Use of inotropic agents in critical illness

Drug utilization pattern in the intensive care unit of a tertiary care hospital

The authors studied the factors affecting drug use pattern, cost of therapy, and the association between the pattern of drug use and survival as well as the duration of stay in a prospective, observational study in an intensive care unit between February and May 2005. Data were collected regarding drugs used, severity of the disease, and their outcome. The mean +/- SD of the Acute Physiology and Chronic Health Evaluation (APACHE III) and Glasgow Coma Scale (GCS) scores of 84 patients were 52.2 +/- 19.4 and 7.5 +/- 2.4, respectively. Although the mean number of drugs at the time of admission to the intensive care unit was 5.3, it increased to 12.9 on the first day and 22.2 during the entire stay. More than 50% of the average expenditure on drugs and nutrition was accounted by antibiotics. Requirement of insulin or inotropes signified an adverse outcome on mortality (odds ratios of 3.43 and 8.44, respectively). In conclusion, there is a tremendous impact of antibiotic use on the cost of therapy in the intensive care unit. The requirement of certain drugs such as insulin and inotropes is of prognostic significance.

Different response of oxygen consumption and cardiac output to various endogenous and synthetic catecholamines in awake dogs

OBJECTIVE

To determine whether catecholamines with different adrenergic receptor affinities are characterized by individual relationships between cardiac output (Q) and oxygen consumption (VO2).

DESIGN

Comparison of the dose-effect relationships and Q/VO2 relationships of four different catecholamines in the same awake dogs.

SETTING

University research department of experimental anesthesiology.

SUBJECTS

Ten trained, healthy dogs in the basal metabolic state with chronically implanted ultrasonic flow transducers around the pulmonary artery for the continuous measurement of cardiac output.

INTERVENTIONS

Increasing doses of norepinephrine, epinephrine, dobutamine, or dopexamine were infused in a randomly varied sequence on separate days until VO2 and Q reached a maximum.

MEASUREMENTS AND MAIN RESULTS

VO2 was measured by indirect calorimetry, and Q was measured via the pulmonary artery by ultrasonic flowmetry. In healthy dogs, catecholamines increased both VO2 and Q in a dose-dependent manner until a plateau was reached when VO2 had doubled and Q had quadrupled compared with baseline conditions. Regardless of the catecholamine, the resulting Q/VO2 relationships were linear up to the maximal effects, but their slopes (s) differed significantly between agents (p < .05, paired sign test) and increased approximately three-fold in the order norepinephrine (s = 34), epinephrine (s = 54), dobutamine (s = 86), and dopexamine (s = 105). Except for norepinephrine, the catecholamines also increased oxygen delivery more than VO2, so that O2 extraction decreased to 40% below baseline.

CONCLUSIONS

Catecholamines are characterized by linear Q/VO2 relationships with drug-specific slopes. All agents (except norepinephrine) increased oxygen delivery more than oxygen demand. For the practice of catecholamine therapy, our experiments imply that synthetic agents such as dobutamine and particularly dopexamine may be preferred in the treatment of low cardiac output states because they increase Q with the least metabolic effects.

Sepsis and septic shock. II. Treatment

Mortality from septic shock is considerable despite the advantages of cardiovascular support and antibiotic therapy. This article reviews current therapy of septic shock including immunotherapy and further possibilities of septic shock treatment. The role of cytokines, their inhibitors and antibodies to endotoxin is mentioned. Although these treatments hold much promise for the future, careful evaluation of both the benefits and complications of therapy is needed before widespread clinical use can be recommended.

Inotropic support of the critically ill patient. A review of the agents

Intensive care patients often require inotropic support to stabilise circulation and to optimise oxygen supply. In this context, the catecholamines norepinephrine (noradrenaline), epinephrine (adrenaline), dopamine and dobutamine are still the mainstay of therapy. They provide, to different extents, a variety of adrenoceptor-mediated actions comprising vasoconstriction (via alpha-receptors) as well as vasodilatation (via beta 1-receptors), and an increase in cardiac output by enhancing inotropy and heart rate (again via beta 1-receptors). Because of their favourable pharmacokinetic profile (plasma half-lives of about 2 minutes) their actions can easily be controlled. Combinations of different catecholamines with each other or with other drugs such as phosphodiesterase inhibitors or nitrates lead to a broad spectrum of possible haemodynamic actions. However, the use of catecholamines is limited by side effects like tachycardia, hypertension and disturbances of organ perfusion caused by vasoconstriction. Furthermore, as a result of receptor downregulation during long term therapy, the efficacy of catecholamine treatment decreases. These shortfalls stimulated the search for alternatives to catecholamine treatment. Among these, phosphodiesterase inhibitors (e.g. enoximone and amrinone) appear to be the most promising drugs which have been introduced into acute clinical practice up to now. They act via inhibition of the phosphodiesterase isoenzyme III, leading to higher intracellular calcium levels by increasing cyclic adenosine monophosphate (cAMP) levels. These agents improve cardiac performance by enhancing contractility, reducing left ventricular afterload and improve diastolic relaxation. In cases of failing catecholamine therapy due to receptor downregulation, treatment with phosphodiesterase inhibitors may still be effective since their action is not receptor-mediated. Inhibition of the phosphodiesterase enzyme in vascular smooth muscle leads to vasodilatation. Therefore, in low cardiac output states combined with increased total peripheral or pulmonary vascular resistance, phosphodiesterase inhibitor therapy is particularly effective. Depending on the dosage and the speed of intravenous administration, the use of phosphodiesterase inhibitors sometimes results in pronounced decrease of blood pressure which may require vasopressor therapy. Other drugs including histamine H2-agonists are currently under investigation. Their value in the treatment of intensive care patients has still to be evaluated.