Automatic postoperative monitoring of infrainguinal bypass procedures

Objective: To evaluate the usefulness of a portable, computer-based, oscillometric, noninvasive blood pressure monitor for the automatic surveillance of postoperative infrainguinal bypasses. Design: Prospective unblinded study. Setting: Regional tertiary care Veterans Affairs medical center. Patients: A total of 60 limbs were examined in 3 groups (n=20 in each group): normal, asymptomatic volunteers; older patients with symptomatic peripheral vascular disease; and patients who had undergone infrainguinal bypass procedures. Interventions: Noninvasive blood pressure monitor pressures, complete lower extremity arterial studies with Doppler ankle- brachial index (ABI), segmental pressures, and pulse volume recordings were performed in all groups. The patients who had undergone surgery also had hourly noninvasive blood pressure measurements taken. Main Outcome Measures: Ankle-brachial indices obtained with the noninvasive blood pressure monitor were compared with simultaneous manual Doppler ABIs and pulse volume recordings. Results: There was a significant overall correlation between the Doppler-derived ABIs and automatic oscillometric values (r=0.89, P<.001). Although there was a slight difference in absolute values (±SEM) (0.90±0.03 vs 0.84±0.03, respectively), an excellent correlation was found between the 2 methods in the clinically relevant range of ABI values between 0.60 and 1.10. The oscillometric method, however, overestimated the ABI when it was less than 0.60 by the Doppler method (0.61±0.02 vs 0.44±0.03, P<.001) and underestimated it when it was more than 1.10 (1.05±0.02 vs 1.16±0.01, P<.001). (All values given as ±SEM.) Oscillometric overestimation correlated with depressed pulse volume recording waveforms (P<.001) or diminished pulse volume recording amplitudes of less than 10 mm (P<.001). Conclusion: The automatic oscillometric monitor provides a useful, accurate, objective, and quantitative method for postoperative bypass graft surveillance.