Intra-abdominal hypertension: Incidence and association with organ dysfunction during early septic shock

Abstract

Purpose

The objective of this article is to study the cumulative incidence of intra-abdominal hypertension (IAH) in septic shock (SS) patients during the first 72 hours of intensive care unit (ICU) admission and to determine if the presence and severity of IAH are associated with sepsis morbidity and mortality.

Materials and Methods

Eighty-one consecutive SS patients admitted to a surgical-medical ICU of an academic university hospital (January 2005 to January 2006) were included. Intra-abdominal pressure (IAP) and abdominal perfusion pressure (APP) were measured every 6 h (intermittently) for 72 h. Intra-abdominal pressure was registered as minimal, mean, and maximal values per day, during shock and throughout the study period. Intra-abdominal hypertension was diagnosed if IAP remained 12 mm Hg or higher on 2 consecutive measurements and stratified according to the most recent consensus definition (www.wsacs.org).

Results

According to maximal and mean IAP values, 67 (82.7%) and 62 (76.5%) of the patients developed IAH during the study period, respectively. Mean IAP values remained stable throughout the study period. Surgical patients had a higher incidence of IAH than medical patients (93% vs 73%, P < .009). Maximal IAPs were normally distributed, with nonsurvivors exhibiting significantly higher IAP levels during shock (survivors, 17.2 ± 5.3; nonsurvivors, 19.9 ± 5.6 mm Hg; P < .04). Patients with IAH exhibited significantly lower values of APP and diuresis, higher values of lactate and creatinine, and higher maximal norepinephrine doses, and were more frequently mechanically ventilated (P < .05 for all). Increasing degrees of IAH and the development of the abdominal compartment syndrome were associated with lower APP and higher maximal serum creatinine levels (P < .03 for both).

Conclusions

Septic shock patients have a very high incidence of IAH, which seems to be associated with the severity of shock and could be related to the development of organ dysfunctions, particularly renal dysfunction. Intra-abdominal pressure should be routinely monitored during the course of SS.

Introduction

Intra-abdominal hypertension (IAH) is defined by a sustained or repeated pathologic elevation of intra-abdominal pressure (IAP) higher than 12 mm Hg. The deleterious effects of IAH were first described more than 200 years ago [1]. Intra-abdominal hypertension may contribute to splanchnic hypoperfusion and development of multiple organ failure in critically ill patients [2], [3], [4], [5].

Reported prevalence of IAH in critically ill patients ranges from 18% to 58.8% [6], [7], [8], [9], [10]. This wide variation is explained by different clinical settings (surgical or medical) and conditions (trauma, burned and postoperative patients), the IAP measurement technique used, and the cutoff IAP level defined for diagnosis of IAH (12-25 mm Hg) [10]. Using a cutoff value of 12 mm Hg to define IAH in a mixed general intensive care unit (ICU) population, Malbrain et al [6], [10] reported a prevalence of 58.8% and a cumulative incidence during the first week of ICU admission of 57.7%, with maximal IAP values, but only 26.8% with mean values.

In 2004, when the World Society on the Abdominal Compartment Syndrome (WSACS) was founded, consensus definitions and grading for IAH were proposed [11], [12] (www.wsacs.org). Intra-abdominal hypertension was defined as a sustained or repeated pathologic elevation of IAP 12 mm Hg or higher, and was graded into 4 levels (grade 1, 12-15 mm Hg; grade 2, 16-20 mm Hg; grade 3, 21-25 mm Hg; and grade 4, >25 mm Hg). Abdominal compartment syndrome (ACS) was defined as a sustained IAP higher than 20 mm Hg (with or without abdominal perfusion pressure [APP] <60 mm Hg), which is associated with a new organ dysfunction [13]. Primary ACS is a condition associated with injury or disease in the abdominopelvic region, which frequently requires early surgical or interventional radiologic procedures, and secondary ACS refers to conditions that do not originate from the abdominopelvic region.

Previous studies on IAH have focused mainly on trauma [14], [15], [16], surgical [17], [18], [19], burned [20], and obese [16] patients, and an elevated prevalence of IAH has also been reported in sepsis [21]. However, limited information exists about the prevalence and consequences of IAH in septic shock (SS) patients [22]. Septic shock patients usually have increased gut permeability and ileus, together with other risk factors for IAH, such as massive fluid resuscitation. Intra-abdominal hypertension could aggravate hemodynamic instability and hypoperfusion, contributing to organ dysfunction in this setting [23].

In an earlier study, our group found a 51% incidence of IAH in a small series of surgical and medical SS patients [24]. However, a higher level of IAP (≥20 mm Hg) than proposed by the consensus conference was used to define IAH, possibly underestimating the real incidence of IAH in SS patients.

Therefore, the aim of this study was to determine the cumulative incidence of IAH in SS patients during the first 72 hours of ICU admission, according to the new consensus definitions [11], [12]. The secondary objective was to determine if the presence of IAH and its different levels of severity are associated with more severe forms of SS in terms of vasopressor requirements, lactate levels, severity of organ dysfunctions, and mortality.