Cardiovascular responses to anaesthesia. Influence of beta-adrenoreceptor blockade with metoprolol

Comparative Study of Gabapentin, Clonidine and Placebo in Alleviating the Hemodynamic Changes Due to Tracheal Intubation and Laryngoscopy

INTRODUCTION

Hemodynamic changes during laryngoscopy and tracheal intubation must be reduced for safe and effective anesthesia. The present study was conducted to compare the efficacy of oral clonidine, gabapentin and placebo in alleviating the hemodynamic changes due to tracheal intubation and laryngoscopy.

METHODS

This was a double-blinded randomized controlled trial conducted on 90 patients who were undergoing elective surgery and were randomized into three groups. Group I (n=30) received a placebo, group II (n=30) received gabapentin and group III (n=30) received clonidine as premedication before anesthesia induction. Patient heart rate and pressor response were recorded periodically and compared between the groups.

RESULTS

There was no significant difference in the baseline heart rate (HR) and mean arterial pressure (MAP) between the groups. HR elevation was observed in all three groups and found to be significant (p=0.0001) but the increase was higher in the placebo (15 min: 80.80± 15.41) and lower in the clonidine group (15 min: 65.53± 12.43). The elevation in systolic and diastolic blood pressure was least and transient in the gabapentin group, as compared to placebo and clonidine group. Intra-operatively, the requirement of opioids was higher in the placebo as compared to clonidine and gabapentin (p < .001).

CONCLUSION

Clonidine and gabapentin were effective in reducing the hemodynamic changes during laryngoscopy and intubation.

Generalisability of randomised trials evaluating perioperative β-blocker therapy in noncardiac surgery

BACKGROUND

The limited applicability of evidence from RCTs in real-word practice is considered a potential bottleneck for evidence-based practice but rarely systematically assessed. Using our failure to recruit patients into a perioperative beta-blocker trial, we set out to analyse the restrictiveness and generalisability of trial eligibility criteria in a real-world cohort.

METHODS

We prospectively included adult patients (≥18 yr) scheduled for elective noncardiac surgery at an academic tertiary care facility who were screened for inclusion in a planned perioperative beta-blocker RCT, which was terminated owing to recruitment failure. The primary outcome was the proportion of screened patients who matched the eligibility criteria of 36 published RCTs included in a large Cochrane meta-analysis on perioperative beta-blocker therapy. The pragmatic/explanatory level of each RCT was assessed using the PRagmatic-Explanatory Continuum Indicator Summary 2 (PRECIS-2) score, which ranges from 9 points (indicating a very explanatory study) to 45 points (indicating a very pragmatic study).

RESULTS

A total of 2241 patients (54% female, n=1215; 52 [standard deviation, 20] yr) were included for the assessment of trial eligibility between October 2015 and January 2016. Only a small proportion of patients matched the inclusion and exclusion criteria for each of the 36 RCTs, ranging from 53% to 0%. The average proportion of patients who did match the eligibility criteria of all 36 RCTs was 6.5% (n=145; 95% confidence interval, 6.3-6.6). A higher PRECIS-2 score was associated with a higher proportion of matching patients (P<0.001).

CONCLUSIONS

Trial eligibility criteria in perioperative beta-blocker therapy trials are overly restrictive and not generalisable to a real-world surgical population.

CLINICAL TRIAL REGISTRATION

EudraCT#: 2015-002366-23.

Perioperative beta-blockers for preventing surgery-related mortality and morbidity in adults undergoing non-cardiac surgery

BACKGROUND

Randomized controlled trials (RCTs) have yielded conflicting results regarding the ability of beta-blockers to influence perioperative cardiovascular morbidity and mortality. Thus routine prescription of these drugs in an unselected population remains a controversial issue. A previous version of this review assessing the effectiveness of perioperative beta-blockers in cardiac and non-cardiac surgery was last published in 2018. The previous review has now been split into two reviews according to type of surgery. This is an update, and assesses the evidence in non-cardiac surgery only.

OBJECTIVES

To assess the effectiveness of perioperatively administered beta-blockers for the prevention of surgery-related mortality and morbidity in adults undergoing non-cardiac surgery.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, Biosis Previews and Conference Proceedings Citation Index-Science on 28 June 2019. We searched clinical trials registers and grey literature, and conducted backward- and forward-citation searching of relevant articles.

SELECTION CRITERIA

We included RCTs and quasi-randomized studies comparing beta-blockers with a control (placebo or standard care) administered during the perioperative period to adults undergoing non-cardiac surgery. If studies included surgery with different types of anaesthesia, we included them if 70% participants, or at least 100 participants, received general anaesthesia. We excluded studies in which all participants in the standard care control group were given a pharmacological agent that was not given to participants in the intervention group, studies in which all participants in the control group were given a beta-blocker, and studies in which beta-blockers were given with an additional agent (e.g. magnesium). We excluded studies that did not measure or report review outcomes.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, extracted data, and assessed risks of bias. We assessed the certainty of evidence with GRADE.

MAIN RESULTS

We included 83 RCTs with 14,967 participants; we found no quasi-randomized studies. All participants were undergoing non-cardiac surgery, and types of surgery ranged from low to high risk. Types of beta-blockers were: propranolol, metoprolol, esmolol, landiolol, nadolol, atenolol, labetalol, oxprenolol, and pindolol. In nine studies, beta-blockers were titrated according to heart rate or blood pressure. Duration of administration varied between studies, as did the time at which drugs were administered; in most studies, it was intraoperatively, but in 18 studies it was before surgery, in six postoperatively, one multi-arm study included groups of different timings, and one study did not report timing of drug administration. Overall, we found that more than half of the studies did not sufficiently report methods used for randomization. All studies in which the control was standard care were at high risk of performance bias because of the open-label study design. Only two studies were prospectively registered with clinical trials registers, which limited the assessment of reporting bias. In six studies, participants in the control group were given beta-blockers as rescue therapy during the study period.The evidence for all-cause mortality at 30 days was uncertain; based on the risk of death in the control group of 25 per 1000, the effect with beta-blockers was between two fewer and 13 more per 1000 (risk ratio (RR) 1.17, 95% confidence interval (CI) 0.89 to 1.54; 16 studies, 11,446 participants; low-certainty evidence). Beta-blockers may reduce the incidence of myocardial infarction by 13 fewer incidences per 1000 (RR 0.72, 95% CI 0.60 to 0.87; 12 studies, 10,520 participants; low-certainty evidence). We found no evidence of a difference in cerebrovascular events (RR 1.65, 95% CI 0.97 to 2.81; 6 studies, 9460 participants; low-certainty evidence), or in ventricular arrhythmias (RR 0.72, 95% CI 0.35 to 1.47; 5 studies, 476 participants; very low-certainty evidence). Beta-blockers may reduce atrial fibrillation or flutter by 26 fewer incidences per 1000 (RR 0.41, 95% CI 0.21 to 0.79; 9 studies, 9080 participants; low-certainty evidence). However, beta-blockers may increase bradycardia by 55 more incidences per 1000 (RR 2.49, 95% CI 1.74 to 3.56; 49 studies, 12,239 participants; low-certainty evidence), and hypotension by 44 more per 1000 (RR 1.40, 95% CI 1.29 to 1.51; 49 studies, 12,304 participants; moderate-certainty evidence).We downgraded the certainty of the evidence owing to study limitations; some studies had high risks of bias, and the effects were sometimes altered when we excluded studies with a standard care control group (including only placebo-controlled trials showed an increase in early mortality and cerebrovascular events with beta-blockers). We also downgraded for inconsistency; one large, well-conducted, international study found a reduction in myocardial infarction, and an increase in cerebrovascular events and all-cause mortality, when beta-blockers were used, but other studies showed no evidence of a difference. We could not explain the reason for the inconsistency in the evidence for ventricular arrhythmias, and we also downgraded this outcome for imprecision because we found few studies with few participants.

