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Arrest of cerebral blood flow and reperfusion of the brain in the rhesus monkey
Resuscitation (x972), x, 39
Arrest of cerebral blood flow and reperfkion of the brain in the rhesus monkey L. R. WOLIN,
L. C. MASSOPUST,
Jr., R. J. WHITE*
Laboratoti of JVeuropychology and Nwophysiology, Institute, Cleveland, Ohio 44-109, U.S.A.
and N. TASLITZt
Research Division, Cleveland Psychiatric
Rhesus monkeys were subjected to cerebral ischaemia by arresting blood flow to the brain. The carotid and vertebral arteries were temporarily occluded and a cannula inserted into one common carotid artery permitted retrodrainage of blood reaching the circle of Willis via anastomotic channels. The blood from the cerebral vessels was washed out with dextran solution for photographic recording of the arrest of cerebral blood flow and subsequent reperfusion of the cerebral vasculature. Electroencephalographic, cardiovascular and respiratory functions were monitored throughout the procedure. Occlusion of the four major vessels with retrodrainage of the circle of Willis effectively stops perfusion of the brain. Occlusion of the vessels without retrodrainage permits a slow but significant flow of blood to the cerebral vessels. Rapid and effective reperliiion of the brain was noted even after repeated and lengthy periods of ischaemia. Thus a model for studying cerebral ischaemia, and reperfusion after ischaemia, without major thoracic or intracranial intervention is demonstrated. Some implications for resuscitation in cases of cerebral ischaemia are discussed.
The brain cannot long survive anoxia or ischaemia. Time thus is of the utmost importance whenever conditions arise which interfere with adequate cerebral perfusion. A variety of conditions may reduce or eliminate cerebral blood flow to the entire brain or localized areas. Foremost amongst these are cardiac arrest, cerebrovascular occlusion due to thrombosis, embolism or spasm, and cerebral oedema. Whatever the cause, the immediate concern is to re-establish adequate cerebral perfusion as rapidly as possible to reduce or eliminate damage to the highly sensitive neural tissue. Several recent studies have demonstrated that under controlled laboratory conditions cerebral ischaemia may be tolerated for considerably longer periods of time than could be expected from examination of the clinical literature. Hossmann & Sato (1g7oa, b) have recovered EEG activity and evoked potentials in acute cat preparations after as long as go min of cerebral ischaemia. Ischaemia was accomplished by clamping various combinations of arteries (common carotids and basilar; *Divisionof Neurosurgery, Cleveland Metropolitan General Hospital and Case Western Reserve University Medical School. t Department of Anatomy, Case Western Reserve University Medical School. 39
40
L. R. WOLIN,
L. C. MASSOPUST,
JR.,
R. J. WHITE
AND
N. TASLITZ
innominate and left subclavian; innominate, left subclavian and basilar). Reperfusion of the cerebral vessels was good after release of the vascular clamps, but after about 20 min a secondary suppression of electrophysiological activity associated with reduced blood flow was noted in animals subjected to more than 6 min of ischaemia. By perfusing the ischaemic cat brain with dextran, calf serum or Ringer’s solution, Hossman & Olsson (1970) obtained rapid recovery of electrophysiological function without secondary suppression of activity. Yashon et al. (I 970) have likewise demonstrated recovery of electrocortical activity in dogs after periods of cerebral ischaemia of up to 20 min. Ischaemia was produced by clamping the ascending aorta and both vena cavae. Some animals survived this procedure, including one dog subjected to 12 min of ischaemia. There was also a positive relationship between rapidity of recovery of EEG activity and survival. Two recent studies with primates have demonstrated survival after periods of prolonged cerebral ischaemia. Miller & Myers (1970) induced periods of cerebral ischaemia ranging from 8 to 24 min. Induction of ischaemia was performed by clamping of the ascending aorta and both vena cavae. Extensive pharmacological support was employed in attempting to obtain recovery of the animals after ischaemia. Mortality increased greatly with longer duration of ischaemia, but one animal of three subjected to 24 min of cerebral ischaemia survived for more than 4 days after surgery. Wolin et al. (197 ~a) exposed 20 monkeys to ischaemia of 4-15 min duration. Ischaemia was produced by occlusion of the carotid and vertebral arteries and the provision of a special retrodrainage cannula (see the Materials and methods section). Successful recovery (more than 6 months survival) was possible after 14 min of ischaemia, but no animals recovered after 15 min. In our original studies, absence of cerebral