Binding of local anaesthetics to the lipid emulsion Clinoleic™ 20%

Guidelines for Monitoring and Management of Pediatric Patients Before, During, and After Sedation for Diagnostic and Therapeutic Procedures

The safe sedation of children for procedures requires a systematic approach that includes the following: no administration of sedating medication without the safety net of medical/dental supervision, careful presedation evaluation for underlying medical or surgical conditions that would place the child at increased risk from sedating medications, appropriate fasting for elective procedures and a balance between the depth of sedation and risk for those who are unable to fast because of the urgent nature of the procedure, a focused airway examination for large (kissing) tonsils or anatomic airway abnormalities that might increase the potential for airway obstruction, a clear understanding of the medication's pharmacokinetic and pharmacodynamic effects and drug interactions, appropriate training and skills in airway management to allow rescue of the patient, age- and size-appropriate equipment for airway management and venous access, appropriate medications and reversal agents, sufficient numbers of appropriately trained staff to both carry out the procedure and monitor the patient, appropriate physiologic monitoring during and after the procedure, a properly equipped and staffed recovery area, recovery to the presedation level of consciousness before discharge from medical/dental supervision, and appropriate discharge instructions. This report was developed through a collaborative effort of the American Academy of Pediatrics and the American Academy of Pediatric Dentistry to offer pediatric providers updated information and guidance in delivering safe sedation to children.

Low dose Intralipid resuscitation improves survival compared to ClinOleic in propranolol overdose in rats

Background

Medication overdose is a prevalent issue and despite mixed reports of efficacy, the use of intravenous lipid emulsions, notably Intralipid^®, for the management of toxicity from lipid-soluble drugs is becoming increasingly prevalent. Whether alternative lipid emulsion formulations have similar efficacy for resuscitation compared to Intralipid is not known. Here, we compared the efficacy of Intralipid and ClinOleic^® for resuscitation following overdose with the lipid-soluble beta-adrenergic antagonist propranolol.

Methods

Male Sprague-Dawley rats (age 3–4 months) were anesthetized with isoflurane and instrumented for direct hemodynamic assessments. In Study One, rats (n = 22) were pre-treated with Intralipid 20% (n = 12) or ClinOleic 20% (n = 10) to determine whether the hemodynamic effects of propranolol could be prevented. In Study Two, rats were randomly assigned to Intralipid 20% (1, 2, or 3 mL/kg IV, n = 21) or ClinOleic 20% (1, 2, or 3 mL/kg IV, n = 20) resuscitation groups following propranolol overdose (15 mg/kg IV). In Study Three the effect of Intralipid 20% (1 mL/kg IV, n = 3) and ClinOleic 20% (1 mL/kg IV, n = 3) in the absence of propranolol was investigated. The primary endpoint in all studies was survival time (up to a maximum of 120 minutes), and secondary endpoints were time to achieve 50%, 75%, and 90% of baseline hemodynamic parameters.

Results

In Study One, pre-treatment with Intralipid prior to propranolol administration resulted in prolonged survival compared to pre-treatment with ClinOleic at low doses (1 mL/kg; P = 0.002), but provided no benefit at higher doses (3 mL/kg; P = 0.95). In Study Two, Intralipid conferred a survival advantage over ClinOleic, with 18/21 rats surviving 120 minutes in the Intralipid group and only 4/20 survivors in the ClinOleic group (P<0.0001). Median survival times (with interquartile ranges) for rats treated with Intralipid, and ClinOleic, and saline were 120 (80.5–120) min, 21.5 (3.25–74.5) min, and 1 (0.25–2.5) min respectively (P<0.001). Only 3/21 rats in the Intralipid group survived less than 30 minutes, whereas 12/20 ClinOleic treated rats had survival times of less than 30 minutes. The number of rats achieving 75%, and 90% of baseline mean arterial pressure was also greater in the Intralipid group (P<0.05 for both values). Treatment in Study Three did not alter survival times.

