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Echocardiographic assessment of coronary blood flow velocity during controlled hypotensive anesthesia with
M S Mikhail1, D Thangathurai, K B Thaker
1Department of Anesthesiology, University of Southern California School of Medicine, Kenneth Norris Hospital, Los Angeles 90033, USA.
Objective:
To determine the effect of nitroglycerin on coronary blood flow velocity during controlled hypotensive anesthesia in humans.
Design:
Internally controlled prospective study.
Setting:
Single university hospital.
Participants:
Twenty American Society of Anesthesiologists class I and II patients undergoing general anesthesia for surgical resection of a malignancy.
Interventions:
General anesthesia was induced with thiopental, fentanyl, and succinylcholine and maintained with isoflurane and vecuronium. Transesophageal echocardiography was used to evaluate left ventricular wall motion and blood flow velocity in the left anterior descending coronary artery. Intravenous nitroglycerin was used to reduce systolic arterial pressure to 60 to 70 mmHg. Intravenous albumin 5% was administered to maintain pulmonary capillary wedge pressure >5 mmHg.
Measurements And Main Results:
The left anterior descending coronary artery was visualized clearly in 16 of 20 patients. At a mean nitroglycerin dose of 16+/-14 microg/kg/min, peak diastolic left anterior descending flow velocity increased significantly from 32.5+/-10.3 cm/sec to 44.7+/-14.6 cm/sec (p = 0.0103). None of the patients developed any ST-segment changes.
Conclusions:
During nitroglycerin-induced hypotensive anesthesia, coronary blood flow as assessed by peak diastolic left anterior descending flow velocity is preserved or increased in most patients. Increases in left anterior descending flow velocity are predictably achieved only at nitroglycerin doses >5 microg/kg/min. Intraoperative transesophageal echocardiography is useful in monitoring coronary flow velocity responses to controlled hypotensive anesthesia.
