Cardio-respiratory changes with increased intra-bladder pressure in prone position during anesthesia

Twenty non-obese patients, 13–29 years of age, operated on for scoliosis were examined for cardio-respiratory changes that occur during positioning on bolsters, and the effect on the cardio-respiratory system of raised intra-abdominal pressure was evaluated. Hemodynamic and respiratory responses were measured when the position was changed from supine to prone and back to supine during anesthesia. We measured the intra-bladder pressure using a transurethral catheter (IBP) as an index of the intra-abdominal pressure. When the position was changed from supine to prone, the cardiac index (CI) decreased by 10–30% and the systemic vascular resistance index increased by 8–14%. IBP rose significantly (P 0.001), but it remained below 5mmHg. These changes continued to be mild until the patient was returned to the supine position. Pa_{O 2}, A-aD_{O 2}and Qs/Qt remained unchanged. CI decreased significantly (P 0.001) when IBP was increased to 10mmHg by abdominal compression, but was not affected when IBP was increased to only 5mmHg. It was concluded that mild abdominal compression in the prone position during anesthesia has little effect on the cardio-respiratory system in lean young subjects.(Hiraga Y and Hyodo M: Cardio-respiratory changes with increased intra-bladder pressure in prone position during anesthesia. J Anesth 6: 407–413, 1992)