The present study examined the postulate that the quotient of mean systemic arterial pressure and heart rate predicts the severity of myocardial ischemia during occlusion of the left anterior descending coronary artery. Studies were performed in open-chest fentanyl-anesthetized dogs before and during halothane (n = 8) or isoflurane (n = 8) anesthesia. The pressure-rate quotient (PRQ) decreased significantly in both groups during incremental increases in halothane or isoflurane to 68% and 57% of control values at 0.5 MAC and to 41% and 38% at 1.5 MAC for halothane and isoflurane, respectively. Myocardial lactate production was unchanged from the ischemic region, and no correlation between the PRQ and myocardial lactate production was observed. In contrast, heart rate correlated significantly (r = 0.376; P < 0.05) with lactate production. The product of systolic systemic arterial pressure and heart rate (rate-pressure product) correlated with blood flow (r = 0.493; P < 0.001) and with oxygen consumption (r = 0.571; P < 0.001) in the normal myocardium. A weak correlation (r = 0.330; P < 0.05) of rate-pressure product with myocardial lactate production from the ischemic region was observed. There were no correlations between the PRQ and myocardial lactate production from the ischemic region or indices of blood flow distribution (i.e., inner/outer ratio in the ischemic region or ischemic/normal ratio). The relationship of hemodynamic variables to measurements of regional myocardial metabolism was independent of background anesthetic agent or depth of anesthesia. The current data suggest that heart rate changes are weakly predictive of severity of myocardial ischemia. No interdependence between heart rate and blood pressure on blood flow regulation to ischemic myocardium is evident. The findings indicate that the PRQ has limited prognostic value in the assessment of severity of myocardial ischemia under laboratory conditions.
|Original language||English (US)|
|Number of pages||9|
|Journal||Anesthesia and Analgesia|
|State||Published - 1992|
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine