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Controlled Hypothermia as an Ancillary Surgical Procedure
Controlled Hypothermia asan Aneiflary Surgical Procedure GERALD H. PRATT, M.D., F.A.C.S.* VINCENT J. COLLINS, M.D., F.A.C.A.**
THE use of cooling as an analgesic probably predated medicine as a science. This is illustrated by the habit of placing an injured part in cold water to relieve pain or inflammation. The analgesic powers of cold are emphasized by the application of cold cloths, the ice bag and the ice collar. It is not surprising, therefore, that the power of cold to relieve pain was extended to its application as an anesthetic agent. In the late 1930's, Fay and Smith! used human refrigeration to allay the pain associated with inoperable carcinoma. This therapy was effective. In addition to its analgesic effect, the cooling reduced the metabolism of the area. It also cut down the inflammatory activity of the secondary infectious organisms. It was not unusual to see necrotic, infected, malignant growths, of the breast for example, locally improve. Sloughing areas often localized and secondary inflammation was retarded. In the 1930's and early 1940's anesthesia difficulties were one of the main causes for death after amputation for gangrene. Allen and Crossman 2 • 3 were instrumental in introducing refrigeration as an anesthesia for this type of surgery. Our own experiences with this type of anesthesia for amputation have been reported. We found this method satisfactory and used it as the only anesthesia in over 100 major amputations until the advent of one-legged spinal anesthesia.' Lange," Lewis, 6 Talbott," Cookson," Bigelow" and McQuiston l O have been instrumental in the development of anesthesia by hypothermia measures. From the Departments of Surgery and Anesthesiology, St. Vincent's Hospital, New York, N. Y.
* Attending Surgeon and Chief of Vascular Surgery, St. Vincent's Hospital; Associate Clinical Professor of Surgery, New York University College of Medicine. ** Director of the Department of Anesthesiology, St. Vincent's Hospital. 405
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Gerald H. Pratt, Vincent J. Collins CONCLUSIONS FROM EXPERIMENTAL WORK
It had been found that the conduction power of normal nerves is decreased by cooling them. This indicated that the pain fibers could be anesthetized by refrigeration alone." Smith," who was associated with Fay in his earlier work, had shown already that the brain withstood hypothermia well. It is to Bigelow" and Boerema," however, that we are indebted for our knowledge that metabolism could be so lowered that essential circulation to certain parts of the body could be interrupted safely for a much longer time than without refrigeration. Swan," Cookson," Varco,'" Bailey'? and others all played a part in this development. Some of the conclusions of this experimental work on hypothermia follow: 1. Oxygen consumption is reduced consistently and nearly proportionately to the degree of lowered temperature (if shivering is prevented). 2. If shivering occurs, oxygen consumption increases. 3. There are lowered blood pressure, reduced pulse and slower respiration as the temperature drops. (At 68° F. cardiac action, pulse and blood pressure are 15 per cent of normal. 13) 4. There is general arterial, arteriolar and venous constriction." 5. The venous pressure in the right auricle and the superior vena cava is reduced until the temperature reaches 80.6° F. Thereafter it will rise." As the temperature drops, the danger of cardiac arrest increases. It has been found that a reduced thermal state permits the blood supply to be shut off to such essential parts of the body as the brain and the spinal cord for longer periods of time than if the temperature were not so reduced. 13, 18 The above findings immediately suggested and ultimately led to the clinical application of hypothermia in cardiac surgery. The exact future place of this modality in surgery is not known. It seems certain that cooling will be used always to combat hyperpyrexia, a frequent operative complication. At the present time the use of this modality will permit the heart to be opened for a time which is definitely limited. The circulation to vital parts can be shut off for a much longer time than if the patient is not in a cooled state. Within the limits of this time, direct surgery on the heart or great vessels can be performed. SUMMARY OF OTHER STUDIES OF THE EFFECT OF HYPOTHERMIA
Heart Action and Oxygen Consum.ption with Hypotherm.ia
There is a decrease in the mechanical work of the heart. Both the coronary blood flow and myocardial oxygen consumption decrease."
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The fact that coronary artery-vein oxygen difference remains the same under hypothermic conditions indicates that while oxygen consumption decreases, the relationship between demand and supply remains unchanged. The oxygen consumption declines progressively and nearly proportionately with the degree of hypothermia, provided shivering is prevented and oxygen saturation is maintained. Oxygen saturation is only 15 per cent of normal at 20° C.20 When shivering occurs the oxygen consumption at once rises. Potassium. Balance, Ventricular Fibrillation and Sympatholytic Drug Effect
If the heart muscle is subject to ventricular fibrillation, it loses potassium. In practical application, therefore, hypothermia reduces the arterial pressure and activates the carotid sinus reflex. This reduces the vagal impulses. Any sympatholytic drug such as Prostigmin or acetylcholine thus would have an antifibrillatory effect. 21 Ventricular Fibrillation in Hypothermia
Ventricular fibrillation is a great danger in refrigeration of a patient. Two conditions tend to stimulate ventricular fibrillations. These two are (1) a sudden fall in CO 2 from an abnormally high level and (2) a shift in the serum potassium concentration. Sudden Fall in CO2 • Hyperventilation to control CO 2 accumulation reduces greatly the incidence of ventricular fibrillation in hypothermia. In the experimental animals it was reduced to 8 per cent." If CO 2 accumulates and then suddenly falls toward normal there is serious danger that ventricular fibrillation will be stimulated. If the pH is high, the ventricular fibrillation incidence is lowered. Clinically, then, the anesthesiologist should consistently hyperventilate the patient. Shift in the Serum Potassium. The serum potassium drops as the temperature falls. By injecting potassium chloride into the cold dog's coronaries defibrillation can be brought about. Below 28° C. cardiac irregularities are increasingly frequent. The therapeutic use of potassium chloride seems apparent. The human heart has been opened successfully at temperatures of 21.5 to 26° C. for from 2 to 8~ minutes, in 13 out of 15 patients by
Swan." The excitability of the myocardium probably is increased by hypothermia, but in hypoxic children it may be reduced. The most important therapeutic point to prevent fibrillation however, is adequate ventilation to insure the removal of CO 2• Hypothermia likewise gives a quieter operative field.10
Gerald H. Pratt, Vincent J. Collins
4-08 Hemorrhage in Hypot.herrrria
Bleeding is always a danger in cardiovascular surgery. In massive hemorrhage the experimental dog dies in three minutes if it is not reinfused. The body compensates for severe blood losses by vasoconstriction, the withdrawal of blood pools, tachycardia and tachypnea. In irreversible shock the viscera has intense venous congestion. In hypothermia (25° C.) exsanguination can be prolonged from 3 to 25 minutes without death." Cyanotic children often lose their cyanosis during hypothermia. 24 Neurological Changes in Hypot.hezmfa
There is anxiety to a temperature of 92° F. At 90° F. the patient becomes stuporous but responds; below 85 to 90° F. coma supervenes." (See Table 1.) Reflexes. At 90° F. the pupils dilate and react to light sluggishly. At 82° F. there is no eye reflex response. The pharyngeal and laryngeal reflexes disappear at' 85° F. 25 Table 1 OBSERVATIONS ON CLINICAL PATIENTS UNDER HYPOTHERMIA AT ST. VINCENT'S HOSPITAL
TEMPERATURE
.
37-35° C. (98-95° F.)
35-32° C. (95-90° F.)
Level of consciousness .... Complete Reflex excitability Shivering ............. ++++ Swallowing ............ ++++ Eyelid blink ........... ++++ Pharyngeal. . . . . . . . . . . . ++++ Skin stimulation ....... ++++ Laryngeal ............. .++++ Respiratory rate, approximate % reduction ...... 10% Systolic pressure, approximate % reduction ...... 20% Diastolic pressure, approximate % reduction ...... 15% 80 Cardiac rate .............
Calm
EKG changes ............ None
Slowing
Muscular tone ........... No change
Slight decrease
Ceases
32-29° C. (90-85° F.)
Stuporous 0
29-26° C. (85-80° F.)
