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...

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An admixture of thiopentone and propofol was evaluated against propofol for laryngeal mask airway (LMA) insertion. Eighty-one ASA 1 and 2 18-to 65-year-old patients, premedicated with 7.5 mg midazolam orally were assigned randomly to receive either propofol 1% or an admixture of thiopentone and propofol (1.25% and 0.5% respectively), both at a dose of 0.25 ml.kg -1 . Satisfactory conditions for insertion were achieved with the admixture, which was comparable to propofol (73% vs 85%, P>0.05). There was no statistical difference in the incidence or severity of gagging, coughing, inadequate jaw relaxation and laryngospasm. The incidence of hypotension was lower in the admixture group (51% vs 78%, P=0.02). The duration of apnoea was not different between the admixture and propofol group (mean 103s vs 109 s respectively, P>0.05). We conclude that thiopentone/propofol admixture can be a suitable alternative to propofol for LMA insertion, producing less hypotension while allowing cost savings of up to 45%.An admixture of thiopentone and propofol (1.25% and 0.5% respectively) can produce suitable conditions compared to propofol 1%, for laryngeal mask insertion. In addition to cost containment, the admixture also produces less hypotension.

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