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

Addition of low-dose ketamine to midazolam and low-dose bupivacaine improves hemodynamics and postoperative analgesia during spinal anesthesia for cesarean section

BACKGROUND AND AIMS

Spinal anesthesia for cesarean section (CS) is associated with an incidence of hypotension of 60-94%. This study hypothesizes that intrathecal combination of low-dose ketamine, midazolam, and low-dose bupivacaine improves hemodynamics and postoperative analgesia compared with fentanyl and low-dose bupivacaine during CS.

MATERIAL AND METHODS

Fifty parturients undergoing elective CS were randomized equally to receive ketamine (10 mg), midazolam (2 mg) and 0.5% hyperbaric bupivacaine (8 mg) in group ketamine-midazolam-bupivacaine (KMB) or fentanyl (25 μg) and 0.5% hyperbaric bupivacaine (8 mg) in group fentanyl-bupivacaine (FB). Heart rate (HR), mean arterial blood pressure (MAP), oxygen saturation, sensorimotor block characteristics, pain-free period, side-effects including: hypotension, bradycardia, nausea, vomiting, sedation, pruritus, respiratory depression and dissociative manifestations, Apgar score at 1 and 5 min, and patients' satisfaction visual analog scores (VAS) were recorded. Patients in group KMB were followed for 6 months in order to assess any neurological disorder.

RESULTS

Group KMB showed higher sensory level (P = 0.006), rapid sensory (P = 0.001) and motor (P = 0.005) onsets, prolonged sensory (P = 0.008) and motor (P = 0.002) blocks, and prolonged pain free period (P = 0.002). Ketamine-midazolam stabilized HR and MAP, and significantly reduced incidence of hypotension (P = 0.002), bradycardia (P = 0.013) and vomiting (P = 0.019). Apgar scores at 1 and 5 min were comparable in both groups (P = 0.699 and 0.646 respectively). Patients' satisfaction VAS scores were significantly higher in group KMB (P = 0.001). No patients in KMB group showed dissociative or neurotoxic manifestations.

CONCLUSION

Intrathecal low-dose ketamine combined with midazolam and low-dose bupivacaine stabilizes hemodynamics and prolongs postoperative analgesia without significant side-effects in parturients undergoing CS.

Efficacy of intrathecal midazolam in potentiating the analgesic effect of intrathecal fentanyl in patients undergoing lower limb surgery

Introduction:

The intrathecal administration of combination of drugs has a synergistic effect on the subarachnoid block characteristics. This study was designed to study the efficacy of intrathecal midazolam in potentiating the analgesic duration of fentanyl along with prolonged sensorimotor blockade.

Materials and Methods:

In a double-blind study design, 75 adult patients were randomly divided into three groups: Group B, 3 ml of 0.5% hyperbaric bupivacaine; Group BF, 3 ml of 0.5% hyperbaric bupivacaine + 25 mcg of fentanyl; and Group BFM, 3 ml of 0.5% hyperbaric bupivacaine + 25 mcg of fentanyl + 1 mg of midazolam. Postoperative analgesia was assessed using visual analog scale scores and onset and duration of sensory and the motor blockade was recorded.

Results:

Mean duration of analgesia in Group B was 211.60 ± 16.12 min, in Group BF 420.80 ± 32.39 min and in Group BFM, it was 470.68 ± 37.51 min. There was statistically significant difference in duration of analgesia between Group B and BF (P = 0.000), between Group B and BFM (P = 0.000), and between Group BF and BFM (P = 0.000). Both the onset and duration of sensory and motor blockade was significantly prolonged in BFM group.

Conclusion:

Intrathecal midazolam potentiates the effect of intrathecal fentanyl in terms of prolonged duration of analgesia and prolonged motor and sensory block without any significant hemodynamic compromise.

Antiemetic effects of midazolam added to fentanyl-ropivacaine patient-controlled epidural analgesia after subtotal gastrectomy: A prospective, randomized, double-blind, controlled trial

BACKGROUND

Nausea and vomiting are frequent adverse effects of patient-controlled epidural analgesia (PCEA) with opioids.

OBJECTIVE

This study was designed to assess the antiemetic effect of midazolam added to fentanyl-ropivacaine PCEA.

METHODS

In a prospective, randomized, double-blind, controlled trial, smoking patients with gastric cancer undergoing elective subtotal gastrectomy were evenly allocated to 1 of 2 treatment groups to manage postoperative pain: 0.2% ropivacaine mixed with fentanyl 4 μg/mL and midazolam 0.2 mg/mL (test group) or 0.2% ropivacaine mixed with fentanyl 4 μg/mL (control group). The PCEA infusion was set to deliver 4 μL/h of the study solution, with a bolus of 2 mL per demand and a 15-minute lockout time. The incidence of postoperative nausea and vomiting (PONV), pain intensity, sedation score, usage of rescue analgesia and rescue antiemetic, respiratory depression, urinary retention, and pruritus were recorded at 2, 6, 12, 24, 48, and 72 hours after surgery. Total infused volume of PCEA at 72 hours after surgery was measured.

