The hi-map scan: The use of emergency ultrasound to evaluate haemodynamically unstable patients in the emergency setting

Abstract

The HI-MAP (Heart, IVC, Morrison’s pouch, Aorta, Pneumothorax) scan is a focussed bedside ultrasound examination designed to assess the hydration status of patients by quick assessment of cardiac contractility, inferior vena cava collapsibility during inspiration, the aorta and the presence of free fluid in the abdomen or chest. In the Emergency Centre (EC) this non-invasive tool can assist in early accurate diagnosis of critically ill patients. The aim of this study is to demonstrate the use of the HI-MAP scan in a tertiary EC in KZN to assist in diagnosis and determine hydration status in critically ill patients. This is a cross sectional retrospective descriptive study of HI-MAP scans performed on critically ill patients admitted to the EC from January 2010 until October 2011. The scans were performed by level 2 emergency ultrasound trained doctors. Provisional diagnosis using clinical skills and history was documented on admission. The HI-MAP scan was performed and final diagnosis documented in the database, based on clinical findings as well as ultrasound findings. Diagnosis was categorized into fluid overload, cardiogenic and hypovolaemic shock. A total of 133 patients were included. When provisional compared to final diagnosis after HI-MAP, 87(66%) patients had the same diagnosis confirmed by ultrasound. Forty six (34%) patients had different diagnosis after HI-MAP was performed. In fluid overloaded patients 95% had either poor contractility or Inferior vena cava collapsibility index (IVC-CI) of less than 25%. In hypovolaemic patients 96% had either hyperdynamic cardiac contractility or IVC-CI of less than 50%. HI-MAP scan is a good non-invasive tool for assessing volume status in critically ill patients and can be used to categorize patients into fluid overload, cardiogenic shock or hypovolaemic shock. Cardiac contractility and IVC-CI are the two most sensitive components of this scan.