A 67 year old male with a PMHx of DM presents with a chief complaint of cough and generalized weakness.
Vitals: T 102.4 HR 127 BP 77/58 RR 24 O2 88% on RA
You place the patient on O2 via nasal cannula and activate the sepsis protocol. He is empirically treated with broad spectrum antibiotics and IVFs are started. The chest x-ray shows multifocal pneumonia and you call hospital medicine to admit the patient. “What’s the blood pressure now,” the hospitalist asks. You glance at the monitor and murmur back, “92/63, but he looks pretty good.” The hospitalist asks you to insert a central line, start vasopressors, and contact the ICU. Instead, you wheel the ultrasound machine into his room, and ultrasound his IVC. Does this patient require a central line and vasopressors?
Answer and Learning Point
No, the patient’s IVC is small and collapsing almost 75% with normal respiratory variation. This predicts a fluid-responsive state. The patient was given another liter of lactated ringers, his blood pressure improved to 108/69, and his lactate cleared. You start maintenance IV fluids, call the hospitalist back, and the patient is admitted upstairs and does well.
- Fluid responsiveness is a controversial topic that continues to plague emergency medicine physicians and intensivists alike
- In patients whom a fluid bolus is being considered, ultrasound can be a useful tool to assess for cardiac function, lung fluid status (interstitial edema) and whether a patient will improve their cardiac output in response to this fluid challenge
- A recent study showed that the cIVC (inferior vena cava collapsibility) can be used as a predictor of who will be a fluid responder 
- cIVC = (IVC expiratory diameter - IVC inspiratory diameter)/IVC expiratory diameter
- Patients with a cIVC > 25% are likely to be fluid responders (LR + 4.56)
- Patients with a cIVC < 25% are unlikely to be fluid responders (LR - 0.16)
- The IVC should be examined in the subxiphoid region with the probe in a sagittal plane, and can be found by first identifying the right atrium and following this caudally
- A back-up approach involves using the liver as an acoustic window , placing the probe in the mid axillary line in a coronal plane, and fanning anteriorly and posteriorly until the IVC is visualized
- The IVC should be measured 3 cm caudal to the junction of the right atrium and IVC 
- M-mode can be used to evaluate the cIVC and has the advantage of measuring the exact same spot along the IVC over an extended period of time
- As with all adjuncts to clinical decision making, fluid responsiveness should not be determined solely on a single ultrasound measurement such as cIVC but should be taken into context with the rest of the clinical picture
This post was written by Amir Aminlari, MD, Ultrasound Fellowship Director at UCSD.
Corl KA, e. (2017). Inferior vena cava collapsibility detects fluid responsiveness among spontaneously breathing critically-ill patients. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 19 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/28525778
Nagdev AD, e. (2017). Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 19 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/19556029