Antegrade selective cerebral perfusion in thoracic aorta surgery: safety of moderate hypothermia

Advantages of upper brachial artery cannulation in aortic surgery

BACKGROUND

The best method of cerebral protection during aortic arch surgery remains controversial. However, antegrade cerebral perfusion seems to be the most favorable because of better neurological outcomes. Although there have been many studies on antegrade cerebral perfusion via upper brachial cannulation, there is a lack of studies focusing particularly on local complications, with objective findings. The aim of this study was to investigate the local neurological and vascular complications following upper brachial cannulation.

METHODS AND RESULTS

This study included 44 patients who underwent procedures on the ascending aorta, aortic arch, or descending aorta with upper brachial artery cannulation for cardiopulmonary bypass at OSM Ortadogu Hospital and Cankaya Hospital between January 2009 and April 2012. The mean age of the 32 (72.7%) men and 12 (27.3%) women was 55.2 ± 12.3 years. Doppler analysis of the upper brachial artery was performed in 26 (59%) patients. Mean follow-up time for Doppler analysis was 5.7 ± 2 months. The mean antegrade cerebral perfusion time was 35 ± 16.1 min. The mean degree of hypothermia was 25.1 ± 2.0 . Hospital death occurred in 4 (9.1%) patients, and 2 (4.5%) suffered local neurologic complications. Electromyelography analysis was carried out in the 2 patients who suffered local neurologic symptoms.

CONCLUSIONS

Brachial artery cannulation is technically simple and less time consuming, thus suitable even for emergency cases. With an acceptable risk of local complications, we recommend routine use of upper brachial cannulation for antegrade cerebral perfusion.

Modern temperature management in aortic arch surgery: the dilemma of moderate hypothermia

Arch surgery is undoubtedly among the most technically and strategically challenging endeavours in aortic surgery, requiring thorough understanding not only of cardiovascular physiology, but also in particular, of neurophysiology (cerebral and spinal cord), and is still associated with significant mortality and morbidity. In the late 1980s, when deep hypothermic circulatory arrest (HCA) had gained widespread acceptance as the standard approach for arch surgery, antegrade selective cerebral perfusion (SCP), as an adjunct to deep HCA, began its triumphal march, offering excellent neuroprotection and improved overall outcome. This encouraged the use of antegrade SCP in combination with steadily increasing body core temperatures--a trend culminating in the progressive advocation of moderate-to-mild temperatures up to 35 °C, and even normothermia. The impetus for progressive temperature elevation was the limitation of adverse effects of profound hypothermia and the most welcome side effect of significantly shorter cooling and rewarming periods on cardiopulmonary bypass (CPB), and thereby, potentially, the alleviation of the systemic inflammatory response and, in particular, the risk of severe postoperative bleeding (and other organ dysfunctions). The safe limits of prolonged distal circulatory arrest, particularly with regard to the ischaemic tolerance of the viscera and the spinal cord, have not yet been clearly defined. Adverse outcomes due to inappropriate temperature management (core temperatures too high for the required duration of distal arrest) are probably highly underreported. Complications historically associated with hypothermia, namely excessive bleeding, are possibly overestimated. Trading effective neuroprotection and excellent outcomes for the risk of prolonged 'warm' distal ischaemia might constitute a significant step back, jeopardizing visceral and, in particular, spinal cord integrity, with unpredictable consequences for long-term outcome and quality of life, particularly affecting those in need of more complex surgery or with previous neurological deficits.

Hypothermia for aortic surgery

Hypothermic circulatory arrest has been used during aortic arch repairs with acceptable neurologic outcomes. Through the years, we have studied the effects of deep hypothermia on brain metabolism and perfusion both in a pig model and in surgical patients. Hypothermic circulatory arrest has also been used as a method of organ protection in the repair of thoracoabdominal aortic aneurysms. We summarize the clinical and laboratory studies to support the routine use of hypothermic circulatory arrest in clinical practice.

