Cold retrograde cerebral perfusion improves cerebral protection during moderate hypothermic circulatory arrest: A long-term study in a porcine model

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.

Laparoscopic inferior vena cava and right atrial thrombectomy utilizing deep hypothermic circulatory arrest

BACKGROUND AND PURPOSE

Surgery for renal cancer associated with a level III or IV tumor thrombus often involves cardiopulmonary bypass, deep hypothermia, and exploration of the right atrium and inferior vena cava (IVC). This major open operation necessitates a large median sternotomy incision and a midline abdominal or chevron incision. Herein, we investigate the feasibility of purely laparoscopic IVC and right atrial thrombectomy utilizing deep hypothermic circulatory arrest.

MATERIALS AND METHODS

In six male calves weighing 70 to 80 kg, the right common carotid artery and right internal jugular vein were cannulated for subsequent cardiopulmonary bypass. One laparoscopic team performed right radical nephrectomy and complete mobilization of the intra-abdominal IVC by a four-port approach. Simultaneously, a second laparoscopic team obtained three-port thoracoscopic access to incise the pericardium and expose the right atrium. In sequence, cardiopulmonary bypass, complete exsanguination, cardiac arrest, and core hypothermia of 18 degrees C were achieved. A coagulum thrombus was created by needle injection into the IVC. Combined laparoscopic and thoracoscopic incision, exploration, and thrombectomy of the IVC and the right atrium were then performed in a bloodless field. An angioscope was inserted inside the heart and the IVC to confirm complete thrombus clearance visually. The IVC and right atrium were then laparoscopically suture repaired, cardiopulmonary bypass was reestablished, and the animal was gradually rewarmed. Once sinus rhythm was reestablished at normal body temperature, the animal was weaned off the pump.

RESULTS

The mean total operative time was 494.5 minutes (range 355-705 minutes). The mean time needed to lower the core temperature was 63.5 minutes (range 50-120 minutes), and the mean time required to rewarm the animal was 101.8 minutes (range 70-130 minutes). The mean blood volume drained into the pump was 2633.3 mL (range 1400-3200 mL), and the mean estimated blood loss was 350 mL (range 200-750 mL). Reestablishment of sinus cardiac rhythm and weaning off the pump was successful in all animals prior to acute euthanasia.

CONCLUSIONS

Laparoscopic radical nephrectomy with thrombectomy for level III or IV tumor thrombi utilizing deep hypothermic circulatory arrest is feasible in the calf model using minimally invasive techniques exclusively. The procedure is technically complex and requires the combined efforts of expert urologic and cardiac operative teams. Survival studies are planned.

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.

Cerebral Protection During Surgery of the Aortic Arch

The most significant challenge in surgical repair of the aortic arch (transverse thoracic aorta) is to protect the brain from ischemic injury. During the portion of the procedure when the brachiocephalic vessels are at tached to a graft, there is an obligatory interruption in the normal path of circulation to the brain. Various strategies are used to overcome the potential for brain injury during discontinuity between the aorta and the cerebral circulation. These include deep hypothermic circulatory arrest, retrograde cerebral perfusion, and selective anterograde cerebral perfusion. Pharmaco logic adjuncts to these procedures are also used to further enhance brain protection. This review ad dresses the relative merits of these techniques as means of cerebral protection.

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.

Intermittent retrograde cerebral perfusion during prolonged period of hypothermic circulatory arrest: a study in a chronic porcine model

Previous studies have shown that although retrograde cerebral perfusion (RCP) improves cerebral outcome during hypothermic circulatory arrest (HCA), RCP exposes the brain to subsequent edema. In this study, we have compared intermittent RCP (I-RCP) with continuous RCP (C-RCP) and HCA alone to determine whether the rate of fluid sequestration can be decreased without losing the beneficial effects of RCP. Eighteen pigs were randomly assigned to undergo 75 min of I-RCP, C-RCP or HCA at 20 degrees C. Hemodynamic and metabolic measurements were carried out for upto 20 h. Behavioral assessments were examined until day 7, when histopathologic analysis of the brain was performed. The median amount of fluid sequestered was 145 ml after C-RCP and -50 ml after I-RCP (p = 0.04). The mean brain weight of the animals that died within the first postoperative day was significantly higher than that in electively sacrificed animals in the C-RCP group (p = 0.04). These data suggest that if RCP is implemented intermittently, the rate of cerebral edema can be decreased, without compromising the benefits of this strategy.

Leukocyte filtration improves brain protection after a prolonged period of hypothermic circulatory arrest: A study in a chronic porcine model

BACKGROUND

Ischemic cerebral injury follows a well-attested sequence of events, including 3 phases: depolarization, biochemical cascade, and reperfusion injury. Leukocyte infiltration and cytokine-mediated inflammatory reaction are known to play a pivotal role in the reperfusion phase. These events exacerbate the brain injury by impairing the normal microvascular perfusion and through the release of cytotoxic enzymes. The aim of the present study was to determine whether a leukocyte-depleting filter (LeukoGuard LG6, Pall Biomedical, Portsmouth, United Kingdom) could improve the cerebral outcome after hypothermic circulatory arrest.

