Retrograde cerebral perfusion during profound hypothermia and circulatory arrest in pigs

A reappraisal of retrograde cerebral perfusion

Brain protection during aortic arch surgery by perfusing cold oxygenated blood into the superior vena cava was first reported by Lemole et al. In 1990 Ueda and associates first described the routine use of continuous retrograde cerebral perfusion (RCP) in thoracic aortic surgery for the purpose of cerebral protection during the interval of obligatory interruption of anterograde cerebral flow. The beneficial effects of RCP may be its ability to sustain brain hypothermia during hypothermic circulatory arrest (HCA) and removal of embolic material from the arterial circulation of the brain. RCP can offer effective brain protection during HCA for about 40 to 60 minutes. Animal experiments revealed that RCP provided inadequate cerebral perfusion and that neurological recovery was improved with selective antegrade cerebral perfusion (ACP), however, both RCP and ACP provide comparable clinical outcomes regarding both the mortality and stroke rates by risk-adjusted and case-matched comparative study. RCP still remains a valuable adjunct for brain protection during aortic arch repair in particular pathologies and patients.

Ascending and Transverse Aortic Arch Repair

Background— The benefit of retrograde cerebral perfusion (RCP) with profound hypothermic circulatory arrest has been subject to much debate. We examined our experience with ascending and transverse arch repairs to determine the impact of retrograde cerebral perfusion on stroke and mortality.

Methods and Results— Between August 1991 and June 2007, we performed 1107 repairs of the ascending and transverse aortic arch. RCP was used in 82% of cases (907 of 1107). Sixty-two percent were men (682 of 1107); median age was 64 years (range, 16 to 93 years). Perioperative variables were evaluated using univariate and multivariable analysis for mortality and stroke. Thiry-day mortality was 10.4% (115 of 1107). Stroke occurred in 2.8% (31 of 1107) of patients. Univariate risk factors for mortality were increasing age ( P <0.0001), history of coronary artery disease ( P =0.02), previous coronary artery bypass ( P =0.02), emergency status ( P <0.0001), acute dissection ( P =0.02), rupture ( P =0.0001), preoperative glomerular filtration rate, bypass time ( P <0.0001), crossclamp time ( P <0.007), RCP time ( P <0.0001), and packed red blood cell transfusions ( P =0.0001). Univariate risk factors for stroke included emergency status ( P <0.02), cerebrovascular disease ( P <0.02), and crossclamp time ( P <0.04). Independent risk factors for mortality were glomerular filtration rate <90 mL/min ( P =0.0004), emergency status ( P =0.006), rupture ( P =0.004), cardiopulmonary bypass time >120 minutes ( P <0.04), and packed red blood cell transfusions ( P =0.0002). Risk factors for stroke were emergency status ( P <0.009) and hypertension ( P <0.05). RCP was protective against mortality and stroke.

Conclusions— The use of RCP with profound hypothermic circulatory arrest was associated with a reduction in mortality and stroke. The use of RCP remains warranted during repairs of the ascending and transverse aortic arch.

Rapid Brain Cooling by Hypothermic Retrograde Jugular Vein Flush

BACKGROUND

Although whole-body hypothermia recently has been reported effective in improving the neurologic outcome after cardiac arrest, it is contraindicated in the management of trauma patients with hemorrhagic shock. To provide selective brain cooling in this situation, the authors speculated about the feasibility of hypothermic retrograde jugular vein flush (HRJVF). This preliminary study was conducted to test the effectiveness of brain cooling after HRJVF in rats without hemorrhagic shock.

METHODS

After jugular vein cannulation with cranial direction, Sprague-Dawley rats were randomized into a normal control group, a group that underwent flush with cold saline at 4 degrees C, or a group that underwent flush with saline at a room temperature of 24 degrees C. A Servo-controlled heat lamp was applied for all the rats to keep their rectal temperature at 37 +/- 0.5 degrees C. Their brain temperature and cerebral blood flow were checked.

RESULTS

Within the 10-minute period of cold saline flush (1.7 mL/100 g), brain temperature was immediately decreased, and this cooling effect could be maintained for at least 20 minutes. Cerebral blood flow was significantly increased after HRJVF, then returned gradually to the baseline as brain temperature elevated.