Conclusions

Low-dose Intralipid (1, 2, or 3 mL/kg IV) confers a survival advantage up to 120 minutes post-propranolol overdose (the end-point of the experiment) and better hemodynamic recovery compared to ClinOleic (1, 2, or 3 mL/kg IV) in rats with propranolol overdose. As health care centres choose alternate intravenous lipid emulsions, limited availability of Intralipid could impact efficacy and success of overdose treatment for lipid-soluble drugs.

Lipid emulsion in local anesthetic toxicity

PURPOSE OF REVIEW

Enthusiasm for regional anesthesia has been driven by multimodal benefits to patient outcomes. Despite widespread awareness and improved techniques (including the increasing use of ultrasound guidance for block placement), intravascular sequestration and the attendant risk of local anesthetic systemic toxicity (LAST) remains. Intravenous lipid emulsion (ILE) for the treatment of LAST has been endorsed by anesthetic regulatory societies on the basis of animal study and human case report data. The accumulated mass of reporting now permits objective interrogation of published literature.

RECENT FINDINGS

Although incompletely elucidated the mechanism of action for ILE in LAST seemingly involves beneficial effects on initial drug distribution (i.e., pharmacokinetic effects) and positive cardiotonic and vasoactive effects (i.e., pharmacokinetic effects) acting in concert. Recent systematic review by collaborating international toxicologic societies have provided reserved endorsement for ILE in bupivacaine-induced toxicity, weak support for ILE use in toxicity from other local anesthetics, and largely neutral recommendation for all other drug poisonings. Work since publication of these recommendations has concluded that there is a positive effect on survival for ILE when animal models of LAST are meta-analyzed and evidence of a positive pharmacokinetic effect for lipid in human models of LAST.

SUMMARY

Lipid emulsion remains first-line therapy (in conjunction with standard resuscitative measures) in LAST. Increasing conjecture as to the clinical efficacy of ILE in LAST, however, calls for high-quality human data to refine clinical recommendations.

Lipid Emulsion for Treating Local Anesthetic Systemic Toxicity

Lipid emulsion has been shown to be an effective treatment for systemic toxicity induced by local anesthetics, which is reflected in case reports. A systemic review and meta-analysis confirm the efficacy of this treatment. Investigators have suggested mechanisms associated with the lipid emulsion-mediated recovery of cardiovascular collapse caused by local anesthetic systemic toxicity; these mechanisms include lipid sink, a widely accepted theory in which highly soluble local anesthetics (particularly bupivacaine) are absorbed into the lipid phase of plasma from tissues (e.g., the heart) affected by local-anesthetic-induced toxicity; enhanced redistribution (lipid shuttle); fatty acid supply; reversal of mitochondrial dysfunction; inotropic effects; glycogen synthase kinase-3β phosphorylation associated with inhibition of the mitochondrial permeability transition pore opening; inhibition of nitric oxide release; and reversal of cardiac sodium channel blockade. The current review includes the following: 1) an introduction, 2) a list of the proposed mechanisms, 3) a discussion of the best lipid emulsion treatment for reversal of local anesthetic toxicity, 4) a description of the effect of epinephrine on lipid emulsion-mediated resuscitation, 5) a description of the recommended lipid emulsion treatment, and 6) a conclusion.

Guidelines for Monitoring and Management of Pediatric Patients Before, During, and After Sedation for Diagnostic and Therapeutic Procedures: Update 2016