blood flow was inferred from loss of EEG activity and spontaneous respiration. The present report demonstrates both the effectiveness of the procedure employed in our previous experiments on arrest of cerebral blood flow and the rapid and effective reperfusion of the brain even after repeated and extended periods of arrest. Materials and methods The subjects for this study were three rhesus monkeys (Macaca mulatta) of both sexes, ranging in weight from 3.0 to 3’8 kg. The animals were anaesthetized with intravenous pentobarbital sodium (Nembutal), 30 mg/kg. Each animal was then intubated with an endotracheal tube to provide respiratory support during the arrest of cerebral blood flow. A femoral artery was cannulated for monitoring of blood pressure, and one pair of silver ball electrodes was bilaterally implanted epidurally through trephine holes in the calvarium overlying the somaesthetic sensory cortex, for monitoring of EEG activity. A large craniotomy was performed over the mid-temporal region on one side to provide for observation and photographic recording of changes in cerebral perfusion. Photographs were taken through an appropriately equipped Zeiss surgical microscope. Surgisal preparation Preparation for the cerebral arrest consisted of making a ventral midline cervical incision, through which the two common carotid arteries and their bifurcations were
CEREBRAL
WREST
AND
REPERFUSION
0F THE
mum
41
exposed. The vertebral arteries were exposed via this ventral approach just caudal to the body of the sixth cervical vertebra. Silk ligatures were passed with a Ferguson ligature carrier around both external carotid and both vertebral arteries and threaded through a short glass tube, which permitted temporary non-traumatic occlusion. After treatment of the animal with anticoagulant (heparin, 3 mg/kg), a Teflon cannula was inserted into the left common carotid artery to permit both drainage of arterial blood from the circle of Willis and infusion of dextran into the cerebral vasculature. Since this was a straight can&a, its insertion required closing of the common carotid artery below the point of entry. The two external carotid arteries and the two vertebral arteries were then occluded, the brain then being perfused by the uncannulated right internal carotid artery. Previous work has shown that the rhesus monkey brain can be maintained by perfusion through a single carotid artery for long periods of time (Taslitz et al. rgyoa; Donald & White, 1961). The EEG activity was recorded and perfusion of the exposed cortex visually monitored throughout these procedures. Cerebral arrest sequetue The basic arrest procedure simply involved clamping of the functional common artery and simultaneously opening the cannula in the other common carotid, permitting retrodrainage of the circle of Willis. This retrodrainage is necessary; previous work has demonstrated that an average of 3-g ml of blood will reach the cerebral vasculature via anastomotic channels even when the four major vessels are occluded (Taslitz et al. Ig7ob). Reperfusion of the brain was accomplished by reversing the above procedure. Several variations of the above procedure were employed to document changes in cerebral perfusion by the use of still photography. One variation involved flushing out the cerebral vasculature with 6% dextran immediately after clamping the functional carotid artery. The cannula was then opened and the exposed blood vessels were observed and photographed. During the period of arrest with the retrodrainage cannula open fluids (dextran solution, blood and a combination of these) were collected and measured. The flow rate averaged approximately 4 ml/min, which is roughly 10% of the calculated normal cerebral blood flow for monkeys of this size. Pathways providing for anastomotic flows to brain with the major vessels occluded have been previously detailed (Taslitz et d. 19706; Wolin et al. I971 b) . After several minutes of arrest the cannula was closed and reperfusion of vessels recorded photographically. The occluded carotid artery was then opened and the complete reperfusion photographed. Another variation involved the same basic procedure, but in thii case the drainage cannula remained closed. The exposed vessels were again photographed during the arrest period without retrodrainage and again after reopening of the carotid. Between I and 2 min after arrest of cerebral blood flow, spontaneous respiration ceased. The animal was then supported ;&m;dBird respirator with Os+COs (95 : 5, v /v ) until spontaneous respiration After the experimental procedures, the instruments were removed from the animals, the cannulated carotid artery was reconstituted, and all wounds were closed. The cumulative period of ischaemia in each case was approximately 20 min, and none of the animals survived beyond 24 h postsurgically.