CONCLUSIONS

This study successfully demonstrated a significant cooling effect in rat brain by HRJVF. For preservation of brain function, HRJVF may be useful in resuscitation for trauma patients with hemorrhagic shock after further studies on animals with shock.

Hypothermic retrograde jugular perfusion reduces brain damage in rats with heatstroke

OBJECTIVE

To determine whether direct retrograde ice saline infusion in the jugular vein without cardiopulmonary bypass protects rat brains after heatstroke.

DESIGN

Randomized, controlled, prospective study.

SETTING

University physiology research laboratory.

SUBJECTS

Sprague-Dawley rats (270-320 g, males).

INTERVENTIONS

Rats were randomized into three groups and given a) no resuscitation after onset of heat stroke (HS, n = 8); b) ice saline infusion in the femoral vein after onset of heat stroke (HS + F, n = 8); or c) retrograde ice saline infusion in the external jugular vein after onset of heat stroke (HS + J, n = 8). Rats were exposed to an ambient temperature of 43 degrees C after vessel cannulation. Their mean arterial pressure, heart rate, colonic temperature, and brain temperature were continuously recorded. Survival time and brain pathology were checked.

MEASUREMENTS AND MAIN RESULTS

Although colonic temperature decreased 0.8-1.0 degrees C 15 mins after heatstroke in all groups, no treatment-related changes in colonic temperature were noted in any group. However, significant changes were observed in brain temperature. Fifteen minutes after heatstroke, brain temperature was 37.6 +/- 0.4 degrees C, 36.1 +/- 0.4 degrees C, and 33.6 +/- 0.8 degrees C in HS, HS + F, and HS + J, respectively. Survival time was 16.1 +/- 2.1, 33.0 +/- 3.8, and >120 mins in these groups, respectively. Neuron damage score was significantly lower in HS + J and without lateralization.

CONCLUSIONS

We successfully demonstrated that direct retrograde hypothermic perfusion via the jugular vein without cardiopulmonary bypass protected the brain after heat stroke. This technique cooled the brain but did not significantly interfere with body temperature.

Determination of cerebral blood flow dynamics during retrograde cerebral perfusion using power M-mode transcranial Doppler

BACKGROUND

Retrograde cerebral perfusion (RCP) during profound hypothermic circulatory arrest has been used as an adjunct for cerebral protection for repairs of the ascending and transverse aortic arch. Transcranial Doppler ultrasound has been used to monitor cerebral blood flow during RCP with varying success. The purpose of this study was to characterize cerebral blood flow dynamics during RCP using a new mode of monitoring known as transcranial power motion-mode (M-mode) Doppler ultrasound.

METHODS

Data on pump-flow characteristics and patient outcomes were collected prospectively for patients undergoing ascending and transverse aortic arch repair. Retrograde cerebral perfusion during profound hypothermic circulatory arrest was used for all operations. Intraoperative cerebral blood flow dynamics were monitored and recorded using transcranial power M-mode Doppler ultrasound.

RESULTS

Between August 2001 and March 2002, we used transcranial power M-mode Doppler ultrasound monitoring for 40 ascending and transverse aortic arch repairs during RCP. Mean RCP time was 32.2 +/- 13.8 minutes. Mean RCP pump flow and RCP peak pressure for identification of cerebral blood flow were 0.66 +/- 0.11 L/min and 31.8 +/- 9.7 mm Hg, respectively. Retrograde cerebral blood flow during RCP was detected in 97.5% of cases (39 of 40 patients) with a mean transcranial power M-mode Doppler ultrasound flow velocity of 15.5 +/- 12.3 cm/s. In the study group, 30-day mortality was 10.0% (4 of 40 patients). The incidence of stroke was 7.6% (3 of 40 patients); the incidence of temporary neurologic deficit was 35.0% (14 of 40 patients).

CONCLUSIONS

Transcranial power M-mode Doppler ultrasound consistently demonstrated retrograde middle cerebral artery blood flow during RCP. Transcranial power M-mode Doppler ultrasound can provide optimal RCP with individualized settings of pump flow.

