Clinical Characteristics of Prilocaine for Spinal Anesthesia in Ambulatory Surgery: Clinical Profile and Efficacy

Introduction

The increasing number of surgical conditions managed in the outpatient setting has become a reality in contemporary clinical practice. Knee arthroscopy for meniscal pathology is a common orthopedic procedure of short duration that requires early postoperative discharge. In this ambulatory setting, spinal anesthesia plays an important role by providing adequate surgical anesthesia while maintaining a limited duration of action, thereby reducing recovery room stay and facilitating safe and efficient patient discharge.

Prilocaine is a local anesthetic widely used worldwide in ambulatory surgery, particularly for orthopedic and perineal procedures. It offers several advantages over other intermediate-acting local anesthetics, such as bupivacaine, and is associated with a lower incidence of transient neurologic symptoms compared with lidocaine.

Until recently, hyperbaric prilocaine had not been available in our country for intrathecal administration. Its use has now been approved by the Chilean Public Health Institute (ISP) (approval attached). Hyperbaric prilocaine has a favorable profile for ambulatory patients, including a shorter onset time, faster motor recovery, and a shorter time to first voiding.

Objective

The aim of this project is to describe the local use of intrathecal prilocaine, including the clinical characteristics of sensory and motor block, the incidence of anesthesia-related complications, and potential readmissions following outpatient knee arthroscopy.

Hypothesis: The use of prilocaine in short-duration outpatient knee arthroscopy facilitates early discharge from the recovery unit, allows rapid postoperative ambulation following spinal anesthesia, and is associated with a low incidence of complications such as urinary retention, postoperative nausea and vomiting, and hypotension, as reported in studies from other countries.

Research Question: What is the clinical performance of prilocaine in short-duration outpatient knee arthroscopy and what are the associated patient outcomes?

Materials and Methods

Following approval by the Institutional Ethics Committee of the Faculty of Medicine, Pontificia Universidad Católica de Chile (Santiago, Chile), and after obtaining written informed consent, a prospective study will be conducted in 50 ASA physical status I-II patients scheduled for outpatient knee arthroscopy. This sample represents a convenience cohort selected for descriptive purposes.

In the operating room, a peripheral intravenous catheter (18-20 G) will be inserted for the administration of fluids and medications. Spinal anesthesia will be performed using 40 mg of 2% prilocaine under standard monitoring, including continuous electrocardiography, noninvasive blood pressure monitoring, and pulse oximetry. Supplemental oxygen will be administered via Campbell mask, and sedation will be provided with 1-2 mg of midazolam.

The type and duration of surgery will be recorded. Anesthetic outcomes will include the duration of sensory and motor block, time to ambulation, time to first voiding, and time to discharge. In addition, complications occurring during the recovery period, including urinary retention, postoperative nausea and vomiting, and hypotension, will be documented.

No formal sample size calculation was performed, as the study will include a convenience sample of 50 patients.

A descriptive analysis will be conducted, with continuous variables reported as means and standard deviations. No inferential statistical tests will be performed.