Spinal Hypobaric Local Anesthetic Study

Pharmacodynamic Profile of Intrathecal Hypobaric Local Anesthetics. an Observational Study

The length of hospital stay after total hip and knee arthroplasty is determined based on the successful mobilization of the patients post surgery. Fast track pathways involving early mobilization and discharge of the patient on the same day of surgery, shortens the hospital stay and reduces the risk of adverse effects. The long acting LA (bupivacaine) is most commonly used in spinal anesthesia for arthroplasty surgeries and is associated with a prolonged motor and sensory block. In contrast, hypobaric bupivacaine and hypobaric mepivacaine helps in achieving the desired block level with smaller dosage and shorter onset time and faster recovery when compared to long acting local anesthetics. The aim of the study is to observe the effects of hypobaric local anesthetics ( bupivacaine and mepivacaine ) in patients undergoing unilateral total hip or knee arthroplasty in terms of time to onset and time to recovery of the block and also its effect on hemodynamic stability and time to mobilization after surgery. This study will allow the investigators to recommend optimal dosing strategies that in turn will help in faster recovery from spinal anesthesia and early mobilization thereby reducing harmful outcomes.

Study Overview

• Status: Completed
• Conditions: Anesthesia, Local
• Intervention / Treatment: Drug: Spinal hypobaric Bupivacaine Local Anesthetic Injection; Drug: Spinal hypobaric Mepivacaine Local Anesthetic Injection

Detailed Description

Fast-track pathways involving same day mobilization and hospital discharge for total hip and knee arthroplasty are increasingly popular in modern orthopedic practice. Numerous reports have demonstrated the feasibility of this approach.

The choice of local anesthetic (LA) drug and dose administered in spinal anesthesia is determined by several considerations including the desired block height (the upper limit of sensory loss and surgical anesthesia that is achieved) and block duration. Block height and duration should be adequate for the surgery in question, but should ideally not be excessive, as they can lead to adverse effects including sympathetic blockade and hypotension, urinary retention, and delayed recovery of motor function in the lower limbs. The long-acting amide LA, bupivacaine, is most commonly used in this setting at Toronto Western Hospital (TWH) and elsewhere in the world. It is, however, associated with a prolonged motor and sensory recovery (4-6 hours). An alternative strategy to achieve adequate block height without using excessive doses of LA is to administer a hypobaric solution of bupivacaine or mepivacaine; this has been trialed with success at TWH and is now used routinely by staff anesthesiologists. Nevertheless, most of the investigator's knowledge regarding hypobaric LA solutions in spinal anesthesia comes from studies that are more than two decades old. There are no studies on mepivacaine, and neither hypobaric bupivacaine nor mepivacaine have been investigated in the context of fast-track total hip and knee arthroplasty pathways. In this context, the ideal LA solution used for spinal anesthesia should provide a consistent and fast onset time to achieve the required surgical anesthesia while the sensory and motor block should resolve as soon as possible after surgery. The investigators believe that hypobaric bupivacaine and hypobaric mepivacaine may satisfy these criteria and hence, the investigators aim to study their pharmacodynamics.

• Study Type: Observational
• Enrollment (Actual): 60

Contacts and Locations

Study Locations

• Canada
  • Ontario
    • Toronto, Ontario, Canada, M5T 2S8
      • Toronto Western Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

All day surgery and in-patients who are scheduled to undergo elective unilateral total hip or knee arthroplasty under spinal anesthesia at Toronto Western Hospital

Description

Inclusion Criteria:

1. Patients undergoing elective unilateral total hip or knee arthroplasty under spinal anesthesia at Toronto Western Hospital
2. American Society of Anesthesiologists physical status class (ASA-PS) 1-3
3. Aged ≥ 20 years

Exclusion Criteria:

1. Refusal to participate
2. Inability to communicate due to language barrier or cognitive impairment
3. Height < 150 cm or > 200 cm
4. Weight < 40 kg or >130 kg
5. Contraindication or allergy to amide-type local anesthetic
6. Contraindication to spinal anesthesia (e.g., infection at the injection site, existing coagulopathy)
7. Spinal anesthesia performed in the operating room rather than the block room (which will preclude adequate testing)
8. Spinal anesthesia that includes administration of intrathecal opioids (e.g., morphine, fentanyl),so as to avoid unanticipated alterations in block quality or solution baricities.