Cerebral metabolism of nitric oxide during retrograde cerebral perfusion

The aim of this study was to determine whether alpha- or pH-stat protects the brain during deep hypothermic retrograde cerebral perfusion. Fifteen anesthetized dogs on cardiopulmonary bypass were cooled to 18 degrees C under alpha-stat and underwent retrograde cerebral perfusion for 90 minutes under alpha-stat or pH-stat, or underwent antegrade cardiopulmonary bypass under alpha-stat as the control. Cerebral blood flow of the cortex was monitored and serial analyses of blood gases and total nitric oxide oxidation products made. Cerebral blood flow and cerebral metabolic rate for oxygen were significantly higher and plasma levels of nitric oxide oxidation products in the outflow from the brain were significantly lower in retrograde cerebral perfusion under pH-stat than under alpha-stat. This study shows that reduced levels of nitric oxide oxidation products may protect against neuronal damage induced by nitric oxide and that increased cerebral blood flow under pH-stat may lead to a reduction of nitric oxide oxidation products. Under retrograde cerebral perfusion, pH-stat is thus better than alpha-stat for protecting the brain.

Neurological Complications of Aortic Surgery

Surgery of the aortic arch involves an inherently high risk of neurological complications. A number of factors have been identified which may predispose the patient to brain injury, and various techniques employed in an attempt to counteract these are outlined. In particular the vulnerability of the brain to ischemia has led to the development of three adjunctive cerebral protective techniques, hypothermic circulatory arrest, retrograde cerebral perfusion and selective antegrade cerebral perfusion, all based upon brain cooling and metabolic inhibition. The relative merits and disadvantages of these techniques are therefore discussed. Finally, pharmacologic adjuncts and potential future developments in aortic arch surgery are discussed.

Retrograde cerebral perfusion as a method of neuroprotection during thoracic aortic surgery

Retrograde cerebral perfusion is commonly used as an adjunct to hypothermic circulatory arrest to enhance cerebral protection during thoracic aortic surgery. This review summarizes a large number of studies that demonstrate a spectrum of beneficial, neutral, and detrimental effects of retrograde cerebral perfusion in humans and experimental animal models. It remains unclear whether retrograde cerebral perfusion provides effective cerebral perfusion, metabolic support, washout of embolic material, and improved neurological and neuropsychological outcome.

Retrograde cerebral perfusion provides negligible flow through brain capillaries in the pig

OBJECTIVES

Although retrograde cerebral perfusion is being used clinically during aortic arch surgery, whether retrograde flow perfuses the brain effectively is still uncertain.

METHODS

Fourteen pigs were cooled to 20 degrees C with cardiopulmonary bypass and perfused retrogradely via the superior vena cava for 30 minutes: 7 underwent standard retrograde cerebral perfusion and 7 underwent retrograde perfusion with occlusion of the inferior vena cava. Antegrade and retrograde cerebral blood flow were calculated by quantitating fluorescent microspheres trapped in brain tissue after the animals were put to death; microspheres returning to the aortic arch, the inferior vena cava, and the descending aorta were also analyzed during retrograde cerebral perfusion.

RESULTS

Antegrade cerebral blood flow was 16 +/- 7.7 mL. min(-1). 100 g(-1) before retrograde cerebral perfusion and 22 +/- 6.3 mL. min(-1). 100 g(-1) before perfusion with caval occlusion (P =.14). During retrograde perfusion, calculations based on the number of microspheres trapped in the brain showed negligible flows (0.02 +/- 0.02 mL. min(-1). 100 g(-1) with retrograde cerebral perfusion and 0.04 +/- 0.02 mL. min(-1). 100 g(-1) with perfusion with caval occlusion; P =.09): only 0.01% and 0.02% of superior vena caval inflow, respectively. Less than 13% of retrograde superior vena caval inflow blood returned to the aortic arch with either technique. During retrograde cerebral perfusion, more than 90% of superior vena caval input was shunted to the inferior vena cava and was then recirculated, as indicated by rapid development of an equilibrium in microspheres between the superior and inferior venae cavae. With retrograde perfusion and inferior vena caval occlusion, less than 12% of inflow returned to the descending aorta and only 0.01% of microspheres.

CONCLUSIONS

The paucity of microspheres trapped within the brain indicates that retrograde cerebral perfusion, either alone or combined with inferior vena caval occlusion, does not provide sufficient cerebral capillary perfusion to confer any metabolic benefit. The slightly improved outcome previously reported with retrograde cerebral perfusion during prolonged circulatory arrest in this model may be a consequence of enhanced cooling resulting from perfusion of nonbrain capillaries and from venoarterial and venovenous shunting.

