Respiratory depression complicating epidural diamorphine

Two cases of severe respiratory depression complicating epidural diamorphine administration are reported. In both cases, the dura had been punctured. The risk of epidural opiate administration in association with a breach in the dura is reiterated.     

A double-blind comparison of epidural ketamine and diamorphine for postoperative analgesia

Twenty patients who had abdominal hysterectomy under general anaesthesia were randomly assigned to receive either epidural ketamine (30 mg), or epidural diamorphine (5 mg) peri-operatively and on first request for analgesia. Failure to obtain satisfactory analgesia with one of the agents was treated by epidural administration of the other. Pain was assessed by an independent observer, and by the patient using a visual analogue scale. The mean (SD) pain score on recovery from general anaesthesia, on a scale of 0-4, was 2.9 (1.2) for the ketamine group and 1.0 (1.0) for the diamorphine group (p less than 0.01). The mean (SD) time to first request for analgesia was 272 (206) and 72 (41) minutes in the diamorphine and ketamine groups respectively (p less than 0.01). All patients in the diamorphine group obtained adequate analgesia, but all patients in the ketamine group were changed to epidural diamorphine. Epidural ketamine does not appear to be a sufficiently effective alternative to epidural diamorphine for routine use in postoperative pain.     

High-dose intrathecal diamorphine for analgesia after Caesarean section

Forty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric 0.5% bupivacaine were randomly allocated to receive either 0.5 mg or 1 mg intrathecal diamorphine. All women received diclofenac 100 mg at the end of surgery and morphine via a patient-controlled analgesia system. Oral analgesics were not used. Postoperative analgesia was more prolonged and more reliable in the 1-mg group. Mean time to first analgesia was 10.2 h in the 1-mg group and 6.9 h in the 0.5-mg group, and 45% in the 1-mg group used no morphine, compared with 10% in the 0.5-mg group. Mean morphine consumption over 24 h was 5.2 mg in the 1-mg group and 10.6 mg in the 0.5-mg group. Pain scores all tended to be lower in the 1-mg group but this was only significant at 4 h. There were no serious side-effects. Minor side-effects were common but well tolerated, and the incidence did not differ between the groups. If intrathecal diamorphine is used in combination with rectal diclofenac and without oral analgesia, then 1 mg provides superior analgesia to 0.5 mg without any worsening of the side-effects.     

Myoclonic spasms after epidural diamorphine infusion

A case is presented in which myoclonus occurred after epidural diamorphine infusion. Reports of this phenomenon following other epidural drugs and possible mechanisms are discussed.     

Lumbar epidural diamorphine following thoracic surgery

Twenty-two patients received a single dose of diamorphine 5 mg through a lumbar epidural catheter before thoracic surgery. The patients were transferred after surgery to a high dependency unit where they were allocated randomly to receive either an infusion of epidural diamorphine at a rate of 1 mg/hour (group 1) or bolus doses of epidural diamorphine 5 mg on demand (group 2). There was no statistically significant difference between the groups in visual analogue pain scores in the first 18 postoperative hours. Arterial carbon dioxide tension was elevated in both groups and was consistently higher in group 1 than in group 2, with a statistically significant intergroup difference 12 hours after operation. Respiratory rate was not a useful index of respiratory depression. The commonest nonrespiratory side effect was urinary retention, but the incidences of this and other minor side effects were similar in the two groups.     

Perineuronal morphine: a comparison with epidural morphine

In a double-blind, randomised controlled cross-over study the effects of perineuronal (perifemoral) injections of morphine were compared with epidural injections with the same amount of morphine in patients after knee surgery. Better pain scores were achieved during treatment with epidural morphine. We have not been able to confirm the hypothesis of neuro-axonal transport of morphine from the periphery to the spinal cord.     

