Thursday, October 19, 2006

Trauma in the Obese....
We already know that obesity can be a hindrance in diagnosis. And in this month's Journal of the American College of Surgeons are two papers which discuss how obesity affects outcomes after trauma. The first: Impact of Obesity in the Critically Ill Trauma Patient: A Prospective Study
Obesity has risen at an epidemic rate over the past 20 years in the US. To our knowledge, there is an absence of data evaluating the impact of obesity in the critically ill trauma patient.

Prospective data were collected on 1,167 patients admitted to the ICU over a 2-year period. Obesity was defined as a body mass index (calculated as weight [kg]/height [m2]) of 30 or higher. Outcomes analyzed included infection rate, hospital and ICU length of stay, and mortality. Multiple logistic regression was used to evaluate outcomes between obese and nonobese patients for infection (infection versus noninfection) and mortality (deceased versus not deceased). Continuous outcomes such as hospital and ICU lengths of stay were evaluated using multiple linear regression analyses.

Sixty-two of 1,167 (5.3%) patients were obese. The majority (71%) of injuries in the study cohort were blunt. Although the majority of patients were men (76%), women (10% versus 4%) were more likely to be obese (p < 0.001). Obese patients had a more than twofold increase in risk of acquiring a bloodstream, urinary tract, or respiratory infection, or being admitted to the ICU (p < 0.001), after statistically controlling for age and Injury Severity Score. When controlling for diabetes, gender, obesity, age, COPD, and Injury Severity Score, obese patients were 7.1 times (95% CI, 2.06–8.9) more likely to die in the hospital.

Obesity is associated with a substantial increase in morbidity and mortality in the critically ill trauma patient. Future studies are warranted in both the prevention of infection and intensive care management of the obese trauma patient.

Unfortunately the JACS does not place their tables on the HTML version as pictures, so I am unable to grab any graphics from the article. Due to my inferior skills I am also unable to cut and paste the information and get the margins lined up correctly. My apologies. The data show that obesity is as strong a risk factor as age, diabetes, or COPD concerning total LOS as well as ICU LOS.

From the discussion:
The nature of substantial body mass has an impact on how health care providers deliver their care. In our study, we have shown that obese patients have a considerably greater number of ventilator days and pneumonia. This might be, in part, because of an intrinsic reduced lung capacity and increased work of breathing. These patients are also at greater risk of aspiration pneumonia. Procedures such as endotracheal intubation or tracheostomy are quite challenging because of immobility or thickness of subcutaneous tissue of the neck. These factors can play a role in delaying tracheostomy, potentially increasing ventilator days.

Vascular access in obese patients can also present a challenge to the health care provider. Difficulty in maintaining peripheral IV sites increases use of central venous catheters. Placement of central lines can be difficult because of lack of physical landmarks and increased distance to vessels. In critically ill obese patients, the persistent need for venous access is common and promotes the practice of longterm central access. This practice can increase the risk of line sepsis, as demonstrated in our study.

Obese patients have been shown in our study, as monitoring urine output continues to be an important part of ICU care, to have a considerably greater number of Foley catheter days. This almost certainly accounts for the more than twofold risk in urinary tract infections in our obese patients.

As we turn the page we find this article:Obesity Increases Risk of Organ Failure after Severe Trauma:
Obesity is an independent risk factor for a variety of diseases, including postinjury morbidity and mortality. Obesity is associated with a proinflammatory state that could affect the postinjury inflammatory response and increase risk of organ dysfunction. The purpose of this study was to determine the relationship between obesity and postinjury multiple organ failure (MOF).

Study design
A prospective observational study of patients at risk for postinjury MOF. Inclusion criteria were age older than 15 years, Injury Severity Score > 15, ICU admission within 24 hours of injury, and survival longer than 48 hours after injury. Isolated head injuries were excluded. Organ dysfunction was assessed using the Denver multiple organ failure score.

Data were collected on 716 severely injured patients, 70% were men and 83% were victims of blunt trauma. There was no relationship between body mass index and injury severity or the amount of blood transfused within 12 hours of injury. Postinjury MOF was observed in 123 of 564 (22%) nonobese patients and 56 of 152 (37%) obese patients. Obesity was independently associated with MOF (odds ratio, 1.8; 95% CI, 1.2–2.7) after adjusting for patient age, injury severity, and amount of blood transfused during resuscitation. In this study population, obesity was also associated with increased length of ICU and hospital stay but not death.

Obese patients are at increased risk of postinjury MOF. Study of the obesity-related inflammatory profile could provide additional insight into the pathogenesis of organ dysfunction and identify therapeutic targets for both obese and nonobese patients. Increased morbidity and length of stay in obese trauma patients implies greater resource allocation for this population.

Again, the spacing on the tables doesn't translate well to cut-and-paste, but the authors give some indication as to why this occurs:
When multiple systems were evaluated, we found that postinjury MOF was 1.8 times more likely to develop in obese patients than nonobese patients after adjusting for the previously established risk factors. Obesity was found to confer an increased risk of postinjury MOF greater than that of severe injury. MOF was more likely to develop within 72 hours of injury in obese patients than nonobese patients. Because early MOF is thought to reflect the effects of unbridled postinjury hyperinflammation as opposed to uncontrolled infection, this observation supports the proinflammatory nature of the obese state. Alternatively, early organ dysfunction could represent decreased physiologic reserve of these patients. Of those in whom MOF developed, there were no differences in the spectrum of involved organs between obese and nonobese patients. The lung was the most frequent organ involved, followed by the heart, liver, and kidney. It is interesting that once the threshold for MOF is reached, obese patients display the same organ dysfunction pattern as nonobese patients. This might be evidence that the final common pathway to postinjury organ dysfunction is not different between obese and nonobese patients. We conclude from these observations and previous research that obesity is associated with a proinflammatory state that influences the postinjury inflammatory response and resultant organ dysfunction.

And finally:
In summary, we found that obesity is a strong independent risk factor for postinjury organ dysfunction and MOF. These findings, in conjunction with evidence for an altered inflammatory potential in obese patients, might point to therapeutic targets to improve outcomes in both obese and nonobese patients. Finally, the shift toward a more obese population could affect use of trauma and critical care resources because of the higher risk of postinjury MOF.
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