Comparison of indirect methods of measuring intra-abdominal pressure in children

Objective: To determine the most accurate indirect method of measuring intra-abdominal pressure (IAP) in children. Design and setting: Single-centre, prospective, clinical study in a 23-bed specialist paediatric intensive care unit in Australia. Patients and participants: 20 children admitted to paediatric intensive care with a peritoneal dialysis catheter in situ following congenital cardiac surgery. Interventions: IAP was measured directly via the peritoneal dialysis catheter and by intragastric manometry via an indwelling nasogastric tube, and by intravesical manometry via an indwelling transurethral urinary catheter, using volumes of 0, 1, 3 and 5 ml/kg body weight of sterile saline instilled into the bladder. Measurements and results: Across the range of IAPs of 1 8 mmHg the Bland-Altman method for assessing agreement between two methods of clinical measurement showed bladder pressure measured via the urinary catheter with 1 ml/kg body weight of saline instilled to be the most accurate indirect measurement technique, tending to give pressures between 0.07 and 1.23 mmHg higher than the direct measurement (95% CI for bias). Measuring bladder pressure with either no saline instilled or more saline per kilogram body weight instilled was less accurate over the same range of pressures, as was measuring the gastric pressure. Conclusions: The most accurate indirect method of measuring IAP in children over the normal range of IAPs involves measuring bladder pressure via a transurethral urinary catheter with 1 ml/kg body weight of sterile saline instilled into the bladder.