Abdominal Compartment Syndrome

John Hartley

Powerpoint File

Abdominal compartment syndrome (ACS) is a poorly understood entity in which abnormal elevation of intra-abdominal pressure (IAP) leads to progressive organ dysfunction. ACS has been defined as the adverse physiological consequences of an acute elevation in IAP which are typically manifest as increases in airway pressures, progressive oliguria, and reduced cardiac output. A chronic form of ACS may occur but is beyond the scope of this presentation. ACS can occur in both medical and surgical patients but victims of major trauma and patients undergoing complex abdominal procedures for peritonitis, ischaemia and bleeding (including ruptured abdominal aortic aneurysm) appear to be particularly at risk.

The exact incidence of ACS is unclear, but it has been suggested that 0.1 to 33 per cent of postoperative and trauma patients may develop some element of ACS. The importance of recognition of ACS lies in the potential reversibility of this syndrome by timely abdominal decompression. Unresolved ACS is likely to be fatal whilst case series report survival rates following decompression ranging from 17 to 75 per cent. However, there are no controlled data to support the efficacy of surgical decompression and though decompression may lead to initial improvement in airway pressures, oliguria and cardiac output many patients will eventually succumb from multiple organ failure (MOF). It is unclear whether these deaths may be preventable by earlier recognition of ACS and decompression, or whether ACS represents part of a relentless progression to MOF.

Intra-vesical pressure can be readily measured at the bedside via a transurethral catheter and correlates well with IAP. However, absolute values of IAP vary with body mass index so that IAP must be assessed in context with the patients clinical situation. In general terms IAP greater than 20 mmHg should be considered significant in almost all patients whilst pressure above 15mmHg will lead to some degree of ACS in many. Gross ACS should be easily recognised and prompt rapid decompression by laparotomy and laparostomy, however the management of lesser degrees of ACS is controversial and relies upon repeated assessment and clinical judgement. Routine measurement of IAP in patients at risk for ACS would appear sensible, however it is clear from postal surveys that this is undertaken routinely in a minority of intensive care units in the UK. In addition there is no consensus on the optimal timing of measurement or the indications for abdominal decompression.

The management of the open abdomen following decompression is complex and requires attention to fluid loss and protection of the underlying viscera from trauma and dessication. Options for laparostomy management include simple saline soaked abdominal packs beneath an occlusive and watertight dressing, covering the bowel with a non-adherent sheet (a number of variations of the so-called “Bogota bag” have been described), some form of prothetic mesh, or one of the commercially available vacuum dressings. None of these is without complication, prinicipally the development of fistula, and the aim should be to achieve early definitive abdominal closure where possible. In perhaps the 50 per cent of patients in whom early laparostomy closure is not possible healing is allowed to progress by secondary intention with or without skin grafting. Subsequent development of significant ventral herniation is likely and this in itself may represent a significant surgical challenge.

In summary there is increasing awareness of the importance of ACS in general surgical practice. At present is seems possible that ACS is an under diagnosed entity in the UK. Increasing awareness of ACS and a willingness to measure IAP in high risk surgical populations should lead to a better understanding of the pathophysiology of ACS and permit evidence based management plans to be formulated.

References

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2. A.F.K Moore, R. Hargest, M. Martin et al. Intra-abdominal hypertension and the abdominal compartment syndrome. Br J Surg 2004;91:1102-1110

3. Ravishankar N, Hunter J. Measurement of intra-abdominal pressure in intensive care units in the United Kingdom: a national postal questionnaire study. Br J Anaesth 2005;94:763-6

4. Malbrain ML, Chiumello D, Pelosi P et al. Incidence and prognosis of intraabdominal hypertension in a mixed population of critically ill patients: a multiple center epidemiological study. Crit Care Med 2005;33:315-22