Assessing intravascular volume on an obese patient


“Doctor, I can’t get the blood pressure cuff around her arm.” You aren’t surprised by your trauma nurse’s comment as you stare at the 450-pound woman lying on a backboard in front of you. EMS miraculously cut her out of her tiny two-door sedan with the jaws of life and dropped her off in your ED, with a 22 gauge IV in her right hand and her left leg extended in traction. The patient is screaming about her leg, but her robust body habitus precludes you from determining if she has any swelling or deformity on that side.  Each of her thighs is as wide as your waist, but fortunately, you can palpate her dorsalis pedis pulses bilaterally. Her abdomen is soft, but she screams in pain in response to palpation anywhere on her body. She probably does have a broken leg, but you fear that in addition to that she may be one of the many who suffer from the affliction you like to call “LPT” (Low Pain Threshold). You know the type – the ones who scream when you press lightly to see if they have pre-tibial edema.

As you begin your eFAST exam (More on the “extended” FAST exam in an upcoming column), your nurse attempts to wrap the BP cuff around the patient’s forearm and another around her lower leg. Neither extremity provides a consistent BP reading. Your patient’s heart rate is 125 bpm and it would be nice to know if her tachycardia is secondary to her pain or from volume loss.

You start your eFAST exam by examining the patient’s right upper quadrant for free fluid and suddenly remember that bedside ultrasound can also help you gauge intravascular volume status in a matter of seconds. After you visualize Morrison’s Pouch, you fan your probe through the liver and obtain a nice clear view of the IVC as it courses along the liver’s posterior-inferior edge. (See Image).


Based on this ultrasound image, does your patient need a couple boluses of IV fluids or just some more pain medication?

You finish your eFAST exam by scanning through the patient’s left upper quadrant, ensure there is no free fluid in her Pouch of Douglas, take a quick peek at her pericardial sac, and then evaluate above the diaphragm for a pneumothorax or hemothorax. Her IVC measurements are below the normal diameter of 1.6-1.75cm, but at least they are above the 0.8-1cm value that usually signifies significant hypovolemia. Putting your measurements together with the clinical picture, you decide to give her a 2L bolus of normal saline and await her chest X-ray, pelvis X-ray, and extremity X-ray results. As you are completing your secondary survey and waiting for the CT scanner to open up, you decide to take another quick peek at the IVC again. This time, the mean diameter has dropped down to 1.1 cm. She must be losing blood somewhere.


You finish repeating her eFAST exam and conclude it must be her suspected femur fracture just as her X-ray images finally arrive on the PACS machine to confirm your suspicions. You have emergency release blood hooked up to your Level 1 transfuser as you place a page out to your on-call orthopedic colleague. As your patient is being wheeled down the hallway towards the CT scanner your nurse holds up an extra-large BP cuff and says, “I guess we don’t need this anymore.” You tell her to throw it next to your discarded stethoscope since you won’t be using either of them as much with your new trusty ultrasound machine in hand.


  1. Jose Torres on

    Is there also a role of assessing the collapsability of this IVC as well? Over 50% compressibility means hypovolemia as well? do then both compressibility and ivc size should both be used? what position does the pt have to be? supine or upright or trendelenberg?

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