Evolution of cerebral perfusion techniques in type a aortic dissection surgery: a single center experience

BACKGROUND

The purpose of this study was to investigate the effect of using antegrade selective cerebral perfusion (ASCP) with moderate hypothermia on hospital mortality after surgery for acute type A aortic dissection (AAAD).

METHODS

Between January 1998 and December 2008, 142 consecutive patients were operated on for AAAD. Patients were divided into two subgroups: the cohort of patients operated on from January 1998 until December 2003 (without ASCP) (P1998-2003, n=64) and the cohort operated on from January 2004 until December 2008 (with ASCP)(P2004-2008, n=78).

RESULTS

The difference in hospital mortality was statistically significant (P1998-2003: 42.2%; P2004-2008: 14.1%, p<0.0005). Survival rates were 51.6±6.2% vs. 75.1±5.5% and 45.9±6.2% vs. 69.7±7.3% for one and four years, respectively (p=0.001). Multivariate logistic regression analysis revealed that ASCP was the only independent protective factor of hospital mortality (p=0.047).

CONCLUSION

In patients operated on for AAAD, antegrade selective cerebral perfusion with moderate hypothermia is a significant factor in decreasing hospital mortality.

Aortic arch repair with antegrade selective cerebral perfusion using mild to moderate hypothermia of more than 28°C

BACKGROUND

The temperature at circulatory arrest during open distal anastomosis is the most significant issue for aortic arch repair. In many institutions, there has been trend toward raising the temperature during circulatory arrest.

METHODS

Between 2004 and 2011, 164 consecutive patients underwent aortic arch repair with antegrade selective cerebral perfusion (ASCP) and moderate hypothermia. The patients were divided into two subsets (n = 84 each): group A (circulatory arrest at less than 27.9°C) and group B (at more than 28°C).

RESULTS

In group A compared with group B, mean temperature at circulatory arrest was 26° ± 1.0°C vs 29° ± 1.0°C, mean ASCP time was 72 ± 23 minutes vs 67 ± 17 minutes, and mean circulatory arrest time was 47 ± 21 minutes vs 44 ± 13 minutes. The 30-day mortality was 6.1% in both groups. Permanent neurologic deficit occurred in 8 patients (9.8%) in group A and in 5 (6.1%) in group B (p = 0.39). The incidence of renal failure requiring hemodialysis was 14.6% in group A and 3.6% in group B (p = 0.02). Postoperative respiratory failure requiring mechanical ventilation exceeding 3 days occurred in 12.2% of patients in group A and in 7.3% in group B (p = 0.04).

CONCLUSIONS

The temperature during ASCP can be safely increased to more than 28°C without increasing the rate of mortality and morbidity. ASCP with moderate hypothermia offered sufficient cerebral and distal organ protection.

Mild-to-moderate hypothermia in aortic arch surgery using circulatory arrest: a change of paradigm?

OBJECTIVES

Antegrade cerebral perfusion makes deep hypothermia non-essential for neuroprotection; therefore, there is a growing tendency to increase the body temperature during circulatory arrest with selective brain perfusion. However, very little is known about the clinical efficacy of mild-to-moderate hypothermia for ischemic organ protection during circulatory arrest. The aim of this study was to evaluate the safety and efficiency of mild-to-moderate hypothermia for lower-body protection during aortic arch surgery with circulatory arrest and antegrade cerebral perfusion.

METHODS

Between January 2005 and December 2009, a total of 347 patients underwent non-emergent arch surgery. In all patients, the systematic cooling was adapted to the expected time of circulatory arrest, and cerebral perfusion was performed at a constant blood temperature of 28 °C. There were 40 cardiac or aortic re-operations, 312 patients had concomitant aortic valve or root surgery, and 10 patients had replacement of the descending aorta. All examined data were collected prospectively.

