Analgesic Efficacy of Two Doses of Intrathecal Midazolam With Bupivacaine in Patients Undergoing Cesarean Delivery:

Pharmacological and clinical implications of local anaesthetic mixtures: a narrative review

Various techniques have been explored to prolong the duration and improve the efficacy of local anaesthetic nerve blocks. Some of these involve mixing local anaesthetics or adding adjuncts. We did a literature review of studies published between 01 May 2011 and 01 May 2021 that studied specific combinations of local anaesthetics and adjuncts. The rationale behind mixing long- and short-acting local anaesthetics to hasten onset and extend duration is flawed on pharmacokinetic principles. Most local anaesthetic adjuncts are not licensed for use in this manner and the consequences of untested admixtures and adjuncts range from making the solution ineffective to potential harm. Pharmaceutical compatibility needs to be established before administration. The compatibility of drugs from the same class cannot be inferred and each admixture requires individual review. Precipitation on mixing (steroids, non-steroidal anti-inflammatory drugs) and subsequent embolisation can lead to serious adverse events, although these are rare. The additive itself or its preservative can have neurotoxic (adrenaline, midazolam) and/or chondrotoxic properties (non-steroidal anti-inflammatory drugs). The prolongation of block may occur at the expense of motor block quality (ketamine) or block onset (magnesium). Adverse effects for some adjuncts appear to be dose-dependent and recommendations concerning optimal dosing are lacking. An important confounding factor is whether studies used systemic administration of the adjunct as a control to accurately identify an additional benefit of perineural administration. The challenge of how best to prolong block duration while minimising adverse events remains a topic of interest with further research required.

Reduction in labor pain by intrathecal midazolam as an adjunct to sufentanil

BACKGROUND

Anesthesia today has strived to decrease labor pain in a tolerable and controllable fashion. Intrathecal midazolam has been introduced as an adjunct to analgesics. The study was planned to assess the efficacy, safety and duration of analgesia produced by intrathecal midazolam adjunct to sufentanil in decreasing labor pain.

METHODS

In a randomized clinical trial 80 parturient included in the study. The two groups were matched for age, cervical dilation, gravid, gestational age, and other demographic characteristics. Combination of sufentanil and midazolam administered intrathecally to experimental group and compared to sufentanil group. Time to reach maximum block, and pain score was measured and recorded.

RESULTS

Groups were matched for age and weight and other demographic characteristic. No significant adverse effect was seen in both groups including decrease in Apgar score. Duration of analgesia was 92.0 ± 12.7 in sufentanil group and 185.2 ± 15.2 minutes in midazolam and sufentanil group which was significantly different (P = 0.002). Numeric rating scale score was significantly lower in midazolam group compare to sufentanil group at 120 min (P = 0.01), 150 min (P = 0.0014), and 180 min (P = 0.001).

CONCLUSIONS

Intrathecal midazolam as an adjunct to opioid could significantly enhance analgesia in labor pain with no significant adverse effect. Intrathecal injection of midazolam is an appropriate alternative to parenteral or epidural analgesia in small hospital settings.

Interventions at caesarean section for reducing the risk of aspiration pneumonitis

BACKGROUND

Aspiration pneumonitis is a syndrome resulting from the inhalation of gastric contents. The incidence in obstetric anaesthesia has fallen, largely due to improved anaesthetic techniques and the increased use of regional anaesthesia at caesarean section. However, aspiration pneumonitis is still a cause of maternal morbidity and mortality, and it is important to use effective prophylaxis.

OBJECTIVES

To determine whether interventions given prior to caesarean section reduce the risk of aspiration pneumonitis in women with an uncomplicated pregnancy.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 April 2013).

SELECTION CRITERIA

Randomised controlled trials were included. Quasi-randomised trials were excluded.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked. Fixed-effect meta-analysis was used to combine data where it was reasonable to assume that studies were estimating the same underlying treatment effect. If substantial clinical or statistical heterogeneity was detected, we used random-effects analysis to produce an overall summary.

MAIN RESULTS

Thirty-two studies were included in this review. However, only 22 studies, involving 2658 women, provided data for analysis. All the women in the included studies had a caesarean section under general anaesthesia. The studies covered a number of comparisons, but were mostly small and of unclear or poor quality.When compared with no treatment or placebo, there was a significant reduction in the risk of intragastric pH < 2.5 with antacids (risk ratio (RR) 0.17, 95% confidence interval (CI) 0.09 to 0.32, two studies, 108 women), H2 antagonists (RR 0.09, 95% CI 0.05 to 0.18, two studies, 170 women) and proton pump antagonists (RR 0.26, 95% CI 0.14 to 0.46, one study 80 women). H2 antagonists were associated with a reduced the risk of intragastric pH < 2.5 at intubation when compared with proton pump antagonists (RR 0.39, 95% CI 0.16 to 0.97, one study, 120 women), but compared with antacids the findings were unclear. The combined use of 'antacids plus H2 antagonists' was associated with a significant reduction in the risk of intragastric pH < 2.5 at intubation when compared with placebo (RR 0.02, 95% CI 0.00 to 0.15, one study, 89 women) or compared with antacids alone (RR 0.12, 95% CI 0.02 to 0.92, one study, 119 women).

