Insertion of central venous catheters can be difficult in obese individuals. Dr. Kevin P. Blaine, Stanford University Medical Center, Stanford, California, and colleagues studied the ability of positive end-expiratory pressure (PEEP) to increase the cross sectional area, measured by ultrasound, of the internal jugular vein in obese patients. Their results are published in this month’s issue of Anesthesia & Analgesia in the article titled “Positive-End Expiratory Pressure to Increase Internal Jugular Vein Size is Poorly Tolerated in Obese Anesthetized Adults.”
The study authors compared 24 patients with an average BMI of 40 who received 5 and 10 cm H2O PEEP with no PEEP. Each increment of 5 cm H20 of PEEP increased cross section area by 0.16 cm2,orabout 13%. Notably, 25% of study subjects’ arterial pressure fell below 90/60 mm Hg when they were subjected to 10 cm H2O PEEP. Although the cross sectional area increased with PEEP, the authors did not demonstrate whether it increased the ease of internal jugular venous catheterization.
The authors claimed that it is often difficult to place central venous catheters in obese patients. Perhaps, but at least two studies found there was no difference. One is an earlier study from Stanford, and the other is from the University of Genoa. The authors noted that these patients poorly tolerated PEEP. Perhaps the hypotension could have been attenuated either by a prior fluid bolus or by head-down tilt.
As with most studies, this raises additional questions that require further investigation.