Clinical trial NCT06526156: Hypobaric L5-S1 Study
Official title: The Anesthetic and Recovery Profiles of Low-dose Hypobaric Bupivacaine in Spinal Anesthesia Injected in the L5-S1 Space for Total Hip and Knee Arthroplasty
Study type: OBSERVATIONAL
Overall status: RECRUITING
Conditions: Anesthesia
Anesthesia, Local
Keywords: Total Hip Arthroplasty
Total Knee Arthroplasty
Bupivacaine
Lead sponsor: University Health Network, Toronto
Sponsor class: OTHER
First posted: 2024-07-29
Enrollment: 55
Sex: ALL
Minimum age (years): 20
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: COHORT
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: Adults aged at least 20 years having inpatient elective unilateral total hip or knee arthroplasty surgery

Brief summary: Patients going through total hip or knee replacement (arthroplasty) have to be put under spinal anesthesia to prevent them from feeling any pain during surgery. Spinal anesthesia means having a small needle inserted between the bones of the lower lumbar spine (vertebrae). The choice of space used is decided by the anesthesiologist in charge of patient care. The space between these bones is often narrowed by arthritis or other age-related degenerative spine disease in patients having total hip or knee replacement surgery. The lowest L5-S1 (Lumbar 5- Sacral 1) space is the largest one and often least affected by arthritis, which makes it the easiest option. Despite this, it is not currently the most common space used for spinal anesthesia, because it is hard to find by palpation (feeling the bones through the skin), and because there is concern that local anesthetic will not always spread up high enough from this lowest space, which is needed for a successful spinal anesthesia. How far it spreads depends on the amount (dose) and density of local anesthetic given.

There are two types of local anesthetic: one called isobaric, which has the same density as CSF (Cerebro-Spinal Fluid), and another called hypobaric, which has lower density than CSF.

Isobaric local anesthetic spreads evenly throughout the CSF irrespective of patient positioning. However, a larger dose is required to achieve adequate anesthesia for surgery. Using larger doses, leads to a very long duration of sensory and motor block, far in excess of that required for surgical completion which leads to a slower recovery from anesthesia.

Hypobaric local anesthetic, on the other hand, floats in CSF like oil on water. This allows anesthesiologists to use a smaller dose while still being sure that it will spread high enough to achieve adequate anesthesia for surgery. The smaller doses in turn allow for faster recovery of normal movement and feeling in the legs of patients after surgery.

It has been observed that all of these dilemma can be solved by:

1. Using ultrasound imaging to find and mark the space, and
2. Injecting hypobaric local anesthetic.

The goal of this observational study is to determine the success rate of spinal anesthesia with a lower dose of hypobaric bupivacaine injected into the L5-S1 space, when done on total hip or knee arthroplasty patients at Toronto Western Hospital.

Detailed description: Spinal anesthesia is the recommended type of anesthesia for total hip or knee arthroplasty, as it is associated with superior clinical outcomes compared to general anesthesia. However, many patients undergoing these surgical procedures have age-related spine disease, previous spine surgery, or other spinal deformities which make the injection of spinal anesthesia difficult.

One strategy is to administer the spinal anesthesia at the L5-S1 space: it is least affected by arthritic and degenerative changes, and as it is the largest intervertebral space, it has the lowest chance of causing spinal cord trauma.

However, administration of spinal anesthesia at the lowest lumbar intervertebral levels significantly decreases the odds of success of surgical anesthesia. This is due to the fact that the standard solution of 0.5% bupivacaine is isobaric with respect to the cerebrospinal fluid (CSF), leading to unpredictable distribution within the CSF and inconsistent extent of sensory block. It has been shown that an inordinately large dose of 25 mg (5 milliliter) of 0.5% bupivacaine is required to achieve the adequate extent of sensory loss, as opposed to more conventional doses of 12-15 mg (milligram). However, this leads to a very long duration of sensory and motor block, far in excess of that required for surgical completion. This delays patient discharge from the post-anesthetic recovery unit, mobilization, and recovery. This is at odds with the goals of modern total hip and knee arthroplasty, which emphasizes same-day mobilization, physiotherapy, and even same-day hospital discharge. Using lower doses of isobaric bupivacaine, on the other hand, increases the risk of inadequate or failed spinal anesthesia, requiring conversion to general anesthesia.

One strategy to address this dilemma, which has been employed with great success to date at the Toronto Western Hospital (TWH), is to use a solution of bupivacaine that is hypobaric relative to CSF. This promotes cranial distribution of bupivacaine within the CSF and blockade of the higher spinal nerve roots, thus ensuring adequate extent of sensory block, even when administering doses as low as 10 mg of bupivacaine. This hypobaric bupivacaine solution is prepared by mixing 2 mL(milliliter) of isobaric 0.5% bupivacaine with 1 mL of sterile water. The investigators have demonstrated the efficacy of this for successful surgical anesthesia of adequate, but not excessive, duration in a recently concluded observational study. Notably, two subjects in the cohort of 60 patients received spinal anesthesia at the L5-S1 level. Both patients had adequate sensory block height and duration for commencement and completion of surgery without need for anesthetic supplementation. The investigator(s) have performed spinal anesthesia at the L5-S1 level in many other patients over the last 3 years with the same dose of hypobaric bupivacaine and have not encountered failure to date.