AUTHORS' CONCLUSIONS

The evidence for early all-cause mortality with perioperative beta-blockers was uncertain. We found no evidence of a difference in cerebrovascular events or ventricular arrhythmias, and the certainty of the evidence for these outcomes was low and very low. We found low-certainty evidence that beta-blockers may reduce atrial fibrillation and myocardial infarctions. However, beta-blockers may increase bradycardia (low-certainty evidence) and probably increase hypotension (moderate-certainty evidence). Further evidence from large placebo-controlled trials is likely to increase the certainty of these findings, and we recommend the assessment of impact on quality of life. We found 18 studies awaiting classification; inclusion of these studies in future updates may also increase the certainty of the evidence.

Perioperative beta-blockers for preventing surgery-related mortality and morbidity

BACKGROUND

Randomized controlled trials have yielded conflicting results regarding the ability of beta-blockers to influence perioperative cardiovascular morbidity and mortality. Thus routine prescription of these drugs in unselected patients remains a controversial issue.

OBJECTIVES

The objective of this review was to systematically analyse the effects of perioperatively administered beta-blockers for prevention of surgery-related mortality and morbidity in patients undergoing any type of surgery while under general anaesthesia.

SEARCH METHODS

We identified trials by searching the following databases from the date of their inception until June 2013: MEDLINE, Embase , the Cochrane Central Register of Controlled Trials (CENTRAL), Biosis Previews, CAB Abstracts, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Derwent Drug File, Science Citation Index Expanded, Life Sciences Collection, Global Health and PASCAL. In addition, we searched online resources to identify grey literature.

SELECTION CRITERIA

We included randomized controlled trials if participants were randomly assigned to a beta-blocker group or a control group (standard care or placebo). Surgery (any type) had to be performed with all or at least a significant proportion of participants under general anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from all studies. In cases of disagreement, we reassessed the respective studies to reach consensus. We computed summary estimates in the absence of significant clinical heterogeneity. Risk ratios (RRs) were used for dichotomous outcomes, and mean differences (MDs) were used for continuous outcomes. We performed subgroup analyses for various potential effect modifiers.

MAIN RESULTS

We included 88 randomized controlled trials with 19,161 participants. Six studies (7%) met the highest methodological quality criteria (studies with overall low risk of bias: adequate sequence generation, adequate allocation concealment, double/triple-blinded design with a placebo group, intention-to-treat analysis), whereas in the remaining trials, some form of bias was present or could not be definitively excluded (studies with overall unclear or high risk of bias). Outcomes were evaluated separately for cardiac and non-cardiac surgery.CARDIAC SURGERY (53 trials)We found no clear evidence of an effect of beta-blockers on the following outcomes.• All-cause mortality: RR 0.73, 95% CI 0.35 to 1.52, 3783 participants, moderate quality evidence.• Acute myocardial infarction (AMI): RR 1.04, 95% CI 0.71 to 1.51, 3553 participants, moderate quality evidence.• Myocardial ischaemia: RR 0.51, 95% CI 0.25 to 1.05, 166 participants, low quality evidence.• Cerebrovascular events: RR 1.52, 95% CI 0.58 to 4.02, 1400 participants, low quality evidence.• Hypotension: RR 1.54, 95% CI 0.67 to 3.51, 558 participants, low quality evidence.• Bradycardia: RR 1.61, 95% CI 0.97 to 2.66, 660 participants, low quality evidence.• Congestive heart failure: RR 0.22, 95% CI 0.04 to 1.34, 311 participants, low quality evidence.Beta-blockers significantly reduced the occurrence of the following endpoints.• Ventricular arrhythmias: RR 0.37, 95% CI 0.24 to 0.58, number needed to treat for an additional beneficial outcome (NNTB) 29, 2292 participants, moderate quality evidence.• Supraventricular arrhythmias: RR 0.44, 95% CI 0.36 to 0.53, NNTB five, 6420 participants, high quality evidence.• On average, beta-blockers reduced length of hospital stay by 0.54 days (95% CI -0.90 to -0.19, 2450 participants, low quality evidence).NON-CARDIAC SURGERY (35 trials)Beta-blockers significantly increased the occurrence of the following adverse events.• All-cause mortality: RR 1.25, 95% CI 1.00 to 1.57, 11,413 participants, low quality of evidence, number needed to treat for an additional harmful outcome (NNTH) 167.• Hypotension: RR 1.50, 95% CI 1.38 to 1.64, NNTH 16, 10,947 participants, high quality evidence.• Bradycardia: RR 2.23, 95% CI 1.48 to 3.36, NNTH 21, 11,033 participants, moderate quality evidence.We found a potential increase in the occurrence of the following outcomes with the use of beta-blockers.• Cerebrovascular events: RR 1.59, 95% CI 0.93 to 2.71, 9150 participants, low quality evidence.Whereas no clear evidence of an effect was found when all studies were analysed, restricting the meta-analysis to low risk of bias studies revealed a significant increase in cerebrovascular events with the use of beta-blockers: RR 2.09, 95% CI 1.14 to 3.82, NNTH 265, 8648 participants.Beta-blockers significantly reduced the occurrence of the following endpoints.• AMI: RR 0.73, 95% CI 0.61 to 0.87, NNTB 76, 10,958 participants, high quality evidence.• Myocardial ischaemia: RR 0.51, 95% CI 0.34 to 0.77, NNTB nine, 978 participants, moderate quality evidence.• Supraventricular arrhythmias: RR 0.73, 95% CI 0.57 to 0.94, NNTB 112, 8744 participants, high quality evidence.We found no clear evidence of an effect of beta-blockers on the following outcomes.• Ventricular arrhythmias: RR 0.68, 95% CI 0.31 to 1.49, 476 participants, moderate quality evidence.• Congestive heart failure: RR 1.18, 95% CI 0.94 to 1.48, 9173 participants, moderate quality evidence.• Length of hospital stay: mean difference -0.45 days, 95% CI -1.75 to 0.84, 551 participants, low quality evidence.

