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

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSION: PEEP-mechanical ventilation during the clamping phase of infrarenal aortic aneurismectomy can limit blood pressure variation due to clamping and unclamping.