Effects of norepinephrine during intra-abdominal hypertension on renal blood flow in bacteremic dogs*:

Evaluation and Management of Abdominal Compartment Syndrome in the Emergency Department

BACKGROUND

Abdominal compartment syndrome is a potentially deadly condition that can be missed in the emergency department setting.

OBJECTIVE

The purpose of this narrative review article is to provide a summary of the background, pathophysiology, diagnosis, and management of abdominal compartment syndrome with a focus on emergency clinicians.

DISCUSSION

Abdominal compartment syndrome is caused by excessive pressure within the abdominal compartment due to diminished abdominal wall compliance, increased intraluminal contents, increased abdominal contents, or capillary leak/fluid resuscitation. History and physical examination are insufficient in isolation, and the gold standard is intra-abdominal pressure measurement. Abdominal compartment syndrome is defined as an intra-abdominal pressure >20 mm Hg with evidence of end-organ injury. Management involves increasing abdominal wall compliance (e.g., analgesia, sedation, and neuromuscular blocking agents), evacuating gastrointestinal contents (e.g., nasogastric tubes, rectal tubes, and prokinetic agents), avoiding excessive fluid resuscitation, draining intraperitoneal contents (e.g., percutaneous drain), and decompressive laparotomy in select cases. Patients are critically ill and often require admission to a critical care unit.

CONCLUSIONS

Abdominal compartment syndrome is an increasingly recognized condition with the potential for significant morbidity and mortality. It is important for clinicians to be aware of the current evidence regarding the diagnosis, management, and disposition of these patients.

Cardiorenal syndrome in sepsis: A narrative review

Multi-organ dysfunction is seen in nearly 40-60% of all patients presenting with sepsis, including renal and cardiac dysfunction. Cardiorenal syndrome type-5 reflects concomitant cardiac and renal dysfunction secondary to a systemic condition that primarily affects both organs, such as sepsis. There are limited data on the etiology, pathogenesis and clinical implications of cardiorenal syndrome in sepsis. Cardiac dysfunction and injury can be measured with cardiac biomarkers, echocardiographic dysfunction, and hemodynamic parameters. Acute kidney injury is systematically evaluated using serum creatinine and urine output criteria. This review seeks to systematically describe the epidemiology, risk factors, pathogenesis, diagnosis and management of cardiorenal syndrome type-5 in the setting of sepsis.

Effects of norepinephrine on tissue perfusion in a sheep model of intra-abdominal hypertension

BACKGROUND

The aim of the study was to describe the effects of intra-abdominal hypertension (IAH) on regional and microcirculatory intestinal blood flow, renal blood flow, and urine output, as well as their response to increases in blood pressure induced by norepinephrine.

METHODS

This was a pilot, controlled study, performed in an animal research laboratory. Twenty-four anesthetized and mechanically ventilated sheep were studied. We measured systemic hemodynamics, superior mesenteric and renal blood flow, villi microcirculation, intramucosal-arterial PCO2, urine output, and intra-abdominal pressure. IAH (20 mm Hg) was generated by intraperitoneal instillation of warmed saline. After 1 h of IAH, sheep were randomized to IAH control (n = 8) or IAH norepinephrine (n = 8) groups, for 1 h. In this last group, mean arterial pressure was increased about 20 mm Hg with norepinephrine. A sham group (n = 8) was also studied. Fluids were administered to prevent decreases in cardiac output. Differences between groups were analyzed with two-way repeated measures of analysis of variance (ANOVA).

RESULTS

After 2 h of IAH, abdominal perfusion pressure decreased in IAH control group compared to IAH norepinephrine and sham groups (49 ± 11, 73 ± 11, and 86 ± 15 mm Hg, P < 0.0001). There were no differences in superior mesenteric artery blood flow, intramucosal-arterial PCO2, and villi microcirculation among groups. Renal blood flow (49 ± 30, 32 ± 24, and 102 ± 45 mL.min(-1).kg(-1), P < 0.0001) and urinary output (0.3 ± 0.1, 0.2 ± 0.2, and 1.0 ± 0.6 mL.h(-1).kg(-1), P < 0.0001) were decreased in IAH control and IAH norepinephrine groups, compared to the sham group.

CONCLUSIONS

In this experimental model of IAH, the gut and the kidney had contrasting responses: While intestinal blood flow and villi microcirculation remained unchanged, renal perfusion and urine output were severely compromised.

[Abdominal compartment syndrome]

Abdominal compartment syndrome is defined as a pathological elevation of intraabdominal pressure associated with significant organ dysfunction and failure. Organ dysfunction mainly affects the renal, pulmonary, cardiac, gastrointestinal, and central nervous system. A high level of suspicion for this condition and early identification of patients at risk are mandatory for the successful management of abdominal compartment syndrome, which includes conservative and operative strategies.