Unconscious 0 0 0 0 0
++ ++ +++ +++ +++
+ 0 + + ++
+
40%
45%
50%
30%
40%
50%
25% 60-80
40% 35% 40-50 50-60 Bradycardia BradycarProlonged QT dia,occlu- interval sive peripheral vascular changes Marked Excellent decrease relaxation in tone
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Effects on the Spinal Cord. In another set of experiments there was no paralysis in dogs even after occlusion of the thoracic aorta for 90 minutes. In a control group of dogs four of ten had paralysis after 60 minutes. Ten other dogs died, however, during and from the hypothermia itself in this experiment.!" Ganglion Blocking Agents and Hypothermia. The use of ganglion blocking agents such as methonium salts and antihistamine permits faster refrigeration." Extension of Tjme by Hypot.hezm.ia before Heart Failure and Distal Darnage after Aortic Occlusion
The two main dangers from clamping the thoracic aorta are rapid dilatation and failure of the left ventricle and ischemia distally with cord or renal damage. Cooling animals to 26 to 30° C. prevents heart failure or distal damage after clamping the thoracic aorta. The incidence of ventricular fibrillation after cross clamping the aorta likewise is reduced." CLINICAL OBSERVATIONS DURING HYPOTHERMIA (See Table 1)
While no one's experience has been sufficiently large for his observations to be infallible, certain tentative conclusions can be drawn from the reports in the literature. To these we wish to add some data observed in our own limited experience in using this modality. Shivering
This reflex phenomenon, so important in nature's control of exposure to cold, becomes a dangerous symptom in the clinical use of hypothermia. It had been known from the German experiences during World War II with fliers immersed in cold sea water (and later experiments) that those who shivered died. It is now proved that shivering increases the oxygen consumption and also exhausts the patient. Efforts to control the shivering by curare and intravenous procaine have proven futile. The so-called "lytic cocktail" or chlorpromazine as an autonomic blocking agent is by itself insufficient to eliminate shivering.Pr " The English writers believe that a general anesthetic induction prior to hypothermia is the surest and safest way to prevent shivering." Our anesthesiology department is in full accord with this belief, and so practices general anesthesia induction before hypothermia. Respiration
While the respiration rate progressively decreases as the hypothermia develops another change has been noted, both by Bartlett" and ourselves (V.J.C.). A pause appears at the height of inspiration and just
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before expiration. This is suggestive of apneustic breathing. It may be considered that cold initially causes paralysis of the pontine or upper medullary inhibitory centers, then acts on the medullary facility centers and finally on the lower medullary respiratory centers. Renal Effects
The observations of most investigators indicate that there is temporary depression of kidney function. Patients who have been refrigerated below 88° F. (31° C.) have suppression of urine formation for 12 to 48 hours. After this period there is a progressive return to a normal daily output. Presumably the hypotension accompanying hypothermia is the important factor in the suppression. Experimental studies of the effect of hypothermia have provided important information." Effective renal blood flow shows a progressive reduction from approximately 25 per cent at 92° F. to 33 per cent at 88° F. and 50 per cent at 84° F. The percentage fall parallels the decrease in cardiac output. It should be noted that between 20 and 25 per cent of the cardiac output is directed through the renal circulation. The glomerular filtration is reduced. The para-aminohippurate acid extraction, however, is well maintained, indicating that there is no great interference with the function of the tubules themselves. Furthermore, the excretion of electrolytes is not greatly changed, showing that the hypothermic kidney is capable of considerable osmotic work. Water excretion is diminished and urine flow is decreased in dogs by at least one half. In general, one may conclude that the renal effects are rather transient and are of a nonspecific pattern (V.J.C.). In this way the technique of refrigeration anesthesia differs very little from the stereotyped renal response to most general anesthetic agents." Hyperseneitfvrty of the Myocardial Cells
It appears that with hypothermia the brain cells become less sensitive to an ischemia than at normal temperatures. The myocardial cells, however, conversely become more sensitive to ischemia and anoxia. The main effect of the hyperventilation is to overcome this hypersensitive reaction of the myocardial cells by supplying oxygen and removing CO 2 •
It is apparent from this review that hypothermia as an anesthesiologic adjunct to surgical therapy has a definite place in certain surgical operations. It is important that the surgeon and anesthesiologist recognize and accept the limitations and risks of this modality. This risk is not only to the patient's functions but to his life as well. At the present time the use of this agent should be restricted to those patients in whom cor-
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rection of their disease or lesion is impossible with the standard procedures. If the lesion is incompatible with life, then any risk is assumable. If the addition of hypothermia to other anesthesia methods makes the overall picture a safer one for the patient, then refrigeration should be used. Arteriovenous fistulas involving such areas as the thorax or brain can be treated better in this way. In children, particularly the cyanotic group, the indications may be broadened. These children appear to do better with hypothermia than adults. An important point is that the amount of anesthesia necessary for operation in this poor risk group can be reduced to a minimum or eliminated entirely with refrigeration. INDICATIONS FOR THE USE OF HYPOTHERMIA
Indications always must be modified by individual conditions. These indications are outlined as follows: 1. Intracardiac procedures
a. Open technique (septal defects) b. Occlusion of great vessels 2. Congenital cardiac conditions a. Lesions associated with cyanosis b. Transplantation of great vessels (selected cases) 3. Surgery associated with great blood loss a. Repair aortic aneurysms b. Intracranial vessel surgery c. Vessel grafts to vital organs (selected) 4. Toxic conditions a. Hyperpyrexia b. Severe liver dysfunction 5. Severe stress a. Extensive trauma b. Burns c. Major surgery in debilitated patients (especially children and infants)
Intracardiac Procedures
Since the normal circulation can be closed off for only 3 minutes under nonthermic conditions without irreparable cerebral, cord, renal or peripheral changes; survival after longer occlusions requires one of two things. Either the circulation must be carried on extracorporeally or some method must extend this time for safe occlusion. Despite great efforts, the mechanical heart has not been perfected. Hypothermia seems the best alternative now available. The occlusion can be maintained for 30 minutes without fatal cerebral damage. Where open operations on the heart are required, as in correction of septal defects, this method has already proven itself clinically. If the great vessels must be occluded, as in open operations for pulmonary stenosis, aneurysms, and so on, hypothermia is the method of choice.
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Congenital Cardiac Conditions
In the cyanotic lesions it has been demonstrated that hypothermia increases the safety of the operation. This hypothermia often need not be profound. Hypothermia in itself often decreases the cyanosis." Selected patients with transplantation of the great vessels may do better surgically under hypothermia. Surgery Associated with Great Blood Loss
Where major blood loss is anticipated, as in aortic aneurysms, hypothermia may be selected. Certain patients who will need vessel grafts to vital organs may also do better under hypothermic conditions. This applies also to operations on intracranial vessels. Toxic Conditions
The patient with hyperpyrexia "rho requires surgery may be brought to more normal thermal conditions before and during such surgery. This may apply also to operations near the thermal center where hyperpyrexia may be expected. In some patients with severe liter dysfunction requiring surgery, hypothermia may be the safest adjunct to the standard anesthesia methods. Severe Stress
According to Laborit, 28, 29 patients with extensive trauma have a better chance of survival under some degree of hypothermia. This applies also to patients with major burns. Where major surgery is necessary on debilitated patients this modality may aid in controlling the anesthetic problem. This is true especially in children." TECHNIQUES FOR INDUCING HYPOTHERMIA
The following outline lists the various methods of inducing hypothermia. I. Surf ace cooling 1. Refrigeration blanket 2. Immersion technique 3. Direct application to great vessels a. Refrigerant solutions in thoracic or abdominal cavity 4. Regional refrigeration a. Extremities b. Heart and other organs II. Extracorporeal circulation Use of heart-lung apparatus III. Artificial hibernation (pharmacologic) 1. Neuroplegia-autonomic blockade: chlorpromazine 2. "Lytic cocktails" : combined antihistamine, analgesic (Demerol) and neuroplegic chlorpromazine (Laborit)
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S'URFACE COOLING METHODS
Refrigeration Blanket (Fig. 125)
Refrigeration can be induced by the use of a hypothermic refrigeration unit. * This mattress apparatus has tubes in it through which is pumped a circulating refrigerant. The standard solution is 30 per cent alcohol in
Fig. 125. Refrigeration blanket for hypothermia (Therm-O-Rite Products Co., Buffalo, New York). Figure shows both the blanket with inlets and outlets as well as the machine for circulating the refrigerant or warming solutions. Pratt, Gerald H.: Cardiovascular Surgery, Lea & Febiger, Philadelphia, 1954.)
water. The more elaborate circulation machine can be modified to a simple electric pump and the refrigerant solution can be ice water and salt. The temperature falls slowly but continually, and can be dropped to 80° F. Induction. Morphine and scopolamine are given as premedication. Pentothal sodium and curare do not control shivering. Shivering begins at 96° F. and ceases at 92° F., but it must be prevented as it causes ex• Therm-O-Rite Products, Buffalo, N. Y.
