Sonographic Measurement of the IVC Diameter as an Indicator for Fluid Resuscitation: Beware of the Intra-abdominal Pressure.

Abstract

To Editor, We have been routinely using point-of-care ultrasound in evaluating shocked patients including the measurement of the inferior vena cava (IVC) diameter [1–3]. Nevertheless, there have been conflicting results regarding the value of measuring IVC diameter in monitoring fluid resuscitation [4–6]. We have recently noticed that IVC diameter was not useful in guiding the resuscitation and was even misleading in a case of severe acute pancreatitis having abdominal compartment syndrome. This experience highlights an important point which is usually neglected. A 29-year-old alcoholic male was admitted to the ICU of our hospital with severe colicky epigastric pain of 1-day duration radiating to the back and associated with nausea and vomiting. Serum amylase was 720 units/L. The patient was diagnosed as having acute alcoholic pancreatitis. The patient responded to fluid resuscitation. His blood pressure was 115/60 mmHg, urine output was 100 mL per hour, and his arterial lactate dropped from 5.8 to 1.9 mmol/L. Nevertheless, his intra-abdominal pressure raised to 38 mmHg. Surgeon-performed point-of-care ultrasound has shown significant intraperitoneal fluid, bilateral pleural effusion, reduced contractility of the heart, and an IVC diameter of 0.78 cm. As a response, fluids were restricted, the bed was raised in a straight antitrenderberg position which increased the space of the abdomen, nasogastric tube was inserted, the patient was ventilated using muscle relaxants, and percutaneous drainage of intraperitoneal fluid was performed. This approach dropped the abdominal pressure dramatically from 38 to 22 mmHg with improvement in the haemodynamic status. Repeated point-of-care ultrasound over 48 h showed gradual increase of the IVC diameter (Fig. 1a), improved contractility of the heart, and improved cardiac index. The patient gradually and slowly improved over time and was discharged home after 43 days. The measurement of IVC in this case was performed by an operator having more than 20-year experience in pointof-care ultrasound (FAZ) who used a standardized method to measure the IVC diameter (Fig. 1b) which overcomes technical pitfalls. There are other pitfalls in measuring the IVC diameter including the increased intra-thoracic pressure by mechanical ventilation and increased right atrial pressure by pulmonary embolism or pulmonary hypertension. These conditions will increase the diameter of the abdominal IVC [2]. The present case highlights that measuring IVC diameter is not useful in cases of increased intra-abdominal pressure or other cases having direct