Impact of Obesity in Critical Illness

Abstract

The prevalence of obesity is rising worldwide. Adipose tissue exerts anatomic and physiological effects with significant implications for critical illness. Changes in respiratory mechanics cause expiratory flow limitation, atelectasis, and V_/Q_ mismatch with resultant hypoxemia. Altered work of breathing and obesity hypoventilation syndrome may cause hypercapnia. Challenging mask ventilation and peri-intubation hypoxemia may complicate intubation. Patients with obesity are at increased risk of ARDS and should receive lung-protective ventilation based on predicted body weight. Increased positive end expiratory pressure (PEEP), coupled with appropriate patient positioning, may overcome the alveolar decruitment and intrinsic PEEP caused by elevated baseline pleural pressure; however, evidence is insufficient regarding the impact of high PEEP strategies on outcomes. Venovenous extracorporeal membrane oxygenation may be safely performed in patients with obesity. Fluid management should account for increased prevalence of chronic heart and kidney disease, expanded blood volume, and elevated acute kidney injury risk. Medication pharmacodynamics and pharmacokinetics may be altered by hydrophobic drug distribution to adipose depots and comorbid liver or kidney disease. Obesity is associated with increased risk of VTE and infection; appropriate dosing of prophylactic anticoagulation and early removal of indwelling catheters may decrease these risks. Obesity is associated with improved critical illness survival in some studies. It is unclear whether this reflects a protective effect or limitations inherent to observational research.Obesity is associated with increased risk of intubation and death in SARS-CoV-2 infection.Ongoing molecular studies of adipose tissue may deepen our understanding of how obesity impacts critical illness pathophysiology.

Incidence of Adverse Events Associated With the In-Hospital Transport of Critically Ill Patients

“…Only one study has examined physique in relation to body weight ( 2 ); it reported that transporting patients who weighed more than 65 kg involved a significantly increased risk of adverse events compared with transporting patients who weighed less than 65 kg (OR, 1.95 [1.30–2.94]). Physiologic changes such as decreased expiratory reserve and functional residual capacity make obese patients more prone to hypoxemia ( 14 ). Although body weight is directly related to transport difficulties, we examined BMI in this study because we believe that BMI influences changes in the physiologic status of patients more than body weight.…”

Adipose Tissue Inflammation and Pulmonary Dysfunction in Obesity

“…Recent studies have revealed a strong association between obesity and pulmonary hypertension, a condition characterised by an increase in mean pulmonary arterial pressure [7]. Alterations in respiratory system mechanics caused by obesity include expiratory flow limitation, atelectasis, and V/Q mismatch (occurring when either the ventilation airflow or perfusion blood flow is impaired, limiting the primary lung function of delivering oxygen to the blood) with hypoxaemia, all of which have important implications in the context of critical illness [10]. Tidal volume is also slightly lower in obese individuals; however, there is no significant effect on residual volume (RV) or total lung capacity (TLC) [1].…”

“…The rise in the prevalence of obesity affects the epidemiology of pulmonary diseases. Several studies have demonstrated that susceptibility to respiratory infections and hospitalisation rates are higher in obese patients than healthy-weight subjects [1,2,[10][11][12]. Chronic inflammatory diseases of the respiratory system develop based on the understanding of obesity as a state of chronic inflammation [1,11,13].…”

Drug dosing in hospitalized obese patients with COVID-19

“…Obesity is also associated with an increase in kidney mass but the effect on clearance is complex. Obesity, by itself is a risk factor for both chronic kidney disease and acute kidney injury and assessment of kidney function can be influenced by both assessment and indexing strategies [ 4 – 6 ]. Increases in clearance have been reported which could be due to the increase in renal blood flow [ 7 ].…”