AUTHORS' CONCLUSIONS

According to our findings, perioperative application of beta-blockers still plays a pivotal role in cardiac surgery, as they can substantially reduce the high burden of supraventricular and ventricular arrhythmias in the aftermath of surgery. Their influence on mortality, AMI, stroke, congestive heart failure, hypotension and bradycardia in this setting remains unclear.In non-cardiac surgery, evidence shows an association of beta-blockers with increased all-cause mortality. Data from low risk of bias trials further suggests an increase in stroke rate with the use of beta-blockers. As the quality of evidence is still low to moderate, more evidence is needed before a definitive conclusion can be drawn. The substantial reduction in supraventricular arrhythmias and AMI in this setting seems to be offset by the potential increase in mortality and stroke.

Perioperative beta-blockers for preventing surgery-related mortality and morbidity

BACKGROUND

Randomized controlled trials have yielded conflicting results regarding the ability of beta-blockers to influence perioperative cardiovascular morbidity and mortality. Thus routine prescription of these drugs in unselected patients remains a controversial issue.

OBJECTIVES

The objective of this review was to systematically analyse the effects of perioperatively administered beta-blockers for prevention of surgery-related mortality and morbidity in patients undergoing any type of surgery while under general anaesthesia.

SEARCH METHODS

We identified trials by searching the following databases from the date of their inception until June 2013: MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Biosis Previews, CAB Abstracts, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Derwent Drug File, Science Citation Index Expanded, Life Sciences Collection, Global Health and PASCAL. In addition, we searched online resources to identify grey literature.

SELECTION CRITERIA

We included randomized controlled trials if participants were randomly assigned to a beta-blocker group or a control group (standard care or placebo). Surgery (any type) had to be performed with all or at least a significant proportion of participants under general anaesthesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from all studies. In cases of disagreement, we reassessed the respective studies to reach consensus. We computed summary estimates in the absence of significant clinical heterogeneity. Risk ratios (RRs) were used for dichotomous outcomes, and mean differences (MDs) were used for continuous outcomes. We performed subgroup analyses for various potential effect modifiers.

MAIN RESULTS

We included 89 randomized controlled trials with 19,211 participants. Six studies (7%) met the highest methodological quality criteria (studies with overall low risk of bias: adequate sequence generation, adequate allocation concealment, double/triple-blinded design with a placebo group, intention-to-treat analysis), whereas in the remaining trials, some form of bias was present or could not be definitively excluded (studies with overall unclear or high risk of bias). Outcomes were evaluated separately for cardiac and non-cardiac surgery. CARDIAC SURGERY (53 trials)We found no clear evidence of an effect of beta-blockers on the following outcomes.• All-cause mortality: RR 0.73, 95% CI 0.35 to 1.52, 3783 participants, moderate quality of evidence.• Acute myocardial infarction (AMI): RR 1.04, 95% CI 0.71 to 1.51, 3553 participants, moderate quality of evidence.• Myocardial ischaemia: RR 0.51, 95% CI 0.25 to 1.05, 166 participants, low quality of evidence.• Cerebrovascular events: RR 1.52, 95% CI 0.58 to 4.02, 1400 participants, low quality of evidence.• Hypotension: RR 1.54, 95% CI 0.67 to 3.51, 558 participants, low quality of evidence.• Bradycardia: RR 1.61, 95% CI 0.97 to 2.66, 660 participants, low quality of evidence.• Congestive heart failure: RR 0.22, 95% CI 0.04 to 1.34, 311 participants, low quality of evidence.Beta-blockers significantly reduced the occurrence of the following endpoints.• Ventricular arrhythmias: RR 0.37, 95% CI 0.24 to 0.58, number needed to treat for an additional beneficial outcome (NNTB) 29, 2292 participants, moderate quality of evidence.• Supraventricular arrhythmias: RR 0.44, 95% CI 0.36 to 0.53, NNTB six, 6420 participants, high quality of evidence.• On average, beta-blockers reduced length of hospital stay by 0.54 days (95% CI -0.90 to -0.19, 2450 participants, low quality of evidence). NON-CARDIAC SURGERY (36 trials)We found a potential increase in the occurrence of the following outcomes with the use of beta-blockers.• All-cause mortality: RR 1.24, 95% CI 0.99 to 1.54, 11,463 participants, low quality of evidence.Whereas no clear evidence of an effect was noted when all studies were analysed, restricting the meta-analysis to low risk of bias studies revealed a significant increase in all-cause mortality with the use of beta-blockers: RR 1.27, 95% CI 1.01 to 1.59, number needed to treat for an additional harmful outcome (NNTH) 189, 10,845 participants.• Cerebrovascular events: RR 1.59, 95% CI 0.93 to 2.71, 9150 participants, low quality of evidence.Whereas no clear evidence of an effect was found when all studies were analysed, restricting the meta-analysis to low risk of bias studies revealed a significant increase in cerebrovascular events with the use of beta-blockers: RR 2.09, 95% CI 1.14 to 3.82, NNTH 255, 8648 participants.Beta-blockers significantly reduced the occurrence of the following endpoints.• AMI: RR 0.73, 95% CI 0.61 to 0.87, NNTB 72, 10,958 participants, high quality of evidence.• Myocardial ischaemia: RR 0.43, 95% CI 0.27 to 0.70, NNTB seven, 1028 participants, moderate quality of evidence.• Supraventricular arrhythmias: RR 0.72, 95% CI 0.56 to 0.92, NNTB 111, 8794 participants, high quality of evidence.Beta-blockers significantly increased the occurrence of the following adverse events.• Hypotension: RR 1.50, 95% CI 1.38 to 1.64, NNTH 15, 10,947 participants, high quality of evidence.• Bradycardia: RR 2.24, 95% CI 1.49 to 3.35, NNTH 18, 11,083 participants, moderate quality of evidence.We found no clear evidence of an effect of beta-blockers on the following outcomes.• Ventricular arrhythmias: RR 0.64, 95% CI 0.30 to 1.33, 526 participants, moderate quality of evidence.• Congestive heart failure: RR 1.17, 95% CI 0.93 to 1.47, 9223 participants, moderate quality of evidence.• Length of hospital stay: mean difference -0.27 days, 95% CI -1.29 to 0.75, 601 participants, low quality of evidence.

