A Comparative Study Between Age-Based and Weight-Based Bupivacaine Dosing for Pediatric Spinal Anesthesia in Children Undergoing Elective Infra-Umbilical Surgeries

This prospective randomized double-blinded controlled trial will be conducted on 60 pediatric patients who will undergo elective infra-umbilical surgeries, e.g., inguinal hernia repair, orchiopexy, etc. admitted to the operating theatres of Abu El Reesh Children's Hospital, Cairo University.

Randomization and blinding An online randomization program (http://www.randomizer.org) will be used to generate a random list, and each patient's code will be kept in an opaque sealed envelope. Patients will be randomly allocated in a 1:1 allocation ratio into two equal groups in a parallel manner:

• Group A (n=30): Children will receive spinal anesthesia according to weight-based dosing calculation of bupivacaine
• Group B (n=30): Children will receive spinal anesthesia according to age-based dosing calculation of bupivacaine. The patient and/or related guardian will be blinded to group assignment as well as the anesthesiologist involved in data collection and analysis. A physician who is not involved in the study prepared the interventional medications.

Methods:

All patients will be subjected to the followings:

• History taking and demographic data collection (age, sex, weight, and ASA).
• Complete clinical examination.
• Routine Laboratory investigations

All patients will be instructed to fast according to the following guidelines:

2 hours for clear fluids, 4 hours for breastmilk, 6 hours for formula milk and other particulate fluids. EMLA cream (5%) will be applied to the anticipated puncture sites for IV cannulation and covered for 45 minutes before transport to the OR, to facilitate the insertion of an intravenous (IV) cannula. Premedication included intramuscular (IM) midazolam at 0.3 mg/kg and atropine at 0.02 mg/kg, administered 15 minutes before transportation to the operating room (OR). Upon arrival in the OR, standard monitoring equipment will be applied, including electrocardiography, non-invasive blood pressure, and pulse oximetry. The anesthesia machine and all necessary equipment and medications for general anesthesia (GA) will be prepared for each patient. The IV cannula will be inserted, secured and checked with a saline flush. IV midazolam at a dose of 0.1 mg/kg will be given at the time of spinal anesthesia administration to ensure immobility during the procedure.

A Pediatric Analog Sedation Score (PASS) will be used to evaluate sedation levels during the procedure as well as intraoperatively, where a score of 0 = no sedation, 1 = slightly sedated, 2 = moderately sedated, 3 = well sedated, and 4 = heavily sedated. The target sedation score is 1, indicating minimal sedation. The child will be positioned in the lateral decubitus position, and under strict aseptic conditions, the lumbar region will be sterilized using Betadine. A lumbar puncture will be performed at the L4-L5 interspace (Tuffier's line) using a 2.5-inch 22-gauge Quincke needle by an experienced anesthesiologist. A formula will be used to estimate the distance from skin to subarachnoid space (mm) = [2 × weight (kg)]+ 7(mm). This will be used as a guide to reduce chances of inserting the spinal needle too deep. Two attempts at obtaining a free flow of cerebrospinal fluid (CSF) will be allowed; if unsuccessful, the patient will be excluded from the study and switched to GA. A new attempt involves removing the needle and reinserting it. The calculated dose of hyperbaric bupivacaine 0.5% (Trade name: Sunnypivacaine, Manufacturer: Sunny Pharmaceuticals, Country: Egypt) will be aspirated and administered via a 3-ml syringe.

Group A:

Hyperbaric bupivacaine 0.5% will be administered based on weight:

• 0.4 mg/kg (0.08 ml/kg) for children weighing 5-15 kg
• 0.3 mg/kg (0.06 ml/kg) for children weighing >15 kg.

Group B:

Hyperbaric bupivacaine 0.5% will be calculated using Partha formula by dividing the child's age in years by 5. The resultant figure will be considered to be the dose of Bupivacaine in ml. If the number of months after the completion of a year in age is more than 6 months, the child's age will be noted to be the year older.

After obtaining free flow of CSF, and negative aspiration test for blood, the local anesthetic will be administered slowly. Then, the child will be placed in a supine position with a small pillow under the head. IV fluids will be administered at a rate of 4 ml/kg/hr. Sensory and motor levels will be assessed every minute for the first 5 minutes. The adequacy of the block will be determined by the lack of response to a firm skin pinch at the dermatomal level. The peak sensory level will be determined when the dermatomal level remained unchanged in at least two consecutive assessments. If the patient reported pain, the block will be considered failed, and they are excluded from the study. Motor blockade at or above the L1 level will be tested using superficial abdominal reflexes. After a maximum of ten minutes after spinal anesthesia, the target peak sensory level should be at least T10, and the Bromage score should be 3, indicating a complete motor block. Only then the surgery will be proceeded. Iff inadequate sensory or motor block are observed (e.g., peak sensory level below T10 or Bromage score <3), GA will be administered, and the failure will be documented.

Inclusion criteria

• Children aged 1-6 years

• Both genders.
• American Society of Anesthesiologists (ASA) physical status I or II.
• Elective infra-umbilical surgeries with anticipated duration ≤ 90 minutes.

Exclusion criteria

• Guardian refusal.

• Children with significant congenital heart disease (e.g., septal defects requiring surgical intervention)
• Children with neuromuscular disorders or high intracranial pressure.
• Children with spinal deformities or morbid obesity (body mass index (BMI) above the 99th percentile).
• Children with a history or family history of coagulation disorders.
• Children with local infection at the site of skin puncture for spinal anesthesia.
• Children with known allergy to Bupivacaine.
• Surgeries requiring Trendelenburg or prone position.
• Unexpected prolongation of surgery > 90 minutes