RESULTS

The duration of circulatory arrest and the deepest rectal temperature were 18±11 min (range, 6-70 min) and 31.5±1.6 °C (range, 26.0-35.0 °C) for all 347 patients, and 34±12 min (range, 17-70 min) and 29.9±1.7 °C (range, 26.0-34.6 °C) for 77 patients having total/subtotal arch replacement. The maximum serum lactate level on the first postoperative day was, on average, 2.3±1.2 mmol l(-1). In the statistical analysis, no association between the duration of temperature-adapted circulatory arrest and lactate, creatinine, or lactate dehydrogenase levels after surgery could be demonstrated. The 30-day mortality was 0.9%. Permanent neurological deficit or temporary dysfunction occurred in three (0.9%) and eight (2.3%) patients, respectively. No paraplegia and no hepatic failure were reported; however, mesenteric ischemia occurred in one patient with severe stenosis of the celiac and upper mesenteric arteries. Temporary dialysis was necessary primarily after surgery in five patients. All of them underwent hemiarch replacement only, and four patients had an increased creatinine level before surgery.

CONCLUSION

Systemic mild-to-moderate hypothermia that is adapted to the duration of circulatory arrest is a simple, safe, and effective method of organ protection and can be recommended in routine aortic arch surgery with circulatory arrest and cerebral perfusion.

Brief review on systematic hypothermia for the protection of central nervous system during aortic arch surgery: a double-sword tool?

Antegrade selective cerebral perfusion in conjunction with hypothermia attenuate postoperative neurological injury, which in turn still remains the main cause of mortality and morbidity following aortic arch surgery. Hypothermic circulatory arrest however could be a useful tool during arch surgery, surgery for chronic thromboembolic disease, air on the arterial line during CPB, during cavotomy for extraction of renal cell carcinoma with level IV extension, or when dealing with difficult trauma to the SVC or IVC. Cerebral protective effects with hypothermic procedures including inhibition of neuron excitation, and discharge of excitable amino acids, and thereby, prevention of an increase in intercellular calcium ions, hyperoxidation of lipids in cell membranes, and free radical production.The authors are briefly discussing the fundamental principles of using hypothermia as an adjunct tool of the cardiothoracic surgeon's practice. The relationship between temperature, flow, metabolic requirements and adverse effects is addressed.

Repair of multiple aneurysms of the thoracic aorta with a hybrid prosthesis

Complex aneurysmal disease of the thoracic aorta is commonly treated with the elephant trunk technique using two-stage surgery. However, this procedure is associated with high morbidity and mortality. We present the surgical technique used to correct diffuse aneurysmal aortic disease that involves the aortic arch and the descending aorta. The frozen elephant trunk technique using the E-vita Open prosthesis (hybrid procedure), that combines surgical and interventional technologies, was useful to simplify the conventional surgical procedure in a single-stage approach with optimal results.

What is the best method for brain protection in surgery of the aortic arch? Selective antegrade cerebral perfusion

Despite considerable progress in the operative management of lesions involving the transverse aortic arch, replacement of this portion of the vessel remains a surgical challenge and is still associated with mortality and morbidity. This situation is due not only to the technical difficulties of the procedure but, often, to the unsatisfactory preservation of the integrity of the central nervous system during the period of arch exclusion. The techniques of cerebral protection during surgery of the aortic arch can be divided into those aimed at suppressing the metabolic demand of the central nervous system and those aimed at maintaining the metabolic supply during the time of exclusion of the cerebral vessels. Whichever technique is used, it must maintain the normal metabolism of the central nervous system or, at least, allow restoration of the physiologic conditions of its function. In this regard, selective antegrade cerebral perfusion has demonstrated experimentally and clinically its superiority over the other proposed protective techniques.

Integrated Cerebral Protection Combined Antegrade and Retrograde Cerebral Perfusion during Deep Hypothermic Circulatory Arrest

Objective

Aortic arch surgery requires temporary interruption of cerebral perfusion. Hypothermic circulatory arrest (HCA) is an established method of central nervous system protection for limited periods of absent cerebral blood flow. Adjuncts to increase the safe duration of circulatory arrest include either retrograde cerebral perfusion (RCP) or antegrade cerebral perfusion (ACP), with most complex aortic operations now performed using HCA with ACP. We reasoned that optimal cerebral protection might be achieved with a combination of ACP and RCP (integrated brain protection) and present an early clinical experience that supports this approach.

