Intralipid® 20% for Reversal of Local Anesthetics

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

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.

Study Overview

• Status: Active, not recruiting
• Conditions: Anesthesia, Local
• Intervention / Treatment: Drug: Lidocaine 2%; Drug: Lidocaine 1%; Drug: Bupivacaine 0.25%; Drug: Bupivacaine 0.5%; Drug: Intralipid, 20% Intravenous; Other: Saline; Other: Saline intravenously

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 18
• Phase: Phase 4

Contacts and Locations

Study Locations

• United States
  • New York
    • New York, New York, United States, 10021
      • Hospital of Special Surgery

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

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)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Intralipid 20% IV Bolus; 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%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Lidoderm; Lidocaine Viscous; Recticare; Drug: Lidocaine 1%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Lidoderm; Lidocaine Viscous; Recticare; Drug: Bupivacaine 0.25%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Marcaine; Sensorcaine; Drug: Bupivacaine 0.5%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Marcaine; Sensorcaine; Drug: Intralipid, 20% Intravenous; a 250ml bag administered intravenously; Other Names: i.v. fat emulsion; Other: Saline; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: salt
Placebo Comparator: Saline; 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%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Lidoderm; Lidocaine Viscous; Recticare; Drug: Lidocaine 1%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Lidoderm; Lidocaine Viscous; Recticare; Drug: Bupivacaine 0.25%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Marcaine; Sensorcaine; Drug: Bupivacaine 0.5%; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: Marcaine; Sensorcaine; Other: Saline; 3 mL of test solution to a skin area on the thigh, 2cm in diameter; Other Names: salt; Other: Saline intravenously; a 250ml bag administered intravenously; Other Names: salt

What is the study measuring?

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

Collaborators and Investigators

• Sponsor: Hospital for Special Surgery, New York
• Investigators: Principal Investigator: Stavros Memtsoudis, MD/PhD, Hospital for Special Surgery, New York

Study record dates

Study Major Dates

• Study Start (Actual): July 26, 2019
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): October 1, 2026

Study Registration Dates

• First Submitted: May 21, 2019
• First Submitted That Met QC Criteria: May 28, 2019
• First Posted (Actual): May 30, 2019

Study Record Updates

• Last Update Posted (Actual): December 8, 2025
• Last Update Submitted That Met QC Criteria: December 2, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Organic Chemicals; Anilides; Amides; Aniline Compounds; Amines; Acetanilides; Inorganic Chemicals; Chlorine Compounds; Sodium Compounds; Chlorides; Hydrochloric Acid; Bupivacaine; Lidocaine; Sodium Chloride; Salts; soybean oil, phospholipid emulsion; Lidoderm
• Other Study ID Numbers: 2018-2039

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures)
• IPD Sharing Time Frame: Beginning 9 months and ending 36 months following article publication
• IPD Sharing Access Criteria: Investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose. For individual participant meta-analysis. Proposals may be submitted up to 36 months following article publication. After 36 months the data will be available in our data warehouse but without investigator support other than deposited metadata.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No