Population Pharmacokinetics of Levobupivacaine During Transversus Abdominis Plane Block in Children.

BACKGROUND: Levobupivacaine is commonly used during transversus abdominis plane (TAP) block in pediatric patients. However, the dosing regimen is still empirical, and the pharmacokinetic properties of levobupivacaine are not considered. Here, the pharmacokinetics of levobupivacaine during an ultrasound-guided TAP block were evaluated to optimize dosing regimen, regarding the between-subject variability (BSV) and the volume of levobupivacaine injected. METHOD: The clinical trial (prospective, randomized, double-blind study protocol) was conducted in 40 children aged 1-5 years, who were scheduled for inguinal surgery. Each patient received 0.4 mg/kg of levobupivacaine with a volume of local anesthesia solution adjusted to 0.2 mL/kg of 0.2% or 0.4 mL/kg of 0.1% levobupivacaine. Blood samples were collected at 5, 15, 20, 25, 30, 45, 60, and 75 minutes after the block injection. The population pharmacokinetic analysis was performed using the NONMEM software. RESULTS: From the pharmacokinetic parameters obtained, median Cmax, tmax,, and area under the concentration versus time curve were 0.315 mg/L, 17 minutes, and 41 mg/L·min, respectively. BSV of clearance was explained by weight. At the dose regimen of 0.4 mg/kg, none of the infants showed signs of toxicity, but in 13 patients, TAP block failed. After analysis, BSV for absorption rate constant, distribution volume, and clearance were 81%, 47%, and 41%, respectively. Residual unexplained variability was estimated to be 14%. CONCLUSIONS: For improved efficiency in the pediatric population, the dose of levobupivacaine should be greater than 0.4 mg/kg. Children's weight should be considered to anticipate any risk of toxicity.

Quadratus lumborum block versus transversus abdominis plane block for postoperative pain management after laparoscopic colorectal surgery: A randomized controlled trial.

BACKGROUND: This study aimed to compare the quadratus lumborum block (QLB) method with transversus abdominis plane block (TAPB) for postoperative pain management in patients undergoing laparoscopic colorectal surgery. METHODS: Seventy-four patients scheduled for laparoscopic colorectal surgery were randomly assigned into 2 groups. After surgery, patients received bilateral ultrasound-guided single-dose of QLB or TAPB. Each side was administered with 20 ml of 0.375% ropivacaine. All patients received sufentanil as patient-controlled intravenous analgesia (PCIA). Resting and moving numeric rating scale (NRS) were assessed at 2, 4, 6, 24, 48 hours postoperatively. The primary outcome measure was sufentanil consumption at predetermined time intervals after surgery. RESULTS: Patients in the QLB group used significantly less sufentanil than TAPB group at 24 and 48 hours (P < .05), but not at 6 hours (P = .33) after laparoscopic colorectal surgery. No significant differences in NRS results were found between the two groups at rest or during movement (P > .05). Incidence of dizziness in the QLB group was lower than in TAPB group (P < .05). CONCLUSIONS: The QLB is a more effective postoperative analgesia as it reduces sufentanil consumption compared to TAPB in patients undergoing laparoscopic colorectal surgery.

The Subcostal Nerve During Lateral Approaches to the Lumbar Spine: An Anatomical Study with Relevance for Injury Avoidance and Postoperative Complications Such as Abdominal Wall Hernia.

BACKGROUND: Lateral approaches to the spine are increasing in popularity. However, details of the innervation pattern of the abdominal oblique muscles with the initial dissection have not been well studied. METHODS: Ten adult fresh-frozen cadavers (20 sides) were placed in the lateral position. On each side, the region in which transpsoas approaches are performed, between the iliac crest and the 12th rib, was dissected. The nerves, their course, and their muscular supply were studied. RESULTS: The subcostal nerve is the predominant nerve supply for the anterolateral abdominal muscle innervation. It is larger and has a wider field of distribution and more branches (8 on average) compared with the L1 (4 on average) and 11th intercostal nerves (2 on average 2). The proximal 6-10 cm of each nerve has few if any branches. The subcostal nerve is often (75%) located up to 5 cm inferior to the 12th rib in its initial course. The area of least concentration ("safe zone") is located at an approximate midpoint between the lower edge of the 12th rib and the superior-most aspect of the iliac crest. A previously undescribed branch of the subcostal nerve was found traveling posterior to the quadratus lumborum and joining the remaining subcostal nerve in an anastomosis at or near the lateral position. CONCLUSIONS: Knowledge of the innervation and nerve dominance patterns might help decrease postoperative complications such as sensory deficits or abdominal wall hernias. The subcostal nerve is the dominant nerve in both size and innervation of the oblique muscles in the lateral position, transpsoas approach.