Results of aortic arch repair with hypothermic circulatory arrest and retrograde cerebral perfusion

BACKGROUND

Repair of aortic arch pathology is reliably performed with hypothermic circulatory arrest, but the best method of brain protection is controversial.

METHODS

We reviewed a consecutive series of 67 patients who had aortic arch repair with hypothermic circulatory arrest. Retrograde perfusion of arterial blood into the superior vena cava (SVC) during systemic arrest was used in 87%. Average age was 65 years. Acute dissection was present in 25%. Average circulatory arrest time was 37 minutes, and average temperature 17.7 degrees C.

RESULTS

Hospital mortality was 1.5%. Strokes occurred in 4.5%. Temporary neurological dysfunction occurred in 16%. Multivariate logistic regression analysis showed that acute dissection was the only independent predictor of the combined risk of stroke and temporary neurological dysfunction (odds ratio 8.5). Duration of circulatory arrest and patient age were not risk factors for adverse neurological outcome.

CONCLUSION

Continuous arterial perfusion of the SVC during hypothermic circulatory arrest provides excellent cerebral protection for aortic arch repair. Acute dissection is an independent risk factor for adverse neurological outcome. Arrest time is not a predictor of neurological dysfunction.

Comparison of two sites of inflow pressure measurement during retrograde cerebral perfusion

OBJECTIVE

To determine whether internal jugular venous valves influence inflow pressure during retrograde cerebral perfusion.

DESIGN

Prospective study.

SETTING

Community hospital, university setting, single institution.

PARTICIPANTS

Ten patients undergoing reconstructive aortic arch surgery with profound hypothermic circulatory arrest.

INTERVENTIONS

During retrograde cerebral perfusion, inflow pressure was continuously measured at 2 separate sites relative to the left internal jugular venous valve (ie, superior vena cava inflow catheter [infravalvular pressure] and rostral left internal jugular vein [supravalvular pressure]).

MEASUREMENTS AND MAIN RESULTS

Infravalvular pressure of 29.8 +/- 3.5 mmHg and supravalvular pressure of 22.7 +/- 0.8 mmHg were significantly different (mean difference, 7.1 +/- 3.6 mmHg; p = 0.041). In 8 patients, the pressure difference was <6 mmHg; whereas in 2 patients, the pressure difference was >20 mmHg. Bland and Altman analysis revealed 95% limits of agreement on mean bias of -12.9 to 27.8 mmHg.

CONCLUSION

Internal jugular venous valves can obstruct retrograde cerebral perfusion inflow, manifest by an inflow pressure difference between the superior vena cava and internal jugular vein. In the presence of competent internal jugular venous valves, measurement of inflow pressure in the superior vena cava may be an inaccurate estimate of actual cerebral perfusion pressure. Internal jugular vein pressure should be monitored to avoid inadvertent cerebral hypoperfusion.

Retrograde perfusion of the spinal cord during aortic crossclamping: initial observations in the swine model

BACKGROUND

Retrograde perfusion has emerged as a useful technique for the preservation of the heart and brain when arterial circulation is interrupted. Herein, this study was designed to test the hypothesis that retrograde perfusion of the azygos vein is sufficient to maintain viability of the spinal cord during aortic occlusion in the swine model.

METHODS

Female swine, 17 to 22 kg, underwent left thoracotomy, creation of a shunt between the aortic arch and the azygos vein, and aortic crossclamping for 60 minutes: the shunt was open in the retrograde perfusion group (n = 5) and closed in the control group (n = 4). The animals were evaluated for neurologic function for 8 days and killed. Spinal cords were processed for histologic examination. Additional animals underwent left thoracotomy and injection of a casting solution in the azygos vein (n = 2), left thoracotomy and angiography of the azygos vein (n = 2), and a compartmentalization procedure to separate the azygos vein from the caval system followed by angiography (n = 2).

RESULTS

Differences in the neurologic (2-sample t test, P =.11) and histologic (2-sample t test, P =.65) scores of retrograde perfusion and control groups were likely due to chance. Casting and angiography groups showed extensive collaterals between azygos and caval systems, only partially interrupted by compartmentalization.