42
L. R. WOLIN, L. C. MASSOPUST, JR., R. J. WHITE AND N. TASLITZ
Results Clamping of the carotid and vertebral arteries with simultaneous opening of the cannula, which provided for retrodrainage of the circle of Willis, resulted in immediate cessation of detectable blood flow in the exposed pial vessels. This resulted in loss of all EEG activity within 15-q s, a brief drop in arterial blood pressure (20-40 mmHg systolic) followed by a rise of blood pressure to 20-30 mmHg above pre-occlusion levels, and the loss of spontaneous respiration within 1.5-2 min. The heart rate also changed after occlusion of all arteries. With occlusion and retrodrainage, heart rate increased approximately 10% within the first minute, continued to increase to about 40% above pre-occlusion levels by IO min, then gradually dropped and returned to near baseline level after reperfkion. The major increase in heart rate started immediately after the initiation of mechanical respiratory support. During occlusion without retrodrainage there was also an initial rise in heart rate. In this procedure respiratory support was not required and after several minutes the rate began to drop, returning to pre-occlusion levels or slightly below. The cortical perfusion via a single carotid artery is shown in Plate I. After the occlusion of the functional carotid
1
2
3
F3g. x. Excerpted electrocorticogran~ from the sensory cortex showing changes in activity before (I and 4) and immediatelyat&r (I and 5) occlusivearrest &brain arterial circulation. 3 and 6 show the degree of suppressionof EEG after occlusion. I, 2 and 3, Incomplete occlusivecirculatory arrest. 4, 5 and 6, Complete occlusive circulatory arrest. Note the electrocardiogram on isoelectric tracing (6). Calibration: vertical mark = IOO pV for 1-5, 20 PV for 6; horizontal mark = I a.
and opening of the retrodrain, the cortical vessels remained filled (Plate IB) but no pulsation or flow of blood was visible. Some pallor of the cortex was seen, but the change was not dramatic. When the drainage cannula was closed and the intact common carotid opened, immediate reperfusion of all vessels was noted (Plate IC). The second arrest procedure involved flushing the cerebral vasculature with approximately IO ml of 6% dextran (Plate 2A and B). While the drainage cannula remained open little perfusion was seen, but, upon closure of the drainage cannula, the blood flow slowly resumed (Plate 2C and D). Reopening of the occluded carotid artery resulted in immediate reperfusion of the vascular bed (Plate 3A). The third arrest procedure involved wash-out with dextran after occlusion, but with no retrodrainage provided (Plate 3B, C and D). Finally, the occluded carotid artery was again opened (Plate 4) and excellent reperfusion of the brain was noted. The contrast between total and subtotal arrest of cerebral blood flow on EEG activity is illustrated in Fig. I. The upper set of traces shows the depression and slowing of the EEG in subtotal arrest (drainage cammla closed) ; the EEG continues
CEREBRAL
ARREST AND REPERFUSION OF THE BRAIN
43
to show activity. In the lower set of traces, complete arrest with retrodrainage has been accomplished. The third segment (recorded at high sensitivity) reveals no EEG activity, but only small electrocardiogram artifact.
