Effects of intra-abdominal pressure on liver function assessed with the LiMON in critically ill patients

Intra-abdominal pressure (IAP) is the steady-state pressure concealed within the abdominal cavity and is influenced by body weight, body position and abdominal muscle activity.1–3 A transient increase in IAP, such as pneumoperitoneum during laparoscopic surgery, causes only minimal adverse effects. Several clinical conditions, such as ascites and blood accumulation, tumours, burn eschars, edema, bowel distension5 and closure of a swollen and noncompliant abdominal wall,6 can cause a persistent increase in IAP.4–8 There has been a growing interest in the concept of IAP and in the impact of intra-abdominal hypertension (IAH) on organ dysfunction in critically ill patients.8,9 A pathologic increase in IAP has negative effects on splanchnic, respiratory, cardiovascular, renal and neurologic function. Intra-abdominal hypertension is defined by a sustained or pathologic elevation in IAP equal to or above 12 mm Hg, whereas abdominal compartment syndrome (ACS) is defined as an IAP above 20 mm Hg. Intra-abdominal hypertension not only has harmful consequences for different organ systems, but also is associated with mortality.8–12 In addition, it is associated with splanchnic hypoperfusion; thus, monitoring of regional organ blood flow and function is often crucial for guiding therapy in critically ill patients and is highly recommended.10,11,13 The dynamic liver test indocyanine green plasma disappearance rate (ICG-PDR) should provide better direct measurement of liver function and has been suggested as a marker of global hepato-splanchnic blood fow.14 The ICG-PDR is the most commonly used ICG-derived parameter for clinical and experimental assessment of liver function; the normal range is 18%–25% per minute. Noninvasive means of measuring ICG elimination using dye densitometry have been described since 1967, and the advent of pulse oximetry and subsequently pulse dye densitometry have led to the development of commercially available equipment for pulse spectrophotometry.15 The only such device currently in use in Turkey is the noninvasive liver function monitoring system LiMON (Pulsion Medical Systems). Previous studies have shown the value of measuring ICG-PDR for assessing prognosis.16,17 The aim of this study was to assess the effects of IAH on liver function using the LiMON and to assess the prognostic value of IAP in critically ill patients.