INTRAABDOMINAL PRESSURE

The abdominal pressure is a hydrostatic one, which can be measured in the bladder, the rectum and the stomach. In physiologic conditions, th e abdominal pressure is variable, with peaks as high as 100 to 200 mmH g at the time of defecation, cough. The increase in abdominal pressure elicited by abdominal distension or compression acts directly on the abdominal compartment, indirectly on the thoracic compartment, and mod ifies the circulation and the ventilation. Venous return is decreased as the inferior vena cava is compressed. The systemic resistances are also increased as the abdominal vessels are compressed. Therefore the circulation is mainly distributed to the superior part of the body. Al through the cardiac output is decreased, the usual haemodynamic parame ters remain in the normal range : arterial pressure is increased, hear t rate is unchanged, central venous pressure is increased, cardiac fai lure is unusual. The abdominal distension is also responsible for a re strictive respiratory syndrome, mainly due to the ascension of the dia phragm. The compression of the abdominal content explains renal effect s and the decreased diuresis. A sustained increase in abdominal pressu re occurs in several clinical conditions. During coelioscopy, abdomina l pressure is a under control and the cardiovascular effects are minor . Insufflation with CO2 carries the risk of hypercapnia, gas embolism and pneumothorax. During abdominal tamponade, anuria is directly relat ed to the level of pressures. At an abdominal pressure over 25 mmHg, a nuria is common and decompression becomes essential. The G suit increa ses arterial pressure either by elevating vascular resistances or incr easing blood content in the upper part of the body. Therefore cardiac tolerance can be decreased especially in cardiac patients. The adverse effects of abdominal pressure can also be observed in case of periton eal dialysis and ascites. The risk of regurgitation associated with an increased abdominal pressure must also be kept in mind. The abdominal pressure plays an important role in anaesthesia as well as in surgery . Therefore its measurement, which is easy, should become a routine.