Local anaesthesia is safely used for many plastic surgery procedures limited by the dose that can be administered before plasma concentration causes systemic toxicity. As long as inadvertent intravascular injection is avoided, the plasma concentration reflects the rate of absorption less than the metabolism. Local anaesthetic systemic toxicity (LAST) occurs in a well-defined clinical sequence and includes tinnitus, lightheadedness, and circumoral tingling. At higher plasma levels unconsciousness, respiratory arrest and cardiovascular depression can occur [5
The absorption of local anaesthetic varies by injection site, being highest after intercostal blocks followed by epidural/caudal, brachial plexus, femoral/sciatic block and lowest when injected subcutaneously. This reflects the vascular supply of each tissue. Despite different tissue absorption rates, the maximum dose recommendations are presented as exact milligram per kilogram (mg/kg) doses.
20% of intralipid is an emulsion consisting of 200
g of purified soybean oil, 12
g purified egg phospholipids and 22
g anhydrous glycerol. It has been in medical use since 1962 as a source of omega-3 and -6 fatty acids in parenteral nutrition [6
]. Its use in the treatment of LAST was a chance discovery by Weinberg in 1998 and is now part of the treatment pathway for the management of local anaesthetic-induced toxicity in the United Kingdom [7
]. It is believed that intralipid forms a “lipid sink,” that is, an expanded intravascular lipid phase that acts to absorb the circulating lipophilic drug which reduces the amount of unbound free drug to bind to the myocardium [6
]. In addition to its use in LAST, lipid emulsion therapy has been successfully used in the treatment of toxicity from other lipophilic drugs like chlorpromazine, beta-blockers, and calcium channel antagonists [9
The maximum recommended dose for levobupivacaine is 2 or 3
mg/kg or 150
mg. We used 350
mg over a four-hour period, which was almost two and a half times the recommended maximum dose. Although this is a large quantity, it is less than what is reported to be safe in tumescent anaesthesia where up to twenty times the maximum local anaesthetic dosage is used [10
]. The incremental nature of the injections spreads the absorption, and unlike liposuction significant quantities of the local anaesthetic were excised within the specimen.
Did we need the intralipid? We cannot say for sure, however, given it has minimal side effects that it seemed prudent. There is also a possibility that the morbidly obese might behave as a tumescent patient due to increased subcutaneous fat and odema.
The use of Hyalase is controversial in cases of malignancy; however, literature review revealed no evidence of definitive spread of malignant cells. Additionally the ring block was administered remotely from the tumor and not into the lesion itself.
This is the first reported use of intralipid prophylactically in this subgroup of patients in world literature. Anaesthesia of the required area, tumor clearance, and healed wounds were achieved without any reported significant anaesthetic side effects. This could be a useful addition to the armamentarium in plastic surgery. In the unfit patient with multiple comorbidities the described technique can be used to achieve anaesthesia of the required area, avoiding the risks of invasive anaesthetic procedures.