ICU patients: fatter is better?

The Impact of Obesity on Sudden Cardiac Death Risk

PURPOSE OF REVIEW

We aimed to describe the epidemiology of sudden cardiac death (SCD) in the obese, elaborating on the potential pathophysiological mechanisms linking obesity, SCD, and the outcomes in SCD survivors, as well as looking into the intriguing "obesity paradox" in these patients.

RECENT FINDINGS

Several studies show increased mortality in patients with BMI > 30 kg/m² admitted to the hospital following SCD. At the same time, other studies have implied that the "obesity paradox," described in various cardiovascular conditions, applies to patients admitted after SCD, showing lower mortality in the obese compared to normal weight and underweight patients. We found a significant body of evidence to support that while obesity increases the risk for SCD, the outcomes of obese patients post SCD are better. These findings should not be interpreted as supporting weight gain, as it is always better to prevent the "disaster" from happening than to improve your chances of surviving it. Obesity is shown to be significantly associated with increased risk for SCD; however, there is a growing body of evidence, supporting the "obesity paradox" in the survival of SCD victims. Prospectively, well-designed studies are needed to confirm these findings.

Diagnosis of obesity based on body composition-associated health risks-Time for a change in paradigm

Traditional diagnosis and understanding of the pathophysiology of obesity are based on excessive fat storage due to a chronically positive energy balance characterized by body mass index (BMI). Quantitative and qualitative analysis of lean and adipose tissue compartments by body composition analysis reveals that characterization of obesity as "overfat" does not facilitate a comprehensive understanding of obesity-associated health risk. Instead of being related to fat mass, body composition characteristics underlying BMI-associated prognosis may depend (i) on accelerated growth by a gain in lean mass or fat-free mass (FFM) in children with early BMI rebound or adolescents with early puberty; (ii) on a low muscle mass in aging, associated chronic disease, or severe illness; and (iii) on impaired adipose tissue expandability with respect to cardiometabolic risk. It is therefore time to call the adipocentric paradigm of obesity into question and to avoid the use of BMI and body fat percentage. By contrast, obesity should be seen in face of a limited FFM/muscle mass together with a limited capacity of fat storage.

Medical Versus Surgical ICU Obese Patient Outcome: A Propensity-Matched Analysis to Resolve Clinical Trial Controversies

OBJECTIVES

To determine the short- and long-term mortality of obese ICU patients following medical as opposed to surgical admission and the relation between obesity and mortality.

DESIGN

Retrospective analysis of prospectively collected data, using a propensity score-matched analysis of patients with medical or surgical admission.

SETTING

One French mixed medical-surgical ICU.

PATIENTS

Critically ill obese patients (body mass index ≥ 30 kg/m) and nonobese patients admitted during a 14-year period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Seven-hundred ninety-one obese patients and 4,644 nonobese patients were included, 338 (43%) and 2,367 (51%) medical and 453 (57%) and 2,277 (49%) surgical obese and nonobese patients, respectively. Mortality was significantly higher in medical than in surgical obese patients in ICU (25% vs 12%; p < 0.001) and up to 365 days (36% vs 18%; p < 0.001) post ICU admission. One-to-one propensity score matching generated 260 pairs with well-balanced baseline characteristics. After matching on propensity score, mortality was still significantly higher in medical patients both in the ICU (21% vs 13%; p = 0.03) and up to 365 days (30% vs 20%; p = 0.01) post ICU admission. Obesity was not significantly associated with mortality both in univariate analysis (140 obese patients [15%] in the dead group vs 651 [14%] in the alive group; p = 0.72) and multivariate analysis (odds ratio, 1.09 [95% CI, 0.86-1.38]; p = 0.49) after adjustment for Simplified Acute Physiology Score II, age, category of admission, history of cardiac disease, and history of respiratory disease.

CONCLUSIONS

After careful matching, the data suggest that ICU mortality in obese population was higher in the medical group than in the surgical group and remains significantly higher 365 days post ICU admission.

Metabolic support challenges with obesity during critical illness

Adiposity-based chronic disease, critical illness, and nutrition therapy increase the risk for overfeeding and worsened nutritional and clinical outcomes. Hypocaloric, high-protein nutrition therapy provides critically ill obese patients the opportunity to achieve net protein anabolism with a reduced risk for overfeeding-related complications. The intent of this review is to discuss the impact of obesity on clinical outcomes, describe the consequences of obesity that increase complications associated with nutrition therapy, provide the framework to develop a hypocaloric, high-protein regimen, review the scientific evidence to support this mode of therapy, and discuss its limitations. Practical suggestions for patient monitoring are also provided.

The obesity paradox in the ICU: real or not?