There are a number of interesting implications which have some bearing on problems of resuscitation in general and prevention of brain damage in particular. Most of the preparations, both actute and chronic, used in cerebral ischaemia studies have involved systemic anticoagulation. Hossman & Olsson (1970) used both heparinized and non-heparinized preparations and, although they reported longer delays in development of secondary suppression of neurophysiological activity in the heparinized animals, they nevertheless questioned the therapeutic efficacy of heparin. Crowell et al. (x955), however, caused circulatory arrest in dogs by producing cardiac fibrillation and respiratory arrest. They found emboli in the heart and lungs of animals after IO min of arrest. Animals given heparin showed higher survival rates than nonheparinized animals. Using monkeys, Smith, Ducker & Kempe (1969) also showed decreased incidence of infarction with up to 30 min of occlusion of the middle cerebral artery when the animals were pretreated with large doses of heparin. Ames et al. (1g68), in a study with rabbits, used both heparin premeditation and wash-out of blood with Ringer’s solution. They reported only slight protection from heparin and also presented evidence of narrowing of blood vessels, thus restricting reperfusion even after wash-out. It has been our experience that any procedure requiring cannulation of major vessels or temporary occlusion of major vessels invariably resulted in secondary complications in the absence of prior systemic anticoagulation. In the present experiment, the use of dextran wash-out of blood from the brain was employed only as a means of illustrating the effectiveness of arrest and reperfusion. Hossmann & Olsson (1970) used dextran, calf serum or Ringer’s solution for this purpose, and reported that this procedure prevented secondary complication in maintaining postischaemic blood flow. It should also be noted that they used solutions at 25°C in most cases and that the reduction in brain temperature which would occur under these conditions would in itself have a protective effect on the brain (White et al. 1969). Wolfson et al. (x964), Wolfson, Icoz & Luber (Ig65a) and Wolfson et al. (I g656) have also used cold saline wash-out of the brain as a means of inducing hypothermia for neurosurgical purposes, and the evidence suggests that this may be a potentially efficient procedure for protection of the brain against ischaemia. Actually two advantages are apparent, one being the protective effects of hypothermia and the second the clearing of blood from the capillary system, thus reducing the possibility of clotting and also washing out metabolic products [lactate etc.). This would, of course, be particularly advantageous when anticoagulation measures have not, or cannot, be employed. The use of either anticoagulation or wash-out procedures appears to facilitate the re-establishment of rapid, effective perfusion of the brain after ischaemia and appears to reduce the incidence of secondary circulatory complications. We thus see that occlusion of the carotid and vertebral arteries is insufficient to stop all blood flow to the brain in the monkey. Provision of a retrodrainage system directly from the circle of Willis does effectively eliminate cortical blood flow (Wolin
‘$4
L. R. WOLIN,
L. C. MASSOPUST, JR., R. J. WHITE AND N. TASLITZ
After repeated arrest of cerebral circulation involving both stagnation of blood and wash-out of the cerebral vasculature with de&ran, immediate and effective reperfitsion of the brain occurs. In conclusion, it has been repeatedly demonstrated that recovery of brain function is possible after extended periods of ischaemia. Several studies have also demonstrated long-term survival of primates after cerebral ischaemia, often with little or no demonstrable neurological or behavioural deficits. Rapid and effective reperfusion of the brain after ischaemia appears critical for survival and reduction or elimination of brain damage. Use of anticoagulation, vascular wash-out or hypothermia, or any combination of these procedures, appears to be advantageous in facilitating recovery from ischaemic insult to the brain.
et al. Ig7Ia).
Acknowledgements This work was supported by grants NS 06552 and NS 03859 from the National Institutes of Health. References Ames, A., III, Wright, R. L., Kowada, M., Thuraton, J. M. & Majno, G. (xg68) Cerebral iachemia. II. The no-reflow phenomenon. Am. J. Path. 5n, 437- 5 . Crowell, J. W., Sharpe, G. P., Lambright, R. L. & Rea$ !4 . L. (1955) The mechanism of death after resuscitation following acute circulatory failure. Swgwy 2 6$7o** occ usIon of the common carotid and verteDonald, D. E. & White, R. J. (@I) Temporary bilat bral arteries in the monkey at normal body temperature. Nclrrologl II, 836-838. Hossmann, K.-A. & Olson, Y. (1970) Suppression and recovery of neuronal function in transient cerebral ischemia. Brain as. 00,313-325. Hossmann, K.-A. & Sato, K. (xg7oa) The effect of ischemia on sensorimotor cortex of cat. <. Jk&. 198s 33-45 Hoscrmann, K.-A. & Sato, K. (19706). Recovery of neuronal function after prolonged cerebral kchemia. science 16% 375-376. Miller, J. R. & Myers, R. E. (x970) Ne.urological effects of systemic circulatory arrest in the monkey. &WV&~OO, 715-724. L. G. (I g6g) Temporary experimental intracranial vascular Smith, D. R., Ducker, T. B. & Kern occlusion. Effect of massive doses oF heparin on brain survival. 3. Navana. Task, N., White, R. J., Wolin, L. R. & Yashon, D. (19706) Adequacy of $rn$ %%u-!F perfusion of the brain. Anut.Rec.166,388. Task, N., Wolin, L. R., Maso ust, L. C., Jr., White, R. J. & Kadoya, S. (Igfob) Blood flow to brain following arterial occlusion. Psd. Proc. og, 520. White, R. J., Masaopust, L. C., Jr., Wolin, L. R., Taslitz, N. & Yashon, D. (1g6g) Profound selective cooling and ischemia of primate brain without pump or oxygenator. surgag 66,224-232. Wolfkn, S. K., Jr., Icoz, M. V., Inouye! W. Y. & Parkins, W. M. (1964) Prolonged circulatory arrest with preferential cerebral hypothenma and resuscitation by external cardiac massage. Surg. Fwum
xv,
4’5-417.
