Bolus administration of esmolol for the treatment of intraoperative myocardial ischaemia

The association of rate pressure product (RPP) and myocardial perfusion imaging (MPI) findings: a preliminary study

Introduction: The product of heart rate and systolic blood pressure, termed as rate-pressure product (RPP), is a very reliable indicator of myocardial oxygen demand and is widely used clinically. There have been previous attempts to describe the relationship between RPP and the onset of pain in angina pectoris. The current study aimed to evaluate the association between RPP results and scan findings.

Materials and methods: In total, 497 patients with suspected coronary artery disease (CAD) underwent gated, single-photon emission computed tomography (SPECT) imaging with dipyridamole, exercise, or dobutamine stress, and were included in this study. Baseline and maximum heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and electrocardiogram (ECG) results were recorded. The rate-pressure product (RPP) was calculated as the product of heart rate and systolic arterial pressure for both baseline and maximum measures. The difference between the RPP max and the basal RPP is known as the RPP reserve. Researchers also obtained semi-quantitative analyses of myocardial perfusion imaging (MPI), using gated software, demographic information, risk factors of CAD, and pretest likelihoods of CAD using nomograms.

Result: Four hundred and ninety-seven cases, including 426 patients with dipyridamole stress, 59 with exercise stress, and 12 with dobutamine stress, underwent myocardial perfusion imaging. Scan results were positive in 194 (45.5%) and negative in 232 (54.5%) patients with dipyridamole stress. In patients with exercise stress, the scan was positive in 24 (40.7%) cases and negative in 35 (59.3%) cases. In dobutamine stressed patients, the scan was positive in 6 (50%) cases and negative in the 6 remaining cases. Dipyridamole stress resulted in a significant difference between HR at rest and at maximum (28.95 ± 24.53, p-value<0.0001), between systolic BP at rest and maximum (6.75 ± 12.50, p-value<0.0001) and between diastolic BP at rest and maximum (1.45 ± 5.80; p-value<0.0001). There was a significant correlation between sum stress scores (SSS) and reserved RPP (r= −0.12, p-value<0.001) which, in dipyridamole patients, was r=−0.18, p-value=0.0001). In addition, there was a significant association between reserved RPP and risk of CAD (p-value<0.001). In the patients with dipyridamole stress, the ejection fraction (EF) change (odds ratio =0.92; 95% CI: 0.86-0.98; p=0.01), reserve RPP (odds ratio =1.00; 95% CI: 1.00-1.00; p=0.04), risk of CAD (odds ratio =5.80; 95% CI: 3.21-10.50; p<0.0001) and age (odds ratio =0.94; 95% CI: 0.89-0.98; p=0.01) were associated significantly with MPI results, using multiple logistic regressions.

Conclusion. The study demonstrated that RPP is associated with MPI findings using gated SPECT imaging with dipyridamole stress. However, to confirm this preliminary result, further studies are mandatory.

ß-Blockers reduce mortality in patients undergoing high-risk non-cardiac surgery

BACKGROUND

ß-Adrenergic receptor antagonists (beta-blockers) are frequently used with the aim of reducing perioperative myocardial ischemia and infarction. However, randomized clinical trials specifically designed to evaluate the effects of beta-blockers on mortality in patients undergoing non-cardiac surgery have yielded conflicting results.

OBJECTIVE

This study aimed to examine the effect of perioperative ß-blockers on total and cardiovascular mortality in patients undergoing non-cardiac surgery.

METHODS

We conducted a meta-analysis of randomized clinical trials that examined the effects of ß-blockers versus placebo on cardiovascular and all-cause mortality in patients undergoing non-cardiac surgery. We extracted data from articles published before 30 November 2009 in peer-reviewed journals indexed in MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE and CINAHL. Data extraction was carried out independently by two reviewers on the basis of an intent-to-treat approach, and inconsistencies were discussed and resolved in conference. The present meta-analysis was undertaken according to the Quality of Reporting of Meta-analyses (QUORUM) statement.

