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

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.

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.

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.

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.