Wolf&m, S. K., Jr., Icoz, M. V. & Lubw, S. (Ig65u) Preservation of conditioned responses in primates after total circulatory arrest with pwfkrential cerebral hypothermia. Surg. Forum XVI, 4og-41 I. Wolf&m, S. K., Jr., Inouye, W. Y., Kavianian, A., Icon, M. V. & Parkins, W. M. (9656). Preferential cerebral hypothermia for circulatory arrest. Swg 579 846-855. Wolin, L. R., M2ssopust, L. C., Jr., Taslitz, N. & Fz te+R. J. (rg7ra) Cerebral perlkion and cerebral arrest in the rhesus monkey. AMt. Rec. x6g, 457. Wolin, L. R., Masaopust, L. C., Jr. & Taslitz, N. (‘g71b) Tolerance to arrest of cerebral circulation in the rhesus monkey. E*p. .hkol. 30, 103-115. Yashon, D., White, R. J., Taslitz, N., Wolin, L. R. & Massopust, L. C., Jr. (1970) Experimental cerebral circulatory arrest. Effect on electrocortical potentials. 3. &UVXW 6 3%74-82.
Arrest of cerebral blood flow and reperfkion of the brain in the rhesus monkey L. R. WOLIN,
L. C. MASSOPUST,
Jr., R. J. WHITE*
Laboratoti of JVeuropychology and Nwophysiology, Institute, Cleveland, Ohio 44-109, U.S.A.
and N. TASLITZt
Research Division, Cleveland Psychiatric
Rhesus monkeys were subjected to cerebral ischaemia by arresting blood flow to the brain. The carotid and vertebral arteries were temporarily occluded and a cannula inserted into one common carotid artery permitted retrodrainage of blood reaching the circle of Willis via anastomotic channels. The blood from the cerebral vessels was washed out with dextran solution for photographic recording of the arrest of cerebral blood flow and subsequent reperfusion of the cerebral vasculature. Electroencephalographic, cardiovascular and respiratory functions were monitored throughout the procedure. Occlusion of the four major vessels with retrodrainage of the circle of Willis effectively stops perfusion of the brain. Occlusion of the vessels without retrodrainage permits a slow but significant flow of blood to the cerebral vessels. Rapid and effective reperliiion of the brain was noted even after repeated and lengthy periods of ischaemia. Thus a model for studying cerebral ischaemia, and reperfusion after ischaemia, without major thoracic or intracranial intervention is demonstrated. Some implications for resuscitation in cases of cerebral ischaemia are discussed.
