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Monitoring during anesthesia
Anesthesiology Leonard
M. Monheim,
Monitoring
Editor
during anesthesia
Andrew G. To& D.D.S., Richard J. Ward, 3C.D., Gerald D. Allen, M.D., William P. Kennedy, Jr., M.D., and John J. Bonica, N.D., Seattle, Wash. DEPARTMENTS OF
OF
WASHINUTON
ANESTHESIOLOGY SCHOOLS
OF
AND MEDICINE
ORAL AND
SURGERY,
IJNIVERSITY
DENTISTRY
0
&patient general anesthesia for the oral surgical patient has in many respects revolutionized the practice of oral surgery. The ever-increasing frequency of its use has placed a greater burden of responsibility upon the administrator. Gawathmey very succinctly paraphrased the potential dangers of general anesthesia when he said: “To bring a human being to that borderline state in which life, in so many respects simulates death, is at no time a fool’s occupation. ’ ‘l The candidate for intraoral surgical intervention under general anesthesia faces certain unique potential anesthetic dangers. Specifically, since the operative site will be within the confines of the airway, the problems of secretions, hemorrhage, and maintenance of a patent airway are of paramount importance in the safe administration of an anesthetic. Some of the airway problems can be circumvented by nasotracheal or orotracheal intubation, but this certainly is not a panacea, for tracheal intubation itself involves certain inherent dangers.2-5 The functions of the person administering the anesthetic for intraoral surgery mill be numerous. He must maintain a patent airway, support and stabilize the patient’s head, maintain the proper flow rates and concentrations of inhalation anesthetic agents, control the intravenous infusion, and monitor the vital signs. Thus, at times it is almost impossible to give proper support to the mandible Supported Surgeon
General,
by
the
United
Contract
States
Brmy
Research
and
Development
Command,
Office
of
the
DA-49.193.MD-2231.
317
318
l’olus
et al.
and suprahyoid structures in the maintenance of a patent airway and still IF able to manipulate the monitoring equipment manually. The presence of an anest,hesiologist for all cases requiring general anesthesi;r would bc ideal. The surgeon’s responsibility \\ould bc lessened, allowing him to concentrate upon the surgical procedure. There is a shortage of anesthesiologists, lro~e~r, and the more com~non situation finds the oral surgeon supervising a registered-nurse anesthetist or a rcgistercd nurse specifically trained by him in the administration of an ant+th(~tic. In these instances the burden of responsibility rests upon the oral SIII*~COI~, who must wmnin aware of the patient’s status at all times. A monito,~ is dclinetl as 011~1\vho watches and warws. During anesthesia monitor*s serve as ad,juvants in the measurement of w&in physiologic parametws. It. is axiomatic that. the most important monitw during anesthetizat.ion is the attention of the individual ndministcring the anesthetic.F In the final analysis, it is t,hc close scrutiny and intcrprctation of tho monitored physiologic parameters which will give some idea 0~ insight as to the patient’s physiologic status. In selecting a monitor COY oral surgical nnest,hcsia, one should consider the following questions : What charactwistics would constitute the ideal monit,or ? To what degree do present-day monit,ors possess thcsc characteristics? The ideal monitor should bc primar*ily of a continuous nature, whereby any alteration in the parameter nrcasurc~d will be detected instantaneously as it, m mechanical or electronic maloccurs. It should be simple in make-up, ncgatin, function due to inhcrcnt complexit)-, and y-et. it should be relatively inexpensive. It should be foolproof, yielding no false positives and I’ew or no false negative findings. The monitor should not require active manipulation or visualization during the anesthetic 0~ surgical period. Finally, it should give usable and valuable information. All of the monitors in use at the present time fail to meet one or more of these requirements. The paramctcrs usuall,v measured arc respiration, blood pressure, and pulse. Respiration is evaluated by the case and depth