The effects of intravenous lipid emulsion on hemodynamic recovery and myocardial cell mitochondrial function after bupivacaine toxicity in anesthetized pigs.

Local anesthetic toxicity is thought to be mediated partly by inhibition of cardiac mitochondrial function. Intravenous (i.v.) lipid emulsion may overcome this energy depletion, but doses larger than currently recommended may be needed for rescue effect. In this randomized study with anesthetized pigs, we compared the effect of a large dose, 4 mL/kg, of i.v. 20% Intralipid® ( n = 7) with Ringer's acetate ( n = 6) on cardiovascular recovery after a cardiotoxic dose of bupivacaine. We also examined mitochondrial respiratory function in myocardial cell homogenates analyzed promptly after needle biopsies from the animals. Bupivacaine plasma concentrations were quantified from plasma samples. Arterial blood pressure recovered faster and systemic vascular resistance rose more rapidly after Intralipid than Ringer's acetate administration ( p < 0.0001), but Intralipid did not increase cardiac index or left ventricular ejection fraction. The lipid-based mitochondrial respiration was stimulated by approximately 30% after Intralipid ( p < 0.05) but unaffected by Ringer's acetate. The mean (standard deviation) area under the concentration-time curve (AUC) of total bupivacaine was greater after Intralipid (105.2 (13.6) mg·min/L) than after Ringer's acetate (88.1 (7.1) mg·min/L) ( p = 0.019). After Intralipid, the AUC of the lipid-un-entrapped bupivacaine portion (97.0 (14.5) mg·min/L) was 8% lower than that of total bupivacaine ( p < 0.0001). To conclude, 4 mL/kg of Intralipid expedited cardiovascular recovery from bupivacaine cardiotoxicity mainly by increasing systemic vascular resistance. The increased myocardial mitochondrial respiration and bupivacaine entrapment after Intralipid did not improve cardiac function.

Intravenous lipid emulsion for levobupivacaine intoxication in acidotic and hypoxaemic pigs.

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 in one minute. After lactic acid infusion, pigs were treated, in randomised order, with either 20% lipid emulsion or Ringer's acetate for 30 min: 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.

Incidence of severe local anaesthetic toxicity and adoption of lipid rescue in Finnish anaesthesia departments in 2011-2013.

BACKGROUND: Although the incidence of severe local anaesthetic systemic toxicity (LAST) has been declining, the risk of LAST still remains. There are no national treatment guidelines for LAST in Finland. We performed a national survey of the occurrence of LAST and its treatment in 2011-2013. METHODS: A structured electronic questionnaire was sent to the anaesthesia department chiefs of all Finnish public hospitals (n = 45) in spring 2014. We collected information about the occurrence and outcome of LASTs and existence of treatment protocols. RESULTS: The questionnaire response rate was 100% covering approximately 95% of all regional anaesthesias managed by anaesthesiologists in Finnish hospitals. The total number of regional anaesthesias, excluding spinal anaesthesia, performed by anaesthesiologists was approximately 211,700 during the survey period. Fifteen cases of LAST were reported (0.7 : 10,000); all patients recovered without negative sequelae. Fourteen patients, in five of whom ultrasound guidance had been applied, developed central nervous system toxicity symptoms and only one cardiac symptoms. Lipid emulsion was given to this latter patient, and to four of the other 14. The relative risk (95% confidence intervals) for occurrence of LAST in non-academic hospital vs. university hospitals was 3.3 (1.0-10.3; P = 0.04). Treatment protocols for LAST included lipid emulsion in 47% of the departments. CONCLUSIONS: The incidence of LAST in Finland is very low. Several departments have adopted lipid emulsion treatment for LAST despite lack of national recommendations and knowledge of the possible mechanism of action.