The brain cannot long survive anoxia or ischaemia. Time thus is of the utmost importance whenever conditions arise which interfere with adequate cerebral perfusion. A variety of conditions may reduce or eliminate cerebral blood flow to the entire brain or localized areas. Foremost amongst these are cardiac arrest, cerebrovascular occlusion due to thrombosis, embolism or spasm, and cerebral oedema. Whatever the cause, the immediate concern is to re-establish adequate cerebral perfusion as rapidly as possible to reduce or eliminate damage to the highly sensitive neural tissue. Several recent studies have demonstrated that under controlled laboratory conditions cerebral ischaemia may be tolerated for considerably longer periods of time than could be expected from examination of the clinical literature. Hossmann & Sato (1g7oa, b) have recovered EEG activity and evoked potentials in acute cat preparations after as long as go min of cerebral ischaemia. Ischaemia was accomplished by clamping various combinations of arteries (common carotids and basilar; *Divisionof Neurosurgery, Cleveland Metropolitan General Hospital and Case Western Reserve University Medical School. t Department of Anatomy, Case Western Reserve University Medical School. 39
40
L. R. WOLIN,
L. C. MASSOPUST,
JR.,
R. J. WHITE
AND
N. TASLITZ
innominate and left subclavian; innominate, left subclavian and basilar). Reperfusion of the cerebral vessels was good after release of the vascular clamps, but after about 20 min a secondary suppression of electrophysiological activity associated with reduced blood flow was noted in animals subjected to more than 6 min of ischaemia. By perfusing the ischaemic cat brain with dextran, calf serum or Ringer’s solution, Hossman & Olsson (1970) obtained rapid recovery of electrophysiological function without secondary suppression of activity. Yashon et al. (I 970) have likewise demonstrated recovery of electrocortical activity in dogs after periods of cerebral ischaemia of up to 20 min. Ischaemia was produced by clamping the ascending aorta and both vena cavae. Some animals survived this procedure, including one dog subjected to 12 min of ischaemia. There was also a positive relationship between rapidity of recovery of EEG activity and survival. Two recent studies with primates have demonstrated survival after periods of prolonged cerebral ischaemia. Miller & Myers (1970) induced periods of cerebral ischaemia ranging from 8 to 24 min. Induction of ischaemia was performed by clamping of the ascending aorta and both vena cavae. Extensive pharmacological support was employed in attempting to obtain recovery of the animals after ischaemia. Mortality increased greatly with longer duration of ischaemia, but one animal of three subjected to 24 min of cerebral ischaemia survived for more than 4 days after surgery. Wolin et al. (197 ~a) exposed 20 monkeys to ischaemia of 4-15 min duration. Ischaemia was produced by occlusion of the carotid and vertebral arteries and the provision of a special retrodrainage cannula (see the Materials and methods section). Successful recovery (more than 6 months survival) was possible after 14 min of ischaemia, but no animals recovered after 15 min. In our original studies, absence of cerebral blood flow was inferred from loss of EEG activity and spontaneous respiration. The present report demonstrates both the effectiveness of the procedure employed in our previous experiments on arrest of cerebral blood flow and the rapid and effective reperfusion of the brain even after repeated and extended periods of arrest. Materials and methods The subjects for this study were three rhesus monkeys (Macaca mulatta) of both sexes, ranging in weight from 3.0 to 3’8 kg. The animals were anaesthetized with intravenous pentobarbital sodium (Nembutal), 30 mg/kg. Each animal was then intubated with an endotracheal tube to provide respiratory support during the arrest of cerebral blood flow. A femoral artery was cannulated for monitoring of blood pressure, and one pair of silver ball electrodes was bilaterally implanted epidurally through trephine holes in the calvarium overlying the somaesthetic sensory cortex, for monitoring of EEG activity. A large craniotomy was performed over the mid-temporal region on one side to provide for observation and photographic recording of changes in cerebral perfusion. Photographs were taken through an appropriately equipped Zeiss surgical microscope. Surgisal preparation Preparation for the cerebral arrest consisted of making a ventral midline cervical incision, through which the two common carotid arteries and their bifurcations were
CEREBRAL
WREST
AND
REPERFUSION
0F THE
mum
41
exposed. The vertebral arteries were exposed via this ventral approach just caudal to the body of the sixth cervical vertebra. Silk ligatures were passed with a Ferguson ligature carrier around both external carotid and both vertebral arteries and threaded through a short glass tube, which permitted temporary non-traumatic occlusion. After treatment of the animal with anticoagulant (heparin, 3 mg/kg), a Teflon cannula was inserted into the left common carotid artery to permit both drainage of arterial blood from the circle of Willis and infusion of dextran into the cerebral vasculature. Since this was a straight can&a, its insertion required closing of the common carotid artery below the point of entry. The two external carotid arteries and the two vertebral arteries were then occluded, the brain then being perfused by the uncannulated right internal carotid artery. Previous work has shown that the rhesus monkey brain can be maintained by perfusion through a single carotid artery for long periods of time (Taslitz et