The safe sedation of children for procedures requires a systematic approach that includes the following: no administration of sedating medication without the safety net of medical/dental supervision, careful presedation evaluation for underlying medical or surgical conditions that would place the child at increased risk from sedating medications, appropriate fasting for elective procedures and a balance between the depth of sedation and risk for those who are unable to fast because of the urgent nature of the procedure, a focused airway examination for large (kissing) tonsils or anatomic airway abnormalities that might increase the potential for airway obstruction, a clear understanding of the medication's pharmacokinetic and pharmacodynamic effects and drug interactions, appropriate training and skills in airway management to allow rescue of the patient, age- and size-appropriate equipment for airway management and venous access, appropriate medications and reversal agents, sufficient numbers of staff to both carry out the procedure and monitor the patient, appropriate physiologic monitoring during and after the procedure, a properly equipped and staffed recovery area, recovery to the presedation level of consciousness before discharge from medical/dental supervision, and appropriate discharge instructions. This report was developed through a collaborative effort of the American Academy of Pediatrics and the American Academy of Pediatric Dentistry to offer pediatric providers updated information and guidance in delivering safe sedation to children.

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.

Comparison of Effects of Separate and Combined Sugammadex and Lipid Emulsion Administration on Hemodynamic Parameters and Survival in a Rat Model of Verapamil Toxicity

BACKGROUND

Toxicity of calcium channel blockers leads to high patient mortality and there is no effective antidote. The benefit of using 20% lipid emulsion and sugammadex has been reported. The present study measured the effect of sugammadex and 20% lipid emulsion on hemodynamics and survival in a rat model of verapamil toxicity.

MATERIAL/METHODS

In this single-blinded randomized control study, rats were separated into 4 groups of 7 rats each: Sugammadex (S), Sugammadex plus 20% lipid emulsion (SL), 20% lipid emulsion (L), and control (C). Heart rates and mean arterial pressures were monitored and noted each minute until death.

RESULTS

Average time to death was 21.0±9.57 minutes for group C, 35.57±10.61 minutes for group S, 37.14±16.6 minutes for group L and 49.86±27.56 minutes for group SL. Time to death was significantly longer in other groups than in the control group (p<0.05).

CONCLUSIONS

Verapamil overdose is has a comparatively high mortality rate and there is no effective antidote. Treatment generally involves gastric decontamination and symptomatic treatment to counteract the drug's negative effects. In animal studies sugammadex and lipid emulsion had a positive effect on survival in patients with calcium channel blocker toxicity. Sugammadex and intralipid increased survival in a rat model of verapamil toxicity. The combination of both drugs may decrease cardiotoxicity. Sugammadex alone or combined with 20% lipid emulsion reduce the need for inotropic agents. The mechanism requires clarification with larger studies.

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

An in vitro analysis of the effects of intravenous lipid emulsion on free and total local anaesthetic concentrations in human blood and plasma

Background. Intravenous lipid emulsion (ILE) is recommended as a “rescue” treatment for local anaesthetic (LA) toxicity. A purported mechanism of action suggests that lipophilic LAs are sequestered into an intravascular “lipid-sink,” thus reducing free drug concentration. There is limited data available correlating the effects of ILE on LAs. Aims. To compare the in vitro effect of ILE on LA concentrations in human blood/plasma and to correlate this reduction to LA lipophilicity. Method. One of four LAs (bupivacaine-most lipophilic-4 mg/L, ropivacaine-6 mg/L, lignocaine-14 mg/L, and prilocaine-least lipophilic-7 mg/L) was spiked into plasma or whole blood. ILE or control-buffer was added. Plasma was centrifuged to separate ILE and total-LA concentration assayed from the lipid-free fraction. Whole blood underwent equilibrium dialysis and free-LA concentration was measured. Percent reduction in LA concentration from control was compared between the LAs and correlated with lipophilicity. Results. ILE caused a significant reduction in total and free bupivacaine concentration compared with the other LAs. Ropivacaine had the least reduction in concentration, despite a lipophilicity similar to bupivacaine. The reduction in LA concentration correlated to increasing lipophilicity when ropivacaine was excluded from analysis. Conclusion. In this first in vitro model assessing both free- and total-LA concentrations exposed to ILE in human blood/plasma, ILE effect was linearly correlated with increasing lipophilicity for all but ropivacaine.