Acute kidney injury following acute pancreatitis: A review

BACKROUND. Acute kidney injury (AKI) is a common serious complication of severe acute pancreatitis (SAP) and an important marker of morbidity and mortality in critically ill septic patients. AKI due to severe acute pancreatitis can be the result of hypoxemia, release of pancreatic amylase from the injured pancreas with impairment of renal microcirculation, decrease in renal perfusion pressure due to abdominal compartment syndrome, intraabdominal hypertension or hypovolemia. Endotoxins and reactive oxygen species (ROS) also play an important role in the pathophysiology of SAP and AKI. Knowledge of the pathophysiology and diagnosis of AKI following SAP might improve the therapeutic outcome of critically ill patients.

METHODS AND RESULTS

An overview of the pathophysiology, diagnosis and potential treatment options based on a literature search of clinical human and experimental studies from 1987 to 2013.

CONCLUSIONS

Early recognition of AKI and SAP in order to prevent severe complication like septic shock, intraabdominal hypertension or abdominal compartment syndrome leading to multiple organ dysfunction syndrome is a crucial tool of therapeutic measures in intensive care.

Measurement of intra-abdominal pressure in dogs and cats

OBJECTIVE

To review and summarize the human and veterinary literature on intra-abdominal pressure measurement techniques.

DATA SOURCES

Human and veterinary clinical studies, research articles, reviews, and textbooks with no date restrictions with a focus on techniques for intra-abdominal pressure (IAP) measurement and their limitations.

HUMAN DATA SYNTHESIS

Human literature has established the intravesicular method as the gold standard for indirect measurement of IAP. However, current research has explored the intragastric method as a valid alternative. Recently, debate has focused on the shortcomings of the various measurement methods.

VETERINARY DATA SYNTHESIS

Early human literature using dogs as models contributed to the original data for IAP measurements in small animals. Since that time, a number of clinical studies and 1 case report have contributed to that original information. A reference interval for IAP measured by the intravesicular method has recently been determined in healthy cats.

CONCLUSIONS

Further studies investigating IAP in critically ill veterinary patients are required to establish the optimal technique for this measurement in veterinary medicine.

Incidence, Risk Factors and Outcome Associations of Intra-Abdominal Hypertension in Critically Ill Patients

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are significantly associated with morbidity and mortality. We performed a prospective observational study and applied recently published consensus criteria to measure and describe the incidence of IAH and ACS, identify risk factors for their development and define their association with outcomes. We studied 100 consecutive patients admitted to our general intensive care unit. We recorded relevant demographic, clinical data and maximal (max) and mean intra-abdominal pressure (IAP). We measured and defined IAH and ACS using consensus guidelines. Of our study patients, 42% (by IAPmax) and 38% (by IAPmean) had IAH. Patients with IAH had greater mean body mass index (30.4±9.6 vs 25.4±5.6 kg/m2, P=0.005), Acute Physiology and Chronic Health Evaluation III score (78.2±28.5 vs 65.5±29.2, P=0.03) and central venous pressure (12.8±4.8 vs 9.2±3.5 mmHg, P <0.001), lower abdominal perfusion pressure (67.6±13.5 vs 79.3±17.3 mmHg, P <0.001) and lower filtration gradient (51.2±14.8 vs 71.6±17.7 mmHg; P <0.001). Risk factors associated with IAH were body mass index ≥30 (P <0.001), higher central venous pressure (P <0.001), presence of abdominal infection (P=0.005) and presence of sepsis on admission (P=0.035). Abdominal compartment syndrome developed in 4% of patients. IAP was not associated with an increased risk of mortality after adjusting for other confounders. We conclude that, in a general population of critically ill patients, using consensus guidelines, IAH was common and significantly associated with obesity and sepsis on admission. In a minority of patients, IAH was associated with abdominal compartment syndrome. In this cohort IAH was not associated with an increased risk of mortality.

A modified model of the abdominal compartment syndrome

BACKGROUND

To develop an animal model in rats and to investigate whether an intra-abdominal pressure (IAP) of 20 mm Hg will lead to a condition comparable with the abdominal compartment syndrome in humans.

METHODS

Forty Sprague-Dawley rats were used. In the study group, IAP was increased to 20 mm Hg using a nitrogen gas pneumoperitoneum for 4 hours. We also observed the next reperfusion period for another 4 hours. In the controls, IAP remained unchanged. Hemodynamic readings, peak inspiratory pressure, renal function parameters, and blood gas were obtained. Additionally, histopathologic examinations were performed.

RESULTS

In the presence of intra-abdominal hypertension (IAH), mean arterial pressure was reduced, whereas central venous pressure was increased significantly. Peak inspiratory pressure remained >35 mbar in the 4 hours of IAH and recovered after decompression. Arterial Po(2) decreased substantially while Pco(2) increased soon after IAH. IAH caused a metabolic acidosis, which was further complicated by the respiratory acidosis. Decompression resulted in normocapnia but the metabolic acidosis persisted. Renal blood flow and urine output decreased obviously, whereas little change was found in blood urea nitrogen and creatinine. The histopathologic study revealed parenchymal injury in lung and intestine.

