Comparative evaluation of intrathecal midazolam and low dose clonidine: efficacy, safety and duration of analgesia. A randomized, double blind, prospective clinical trial

Alpha-2 adrenergic agonists for the prevention of cardiac complications among adults undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may help prevent postoperative cardiac complications.

OBJECTIVES

To determine the efficacy and safety of α-2 adrenergic agonists for reducing mortality and cardiac complications in adults undergoing cardiac surgery and non-cardiac surgery.

SEARCH METHODS

We searched CENTRAL (2017, Issue 4), MEDLINE (1950 to April Week 4, 2017), Embase (1980 to May 2017), the Science Citation Index, clinical trial registries, and reference lists of included articles.

SELECTION CRITERIA

We included randomized controlled trials that compared α-2 adrenergic agonists (i.e. clonidine, dexmedetomidine or mivazerol) against placebo or non-α-2 adrenergic agonists. Included trials had to evaluate the efficacy and safety of α-2 adrenergic agonists for preventing perioperative mortality or cardiac complications (or both), or measure one or more relevant outcomes (i.e. death, myocardial infarction, heart failure, acute stroke, supraventricular tachyarrhythmia and myocardial ischaemia).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials. We evaluated included studies using the Cochrane 'Risk of bias' tool, and the quality of the evidence underlying pooled treatment effects using GRADE methodology. Given the clinical heterogeneity between cardiac and non-cardiac surgery, we analysed these subgroups separately. We expressed treatment effects as pooled risk ratios (RR) with 95% confidence intervals (CI).

MAIN RESULTS

We included 47 trials with 17,039 participants. Of these studies, 24 trials only included participants undergoing cardiac surgery, 23 only included participants undergoing non-cardiac surgery and eight only included participants undergoing vascular surgery. The α-2 adrenergic agonist studied was clonidine in 21 trials, dexmedetomidine in 24 trials and mivazerol in two trials.In non-cardiac surgery, there was high quality evidence that α-2 adrenergic agonists led to a similar risk of all-cause mortality compared with control groups (1.3% with α-2 adrenergic agonists versus 1.7% with control; RR 0.80, 95% CI 0.61 to 1.04; participants = 14,081; studies = 16). Additionally, the risk of cardiac mortality was similar between treatment groups (0.8% with α-2 adrenergic agonists versus 1.0% with control; RR 0.86, 95% CI 0.60 to 1.23; participants = 12,525; studies = 5, high quality evidence). The risk of myocardial infarction was probably similar between treatment groups (RR 0.94, 95% CI 0.69 to 1.27; participants = 13,907; studies = 12, moderate quality evidence). There was no associated effect on the risk of stroke (RR 0.93, 95% CI 0.55 to 1.56; participants = 11,542; studies = 7; high quality evidence). Conversely, α-2 adrenergic agonists probably increase the risks of clinically significant bradycardia (RR 1.59, 95% CI 1.18 to 2.13; participants = 14,035; studies = 16) and hypotension (RR 1.24, 95% CI 1.03 to 1.48; participants = 13,738; studies = 15), based on moderate quality evidence.There was insufficient evidence to determine the effect of α-2 adrenergic agonists on all-cause mortality in cardiac surgery (RR 0.52, 95% CI 0.26 to 1.04; participants = 1947; studies = 16) and myocardial infarction (RR 1.01, 95% CI 0.43 to 2.40; participants = 782; studies = 8), based on moderate quality evidence. There was one cardiac death in the clonidine arm of a study of 22 participants. Based on very limited data, α-2 adrenergic agonists may have reduced the risk of stroke (RR 0.37, 95% CI 0.15 to 0.93; participants = 1175; studies = 7; outcome events = 18; low quality evidence). Conversely, α-2 adrenergic agonists increased the risk of bradycardia from 6.4% to 12.0% (RR 1.88, 95% CI 1.35 to 2.62; participants = 1477; studies = 10; moderate quality evidence), but their effect on hypotension was uncertain (RR 1.19, 95% CI 0.87 to 1.64; participants = 1413; studies = 9; low quality evidence).These results were qualitatively unchanged in subgroup analyses and sensitivity analyses.