Gerald H. Pratt, Vincent J. Collins haustion. Although intravenous sodium thiopental has been suggested," in our Clinic general anesthesia is-now preferred. The operation can be done adequately at between 84 and 88° F., although some of the operations have been performed at 80 and 81° F. Rate of Cooling. The rate of cooling varies with the patient's size. In adults two to four hours are required. In children the temperature can be reduced to 74° F. in one hour." In our experience, with long) complicated vascular operations the patient's temperature can be maintained at 88 to 92° F. with safety for three to five hours. In our series of nine adults thus operated on there was one serious complication. This was a partial amnesia lasting a year. Rewarming. Rewarming of the patient begins at the termination of the definitive surgery on the heart 'or blood vessels. The cold solution is changed to a warming one. It continues during the closure of the thorax or abdomen, and return to normal temperature requires several hours. Immersion Technique
Induction. An intravenous Pentothal drip for. induction is followed by cyclopropane and then ether, with respiration maintained by endotracheal tube. In the third stage of anesthesia, and with the defensive reflex mechanisms eliminated, the patient is immersed in a tub of ice water at a temperature of approximately 3° C. The patient's body temperature is observed carefully by means of a deep rectal thermometer or thermocouple. Rate of Cooling. The rapidity of cooling by this method depends entirely upon the size of the patient and his adipose covering. The time required to reach the desired level is somewhere betvveen 12 and 20 minutes. The temperature desired is between 28 and 23° C. (73 to 82° F.), depending upon the operation to be performed. The risk of cardiac arrhythmia follows proportionately the degree of cooling. Conversely, the length of time that the circulation can be halted without cerebral cord or other damage increases with the lower temperature. Length of Cooling. The length of time of the cooling should be correlated with the operative procedure contemplated. For an open operation for pulmonary stenosis where four to five minutes will be required, the temperature need only be reduced to 26 to 28° C. (79 to 82.5° F.). For atrial septal defects, where eight to ten minutes may be required, a 24 to 26° C. (75.5 to 79° F.) temperature is necessary. In more extensive operations a modified temperature of from 27 to 30° C. (80 to 86° F.) may be employed. In patients in a desperate state where the operation decides life or death; a lowered temperature to even 21 or 22° C. (69 to 71.5° F.) may be required. This increases the incidence of arrhythmia and cardiac arrest, but in such instances this added risk must be assumed. It must be remembered that the patient's temperature will
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drop from 1 to 6 degrees; depending upon his size, after he is removed from the immersion tank. Rewarming. In Swann's technique the wounds are sealed with dermatome glue and the drains surrounded with pieces of rubber secured with the same material. The patient is then re-immersed in the tub at 45° C. When the temperature has reached 32 or 34° C. (89 to 93.5° F.), the patient is removed from the tank." Combination of Cooling Apparatus and Immersion. The above methods may be combined. The advantages of the rapid induction accomplished with immersion can be continued with a cooling method by the blankets which permit longer operations.
Fig. 126. Regional refrigeration for anesthesia. Direct application of ice in an icebox to limb prior to amputation. Ice is applied for 2 hours before operation and removed in operating room. Amputation is painless provided the sciatic nerve is anesthetized before its division. (Pratt, Gerald H.: Surgical Management of Vascular..Diseases, Lea & Febiger, Philadelphia, 1949.)
Slow Warming. It is uncertain at this time whether slowwarming after certain types of operation would not be advantageous. The emergence of the hibernated animal is gradual, and apparently he resumes his normal functions best under these circumstances. This evidence would tend to indicate that slow warming, at least in some instances, would' have an important therapeutic value. Direct Cold Applications to Great Vessels
Cold solutions can be applied directly to the major blood vessels and this method quite rapidly results in hypothermia. Ice bags have been applied by some surgeons along the great vessels. In combination with ganglioplegic substances the temperature could be lowered rapidly." At times this cooling can be induced by repeatedly flooding the chest or abdominal cavity with cold saline. 18
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Regional Refrigeration (Fig. 126)
In the original refrigeration anesthesia techniques for amputation, the limb was encased in ice for several hours before the operation. The part was actually and directly cooled. The blanket works as well. The amputation could be done without further anesthesia except for a local infiltration with procaine of the sciatic nerve prior to its division. Over 100 amputations were done by one of us successfully with this technique." Such regional cooling can be applied to other organs, including the heart. EXTRACORPOREAL CIRCULATION METHOD
This method requires the use of an extracorporeal pump. The blood is removed, cooled and replaced. It has been advocated by Brock, but is a complicated technique with which we have had no experience. ARTIFICIAL HIBERNATION METHOD (PHARMACOLOGIC)
This method of hibernation essentially is a technique of blocking heat production by central autonomic blocking agents, which requires concomitant analgesia or anesthesia. There are tW0. types of such blocks described. The neuroplegia autonomic blockage consists of the use of chlorpromazine. The second method consists of a combined antihistamine, an analgesic and a neuroplegic substance. Demerol is used as the analgesic, and the neuroplegic block is again chlorpromazine. It appears that the latter substance is the active principle in this method. Other drugs with similar action will be found.": 29 DISADVA~TAGES
OF HYPOTHERMIA
Stress Reaction to Cold
The stress reaction which is an initial phenomenon is a definite disadvantage. It can be minimized by the use of central autonomic blocking agents (chlorpromazine) and general anesthetic agents. Increased Myocardial Irritability
This increased cardiac irritability is a definite deterrent to the use of hypothermia and is related to temperature levels below 80° F. It can be overcome by careful attention to acid-base and electrolyte balance and to adequate ventilation. Cardiac cells under hypothermia die in 15 minutes if the circulation is shut off in contrast to the 30 minutes that the brain cells can withstand no circulation. Increased Viscosity of Blood and Hernoconoerrtnat.iori
Such blood changes are conducive to intravascular clotting. They can be controlled in part by the continuous infusion of crystalloidal solutions (5 per cent dextrose in water; sixth-molar sodium lactate). Potassium
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lactate solution (Darrow) helps protect the patient against ventricular fibrillation. PRACTICAL APPLICATIONS AND CASE REPORTS CASE I. A white, male patient, aged 61, was admitted because of severe claudication in the left lower extremity, associated with coldness, rest pain, paresthesia and some anesthesia which had been present for two years. A translumbar aortogram showed a complete block of the left internal iliac artery, the left external iliac artery and minimal collaterals to the femoral artery (Fig. 127).
Fig. 127. Preoperative and postoperative aortograms after successful endarterectomy. Operation performed under hypothermia.
Morphine, 1/6 grain, and scopolamine, 1/150 grain, were given one hour before operation. Pentothal Sodium, 0.4 per cent, and curare were used for induction and the patient was intubated and further anesthetized. Hypothermia than was induced, using the refrigeration blankets. At the end of one hour the patient's temperature was 90° F. The blood pressure, which had been 120/70, the pulse 80 and the respirations 20, dropped during induction to 80/50, 58 and 16 respectively. Pentothal Sodium then was discontinued and the patient was given nitrous oxide and oxygen inhalations. The temperature then dropped to 83° F. The operation consisted of exploring the aorta, iliac and femoral arteries. An endarterectomy of the iliac and femoral arteries was performed. Surgical sympathectomy was used as a complement to the intimectomy. The operation lasted three and a half hours. The patient's temperature at its lowest was 79° F. At this temperature, the blood pressure, pulse and respiration remained at the level of 120/60, 60 and 16. The patient received 500 cc, of blood during the
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operation. The postoperative aortogram showed an improved circulation with a larger lumen and a much more satisfactory filling of the collateral vessels. The patient made an uneventful recovery, with no residual disability due to either the operation or anesthesia. Six months later the claudication time had shown a progressive decrease. CASE II. This male patient, 69 years of age, was admitted to the hospital with a tumor mass in the abdomen the size of an 8 months' pregnancy, and intolerable pain. This mass had an expansile pulsation and a systolic bruit. There had been
) Fig. 128. Abdominal aortic aneurysm treated by wiring. Operation performed under hypothermia. Six hundred feet of No. 32 alloy steel wire inserted in enormous arteriosclerotic aneurysm. Tumor encased in wire mesh. Result: Relief of pain for 1 year.
two episodes of sudden collapse within-the last nine months. The diagnosis was abdominal aneurysm of arteriosclerotic origin. The patient had been on heavy doses of morphine and his general status was unsatisfactory. The x-rays showed the renal vessels were both involved in this process. Operation was proposed only because of the severity of the pain. It was evident preoperatively that resection of the aneurysm and grafting would not be feasible. There also had been two coronary occlusions and the patient had a heart block. Refrigeration anesthesia was selected to augment the segmental spinal anesthesia in an effort to eliminate or at least minimize the risk. The patient was given morphine and Sodium Amytal. The temperature was dropped to 90° F. slowly over a period of two hours. At this temperature, 120 mg. of procaine was injected intrathecally. The spinal anesthesia reached the
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level of the seventh thoracic vertebrae. The blood pressure was 140/100, the pulse rate 92, and the respirations 36, dropping to 120/100, 80 and 22, respectively. The operation consisted of inserting over 600 feet of No. 32 steel wire into the aneurysm by the two-needle technique, the wire being forced in from both sides at the same time. At one stage the area of old leakage in the right iliac gutter gave way with a massive hemorrhage. This area -was sealed over by. the use of the psoas muscle sutured to the retroperitoneum. The entire aneurysm was then
Fig. 129. Postoperative x-ray showing 600 feet of wire in huge aneurysm.
