Low-Dose Hypobaric Anesthesia Shows Promise in Arthroplasty

TOPLINE:

Low-dose hypobaric mepivacaine and bupivacaine provide adequate spinal anesthesia for hip and knee arthroplasty, with 93% of patients completing surgery without supplementation. Motor function returned by a mean of 145 minutes with mepivacaine and 217 minutes with bupivacaine.

METHODOLOGY:

• Researchers conducted a prospective observational study to investigate the anesthetic and recovery profiles of low-dose hypobaric mepivacaine and bupivacaine for spinal anesthesia in patients undergoing total hip and knee arthroplasty.
• They enrolled patients aged 20 years or older with American Society of Anesthesiologists Physical Status I-III who were scheduled for elective unilateral total hip or knee arthroplasty.
• Participants scheduled for same-day discharge received 51 mg of hypobaric 1.5% mepivacaine (n = 30); those scheduled for inpatient stay received 10 mg of hypobaric 0.33% bupivacaine (n = 30).
• Sensory blockade was assessed using pinprick testing, and motor function was evaluated through active flexion and extension at the hip, knee, and ankle. Testing was performed every 5 minutes for up to 30 minutes after spinal anesthesia or until transfer to the operating room, whichever occurred first.
• Preoperative outcomes included time to achieve sensory blockade at T10 or higher and L1 or higher, and postoperative outcomes included duration of sensory blockade and time to recovery of normal sensation and motor function.

TAKEAWAY:

• The mean time to achieve sensory blockade at or above L1 and T10 in the operative limb was 5.7 and 7.3 minutes, respectively, with mepivacaine, and 6.2 and 8.1 minutes, respectively, with bupivacaine.
• The mean duration of the sensory blockade at or above T10 and L1 in the operative limb was 97 and 115 minutes, respectively, with mepivacaine and 127 and 161 minutes, respectively, with bupivacaine.
• Motor function returned by 145 and 217 minutes in the mepivacaine and bupivacaine groups, respectively.
• The success rate for anesthesia reached 93% in both groups, with four patients requiring supplemental anesthesia for surgical completion; the median satisfaction score for anesthetic care was 5 out of 5 in both groups, and no patients reported transient neurologic symptoms at follow-up.

IN PRACTICE:

“Practitioners should view our data on duration of surgical anesthesia and sensory and motor block as a reference from which to extrapolate LA [local anesthetic] dose adjustments based on their desired anesthetic goals. Where duration of surgical anesthesia above T10 exceeding two hours is desired, higher doses of mepivacaine (60-80 mg) or bupivacaine (12-15 mg) should be used,” the authors of the study wrote.

SOURCE:

The study was led by Joanne M.H. Tan, MD, of the Department of Anaesthesia, Pain and Hyperbaric Medicine at Royal Adelaide Hospital, in Adelaide, Australia, and was published online on December 10, 2024, in the Canadian Journal of Anesthesia.

LIMITATIONS:

Data regarding the duration of the sensory block at the T10 and L1 levels were missing for a significant proportion of patients, which could have led to an overestimation of the duration of the sensory block. The study did not formally measure the specific gravity of the LA solutions used in the study.

DISCLOSURES:

No funding source was disclosed. The authors reported no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.