Intrathecal midazolam increases the analgesic effects of spinal blockade with bupivacaine in patients undergoing haemorrhoidectomy

Neurotoxicity with single dose intrathecal midazolam administration

BACKGROUND AND OBJECTIVE

The aim of study was to investigate the electron microscopic changes in the medulla of the spinal cord that occur with intrathecal midazolam administration.

METHODS

Twenty-eight albino rabbits of New Zealand type were randomized into two groups. Following anaesthesia, 16 rabbits were given 300 microg of midazolam (Group M) and 12 rabbits were given 0.3 mL of normal saline solution (Group C) intrathecally. Eight rabbits from Group M (Group M1) and 6 rabbits from Group C (Group C1) were sacrificed 24 h after the anaesthesia and 8 rabbits from Group M (Group M2) and 6 rabbits from Group C (Group C2) were sacrificed 6 days after the anaesthesia. The lumbosacral portion was removed by laminectomy and thin sections were examined microscopically.

RESULTS

Severe separation in myelin lamella of the large axons, honeycomb appearance, slight separation in myelin lamella of small to moderately large axons, degenerate vacuoles in the cytoplasm and nuclear membrane irregularity were observed in neurons of Groups M1 and M2. Myelin lamella and nuclear membranes were found to be regular, vacuoles and oedema were observed in the neurons in the Groups C1 and C2.

CONCLUSION

Midazolam administered at single dose by the intrathecal route may have neurotoxic effects on the neurons and myelinated axons at 24 h and 6 days following administration.

Brachial plexus block with midazolam and bupivacaine improves analgesia

PURPOSE

Adjuncts to local anesthetics for brachial plexus block may enhance the quality and duration of analgesia. Midazolam, a water-soluble benzodiazepine, is known to produce antinociception and enhance the effect of local anesthetics when given epidurally or intrathecally. The purpose of this study was to assess the effect of midazolam added to brachial plexus anesthesia.

METHODS

A prospective, randomized, double blind study was conducted on 40 ASA I or II adult patients undergoing upper limb surgeries under supraclavicular brachial plexus block. Patients were randomly divided into two groups. Patients in Group B (n = 20) were administered 30 mL of 0.5% bupivacaine and Group BM (n = 20) were given 30 mL of 0.5% bupivacaine with midazolam 50 microg x kg(-1). Hemodynamic variables (i.e., heart rate, noninvasive blood pressure), pain scores and rescue analgesic requirements were recorded for 24 hr postoperatively.

RESULTS

The onset of sensory and motor block was significantly faster in Group BM compared to Group B (P < 0.05). Pain scores were significantly higher in Group B compared to Group BM from two hours to 24 hr postoperatively (P < 0.05). Rescue analgesic requirements were significantly less in Group BM compared to Group B (P < 0.05). Hemodynamics and sedation scores did not differ between groups in the post-operative period.

CONCLUSION

Midazolam (50 microg x kg(-1)) in combination with 30 mL of bupivacaine (0.5%) hastened onset of sensory and motor block, and improved postoperative analgesia when used in brachial plexus block, without producing any adverse events.

The use of intrathecal midazolam in humans: a case study of process

Early preclinical work demonstrated the potential role of spinal benzodiazepine pharmacology in regulating spinal nociceptive transmission. We review this preclinical activity and the evolving implementation of intrathecal midazolam in humans for pain management. Important elements in this development for use in humans are issues pertinent to safety and the preclinical reports that have increased our understanding of intrathecal midazolam toxicity. We seek to emphasize the time course of these studies and how they merged to provide enabling data that drove the clinical implementation. In the case of midazolam, we point to the potential issues that arose when preclinical safety data were unreasonably ignored and how consideration of preclinical safety data can serve to facilitate drug development by demonstrating reasonable safety profiles that document the minimal degree of potential risk to the patient. Issues that are of continuing relevance to the use of intrathecal midazolam, including issues of formulation and kinetics, are considered.

IMPLICATIONS

The intrathecal use of midazolam has evolved over 20 years though a combination of preclinical and clinical investigations. We review the time course of this development to define critical elements that should be pursued in reducing the risk associated with the clinical use of a novel spinal drug.

Sedation with Midazolam Leads to Reduced Pain After Dental Surgery

Our principal objective in this study was to evaluate the potential pain reducing effect of i.v. midazolam in patients undergoing oral surgery. One-hundred-twenty-five patients with impacted mandibular third molars requiring removal under local anesthetic were randomized into 2 groups. The first group (n = 64) was administered i.v. midazolam by titration until a clinical end-point of conscious sedation followed by local anesthetic before surgery; the second group (n = 61) was the control and was administered only local anesthetic before surgery. The surgery was performed in a standardized manner in both groups by the same surgeon. Outcome measures were four primary end-points: pain intensity as assessed by a 100-mm visual analogue scale and a 4-point categorized scale hourly for 8 h, time to first analgesic, total analgesic (ibuprofen) consumption over the first 48 h, and a 5-point categorical patient global assessment scale (0 = poor, 1 = fair, 2 = good, 3 = very good, and 4 = excellent). Throughout the 8-h investigation period, patients in the midazolam group reported significantly lower pain intensity scores than those in the control group (19.0 +/- 13.2 mm versus 28.1 +/- 12.8 mm, P < 0.05). The patients in the midazolam group also reported significantly longer time to first analgesic (165.5 +/- 56.5 min versus 202.2 +/- 79.0 min, P < 0.05), less analgesic consumption (1275 +/- 364 mg versus 1688 +/- 407 mg, P < 0.001) and better patient global assessment (3.34 +/- 0.8 versus 2.4 +/- 0.9, P < 0.001). We conclude that systemically administered midazolam is effective in reducing postoperative pain after third molar surgery.

