The Effect of Bladder Instill Volume on Intra Bladder Pressure Measurement in Critically Ill Patients When Positioned with the Head of Bed Elevated to Thirty Degrees

Sunday, November 1, 2009

Melanie Horbal Shuster, PhD, RN
Allegheny Center for Digestive Health, West Penn Allegheny Health System, Pittsburgh, PA

Learning Objective 1: understand the relationship between bladder instill volume and intra bladder pressure

Learning Objective 2: understand the relationship between body position and intra bladder pressure

Introduction:  The World Society of Abdominal Compartment Syndrome (WSACS) by consensus recommends measurement of intra bladder pressure (IBP) with a 25 ml bladder instill volume (BIV) while lying supine and flat.  This is against critical care expert opinion and practice guidelines.  Aims:  To simultaneously assess the effect of BIV and a position that reflects current recommendations to reduce aspiration pneumonia. Method: One hundred and twenty (120) ICU patients were randomly assigned to have IBP measured using the method of Kron, and the Abviser with the transducer leveled at the symphysis pubis.  Patients were studied in one of twelve possible combinations of BIV and body position.  The randomized BIV were 25, 50 and 200 ml, and the randomized body positions were supine (S), or a 30º HOBE either supine (S30), right lateral (RL), left lateral (LL).  Data were analyzed by two-way ANOVA.  Results:  A significant volume (p<0.05), position (p<0.007) and volume-position interaction (p<0.004) was found.  The 25 and 50 ml BIV gave comparable values and inter-patient variability in all HOBE positions.  The 200 ml BIV resulted in higher IBP values than the 25 and 50 ml BIV and greater inter-patient variability.  The S position yielded lower values than the S30, RL and LL for each volume (p < 0.01).  Higher BIV resulted in higher IBP in the S and RL positions; and not observed in the S30 or LL positions.  There was no statistically significant difference in IBP among the S30, RL and LL positions using a 25 ml BIV.  Conclusion:  Results confirm findings of previous studies of independent effects of BIV and position in IBP measurements in the supine position but additionally demonstrate an interaction between these variables.  Results validate the WSACS recommendation for BIV in all HOBE positions and suggest that S30, RL, and LL positions could be used.