of thoracoabdominal movement, plus the sound of anesthetic gas flowing thrbough the anesthetic machinc. Unfortunntelp, surgical drapes and equipment cffectivcly shield the rcspir’atorLy mo~cmcnts from the surgeon, and ancsthet ie machine noise cannot be correlated to actual pulmonar~y gas cschangc. Blood pressure determination by the arm-cuff met,hod gives nscful infor~maI,ion, but it requires active manipulation, which may be difficult to perform. KO information is available bctwccn determinations, and mechanical difficulties may give false readings. Digital palpation of the pulse provides important information. It also YCquires a,ctivc manipulation, which may be difficult to perform, and no information is available bet,ween observations. The efficacy of various continuous cardiac monitors, such as electrocardiographs or QRS monitors, in oral surgery is questionable. Although continuous, they arc expensive, highly complex in make-up, and require experience in interpretation. The irrformatiorr obtnincd is valuable and yet, by itself, may not
Volume Xumber
19 3
Monitoring
during
anesthesia
319
be particularly useful. The greatest shortcoming is that the surgeon must concentrate on the monitor rather than on the patient. Serious arrythmias may occur without detection if the surgeon concentrates on the surgical procedure. Since the electrocardiogram represents the electrical events of depolarization and repolarization, it is unable to demonstrate the integrity of myocardial cont,ractibility.7 A failing myocardium, secondary to hypoxia or cardiac decompensation, or even cardiac arrest may be represented by a normal-appearing electrocardiogram for a brief period. The QRS monitor functions much as t.he electrocardiogram in using standard bipolar limb leads. The electrical events of the cardiac cycle arc not represented by any tracing but trigger a flashing light or produce a sound with each occurrence of the cardiac cycle. It tells only t.hat some sort of electrical impulse has passed through the conduction apparatus. The monitor may be incapable of detecting cardiac arrest and arrythmias. It has a very limited place in clinical anesthesia. Automatic blood pressure monit.ors and digital plethysmographs have been advocated for routine clinical use. These are expensive, complex electronic devices and may cause confusion if they are malfunctioning. The failure of all the routine monitors to satisfy the criteria of the “ideal” has led us to employ the cardiophone, which consists of a pressure-sensitive stethoscope head, sensitive to 15 to 300 cycles per second. The heart sounds are amplified and transmitted to a loudspeaker. The stethoscope is lightly taped into position over the precordium, and the volume is adjusted to the desired level. This may be readily accomplished hy office personnel as the patient is being prepared for induction of anesthesia. Cont.innous auscultation of t.he heart and respiratory sounds provides the maximum possible information. The rat.e and regularity of the cardiac cpclc are continuously known. Arrythmias are detected the instant they develop. Subtle changes in intensity of the heart sounds are a reflection of the cardiac pressure pattern and, with continuous monitoring, increased expcricnce will permit the proper assessment of this parameter. Active manipulation is not necessary to receive the information. Distraction from t,he surgical procedure dots not occur, as the information is heard rather than seen. The device is simple, inexpensive, and has no moving parts. Thwc are no false positive or negative findings t,o alarm the S11rgicill Icam lutnccc!ssuril~~. SUMMARY Continuous auscultatory most direct and foolproof dynamics during surgery.
monitoring of heart sounds has proved t)o be the m&hod of evaluating alterations in cardiovascular
REFERENCES
1. Symposium on General Anesthesia and Premeditation College of Dentistry, 1961, p. 37. 2. Devaust,, M., Greifenstein, F. E., and Harris, L. C.: Intubatlon in Higher General Anesthesia; the Effect thesiology 21: 360, 1960.
for
Dentists,
Circulatory of Atropine
University
of
IlIinois
Responses to Endotracheal and Phentolamine, Anes-
320
1’01a.s et al.
