Resuscitation with lipid emulsion: dose-dependent recovery from cardiac pharmacotoxicity requires a cardiotonic effect.
BACKGROUND
Recent publications have questioned the validity of the "lipid sink" theory of lipid resuscitation while others have identified sink-independent effects and posed alternative mechanisms such as hemodilution. To address these issues, the authors tested the dose-dependent response to intravenous lipid emulsion during reversal of bupivacaine-induced cardiovascular toxicity in vivo. Subsequently, the authors modeled the relative contribution of volume resuscitation, drug sequestration, inotropy and combined drug sequestration, and inotropy to this response with the use of an in silico model.


METHODS
Rats were surgically prepared to monitor cardiovascular metrics and deliver drugs. After catheterization and instrumentation, animals received a nonlethal dose of bupivacaine to produce transient cardiovascular toxicity, then were randomized to receive one of the four treatments: 30% intravenous lipid emulsion, 20% intravenous lipid emulsion, intravenous saline, or no treatment (n = 7 per condition; 28 total animals). Recovery responses were compared with the predictions of a pharmacokinetic-pharmacodynamic model parameterized using previously published laboratory data.


RESULTS
Rats treated with lipid emulsions recovered faster than did rats treated with saline or no treatment. Intravenous lipid emulsion of 30% elicited the fastest hemodynamic recovery followed in order by 20% intravenous lipid emulsion, saline, and no treatment. An increase in arterial blood pressure underlay the recovery in both lipid emulsion-treated groups. Heart rates remained depressed in all four groups throughout the observation period. Model predictions mirrored the experimental recovery, and the model that combined volume, sequestration, and inotropy predicted in vivo results most accurately.


CONCLUSIONS
Intravenous lipid emulsion accelerates cardiovascular recovery from bupivacaine toxicity in a dose-dependent manner, which is driven by a cardiotonic response that complements the previously reported sequestration effect.
From the Department of Anesthesiology, University of Illinois College of Medicine, Chicago, Illinois (M.R.F., R.R., and G.W.); Research and Development Service, Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois (M.R.F., R.R., I.R., and G.W.); University of Illinois College of Medicine, Chicago, Illinois (M.R.F. and B.Z.); Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois (B.S.A.); University of Illinois College of Medicine, Peoria, Illinois (J.L.); and Section of Pulmonary, Critical Care, Sleep, and Allergy Medicine, Department of Medicine, University of Illinois College of Medicine, Chicago, Illinois (I.R.).
Michael R
MR
Fettiplace
Belinda S
BS
Akpa
Richard
R
Ripper
Brian
B
Zider
Jason
J
Lang
Israel
I
Rubinstein
Guy
G
Weinberg
D000779:Anesthetics, Local / Q000633:toxicity; D000818:Animals; D002045:Bupivacaine / Q000633:toxicity*; D002316:Cardiotonic Agents / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005217:Fat Emulsions, Intravenous / Q000627:therapeutic use*; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006323:Heart Arrest / Q000139:chemically induced* / Q000628:therapy*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012151:Resuscitation / Q000379:methods*; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors; D016896:Treatment Outcome
D000779:Anesthetics, Local; D002316:Cardiotonic Agents; D005217:Fat Emulsions, Intravenous; D012965:Sodium Chloride; D002045:Bupivacaine