CONCLUSIONS

This animal model was simple and easily reproducible. An IAP of 20 mm Hg can lead to a condition comparable with the abdominal compartment syndrome in humans.

Cardiorenal syndromes and sepsis

The cardiorenal syndrome is a clinical and pathophysiological entity defined as the concomitant presence of renal and cardiovascular dysfunction. In patients with severe sepsis and septic shock, acute cardiovascular, and renal derangements are common, that is, the septic cardiorenal syndrome. The aim of this paper is to describe the pathophysiology and clinical features of septic cardiorenal syndrome in light of the actual clinical and experimental evidence. In particular, the importance of systemic and intrarenal endothelial dysfunction, alterations of kidney perfusion, and myocardial function, organ “crosstalk” and ubiquitous inflammatory injury have been extensively reviewed in light of their role in cardiorenal syndrome etiology. Treatment includes early and targeted optimization of hemodynamics to reverse systemic hypotension and restore urinary output. In case of persistent renal impairment, renal replacement therapy may be used to remove cytokines and restore renal function.

[Intraabdominal hypertension and abdominal compartment syndrome]

Although intraabdominal pressure (IAP) has been studied for more than 100 years, the concepts of intraabdominal hypertension (IAH) and abdominal compartmental syndrome (ACS) have only been developed as clinical entities of interest in intensive care in the last 5 years. At the first Congress on Abdominal Compartment Syndrome in December 2004, a series of definitions were established, which were published in 2006. IAH is defined as IAP ≥ 12 mmHg and is classified in four severity grades, the maximum grade being ACS, with the development of multiorgan failure. The incidence of IAH in patients in intensive care units is high, around 30% at admission and 64% in those with a length of stay of 7 days. The increase in IAP leads to reduced vascular flow to the splenic organs, increased intrathoracic pressure and decreased venous return, with a substantial reduction in cardiac output. If IAH persists, these physiopathologic episodes are followed by the development of multiorgan failure with renal, cardiocirculatory and respiratory failure and intestinal ischemia. Mortality from untreated ACS is higher than 60%. The only treatment for ACS is surgical decompression. In patients with moderate IAH, medical treatment should be optimized, based on the following measures: a) serial IAP monitoring; b) optimization of systemic perfusion and the function of the distinct systems in patients with high IAP; c) instauration of specific measures to decrease IAP; and d) early surgical decompression for refractory IAH. The application of the medical measures that can reduce IAP and early abdominal decompression in ACS improve survival in critically ill patients with IAH.

Renal dysfunction associated with intra-abdominal hypertension and the abdominal compartment syndrome

Once considered mostly a postsurgical condition, intra-abdominal hypertension (IAH) and the abdominal compartment syndrome (ACS) are now thought to increase morbidity and mortality in many patients receiving medical or surgical intensive care. Animal data and human observational studies indicate that oliguria and acute kidney injury are early and frequent consequences of IAH/ACS and can be present at relatively low levels of intra-abdominal pressure (IAP). Among medical patients at particular risk are those with septic shock and severe acute pancreatitis, but the adverse effects of IAH may also be seen in cardiorenal and hepatorenal syndromes. Factors predisposing to IAH/ACS include sepsis, large volume fluid resuscitation, polytransfusion, mechanical ventilation with high intrathoracic pressure, and acidosis, among others. Transduction of bladder pressure is the gold standard for measuring intra-abdominal pressure, and several nonsurgical methods can help reduce IAP. The role of renal replacement therapy for volume management is not well defined but may be beneficial in some cases. IAH/ACS is an important possible cause of acute renal failure in critically ill patients and screening may benefit those at increased risk.

Nonoperative management of intraabdominal hypertension and abdominal compartment syndrome

Intraabdominal hypertension (IAH) and abdominal compartment syndrome (ACS) have detrimental effects on all organ systems and are associated with significant morbidity and mortality. In recent years, the diagnosis and management of these syndromes has evolved tremendously, and the importance of comprehensive strategies to reduce intraabdominal pressure (IAP) has been recognized. All clinicians should be aware of the risk factors that predict the development of IAH/ACS, the appropriate measurement of IAP, and the current resuscitation options for managing these highly morbid syndromes. The nonoperative management of IAH/ACS can be summarized using five therapeutic goals: evacuate intraluminal contents, evacuate intraabdominal space-occupying lesions, improve abdominal wall compliance, optimize fluid administration, and optimize systemic and regional tissue perfusion. Surgical intervention through open abdominal decompression should immediately be pursued for patients with progressive IAH, end-organ dysfunction, and failure that is refractory to these nonoperative therapies. This comprehensive management strategy has been demonstrated to improve patient survival and long-term outcome.