encased in a No. 70 steel mesh cloth. The operation required four hours, and 4000 cc. of blood were transfused (Fig. 128). At the conclusion of this stage of the operation, the rewarming process was begun. The patient was slowly rewarmed, his temperature reaching 98° F. in two hours. The patient made an uneventful recovery (Fig. 129). After the second day sedation was not required and the relief of pain was dramatic. This patient subsequently was observed for one year. Another rupture at that
Gerald H. Pratt, Vincent J. Collins time resulted fatally. It is of interest that a postmortem examination showed that neither of the previous leaking points had given way but that a new area near the left iliac artery, at the site of a degenerated plaque, was the source of the final fatal hemorrhage. This patient was given a year more of life with freedom from pain by this operation. We believe that hypothermia made this operation possible in this poor risk patient. CONCLUSIONS
1. Hypothermia is a valuable anesthesia and surgical adjunct in certain diseases. 2. It permits open-heart operations (limited), and reduces the danger from cerebral, cord and peripheral ischemia by extending the time the circulation can be occluded. 3. Until the mechanical heart is perfected this method will permit the best open-heart operation. 4. Its application requires a trained team to minimize the technical difficulties and permit its successful application. 5. The greatest danger is ventricular fibrillation. The incidence can be reduced by careful attention to measures to reduce cardiac irritation. 6. Better methods to treat fibrillation and cardiac massage are being developed as its mechanism is further studied. 7. Within limits outlined the hypothermic technique is an addition to the surgical and anesthesia armamentarium. REFERENCES 1. Fay, Temple and Smith, G. W.: Observations of Reflex Responses During Prolonged Periods of Human Refrigeration. Arch. Neurol. & Psychiat. 4-5: 215; 1941. 2. Allen, F. M.: Reduced Temperatures in Surgery. Am. J. Surge 52: 225, 1941. 3. Allen, F. M., Crossman, L. W. and Safford, F. K. Jr.: Reduced Temperature Treatment for Burns and Frostbite. New York State J. Med. 43: 951, 1943. 4. Pratt, Gerald H.: Surgical Management of Vascular Diseases. Philadelphia, Lea & Febiger, 1949. 5. Lange, K., Weiner, D. and Boyd, L. J.: Frostbite, Physiology, Pathology and Therapy. New England J. Med. 237: 383, 1947. 6. Lewis, Col. R. B.: Local Cold Injury-Frostbite. The Wellcome Prize Essay, 1951. 7. Talbott, J. J.: The Physiologic and Therapeutic Effects of Hypothermia. New England J. Med. 224: 281, 1941. 8. Cookson, Brian A., Neptune, Wilford B. and Bailey, Charles P.: Hypothermia as a Means of Performing Intracardiac Surgery under Direct Vision. Diseases of the Chest 22: 245, 1952. 9. Bigelow, W. G., Lindsay, W. R. and Greenwood, W. F.: Hypothermia. Its Possible Role in Cardiac Surgery: An Investigation of Factors Governing Survival in Dogs at Low Body Temperature. Ann. Surge 132: 849, 1950. 10. McQuiston, W. 0.: Anesthesia for Cardiac Surgery in Children. Pede Clin, North America 1: 147, 1954. 11. Bickford, R. G.: The Fibre Dissociation Produced by Cooling Human Nerves. Clin. Sc. 4: 159, 1939. 12. Smith, L. W.: The Use of Cold in Medicine. Ann. Int. Med. 17: 618, 1942.
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13. Bigelow, W. G. and McBirnie, J. E.: Further Experiences with Hypothermia for Intracardiac Surgery with Monkeys and Groundhogs. Ann. Surge 137: 361, 1953. ,14. Boerema, I., Wildschut, A., Schmidt, W. J. H. and Broekhuysen, L.: Experimental Researches into Hypothermia as an Aid in Surgery of the Heart. Arch. chir. need. 3: 25, 1951. 15. Swan, Henry and Zeavin, Irvin: Cessation of Circulation in General Hypothermia. III. Technics of Intracardiac Surgery under Direct Vision. Ann. Surge 139:385,1954. 16. Varco, R. L.: Discussion of paper by Muller and Longmire. Surgery 30: 42,1951. 17. Bailey, C. P., et al.: Congenital Interatrial Communications: Clinical and Surgical Considerations with a Description of aNew Surgical Technic: Atrioseptopexy. Ann. Int. Med. 37: 888, 1952. 18. Beattie, E. J. Jr., Adovasio, D., Keshishian, J. H. and Blades, Brian: Refrigeration in Experimental Surgery of the Aorta. Surg., Gynec. & Obst. 96: 6, 1953. . 19. Edwards, W. S., Tuhey, S., Reber, W. E., Siegel, A. and Bing, R. J.: Coronary Blood Flow and Myocardial Metabolism in Hypothermia. Ann. Surge 139: 275, 1954. 20. Bigelow, A. A., Mustard, W. T. and Evans, J. G.: Some Physiologic Concepts of Hypothermia and Their Application to Cardiac Surgery. J. Thoracic Surge 28: 463, 1954. 21. Montgomery, A. V., Prevedal, A. E. and Swan, Henry: Prostigmine Inhibition of Ventricular Fibrillation in the Hypothermic Dog. Circulation 10: 721, 1954. 22. Swan, Henry, Zeavin, Irvin, Blount, S. Gilbert Jr. and Virtue, R. W.: Surgery by Direct Vision in the Open Heart During Hypothermia. J.A.M.A. 153: 1081, 1953. 23. Bobbio, A., Foffrini, P. and Bezzi, E.: Massive Hemorrhage Combined with Controlled General Hypothermia and Its Application to Experimental Cardiac Surgery. Bol. Soc. Piemont Chir. 24-: 428, 1954. 24. Scott, H. W. Jr., Collins, H. A. and Foster, J. A.: Hypothermia as an Adjuvant in Cardiovascular Surgery; Experimental and Clinical Observations. Ann. Surgeon 20: 799, 1954. 25. Collins, V. J. and Grantelli, A.: Controlled Hypothermia During Anesthesia in Human Adults. Use in Cardiovascular Surgery. Preliminary Observations. Angiology 6: 118, 1955. 26. Hardin, C. A., Reismann, K. R. and Dimond, E. G.: The Use of Hypothermia in the Resection and Homologous Graft Replacement of the Thoracic Grafts. Ann. Surge 14-0: 720, 1954. 27. Dogliotti, A. M. and Ciocatto, E.: Physiopathological Basis of Hypothermia and Possibilities of Combination of Hypothermia and Extracorpeal Circulation. Schweiz. med. Wchnschr. 83: 707, 1953. 28. Laborit, H. et Huguenard, P.: Technique actuelle de l'hibernation artificielle. Presse med. 60: 1455, 1952. 29. Laborit, H. et Huguenard, P.: Pratique de I'hibernotherapie en chirurgie et en medicine. Masson & Cie., 1954. 30. Symposium, Faculty Anesthetists Royal College of Surgeons: Present Status of Hypothermia in Anesthesia. Brit. M. J. 4919: 968, 1955. 31. Bartlett, R. G.: Apneustic Breathing Produced by Severe Hypothermia with Mild Anesthesia. Am. J. Physiol. 180: 433, 1955. 32. Miles, B. E. and Churchill-Davidson, H. C.: The Effect of Hypothermia on the Renal Circulation of the Dog. Anesthesiology 16: 230, 1955. 33. Papper, E. M.: Renal Function During General Anesthesia and Operation. ,T.A.M.A. 152: 1686, 1953. 34. Keown, Kenneth K.: Hypothermia. Chapter IV in Bailey, C. P.: Surgery of the Heart. Philadelphia, Lea & Febiger, 1955.
