Anaesthesia
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This paper describes practical aspects relating to the safe use of target controlled infusion systems in anaesthesia. Consideration is given to the correct use of syringes and infusion lines for any target controlled infusion system. ⋯ Particular features of these systems are discussed. Finally, the practical consequences of possible misuse of infusion systems incorporating pharmacokinetic models are considered.
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The pharmacokinetic profile of propofol is an advantage in neurosurgery, where the rapid return of cognitive function is essential for an early postoperative assessment of neurological status. Administration of propofol by 'Diprifusor' target controlled infusion allows induction of anaesthesia in neurosurgical patients without significant reduction of mean arterial pressure or occurrence of apnoeic episodes. This short paper describes our experience of 'Diprifusor' target controlled infusion for neuroanaesthesia in a series of 20 patients undergoing craniotomy for excision of epileptic foci. The results have been compared with ten similar operations where propofol infusion was controlled manually.
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Review Case Reports
Recurrent respiratory depression after total intravenous anaesthesia with propofol and alfentanil.
Since first commented upon by Lamarche in 1984, several cases of recurrent respiratory arrest after alfentanil infusions have been reported. In all these cases the alfentanil infusions have been used to supplement conventional anaesthetic techniques with nitrous oxide and/or inhalational agents and in most cases rather high total alfentanil doses have been administered. We have seen two cases of severe recurrent respiratory depression in healthy patients after relatively minor procedures performed under total intravenous anaesthesia with propofol-alfentanil infusions, air-oxygen ventilation and muscle relaxation, where the alfentanil doses administered were quite small. These cases are presented in detail and compared within a tabulated presentation with the earlier published cases of alfentanil-related recurrent respiratory depression.
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The availability of fast-acting intravenous drugs for anaesthesia has encouraged anaesthetists to gain a practical understanding of the pharmacodynamics and pharmacokinetics of these drugs to optimise their administration. 'Diprifusor' technology uses pharmacokinetic modelling to control the infusion rate of a pump, providing the anaesthetist with direct control of the blood concentration rather than indirect control by the infusion rate. The 'Diprifusor' electronics module is a dual microprocessor component that can be incorporated into an infusion pump to provide this mode of administration. This paper describes the module's infusion control system, prefilled syringe recognition system and the safety aspects addressed by the design.
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Randomized Controlled Trial Clinical Trial
Dorsal column function after epidural and spinal blockade: implications for the safety of walking following low-dose regional analgesia for labour.
Walking after regional blockade for labour using low-dose combinations of bupivacaine and fentanyl is possible due to the maintenance of lower limb motor power. In order to investigate concerns that dorsal column function, important in maintaining balance, is impaired after such techniques, clinical assessment of lower limb proprioception and vibration sense was evaluated in parturients after either low-dose epidural (n = 30) or spinal blockade (n = 30) for labour analgesia and compared with spinal anaesthesia (n = 30) for elective Caesarean section using a larger total dose of local anaesthetic. Of the patients receiving low-dose regional labour analgesia 7% (n = 4) had abnormal dorsal column function compared with 97% (n = 29) receiving spinal anaesthesia for Caesarean section (p < 0.001). ⋯ There were no significant differences between the low-dose groups with respect to sensory block, motor block or dorsal column function. Overall, 90% of patients receiving low-dose bupivacaine/fentanyl regional labour analgesia had both normal lower limb motor power and dorsal column function. Assessment of these parameters is recommended before allowing patients to walk after low-dose regional techniques for labour.