METHODS

Twenty pigs (23-30 kg) were randomly assigned to undergo cardiopulmonary bypass with or without a leukocyte-depleting filter before and after a 75-minute period of hypothermic circulatory arrest at 20 degrees C. Electroencephalographic recovery, S-100beta protein levels, and cytokine levels (interleukin 1beta, interleukin 8, and tumor necrosis factor alpha) were recorded up to the first postoperative day. Postoperatively, all animals were evaluated daily until death or until electively being put to death on day 7 by using a quantitative behavioral score. A postmortem histologic analysis of the brain was carried out on all animals.

RESULTS

The rate of mortality was 2 of 10 in the leukocyte-depletion group and 5 of 10 in control animals. The risk for early death in control animals was 2.5 (95% confidence interval, 0.63-10.0) times higher than that of the leukocyte-depleted animals. The median behavioral score at day 7 was higher in the leukocyte-depletion group (8.5 vs 3.5; P =.04). The median of total histopathologic score was 8.5 in the leukocyte-depletion group and 15.5 in the control group (P =.005).

CONCLUSION

A leukocyte-depleting filter improves brain protection after a prolonged period of hypothermic circulatory arrest.

Lamotrigine improves cerebral outcome after hypothermic circulatory arrest: a study in a chronic porcine model

BACKGROUND

Glutamate excitotoxicity has an important role in the development of brain injury after prolonged hypothermic circulatory arrest. The goal of the present studies was to determine the potential efficacy of lamotrigine, an Na(+) channel blocker, to mitigate cerebral injury after hypothermic circulatory arrest.

METHODS

Sixteen pigs (21-27 kg) were randomly assigned to receive lamotrigine (20 mg/kg) or placebo in a blinded fashion before a 75-minute period of hypothermic circulatory arrest (20 degrees C). Hemodynamic, electroencephalographic, and metabolic monitoring were carried out. S-100beta protein was determined up to the first postoperative morning. Daily behavioral assessment was performed until the animal died or was put to death on day 7. Histologic analysis of the brain was carried out in all animals.

RESULTS

Complete behavioral recovery was seen in 5 of 8 (63%) animals after lamotrigine administration, compared with 1 of 8 (13%) in the placebo group (P =.02). Among the animals that survived for 7 days, the median behavioral score was higher in the lamotrigine group (8 vs 7, P =.02). The medians of recovered electroencephalographic bursts in the lamotrigine group were higher than those in the placebo group 4 1/2 hours after the start of rewarming (P =.01). The median S-100beta level was lower in the lamotrigine group (0.01 microg/L) than in placebo controls (0.1 microg/L) 20 hours after the start of rewarming (P =.01). The median of total histopathologic score was 5.5 in the lamotrigine group and 7.5 in the placebo group (P =.06).

CONCLUSIONS

The present data suggest that lamotrigine improves neurologic outcome after a prolonged period of hypothermic circulatory arrest.

Central Nervous System Complications in Cardiac Surgery: Retrograde Cerebral Perfusion, Pressure, Pulsatility, Temperature, and pH Management During Cardiopulmonary Bypass

Currently, clinical management strategies during cardio pulmonary bypass (CPB) are undergoing profound changes. Renewed interest in normothermic versus hypothermic perfusion during CPB has resulted in appar ently contradictory results regarding patient outcomes. Much effort has been devoted to defining physiological responses of the brain to various alterations during CPB (eg, pH strategy, normothermia versus hypothermia, pulsatile or nonpulsatile perfusion, use of arterial line filtration, circulatory arrest, retrograde cerebral perfu sion). In addition, prospective studies are examining the impact of diverse strategies on neuropsychological and neurological outcomes after CPB, to define optimal management techniques.

Is maintained cranial hypothermia the only factor leading to improved outcome after retrograde cerebral perfusion? An experimental study with a chronic porcine model

BACKGROUND

Previous studies have shown that retrograde cerebral perfusion can improve neurologic outcome after prolonged hypothermic circulatory arrest. Here we have compared two temperatures of retrograde cerebral perfusion (15 degrees C and 25 degrees C) with hypothermic circulatory arrest at systemic hypothermia of 25 degrees C to clarify whether the possible benefit of retrograde cerebral perfusion may only be due to improved cooling effect.

METHODS

Eighteen pigs (23-27 kg) were randomly assigned to undergo 15 degrees C retrograde cerebral perfusion at systemic hypothermia of 25 degrees C, 25 degrees C retrograde cerebral perfusion at 25 degrees C systemic hypothermia, or hypothermic circulatory arrest at 25 degrees C for 40 minutes. Flow was adjusted to maintain superior vena cava pressure at 20 mm Hg during retrograde cerebral perfusion. Hemodynamic, electrophysiologic, metabolic, and temperature monitoring were performed until 4 hours after the start of rewarming. Daily behavioral assessment was done until death or until the animals were killed on day 7. Histopathologic analysis of the brain was carried out on all animals.

RESULTS

Epidural temperatures were lower in the 15 degrees C retrograde cerebral perfusion group during the intervention (P <.05). In the 15 degrees C retrograde cerebral perfusion group, 4 (67%) of 6 animals survived for 7 days compared with 3 (50%) of 6 in both the 25 degrees C retrograde cerebral perfusion and hypothermic circulatory arrest groups. The median total histopathologic score was 5 in the 15 degrees C retrograde cerebral perfusion group and 7 in the 25 degrees C retrograde cerebral perfusion group (P =.04).

CONCLUSIONS

These findings suggest that enhanced cranial hypothermia is the major beneficial factor of retrograde cerebral perfusion when careful attention is paid to its implementation.