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35. Dogliotti, A. M. and Avicatto, E.: Surgical Possibihties on Bloodless Heart in Animals Treated with Ganglioplegic Substances and Hypothermia. Minerva med. 43: 891, 1952. 36. Pratt, Gerald H.: Amputation f-or Vascular Disease with Refrigeration Anesthesia. Postgraduate Med. 6: 490, 1949. 20 East 68th Street New York, N. Y. (Dr. Pratt)
THE use of cooling as an analgesic probably predated medicine as a science. This is illustrated by the habit of placing an injured part in cold water to relieve pain or inflammation. The analgesic powers of cold are emphasized by the application of cold cloths, the ice bag and the ice collar. It is not surprising, therefore, that the power of cold to relieve pain was extended to its application as an anesthetic agent. In the late 1930's, Fay and Smith! used human refrigeration to allay the pain associated with inoperable carcinoma. This therapy was effective. In addition to its analgesic effect, the cooling reduced the metabolism of the area. It also cut down the inflammatory activity of the secondary infectious organisms. It was not unusual to see necrotic, infected, malignant growths, of the breast for example, locally improve. Sloughing areas often localized and secondary inflammation was retarded. In the 1930's and early 1940's anesthesia difficulties were one of the main causes for death after amputation for gangrene. Allen and Crossman 2 • 3 were instrumental in introducing refrigeration as an anesthesia for this type of surgery. Our own experiences with this type of anesthesia for amputation have been reported. We found this method satisfactory and used it as the only anesthesia in over 100 major amputations until the advent of one-legged spinal anesthesia.' Lange," Lewis, 6 Talbott," Cookson," Bigelow" and McQuiston l O have been instrumental in the development of anesthesia by hypothermia measures. From the Departments of Surgery and Anesthesiology, St. Vincent's Hospital, New York, N. Y.
* Attending Surgeon and Chief of Vascular Surgery, St. Vincent's Hospital; Associate Clinical Professor of Surgery, New York University College of Medicine. ** Director of the Department of Anesthesiology, St. Vincent's Hospital. 405
406
Gerald H. Pratt, Vincent J. Collins CONCLUSIONS FROM EXPERIMENTAL WORK
It had been found that the conduction power of normal nerves is decreased by cooling them. This indicated that the pain fibers could be anesthetized by refrigeration alone." Smith," who was associated with Fay in his earlier work, had shown already that the brain withstood hypothermia well. It is to Bigelow" and Boerema," however, that we are indebted for our knowledge that metabolism could be so lowered that essential circulation to certain parts of the body could be interrupted safely for a much longer time than without refrigeration. Swan," Cookson," Varco,'" Bailey'? and others all played a part in this development. Some of the conclusions of this experimental work on hypothermia follow: 1. Oxygen consumption is reduced consistently and nearly proportionately to the degree of lowered temperature (if shivering is prevented). 2. If shivering occurs, oxygen consumption increases. 3. There are lowered blood pressure, reduced pulse and slower respiration as the temperature drops. (At 68° F. cardiac action, pulse and blood pressure are 15 per cent of normal. 13) 4. There is general arterial, arteriolar and venous constriction." 5. The venous pressure in the right auricle and the superior vena cava is reduced until the temperature reaches 80.6° F. Thereafter it will rise." As the temperature drops, the danger of cardiac arrest increases. It has been found that a reduced thermal state permits the blood supply to be shut off to such essential parts of the body as the brain and the spinal cord for longer periods of time than if the temperature were not so reduced. 13, 18 The above findings immediately suggested and ultimately led to the clinical application of hypothermia in cardiac surgery. The exact future place of this modality in surgery is not known. It seems certain that cooling will be used always to combat hyperpyrexia, a frequent operative complication. At the present time the use of this modality will permit the heart to be opened for a time which is definitely limited. The circulation to vital parts can be shut off for a much longer time than if the patient is not in a cooled state. Within the limits of this time, direct surgery on the heart or great vessels can be performed. SUMMARY OF OTHER STUDIES OF THE EFFECT OF HYPOTHERMIA
Heart Action and Oxygen Consum.ption with Hypotherm.ia
There is a decrease in the mechanical work of the heart. Both the coronary blood flow and myocardial oxygen consumption decrease."
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The fact that coronary artery-vein oxygen difference remains the same under hypothermic conditions indicates that while oxygen consumption decreases, the relationship between demand and supply remains unchanged. The oxygen consumption declines progressively and nearly proportionately with the degree of hypothermia, provided shivering is prevented and oxygen saturation is maintained. Oxygen saturation is only 15 per cent of normal at 20° C.20 When shivering occurs the oxygen consumption at once rises. Potassium. Balance, Ventricular Fibrillation and Sympatholytic Drug Effect
If the heart muscle is subject to ventricular fibrillation, it loses potassium. In practical application, therefore, hypothermia reduces the arterial pressure and activates the carotid sinus reflex. This reduces the vagal impulses. Any sympatholytic drug such as Prostigmin or acetylcholine thus would have an antifibrillatory effect. 21 Ventricular Fibrillation in Hypothermia
Ventricular fibrillation is a great danger in refrigeration of a patient. Two conditions tend to stimulate ventricular fibrillations. These two are (1) a sudden fall in CO 2 from an abnormally high level and (2) a shift in the serum potassium concentration. Sudden Fall in CO2 • Hyperventilation to control CO 2 accumulation reduces greatly the incidence of ventricular fibrillation in hypothermia. In the experimental animals it was reduced to 8 per cent." If CO 2 accumulates and then suddenly falls toward normal there is serious danger that ventricular fibrillation will be stimulated. If the pH is high, the ventricular fibrillation incidence is lowered. Clinically, then, the anesthesiologist should consistently hyperventilate the patient. Shift in the Serum Potassium. The serum potassium drops as the temperature falls. By injecting potassium chloride into the cold dog's coronaries defibrillation can be brought about. Below 28° C. cardiac irregularities are increasingly frequent. The therapeutic use of potassium chloride seems apparent. The human heart has been opened successfully at temperatures of 21.5 to 26° C. for from 2 to 8~ minutes, in 13 out of 15 patients by
Swan." The excitability of the myocardium probably is increased by hypothermia, but in hypoxic children it may be reduced. The most important therapeutic point to prevent fibrillation however, is adequate ventilation to insure the removal of CO 2• Hypothermia likewise gives a quieter operative field.10
Gerald H. Pratt, Vincent J. Collins
4-08 Hemorrhage in Hypot.herrrria
Bleeding is always a danger in cardiovascular surgery. In massive hemorrhage the experimental dog dies in three minutes if it is not reinfused. The body compensates for severe blood losses by vasoconstriction, the withdrawal of blood pools, tachycardia and tachypnea. In irreversible shock the viscera has intense venous congestion. In hypothermia (25° C.) exsanguination can be prolonged from 3 to 25 minutes without death." Cyanotic children often lose their cyanosis during hypothermia. 24 Neurological Changes in Hypot.hezmfa
There is anxiety to a temperature of 92° F. At 90° F. the patient becomes stuporous but responds; below 85 to 90° F. coma supervenes." (See Table 1.) Reflexes. At 90° F. the pupils dilate and react to light sluggishly. At 82° F. there is no eye reflex response. The pharyngeal and laryngeal reflexes disappear at' 85° F. 25 Table 1 OBSERVATIONS ON CLINICAL PATIENTS UNDER HYPOTHERMIA AT ST. VINCENT'S HOSPITAL
TEMPERATURE
.
37-35° C. (98-95° F.)
35-32° C. (95-90° F.)
Level of consciousness .... Complete Reflex excitability Shivering ............. ++++ Swallowing ............ ++++ Eyelid blink ........... ++++ Pharyngeal. . . . . . . . . . . . ++++ Skin stimulation ....... ++++ Laryngeal ............. .++++ Respiratory rate, approximate % reduction ...... 10% Systolic pressure, approximate % reduction ...... 20% Diastolic pressure, approximate % reduction ...... 15% 80 Cardiac rate .............
Calm
EKG changes ............ None
Slowing
Muscular tone ........... No change
Slight decrease
Ceases
32-29° C. (90-85° F.)
Stuporous 0
29-26° C. (85-80° F.)
