Moderate Hypothermia Protects Visceral Organs During Circulatory Arrest

Though surgeons use different types of selective antegrade cerebral perfusion (SACP) to protect the brain during aortic arch surgery, the appropriate method to provide distal organ protection during circulatory arrest remains unclear.

To offer clarification, researchers from the University of Bologna in Italy published a study in the January 2014 issue of the European Journal of Cardio-Thoracic Surgery that retrospectively evaluated aortic arch surgery using SACP at different temperatures, focusing on visceral functions by comparing preoperative and postoperative creatinine, aspartate aminotransferase, alanine aminotransferase, and bilirubin levels.

The authors enrolled 334 patients who underwent elective aortic arch surgery using SACP from November 1996 to March 2011. Among the 194 patients assigned to Group A, the surgical team used deeper systemic hypothermia ≤25°C, and in the 110 patients assigned to Group B, the team employed moderate hypothermia >25°C.

According to the researchers, the 30-day mortality rate in Group A was 5.2%, compared to 3.6% in Group B. On the other hand, permanent neurological deficits occurred in only 4 patients in Group A, compared to 14 patients in Group B, and only 6 patients in Group A developed postoperative renal insufficiency requiring dialysis, compared to 15 in Group B. However, none of those differences were statistically significant, and postoperative increases in biochemical markers were similar between the 2 groups.

Cardiopulmonary bypass time >180 minutes was the only significant risk factor for renal dysfunction with or without liver dysfunction, while both cardiopulmonary bypass time >180 minutes and hypothermia >25°C were independently related to liver dysfunction.

Although most of the differences between the 2 groups were statistically insignificant, the researchers concluded that moderate hypothermia more effectively protects visceral organs during circulatory arrest, likely by reducing the systemic inflammatory response and reperfusion organ injury. Thus, the authors concluded that SACP performed at >25°C should be the preferred surgical method for periods of visceral ischemia limited to <60 min.