AUTHORS' CONCLUSIONS

According to our findings, perioperative application of beta-blockers still plays a pivotal role in cardiac surgery , as they can substantially reduce the high burden of supraventricular and ventricular arrhythmias in the aftermath of surgery. Their influence on mortality, AMI, stroke, congestive heart failure, hypotension and bradycardia in this setting remains unclear.In non-cardiac surgery, evidence from low risk of bias trials shows an increase in all-cause mortality and stroke with the use of beta-blockers. As the quality of evidence is still low to moderate, more evidence is needed before a definitive conclusion can be drawn. The substantial reduction in supraventricular arrhythmias and AMI in this setting seems to be offset by the potential increase in mortality and stroke.

Oral clonidine versus gabapentin as premedicant for obtunding hemodynamic response to laryngoscopy and tracheal intubation

BACKGROUND

We compared the effects of oral clonidine and gabapentin as premedicant in obtunding hemodynamic response to laryngoscopy and intubation in normotensive patients undergoing elective surgery.

METHODS

A total of 100 patients of either sex enrolled in the study were randomly divided into two groups of 50 each. Group A patients received oral clonidine 200 μg and Group B patients received oral gabapentin 900 mg, 90 min prior to induction of anesthesia.

RESULTS

Both groups were matched for age, sex weight and intubation time. Anxiety score and sedation scores before induction were significantly better in Group A as compared with Group B. Heart rate rise was obtunded in Group A except at 1 min, as compared with Group B in which tachycardia persisted even at 3 and 5 min following intubation. Mean arterial pressure was maintained below baseline at all times in Group A as compared with Group B in which significant rise (+7.55%, P < 0.001) was seen at 1 min after intubation.

CONCLUSION

Oral clonidine provided good attenuation of hemodynamic response to laryngoscopy and intubation as compared with oral gabapentin.

Clinical Review: Is the Perioperative Use of β-Blockers Still Recommended? A Critical Review of Recent Controversies

The optimal role of β-adrenergic receptor blockade in the perioperative period remains unclear in patients at risk for cardiovascular events. Cardiovascular complications continue to be the most common cause of perioperative morbidity and mortality, and cardioprotective properties of β-blockers are widely recognized, yet the results of the clinical trials investigating the use of different β-blockers in the perioperative period are controversial. The discrepancy might be related to differences in the design of studies, use of different agents, administration by different routes, and continuation for different time intervals. Evidently, perioperative mortality and morbidity seem to be related to heart rate, and the majority of complications are related to β-blockers’ side effects. Based on the observations from different studies, we propose an algorithm for perioperative β blockade.

Perioperative beta blockers in patients having non-cardiac surgery: a meta-analysis

BACKGROUND

American College of Cardiology and American Heart Association (ACC/AHA) guidelines on perioperative assessment recommend perioperative beta blockers for non-cardiac surgery, although results of some clinical trials seem not to support this recommendation. We aimed to critically review the evidence to assess the use of perioperative beta blockers in patients having non-cardiac surgery.

METHODS

We searched Pubmed and Embase for randomised controlled trials investigating the use of beta blockers in non-cardiac surgery. We extracted data for 30-day all-cause mortality, cardiovascular mortality, non-fatal myocardial infarction, non-fatal stroke, heart failure, and myocardial ischaemia, safety outcomes of perioperative bradycardia, hypotension, and bronchospasm.

FINDINGS

33 trials included 12 306 patients. beta blockers were not associated with any significant reduction in the risk of all-cause mortality, cardiovascular mortality, or heart failure, but were associated with a decrease (odds ratio [OR] 0.65, 95% CI 0.54-0.79) in non-fatal myocardial infarction (number needed to treat [NNT] 63) and decrease (OR 0.36, 0.26-0.50) in myocardial ischaemia (NNT 16) at the expense of an increase (OR 2.01, 1.27-3.68) in non-fatal strokes (number needed to harm [NNH] 293). The beneficial effects were driven mainly by trials with high risk of bias. For the safety outcomes, beta blockers were associated with a high risk of perioperative bradycardia requiring treatment (NNH 22), and perioperative hypotension requiring treatment (NNH 17). We recorded no increased risk of bronchospasm.

INTERPRETATION

Evidence does not support the use of beta-blocker therapy for the prevention of perioperative clinical outcomes in patients having non-cardiac surgery. The ACC/AHA guidelines committee should soften their advocacy for this intervention until conclusive evidence is available.

Perioperative beta-blockers for preventing surgery-related mortality and morbidity: a systematic review and meta-analysis

BACKGROUND

Perioperative beta-blockers are suggested to reduce cardiovascular mortality, myocardial-ischemia/infarction, and supraventricular arrhythmias after surgery. We reviewed the evidence regarding the effectiveness of perioperative beta-blockers for improving patient outcomes after cardiac and noncardiac surgery.

METHODS

Eleven large databases were searched from the time of their inception until October 2005. Various online-resources were consulted for the identification of unpublished trials and conference abstracts. We included randomized, controlled trials comparing perioperative beta-blockers with either placebo or the standard-of-care. Of the 3680 retrieved titles, 69 met inclusion criteria for analysis. Odds ratios (OR) assuming random effects were computed in the absence of significant clinical heterogeneity.

RESULTS

Beta-blockers reduced the frequency of ventricular tachyarrhythmias [OR (cardiac surgery): 0.28, 95% CI 0.13-0.57; OR (noncardiac surgery): 0.56, 95% CI 0.21-1.45], atrial fibrillation/flutter [OR (cardiac surgery): 0.37, 95% CI 0.28-0.48], other supraventricular arrhythmias [OR (cardiac surgery): 0.25, 95% CI 0.18-0.35; OR (noncardiac surgery): 0.43, 95% CI 0.14-1.37], and myocardial ischemia [OR (cardiac surgery): 0.49, 95% CI 0.17-1.4; OR (noncardiac surgery): 0.38, 95% CI 0.21-0.69]. Length of hospitalization was not reduced [weighted mean difference (cardiac surgery): -0.35 days, 95% CI -0.77-0.07; weighted mean difference (noncardiac surgery): -5.59 days, 95% CI -12.22-1.04] and, in contrast to previous reports, beta-blockers did not reduce mortality [OR (cardiac surgery): 0.55, 95% CI 0.17-1.83; OR (noncardiac surgery): 0.78, 95% CI 0.33-1.87], and they had no influence on the occurrence of perioperative myocardial infarction [OR (cardiac surgery): 0.89, 95% CI 0.53-1.5; OR (noncardiac surgery): 0.59; 0.25-1.39].