CONCLUSIONS

Retrograde perfusion does not protect the spinal cord from ischemic injury. The collateral network between the azygos and caval systems prevents the oxygenated blood from reaching the cord. Surgical separation between the 2 systems was only partially successful in this study.

Distribution of cerebral flow using retrograde versus antegrade cerebral perfusion

BACKGROUND

This study compared flow to the brain with retrograde and antegrade cerebral perfusion during circulatory arrest.

METHODS

Twenty-four rabbits were injected with 5 mCi of technetium-99 macroaggregated albumin, a tracer trapped in the capillaries. Group I (n = 6) were maintained normothermic, and the tracer was injected into the ascending aorta. Group II (n = 6) were maintained normothermic, and underwent cannulation of the superior vena cava (SVC), exsanguination through the aorta, and injection of the tracer into the SVC, which was proximally occluded. In group III (n = 6), the animal was cooled to 25 degrees C. The animal was exsanguinated through the aorta and tracer was injected into the ascending aorta. In group IV (n = 6), animals were cooled to 25 degrees C. The animal was exsanguinated through the ascending aorta and tracer was injected into the SVC. Three animals (group V) were exsanguinated through the ascending aorta and a retrograde venogram of the SVC was performed. Scintigraphy of groups I to IV was carried out on a digital gamma camera. Brain trapping of tracer was graded from 0 to 5, with 0 being no tracer in the brain and 5 being dominant tracer trapping in the brain.

RESULTS

Tracer trapping in the brain showed group I, 3.67+/-0.82; group II, 0; group III, 4.67+/-0.41; group IV, 0.17+/-0.41 (p<0.0001). Retrograde venogram of the SVC showed flow into the cerebral veins.

CONCLUSIONS

Retrograde flow through the SVC reaches the cerebral venous system. Flow arriving in retrograde fashion does not go through the capillary system.

Effect of lidocaine on improving cerebral protection provided by retrograde cerebral perfusion: a neuropathologic study

OBJECTIVE

To determine whether lidocaine can improve the neuropathologic results in canine brains after retrograde cerebral perfusion (RCP).

DESIGN

Randomized, blinded, experimental study.

SETTING

University animal laboratory.

PARTICIPANTS

Mongrel dogs.

INTERVENTIONS

Fourteen mongrel dogs were placed on 120 minutes of hypothermic (20 degrees C) RCP. Following the RPC, they then resumed cardiopulmonary bypass and rewarming for 60 minutes. In the lidocaine group (n = 8), lidocaine was administered continuously; in the control group (n = 6), normal saline was administered. Cerebral perfusion fixation was performed at the end of the experiment.

MEASUREMENTS AND MAIN RESULTS

The number of ischemic cells in 200 neurons was counted in the parietal cortex, CA1 sector of the hippocampus, CA3 sector of the hippocampus, ventral posterolateral nucleus of the thalamus, and Purkinje cells of the cerebellar cortex. Those in the parietal cortex, CA1 sector of the hippocampus, and ventral posterolateral nucleus of the thalamus were significantly less in the lidocaine group than in the control group (25.8+/-17.3 v 53.7+/-12.0; p < 0.01; 17.0+/-8.5 v 54.7+/-22.1; p < 0.01; and 16.9+/-17.8 v 49.7+/-28.4; p < 0.05, respectively). The total number of ischemic cells in the five examined regions was also significantly less in the lidocaine group than in the control group (89.5+/-19.4 v 219.5+/-45.5; p < 0.01).

CONCLUSION

Continuous lidocaine significantly alleviated the ischemic neuropathologic injury after RCP and thus possibly improved cerebral protection.