RESULTS

A total of 60 patients were approached and randomized to treatment. No patients were excluded by exclusion criteria and all enrolled patients completed this study. Incidence of nausea (7% vs 33%; P = 0.02) in the test group was significantly lower than in the control group. The overall frequency of PONV in the test group was significantly less than that of the control group (7% vs 40%; P = 0.006). In addition, the mean (SD) infused volume of PCEA in the test group was significantly lower than that in the control group (392.3 [68.9] vs 351.2 [49.8] mL; P = 0.01). However, there were no significant differences in pain intensity, usage of rescue antiemetics and rescue analgesics, and mild pruritus between groups. No patient reported moderate or severe sedation, respiratory depression, or hypoxemia. In addition, there were no severe adverse events.

CONCLUSIONS

Midazolam added to fentanyl-ropivacaine PCEA was associated with a significant reduction in the incidence of PONV compared with fentanyl-ropivacaine alone, and a significant decrease in the amount of PCEA administered without a significant increase in adverse events in these patients who underwent subtotal gastrectomy.

Combination of low doses of intrathecal ketamine and midazolam with bupivacaine improves postoperative analgesia in orthopaedic surgery

BACKGROUND

Intrathecal ketamine produces a short period of analgesia with stable haemodynamics. Midazolam with bupivacaine prolongs the duration of analgesia when administered intrathecally but does not prevent hypotension. The objective of this study was to assess the effect of a combination of intrathecal bupivacaine, ketamine and midazolam on the duration of analgesia and haemodynamic parameters.

METHODS

A prospective, randomized, double-blind study was carried out in 60 ASA I and II patients undergoing lower limb surgery under spinal anaesthesia. Patients were divided into three groups of 20 each. Patients in all the three groups received 3 mL of hyperbaric bupivacaine (0.5%) intrathecally. In addition, patients in Groups II and III received intrathecal ketamine (0.1 mg kg-1) and the same dose of ketamine along with midazolam (0.02 mg kg-1), respectively. All patients were evaluated for block characteristics, duration of pain-free period, total rescue analgesic requirement in the 24-h postoperative period, total dose of mephenteramine to treat hypotension and any central or neurological complication.

RESULTS

No patients in Group II required mephenteramine while 40% of patients in Group I and 10% in Group III required mephenteramine to maintain blood pressure after spinal anaesthesia. The mean +/- standard deviation duration of pain-free period was 331.5 +/- 89.9, 369.7 +/- 124.2 and 730.5 +/- 81.5 min in Group I, II and III, respectively. The pain-free interval was significantly greater in Group III compared to Groups I and II (P < 0.001). No patient had any complications.

CONCLUSION

A low dose of midazolam and ketamine with bupivacaine intrathecally results in prolonged analgesia and less haemodynamic fluctuations. However, the safety of this combination needs to be proved before its use in clinical practice.

Antinociceptive synergy between the cannabinoid receptor agonist WIN 55,212-2 and bupivacaine in the rat formalin test

BACKGROUND

The analgesic interaction between cannabinoids and local anesthetics has not been investigated. We sought to determine the nature of the interaction between the intrathecal cannabinoid receptor agonist (WIN 55,212-2) and bupivacaine using the formalin test.

METHODS

Lumbar intrathecal catheters were implanted in male Sprague-Dawley rats. After intrathecal administration of WIN 55,212-2, bupivacaine, or their combination, 50 microL of 5% formalin was injected subcutaneously into the hindpaw. Dose-response curves were established and the respective ED50 (50% effective dose) values were determined for each agent alone. Fixed-ratio combinations of WIN 55,212-2 and bupivacaine were tested for combined antinociceptive effects in the formalin test and an isobolographic analysis was performed to characterize the pharmacologic interaction of both drugs.

RESULTS

Intrathecally administered WIN 55,212-2, bupivacaine, or their combination produced a dose-dependent decrease in the number of flinches during Phase 1 and 2 of the formalin test. Isobolographic analysis revealed a synergistic interaction between intrathecal WIN 55,212-2 and bupivacaine in both phases of the formalin test. In combination, the ED50 value was significantly smaller than the theoretical additive value (P < 0.05).

CONCLUSIONS

These results demonstrate that intrathecally coadministered WIN 55,212-2 and bupivacaine provide synergistic antinociceptive interaction in both phases of the formalin test.

Intrathecal midazolam regulates spinal AMPA receptor expression and function after nerve injury in rats

Spinal gamma-aminobutyric acid (GABA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been implicated in the mechanisms of neuropathic pain after nerve injury; however, how these two receptors interact at the spinal level remains unclear. Here we show that intrathecal midazolam through activation of spinal GABAA receptors attenuated the expression and function of spinal AMPA receptors in rats following peripheral nerve injury. Thermal hyperalgesia and mechanical allodynia induced by chronic constriction nerve injury (CCI) in rats were attenuated by the short-acting benzodiazepine midazolam (20=10>5 mug>vehicle) administered intrathecally once daily for 7 postoperative days. CCI-induced upregulation of AMPA receptors within the spinal cord dorsal horn was also significantly reduced by the intrathecal midazolam (10, 20 mug) treatment. The inhibitory effects of midazolam (10, 20 mug) on neuropathic pain behaviors and AMPA receptor expression were prevented by co-administration of midazolam with the GABAA receptor antagonist bicuculline (3 mug), whereas intrathecal treatment with bicuculline (1 or 3 mug) alone in naive rats induced the upregulation of spinal AMPA receptor expression and nociceptive responses, indicating a tonic regulatory effect from endogenous GABAergic activity on the AMPA receptor expression and spinal nociceptive processing. These results indicate that modulation of spinal AMPA receptor expression and function by the GABAergic activity may serve as a mechanism contributory to the spinal nociceptive processing.

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.