CONCLUSIONS

Beta-blockers reduced perioperative arrhythmias and myocardial ischemia, but they had no effect on myocardial infarction, mortality, or length of hospitalization.

Acute peri-operative beta blockade in intermediate-risk patients

Peri-operative beta-blockade has been shown to reduce the incidence of postoperative cardio- vascular complications including cardiac death in high-risk non-cardiac surgical patients. However, the recent analysis by Lindenauer et al. suggests that it is inappropriate to administer beta-blockers blindly to all surgical patients. In an attempt to determine the appropriateness of peri-operative beta-blocker administration across patients with a spectrum of cardiovascular risks, we have examined studies of intermediate-risk patient groups (that is those undergoing intermediate risk surgery or those with a Lee Revised Cardiac Risk Score of < or =2). We analysed data from randomised prospective studies of the effects of acute peri-operative beta-blockade on the incidence of peri-operative myocardial ischaemia. By examining the demographics and surgical interventions in these patients, we have compared these studies with other studies of peri-operative silent myocardial ischaemia representing patients of similar risk. We thus estimated the expected long-term postoperative cardiovascular complication rate associated with myocardial ischaemia in these patients in terms of number needed to treat for ischaemia prevention and for prevention of major cardiovascular complications. Prevention of peri-operative myocardial ischaemia with acute beta-blockade in non-cardiac surgical patients with 1-2 RCRI clinical risk factors can be achieved with a number needed to treat of 10. It is not associated with a significant increase in drug associated side-effects. However, acute beta-blockade shows no real benefit in the prevention of major cardiovascular complications in intermediate risk non-vascular surgical patients with a number-needed-to-treat of 833. Vascular surgical patients undergoing intermediate-risk surgery may benefit from the protective effects of acute peri-operative beta-blockade, however, with a number-needed-to-treat of 68 it would require a randomised clinical trial of over 24,000 patients to prove their efficacy.

A meta-analysis of safety and effectiveness of perioperative beta-blocker use for the prevention of cardiac events in different types of noncardiac surgery

OBJECTIVE

Perioperative beta-blocker therapy has been proposed to improve outcome. Most of the trials conducted, however, lacked statistical power to evaluate the incidence of hard cardiac events and the relationship to the type of surgery. Therefore, we conducted a meta-analysis of all randomized controlled trials in which beta-blocker therapy was evaluated.

METHODS

An electronic search of published reports on Medline was undertaken to identify studies published between January 1980 and November 2004 in English language journals. All studies reported on at least one of three endpoints: perioperative myocardial ischemia, perioperative nonfatal myocardial infarction, and cardiac mortality. Type of surgery, defined as low, intermediate, and high risk according to the American College of Cardiology/American Heart Association guidelines, was noted.

RESULTS

In total, 15 studies were identified, which enrolled 1,077 patient. No significant differences were observed in baseline clinical characteristics between patients randomized to beta-blocker therapy and control/placebo. Beta-blocker therapy was associated with a 65% reduction in perioperative myocardial ischemia (11.0% vs. 25.6%; odds ratio 0.35, 95% confidence interval 0.23-0.54; P<0.001). Furthermore, a 56% reduction in myocardial infarction (0.5% vs. 3.9%, odds ratio 0.44, 95% confidence interval 0.20-0.97; P=0.04) and a 67% reduction (1.1% vs. 6.1%, odds ratio 0.33, 95% confidence interval 0.17-0.67; P=0.002) in the composite endpoint of cardiac death and nonfatal myocardial infarction were observed. No statistical evidence was observed for heterogeneity in the treatment effect in subgroups according to type of surgery (P for heterogeneity 0.2).

CONCLUSION

This meta-analysis shows that beta-blocker use in noncardiac surgical procedures is associated with a significant reduction of perioperative cardiac adverse events.

How strong is the evidence for the use of perioperative beta blockers in non-cardiac surgery? Systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To determine the effect of perioperative beta blocker treatment in patients having non-cardiac surgery.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Seven search strategies, including searching two bibliographic databases and hand searching seven medical journals. STUDY SELECTION AND OUTCOMES: We included randomised controlled trials that evaluated beta blocker treatment in patients having non-cardiac surgery. Perioperative outcomes within 30 days of surgery included total mortality, cardiovascular mortality, non-fatal myocardial infarction, non-fatal cardiac arrest, non-fatal stroke, congestive heart failure, hypotension needing treatment, bradycardia needing treatment, and bronchospasm.

RESULTS

Twenty two trials that randomised a total of 2437 patients met the eligibility criteria. Perioperative beta blockers did not show any statistically significant beneficial effects on any of the individual outcomes and the only nominally statistically significant beneficial relative risk was 0.44 (95% confidence interval 0.20 to 0.97, 99% confidence interval 0.16 to 1.24) for the composite outcome of cardiovascular mortality, non-fatal myocardial infarction, and non-fatal cardiac arrest. Methods adapted from formal interim monitoring boundaries applied to cumulative meta-analysis showed that the evidence failed, by a considerable degree, to meet standards for forgoing additional studies. The individual safety outcomes in patients treated with perioperative beta blockers showed a relative risk for bradycardia needing treatment of 2.27 (95% CI 1.53 to 3.36, 99% CI 1.36 to 3.80) and a nominally statistically significant relative risk for hypotension needing treatment of 1.27 (95% CI 1.04 to 1.56, 99% CI 0.97 to 1.66).

CONCLUSION

The evidence that perioperative beta blockers reduce major cardiovascular events is encouraging but too unreliable to allow definitive conclusions to be drawn.

