Moderate hypothermia ≥24 and ≤28°C with hypothermic circulatory arrest for proximal aortic operations in patients...

To determine whether, in patients with previous cardiac operations, moderate hypothermia (between 24 and 28°C) for hypothermic circulatory arrest (HCA) during antegrade cerebral perfusion (ACP) is safe for use during surgery on the proximal aorta and transverse aortic arch.

Over a 7-year period, 118 patients underwent ascending aortic and hemiarch repair (n = 70; 59.3%), total arch replacement (n = 47; 39.8%) or ascending aortic replacement to treat porcelain aorta (n = 1; 0.9%). Simultaneous procedures included aortic root repair or replacement (n = 33; 28.0%) and coronary artery bypass grafting (n = 21; 17.8%). All patients had previously undergone cardiac operations via a median sternotomy. Eighteen patients (15.3%) had more than 1 previous sternotomy, and 24 patients (20.3%) required emergent/urgent operation. Median cardiopulmonary bypass, cardiac ischaemic, circulatory arrest and ACP times (min) were 136.0 [118-180 interquartile range (IQR)], 91.0 (68-119 IQR), 34.0 (21-59 IQR) and 33.5 (20-59 IQR), respectively. The median temperature when HCA was initiated was 24.2°C (24.1-24.8°C IQR).

The operative mortality rate was 10.2% (n = 12). Six patients (5.1%) had a permanent stroke, and 16 patients (13.6%) had a composite adverse outcome (operative mortality and/or a permanent neurological event and/or permanent haemodialysis at discharge). Preoperative renal disease was significantly more prevalent (P= 0.020) and the median circulatory arrest time significantly longer (48.5 vs 33 min; P= 0.058) in patients with composite adverse outcomes. Multivariable analysis of the redo patients showed that age (P =0.025), preoperative renal disease (P =0.024) and ACP time (P =0.012) were independent risk factors for a new postoperative renal injury.

Moderate hypothermia for HCA during ACP is being used with increasing frequency, but has not been thoroughly evaluated in patients undergoing cardiovascular reoperations. Our experience suggests that in patients with previous cardiac surgery who are undergoing hemiarch and total aortic arch operations, moderate hypothermia is safe and produces respectable results.