[An experimental study on the occurrence of brain edema after retrograde cerebral perfusion]

To assess the safety of retrograde cerebral perfusion, the occurrence of brain edema after this procedure was investigated. Twenty-eight adult mongrel dogs were divided into three groups that underwent the following treatments: antegrade perfusion (group 1, n = 9); retrograde perfusion alone (group 2, n = 11); or tetrograde perfusion with drugs (manuitol, thiopental sodium, and methylprednisolone; group 3, n = 8). After 90 minutes of cerebral perfusion at 20 degrees C of the pharyngeal temperature, evans blue (EB) was administered to check for disruptions of the blood-brain-barrier (BBB) and brain tissue water content was measured. Intracranial pressure after cerebral perfusion was markedly higher in group 2 than in group 1 (26.4 +/- 9.4 vs. 11.2 +/- 3.6 mmHg), and brain tissue water content was also significantly higher in group 2 than in group 1 (80.7 +/- 2.0 vs. 77.8 +/- 0.9%). These data suggested that brain edema was more prominent after retrograde perfusion than after antegrade perfusion. The extent of EB to brain tissue was greater in group 2 than in group 1 (169.8 +/- 97.7 vs. 54.7 +/- 31.5 micrograms/dl). The BBB was highly disrupted in group 2 and vasogenic edema appeared after retrograde cerebral perfusion. Maximum intracranial pressure, brain tissue water content and EB concentration were significantly lower in group 3 than in group 2, and did not differ significantly between group 3 and 1. Administration of pharmacologic agents suppressed edema formation and extravasation of EB. We conclude that 90 minutes of retrograde cerebral perfusion at 20 degrees C of the pharyngeal temperature causes brain edema and disrupts the BBB in a manner different from that associated with antegrade perfusion. Mannitol, thiopental sodium, and methylprednisolone prevent these phenomena, indicating that pharmacologic intervention may improve the safety of retrograde cerebral perfusion.

Techniques for retrograde cerebral perfusion in the treatment of aortic lesions via left thoracotomy

Retrograde cerebral perfusion under deep hypothermic circulatory arrest is a simple and useful adjunct in aortic surgery and is performed by many surgeons in the treatment of aortic arch pathology. In recent years, this technique has been recommended in the surgery of distal arch and proximal descending aortic lesions through a left thoracotomy inclusion. The aim of the technique is to increase the right atrial pressure for retrograde cerebral perfusion. After cooling using femorofemoral bypass, circulatory arrest is initiated. The right atrial pressure is increased to 20 mmHg, and retrograde cerebral circulation results. In this article, five patients with distal aortic arch and proximal descending thoracic aortic lesions who were operated on by using this technique were evaluated. It is suggested that this technique can be used with a lateral thoracotomy approach that is suitable for procedures on a distal aortic arch and proximal descending aorta.

Impact of retrograde cerebral perfusion on ascending aortic and arch aneurysm repair

PURPOSE

The effect of retrograde cerebral perfusion on the incidence of stroke and death among patients undergoing repair of aneurysms of the ascending aorta and transverse arch was determined.

MATERIALS AND METHODS

Between January 1991 and March 1995, 161 patients were operated on for aneurysms of the ascending aorta and transverse arch. Thirty-three of the patients (20%) had an aneurysm of the ascending aorta only and 128 (80%) had aneurysms of both the ascending aorta and the transverse arch. All the patients underwent cardiopulmonary bypass, profound hypothermia, and circulatory arrest, and 120 (74%) also underwent retrograde cerebral perfusion. Median pump time was 143 minutes (range, 21 to 461 minutes). Median circulatory arrest time was 42 minutes (range, 8 to 111 minutes), and median myocardial ischemic time was 71 minutes (range, 14 to 306 minutes).

RESULTS

The overall 30-day mortality rate was 6% (9 patients) and the incidence of stroke was 4% (7 patients). The use of retrograde cerebral perfusion demonstrated a protective effect against stroke (3 of 120 patients, or 3%) compared with no retrograde cerebral perfusion (4 of 41 patients, or 9%; odds ratio, 0.24; confidence interval, 0.06 to 0.99; p < 0.049). This was most significant in patients more than 70 years of age; none of the 36 elderly patients who received retrograde cerebral perfusion had a stroke, compared with 3 of the 13 (23%) who did not (p < 0.003). Only pump time was associated with an increased risk of stroke (odds ratio, 1.01; 95% confidence interval, 1.00 to 1.02; p < 0.005). Pump time also was associated with increased mortality (odds ratio, 1.01; 95% confidence interval, 1.00 to 1.02; p < 0.008).

CONCLUSION

Retrograde cerebral perfusion decreased the incidence of stroke in patients undergoing repair of aneurysms of the ascending aorta and transverse arch.