Unconscious 0 0 0 0 0
++ ++ +++ +++ +++
+ 0 + + ++
+
40%
45%
50%
30%
40%
50%
25% 60-80
40% 35% 40-50 50-60 Bradycardia BradycarProlonged QT dia,occlu- interval sive peripheral vascular changes Marked Excellent decrease relaxation in tone
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Effects on the Spinal Cord. In another set of experiments there was no paralysis in dogs even after occlusion of the thoracic aorta for 90 minutes. In a control group of dogs four of ten had paralysis after 60 minutes. Ten other dogs died, however, during and from the hypothermia itself in this experiment.!" Ganglion Blocking Agents and Hypothermia. The use of ganglion blocking agents such as methonium salts and antihistamine permits faster refrigeration." Extension of Tjme by Hypot.hezm.ia before Heart Failure and Distal Darnage after Aortic Occlusion
The two main dangers from clamping the thoracic aorta are rapid dilatation and failure of the left ventricle and ischemia distally with cord or renal damage. Cooling animals to 26 to 30° C. prevents heart failure or distal damage after clamping the thoracic aorta. The incidence of ventricular fibrillation after cross clamping the aorta likewise is reduced." CLINICAL OBSERVATIONS DURING HYPOTHERMIA (See Table 1)
While no one's experience has been sufficiently large for his observations to be infallible, certain tentative conclusions can be drawn from the reports in the literature. To these we wish to add some data observed in our own limited experience in using this modality. Shivering
This reflex phenomenon, so important in nature's control of exposure to cold, becomes a dangerous symptom in the clinical use of hypothermia. It had been known from the German experiences during World War II with fliers immersed in cold sea water (and later experiments) that those who shivered died. It is now proved that shivering increases the oxygen consumption and also exhausts the patient. Efforts to control the shivering by curare and intravenous procaine have proven futile. The so-called "lytic cocktail" or chlorpromazine as an autonomic blocking agent is by itself insufficient to eliminate shivering.Pr " The English writers believe that a general anesthetic induction prior to hypothermia is the surest and safest way to prevent shivering." Our anesthesiology department is in full accord with this belief, and so practices general anesthesia induction before hypothermia. Respiration
While the respiration rate progressively decreases as the hypothermia develops another change has been noted, both by Bartlett" and ourselves (V.J.C.). A pause appears at the height of inspiration and just
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Gerald H. Pratt, Vincent J. Collins
before expiration. This is suggestive of apneustic breathing. It may be considered that cold initially causes paralysis of the pontine or upper medullary inhibitory centers, then acts on the medullary facility centers and finally on the lower medullary respiratory centers. Renal Effects
The observations of most investigators indicate that there is temporary depression of kidney function. Patients who have been refrigerated below 88° F. (31° C.) have suppression of urine formation for 12 to 48 hours. After this period there is a progressive return to a normal daily output. Presumably the hypotension accompanying hypothermia is the important factor in the suppression. Experimental studies of the effect of hypothermia have provided important information." Effective renal blood flow shows a progressive reduction from approximately 25 per cent at 92° F. to 33 per cent at 88° F. and 50 per cent at 84° F. The percentage fall parallels the decrease in cardiac output. It should be noted that between 20 and 25 per cent of the cardiac output is directed through the renal circulation. The glomerular filtration is reduced. The para-aminohippurate acid extraction, however, is well maintained, indicating that there is no great interference with the function of the tubules themselves. Furthermore, the excretion of electrolytes is not greatly changed, showing that the hypothermic kidney is capable of considerable osmotic work. Water excretion is diminished and urine flow is decreased in dogs by at least one half. In general, one may conclude that the renal effects are rather transient and are of a nonspecific pattern (V.J.C.). In this way the technique of refrigeration anesthesia differs very little from the stereotyped renal response to most general anesthetic agents." Hyperseneitfvrty of the Myocardial Cells
It appears that with hypothermia the brain cells become less sensitive to an ischemia than at normal temperatures. The myocardial cells, however, conversely become more sensitive to ischemia and anoxia. The main effect of the hyperventilation is to overcome this hypersensitive reaction of the myocardial cells by supplying oxygen and removing CO 2 •
It is apparent from this review that hypothermia as an anesthesiologic adjunct to surgical therapy has a definite place in certain surgical operations. It is important that the surgeon and anesthesiologist recognize and accept the limitations and risks of this modality. This risk is not only to the patient's functions but to his life as well. At the present time the use of this agent should be restricted to those patients in whom cor-
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rection of their disease or lesion is impossible with the standard procedures. If the lesion is incompatible with life, then any risk is assumable. If the addition of hypothermia to other anesthesia methods makes the overall picture a safer one for the patient, then refrigeration should be used. Arteriovenous fistulas involving such areas as the thorax or brain can be treated better in this way. In children, particularly the cyanotic group, the indications may be broadened. These children appear to do better with hypothermia than adults. An important point is that the amount of anesthesia necessary for operation in this poor risk group can be reduced to a minimum or eliminated entirely with refrigeration. INDICATIONS FOR THE USE OF HYPOTHERMIA
Indications always must be modified by individual conditions. These indications are outlined as follows: 1. Intracardiac procedures
a. Open technique (septal defects) b. Occlusion of great vessels 2. Congenital cardiac conditions a. Lesions associated with cyanosis b. Transplantation of great vessels (selected cases) 3. Surgery associated with great blood loss a. Repair aortic aneurysms b. Intracranial vessel surgery c. Vessel grafts to vital organs (selected) 4. Toxic conditions a. Hyperpyrexia b. Severe liver dysfunction 5. Severe stress a. Extensive trauma b. Burns c. Major surgery in debilitated patients (especially children and infants)
Intracardiac Procedures
Since the normal circulation can be closed off for only 3 minutes under nonthermic conditions without irreparable cerebral, cord, renal or peripheral changes; survival after longer occlusions requires one of two things. Either the circulation must be carried on extracorporeally or some method must extend this time for safe occlusion. Despite great efforts, the mechanical heart has not been perfected. Hypothermia seems the best alternative now available. The occlusion can be maintained for 30 minutes without fatal cerebral damage. Where open operations on the heart are required, as in correction of septal defects, this method has already proven itself clinically. If the great vessels must be occluded, as in open operations for pulmonary stenosis, aneurysms, and so on, hypothermia is the method of choice.
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Congenital Cardiac Conditions
In the cyanotic lesions it has been demonstrated that hypothermia increases the safety of the operation. This hypothermia often need not be profound. Hypothermia in itself often decreases the cyanosis." Selected patients with transplantation of the great vessels may do better surgically under hypothermia. Surgery Associated with Great Blood Loss
Where major blood loss is anticipated, as in aortic aneurysms, hypothermia may be selected. Certain patients who will need vessel grafts to vital organs may also do better under hypothermic conditions. This applies also to operations on intracranial vessels. Toxic Conditions
The patient with hyperpyrexia "rho requires surgery may be brought to more normal thermal conditions before and during such surgery. This may apply also to operations near the thermal center where hyperpyrexia may be expected. In some patients with severe liter dysfunction requiring surgery, hypothermia may be the safest adjunct to the standard anesthesia methods. Severe Stress
According to Laborit, 28, 29 patients with extensive trauma have a better chance of survival under some degree of hypothermia. This applies also to patients with major burns. Where major surgery is necessary on debilitated patients this modality may aid in controlling the anesthetic problem. This is true especially in children." TECHNIQUES FOR INDUCING HYPOTHERMIA
The following outline lists the various methods of inducing hypothermia. I. Surf ace cooling 1. Refrigeration blanket 2. Immersion technique 3. Direct application to great vessels a. Refrigerant solutions in thoracic or abdominal cavity 4. Regional refrigeration a. Extremities b. Heart and other organs II. Extracorporeal circulation Use of heart-lung apparatus III. Artificial hibernation (pharmacologic) 1. Neuroplegia-autonomic blockade: chlorpromazine 2. "Lytic cocktails" : combined antihistamine, analgesic (Demerol) and neuroplegic chlorpromazine (Laborit)
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S'URFACE COOLING METHODS
Refrigeration Blanket (Fig. 125)
Refrigeration can be induced by the use of a hypothermic refrigeration unit. * This mattress apparatus has tubes in it through which is pumped a circulating refrigerant. The standard solution is 30 per cent alcohol in
Fig. 125. Refrigeration blanket for hypothermia (Therm-O-Rite Products Co., Buffalo, New York). Figure shows both the blanket with inlets and outlets as well as the machine for circulating the refrigerant or warming solutions. Pratt, Gerald H.: Cardiovascular Surgery, Lea & Febiger, Philadelphia, 1954.)
water. The more elaborate circulation machine can be modified to a simple electric pump and the refrigerant solution can be ice water and salt. The temperature falls slowly but continually, and can be dropped to 80° F. Induction. Morphine and scopolamine are given as premedication. Pentothal sodium and curare do not control shivering. Shivering begins at 96° F. and ceases at 92° F., but it must be prevented as it causes ex• Therm-O-Rite Products, Buffalo, N. Y.