al. rgyoa; Donald & White, 1961). The EEG activity was recorded and perfusion of the exposed cortex visually monitored throughout these procedures. Cerebral arrest sequetue The basic arrest procedure simply involved clamping of the functional common artery and simultaneously opening the cannula in the other common carotid, permitting retrodrainage of the circle of Willis. This retrodrainage is necessary; previous work has demonstrated that an average of 3-g ml of blood will reach the cerebral vasculature via anastomotic channels even when the four major vessels are occluded (Taslitz et al. Ig7ob). Reperfusion of the brain was accomplished by reversing the above procedure. Several variations of the above procedure were employed to document changes in cerebral perfusion by the use of still photography. One variation involved flushing out the cerebral vasculature with 6% dextran immediately after clamping the functional carotid artery. The cannula was then opened and the exposed blood vessels were observed and photographed. During the period of arrest with the retrodrainage cannula open fluids (dextran solution, blood and a combination of these) were collected and measured. The flow rate averaged approximately 4 ml/min, which is roughly 10% of the calculated normal cerebral blood flow for monkeys of this size. Pathways providing for anastomotic flows to brain with the major vessels occluded have been previously detailed (Taslitz et d. 19706; Wolin et al. I971 b) . After several minutes of arrest the cannula was closed and reperfusion of vessels recorded photographically. The occluded carotid artery was then opened and the complete reperfusion photographed. Another variation involved the same basic procedure, but in thii case the drainage cannula remained closed. The exposed vessels were again photographed during the arrest period without retrodrainage and again after reopening of the carotid. Between I and 2 min after arrest of cerebral blood flow, spontaneous respiration ceased. The animal was then supported ;&m;dBird respirator with Os+COs (95 : 5, v /v ) until spontaneous respiration After the experimental procedures, the instruments were removed from the animals, the cannulated carotid artery was reconstituted, and all wounds were closed. The cumulative period of ischaemia in each case was approximately 20 min, and none of the animals survived beyond 24 h postsurgically.
42
L. R. WOLIN, L. C. MASSOPUST, JR., R. J. WHITE AND N. TASLITZ
Results Clamping of the carotid and vertebral arteries with simultaneous opening of the cannula, which provided for retrodrainage of the circle of Willis, resulted in immediate cessation of detectable blood flow in the exposed pial vessels. This resulted in loss of all EEG activity within 15-q s, a brief drop in arterial blood pressure (20-40 mmHg systolic) followed by a rise of blood pressure to 20-30 mmHg above pre-occlusion levels, and the loss of spontaneous respiration within 1.5-2 min. The heart rate also changed after occlusion of all arteries. With occlusion and retrodrainage, heart rate increased approximately 10% within the first minute, continued to increase to about 40% above pre-occlusion levels by IO min, then gradually dropped and returned to near baseline level after reperfkion. The major increase in heart rate started immediately after the initiation of mechanical respiratory support. During occlusion without retrodrainage there was also an initial rise in heart rate. In this procedure respiratory support was not required and after several minutes the rate began to drop, returning to pre-occlusion levels or slightly below. The cortical perfusion via a single carotid artery is shown in Plate I. After the occlusion of the functional carotid
1
2
3
F3g. x. Excerpted electrocorticogran~ from the sensory cortex showing changes in activity before (I and 4) and immediatelyat&r (I and 5) occlusivearrest &brain arterial circulation. 3 and 6 show the degree of suppressionof EEG after occlusion. I, 2 and 3, Incomplete occlusivecirculatory arrest. 4, 5 and 6, Complete occlusive circulatory arrest. Note the electrocardiogram on isoelectric tracing (6). Calibration: vertical mark = IOO pV for 1-5, 20 PV for 6; horizontal mark = I a.
and opening of the retrodrain, the cortical vessels remained filled (Plate IB) but no pulsation or flow of blood was visible. Some pallor of the cortex was seen, but the change was not dramatic. When the drainage cannula was closed and the intact common carotid opened, immediate reperfusion of all vessels was noted (Plate IC). The second arrest procedure involved flushing the cerebral vasculature with approximately IO ml of 6% dextran (Plate 2A and B). While the drainage cannula remained open little perfusion was seen, but, upon closure of the drainage cannula, the blood flow slowly resumed (Plate 2C and D). Reopening of the occluded carotid artery resulted in immediate reperfusion of the vascular bed (Plate 3A). The third arrest procedure involved wash-out with dextran after occlusion, but with no retrodrainage provided (Plate 3B, C and D). Finally, the occluded carotid artery was again opened (Plate 4) and excellent reperfusion of the brain was noted. The contrast between total and subtotal arrest of cerebral blood flow on EEG activity is illustrated in Fig. I. The upper set of traces shows the depression and slowing of the EEG in subtotal arrest (drainage cammla closed) ; the EEG continues
CEREBRAL
ARREST AND REPERFUSION OF THE BRAIN
43
to show activity. In the lower set of traces, complete arrest with retrodrainage has been accomplished. The third segment (recorded at high sensitivity) reveals no EEG activity, but only small electrocardiogram artifact.
