Intralipid® 20% for Reversal of Local Anesthetics

Study Overview
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Brief Summary
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In order to determine if Intralipid 20% can be used to reverse the effects of local anesthetics, the investigators will recruit 18 volunteers who will be asked to come to HSS for two study visits. Small amounts of local anesthetics will be injected into the volunteers' thighs during both visits. During one visit volunteers will receive Intralipid 20% and during the other visit they will receive a saline solution. The study team will measure how quickly normal sensation returns to the thighs when the volunteers get Intralipid 20% compared to saline.

Detailed Description
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The purpose of this study is to determine if a fat solution (Intralipid 20%) given intravenously can reverse the effects of local anesthetics. Local anesthetics are drugs that cause numbness when they are injected into different parts of the body. Local anesthetics are important drugs because they allow doctors to perform surgeries and other procedures on patients; however, there are certain instances where it would be helpful to reverse the effects of local anesthetics and reduce the amount of time that they produce numbness. In order to determine if Intralipid 20% can be used to reverse the effects of local anesthetics, the investigators will recruit 18 volunteers who will be asked to come to HSS for two study visits. Small amounts of local anesthetics will be injected into the volunteers' thighs during both visits. During one visit volunteers will receive Intralipid 20% and during the other visit they will receive a saline solution. The study team will measure how quickly normal sensation returns to the thighs when the volunteers get Intralipid 20% compared to saline.

Official Title
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The Use of Intralipid® 20% Solution to Reverse the Anesthetic Effect of Local Anesthetics: a Proof of Concept Study in Volunteers

Conditions
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Anesthesia, Local

Intervention / Treatment
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* Drug: Lidocaine 2%
* Drug: Lidocaine 1%
* Drug: Bupivacaine 0.25%
* Drug: Bupivacaine 0.5%
* Drug: Intralipid, 20% Intravenous
* Other: Saline intravenously
* Other: Saline


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: English speaking BMI 18-25, with body weight between 50-100kg Exclusion Criteria: ASA III or higher Pregnant Women Allergy to study medications (lidocaine, bupivacaine, soybeans, eggs) Use of drugs affecting the sensorium (including opioids, benzodiazepines, antipsychotics, gabapentinoids)

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Intralipid 20% IV Bolus<br>This is 1 out of the 2 study visits. The patient will receive 6 injections (3 in each thigh). The 6 injections are: lidocaine 1% lidocaine 2% bupivacaine 0.5% bupivacaine 0.25% saline no injection Each test solution will be injected over 5 seconds through a 27G needle and tuberculin syringe at a 30 degree angle. The patient will also receive an intravenous bolus in the arm of Intralipid 20%. Participant will be blindfolded for these activities so they will not know what they received during the visit. | Drug: Lidocaine 2%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Recticare;Drug: Lidocaine 1%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Recticare;Drug: Bupivacaine 0.25%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Sensorcaine;Drug: Bupivacaine 0.5%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Sensorcaine;Drug: Intralipid, 20% Intravenous<br>* a 250ml bag administered intravenously<br>* Other names: i.v. fat emulsion;Other: Saline<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: salt;|
| Placebo Comparator: Saline<br>This is 2 out of the 2 study visits. The patient will receive 6 injections (3 in each thigh). The 6 injections are: lidocaine 1% lidocaine 2% bupivacaine 0.5% bupivacaine 0.25% saline no injection Each test solution will be injected over 5 seconds through a 27G needle and tuberculin syringe at a 30 degree angle. The patient will also receive an intravenous bolus in the arm of Saline. Participant will be blindfolded for these activities so they will not know what they received during the visit. | Drug: Lidocaine 2%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Recticare;Drug: Lidocaine 1%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Recticare;Drug: Bupivacaine 0.25%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Sensorcaine;Drug: Bupivacaine 0.5%<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: Sensorcaine;Other: Saline intravenously<br>* a 250ml bag administered intravenously<br>* Other names: salt;Other: Saline<br>* 3 mL of test solution to a skin area on the thigh, 2cm in diameter<br>* Other names: salt;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time to complete normal sensation after lidocaine 1% | The time (measured in minutes) when the participant reports normal sensation of both cold swab and pinprick at the injection site of lidocaine 1%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to complete normal sensation after lidocaine 2% | The time (measured in minutes) when the participant reports normal sensation of both cold swab and pinprick at the injection site of lidocaine 2%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to complete normal sensation after Bupivacaine 0.5% | The time (measured in minutes) when the participant reports normal sensation of both cold swab and pinprick at the injection site of Bupivacaine 0.5%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to complete normal sensation after Bupivacaine 0.25% | The time (measured in minutes) when the participant reports normal sensation of both cold swab and pinprick at the injection site of Bupivacaine 0.25%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time to normal cold swab sensation after lidocaine 1% | The time (measured in minutes) when the participant reports normal sensation of cold swab at the injection site of lidocaine 1%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal pinprick sensation after lidocaine 1% | The time (measured in minutes) when the participant reports normal sensation of pinprick at the injection site of lidocaine 1%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal cold swab sensation after lidocaine 2% | The time (measured in minutes) when the participant reports normal sensation of cold swab at the injection site of lidocaine 2%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal pin prick sensation after lidocaine 2% | The time (measured in minutes) when the participant reports normal sensation of pinprick at the injection site of lidocaine 2%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal pinprick sensation after Bupivacaine 0.5% | The time (measured in minutes) when the participant reports normal sensation of pinprick at the injection site of Bupivacaine 0.5%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal cold swab sensation after Bupivacaine 0.5% | The time (measured in minutes) when the participant reports normal sensation of cold swab at the injection site of Bupivacaine 0.5%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal cold swab sensation after Bupivacaine 0.25% | The time (measured in minutes) when the participant reports normal sensation of cold swab at the injection site of Bupivacaine 0.25%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours | 
| Time to normal pinprick sensation after Bupivacaine 0.25% | The time (measured in minutes) when the participant reports normal sensation of pinprick at the injection site of Bupivacaine 0.25%. Although measured for each individual participant, the average time across all participants is reported. | up to 24 hours |