RESULTS

A total of 2148 records were screened, from which we identified 74 randomized controlled trials for non-cardiac surgery. After excluding 49 studies that did not report the clinical outcome of interest or were subanalyses or presented duplicate data, the final search left 25 clinical trials. Treatment with ß-blockers had no significant effect on all-cause mortality (odds ratio [OR] 1.15; 95% confidence interval [CI] 0.92, 1.43; p = 0.2717) or cardiovascular mortality (OR 1.13; 95% CI 0.85, 1.51; p = 0.5855). However, surgical risk category markedly differed across the studies. According to Joint American College of Cardiology and American Heart Association guidelines for perioperative assessment of patients having non-cardiac surgery, five trials evaluated the effect of ß-blockers in patients treated with emergency and vascular surgery (high-risk category) whereas 15 and five trials evaluated the effect of ß-blockers in intermediate low and intermediate high surgical risk categories, respectively. Subgroup analyses showed that the surgical risk category and dose titration of ß-blockers to target heart rate affected the estimate of the effect of ß-blockers for all-cause and cardiovascular mortality. ß-Blockers reduced total mortality by 61% more in patients who underwent high-risk surgery than in those who underwent intermediate high- or intermediate low-risk surgery. When cardiovascular mortality was assessed, the benefit of ß-blockers was 74% greater in trials that titrated ßblockers to heart rate than in trials that did not, although formal statistical significance was not achieved.

CONCLUSIONS

These data suggest that ß-blockers may be useful for reducing mortality in patients who undergo high-risk non-cardiac surgery.

β-blockers and risk of all-cause mortality in non-cardiac surgery

Myocardial ischemia is a frequent complication in patients undergoing non-cardiac surgery and β-blockers may exert a protective effect. The main benefit of β-blockers in perioperative cardiovascular morbidity and mortality is believed to be linked to specific effects on myocardial oxygen supply and demand. β-blockers may exert anti-inflammatory and anti-arrhythmic effects. Randomized clinical trials which evaluated the effects of β-blockers on all-cause mortality in patients undergoing non-cardiac surgery have yielded conflicting results. In 9 trials, 10,544 patients with non-cardiac surgery were randomized to β-blockers (n = 5274) or placebo (n = 5270) and there were a total of 304 deaths. Patients randomized to β-blockers group showed a 19% increased risk of all-cause mortality (odds ratio [OR] 1.19, 95% confidence interval (CI) 0.95-1.50; p = 0.135). However, trials included in the meta-analysis differed in several aspects, and a significant degree of heterogeneity (I 2 = 46.5%) was noted. A recent analysis showed that the surgical risk category had a substantial influence on the overall estimate of the effect of β-blockers. Compared with patients in the intermediate-high-surgical-risk category, those in the high-risk category showed a 73% reduction in the risk of total mortality with β-blockers compared with placebo (OR 0.27, 95% CI 0.10-0.71, p = 0.016). These data suggest that perioperative β-blockers confer a benefit which is mostly limited to patients undergoing high-risk surgery.

QT interval of the ECG, heart rate and arterial pressure during anaesthetic induction: comparative effects of alfentanil and esmolol

In a double-blind study the effect of esmolol and alfentanil on the QT interval of the ECG corrected by the heart rate (QTc), heart rate and arterial pressure during anaesthetic induction was studied in 59 oxycodone- and atropine-premedicated ASA class I-(II) patients with a mean age of 26 yr (range 15-50 yr). The patients were randomly allocated to one of the four groups: saline, esmolol 2 mg.kg-1, esmolol 3 mg.kg-1 or alfentanil 0.03 mg.kg-1. Both doses of esmolol prevented the prolongation of the QTc interval after thiopental and suxamethonium, but not after laryngoscopy and intubation. Alfentanil prevented the prolongation of the QTc interval following thiopental, suxamethonium and laryngoscopy but not after intubation. Esmolol did not prevent the increase in the heart rate and arterial pressure in response to laryngoscopy and intubation. No cardiovascular responses to laryngoscopy and intubation occurred in the patients treated with alfentanil. No cardiac arrhythmias occurred in the esmolol 3 mg.kg-1 group, whereas the frequency of ventricular ectopic beats was 40% in the saline group and 13-20% in the other groups.

