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

Abstract

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.

Figure 1:

Schematic illustration of complete arch and descending aorta replacement that demonstrates method for limiting duration of circulatory arrest. Arterial line is armed with 2 additional branches using Y-shaped connectors. The first line is placed in carotid artery (CA) for establishment of cardiopulmonary bypass and unilateral cerebral perfusion during circulatory arrest. After completing distal anastomosis (1), aortic graft is cannulated with the second branch of the arterial line (1a) and cross-clamped (CC) in order to re-establish perfusion of lower body. Alternatively the femoral artery can be cannulated with this branch primarily (FA). After completing anastomoses between aortic arch graft and supraaortic arteries (2), graft is cannulated with third branch of the arterial line and cross-clamped at both ends allowing re-establishment of full cerebral perfusion. The next step consists of proximal aortic and cardiac repairs, and re-establishment of myocardial perfusion (3), followed lastly by anastomosing arch graft with aorta descending prosthesis (4). For other details see text.

Figure 2:

Schematic illustration of complete aortic arch replacement that demonstrates the method for limiting duration of circulatory arrest and unilateral cerebral perfusion. After completing distal anastomosis (1) and cross-clamping (CC) the aortic arch graft and its side branches, graft is cannulated through the 4th side branch and perfusion of lower body is re-established. Cerebral perfusion is re-established step-by-step after completing of each further anastomosis (2–4) starting with the left carotid artery (LCA), then followed by the left subclavian artery (LSA) then the innominate artery (IA). Thereafter the arterial line branch to the carotid artery is cross-clamped and arterial return is performed through aortic arch graft exclusively. Surgery is completed by proximal aortic and cardiac repairs and re-establishment of myocardial perfusion (5). For further details see text.

Figure 3:

Scatter plots showing no association between lactate level (upper row), LDH level (mid row) and creatinine level (bottom row), and duration of CA and CPB.