Hemodynamics of chronic experimental aortic insufficiency

Propofol and fentanyl take longer for induction of anesthesia in aortic regurgitation: a case-controlled prospective study

OBJECTIVES

This study was conducted to determine if induction time of anesthesia in patients with aortic regurgitation (AR) is different from patients with a normal aortic valve (AV).

DESIGN

A prospective, case-control study.

SETTING

A single institutional study conducted in a tertiary care teaching hospital.

PARTICIPANTS

Twenty-four male patients scheduled for cardiac surgery, group I (n = 12) patients with competent AV and group 2 (n = 12) with severe AR.

INTERVENTIONS

General anesthesia was induced by intravenous infusion of propofol and fentanyl.

MEASUREMENTS AND MAIN RESULTS

Continuous measurements of heart rate, intra-arterial blood pressure, and bispectral index were recorded. Induction doses of propofol and fentanyl were analyzed and compared. There was significant difference between the 2 groups in terms of induction time of anesthesia (mean ± SD 308 ± 68.2 seconds in group 1 v 445 ± 97.9 seconds in group 2). The patients in group 2 (AR) required significantly larger doses of propofol (0.91 ± 0.40 mg/kg) than the patients in group 1 (0.49 ± 0.17 mg/kg). Similarly, fentanyl dose was increased in the group 2 patients (20.8 ± 15.9 µg/kg) compared with the group 1 patients (9.2 ± 2.9 µg/kg).

CONCLUSION

The authors concluded that there was a significant prolongation of the induction time of anesthesia and the need of larger doses of propofol and fentanyl by slow intravenous infusion regimen in patients with AR compared with patients with a competent aortic valve.

Phasic changes in human right coronary blood flow before and after repair of aortic insufficiency

We have shown previously that acute aortic insufficiency in chronically instrumented dogs reverses the normally high ratio of diastolic to systolic coronary blood flow. Phasic blood flow in the dominant right coronary artery was measured directly with an electromagnetic flow meter during surgery in eight patients with severe aortic insufficiency before and after relacement of the aortic valve. Before the insufficiency was eliminated, right coronary flow average 116 +/- 37 ml./minute and the diastolic to systolic flow ratio was 0.88 +/- 17. Mean arterial blood pressure averaged 106 +/- 17 mm. Hg, heart rate 84 +/- 19 beats/minute, and mean diastolic pressure averaged 67 +/- 10 mm. Hg. After the aortic valve was replaced with an average heart rate of 90 +/- 15 and mean blood pressure of 103 +/- 13 mm. Hg, the average right coronary blood flow increased to 180 +/- 40 ml./minute with a D/S ratio of 2.18 +/- 0.8. In all cases the right coronary blood flow increased after the aortic insufficiency was eliminated surgically. Right coronary flow probably increased because of the improved diastolic perfusion pressure and the change from predominantly systolic to diastolic coronary flow.

Direct determinations of aortic blood flow in patients with aortic regurgitation. Effects of alterations in heart rate, increased ventricular preload or afterload, and isoproterenol

Instantaneous ascending aortic blood flow and left ventricular and central aortic pressure were determined at the time of operation in nine patients with severe aortic regurgitation. In six, the heart rate was controlled and increased by electrical stimulation between 50 and 170 beats/min. The relative duration of diastole decreased, and that of systole increased at faster heart rates. The mean systolic ejection rate fell, and regurgitant flow rates remained relatively constant. Thus, the per cent regurgitation was not reduced at faster rates. Following isoproterenol administration, the faster heart rate lengthened the relative duration of systole, abbreviated that of diastole, and increased the systolic ejection rate. Net result was an increased total forward flow and a reduced per cent regurgitation, but when the heart rate was held constant, the total forward stroke volume was ejected more rapidly, but the total forward and regurgitant flows per beat and per minute, and consequently the per cent regurgitation did not change. Assessments of left venticular function also were made in two patients.