Modification of the haemodynamic responses to induction of anaesthesia and tracheal intubation with alfentanil, esmolol and their combination

The purpose of this double-blind randomized work was to study the effect of alfentanil and esmolol and their half-dose combination on the increases of heart rate and arterial pressure and on the prolongation of the QTc interval of the ECG occurring during anaesthetic induction. Sixty ASA class I-II patient with mean age ranging from 26 to 32 yr among the groups. Patients were allocated to one of four equal groups to receive saline, esmolol 2 mg.kg-1, alfentanil 0.03 mg.kg-1 and alfentanil 0.015 mg.kg-1+esmolol 1 mg.kg-1. Anaesthesia was induced with thiopentone. Succinylcholine was used to facilitate tracheal intubation. Haemodynamic variables were measured non-invasively and the QTc interval with the aid of a microcomputer. Comparisons between the groups were performed using two-way analysis of variance with repeated measures. Both alfentanil and alfentanil-esmolol prevented the increase of heart rate and arterial pressure caused by intubation whereas esmolol prevented only the increase of the heart rate. None of the treatments prevented prolongation of the QTc interval after intubation and only alfentanil prevented that after succinylcholine. The present results suggest that in the prevention of the haemodynamic responses to tracheal intubation, the half-dose combination of alfentanil and esmolol is as effective as alfentanil and superior to esmolol. The combination is preferable to relatively large doses of either drug in circumstances where side effects, such as respiratory depression due to alfentanil or bradycardia due to both drugs should be minimized.

Advances in pharmacotherapy: treatment of hypertensive crisis

A hypertensive crisis can be caused by many factors. Frequently, the mechanism involved is complex and highly variable among patients. Without drug therapy, this condition is associated with very high mortality and morbidity. There are a number of oral and intravenous hypotensive agents available, which can effectively control blood pressure in a hypertensive crisis. The relative advantages and disadvantages of each treatment option is discussed.

A comparison of fentanyl, esmolol, and their combination for blunting the haemodynamic responses during rapid-sequence induction

The purpose of this randomized, double-blind study was to compare the ability of a combination of fentanyl and esmolol to blunt the haemodynamic effects of intubation with that of either agent alone. Patients received fentanyl or saline four minutes before, and esmolol or saline two minutes before rapid-sequence induction of anaesthesia. The F2 group (n = 24) received fentanyl 2 micrograms.kg-1, the E2 group (n = 24) received esmolol 2 mg.kg-1, the F2/E2 group (n = 25) received a combination of fentanyl 2 micrograms.kg-1 and esmolol 2 mg.kg-1, and the F5 group (n = 26) received fentanyl 5 micrograms.kg-1. Following tracheal intubation, the maximum percent change from baseline heart rate was less in the F2/E2 and F5 groups (12% and 16% respectively) than in the E2 group (34%)(P < 0.05). The maximum percent changes from baseline systolic blood pressure in the F2/E2 and F5 groups (15% and 6% respectively) were less than in the F2 and E2 groups (24% and 33% respectively) (P < 0.05). The combination of a low dose of fentanyl and esmolol provides an alternative to a higher dose of fentanyl for blunting the haemodynamic responses to laryngoscopy and tracheal intubation during rapid-sequence induction in healthy patients.

A bolus dose of esmolol attenuates tachycardia and hypertension after tracheal intubation

Forty-five patients of ASA physical status I and II undergoing a variety of non-cardiac surgical procedures were studied to determine the effect of bolus administration of esmolol, a new short-acting beta blocking drug, on heart rate and blood pressure responses to induction of anaesthesia and tracheal intubation. Subjects were allocated randomly to receive placebo, 100 mg or 200 mg of esmolol IV as part of an anaesthetic induction technique. The differences in heart rate between the placebo group and both the 100 mg and 200 mg groups were significant prior to intubation (95 +/- 7.9, 82 +/- 9.7, 80 +/- 7.3 beats per min respectively), and also at 0.5 min and 1.5 min following intubation for the 200 mg group. In the 200 mg group there was a significant decrease, compared with placebo, in systolic blood pressure at 0.5 min (144 +/- 32.1 vs 165 +/- 18.7 mmHg) and 1.5 min (154 +/- 25.0 vs 170 +/- 19.5 mmHg) after intubation. In this study, adequate haemodynamic control was obtained following administration of 200 mg of esmolol.