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OBJECTIVE The lithium indicator dilution technique has been shown to measure cardiac output (CO) accurately by using central venous injection of lithium chloride (Li-CCO). This study aimed to compare the measurement of CO by using peripheral venous administration of lithium chloride (Li-PCO) with Li-CCO. DESIGN Prospective, observational human study. SETTING Surgical intensive care unit. PATIENTS Thirty-one patients were studied after major surgery. All patients had arterial, central, and peripheral venous catheters. A total of 24 patients had pulmonary artery catheters. MEASUREMENTS Serial measurements of Li-CCO and Li-PCO were made during hemodynamically stable conditions. CO was also measured using thermodilution (TDCO) when a pulmonary artery catheter was present. Data were analyzed by linear regression, the generalized estimating equation, and the comparison method described by Bland and Altman. MAIN RESULTS There were 93 Li-CCOs, 93 Li-PCOs, and 216 TDCOs recorded. The ranges of COs were similar: Li-CCO, 2.36-11.52 L/min (mean, 5.22 L/min; n = 31); Li-PCO, 1.63-9.99 L/min (mean, 5.22 L/min; n = 31), and TDCO, 3.28-10.4 L/min (mean, 5.75 L/min; n = 24). There was good linear correlation between Li-CCO and Li-PCO (R2 =.845). The mean difference for Li-CCO-Li-PCO was very small and insignificant (p =.97), and the limits of agreement were acceptable (mean difference +/- sd, 0.0005 +/- 0.64 L/min). The mean difference for Li-CCO-Li-PCO was smaller if the peripheral injection site was proximal rather than distal to the wrist (p =.053). Li-PCO and Li-CCO values were lower than simultaneously obtained TDCO measurements (Li-PCO-TDCO, -0.538 +/- 0.95 L/min, p =.003; Li-CCO-TDCO, -0.526 +/- 0.67 L/min, p =.0001). CONCLUSIONS Li-PCO gives a measurement that agrees well with Li-CCO. Accuracy of Li-PCO is probably improved if a proximal arm vein is used. Li-PCO provides accurate measurements of CO without the risks of pulmonary artery or central venous catheterization.

Objective To describe the goals of sedative use in the intensive care unit and review the pharmacology of commonly used sedative drugs as well as to review pertinent publications in the literature concerning the comparative pharmacology of these drugs, with emphasis on outcomes related to sedation and comparative pharmacoeconomics. Data sources Publications in the scientific literature. Data extraction Computer search of the literature with selection of representative articles. Synthesis Proper choice and use of sedative drugs is based on knowledge of the pharmacology of commonly used agents and is an essential component of caring for patients in the intensive care unit. The large variability in pharmacokinetics and pharmacodynamics in the critically ill make it difficult to directly compare agents. Midazolam provides rapid and reliable amnesia, even when administered for low levels of sedation. Propofol may be useful when deeper levels of sedation and more rapid awakening are required. Lorazepam can be used for long-term sedation in more stable patients if rapidity of effect is not required. Further investigation in assessment of depth of sedation in the critically ill is needed. Continued study of costs, side effects, and appropriate dosing strategies of all sedative agents is needed to answer questions not sufficiently addressed in the current literature. Conclusion An individualized approach to sedation based on knowledge of drug pharmacology is needed because of confounding variables including concurrent patient illness, depth of sedation, and concomitant use of analgesic agents. (Crit Care Med 2000; 28:854-866)