Obese Cardiac Surgery Patients a Burden on ICU Resources

Obese patients undergoing cardiac surgery are a greater burden on intensive care unit (ICU) resource utilization than patients with a normal body mass index (BMI), a new study shows.

After CABG, valve, and other cardiac surgeries, these patients spend more time in the ICU, have higher rates of readmission to the ICU, and require significantly more mechanical ventilation, report investigators.

“The patients we’re seeing now are definitely a lot different than the ones we saw 5, 10, or 15 years ago,” senior investigator Ansar Hassan, MD (Dalhousie Medicine New Brunswick, Saint John, Canada) told TCTMD. “Patients we’re operating on now are typically older, they have much more comorbid disease, such as diabetes, kidney failure, and poor lung function. And as part of the comorbid disease burden, we’re certainly seeing more obesity. And not just people who are mildly obese—we’re talking people who are morbidly obese.”

Given the rise in obese patients, Hassan and colleagues wanted to determine how obesity affected their resource utilization. Previous studies have focused on the effect of obesity on mortality and surgical complications, but few studies have addressed its impact on postoperative ICU resource use.

Better Shape Desirable but Not Always Possible

In their study, which is published August 10, 2017, in the Annals of Thoracic Surgery, the researchers analyzed all patients who underwent a cardiac operation through a median sternotomy between 2006 and 2013 at their center. This included 5,365 patients, of whom 1,948 were obese. The obese patients were further stratified by BMI: class I (BMI 30-34.99), class II (BMI 35-39.99), and class III obesity (BMI ≥ 40).

The patients we’re seeing now are definitely a lot different than the ones we saw 5, 10, or 15 years ago. Ansar Hassan

The obese patients had more comorbid disease than patients with healthy BMIs, including greater rates of smoking and NYHA class IV symptoms. Hypertension, dyslipidemia, renal failure, and diabetes, among other conditions, were also more prevalent in the obese patients. Following surgery, the in-hospital mortality rate was 1.7% and the average length of stay was 5 days.

In a risk-adjusted analysis, class II and III obese patients had a respective two- and fourfold higher risk of staying more than 48 hours in the ICU compared with normal-weight patients. Individuals with class III obesity had a more than threefold greater risk of requiring mechanical ventilation for more than 24 hours, while those with class II and III obesity were approximately three times more likely to end up back in the ICU than the normal-weight patients.      

“At the end of the day, these patients are coming to us and as much as we’d like them to be in better shape for their operation, often times we don’t have that luxury,” said Hassan. “These are operations that sometimes need to be done on an emergent or urgent basis. We have to deal with the aftereffects of [the patients] being obese.”

Mitigating Impact of Obesity on Resources 

In an attempt to mitigate the impact of obesity, Hassan said there are ongoing studies in nonemergent patients to determine if losing weight or improving fitness levels might reduce the risk of surgical complications. Another way is to simply accept the burden on ICU resources and look for ways to transfer obese patients from the ICU to a stepdown or intermediate unit and to have them stay there for an extended period, a process that might help reduce the risk of ICU readmissions.

Hassan also noted they have scheduled operations on obese patients on a Thursday or Friday, which allows for prolonged ICU time over the weekend when the unit is less strained.

In their analysis, respiratory failure was most common reason for ICU readmission, followed by cardiac and gastrointestinal complications. The availability of noninvasive forms of ventilation in the stepdown/intermediate unit might also mitigate the risk of readmission, said Hassan.  

The researchers are currently in the process of publishing data looking at the impact of obesity on clinical outcomes, but Hassan said the relationship is not clear cut. That analysis, which will be published soon, showed obese patients have higher rates of infection and renal failure at 30 days, but there was no consistent relationship with other endpoints, such as mortality, stroke, or readmissions. This speaks to the heterogeneity of obese patients, with some doing well and others poorly, he said.

“Even if you are ventilated for longer, in the ICU for longer, while this may not translate into difference in mortality, it does translate into significant resource utilization difference with an obesity classification,” said Hassan. “People who are in class II and III [obesity] definitely have a much higher impact on healthcare costs.”