The purpose of this observational study is to determine the success rate of spinal anesthesia with low-dose (10 mg) hypobaric bupivacaine injected into the L5-S1 space in patients undergoing total hip or knee arthroplasty surgery.

Eligibility criteria: Inclusion Criteria:

* Patients undergoing elective unilateral total hip or knee arthroplasty under spinal anesthesia at TWH who are scheduled for inpatient overnight admission
* American Society of Anesthesiologists physical status class (ASA-PS) 1-3
* At least 20 years of age

Exclusion Criteria:

* Refusal to participate
* Inability to communicate due to language barrier or cognitive impairment
* Height \> 200 cm
* Weight \>120 kg
* Body mass index (BMI) \>45 kg/m\^2
* Contraindication or allergy to amide-type local anesthetic
* Contraindication to spinal anesthesia at the L5-S1 space (e.g., infection at the injection site, existing coagulopathy, severe spinal stenosis at higher vertebral levels)
* Previous spinal surgery in the lumbosacral spine
* Spinal anesthesia performed in the operating room rather than the block room
* Spinal anesthesia that includes administration of intrathecal opioids (e.g., morphine, fentanyl)
* Pre-existing sensory or motor impairment in the lower extremities
* Inability to identify the L5-S1 space with ultrasonography

Primary outcomes:
measure: Rate of successful spinal anesthesia
timeFrame: Assessed from time of spinal injection to surgery completion
measure: Most cranial dermatomal level of sensory anesthesia achieved before surgery
timeFrame: Assessed every 5 minutes for the first 30 minutes after spinal injection
measure: Time to reach the most cranial dermatomal level of sensory anesthesia before surgery
timeFrame: Assessed from time of spinal injection to surgery commencement
measure: Time to reach sensory anesthesia at level of T10 or higher before surgery, on the operative limb
timeFrame: Assessed from time of spinal injection to surgery commencement
measure: Time to reach sensory anesthesia at level of L1 or higher before surgery, on the operative limb
timeFrame: Assessed from time of spinal injection to surgery commencement
measure: Time to recovery of normal sensation at T10 or lower (also defined as duration of sensory analgesia at T10 or higher) in both lower limbs
timeFrame: Assessed at the end of surgery and every 30 minutes in the post-anesthesia care unit (PACU) or inpatient ward until a return of normal sensation in the T10 dermatome has been documented
measure: Time to normal sensation at L1 or lower (also defined as duration of sensory analgesia at L1 or higher) in both lower limbs
timeFrame: Assessed at the end of surgery and every 30 minutes in the PACU or inpatient ward until a return of normal sensation in the L2 dermatome has been documented on the day of surgery.
measure: Time to recovery of normal sensation at L2 or lower in both lower limbs
timeFrame: Assessed at the end of surgery and every 30 minutes in the PACU or inpatient ward until a return of normal sensation in the L2 dermatome has been documented on the day of surgery.
measure: Time to achieve complete motor block at hip, knee, ankle, and toes
timeFrame: Assessed every 5 minutes for the first 30 minutes after spinal injection
measure: Time to regain ability to move hip, knee, ankle, and toes; and a score of 0 on the modified Bromage scale
timeFrame: Assessed at the end of surgery and every 30 minutes in the PACU or inpatient ward until full motor recovery has been achieved in both lower limbs on the day of surgery.
Secondary outcomes:
measure: Time to scan, locate and mark the L5-S1 space
timeFrame: Assessed before surgery
measure: Time to perform the spinal anesthetic
timeFrame: Assessed before surgery
measure: Number of needle passes
timeFrame: Assessed before surgery
measure: Incidence of adverse effects after spinal anesthesia
timeFrame: Assessed after the end of surgery and during the patient's stay in PACU or in-patient ward on the day of surgery.
measure: Patient satisfaction with anesthesia care, based on Likert scale
timeFrame: Assessed at the last study assessment visit, when regression to L2 has been documented either in PACU or in-patient ward on the day of surgery.
measure: Patient satisfaction with anesthesia care, based on 3-response question
timeFrame: Assessed at the last study assessment visit, when regression to L2 has been documented either in PACU or in-patient ward on the day of surgery.
measure: Surgeon's perception of quality of intraoperative anesthesia
timeFrame: Assessed at the end of surgery and before the patient is transferred to PACU on the day of surgery.
Other outcomes:
Locations:
city: Toronto
country: Canada
facility: Toronto Western Hospital
state: Ontario
Study officials:
affiliation: UHN
name: Ki Jinn Chin, MBBS,MMed,FRCPC
role: PRINCIPAL_INVESTIGATOR
References: