Lithium dilution measurement of cardiac output and arterial pulse waveform analysis: an indicator dilution calibrated beat-by-beat system for continuous estimation of cardiac output.

Lithium dilution cardiac output (LiDCO trade mark; LiDCO, London, UK) is a minimally invasive indicator dilution technique for the measurement of cardiac output. It was primarily developed as a simple calibration for the PulseCO trade mark (LiDCO, London, UK) continuous arterial waveform analysis monitor. The technique is quick and simple, requiring only an arterial line and central or peripheral venous access. These lines would probably already have been inserted in critical care patients. A small dose of lithium chloride is injected as an intravenous bolus, and cardiac output is derived from the dilution curve generated by a lithium-sensitive electrode attached to the arterial line. Studies in humans and animals have shown good agreement compared with results obtained with other techniques, and the efficacy of LiDCO trade mark in pediatric patients has also been proven. Compared with thermodilution, lithium dilution showed closer agreement in clinical studies with electromagnetic flow measurement.PulseCO trade mark is a beat-to-beat cardiac output monitor that calculates stroke volume from the arterial pressure waveform using an autocorrelation algorithm. The algorithm is not dependent on waveform morphology, but, rather, it calculates nominal stroke volume from a pressure-volume transform of the entire waveform. The nominal stroke volume is converted to actual stroke volume by calibration of the algorithm with LiDCO trade mark. Initial studies indicate good fidelity, and the results from centers in the United States and the United Kingdom are extremely encouraging. The PulseCO trade mark monitor incorporates software for interpretation of the hemodynamic data generated and provides a real-time analysis of arterial pressure variations (ie, stroke volume variation, pulse pressure variation, and systolic pressure variation) as theoretical guides to intravascular and cardiac filling.

A randomised controlled trial investigating the effects of dopexamine on gastrointestinal function and organ dysfunction in the critically ill.

OBJECTIVE: To determine whether an infusion of dopexamine for up to 7 days has an effect on gastrointestinal (GIT) absorption and permeability, renal function or organ dysfunction in the critically ill. DESIGN AND SETTING: Prospective, randomised controlled clinical trial in two general adult intensive care units. PATIENTS: 102 critically ill adult patients predicted to require organ support for at least 4 days. INTERVENTIONS: After resuscitation patients were randomly assigned to receive an infusion of up to 2 mcg/kg/min [corrected] per minute of dopexamine or control. MEASUREMENTS AND RESULTS: GIT absorption and permeability were measured using the ratio of absorbed rhamnose to 3- O-methyl- D-glucose and the ratio of lactulose to rhamnose on days 1, 4 and 7. Creatinine clearance was measured concurrently. Daily Sequential Organ Failure Assessment scores were calculated. Fifty-two patients received dopexamine. No significant difference between the two groups emerged on any of the measured parameters during the study period. CONCLUSIONS: No benefit was seen from a prolonged infusion of dopexamine in this group of critically ill patients in terms of GIT absorption and permeability, creatinine clearance or organ dysfunction.