The obesity paradox has been used to describe the observed phenomenon described by several studies that indicated improved survival for critically ill patients with mild to moderate obesity when compared with their lean counterparts. The study by Arabi and coworkers challenges the obesity paradox concept for critically ill obese patients with septic shock. Their data indicate that obesity, per se, does not significantly improve mortality when outcomes are adjusted for differences in baseline characteristics and sepsis interventions. Further studies are needed to assess the influence of body weight, lean weight, and fat mass for optimizing fluid resuscitation, pharmacotherapy, and nutritional therapy for critically ill patients with sepsis.

The association between BMI and plasma cytokine levels in patients with acute lung injury

BACKGROUND

Obesity is associated with poor outcomes in many diseases, although recent data suggest that acute lung injury (ALI) is an exception. This is particularly interesting because obesity is marked by increased levels of proinflammatory mediators associated with increased morbidity and mortality in ALI. We hypothesized that cytokine response might be attenuated in patients who are obese and critically ill or that obesity might modify the relationship between plasma cytokines and clinical outcomes in ALI.

METHODS

We analyzed plasma biomarker levels (interleukin [IL]-6, IL-8, tumor necrosis factor-alpha receptor 1, surfactant protein D [SP-D], soluble intracellular adhesion molecule, von Willebrand factor (vWF), protein C, and plasminogen activator inhibitor-1) collected at baseline and day 3 in 1,409 participants in prior National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network (ARDSNet) trials. BMI was calculated for each patient, and associations with cytokine levels and ventilator-free days (VFDs), organ failure-free days (OFDs), and mortality were investigated in regression models adjusting for confounders.

RESULTS

In adjusted analyses, plasma IL-6 (P = .052), IL-8 (P = .001), and SP-D (P < .001) were inversely related to BMI, whereas vWF (P = .001) and WBC count (P = .042) increased proportionally with BMI. BMI was not associated with increased morbidity or mortality and did not modify the association between baseline biomarker levels and mortality, VFDs, or OFDs.

CONCLUSIONS

Patients who are obese and have ALI have lower levels of several proinflammatory cytokines, suggesting that the inflammatory response may be altered in patients with ALI and a high BMI. Lower SP-D but higher vWF suggests decreased epithelial and increased endothelial injury in the lung of patients who are obese. Mechanisms by which obesity may modulate innate immunity in critical illness are unclear, and future studies should elucidate such mechanisms.

Endocrine system and obesity

Obesity is associated with significant alterations in endocrine function. An association with type 2 diabetes mellitus and dyslipidemia has been well documented. This article highlights the complexities of treating endocrine system disorders in obese patients.

The association between body-mass index and patient outcome in septic shock: a retrospective cohort study

BACKGROUND

It is unknown whether body-mass index (BMI) and commonly defined BMI categories are associated with mortality in patients with septic shock.

METHODS

The database of a multidisciplinary intensive care unit (ICU) was retrospectively screened for adult patients with septic shock. BMI, demographic, clinical and laboratory variables together with outcome measures were collected in all patients. Subjects were categorized as follows: underweight, BMI < 18.5; normal weight, BMI 18.5-24.9; overweight, BMI 25-29.9; obesity, BMI >or= 30. Bivariate and multivariate logistic regression models were used to evaluate the association between BMI and outcome parameters.

RESULTS

In total, 301 patients with septic shock were identified. BMI was bivariately associated with ICU mortality (OR 0.91; 95% CI 0.86-0.98; P = 0.007). There was no significant association between BMI and ICU mortality in the multivariate model but an increasing BMI tended to be associated with lower ICU mortality (OR 0.93; 95% CI 0.86-1.01; P = 0.09). Although overweight (OR 0.43; 95% CI 0.19-0.98; P = 0.04) and obese (OR 0.28; 95% CI 0.08-0.93; P = 0.04) patients had an independently lower risk of ICU death than those with normal weight, there was no difference in the risk of ICU death between normal weight and underweight patients (P = 0.22). A high BMI was independently associated with a lower frequency of acute delirium (P = 0.04) and a lower need for ICU re-admission (P = 0.001) but with a higher rate of ICU-acquired urinary tract infections (P = 0.02).

CONCLUSIONS

BMI up to 50 does not appear to be associated with worse ICU and hospital mortality in patients with septic shock. In contrast, a high BMI may reduce the risk of death from septic shock.

Recently published papers: Heavyweight problems in the intensive care unit?

The management of the obese patient in intensive care is fraught with difficulty, or so conventional wisdom would have us believe. Two recent studies add to the growing evidence that the obese patient is not significantly disadvantaged in terms of outcome following intensive care admission. Another study highlights the increasing burden of end-stage renal disease on intensive care unit resources with some interesting results. And there is more on citrate, the new anticoagulant!