O.S., O.M. & 0.1’. March
? 7965 *
3. Scott, M., and Brechner, V. I,.: Retrobulbar Hemorrhage From Nasotrachc~al 1 nt ubat ion. Anesthesiology 20: 717, 1959. 4. Smith, R. H., Pool, L. L, and Volpitto, P. P.: Subcutaneous Emphysema as a Complication\ of Endotracheal Intubatlon, Anesthesiology 20: 714, 1959. t,o Anesthesia, etl. 2. 5. Dripps, R. D., EckenhofT, J. E., and Vandam, L. D.: Jntroduction Philadelphia, 1961, W. B. Saunders Company. 6. Cullen, S. C.: Monitors and Clinical Judgment, AnesthesiologJr 23: 120, 1961. Philadelphia, 1946, Lea k Fcbiger, p. 80. 7. Katz, Louis NT.: Electrocardiography,
M. Monheim,
Monitoring
Editor
during anesthesia
Andrew G. To& D.D.S., Richard J. Ward, 3C.D., Gerald D. Allen, M.D., William P. Kennedy, Jr., M.D., and John J. Bonica, N.D., Seattle, Wash. DEPARTMENTS OF
OF
WASHINUTON
ANESTHESIOLOGY SCHOOLS
OF
AND MEDICINE
ORAL AND
SURGERY,
IJNIVERSITY
DENTISTRY
0
&patient general anesthesia for the oral surgical patient has in many respects revolutionized the practice of oral surgery. The ever-increasing frequency of its use has placed a greater burden of responsibility upon the administrator. Gawathmey very succinctly paraphrased the potential dangers of general anesthesia when he said: “To bring a human being to that borderline state in which life, in so many respects simulates death, is at no time a fool’s occupation. ’ ‘l The candidate for intraoral surgical intervention under general anesthesia faces certain unique potential anesthetic dangers. Specifically, since the operative site will be within the confines of the airway, the problems of secretions, hemorrhage, and maintenance of a patent airway are of paramount importance in the safe administration of an anesthetic. Some of the airway problems can be circumvented by nasotracheal or orotracheal intubation, but this certainly is not a panacea, for tracheal intubation itself involves certain inherent dangers.2-5 The functions of the person administering the anesthetic for intraoral surgery mill be numerous. He must maintain a patent airway, support and stabilize the patient’s head, maintain the proper flow rates and concentrations of inhalation anesthetic agents, control the intravenous infusion, and monitor the vital signs. Thus, at times it is almost impossible to give proper support to the mandible Supported Surgeon
General,
by
the
United
Contract
States
Brmy
Research
and
Development
Command,
Office
of
the
DA-49.193.MD-2231.
317
318
l’olus
et al.
and suprahyoid structures in the maintenance of a patent airway and still IF able to manipulate the monitoring equipment manually. The presence of an anest,hesiologist for all cases requiring general anesthesi;r would bc ideal. The surgeon’s responsibility \\ould bc lessened, allowing him to concentrate upon the surgical procedure. There is a shortage of anesthesiologists, lro~e~r, and the more com~non situation finds the oral surgeon supervising a registered-nurse anesthetist or a rcgistercd nurse specifically trained by him in the administration of an ant+th(~tic. In these instances the burden of responsibility rests upon the oral SIII*~COI~, who must wmnin aware of the patient’s status at all times. A monito,~ is dclinetl as 011~1\vho watches and warws. During anesthesia monitor*s serve as ad,juvants in the measurement of w&in physiologic parametws. It. is axiomatic that. the most important monitw during anesthetizat.ion is the attention of the individual ndministcring the anesthetic.F In the final analysis, it is t,hc close scrutiny and intcrprctation of tho monitored physiologic parameters which will give some idea 0~ insight as to the patient’s physiologic status. In selecting a monitor COY oral surgical nnest,hcsia, one should consider the following questions : What charactwistics would constitute the ideal monit,or ? To what degree do present-day monit,ors possess thcsc characteristics? The ideal monitor should bc primar*ily of a continuous nature, whereby any alteration in the parameter nrcasurc~d will be detected instantaneously as it, m mechanical or electronic maloccurs. It should be simple in make-up, ncgatin, function due to inhcrcnt complexit)-, and y-et. it should be relatively inexpensive. It should be foolproof, yielding no false positives and I’ew or no false negative findings. The monitor should not require active manipulation or visualization during the anesthetic 0~ surgical period. Finally, it should give usable and valuable information. All of the monitors in use at the present time fail to meet one or more of these requirements. The paramctcrs usuall,v measured arc respiration, blood pressure, and pulse. Respiration is evaluated by the case and depth of thoracoabdominal movement, plus the sound of