9. Pre-existing sensory or motor impairment in the lower extremities

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Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Mepivacaine; Day surgery patients(30 patients); For these patients- Administration of a spinal hypobaric mepivacaine injection	Drug: Spinal hypobaric Mepivacaine Local Anesthetic Injection; • Administration of a hypobaric spinal mixture for Day-Surgery patients: 3.4ml of 1.5% mepivacaine created by 3ml 2% mepivacaine with 1ml sterile water, and then discarding 0.6ml; Other Names: Carbocaine
Bupivacaine; In-patients(30 patients): For these patients- Administration of a spinal hypobaric bupivacaine injection	Drug: Spinal hypobaric Bupivacaine Local Anesthetic Injection; Administration of a hypobaric spinal mixture for In-patients: 3ml of 0.33% bupivacaine created by 2ml 0.5% bupivacaine with 1ml sterile water; Other Names: Marcaine

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
1. Time to reach the most cephalad/cranial sensory block level (onset time of spinal anesthesia on the surgical side).	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Time to reach sensory block level of L1 or higher (adequate level of anesthesia for knee surgery) on the surgical side	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Time to reach sensory block level T10 or higher (adequate level of anesthesia for hip surgery) on the surgical side	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Time to achieve complete motor block on the modified Bromage scale	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
The most cephalad/cranial sensory block level	Sensory block will be assessed every 5 mins during the first 30 mins after spinal injection. A pinprick test using an 18G (Gauge) blunt-tipped needle (BD Blunt Fill needle) will be performed on non-dependent and dependent sides to detect sensory loss over the torso and lower limbs.	Assessed over the duration of time period till the patient is discharged.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time to regression of the sensory block to the L2 dermatome on both lower limbs.	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Time to full motor recovery on the modified Bromage scale	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Hemodynamic stability after the spinal injection	Will be assessed by the measurement of vitals	Assessed over the duration of time period till the patient is discharged.
Time to ambulation	Time to onset is a continuous variable and therefore will be expressed as mean ± standard deviation.	Assessed over the duration of time period till the patient is discharged.
Patient satisfaction score	Assessed by a five-point Likert scale provided to the patient	Assessed before the patient is discharged.
Surgeon's perception of quality of anesthesia	Assessed by a three-point Likert scale provided to the surgeon	Assessed after the end of surgery.
Rate of successful spinal anesthesia	Will be determined as successful when there will be no need to convert to general anesthesia or administer supplemental opioids or local infiltration in the operating room.	Assessed after the spinal block till the end of surgery

Collaborators and Investigators

• Sponsor: University Health Network, Toronto
• Investigators: Principal Investigator: Ki Jinn Chin, MD,FRCPC, UHN

Study record dates

Study Major Dates

• Study Start (Actual): June 9, 2023
• Primary Completion (Actual): October 17, 2023
• Study Completion (Actual): May 24, 2024

Study Registration Dates

• First Submitted: December 4, 2023
• First Submitted That Met QC Criteria: December 4, 2023
• First Posted (Actual): December 12, 2023

Study Record Updates

• Last Update Posted (Actual): March 28, 2025
• Last Update Submitted That Met QC Criteria: March 24, 2025
• Last Verified: March 1, 2025

More Information

Terms related to this study

• Keywords: Bupivacaine; Mepivacaine; Spinal Hypobaric LA
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Peripheral Nervous System Agents; Central Nervous System Depressants; Sensory System Agents; Bupivacaine; Anesthetics; Anesthetics, Local; Mepivacaine
• Other Study ID Numbers: 22-5558; v04Nov2022 (Other Identifier: UHN)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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