How common is IAH and ACS in pediatrics:

Compared to the adult literature, relatively little research has been published regarding intra-abdominal hypertension in critically ill children. In 2001 an article by Beck et al suggested full blown abdominal compartment syndrome (elevated IAP plus organ failure) it was extremely rare, occurring in less than 1% of pediatric ICU admissions.[1] However, the authors did note that progression to ACS carried a 60% mortality rate, that abdominal compartment syndrome occurred at intra-abdominal pressures as low as 15 mm Hg, and that the syndrome existed in a broad array of medical and surgical patients, not just trauma patients. In contrast to Beck’s data, a prospective study presented at the society of critical care medicine in January 2006 suggested a dramatically higher incidence of ACS. Ejike et al found ACS to be present in 17.6% of ventilated PICU patients (they were only able to consent 1/3 of patients to enter the study, but even those who they had no clinical suspicion carried a 22% incidence of IAH and 7% of them progressed to ACS).[2] Those with ACS had a significantly higher mortality (33.3%) and length of stay (13 d) than those without ACS (2.4% mortality, 6 day LOS). Both of these studies as well as numerous other case series demonstrate this syndrome is not confined to trauma patients. It is ubiquitous to critically ill patients and occurs in children with many conditions including sepsis, Wilms tumor, perforated bowel, necrotizing enterocolitis, intussusception, meningococcemia and gastroschisis.[1, 3-5]

How much saline should be infused into a child’s bladder to obtain an adequate pressure measurement?

Accurate pressure transduction requires a small pocket of fluid within a cavity connected via a continuous column of fluid to the transducer. (See "Volume of infusion" discussion and diagram on this web site). The size of this pocket can be small as long as that fluid pocket is equilibrated with the pressure in the cavity being measured. When using the bladder to reflect pressure within the abdomen there needs to be some fluid to passively transmit intra-abdominal pressure, but not too much fluid. If the bladder is overdistended, the bladder wall begins to stretch and pressure measurements will rise to reflect bladder wall compliance, not intra-abdominal pressure. Two investigators have conducted research in pediatric ICU’s to determine the optimal volume of infusion to accurately transduce intra-abdominal pressure. Davis et al compared intra-abdominal pressure measured via a peritoneal dialysis catheter (gold standard) against IAP measured via the stomach and via the bladder using infusion volumes of 0, 1, 3 and 5 ml/kg. He found 1 ml/kg infused into the bladder to be the most accurate, while smaller or larger volumes were less accurate as was any volume infused when measuring gastric pressure.[6] Ejike measured bladder compliance curves in children by infusing increasing volumes and measuring each pressure obtained with that volume.[7] She found that optimal volumes ranged from 6 ml to 25 ml in children between 3 kg and 50 kg. She concluded that 6 ml was enough in all situations and one never needed more than 20-25 ml in any child to obtain accurate IAP transduction via the bladder. Therefor, these two studies suggest that one can either use 1 ml/kg (not ever needing more than 20-25 ml) or just use 6 ml infusion volume in pediatric patients to obtain accurate pressure transduction.

1. Beck, R., et al., Abdominal compartment syndrome in children. Pediatr Crit Care Med, 2001. 2(1): p. 51-6.
2. Ejike, J.C. and M. Mathur, Occurence and outcome of abdominal compartment syndrome in critically ill children. Critical Care Medicine, 2005. 33(12 supplement): p. A95, Abstract 158-M.
3. Ng, E., et al., Life threatening tension pneumoperitoneum from intestinal perforation during air reduction of intussusception. Paediatr Anaesth, 2002. 12(9): p. 798-800.
4. DeCou, J.M., et al., Abdominal compartment syndrome in children: experience with three cases. J Pediatr Surg, 2000. 35(6): p. 840-2.
5. Kidd, J.N., Jr., et al., Evolution of staged versus primary closure of gastroschisis. Ann Surg, 2003. 237(6): p. 759-64; discussion 764-5.
6. Davis, et al., Comparison of indirect methods of measuring intra-abdominal pressure in children. Intensive Care Med, 2005. 31(3): p. 471-475.
7. Ejike, J.C. and M. Mathur, Optimal Bladder Volumes For Intra-abdominal Pressure Measurement In Small Children. Critical Care Medicine, 2005. 33(12 supplement): p. A93, Abstract 150-M.