AUTHORS' CONCLUSIONS

Our review concludes that prophylactic α-2 adrenergic agonists generally do not prevent perioperative death or major cardiac complications. For non-cardiac surgery, there is moderate-to-high quality evidence that these agents do not prevent death, myocardial infarction or stroke. Conversely, there is moderate quality evidence that these agents have important adverse effects, namely increased risks of hypotension and bradycardia. For cardiac surgery, there is moderate quality evidence that α-2 adrenergic agonists have no effect on the risk of mortality or myocardial infarction, and that they increase the risk of bradycardia. The quality of evidence was inadequate to draw conclusions regarding the effects of alpha-2 agonists on stroke or hypotension during cardiac surgery.

Comparison of intrathecal clonidine and magnesium sulphate used as an adjuvant with hyperbaric bupivacaine in lower abdominal surgery

Background and Aims:

Use of various adjuvants to spinal anaesthesia is a well-known modality to provide intra- and post-operative analgesia. This study was designed to evaluate and compare the analgesic efficacy of clonidine and magnesium when used as an additive to intrathecal 0.5% hyperbaric bupivacaine.

Methods:

Ninety patients of the American Society of Anesthesiologists’ physical status grade I or II, scheduled for lower abdominal surgery under spinal anaesthesia, were randomly allocated into three groups. Group B received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL of normal saline, Group C received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL (30 μg) of clonidine and Group M received 3 mL of 0.5% hyperbaric bupivacaine with 1 mL (50 mg) magnesium sulphate. The primary outcome variable was duration of analgesia and secondary outcome variables included onset and duration of sensory and motor block, sedation level and adverse effects. Data were analysed with ANOVA, Kruskal–Wallis and Chi-square tests.

Results:

The time to first rescue analgesia was significantly (P < 0.01) longer in the Group C (330.7 ± 47.7 min) than both Groups. Group M (246.3 ± 55.9 min) showed significantly prolonged analgesia than Group B (134.4 ± 17.9 min). Group C and Group M showed significantly prolonged duration of both sensory and motor block compared to Group B.

Conclusion:

Intrathecal clonidine added to bupivacaine prolongs the duration of post-operative analgesia, and hastens the onset and prolongs the duration of sensory and motor block compared to magnesium or controls.

B. S, Pandarpurkar S, Jajee P. Intrathecal Midazolam as an Adjuvant in Pregnancy-Induced Hypertensive Patients Undergoing an Elective Caesarean Section: A Clinical Comparative Study

Background

A pain-free postoperative period is essential following a caesarean section so new mothers may care for and bond with their neonates. Intrathecal adjuvants are often administered during this procedure to provide significant analgesia, but they may also have bothersome side effects. Intrathecal midazolam produces effective postoperative analgesia with no significant side effects.

Objectives

This prospective, randomized, double-blind study was designed to compare the analgesic efficacy and safety of intrathecal midazolam vs. plain bupivacaine as an adjunct to bupivacaine in pregnancy-induced hypertension patients scheduled for elective caesarean section.

Methods

Sixty patients diagnosed with pregnancy-induced hypertension on regular treatment who were scheduled for a caesarean section were randomly allocated into two groups: a control group (Group BC, n = 30) and a midazolam group (Group BM, n = 30). Both groups received 10 mg (2 mL) of 0.5% hyperbaric bupivacaine. Group BC received 0.4 mL of distilled water, while group BM received 0.4 mL (2 mg) of midazolam intrathecally. The duration of postoperative analgesia, analgesic requirements during the first 24 hours after surgery, onset times and durations of sensory and motor blocks, incidence of hypotension, vasopressor requirements, and side effects were recorded.

Results

Postoperative analgesia was significantly longer in the midazolam group compared to the control group (201.5 minutes vs. 357.6 minutes). The mean onset times of the sensory and motor blocks were significantly faster (P < 0.01) in the midazolam group compared to the control group. The mean times to attain the maximum sensory level and motor blocks were also significantly faster in the midazolam group compared to the control group (P < 0.05). The incidence of hypotension was 6.6% in the midazolam group and 36.6% in the control group, which was highly significant. In addition, the number of patients with side effects was significantly lower in the midazolam group compared to the control group.