AUTHORS' CONCLUSIONS

The quality of the evidence was poor, but the findings suggest that the combination of antacids plus H2 antagonists was more effective than no intervention, and superior to antacids alone in preventing low gastric pH. However, none of the studies assessed potential adverse effects or substantive clinical outcomes. These findings are relevant for all women undergoing caesarean section under general anaesthesia.

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.

Interventions for preventing nausea and vomiting in women undergoing regional anaesthesia for caesarean section

BACKGROUND

Nausea and vomiting are distressing symptoms which are experienced commonly during caesarean section under regional anaesthesia and can also occur in the period following the procedure. 

OBJECTIVES

To assess the efficacy of pharmacological and non-pharmacological interventions given prophylactically to prevent nausea and vomiting in women undergoing regional anaesthesia for caesarean section.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (27 February 2012) and reference lists of identified studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and excluded quasi-RCTs and cross-over studies.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked.  

MAIN RESULTS

Fifty-two studies met the inclusion criteria but only 41 studies, involving 5046 women, provided useable data for the review involving women having caesareans under regional anaesthesia. The majority of the studies involved women undergoing elective caesarean section. Only two studies included emergency surgery, however, they did not stratify data according to type of surgery. The studies covered numerous comparisons, but the majority of studies involved 5-HT(3) receptor antagonists, dopamine receptor antagonists, corticosteroids or acupressure. Studies were mainly small and of unclear quality.Three classes of intervention were found to be effective in at least three out of four of our primary outcomes (intraoperative nausea, intraoperative vomiting, postoperative nausea and postoperative vomiting). These interventions were 5-HT(3) antagonists, dopamine antagonists and sedatives. Other classes of intervention were effective for fewer than three of our primary outcomes.With 5-HT antagonists, we found a reduction in intraoperative nausea (average risk ratio (RR) 0.64, 95% confidence interval (CI) 0.46 to 0.88, eight studies, 720 women). There were also reductions in postoperative nausea (average RR 0.40, 95% CI 0.25 to 0.64, four studies, 405 women) and vomiting (average RR 0.50, 95% CI 0.32 to 0.77, five studies, 565 women). We did not detect a significant reduction in intraoperative vomiting (average RR 0.56, 95% CI 0.31 to 1.00, seven studies, 668 women).Dopamine antagonists demonstrated a reduction in intraoperative nausea (average RR 0.38, 95% CI 0.25 to 0.57, nine studies, 636 women) and intraoperative vomiting (average 0.39, 95% CI 0.24 to 0.64, eight studies, 536 women), with similar reductions in postoperative nausea (average RR 0.60, 95% CI 0.40 to 0.91, five studies, 412 women) and vomiting (average RR 0.57, 95% CI 0.36 to 0.91, six studies, 472 women). These differences were observed with both metoclopramide and droperidol.Sedatives (most commonly propofol) demonstrated a reduction in intraoperative nausea (average RR 0.71, 95% CI 0.52 to 0.96, four studies, 285 women) and intraoperative vomiting (average RR 0.42, 95% CI 0.26 to 0.68, four studies, 285 women), also with a reduction in postoperative nausea (average RR 0.25, 95% CI 0.09 to 0.71, two studies 145 women) and vomiting (average RR 0.09, 95% CI 0.03 to 0.28, two studies, 145 women).Acupressure was found to be effective for intraoperative nausea (average RR 0.59, 95% CI 0.38 to 0.90, six studies, 649 women) but not postoperative nausea (average RR 0.83, 95% CI 0.68 to 1.00, three studies, 429 women). Acupressure was not effective at reducing vomiting either intraoperatively (average RR 0.74, 95% CI 0.46 to 1.18, six studies, 649 women) or postoperatively (average RR 0.69, 95% CI 0.45 to 1.06, three studies, 429 women).Other effective intervention classes included corticosteroids, antihistamines, and anticholinergics.There were insufficient data to demonstrate any class of intervention was superior to another. There were no significant differences observed in the comparison of combined versus single interventions.Few studies assessed our secondary outcomes or the incidence of adverse effects. However, one study showed an increase in respiratory depression with sedation (midazolam) compared with dopamine antagonists.

AUTHORS' CONCLUSIONS

This review indicates that many different interventions have efficacy in preventing nausea and vomiting in women undergoing regional anaesthesia for caesarean section. There is little evidence that combinations of treatment are better than single agents.

