Department of Anaesthesiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Kangnam-Ku, Seoul 135-710, Korea*Corresponding author
Accepted for publication: July 19, 2000
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Abstract |
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Br J Anaesth 2001; 86: 779
Keywords: anaesthetic techniques, spinal; analgesia, postoperative, anaesthetics local, bupivacaine; hypnotics benzodiazepine, intrathecal midazolam; surgery, haemorrhoidectomy
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Introduction |
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After haemorrhoidectomy, many patients require parenteral oral opioids and/or nonsteroidal antiinflammatory drugs (NSAIDs) for analgesia. The use of opioids in intrathecal or epidural anaesthesia has become popular to optimize postoperative analgesia. However, opioid-induced side effects, such as respiratory depression, nausea, vomiting, urinary retention and pruritus, limit their use.8 9 The purpose of our study was to assess the effects of intrathecal midazolam as an adjunct to intrathecal bupivacaine after haemorrhoidectomy.
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Methods |
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Saddle block anesthesia was performed in the sitting position under aseptic conditions using a 25 G spinal needle and the subarachnoid space was entered at the L34 level. Patients were kept in the sitting position for 5 min, tested for sensory loss and then placed in the prone position before surgery.
During surgery, patients were monitored with electrocardiography, pulse oximetry and non-invasive measurement of arterial pressure and heart rate. After surgery, all patients were admitted for 1 day and instructed to take two Codety tablets (each tablet containing 300 mg paracetamol and 30 mg codeine phosphate) every 4 h as needed. No other analgesic was allowed during the 24 h after surgery.
Three parameters were assessed in this study: duration of effective analgesic time from the spinal anaesthesia; visual analogue scales (VAS) at first analgesia; and total consumption of analgesics in the 24 h after spinal anaesthesia. Any adverse events were also recorded. Neurological changes, such as motor and sensory deficits, bowel and bladder dysfunction, were checked before discharge. The anaesthetist who performed subarachnoid block was not involved in assessment of patients and the observers were blinded.
Data are expressed as mean (SD). Statistical analysis was performed using the computer program SPSS (version 9.0; SPSS Inc., Chicago, IL, USA). One-way analysis of variance (ANOVA) was used for normally distributed parametric data. Time to first analgesia, pain scores at first pain medication and the number of analgesics requested in 24 h were analysed by the KruskalWallis test followed by the post hoc multiple comparison test using the Dunnett method. P<0.05 was considered statistically significant.
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Results |
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There were no episodes of bradycardia, hypotension, sedation or dizziness in any patients. Three of the 15 patients from each group developed urinary retention. Time to the first episode of self-voiding was similar in all groups. No neurological deficits were detected at discharge (Table 3).
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Discussion |
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This study may be criticized on account of the different volumes of subarachnoid injection (1.2 ml was injected in the control and BM1 groups; and 1.4 ml in the BM2 group) and the consequent differences in bupivacaine concentration. However, Van Zundert and colleagues10 have shown that the concentration and volume do not affect sensory block, motor block or duration of spinal anesthesia as long as the dose of local anaesthetic is constant.
In vitro autoradiography has shown that there is a high density of benzodiazepine (GABA-A) receptors in lamina II of the dorsal horn in the human spinal cord, suggesting a possible role in pain modulation.11 In 1987, Goodchild and Serrao reported that benzodiazepines might have analgesic effects at the spinal cord level in animals.2 Analgesic efficacy of intrathecal midazolam in humans has been demonstrated recently.57 The -selective opioid antagonist, naltrindole, suppresses the antinociceptive effect of intrathecal midazolam,12 suggesting that intrathecal midazolam is involved in the release of an endogenous opioid acting at spinal
receptors.
The most serious risk of intrathecal midazolam is its possible neurotoxicity. So far, animal studies have revealed no damage to the spinal cord, nerve roots or meninges.13 There have been some reports on the spinal application of midazolam in humans. A single intrathecal injection of 2 mg midazolam did not cause any clinical neurological deficits and produced significant analgesia for 2 months in patients with chronic low back pain.5 Intrathecal midazolam was also effective after leg surgery, without any side effects.4 In addition to the effectiveness of intrathecal midazolam against somatic pain, an antinociceptive effect against visceral pain has been demonstrated in rabbits subjected to intestinal distension3 and in humans after caesarean section.6 Intrathecal midazolam has been used in a continuous infusion with doses of 6 mg day1 for a long-term period in four patients with refractory neurogenic and musculoskeletal pain.7 In vitro studies have suggested that clinically useful doses of intrathecal midazolam are unlikely to be neurotoxic.14 In our study, we paid special attention to any potential side effects or complications during the perioperative period. There were no neurological complications. The analgesic effect of intrathecal midazolam was segmental, with no alteration in sympathetic tone or reflexes.
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References |
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