Intradural morphine and diamorphine

This open study of 81 patients having major orthopaedic surgery reviews the duration of analgesia and side-effects of 0.625, 1.25 or 2.5 mg of morphine or 1.25 or 2.5 mg of diamorphine given intradurally in combination with 7.5 mg of cinchocaine at induction of anaesthesia. A significant dose-response relationship for duration of analgesia measured by time to first requirement of postoperative analgesic was found with morphine; 1.25 and 2.5 mg of morphine produced analgesia of longer duration than 0.625 mg. No such dose-response was found for side-effects. There was no significant difference in duration of analgesia between diamorphine 1.25 and 2.5 mg, and the duration was similar to that seen with the higher doses of morphine. An intradural dose of between 0.625 mg and 1.25 mg of either morphine or diamorphine used with cinchocaine and without additional parenteral opiate, may be appropriate.     

Extradural versus intramuscular diamorphine

The effects of diamorphine hydrochloride 0.1 mg/kg, given either extradurally or intramuscularly for postoperative analgesia were compared in two randomised double-blind studies involving 39 patients undergoing thoracotomy and major gynaecological surgery. Assessments were made at fixed intervals after the administration of diamorphine and consisted of the measurement of pain or analgesic effect. Segmental, sympathetic and any adverse effects were sought. There was no significant difference in the quality of analgesia between the two groups in either trial. Extradural diamorphine provided safe and effective analgesia of rapid onset, with no specific undesirable side-effects. In both studies, analgesia was more prolonged following extradural administration. The relative proportion of spinal binding may be increased after extradural administration and this may be reflected in the prolonged analgesia observed.     

Intrathecal diamorphine for analgesia after Caesarean sectionA dose finding study and assessment of side-effects

Eighty women undergoing elective Caesarean section under spinal anaesthesia using hyperbaric bupivacaine 0.5% were randomly allocated to receive, in addition, intrathecal diamorphine 0.125, 0.25 or 0.375 mg or saline. Postoperative morphine requirements, measured using a patient-controlled analgesia system, were reduced in a dose-dependent manner by diamorphine. Pain scores were significantly lower at 2 and 6 h following the two larger doses of diamorphine. Less supplemental analgesia was required intra-operatively if intrathecal diamorphine had been given. The incidences of vomiting and pruritus were also dose-related. No respiratory rates of less than 14 breath.min⁻¹ were recorded and the incidence of oxygen saturation readings less than 95% and 90% did not differ between groups. There were no adverse neonatal effects. Intrathecal diamorphine in the present study was found to be safe in doses of up to 0.375 mg following Caesarean section. However, minor side-effects were frequently observed.     

Epidural infusion of diamorphine with bupivacaine in labour

We have compared the analgesic effects of three epidural infusions in a randomised, double-blind study of 61 mothers in labour. An initial dose of bupivacaine 0.5% 8 ml was followed by either bupivacaine 0.125%, bupivacaine 0.125% with diamorphine 0.0025% or bupivacaine 0.125% with fentanyl 0.0002%. All infusions were run at a rate of 7.5 ml/hour. Analgesia was significantly better in both the groups receiving opioids. Diamorphine was shown to be the more effective supplement to bupivacaine. The 5% incidence of pruritis in the opioid groups was less than that reported by earlier authors.     

Effects of epidural diamorphine on the somatosensory evoked potential to posterior tibial nerve stimulation

We have studied the effects of the epidural administration of diamorphine 0.1 mg/kg at the L3-4 interspace on somatosensory evoked potentials in the cervical epidural space before corrective surgery for idiopathic adolescent scoliosis. A further eight patients in whom anaesthesia was maintained with a propofol infusion acted as a control group. Epidural diamorphine had no effect on the latency or amplitude of the evoked potentials. We conclude that epidural diamorphine is a suitable technique to use in scoliosis surgery because of its lack of effect on neurophysiological variables, although the potential respiratory problems need investigation.     

Epidural buprenorphine for postoperative analgesia. A controlled comparison with epidural morphine.