Gerald H. Pratt, Vincent J. Collins haustion. Although intravenous sodium thiopental has been suggested," in our Clinic general anesthesia is-now preferred. The operation can be done adequately at between 84 and 88° F., although some of the operations have been performed at 80 and 81° F. Rate of Cooling. The rate of cooling varies with the patient's size. In adults two to four hours are required. In children the temperature can be reduced to 74° F. in one hour." In our experience, with long) complicated vascular operations the patient's temperature can be maintained at 88 to 92° F. with safety for three to five hours. In our series of nine adults thus operated on there was one serious complication. This was a partial amnesia lasting a year. Rewarming. Rewarming of the patient begins at the termination of the definitive surgery on the heart 'or blood vessels. The cold solution is changed to a warming one. It continues during the closure of the thorax or abdomen, and return to normal temperature requires several hours. Immersion Technique
Induction. An intravenous Pentothal drip for. induction is followed by cyclopropane and then ether, with respiration maintained by endotracheal tube. In the third stage of anesthesia, and with the defensive reflex mechanisms eliminated, the patient is immersed in a tub of ice water at a temperature of approximately 3° C. The patient's body temperature is observed carefully by means of a deep rectal thermometer or thermocouple. Rate of Cooling. The rapidity of cooling by this method depends entirely upon the size of the patient and his adipose covering. The time required to reach the desired level is somewhere betvveen 12 and 20 minutes. The temperature desired is between 28 and 23° C. (73 to 82° F.), depending upon the operation to be performed. The risk of cardiac arrhythmia follows proportionately the degree of cooling. Conversely, the length of time that the circulation can be halted without cerebral cord or other damage increases with the lower temperature. Length of Cooling. The length of time of the cooling should be correlated with the operative procedure contemplated. For an open operation for pulmonary stenosis where four to five minutes will be required, the temperature need only be reduced to 26 to 28° C. (79 to 82.5° F.). For atrial septal defects, where eight to ten minutes may be required, a 24 to 26° C. (75.5 to 79° F.) temperature is necessary. In more extensive operations a modified temperature of from 27 to 30° C. (80 to 86° F.) may be employed. In patients in a desperate state where the operation decides life or death; a lowered temperature to even 21 or 22° C. (69 to 71.5° F.) may be required. This increases the incidence of arrhythmia and cardiac arrest, but in such instances this added risk must be assumed. It must be remembered that the patient's temperature will
Controlled Hypothermia as an A ncillary Surgical Procedure
415
drop from 1 to 6 degrees; depending upon his size, after he is removed from the immersion tank. Rewarming. In Swann's technique the wounds are sealed with dermatome glue and the drains surrounded with pieces of rubber secured with the same material. The patient is then re-immersed in the tub at 45° C. When the temperature has reached 32 or 34° C. (89 to 93.5° F.), the patient is removed from the tank." Combination of Cooling Apparatus and Immersion. The above methods may be combined. The advantages of the rapid induction accomplished with immersion can be continued with a cooling method by the blankets which permit longer operations.
Fig. 126. Regional refrigeration for anesthesia. Direct application of ice in an icebox to limb prior to amputation. Ice is applied for 2 hours before operation and removed in operating room. Amputation is painless provided the sciatic nerve is anesthetized before its division. (Pratt, Gerald H.: Surgical Management of Vascular..Diseases, Lea & Febiger, Philadelphia, 1949.)
Slow Warming. It is uncertain at this time whether slowwarming after certain types of operation would not be advantageous. The emergence of the hibernated animal is gradual, and apparently he resumes his normal functions best under these circumstances. This evidence would tend to indicate that slow warming, at least in some instances, would' have an important therapeutic value. Direct Cold Applications to Great Vessels
Cold solutions can be applied directly to the major blood vessels and this method quite rapidly results in hypothermia. Ice bags have been applied by some surgeons along the great vessels. In combination with ganglioplegic substances the temperature could be lowered rapidly." At times this cooling can be induced by repeatedly flooding the chest or abdominal cavity with cold saline. 18
Gerald H. Pratt, Vincent J. Collins
416
Regional Refrigeration (Fig. 126)
In the original refrigeration anesthesia techniques for amputation, the limb was encased in ice for several hours before the operation. The part was actually and directly cooled. The blanket works as well. The amputation could be done without further anesthesia except for a local infiltration with procaine of the sciatic nerve prior to its division. Over 100 amputations were done by one of us successfully with this technique." Such regional cooling can be applied to other organs, including the heart. EXTRACORPOREAL CIRCULATION METHOD
This method requires the use of an extracorporeal pump. The blood is removed, cooled and replaced. It has been advocated by Brock, but is a complicated technique with which we have had no experience. ARTIFICIAL HIBERNATION METHOD (PHARMACOLOGIC)
This method of hibernation essentially is a technique of blocking heat production by central autonomic blocking agents, which requires concomitant analgesia or anesthesia. There are tW0. types of such blocks described. The neuroplegia autonomic blockage consists of the use of chlorpromazine. The second method consists of a combined antihistamine, an analgesic and a neuroplegic substance. Demerol is used as the analgesic, and the neuroplegic block is again chlorpromazine. It appears that the latter substance is the active principle in this method. Other drugs with similar action will be found.": 29 DISADVA~TAGES
OF HYPOTHERMIA
Stress Reaction to Cold
The stress reaction which is an initial phenomenon is a definite disadvantage. It can be minimized by the use of central autonomic blocking agents (chlorpromazine) and general anesthetic agents. Increased Myocardial Irritability
This increased cardiac irritability is a definite deterrent to the use of hypothermia and is related to temperature levels below 80° F. It can be overcome by careful attention to acid-base and electrolyte balance and to adequate ventilation. Cardiac cells under hypothermia die in 15 minutes if the circulation is shut off in contrast to the 30 minutes that the brain cells can withstand no circulation. Increased Viscosity of Blood and Hernoconoerrtnat.iori
Such blood changes are conducive to intravascular clotting. They can be controlled in part by the continuous infusion of crystalloidal solutions (5 per cent dextrose in water; sixth-molar sodium lactate). Potassium
Controlled Hypothermia as an Ancillary Surgical Procedure
417
lactate solution (Darrow) helps protect the patient against ventricular fibrillation. PRACTICAL APPLICATIONS AND CASE REPORTS CASE I. A white, male patient, aged 61, was admitted because of severe claudication in the left lower extremity, associated with coldness, rest pain, paresthesia and some anesthesia which had been present for two years. A translumbar aortogram showed a complete block of the left internal iliac artery, the left external iliac artery and minimal collaterals to the femoral artery (Fig. 127).
Fig. 127. Preoperative and postoperative aortograms after successful endarterectomy. Operation performed under hypothermia.
Morphine, 1/6 grain, and scopolamine, 1/150 grain, were given one hour before operation. Pentothal Sodium, 0.4 per cent, and curare were used for induction and the patient was intubated and further anesthetized. Hypothermia than was induced, using the refrigeration blankets. At the end of one hour the patient's temperature was 90° F. The blood pressure, which had been 120/70, the pulse 80 and the respirations 20, dropped during induction to 80/50, 58 and 16 respectively. Pentothal Sodium then was discontinued and the patient was given nitrous oxide and oxygen inhalations. The temperature then dropped to 83° F. The operation consisted of exploring the aorta, iliac and femoral arteries. An endarterectomy of the iliac and femoral arteries was performed. Surgical sympathectomy was used as a complement to the intimectomy. The operation lasted three and a half hours. The patient's temperature at its lowest was 79° F. At this temperature, the blood pressure, pulse and respiration remained at the level of 120/60, 60 and 16. The patient received 500 cc, of blood during the
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Gerald H. Pratt, Vincent J. Collins
operation. The postoperative aortogram showed an improved circulation with a larger lumen and a much more satisfactory filling of the collateral vessels. The patient made an uneventful recovery, with no residual disability due to either the operation or anesthesia. Six months later the claudication time had shown a progressive decrease. CASE II. This male patient, 69 years of age, was admitted to the hospital with a tumor mass in the abdomen the size of an 8 months' pregnancy, and intolerable pain. This mass had an expansile pulsation and a systolic bruit. There had been
) Fig. 128. Abdominal aortic aneurysm treated by wiring. Operation performed under hypothermia. Six hundred feet of No. 32 alloy steel wire inserted in enormous arteriosclerotic aneurysm. Tumor encased in wire mesh. Result: Relief of pain for 1 year.
two episodes of sudden collapse within-the last nine months. The diagnosis was abdominal aneurysm of arteriosclerotic origin. The patient had been on heavy doses of morphine and his general status was unsatisfactory. The x-rays showed the renal vessels were both involved in this process. Operation was proposed only because of the severity of the pain. It was evident preoperatively that resection of the aneurysm and grafting would not be feasible. There also had been two coronary occlusions and the patient had a heart block. Refrigeration anesthesia was selected to augment the segmental spinal anesthesia in an effort to eliminate or at least minimize the risk. The patient was given morphine and Sodium Amytal. The temperature was dropped to 90° F. slowly over a period of two hours. At this temperature, 120 mg. of procaine was injected intrathecally. The spinal anesthesia reached the
Controlled Hypothermia as an Ancillary Surgical Procedure
419
level of the seventh thoracic vertebrae. The blood pressure was 140/100, the pulse rate 92, and the respirations 36, dropping to 120/100, 80 and 22, respectively. The operation consisted of inserting over 600 feet of No. 32 steel wire into the aneurysm by the two-needle technique, the wire being forced in from both sides at the same time. At one stage the area of old leakage in the right iliac gutter gave way with a massive hemorrhage. This area -was sealed over by. the use of the psoas muscle sutured to the retroperitoneum. The entire aneurysm was then
Fig. 129. Postoperative x-ray showing 600 feet of wire in huge aneurysm.
