SummaryPain on injection of propofol is a common problem, the cause of which remains unknown. The chemical properties and preparation of propofol, proposed mechanisms for the cause of the pain and clinical strategies to prevent pain on injection of propofol are reviewed in the hope of shedding some light on the subject.
SummaryThe effect of pre-versus postincisional epidural blockade without the use of systemic opioids was investigated in a randomised, double-blind study of two groups of 25 patients undergoing abdominal hysterectomy performed under general anaesthesia. The first group received, via a lumbar epidural catheter, 0.9% saline (16 ml) 15 min prior to surgical incision and 0.5% bupivacaine (15 ml) and fentanyl 50 mg (1 ml) 15 min prior to skin closure. The second group of 25 patients received the same amount of bupivacaine and fentanyl 15 min pre-incision and saline prior to skin closure. Visual analogue pain scores and patient-controlled morphine consumption were measured at specified times for 48 h. We were unable to detect any significant difference in either of the outcome measures for the two groups and thus were unable to demonstrate that epidural blockade using local anaesthetic and opioid has a pre-emptive effect. The concept of pre-emptive analgesia was first proposed following basic scientific research that showed that the central nervous system demonstrated plasticity and was not 'hard wired' [1]. Noxious stimuli could induce changes in neural function such as hyperexcitability or 'wind up' in the dorsal horn of the spinal cord [2]; 'wind up' may relate to the establishment of a subsequent pain memory. Blocking or reducing this process might lead to reduced analgesic requirement in the acute phase of an injury and the prevention of long-term neurological sequelae. The aim of this study was to establish whether pre-emptive epidural neural blockade using combined local anaesthetic and opioid could be shown to reduce pain experienced in the early postoperative period. MethodsFollowing local ethics committee approval and informed consent, 50 patients scheduled to undergo abdominal hysterectomy for benign disease were entered into the study. All patients were ASA 1 or 2 taking no concurrent analgesic medication and had no contraindications to epidural anaesthesia. The visual analogue scale (VAS) with endpoints labelled 'no pain' and 'worst pain possible' and the patient-controlled analgesia (PCA) machine were shown to the patients pre-operatively and their use explained. Each patient received temazepam 20 mg orally 1 h pre-operatively as premedication. In the anaesthetic room, an epidural catheter was sited at the L 2-3 interspace. General anaesthesia was induced with propofol 2 mg.kg À1 and vecuronium 0.1 mg.kg À1 was used to provide muscle relaxation. The trachea was intubated and the lungs ventilated with 66% nitrous oxide in oxygen and isoflurane was titrated to clinical need. No supplementary analgesia was given during anaesthesia. Patients were then randomly allocated to receive either 0.9% saline 16 ml (group A) or 0.5% bupivacaine 15 ml and fentanyl 50 mg (group B) via the epidural catheter 15 min prior to skin incision. All patients and personnel involved in patient management and data collection were blinded to the group allocation. Arterial blood pressure was measured prior to and at 5-min intervals f...
SummaryWe conducted a double blind, prospective, controlled trial comparing intubating conditions after induction with a propofol-ephedrine combination or propofol alone, followed by rocuronium. One hundred adult patients were randomly assigned to receive either propofol 2.5 mg.kg A1 and ephedrine 15 mg in combination or propofol 2.5 mg.kg A1 given over 30 s, followed by rocuronium 0.6 mg.kg A1 given over 5 s. Tracheal intubation was performed 1 min later. Jaw relaxation, vocal cord position and diaphragmatic response were used to assess intubation conditions. Tracheal intubation was successful and acceptable in all patients. There was a signi®cantly higher proportion of intubating conditions graded as ÔexcellentÕ in the propofol-ephedrine group (84%) than in the propofol group (32%) (p < 0.0001). Vocal cord position and response to intubation were signi®cantly better in the propofol-ephedrine group, although jaw relaxation was similar. Mean arterial pressure was maintained at pre-induction levels in the propofol-ephedrine group. In conclusion, induction with propofol and ephedrine in combination provided signi®cantly better intubating conditions than propofol alone, when followed by rocuronium.
It is common practice to mix opioids with hyperbaric bupivacaine in a single syringe before intrathecal injection of the mixture. Mixing these drugs may alter the density of the hyperbaric solution, affecting the spread of local anaesthetic and opioid. Forty-eight women having elective caesarean section under spinal anaesthesia were recruited to this double-blind, randomised trial. Group M (n=24) received 2 ml of 0.5% hyperbaric bupivacaine plus morphine 100 µg plus fentanyl 15 µg, mixed in a syringe prior to administration. Group S (n=24) received 2 ml of 0.5% bupivacaine through one syringe, followed by morphine 100 µg plus fentanyl 15 µg through a separate syringe. All patients received patient-controlled intravenous morphine for 24 hours postoperatively. Block characteristics, postoperative pain scores and morphine use were noted. The patients in Group M had higher levels of sensory block to cold than those in Group S (median T2 vs T3)(P=0.003). Five patients in Group M and none in Group S had a block to cold ≥T1 (P=0.02). There was no difference between groups in the incidence of hypotension, need for vasopressor or side-effects. Morphine consumption was significantly higher in group M (13.3±11.2 vs 6.2±7.2 mg, P=0.015). Mixing of fentanyl and morphine with hyperbaric bupivacaine results in a higher level of sensory block than sequential administration of bupivacaine then opioid and may be associated with higher postoperative opioid requirement.
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