Conclusions

Intrathecal midazolam 2 mg provides significantly longer and effective postoperative analgesia with no side effects.

Analgesic Effect of Clonidine Added to Bupivacaine in Spinal Anesthesia for Cruciate Ligament Repair

Background:

Several researchers have suggested that addition of local anesthetics to spinal anesthesia increases the duration of post-operative analgesia.

Objectives:

This study sought to assess the effect of addition of clonidine to bupivacaine in spinal anesthesia on analgesia after cruciate ligament repair.

Patients and Methods:

This double-blind clinical trial was conducted on 50 American Society of Anesthesiologists (ASA) class I or II patients who were candidates for cruciate ligament repair. Patients were randomly assigned to two groups; one group received 15 mg of bupivacaine (group B) and the other 15 mg of bupivacaine plus clonidine (75 µg, group BC). The two groups were compared in terms of post-operative analgesia and related factors using the SPSS software version 20.

Results:

All patients were males with a mean age of 24.9 years in group B, and 25.2 years in group BC (P > 0.05). In group BC, time lapse to request analgesics was 160 minutes longer and the Visual Analog Scale (VAS) at this time was 0.3 units less than group B. The time to regression of sensory block by two dermatomes was seven minutes longer, VAS in the recovery room was 1 unit less and Bromage scale in the recovery room and ward was 0.6 and 0.9 units more, respectively in the BC group. Hypotension and ephedrine usage was 36% more in the BC group (P < 0.05).

Conclusions:

Clonidine plus bupivacaine can increase the duration of motor and sensory block in arthroscopic cruciate ligament repair under spinal anesthesia. However, due to significant hemodynamic changes, further studies are required to determine a safer dose.

Midazolam in Subarachnoid Block: Current Evidence

Midazolam, despite of being the commonest benzodiazepine used in anaesthesia and perioperative care, is a relatively newer addition to the list of adjuvant used in subarachnoid block. Midazolam causes spinally mediated analgesia and the segmental analgesia produced by intrathecal midazolam is mediated by the benzodiazepine-GABA receptor complex. Initial animal studies questioned the safety of intrathecal midazolam in terms of possible neurotoxicity. However subsequent clinical studies also failed to show any neurotoxicity of high dose midazolam even on long-term use. Addition of intrathecal midazolam to bupivacaine significantly improves the duration and quality of spinal anaesthesia and provides prolonged perioperative analgesia without any significant side effects. Clinical studies also reported its safety and efficacy in pregnant women, but some studies also reported mild sedation with intrathecal midazolam. It is also reported to decrease the incidence of PONV. Intrathecal midazolam does not have any clinically significant effect on perioperative hemodynamics.

The effect of adjuvant midazolam compared with fentanyl on the duration of spinal anesthesia with 0.5% bupivacaine in opium abusers

Background

There are a number of adjuvants to be used for local anesthetics in spinal block. The aim of this study was to demonstrate the possible effect of intrathecal midazolam compared with bupivacaine as adjuvants in spinal anesthesia with bupivacaine in chronic opium abuses.

Methods

In a double blind, randomized clinical trial, 90 opium abuser patients undergoing lower limb orthopedic surgery were selected and randomly assigned into 3 groups (30 cases each). The patients received 15 mg plain bupivacaine, or 15 mg bupivacaine plus 25 mcg fentanyl or 15 mg bupivacaine plus 1 mg midazolam, intrathecally.

Results

The duration of anesthesia was much longer in the bupivacaine-midazolam group than the bupivacaine-fentanyl group; both were longer than the plain bupivacaine group (P < 0.05).

Conclusions

Subarachnoid injection of adjuvant midazolam or fentanyl with plain 0.5% bupivacaine in opium abusers in lower limb orthopedic surgery increases the duration of sensory block. Therefore midazolam is more effective than fentanyl in such cases.