anesthetic gas flowing thrbough the anesthetic machinc. Unfortunntelp, surgical drapes and equipment cffectivcly shield the rcspir’atorLy mo~cmcnts from the surgeon, and ancsthet ie machine noise cannot be correlated to actual pulmonar~y gas cschangc. Blood pressure determination by the arm-cuff met,hod gives nscful infor~maI,ion, but it requires active manipulation, which may be difficult to perform. KO information is available bctwccn determinations, and mechanical difficulties may give false readings. Digital palpation of the pulse provides important information. It also YCquires a,ctivc manipulation, which may be difficult to perform, and no information is available bet,ween observations. The efficacy of various continuous cardiac monitors, such as electrocardiographs or QRS monitors, in oral surgery is questionable. Although continuous, they arc expensive, highly complex in make-up, and require experience in interpretation. The irrformatiorr obtnincd is valuable and yet, by itself, may not
Volume Xumber
19 3
Monitoring
during
anesthesia
319
be particularly useful. The greatest shortcoming is that the surgeon must concentrate on the monitor rather than on the patient. Serious arrythmias may occur without detection if the surgeon concentrates on the surgical procedure. Since the electrocardiogram represents the electrical events of depolarization and repolarization, it is unable to demonstrate the integrity of myocardial cont,ractibility.7 A failing myocardium, secondary to hypoxia or cardiac decompensation, or even cardiac arrest may be represented by a normal-appearing electrocardiogram for a brief period. The QRS monitor functions much as t.he electrocardiogram in using standard bipolar limb leads. The electrical events of the cardiac cycle arc not represented by any tracing but trigger a flashing light or produce a sound with each occurrence of the cardiac cycle. It tells only t.hat some sort of electrical impulse has passed through the conduction apparatus. The monitor may be incapable of detecting cardiac arrest and arrythmias. It has a very limited place in clinical anesthesia. Automatic blood pressure monit.ors and digital plethysmographs have been advocated for routine clinical use. These are expensive, complex electronic devices and may cause confusion if they are malfunctioning. The failure of all the routine monitors to satisfy the criteria of the “ideal” has led us to employ the cardiophone, which consists of a pressure-sensitive stethoscope head, sensitive to 15 to 300 cycles per second. The heart sounds are amplified and transmitted to a loudspeaker. The stethoscope is lightly taped into position over the precordium, and the volume is adjusted to the desired level. This may be readily accomplished hy office personnel as the patient is being prepared for induction of anesthesia. Cont.innous auscultation of t.he heart and respiratory sounds provides the maximum possible information. The rat.e and regularity of the cardiac cpclc are continuously known. Arrythmias are detected the instant they develop. Subtle changes in intensity of the heart sounds are a reflection of the cardiac pressure pattern and, with continuous monitoring, increased expcricnce will permit the proper assessment of this parameter. Active manipulation is not necessary to receive the information. Distraction from t,he surgical procedure dots not occur, as the information is heard rather than seen. The device is simple, inexpensive, and has no moving parts. Thwc are no false positive or negative findings t,o alarm the S11rgicill Icam lutnccc!ssuril~~. SUMMARY Continuous auscultatory most direct and foolproof dynamics during surgery.
monitoring of heart sounds has proved t)o be the m&hod of evaluating alterations in cardiovascular
REFERENCES
1. Symposium on General Anesthesia and Premeditation College of Dentistry, 1961, p. 37. 2. Devaust,, M., Greifenstein, F. E., and Harris, L. C.: Intubatlon in Higher General Anesthesia; the Effect thesiology 21: 360, 1960.
for
Dentists,
Circulatory of Atropine
University
of
IlIinois
Responses to Endotracheal and Phentolamine, Anes-
320
1’01a.s et al.
O.S., O.M. & 0.1’. March
? 7965 *
3. Scott, M., and Brechner, V. I,.: Retrobulbar Hemorrhage From Nasotrachc~al 1 nt ubat ion. Anesthesiology 20: 717, 1959. 4. Smith, R. H., Pool, L. L, and Volpitto, P. P.: Subcutaneous Emphysema as a Complication\ of Endotracheal Intubatlon, Anesthesiology 20: 714, 1959. t,o Anesthesia, etl. 2. 5. Dripps, R. D., EckenhofT, J. E., and Vandam, L. D.: Jntroduction Philadelphia, 1961, W. B. Saunders Company. 6. Cullen, S. C.: Monitors and Clinical Judgment, AnesthesiologJr 23: 120, 1961. Philadelphia, 1946, Lea k Fcbiger, p. 80. 7. Katz, Louis NT.: Electrocardiography,