Midazolam activates the intrinsic pathway of apoptosis independent of benzodiazepine and death receptor signaling

BACKGROUND AND OBJECTIVES

Midazolam has neurotoxic properties when administered neuraxially in vivo. Furthermore, midazolam induces neurodegeneration in neonatal animal models in combination with other general anesthetics. Therefore, this study focuses on the mechanism of neurotoxicity by midazolam in neuronal and nonneuronal cells. The study aims to evaluate the apoptotic pathway and to investigate the protective effects of the benzodiazepine antagonist flumazenil and the caspase inhibitor N-(2-quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)-methylketone.

METHODS

The apoptosis-inducing effect of preservative-free midazolam on human lymphoma and neuroblastoma cell lines was evaluated using flow cytometric analysis of early apoptotic stages (annexin V/7AAD) and caspase 3 activation. B-cell lymphoma (Bcl2) protein overexpressing and caspase 9-deficient lymphoma cells were used to determine the role of the mitochondrial (intrinsic) pathway. Caspase 8-deficient and Fas-associated protein with death domain (FADD)-deficient cells were used to evaluate the death receptor (extrinsic) pathway. The protective effects of flumazenil and the caspase inhibitor N-(2-quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)-methylketone were investigated in neuroblastoma cells and primary rat neurons using metabolic activity assays (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) and immunofluorescence microscopy.

RESULTS

Midazolam induced apoptosis in all investigated cell types in a concentration-dependent manner, indicated by flow cytometry. Bcl2-overexpression and caspase 9 deficiency protected against toxicity, whereas caspase 8 or FADD deficiency had no effect. Pancaspase inhibition had a strong protective effect, whereas flumazenil did not inhibit midazolam-induced apoptosis.

CONCLUSIONS

Midazolam induces apoptosis via activation of the mitochondrial pathway in a concentration-dependent manner. The mechanism of midazolam toxicity switches from caspase-dependent apoptosis to necrosis with increasing concentrations. The induction of apoptosis and necrosis by midazolam is presumably unrelated to GABAA receptor pathway signaling.

Intrathecal midazolam as supplementary analgesia for chronic lumbar pain--15 years' experience

BACKGROUND

The antinociceptive effect of intrathecal midazolam is based on its affecting spinal gamma-amino butyric acid receptors.

OBJECTIVE

To evaluate pain relief in patients with chronic low back pain and failed back surgery syndrome after a single-shot intrathecal administration of midazolam.

DESIGN

A prospective, open-label study.

OUTCOME MEASURES

The analgesic effect was determined using a patient questionnaire during subsequent visits to the pain therapy service. We classified at least a 50% pain reduction with improved quality of life and improved functional condition as a positive outcome.

RESULTS

Between 1995 and 2010, we performed 500 administrations: 227 administrations in 57 male patients and 273 administrations in 69 female patients. We performed 81 administrations for chronic low back pain and 419 administrations for failed back surgery syndrome. The average age of our patients was 50 years (range 28 to 86). The dose administered ranged from 2 to 5 mg of midazolam. The analgesic effect lasted 9.7 weeks on average, ranging from 1 week to 3 years; the most common reported duration was between 4 and 12 weeks (3 months). In 65% of patients, we achieved pain relief lasting 4 weeks or longer; in 13%, the administration provided no analgesic effect at all. The incidence of side effects (drowsiness, nausea, headache, or transient worsening of complaints) was rather low.

CONCLUSION

Intrathecal midazolam is a useful supplement to standard analgesic therapy with opioids, non-opioids, or spinal steroids.

The influence of adjuvants used in regional anesthesia on lidocaine-induced neurotoxicity in vitro

BACKGROUND

Neurotoxic properties of local anesthetics can rarely lead to irreversible neuronal damage as in cauda equina syndrome. Clinically, local anesthetics are often combined with adjuvants to improve or prolong the anesthetic effect, whereas the impact of such adjuvants on lidocaine-induced apoptosis is unclear. Therefore, we investigated the influence of different adjuvants on the neurotoxicity of lidocaine.

METHODS

Human neuroblastoma cells and primary rat astrocytes were incubated for 24 hrs with lidocaine at a toxic concentration alone and in combination with morphine, sufentanil, clonidine, epinephrine, neostigmine, ketamine, and midazolam. Subsequently, the rates of cell death and early apoptosis were measured by flow cytometry in neuroblastoma cells, whereas astrocyte viability was analyzed by mitochondrial activity assay. In addition, isobolograms were calculated to describe the additive effects of lidocaine with ketamine or midazolam, respectively.