There are a number of interesting implications which have some bearing on problems of resuscitation in general and prevention of brain damage in particular. Most of the preparations, both actute and chronic, used in cerebral ischaemia studies have involved systemic anticoagulation. Hossman & Olsson (1970) used both heparinized and non-heparinized preparations and, although they reported longer delays in development of secondary suppression of neurophysiological activity in the heparinized animals, they nevertheless questioned the therapeutic efficacy of heparin. Crowell et al. (x955), however, caused circulatory arrest in dogs by producing cardiac fibrillation and respiratory arrest. They found emboli in the heart and lungs of animals after IO min of arrest. Animals given heparin showed higher survival rates than nonheparinized animals. Using monkeys, Smith, Ducker & Kempe (1969) also showed decreased incidence of infarction with up to 30 min of occlusion of the middle cerebral artery when the animals were pretreated with large doses of heparin. Ames et al. (1g68), in a study with rabbits, used both heparin premeditation and wash-out of blood with Ringer’s solution. They reported only slight protection from heparin and also presented evidence of narrowing of blood vessels, thus restricting reperfusion even after wash-out. It has been our experience that any procedure requiring cannulation of major vessels or temporary occlusion of major vessels invariably resulted in secondary complications in the absence of prior systemic anticoagulation. In the present experiment, the use of dextran wash-out of blood from the brain was employed only as a means of illustrating the effectiveness of arrest and reperfusion. Hossmann & Olsson (1970) used dextran, calf serum or Ringer’s solution for this purpose, and reported that this procedure prevented secondary complication in maintaining postischaemic blood flow. It should also be noted that they used solutions at 25°C in most cases and that the reduction in brain temperature which would occur under these conditions would in itself have a protective effect on the brain (White et al. 1969). Wolfson et al. (x964), Wolfson, Icoz & Luber (Ig65a) and Wolfson et al. (I g656) have also used cold saline wash-out of the brain as a means of inducing hypothermia for neurosurgical purposes, and the evidence suggests that this may be a potentially efficient procedure for protection of the brain against ischaemia. Actually two advantages are apparent, one being the protective effects of hypothermia and the second the clearing of blood from the capillary system, thus reducing the possibility of clotting and also washing out metabolic products [lactate etc.). This would, of course, be particularly advantageous when anticoagulation measures have not, or cannot, be employed. The use of either anticoagulation or wash-out procedures appears to facilitate the re-establishment of rapid, effective perfusion of the brain after ischaemia and appears to reduce the incidence of secondary circulatory complications. We thus see that occlusion of the carotid and vertebral arteries is insufficient to stop all blood flow to the brain in the monkey. Provision of a retrodrainage system directly from the circle of Willis does effectively eliminate cortical blood flow (Wolin
‘$4
L. R. WOLIN,
L. C. MASSOPUST, JR., R. J. WHITE AND N. TASLITZ
After repeated arrest of cerebral circulation involving both stagnation of blood and wash-out of the cerebral vasculature with de&ran, immediate and effective reperfitsion of the brain occurs. In conclusion, it has been repeatedly demonstrated that recovery of brain function is possible after extended periods of ischaemia. Several studies have also demonstrated long-term survival of primates after cerebral ischaemia, often with little or no demonstrable neurological or behavioural deficits. Rapid and effective reperfusion of the brain after ischaemia appears critical for survival and reduction or elimination of brain damage. Use of anticoagulation, vascular wash-out or hypothermia, or any combination of these procedures, appears to be advantageous in facilitating recovery from ischaemic insult to the brain.
et al. Ig7Ia).
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