IMPLICATIONS

In this observer blinded study, we found that i.v. midazolam treatment (0.09 mg/kg) has a pain-reducing effect after third molar surgery, thus improving postoperative pain management.

Improvement in postoperative pain relief by the addition of midazolam to an intrathecal injection of buprenorphine and bupivacaine

BACKGROUND AND OBJECTIVE

Intrathecal injections of the benzodiazepine midazolam have been reported to cause antinociception in animals and pain relief in human beings, including the potentiation of opioid analgesia. This study compared the efficacy of the addition of midazolam to a mixture of buprenorphine and bupivacaine used for spinal anaesthesia.

METHODS

The study was prospective, randomized, and observer blinded. It involved 60 patients (30 per group), ASA I and II, age 20-40 yr, undergoing minor and intermediate lower abdominal surgery under spinal anaesthesia. Patients were randomized into two groups: the control group received a spinal injection of hyperbaric bupivacaine (15 mg) plus buprenorphine (0.15 mg) and the experimental group received a spinal injection of the same two drugs and doses but supplemented with intrathecal midazolam (2 mg).

RESULTS

The duration of postoperative analgesia in the control group was 9.24 +/- 2.57 h (mean +/- SEM), and 21.33 +/- 12.69 h in the midazolam treated group (P < 0.001). Patients treated with intrathecal midazolam had better pain relief judged by visual analogue score on coughing (P = 0.0013) and a nursing mobility score (P < 0.0001). Adverse effects were minor and their incidence was similar in both groups.

CONCLUSIONS

We conclude that intrathecal midazolam 2 mg improves the quality and duration of postoperative pain relief afforded by intrathecal buprenorphine and bupivacaine.

Intrathecal midazolam added to bupivacaine improves the duration and quality of spinal anaesthesia

BACKGROUND

The antinociceptive action of intrathecal midazolam is well documented. In this prospective study, we investigated the addition of midazolam to intrathecal bupivacaine on the duration and quality of spinal blockade.

METHODS

Forty ASA I or II adult patients undergoing lower abdominal surgery were selected for the study. The patients were randomly allocated to receive 3 ml of 0.5% hyperbaric bupivacaine intrathecally either alone or with 1 mg of midazolam using a combined spinal epidural technique. The duration and quality of sensory and motor block, perioperative analgesia, haemodynamic changes, and sedation levels were assessed.

RESULTS

The duration of sensory block (i.e. time to regression to the S2 segment) was significantly longer in the midazolam group than the control group (218 min vs. 165 min; P < 0.001). The duration of motor block was also prolonged in the midazolam group as compared with the control group (P < 0.01). In 90% of the patients in the midazolam group, the quality of block was adequate during the intra-operative period as compared with only 65% of the patients in the control group (P < 0.05). The duration of effective analgesia was longer in the midazolam group than in the control group (199 vs. 103 min; P < 0.001). Blood pressure, heart rate, oxygen saturation and sedation scores were comparable in both groups. No neurological deficit or other significant adverse effects were recorded.

CONCLUSION

The addition of intrathecal midazolam to bupivacaine significantly improves the duration and quality of spinal anaesthesia and provides prolonged perioperative analgesia without significant side-effects.

Midazolam can potentiate the analgesic effects of intrathecal bupivacaine on thermal- or inflammatory-induced pain

Epidurally administered midazolam can potentiate analgesia by epidural bupivacaine. However, whether this effect is synergistic or additive is not known. In this study, we investigated the spinally-mediated analgesic interaction between midazolam and bupivacaine by using the tail-flick and formalin tests in rats with chronically implanted catheters. Behavioral effects were also observed. The dose dependency of analgesia and the 50% effective doses of intrathecal midazolam and bupivacaine were determined, and then the interaction of these two drugs was examined with an isobolographic analysis. Both drugs had dose-dependent analgesic effects in both the tail-flick test and the formalin test. The 50% effective dose values of the combination were significantly lower than the calculated additive values in both tests (P = 0.023 in the tail-flick test; P = 0.0025 in Phase 1 and 0.047 in Phase 2 of the formalin test). Behavioral side effects decreased in the combination group compared with each drug alone. In conclusion, intrathecally administered midazolam and bupivacaine had synergistic analgesic effects on acute thermal- or inflammatory-induced pain, with decreased behavioral side effects.

IMPLICATIONS

In both acute thermal- and inflammatory-induced pain, intrathecally administered midazolam and bupivacaine produced synergistic analgesia with decreased side effects in intrathecally catheterized rats.