In a double-blind controlled study, epidural buprenorphine 0.3 mg was compared with 4 mg of epidural morphine for postoperative pain relief the first 24 hours after major orthopaedic surgery. The degree of analgesia was equal and satisfactory in both groups. Duration of action was 620 minutes with buprenorphine and 580 minutes with morphine, which was not significantly different. The only serious side effects were recorded in the morphine group, with two patients complaining of pruritus and five of urinary retention. In conclusion, epidural buprenorphine did not offer any advantages in preference to morphine for postoperative pain relief following orthopaedic surgery.     

Epidural fentanyl and 0.5% bupivacaine for elective Caesarean section

Either 100 micrograms fentanyl or 2 ml saline was added to 0.5% bupivacaine administered epidurally for elective Caesarean section in 30 patients, in a double-blind randomised study. Bupivacaine 0.5% was administered until a complete sensory block was established extending to the 4th thoracic dermatome. One of the patients who received epidural fentanyl required intravenous alfentanil and Entonox and another, Entonox only briefly during surgery, compared with seven in the control group who required intravenous alfentanil and Entonox and one who required Entonox only. Postoperative analgesia was of longer duration in those who received epidural fentanyl (p less than 0.01). There were no deleterious effects on neonatal or maternal outcome.     

Some aspects of epidural block provided for elective Caesarean section

We present here clinical data from 993 patients who were destined to undergo elective Caesarean section under epidural analgesia. In 29 cases the attempt to provide an epidural was abandoned before the operation started. In regard to this, the importance of monitoring the fetal heart rate during initiation of the epidural is emphasised. In 10 cases general anaesthesia was induced after delivery, and in a further 108 cases supplemental analgesia was administered, either systemically, by inhalation or by an additional epidural top-up, after delivery. Satisfactory analgesia throughout the operation was achieved in 87.8%. In an appreciable proportion of cases the recommended maximum dose of bupivacaine, and the recommended maximum rate of bupivacaine administration, were exceeded without apparent complication. There was a tendency for the volume of Hartmann's solution infused intravenously before and during initiation of the epidural to be increased throughout the period under review (1971-85). The prevalence of hypotension diminished during that period. Characteristics of the data did not permit a close analysis of the main factors which could have led to an episode of maternal hypotension. However, it did appear that such an episode could be ascribed to too brief an interval between the first and second, or the second and third top-up doses. The frequency with which blood was transfused during operation was markedly lower than that noted in a concurrent series of elective sections conducted under general anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intrathecal morphine for Caesarean section: an assessment of pain relief, satisfaction and side-effects

In a prospective, randomised, double-blind study of 60 patients who had an elective Caesarean section under spinal anaesthesia we compared 0.1 mg intrathecal morphine with intrathecal saline placebo. All patients received morphine intravenously by patient-controlled analgesia after the operation. Pain, satisfaction and side-effects were assessed at 4 and 24 h after the operation. Pain measured by a 100-mm visual analogue scale was less in the intrathecal morphine group at both times (p <0.05) and morphine consumption was lower (p <0.01). At 4 h the intrathecal morphine group had more pruritus (p <0.001) but there was no difference in satisfaction. At 24 h there was no significant difference in side-effects, but overall satisfaction measured by visual analogue scale was better in the intrathecal morphine group (p <0.01). Intrathecal morphine improves pain relief and patient satisfaction after Caesarean section.     

Double-blind testing fails to confirm analgesic response to extradural morphine

We report two patients with chronic non-malignant pain in whom morphine given intravenously via a patient-controlled analgesia system produced partial pain relief but was accompanied by severe side effects. Open administration of epidural morphine resulted in complete pain relief with minimal side effects and the patients were considered as candidates for implanted opioid delivery systems. However, when the epidural morphine was given in a double-blind and placebo-controlled manner, morphine did not produce greater analgesia than placebo and no dose-response relationship was seen. These cases show that careful investigation is necessary before proceeding to implanted systems and that changing the route did not improve the analgesia:side effect balance for morphine in these patients.