Fresh gas formulae do not accurately predict end-tidal PCO2 in paediatric patients

Area of Science:

• Anesthesiology
• Pediatric Critical Care
• Respiratory Physiology

Background:

• Accurate fresh gas flow (FGF) is crucial for maintaining appropriate ventilation in pediatric patients during anesthesia.
• Existing formulas for FGF requirements may not account for individual patient variability.

Purpose of the Study:

• To determine optimal fresh gas flow (FGF) requirements for pediatric patients undergoing anesthesia.
• To evaluate the efficacy of established FGF formulas in maintaining target end-tidal PCO2 (PETCO2) levels.

Main Methods:

• Measurements of FGF were conducted in pediatric patients (3.8-20 kg) using Sechrist Infant Ventilator or Air-Shields Ventimeter with a Mapleson D circuit.
• Target distal end-tidal PCO2 (PETCO2) levels of 30 and 38 mmHg were maintained.
• FGF requirements were calculated as 500 ml.kg-1.min-1 for PETCO2 of 30 mmHg and 250 ml.kg-1.min-1 for PETCO2 of 38 mmHg when minute ventilation was greater than or equal to FGF.

Main Results:

• Established FGF formulas yielded significant variations in PETCO2 measurements when applied to a new group of pediatric patients.
• The previously determined FGF requirements did not consistently maintain the desired PETCO2 levels across all patients.

Conclusions:

• Formulas for FGF requirements in pediatric anesthesia may lack precision due to inter-patient variability.
• Continuous monitoring of PETCO2 in each pediatric patient is essential for accurate FGF adjustment.
• Individualized FGF titration based on real-time PETCO2 monitoring ensures the safest and most accurate ventilation.