Pharmacologic myocardial protection in patients undergoing noncardiac surgery: a quantitative systematic review

A number of drugs have been tested in clinical trials to decrease cardiac complications in patients undergoing noncardiac surgery. To compare the results of these studies, we conducted a quantitative systematic review. Medline, Embase, and Cochrane databases were searched for randomized trials that assessed myocardial ischemia, myocardial infarction, 30-day cardiac mortality, and adverse effects. Data were combined using a fixed-effect model and expressed as Peto odds ratios (OR) with 95% confidence interval (CI) and as numbers-needed-to-treat/harm (NNT/H). Twenty-one trials involving 3646 patients were included: 11 trials using beta-blockers (6 drugs; 866 patients), 6 clonidine or mivazerol (614 patients), 3 diltiazem or verapamil (121 patients), and 1 nitroglycerin (45 patients). All trials had an inactive control; there were no direct comparisons. beta-blockers decreased ischemic episodes during surgery (7.6% versus 20.2% with placebo; OR 0.32 [95% CI, 0.17-0.58]; NNT 8) and after surgery (15.2% versus 27.9% with control; OR 0.46 [95% CI, 0.26-0.81]; NNT 8). alpha(2)-agonists decreased ischemia during surgery only (19.4% versus 32.8%; OR 0.47 [95% CI, 0.33-0.68]; NNT 7). beta-blockers reduced the risk of myocardial infarction (0.9% versus 5.2%; OR 0.19 [95% CI, 0.08-0.48]; NNT 23) but only when 2 trials with high-risk patients were included. The effect of alpha(2)-agonists on myocardial infarction was not significant (6.1% versus 7.3%; OR 0.85 [95% CI, 0.62-1.14]). beta-blockers significantly decreased the risk of cardiac death from 3.9% to 0.8% (OR 0.25 [95% CI, 0.09-0.73], NNT 32). alpha(2)-agonists significantly decreased the risk of cardiac death from 2.3% to 1.1% (OR 0.50 [95% CI, 0.28-0.91], NNT 83). For calcium channel blockers and nitroglycerin, evidence of any benefit was lacking. The most common adverse effect was bradycardia, which occurred in 24.5% of patients receiving a beta adrenergic blocker versus 9.1% of controls (OR 3.76 [95% CI, 2.45-5.77], NNH 6).

Esmolol blunts the haemodynamic responses to tracheal intubation in treated hypertensive patients

PURPOSE

To compare the ability of different bolus doses of esmolol to blunt the haemodynamic effects of laryngoscopy and tracheal intubation in treated hypertensive patients.

METHODS

In this randomised, double-blind placebo controlled study, 45 ASA II patients, treated for essential hypertension with drugs other than beta blockers, were divided into three groups of 15 patients each. Patients in different groups either received 20 ml normal saline (Group P), or 100 mg esmolol (Group E100) or 200 mg esmolol (Group E200) as a single bolus intravenous dose before laryngoscopy and intubation. Systolic, diastolic and mean arterial pressure and heart rate were monitored for up to 10 min following intubation and were compared with respective basal readings as well as across groups.

RESULTS

Esmolol alone reduced systolic arterial pressure (P < 0.01 in Group E100 and P < 0.001 in Group E200) and heart rate (P < 0.001). Though there was an increase in arterial pressure and heart rate in the control group, esmolol 100 mg maintained arterial pressure and heart rate at levels comparable to basal values throughout the study (P > 0.05). Patients receiving esmolol 200 mg had lower values (P < 0.001) than their basal readings during most of the post-intubation study period.

CONCLUSION

Esmolol 100 mg given as bolus, is effective as well as safe in blunting the haemodynamic responses to laryngoscopy and tracheal intubation in treated hypertensive patients.

VARIABLE RATE IV INFUSION OF MORPHINE AND HAEMODYNAMIC RESPONSE TO LARYNGOSCOPY AND TRACHEAL INTUBATION

Haemodynamic response to laryngoscopy and tracheal intubation was studied in two groups of 45 patients each. Group I patients received variable rate infusion of morphine for 30 minutes followed by intravenous (IV) bolus dose of diazepam. Group II patients received intramuscular morphine as preanaesthetic premedication and preinduction IV bolus dose of diazepam. The method of induction of GA was same in both the groups. Systolic and diastolic blood pressure (SBP and DBP) mean arterial pressure and pulse-rate were recorded at intubation and at different time intervals upto 10 minutes after intubation. In group I patients, there was no statistically significant increase in pulse-rate and SBP following intubation but transient significant increase in DBP. In group II patients, there was statistically significant increase in pulse-rate, SBP and DBP upto 3 minutes post-intubation. Thus IV infusion of morphine in combination with IV bolus dose of diazepam proved more effective in attenuating haemodynamic response to tracheal intubation.

Isosorbide dinitrate spray. Attenuation of cardiovascular responses to laryngoscopy and intubation

We evaluated the efficacy of isosorbide dinitrate buccal spray (Isomack) in attenuating the cardiovascular response to laryngoscopy and tracheal intubation in 60 patients undergoing elective surgery under general anaesthesia. Patients were allocated to one of three groups of 20 patients each. Group 1 patients were administered placebo buccal spray 90 s before induction of anaesthesia. Groups 2 and 3 had isosorbide dinitrate spray 30 and 90 s before induction of anaesthesia. Systolic, diastolic and mean arterial pressures and heart rate were monitored. After the spray, group 3 patients had a significant decrease in systolic arterial pressure (p less than 0.01). At 1 min after intubation, systolic, diastolic and mean arterial pressures showed a significant increase in group 1 patients (24.9 mmHg, 14.2 mmHg and 18.7 mmHg respectively). In contrast, groups 2 and 3 showed a significant decrease in these parameters (p less than 0.01). Although significant tachycardia was present following intubation in all the three groups, the degree of tachycardia was greater in groups 2 and 3 (p less than 0.01).

A comparative study of five different techniques to reduce left ventricular dysfunction during endotracheal intubation

Thirty-five non-selected, consenting patients were studied during induction of anesthesia before coronary artery bypass grafting. Anesthesia was induced with diazepam, thiopentone and fentanyl, followed by pancuronium. Before induction, 200 MBq Tc 99 m - HSA was given i.v. and ejection fraction (EF) of the left ventricle was measured with a collimated single-crystal probe. The patients were allocated to five groups (seven patients in each) treated with: Group A: nitroglycerin i.v. bolus 4 micrograms x kg-1 given 30-60 s before laryngoscopy; Group B: nitroglycerin i.v. in continuous infusion, 1 micrograms x kg-1 x min-1 started before induction; Group C: two-stage topical anesthesia of the vallecula region and larynx with lidocain; Group D: a combination of nitroglycerin and topical anesthesia (as in Group B and C); and Group E: propranolol i.v. 0.01 mg x kg-1 given 5 min before intubation. All groups reacted in the same way during induction of anesthesia up to the point of laryngoscopy. End-diastolic volume and systemic arterial pressure decreased while cardiac index remained unchanged and EF increased. During laryngoscopy and intubation, however, differences between the groups were evident. Nitroglycerin i.v. as a bolus effectively prevented a reduction in EF and an increase in left ventricular volume. In addition to these beneficial hemodynamic effects, there was a moderate increase in heart rate and a reduction of stroke index. Continuous infusion of nitroglycerin and propranolol i.v. had no effect, since EF fell and left ventricular volume increased. Patients receiving topical anesthesia demonstrated a blunted response to endotracheal intubation with a moderate decrease in EF and an unchanged (Group C) or slightly increased (Group D) left ventricular volume.

