Lipidlösungen zur Therapie der Lokalanästhetikaintoxikation

[Update on the pharmacology and effects of local anesthetics]

Local anesthetics (LA) are broadly used in all disciplines and it could be considered that relatively little is reflected on the mechanisms of action of this old substance group. However, several molecular mechanisms of LAs mediating wanted and unwanted effects remain to be explored. Furthermore, the number of indications for application of LAs seems to be expanding. The local anesthetic effect of LAs is primarily mediated by a potent inhibition of voltage-gated sodium channels. However, this effect is due to much more than the interaction of LAs with one single molecule. Most recent studies indicated that the development of selective local anesthetics might be possible and LAs also interact with several other membrane molecules. Although the relevance of these effects is still unclear, they might play a role in systemic analgesia, tissue protection and anti-inflammatory effects of LA. The therapeutic index of systemically applied LA is very narrow. Systemic application is formally not permitted because the impending systemic toxicity is still a life-threatening complication. Although the cardiac and central nervous toxicity at least partly result from an unselective block of neuronal and cardiac sodium channels, preclinical studies suggest the involvement of several mechanisms. A local LA toxicity is less clinically impressive; however, all LAs induce a significant tissue toxicity for which the underlying mechanisms have been partly identified. This review reports on recent findings on mechanisms and on the clinical relevance of some LA-induced effects which are of relevance for anesthesiological activities.

[Anesthesia for geriatric patients : Part 2: anesthetics, patient age and anesthesia management]

Part 2 of this review on geriatric anesthesia primarily describes the multiple influences of age on the pharmacokinetics and pharmacodynamics of different anesthetic agents and their impact on clinical practice. In the elderly the demand for opioids is reduced by almost 50% and with total intravenous anesthesia the dosages of propofol and remifentanil as well as recovery times are more determined by patient age than by body weight. As a result depth of anesthesia monitoring is recommended for geriatric patients to individually adjust the dosing to patients needs. With muscle relaxants both delayed onset of action and prolonged duration of drug effects must be considered with increasing age and as this may lead to respiratory complications, neuromuscular monitoring is highly recommended. The following measures appear to be beneficial for geriatric patients: thorough preoperative assessment, extended hemodynamic monitoring, use of short-acting anesthetics in individually adjusted doses best tailored by depth of anesthesia monitoring, intraoperative normotension, normothermia and normocapnia, complete neuromuscular recovery at the end of the procedure and well-planned postoperative pain management in order to reduce or avoid the use of opioids.

Resuscitation strategies from bupivacaine-induced cardiac arrest

OBJECTIVES

Local anesthetic (LA) intoxication with cardiovascular arrest is a potential fatal complication of regional anesthesia. Lipid resuscitation has been recommended for the treatment of LA-induced cardiac arrest. Aim of the study was to compare four different rescue regimens using epinephrine and/or lipid emulsion and vasopressin to treat cardiac arrest caused by bupivacaine intoxication.

METHODS

Twenty-eight piglets were randomized into four groups (4 × 7), anesthetized with sevoflurane, intubated, and ventilated. Bupivacaine was infused with a syringe driver via central venous catheter at a rate of 1 mg·kg(-1)·min(-1) until circulatory arrest. Bupivacaine infusion and sevoflurane were then stopped, chest compression was started, and the pigs were ventilated with 100% oxygen. After 1 min, epinephrine 10 μg·kg(-1) (group 1), Intralipid(®) 20% 4 ml·kg(-1) (group 2), epinephrine 10 μg·kg(-1) + Intralipid(®) 4 ml·kg(-1) (group 3) or 2 IU vasopressin + Intralipid(®) 4 ml·kg(-1) (group 4) were administered. Secondary epinephrine doses were given after 5 min if required.

RESULTS

Survival was 71%, 29%, 86%, and 57% in groups 1, 2, 3, and 4. Return of spontaneous circulation was regained only by initial administration of epinephrine alone or in combination with Intralipid(®). Piglets receiving the combination therapy survived without further epinephrine support. In contrast, in groups 2 and 4, return of spontaneous circulation was only achieved after secondary epinephrine rescue.

CONCLUSIONS

In cardiac arrest caused by bupivacaine intoxication, first-line rescue with epinephrine and epinephrine + Intralipid(®) was more effective with regard to survival than Intralipid(®) alone and vasopressin + Intralipid(®) in this pig model.

Comparison of epinephrine vs lipid rescue to treat severe local anesthetic toxicity - an experimental study in piglets

OBJECTIVES

Local anesthetic (LA) intoxication with severe hemodynamic compromise is a potential catastrophic event. Lipid resuscitation has been recommended for the treatment of LA-induced cardiac arrest. However, there are no data about effectiveness of Intralipid for the treatment of severe cardiovascular compromise prior to cardiac arrest. Aim of this study was to compare effectiveness of epinephrine and Intralipid for the treatment of severe hemodynamic compromise owing to bupivacaine intoxication.

METHODS

  Piglets were anesthetized with sevoflurane, intubated, and ventilated. Bupivacaine was infused with a syringe driver via a central venous catheter at a rate of 1 mg·kg(-1) ·min(-1) until invasively measured mean arterial pressure (MAP) dropped to 50% of the initial value. Bupivacaine infusion was then stopped, and epinephrine 3 μg·kg(-1) (group 1), Intralipid(®) 20% 2 ml·kg(-1) (group 2), or Intralipid 20% 4 ml·kg(-1) (group 3) was immediately administered. Survival, hemodynamic course, and ET(CO2) were recorded.

RESULTS

  Twenty-one piglets (3 × 7), with median age of 26 days (19-43) and weighing 4.9 kg (4.3-5.8), were investigated. All animals in group 1 (100%) but only four of seven (57%) piglets in group 2 and group 3, respectively, survived. Normalization of hemodynamic parameters (HR, MAP) and ET(CO2) was fastest in group 1 with all piglets achieving HR and MAP values at or above baseline within 1 min.

CONCLUSION

  For the treatment of severe hemodynamic compromise owing to bupivacaine intoxication in piglets, first-line rescue with epinephrine was more effective than Intralipid with regard to survival as well as normalization of hemodynamic parameters and ET(CO2) .