Methods

The integrated brain protection strategy included sequential overlapping periods of RCP, ACP, and RCP during HCA. Moderate systemic hypothermia (25°C) was used. Patient data were gathered through retrospective chart review.

Results

Between 2008 and 2009, six consecutive patients underwent ascending aortic graft replacement for acute type A dissection using HCA and integrated brain protection. The mean minimum systemic temperature was 22.9 ± 1.8°C, the mean total HCA time was 34 ± 5 minutes, and the mean duration of ACP and RCP was 22 ± 6 and 7 ± 5 minutes, respectively. Patients were awake and followed commands 10.1 ± 3.4 (range, 5–13) hours after operation, and there was no evidence of temporary neurologic dysfunction. There was no operative mortality.

Conclusions

Integrated brain protection using both RCP and ACP during HCA is a promising approach for the safe performance of complex aortic surgery and is worthy of evaluation in larger clinical series.

Temperature dependence of cerebral blood flow for isolated regions of the brain during selective cerebral perfusion in pigs

BACKGROUND

Hypothermic circulatory arrest (HCA) and antegrade selective cerebral perfusion (ASCP) are utilized for cerebral protection during aortic surgery. However, no consensus exists regarding optimal ASCP-temperature showing a tendency toward higher values during the last years. This study investigates regional changes of cerebral blood flow (CBF) during ASCP at two temperatures.

METHODS

In this blinded study, 20 pigs (35 to 37 kg) were randomized to two groups. Animals were cooled to 10 minutes of HCA followed by 60 minutes of ASCP. Afterward the animals were perfused at 25 degrees C and 30 degrees C according to the study group. Fluorescent microspheres were injected at seven time points during the experiment to calculate total and regional CBF. Hemodynamics, cerebrovascular resistance (CVR) and cerebral metabolic rate of oxygen (CMRO(2)) were assessed. Tissue samples from the cortex, cerebellum, hippocampus, and pons were taken for microsphere count.

RESULTS

The CBF and CMRO(2) decreased significantly (p < 0.002) during cooling in both groups; it was significantly higher throughout ASCP in the 30 degrees C versus the 25 degrees C group (p = 0.0001). These findings were similar among all brain regions, certainly at different levels. The CBF increased significantly (p = 0.002) during the early period of ASCP for analyzed regions and decreased significantly (p = 0.034) below baseline after 60 minutes of ASCP, reaching critical levels in the hippocampus and neocortex. The hippocampus turned out to have the lowest CBF, while the pons showed the highest CBF. Thirty minutes and more ASCP provides less CBF compared with baseline values at both temperatures.

CONCLUSIONS

Antegrade selective cerebral perfusion improves CBF in all regions of the brain for a limited time. Our study characterizes the brain specific hierarchy of blood flow during ASCP. These dynamics are highly relevant for clinical strategies of perfusion.

Unilateral antegrade selective cerebral perfusion in aortic surgery: clinical outcomes at different levels of hypothermia

Although unilateral antegrade selective cerebral perfusion (UASCP) is considered a safe cerebral protection strategy during aortic surgery, an optimum temperature remains to be defined. This study compared outcomes in patients undergoing UASCP at either <24 or > or =24. Between 2000 and 2007, 104 consecutive patients underwent aortic surgery using UASCP. Patients were divided into two groups according to systemic temperature: group A comprised 64 patients undergoing deep hypothermia (<24); and group B comprised 40 patients undergoing moderate hypothermia (> or =24). Both groups were similar in terms of the extent of aortic replacement and mean UASCP time. The total cardiopulmonary bypass time and aortic cross clamp time were longer in group A. Both groups were similar in terms of 30-day mortality rate (9.4% group A, 10.0% group B), and in terms of temporary (6.7% group A, 7.7% group B) and permanent (11.3% group A, 2.6% group B) neurological deficits. Multivariate analysis showed preoperative shock status was a risk factor for in-hospital mortality, and a preoperative history of a cerebral incident was a risk factor for permanent neurological deficit. UASCP under moderate hypothermia is a relatively safe and effective cerebral protective strategy during aortic surgery.

