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Intravenous lipid emulsion is, in some countries, the recommended treatment for local anaesthetic toxicity. Systemic local anaesthetic toxicity results in hypoxaemia and acidosis, and whether this influences the effects of lipid therapy on drug concentrations and cardiovascular recovery is currently unknown. Twenty anaesthetised pigs were given a 3 mg/kg bolus of levobupivacaine followed by a five-minute phase of hypoventilation and 1 mmol/kg of lactic acid over one minute. After lactic acid infusion, pigs were treated, in randomised order, with either 20% lipid emulsion or Ringer's acetate for 30 minutes: a 1.5 ml/kg bolus followed by a 0.25 ml/kg/minute infusion. Haemodynamic parameters were recorded and blood samples were collected for pharmacokinetic analysis. There was no difference between the groups in the area under the plasma levobupivacaine concentration–time curve (AUC) or between that and AUC of unentrapped levobupivacaine in the Lipid group, or in the plasma half-lives. The cardiovascular outcome and normalisation of the electrocardiogram were similar in both groups. Five pigs developed marked hypotension: one in both groups died, while two in the Lipid group and one in the Ringer group needed adrenaline. Administration of lipid emulsion did not improve cardiovascular recovery from levobupivacaine toxicity exacerbated by acidosis and hypoxaemia. Lipid emulsion did not entrap levobupivacaine or affect levobupivacaine pharmacokinetics.

Background and Objectives:: Ropivacaine is a potent local anesthetic that, experimentally at low concentrations, produces an effective block of pain conducting nerve fibers. Therefore, it was hypothesized that 0.1% and 0.2% ropivacaine would provide clinically adequate postoperative analgesia in continuous axillary plexus block. Methods:: Sixty patients (ASA I-II) scheduled for elective hand or forearm surgery received 5 mg/kg of 0.75% ropivacaine for axillary block using nerve stimulator technique. One hour later, in random order, a continuous infusion of either 0.1% ropivacaine (0.125 mg/kg/h), 0.2% ropivacaine (0.25 mg/kg/h) or saline 6 to 11 mL/h was started. Results:: The mean total ropivacaine dose for the surgical block was 5.1 to 5.2 mg/kg with the supplementation. All patients were pain free for the first 12 to 15 hours after the block. The need for postoperative analgesics during the infusion was similar in all groups. After the initial block, the maximum plasma concentrations (mean 2.5 @mg/mL) were measured at 45 or 60 minutes after injection. The highest individual plasma concentration was 4.2 @mg/mL. Despite the high venous peak concentration, no toxic reactions were observed. The mean peak plasma concentration (C"m"a"x) was 2.2 +/- 0.5 @mg/mL for saline, 2.6 +/- 0.8 @mg/mL for 0.1% ropivacaine, and 2.6 +/- 0.7 @mg/mL for 0.2% ropivacaine. During the continuous infusion of 24 hours, the ropivacaine concentration declined steadily. Conclusions: Ropivacaine is safe and effective for axillary brachial plexus block. The continuous infusion of 0.1% or 0.2% ropivacaine was no more beneficial than an infusion of saline in relieving postoperative pain in patients having elective hand surgery. None of the infusions were sufficient to adequately treat the patients' pain without the addition of adjunct agents.

Continuous supraclavicular brachial plexus blocks are useful for long surgical operations on the shoulder and upper extremily. Their usefulness can be increased with continuous infusions of local anesthetics through the same catheter for postoperative analgesia. Our technique includes the use of a commercial set (Contiplex; B. Braun Medical Inc, Melsungen, Germany and Bethlehem, PA). For shoulder surgery the most superficial trunk of the plexus is identified by using a nerve stimulator with a low current (0.2-0.3 mA) and motor response distal to the shoulder. The initial surgical anesthetic dose of 1% mepivacaine, 0.75% bupivacaine or 0.75% ropivacaine, with 5 @mg/mL epinephrine, is injected. Then the catheter is threaded as far as it can be advanced without obstruction (usually less than 1 cm past the tip of the cannula). To have a functional catheter for 24 to 48 hours, it must be tightly fixed to the skin with tape or sutures. For postoperative analgesia, an infusion of either 0.25% bupivacaine or 0.2% ropivacaine solution can be used. Complications from catheter use are rare but occasional intraarterial catheterizations and epidural blocks have been observed. A phrenic nerve block will always accompany a successful supraclavicular brachial plexus block and hemidiaphragmatic dysfunction can occur as long as the infusion continues.

The effects were studied, in eight healthy volunteers, of premedication with diazepam 0.14 mg kg−1 by mouth or hyoscine 6 μg kg−1 ³ morphine 0.2 mg kg 1 i.m., or no premedication, on toxic symptoms and plasma concentrations after rapid i.v. injection of lignocaine 1 mg kg−1. The α1-acid glycoprotein (AAG) and albumin plasma protein fractions were assessed. A variety of mild central nervous system (CNS) symptoms were experienced after the bolus of lignocaine. However, there was no correlation between premedication and degree of severity or number of CNS symptoms. The highest single arterial plasma concentration of lignocaine was 11.0 μg ml−1, 1 min after injection. There was no correlation between plasma concentration of lignocaine and occurrence of CNS symptoms. Furthermore, there was no correlation between AAG or albumin plasma concentrations and lignocaine plasma concentrations.