Epidural administration

Abstract: Effective analgesia for postoperative pain relief after major surgery has been a practical proposition with epidural administration of local anaesthetic (LA) and opioid drugs since the early 1980s. Although epidural administration is perceived by 80% of UK anaesthetists as the ideal analgesic technique for upper abdominal surgery, 34 there are many patients undergoing major surgery who do not receive this form of analgesia. In a recent survey of UK practice, only 15% of patients undergoing abdominal surgery had epidural analgesia in the 12 hospitals sampled. 31 The main factor which has limited the use of epidural analgesia has been the difficulty in making a reasonable risk/benefit analysis about the technique, which has resulted in clinicians constantly asking whether epidurals are effective for postoperative pain relief and whether the technique is safe. This review considers the efficacy and safety of epidural analgesia in patients recovering from major surgery and is based on a computerized search of the literature from 1976 to 2000 (EMBASE/Medline). The final section will deal with the organizational issues which need to be considered to maximize efficacy and safety and is based on the authors’ joint experience of supervising acute pain services (APS) in New Zealand and the UK; these services have been responsible for pain relief in over 20 000 patients nursed on general postoperative wards.

Abstract: In a randomized double-blind study of thirty grossly obese patients undergoing gastroplasty for weight reduction, the effects of intramuscular and epidural morphine were compared as regards analgesia, ambulation, gastrointestinal motility, early and late pulmonary function, duration of hospitalization, and occurrence of deep vein thrombosis in the postoperative period. The patients were operated on under thoracic epidural block combined with light endotracheal anesthesia. A six-grade scale was devised to quantify postoperative mobilization. A radioactive isotope method using 99mTc -plasmin was employed to detect postoperative deep vein thrombosis. For 14 hr after the first analgesic injection, respiratory frequency was noted every 15 min and arterial blood gases were measured hourly. Peak expiratory flow was recorded daily until the patient was discharged from hospital. Spirometry was performed the day before and the day after surgery. Plasma concentrations of morphine were measured after both intramuscular and epidural administration. Both intramuscular and epidural morphine gave effective analgesia, but the average dose of intramuscular morphine was up to seven times greater than that required by the epidural route. A larger number of patients receiving epidural morphine postoperatively were able to sit, stand, or walk unassisted within 6, 12, and 24 hr, respectively. Being alert and more mobile as a result of superior postoperative analgesia from epidural morphine, patients in this group benefited more from vigorous physiotherapy routine, which resulted in fewer pulmonary complications. Furthermore, earlier postoperative recovery of peak expiratory flow and bowel function presumably contributed to a significantly shorter hospitalization in patients receiving epidural morphine. There was no evidence of prolonged respiratory depression in this high-risk category of patients. The 99mTc -plasmin tests revealed no significant difference between the two groups.

Abstract: UNLABELLED Ropivacaine is a long-acting, enantiomerically pure (S-enantiomer) amide local anaesthetic with a high pKa and low lipid solubility which blocks nerve fibres involved in pain transmission (Adelta and C fibres) to a greater degree than those controlling motor function (Abeta fibres). The drug was less cardiotoxic than equal concentrations of racemic bupivacaine but more so than lidocaine (lignocaine) in vitro and had a significantly higher threshold for CNS toxicity than racemic bupivacaine in healthy volunteers (mean maximum tolerated unbound arterial plasma concentrations were 0.56 and 0.3 mg/L, respectively). Extensive clinical data have shown that epidural ropivacaine 0.2% is effective for the initiation and maintenance of labour analgesia, and provides pain relief after abdominal or orthopaedic surgery especially when given in conjunction with opioids (coadministration with opioids may also allow for lower concentrations of ropivacaine to be used). The drug had efficacy generally similar to that of the same dose of bupivacaine with regard to pain relief but caused less motor blockade at low concentrations. Lumbar epidural administration of 20 to 30ml ropivacaine 0.5% provided anaesthesia of a similar quality to that achieved with bupivacaine 0.5% in women undergoing caesarean section, but the duration of motor blockade was shorter with ropivacaine. For lumbar epidural anaesthesia for lower limb or genitourinary surgery, comparative data suggest that higher concentrations of ropivacaine (0.75 or 1.0%) may be needed to provide the same sensory and motor blockade as bupivacaine 0.5 and 0.75%. In patients about to undergo upper limb surgery, 30 to 40ml ropivacaine 0.5% produced brachial plexus anaesthesia broadly similar to that achieved with equivalent volumes of bupivacaine 0.5%, although the time to onset of sensory block tended to be faster and the duration of motor block shorter with ropivacaine. Ropivacaine had an adverse event profile similar to that of bupivacaine in clinical trials. Several cases of CNS toxicity have been reported after inadvertent intravascular administration of ropivacaine, but only 1 case of cardiovascular toxicity has been reported to date. The outcome of these inadvertent intravascular administrations was favourable. CONCLUSION Ropivacaine is a well tolerated regional anaesthetic with an efficacy broadly similar to that of bupivacaine. However, it may be a preferred option because of its reduced CNS and cardiotoxic potential and its lower propensity for motor block.