Cardiovascular effects of intravenous clonidine. Partial attenuation of the pressor response to intubation by clonidine

The effect of clonidine on the pressor and heart rate response to tracheal intubation was studied in a placebo-controlled, randomised, double-blind trial. Thirty patients were pretreated with either clonidine 1.25 micrograms/kg, or clonidine 0.625 microgram/kg or an equivalent volume of normal saline, given intravenously 15 minutes before induction of anaesthesia. The attenuation of the pressor response to intubation of both clonidine groups was statistically significant compared to the saline group. Neither dose of clonidine completely abolished the increase in either heart rate or blood pressure. There was no difference in attenuation between the clonidine treatments; this indicated that the lower dose may be the more appropriate.

Can esmolol manage surgically-induced tachycardia? Bolus esmolol treatment of intra-operative tachycardia due to surgical stimulation

A double-blind, randomised study was conducted to examine the efficacy of a single bolus dose of esmolol in treating surgically-induced tachycardia. Anaesthetic technique was identical in all patients, and consisted of premedication with midazolam and glycopyrronium, induction with thiopentone followed by suxamethonium, tracheal intubation, and maintenance with isoflurane 0.6% (end-tidal) and 60% nitrous oxide in oxygen. Forty-eight patients developed a heart rate of greater than 95 beats/minute or 20% more than pre-induction values at an average time of 34 minutes after tracheal intubation and received placebo (15 patients), esmolol 50 mg (16 patients), or esmolol 100 mg (17 patients). Controlled intervention was instituted if heart rate or blood pressure was not adequate. Both 50 and 100 mg of esmolol resulted in lower heart rates compared to placebo (p less than 0.05), with no difference between the two esmolol groups (p greater than 0.05). Patients who received placebo had more episodes of medical intervention than those given esmolol (p less than 0.05). No adverse effects occurred in any patient.

Attenuation of hemodynamic responses to rapid sequence induction and intubation in healthy patients with a single bolus of esmolol

The effectiveness of a single preinduction intravenous (IV) bolus of esmolol in blunting hemodynamic responses to rapid sequence induction and tracheal intubation was evaluated. In a randomized double-blind study, 32 ASA I and II healthy patients scheduled for surgery were monitored with electrocardiography (EKG) lead V5, arterial cannulation, and impedance cardiography. After preoxygenation and a priming dose of vecuronium (0.01 mg/kg), patients received either saline (n = 12), esmolol 100 mg (n = 10), or esmolol 200 mg (n = 10) as an IV bolus (20 ml volume). This procedure was immediately followed by a 5 ml IV saline flush, cricoid pressure, thiopental sodium 5 mg/kg, and succinylcholine 1.5 mg/kg. Patients receiving 200 mg of esmolol had a 50% reduction in the usual tachycardia associated with induction and a greater decline in systolic blood pressure (SP) (by 50%) prior to intubation as compared with the placebo group (p less than 0.05). The increase in diastolic blood pressure (DP) and the reduction in stroke volume (SV) produced by induction and intubation were similar in all the groups. Plasma norepinephrine levels at 1.5 minutes after intubation increased in the esmolol groups about 130% above that measured in the placebo group. This finding was associated with a more gradual return of peripheral resistance to baseline following tracheal intubation. However, both doses of esmolol effectively attenuated heart rate (HR), SP, and rate pressure product (RPP) increases (p less than 0.05 vs placebo) produced by laryngoscopy and tracheal intubation.

Comparison of anxiety before induction of anaesthesia in the anaesthetic room or operating theatre

Anxiety before induction of anaesthesia was studied in 100 patients who were allocated randomly to one of two groups. Patients in one group were anaesthetised in an anaesthetic room and those in the other group were anaesthetised inside the operating theatre. Both subjective and objective induces of anxiety were used in the comparison. Other factors that contributed to anxiety were assessed by a simple questionnaire. There was no significant difference in the level of anxiety between the two groups. The site of induction did not emerge as a major contributory factor to anxiety. The advantages and disadvantages of anaesthetic rooms are discussed.

Effects of beta-adrenoceptor antagonism on the cardiovascular and catecholamine responses to tracheal intubation

The catecholamine and cardiovascular responses to laryngoscopy and tracheal intubation were studied in 20 patients who underwent elective gynaecological surgery and who were allocated randomly to receive either practolol 10 mg or saline intravenously prior to induction of anaesthesia. Anaesthesia was induced with fentanyl and thiopentone; atracurium was administered and the lungs were ventilated artificially with 67% nitrous oxide in oxygen. Tracheal intubation was performed when muscle relaxation was adequate. Arterial pressure, heart rate, plasma noradrenaline and adrenaline concentrations were measured before and after tracheal intubation. A significant increase in catecholamine concentrations occurred in both groups in response to tracheal intubation but the magnitude of the increase in adrenaline was greater in the practolol group. There were no significant differences in arterial pressure or heart rate changes between the groups. We conclude that pretreatment with practolol is of no value in the attenuation of the hypertensive response to direct laryngoscopy and tracheal intubation in previously normotensive patients.

Esmolol: a titratable short-acting intravenous beta blocker for acute critical care settings

Esmolol (Brevibloc) is an intravenous, short-acting, titratable, cardioselective beta blocker with a very rapid onset and offset of action (t1/2 = 9.2 minutes). Esmolol-induced beta blockade can be maintained as long as infusion is continued. It exhibits neither intrinsic sympathomimetic activity nor significant membrane-stabilizing activity. It is rapidly metabolized by an esterase in the erythrocyte cytosol to an inactive acid metabolite. Its hemodynamic and electrophysiologic effects are similar to those of other beta blockers. Unlike the effects of other beta blockers, however, the effects of esmolol dissipate rapidly to baseline within 30 minutes after its discontinuation. Evidence obtained from clinical studies indicates that esmolol is effective and safe in reducing the ventricular rate in patients with supraventricular tachyarrhythmias, and in reducing the heart rate in patients with acute myocardial infarction and/or unstable angina. Esmolol has also been shown to be effective and safe in attenuating the tachycardia and hypertension seen during the intraoperative period. Data from postoperative patients indicate that esmolol is ideal as sole-agent therapy for the treatment of moderate postoperative hypertension associated with a hyperdynamic state. The short duration of action and titratability of esmolol make it an ideal drug for use in patients in whom the clinical need for beta blockade is limited in duration, and it offers additional safety in patients in whom beta blockade is beneficial; however, it might be precluded because of coexisting contraindications. To date, experience with esmolol in over 1200 patients has been gathered, and the adverse effect profile is basically similar to that reported here.

