Bedside nuclear medicine investigations in the intensive care unit

The functional nature of nuclear medicine procedures makes them especially valuable in the management of patients undergoing intensive care. However, the severe nature of the patient's condition invariably prevents him or her from attending the nuclear medicine department for diagnostic investigations. We have piloted a bedside nuclear medicine service using a four-probe detector system linked to an IBM computer with curve processing software. Protocols for a range of radionuclide probe investigations, including renal, hepatobiliary, gastric outflow and lung vascular permeability, using 99Tcm and 111In radiopharmaceuticals have been established. The measurement of lung vascular permeability in patients with clinical symptoms of adult respiratory distress syndrome was considered to be a valuable procedure on the intensive care unit. Due to the poor availability of 113Inm, which had previously been used for the measurement of lung permeability, we used a technique based on in vivo labelling of serum transferrin with 111In-chloride together with 99Tcm-red blood cells for the calculation of the plasma protein accumulation index. Other procedures include the measurement of gastric outflow in patients previously on parenteral feeding, and the assessment of hepatobiliary and renal function. The equipment proved to be reliable and convenient for use at the bedside, although ultrasound imaging was essential for the correct positioning of the probe detectors over smaller organs such as the kidneys and the gallbladder. The high sensitivity of the probe detectors required only low administered amounts of activity, minimizing radiation protection measures for patients and staff. The administration of radiopharmaceuticals via indwelling lines and tubes presented particular problems and we recommend that parenteral injections should not be given through manifold giving set, or via Teflon cannulae.