encased in a No. 70 steel mesh cloth. The operation required four hours, and 4000 cc. of blood were transfused (Fig. 128). At the conclusion of this stage of the operation, the rewarming process was begun. The patient was slowly rewarmed, his temperature reaching 98° F. in two hours. The patient made an uneventful recovery (Fig. 129). After the second day sedation was not required and the relief of pain was dramatic. This patient subsequently was observed for one year. Another rupture at that
Gerald H. Pratt, Vincent J. Collins time resulted fatally. It is of interest that a postmortem examination showed that neither of the previous leaking points had given way but that a new area near the left iliac artery, at the site of a degenerated plaque, was the source of the final fatal hemorrhage. This patient was given a year more of life with freedom from pain by this operation. We believe that hypothermia made this operation possible in this poor risk patient. CONCLUSIONS
1. Hypothermia is a valuable anesthesia and surgical adjunct in certain diseases. 2. It permits open-heart operations (limited), and reduces the danger from cerebral, cord and peripheral ischemia by extending the time the circulation can be occluded. 3. Until the mechanical heart is perfected this method will permit the best open-heart operation. 4. Its application requires a trained team to minimize the technical difficulties and permit its successful application. 5. The greatest danger is ventricular fibrillation. The incidence can be reduced by careful attention to measures to reduce cardiac irritation. 6. Better methods to treat fibrillation and cardiac massage are being developed as its mechanism is further studied. 7. Within limits outlined the hypothermic technique is an addition to the surgical and anesthesia armamentarium. REFERENCES 1. Fay, Temple and Smith, G. W.: Observations of Reflex Responses During Prolonged Periods of Human Refrigeration. Arch. Neurol. & Psychiat. 4-5: 215; 1941. 2. Allen, F. M.: Reduced Temperatures in Surgery. Am. J. Surge 52: 225, 1941. 3. Allen, F. M., Crossman, L. W. and Safford, F. K. Jr.: Reduced Temperature Treatment for Burns and Frostbite. New York State J. Med. 43: 951, 1943. 4. Pratt, Gerald H.: Surgical Management of Vascular Diseases. Philadelphia, Lea & Febiger, 1949. 5. Lange, K., Weiner, D. and Boyd, L. J.: Frostbite, Physiology, Pathology and Therapy. New England J. Med. 237: 383, 1947. 6. Lewis, Col. R. B.: Local Cold Injury-Frostbite. The Wellcome Prize Essay, 1951. 7. Talbott, J. J.: The Physiologic and Therapeutic Effects of Hypothermia. New England J. Med. 224: 281, 1941. 8. Cookson, Brian A., Neptune, Wilford B. and Bailey, Charles P.: Hypothermia as a Means of Performing Intracardiac Surgery under Direct Vision. Diseases of the Chest 22: 245, 1952. 9. Bigelow, W. G., Lindsay, W. R. and Greenwood, W. F.: Hypothermia. Its Possible Role in Cardiac Surgery: An Investigation of Factors Governing Survival in Dogs at Low Body Temperature. Ann. Surge 132: 849, 1950. 10. McQuiston, W. 0.: Anesthesia for Cardiac Surgery in Children. Pede Clin, North America 1: 147, 1954. 11. Bickford, R. G.: The Fibre Dissociation Produced by Cooling Human Nerves. Clin. Sc. 4: 159, 1939. 12. Smith, L. W.: The Use of Cold in Medicine. Ann. Int. Med. 17: 618, 1942.
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13. Bigelow, W. G. and McBirnie, J. E.: Further Experiences with Hypothermia for Intracardiac Surgery with Monkeys and Groundhogs. Ann. Surge 137: 361, 1953. ,14. Boerema, I., Wildschut, A., Schmidt, W. J. H. and Broekhuysen, L.: Experimental Researches into Hypothermia as an Aid in Surgery of the Heart. Arch. chir. need. 3: 25, 1951. 15. Swan, Henry and Zeavin, Irvin: Cessation of Circulation in General Hypothermia. III. Technics of Intracardiac Surgery under Direct Vision. Ann. Surge 139:385,1954. 16. Varco, R. L.: Discussion of paper by Muller and Longmire. Surgery 30: 42,1951. 17. Bailey, C. P., et al.: Congenital Interatrial Communications: Clinical and Surgical Considerations with a Description of aNew Surgical Technic: Atrioseptopexy. Ann. Int. Med. 37: 888, 1952. 18. Beattie, E. J. Jr., Adovasio, D., Keshishian, J. H. and Blades, Brian: Refrigeration in Experimental Surgery of the Aorta. Surg., Gynec. & Obst. 96: 6, 1953. . 19. Edwards, W. S., Tuhey, S., Reber, W. E., Siegel, A. and Bing, R. J.: Coronary Blood Flow and Myocardial Metabolism in Hypothermia. Ann. Surge 139: 275, 1954. 20. Bigelow, A. A., Mustard, W. T. and Evans, J. G.: Some Physiologic Concepts of Hypothermia and Their Application to Cardiac Surgery. J. Thoracic Surge 28: 463, 1954. 21. Montgomery, A. V., Prevedal, A. E. and Swan, Henry: Prostigmine Inhibition of Ventricular Fibrillation in the Hypothermic Dog. Circulation 10: 721, 1954. 22. Swan, Henry, Zeavin, Irvin, Blount, S. Gilbert Jr. and Virtue, R. W.: Surgery by Direct Vision in the Open Heart During Hypothermia. J.A.M.A. 153: 1081, 1953. 23. Bobbio, A., Foffrini, P. and Bezzi, E.: Massive Hemorrhage Combined with Controlled General Hypothermia and Its Application to Experimental Cardiac Surgery. Bol. Soc. Piemont Chir. 24-: 428, 1954. 24. Scott, H. W. Jr., Collins, H. A. and Foster, J. A.: Hypothermia as an Adjuvant in Cardiovascular Surgery; Experimental and Clinical Observations. Ann. Surgeon 20: 799, 1954. 25. Collins, V. J. and Grantelli, A.: Controlled Hypothermia During Anesthesia in Human Adults. Use in Cardiovascular Surgery. Preliminary Observations. Angiology 6: 118, 1955. 26. Hardin, C. A., Reismann, K. R. and Dimond, E. G.: The Use of Hypothermia in the Resection and Homologous Graft Replacement of the Thoracic Grafts. Ann. Surge 14-0: 720, 1954. 27. Dogliotti, A. M. and Ciocatto, E.: Physiopathological Basis of Hypothermia and Possibilities of Combination of Hypothermia and Extracorpeal Circulation. Schweiz. med. Wchnschr. 83: 707, 1953. 28. Laborit, H. et Huguenard, P.: Technique actuelle de l'hibernation artificielle. Presse med. 60: 1455, 1952. 29. Laborit, H. et Huguenard, P.: Pratique de I'hibernotherapie en chirurgie et en medicine. Masson & Cie., 1954. 30. Symposium, Faculty Anesthetists Royal College of Surgeons: Present Status of Hypothermia in Anesthesia. Brit. M. J. 4919: 968, 1955. 31. Bartlett, R. G.: Apneustic Breathing Produced by Severe Hypothermia with Mild Anesthesia. Am. J. Physiol. 180: 433, 1955. 32. Miles, B. E. and Churchill-Davidson, H. C.: The Effect of Hypothermia on the Renal Circulation of the Dog. Anesthesiology 16: 230, 1955. 33. Papper, E. M.: Renal Function During General Anesthesia and Operation. ,T.A.M.A. 152: 1686, 1953. 34. Keown, Kenneth K.: Hypothermia. Chapter IV in Bailey, C. P.: Surgery of the Heart. Philadelphia, Lea & Febiger, 1955.
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35. Dogliotti, A. M. and Avicatto, E.: Surgical Possibihties on Bloodless Heart in Animals Treated with Ganglioplegic Substances and Hypothermia. Minerva med. 43: 891, 1952. 36. Pratt, Gerald H.: Amputation f-or Vascular Disease with Refrigeration Anesthesia. Postgraduate Med. 6: 490, 1949. 20 East 68th Street New York, N. Y. (Dr. Pratt)