40 yo F, no PMHx, brought to ED for acute onset of shortness of breath, nausea, and vomiting. She was undergoing hair transplantation for traction alopecia at an outpatient surgi-center. BP 79/40, satting 75% on RA. Bedside sono shows you a grossly reduced EF with poor myocardial contractility. What is happening to her?
What is the maximum dose of lidocaine with epinephrine that you can inject into the peripheral tissues safely?
ANSWER:
- Local Anesthetic Systemic Toxicity (LAST)
- Maximum dose of lidocaine with epinephrine that can be injected into the peripheral tissues is 5-7 mg/kg.
Lidocaine is the most commonly used local anesthetic agent for wound repair and short procedures because it has a rapid onset following local infiltration (seconds – minutes) and short duration of action (maximum of 60 minutes). It can also be used for regional blocks (peak anesthesia in 4-6 min). The addition of epinephrine leads to local vasoconstriction, which increases the duration of action to hours. Some argue that the addition of epinephrine may lead to delayed healing and potentially decrease the resistance to infection. But the old practice of not using epinephrine in distal extremities has been dispelled.
Local Anesthetic Systemic Toxicity (LAST) is a rare complication, but when it causes cardiac toxicity as it did in the example above, the patient needs prompt critical supportive care – BIPAP/mechanical intubation, pressors, and some studies suggest that intralipid. Although lipid rescue mechanism of action is poorly understood, it is supposed that it aids in the removal of lipophilic toxins from affected tissues.
Cave G, Harvey M; Harvey (September 2009). “Intravenous lipid emulsion as antidote beyond local anesthetic toxicity: a systematic review”. Acad Emerg Med 16 (9): 815–24
Simon BC and HG Hern. Wound Management Principles: in Marx JA, Hockberger RS, Walls RM, et al (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, ed 8. Philadelphia, Saunders, 2014, (Ch) 59:p 751-66.