Topical nitroglycerin. A safeguard against pressor responses to tracheal intubation

In order to attenuate the pressor response to intubation of the trachea we have studied the effects of 2% nitroglycerin ointment rubbed on the forehead approximately 12 minutes prior to intubation. A double blind, randomized design was used in 56 consecutive patients. Of these, 30 patients received the ointment while 26 patients formed the control group. The maximum rise in the systolic arterial pressure was significantly lower (p less than 0.001) in the group (7.66 mmHg, 6.2%) as compared to the control group (25.7 mmHg, 20.2%). The rise in arterial pressure persisted for up to 4 minutes in the control group, but lasted for only one minute in the nitroglycerine group. The pulse rate, however, increased in both groups to an equal extent. We have found the application of 2% nitroglycerine ointment to be a safe, inexpensive, comfortable and effective means of attenuating the pressor response to intubation of the trachea.

Cardiovascular and neuromuscular effects of esmolol during induction of anesthesia

Sixteen subjects scheduled for surgical procedures under general anesthesia participated in an investigation of the effects of esmolol on the transient hypertension and tachycardia that was observed during endotracheal intubation and on the duration of succinylcholine-induced neuromuscular blockade. In eight subjects, infusion of esmolol was begun five minutes before induction of anesthesia and continued for 12 minutes after induction. In the remaining subjects, an equivalent volume of solvent (D5W) was infused for 12 minutes. Infusion of esmolol significantly attenuated the cardioacceleration observed during intubation without any significant effect on the pressor effects of the procedure. Esmolol delayed the recovery from succinylcholine-induced neuromuscular blockade by less than three minutes. The mechanism of this delay remains to be investigated, although such a delay does not have clinical significance. Esmolol-induced attenuation of the tachycardia seen during intubation may offer a protective effect on the myocardium, especially in elderly subjects and patients with coronary artery disease.

Esmolol and the adrenergic response to perioperative stimuli

Esmolol, an ultra-short-acting, cardioselective, beta-receptor blocking agent, has been developed for use in clinical conditions requiring controlled beta-receptor blockade. Its esterase-induced rapid metabolic inactivation and resulting brief pharmacologic effect provides control over the magnitude and duration of beta-receptor blockade. In placebo-controlled clinical trials, the effects of infusion of esmolol on the sympathetically mediated hemodynamic responses to stressful events during the perioperative period were evaluated in patients scheduled for surgical procedures under general anesthesia. In patients undergoing either noncardiac or cardiac surgical procedures, esmolol was effective in attenuating tachycardia that is normally seen during induction of anesthesia, laryngoscopy and endotracheal intubation, or sternotomy and aortic dissection by reducing the hemodynamic stress on the heart with negligible adverse effects. This much-desired cardioprotective effect of esmolol will be of special value to patients with coronary artery disease and patients with an unstable cardiovascular status who are undergoing major surgical procedures with general anesthesia.

Electrocardiographical changes in the peri-operative period. A pilot study

The value of continuous electrocardiogram recording in the peri-operative period has been examined. In a group of 15 patients, 14 developed changes two of which persisted into the postoperative period. Dysrhythmias, ST segment and T-wave changes occurred frequently. Continuous recording is of potential benefit in the study of cardiovascular disease and therapy in the peri-operative period.

The effect of labetalol on the cardiovascular, hyperglycaemic and adrenocortical responses to surgery

The effects of a single intravenous bolus of labetalol (0.5 mg/kg) on the cardiovascular, hyperglycaemic and adrenocortical responses to major colonic surgery were studied in five patients. Results were compared with five patients who received the same anaesthetic and had similar operations performed but who did not receive labetalol. It was observed that labetalol reduced the rises in heart rate and rate-pressure product that occur at the time of skin incision but that it did not reduce the rise in mean arterial pressure. The rises in blood glucose and plasma cortisol were significantly less in the labetalol group after 30 minutes of surgery (p less than 0.05).

The use of propranolol in rapid sequence anaesthetic induction: optimal time interval for pretreatment

Forty patients ASA physical status I-III were selected and divided into four groups. Group I, Control, received saline pretreatment five minutes prior to rapid sequence induction and intubation, while Groups II, III and IV received propranolol 0.01 mg X kg-1 IV two, five or eight minutes prior to induction and intubation. Measurements of heart rate (HR), arterial blood pressure (ABP) were recorded as baseline values and at one, two, five, eight and 20 minutes, and simultaneous venous samples were withdrawn for propranolol levels. Calculated rate pressure product (RPP) showed best haemodynamic control in Group III. Serum propranolol levels were under 5 ng X ml-1 in Group III and undetectable in Group IV. Our data show that the optimal time interval between IV propranolol administration and intubation was five minutes.

The use of labetalol in anaesthesia

1 Observed and possible roles for the use of labetalol in anaesthesia are reviewed. 2 When used together with halothane inhalation anaesthesia, satisfactory conditions are achieved for safe hypotensive anaesthesia: (a) Labetalol and halothane have additive hypotensive effects. (b) The usual dose of labetalol is 25 mg intravenously together with 1% halothane. (c) The duration of hypotension can be controlled in the presence of halothane; withdrawal leads to rapid recovery of pre-surgery blood pressure. (d) High doses of halothane (3%) with labetalol predispose to the myocardial depressant effects of halothane and undesirable reductions in myocardial performance. 3 As it is now seen to be important to reduce the blood pressure before anaesthesia and surgery in hypertensive patients, then labetalol is likely to be satisfactory either by the intravenous route for immediate reduction or for less urgent reduction of raised arterial pressure by the oral route. 4 It is known that anaesthesia (for example, laryngoscopy) and surgery provoke hypertensive responses which are particularly undesirable in the patient with pre-existent myocardial ischaemia. In such cases it is likely that previous treatment with labetalol will satisfactorily modify unwanted hypertensive and cardiovascular responses.