Hypobaric L5-S1 Study
NCT Number: NCT06526156
Status: RECRUITING
Study Type: OBSERVATIONAL
Conditions: Anesthesia|Anesthesia, Local
Interventions: DRUG: Bupivacaine injection
Sponsor: University Health Network, Toronto
Sex: ALL
Age: ADULT, OLDER_ADULT
Enrollment: 55
Study Design: Observational Model: |Time Perspective: p
Start Date: 2024-07-22
Completion Date: 2025-06-30
Locations: Toronto Western Hospital, Toronto, Ontario, M5T 2S8, Canada

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.

Primary Outcome Measures: Rate of successful spinal anesthesia, "Successful spinal anesthesia" is defined as the completion of surgery without conversion to general anesthesia, administration of supplemental opioids or surgical local anesthetic infiltration in the operating room to manage surgical pain., Assessed from time of spinal injection to surgery completion|Most cranial dermatomal level of sensory anesthesia achieved before surgery, 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. Sensation to pinprick testing in each dermatome will be categorized as normal ("sharp" sensation), analgesia ("dull" sensation), or anesthesia ("no" sensation).

The most cephalad/cranial (upper) sensory block level of analgesia and anesthesia will be recorded based on the dermatomal map., Assessed every 5 minutes for the first 30 minutes after spinal injection|Time to reach the most cranial dermatomal level of sensory anesthesia before surgery, The most cranial dermatomal level of sensory anesthesia will be determined based on the pinprick test., Assessed from time of spinal injection to surgery commencement|Time to reach sensory anesthesia at level of T10 or higher before surgery, on the operative limb, The dermatomal level of sensory anesthesia will be determined based on the pinprick test., Assessed from time of spinal injection to surgery commencement|Time to reach sensory anesthesia at level of L1 or higher before surgery, on the operative limb, The dermatomal level of sensory anesthesia will be determined based on the pinprick test., Assessed from time of spinal injection to surgery commencement|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, The dermatomal level of sensory anesthesia will be determined based on the pinprick test., 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|Time to normal sensation at L1 or lower (also defined as duration of sensory analgesia at L1 or higher) in both lower limbs, The dermatomal level of sensory anesthesia will be determined based on the pinprick test., 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.|Time to recovery of normal sensation at L2 or lower in both lower limbs, The dermatomal level of sensory anesthesia will be determined based on the pinprick test., 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.|Time to achieve complete motor block at hip, knee, ankle, and toes, The development of motor block will be assessed by assessing the ability to actively flex and extend at the hip, ankle, knee, and toes. This will be scored as either 1 (movement present and observed) or 0 (movement absent) at each joint on both lower extremities., Assessed every 5 minutes for the first 30 minutes after spinal injection|Time to regain ability to move hip, knee, ankle, and toes; and a score of 0 on the modified Bromage scale, Modified Bromage scale scores:

0 - Able to move hip, knee, ankle and toes

1. - Unable to move hip, able to move knee, ankle and toes
2. - Unable to move hip and knee, able to move ankle and toes
3. - Unable to move hip, knee and ankle, able to move toes
4. - Unable to move hip, knee, ankle, or toes, 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 Outcome Measures: Time to scan, locate and mark the L5-S1 space, Time between first skin-probe contact to completion of skin markings., Assessed before surgery|Time to perform the spinal anesthetic, Time between injection of skin local anesthetic to completion of spinal anesthetic injection., Assessed before surgery|Number of needle passes, Each needle pass is defined as an insertion followed by a withdrawal of the spinal needle., Assessed before surgery|Incidence of adverse effects after spinal anesthesia, The following side-effects and adverse effects of spinal anesthesia will be assessed and recorded:

i) Incidence of hypotension following spinal anesthesia and prior to intraoperative sedation

ii) Incidence of postoperative nausea and vomiting (PONV) in the PACU, defined as need for administration of anti-emetic medication during the patient's stay in the PACU on the day of surgery.

iii) Urinary retention (defined as need for urinary catheterization after surgery in PACU or in-patient ward on the day of surgery., Assessed after the end of surgery and during the patient's stay in PACU or in-patient ward on the day of surgery.|Patient satisfaction with anesthesia care, based on Likert scale, Assessed using a 5-point Likert scale.

1. Very dissatisfied
2. Somewhat dissatisfied
3. Neutral - neither satisfied nor dissatisfied
4. Somewhat satisfied
5. Very satisfied

In the event of a score of 1-2 on the Likert scale, the patient will be asked to clarify the reasons for dissatisfaction with the anesthetic and how they think this could be improved with the following questions:

i) "What did you not like about the anesthetic experience?" ii) "How could this be improved in the future?", 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.|Patient satisfaction with anesthesia care, based on 3-response question, Assessed using a 3-response question: "Would you choose to have the same anesthetic for similar surgery in the future?"

Responses: Yes / Unsure / No

In the event of a "No" response, the patient will be asked to clarify the reasons for dissatisfaction with the anesthetic and how they think this could be improved with the following questions:

i) "What did you not like about the anesthetic experience?" ii) "How could this be improved in the future?", 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.|Surgeon's perception of quality of intraoperative anesthesia, Surgeon's perception of the quality of anesthesia, in terms of the operating conditions provided by the spinal anesthetic. Assessed using a 3-point Likert scale:

1. Poor (lowest score, worst outcome)
2. Acceptable
3. Good (highest score, best outcome), Assessed at the end of surgery and before the patient is transferred to PACU on the day of surgery.