Analysis of the risk factors of postoperative respiratory dysfunction of type A aortic dissection and lung protection

AIM

Retrospectively to analyze the risk factors of postoperative respiratory dysfunction (RD) in 196 patients with type A dissection operated on with cerebral perfusion and a lower body hypothermia circulatory arrest (HCA) and to investigate the method of the lung protection.

METHODS

From January 2005 to April 2008, 196 patients with type A dissection underwent surgical repair with cerebral perfusion and HCA. There were 142 male patients and 54 female patients, with ages from 17 to 78 years. Antegrade selective cerebral perfusion (SCP) through the axillary artery was performed for 168 patients and retrograde cerebral perfusion (RCP) from the superior vena cava for 28 patients. All the factors underwent univariate and multivariate analysis.

RESULTS

Mean cardiopulmonary bypass (CPB) duration was (186+/-56) minutes and mean cerebral perfusion time was (35+/-15) minutes; mean HCA time was (39+/-14) minutes. Postoperative RD was detected in 26 patients (13.3%). Multivariate analysis showed that the longer duration of circulatory arrest (CA), P=0.008, OR=1.048, and the higher temperature in the bladder during CA, P=0.002, OR=1.614, were independent risk factors of postoperative RD. There was a higher mortality (23.1%, P=0.025) in patients with postoperative RD when compared with the other patients.

CONCLUSION

The longer duration of CA and the higher temperature in the bladder during CA were found to be the independent risk factors of postoperative RD after type A aortic dissection surgery. Attention should be paid to lung protection for these patients and the adjunct of continuing descending aortic perfusion and cerebral perfusion should be a safe and feasible procedure and it would be valuable to perform a prospective trial.

Cerebral metabolism during deep hypothermic circulatory arrest vs moderate hypothermic selective cerebral perfusion in a piglet model: a microdialysis study

BACKGROUND

Few data exist regarding antegrade selective cerebral perfusion (ASCP) and its application in newborn and juvenile patients. Clinical data suggest ASCP alone to be superior to deep hypothermic circulatory arrest (DHCA); however, the effects of moderate hypothermia during ASCP on cerebral metabolism in this patient population are still unclear.

METHODS

After obtaining the approval from animal investigation committee, 16 piglets were randomly assigned to circulatory arrest combined with either ASCP at 27 degrees C or DHCA at 18 degrees C for 90 min. Cerebral oxygen extraction fraction (COEF) from blood as well as cerebral tissue glucose, glycerol, lactate, pyruvate, and the lactate/pyruvate ratio (L/P ratio) by microdialysis were obtained repeatedly.

RESULTS

COEF was lower during cooling and rewarming, respectively, in the DHCA18 group compared to the ASCP27 group (30 +/- 8 vs 56 +/- 13% and 35 +/- 6 vs 58 +/- 7%, respectively). Glucose decreased in both the DHCA18 and ASCP27 groups during the course of cardiopulmonary bypass (CPB), but were higher in the ASCP27 group during ASCP, compared to the DHCA18 group during circulatory arrest (0.7 +/- 0.1 vs 0.2 +/- 0.1 mm.l(-1), P < 0.05). Pyruvate was higher (ASCP27 vs DHCA18: 53 +/- 17 vs 6 +/- 2 microm.l(-1), P < 0.05), and the L/P ratio increased during circulatory arrest in the DHCA18 group, compared to the selective perfusion phase of the ASCP27 group (DHCA18 vs ASCP27: 1891 +/- 1020 vs 70 +/- 28, P < 0.01).

CONCLUSIONS

In this piglet model, both cerebral oxygenation and microdialysis findings suggested a depletion of cerebral energy stores during circulatory arrest in the DHCA18 group, compared to selective cerebral perfusion combined with circulatory arrest in the ASCP27 group.