Gathering evidence from animal experiments, an editorial in this journal and published human case reports culminated in the Association of Anaesthetists of Great Britain and Ireland recommending in August 2007 that lipid emulsion be immediately available to all patients given potentially cardiotoxic doses of local anaesthetic drugs. This development offered an opportunity to track the adoption of an innovation by anaesthetists in the UK and to gauge the effects of guidelines. Two surveys, each of 66 NHS hospitals delivering acute care within London and its penumbra, examined the adoption of lipid emulsion therapy. After the publication of the editorial in autumn 2006, the spread of 'lipid rescue' was rapid. The timing of the adoption and the impetus for innovation varied substantially between the sampled hospitals. When the formal guidelines were published, approximately half of the hospitals surveyed did not have lipid rescue. Of those that subsequently adopted it, half attributed their decision to the guidelines. At the end of 2007, there remained a small number of hospitals that had yet to adopt lipid rescue. Lipid rescue's adoption by anaesthetists in the UK offers a rare example of swift uptake of an innovation. National guidelines accelerated the adoption of innovation by some hospitals.
◊ Reviewed by A. Van Zundert, MD, PhD, FRCA
Professor, Dept. of Anesthesiology Catharina Hospital,
Brabant Medical School, Eindhoven, The Netherlands
For years anesthesiologists fear the potential devastating reactions to wrongly injected local anaesthetics. Too much drug in the subarachnoid potentially leads to high or even total spinal blocks and accidental intravascular injections or overdose of local anesthetics may end in cardiac arrest. Large doses of local anesthetics, especially of the long-acting ones such as bupivacaine, may produce asystoles or ventricular fibrillation, even 15 minutes after administration, for which immediate cardiopulmonary resuscitation is needed. Even with immediate action a successful outcome is not guaranteed.
In 1998, the infusion of a lipid emulsion was shown to increase the survival rates of rats and dogs that have been resuscitated after an overdose of bupivacaine. Later, similar studies were done with other local anesthetics. Local anesthetics have a potent depressant effect of electrical conduction, which may predispose the heart to reentry types of arrhythmias. Weinberg et al. clearly demonstrated that lipid infusions not only increase the dose of bupivacaine required to produce asystoles, but also improve survival. As a plausible mechanism, the lipid emulsion may extract lipophilic bupivacaine from the aequeous plasma phase, or diffuses directly into tissue and interacts with bupivacaine at that level.
Preferably, lipid rescue is administered via a central venous catheter, but in its absence, peripheral veins can also be used. A 20% lipid emulsion bolus over one minute is recommended with an initial dose of 1 ml/kg, immediately followed by 1 mg atropine and 1 mg epinephrine. Chest compressions should not be interrupted. The intralipid bolus can be repeated with a maximum of 4 ml/kg/min. The lipid infusion is to be maintained at a rate of 0.5 ml/kg/min until hemodynamic recovery.
Lipid infusions act as an antidote to local anaesthetic intoxication, and should be readily at hand like 0-negative blood and dantrolene. It has a low cost and a shelf life of up to one year. The guidelines for the management of severe local anaesthetic toxicity provide essential information, which should be available in all hospitals, particularly in units where local anaesthetics are administered.
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