RESULTS

Coadministration of lidocaine with sufentanil, clonidine, epinephrine, and neostigmine did not alter the rates of cell death compared with cells treated with lidocaine alone. Morphine improved the viability of astrocytes only at concentrations beyond those occurring clinically. In contrast, coincubation of lidocaine with ketamine or midazolam led to significantly increased rates of cell death. The combined toxicity of ketamine and lidocaine was additive, whereas the combined toxicity of midazolam and lidocaine was subadditive.

CONCLUSIONS

Sufentanil, clonidine, epinephrine, and neostigmine do not influence the neurotoxicity of lidocaine in vitro. Morphine may have some cytoprotective effect at concentrations greater than those seen intrathecally in humans. In contrast, ketamine and midazolam increase the neurotoxicity of lidocaine in vitro, presumably by additive induction of mitochondrial apoptosis.

Quality of lidocaine analgesia with and without midazolam for intravenous regional anesthesia

PURPOSE

Midazolam has analgesic effects mediated by gamma aminobutyric acid-A receptors. This study was designed to evaluate the effect of midazolam on anesthesia and analgesia quality when added to lidocaine for intravenous regional anesthesia (IVRA).

METHODS

Forty patients undergoing hand surgery were randomly assigned to two groups to receive IVRA. The control group received 3 mg/kg lidocaine 2% w/v diluted with saline to a total volume of 40 ml, and the midazolam group received an additional 50 μg/kg midazolam. Sensory and motor block onset and recovery times, tourniquet pain, intraoperative analgesic requirements, sedation, and anesthesia quality were recorded. Postoperative pain and sedation scores, time to first analgesic requirements, analgesic use in the first 24 h, and side effects were noted.

RESULTS

Sensory and motor block onset and recovery times did not differ significantly between groups. Tourniquet pain scores were lower at 10, 15, 20, and 30 min (P < 0.0001) in the midazolam group. Three (15%) patients in the midazolam group required fentanyl for tourniquet pain compared with thirteen (65%) patients in the control group (P = 0.02). Patients in both groups received fentanyl once. Midazolam group showed that significantly less patients required diclofenac for postoperative analgesia (P < 0.01) and analgesic-free period during first postoperative 24 h was significantly longer (726.8 ± 662.8 min vs. 91.0 ± 35.9 min, P < 0.0001). Postoperative pain scores were lower (P < 0.0001) and sedation scores higher (P < 0.05) for the first 2 h in the midazolam group.

CONCLUSION

Addition of midazolam to lidocaine for IVRA improves anesthesia quality and enhances intraoperative and postoperative analgesia without causing side effects.

Interventions at caesarean section for reducing the risk of aspiration pneumonitis

BACKGROUND

Aspiration pneumonitis is a syndrome resulting from the inhalation of gastric contents. The incidence in obstetric anaesthesia has fallen, largely due to improved anaesthetic techniques and the increased use of regional anaesthesia at caesarean section. However, aspiration pneumonitis is still a cause of maternal morbidity and mortality, and it is important to use effective prophylaxis.

OBJECTIVES

To determine whether interventions given prior to caesarean section reduce the risk of aspiration pneumonitis in women with an uncomplicated pregnancy.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2009).

SELECTION CRITERIA

Randomised controlled trials were included. Quasi-randomised trials were excluded.

DATA COLLECTION AND ANALYSIS

Authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. Data entry was checked.

MAIN RESULTS

Twenty-two studies, involving 2658 women, are included, all having a caesarean section under general anaesthesia. The studies covered a number of comparisons, but were mostly small and of unclear or poor quality.When compared to no treatment or placebo, there was a significant reduction in the risk of intragastric pH < 2.5 with antacids (risk ratio (RR) 0.17, 95% confidence interval (CI) 0.09 to 0.32, two studies, 108 women), H(2) antagonists (RR 0.09, 95% CI 0.05 to 0.18, two studies, 170 women) and proton pump antagonists (RR 0.26, 95% CI 0.14 to 0.46, one study 80 women). H(2) antagonists were associated with a reduced the risk of intragastric pH < 2.5 at intubation when compared with proton pump antagonists (RR 0.39, 95% CI 0.16 to 0.97, one study, 120 women), but compared with antacids the findings were unclear. The combined use of 'antacids plus H(2) antagonists' was associated with a significant reduction in the risk of intragastric pH < 2.5 at intubation when compared with placebo (RR 0.02, 95% CI 0.00 to 0.15, one study, 89 women) or compared with antacids alone (RR 0.12, 95% CI 0.02 to 0.92, one study, 119 women).

AUTHORS' CONCLUSIONS

The quality of the evidence was poor, but the findings suggest that the combination of antacids plus H(2) antagonists was more effective than no intervention, and superior to antacids alone in preventing low gastric pH. However, none of the studies assessed potential adverse effects or substantive clinical outcomes. These findings are relevant for all women undergoing caesarean section under general anaesthesia.