Positive end-expiratory pressure during infrarenal aortic clamping limits hemodynamic impairment risk

Abstract

Aortic clamping and unclamping abruptly impact hemodynamic assessment. First, vascular resistance and venous blood return increase, causing a cardiac stress; second, when the clamp has been replaced, vascular resistance falls and hypotension with low perfusion pressure risk occurs. We hypothesized that positive end-expiratory pressure (PEEP) during clamping could limit hemodynamic alterations, then its zeroing just before unclamping could guarantee a more stable blood pressure after restoring total circulation. Seventy-one patients submitted to aortic infra-renal aneurismectomy were divided into three groups according to PEEP application (0, 5 and 10 cmH2O) during the clamping phase. Just before restoring total circulation, PEEP was zeroed for all patients. Data were collected before clamping, during clamping and after clamp release. After aortic clamping, PEEP of 10 cmH2O significantly limited the mean arterial pressure increase (P = 0.017). The same occurred with a PEEP of 5 cmH2O, but it was not statistically significant (P = 0.341). In group A (PEEP 0 cmH2O), mean and systolic blood pressure did not rise significantly (P = 0.478 and P = 0.403, respectively), but after unclamping, we recorded a significant reduction in mean arterial pressure (from 89.8 +/- 10.2 to 80.6 +/- 12.7 mmHg; P = 0.002) and systolic blood pressure (from 131.3 +/- 14.7 mmHg to 116.8 +/- 22.2 mmHg; P = 0.002). It did not occur in the PEEP 5 cmH2O group. In the PEEP 10 cmH2O group, only mean arterial pressure reduced significantly, even if its variation was more limited than in the zero end-expiratory pressure (ZEEP) group (from 86.9 +/- 12.1 to 81.4 +/- 8.1 mmHg; P = 0.028). PEEP-mechanical ventilation during the clamping phase of infrarenal aortic aneurismectomy can limit blood pressure variation due to clamping and unclamping.