Serum aldosterone concentrations and urine output in oliguric intensive care unit patients receiving low-dose dopamine

Prevention of post-traumatic clinical capillary leak syndrome

Systemic capillary leak is an early feature of the inflammatory response to localized injury, and is proportional to the severity of the inflammatory insult. Loss of local control of inflammation leads to an exaggerated systemic inflammatory response known as systemic inflammatory response syndrome (SIRS). SIRS is associated with multiple organ failure and death when there is failure to maintain homeostasis.

Whilst the application of molecular biology and recombinant techniques have produced major advances in our understanding of the mediation of the inflammatory response, there is no agent currently available which will prevent SIRS and reduce the incidence of post-traumatic multiple organ failure. In the meantime, a more practical approach to the avoidance of SIRS and its attendant capillary leak syndrome is to attempt to reduce the deleterious effects of interstitial oedema by tailoring treatment to the rapid changes in capillary permeability.

Fluid, electrolytes and nutrition: physiological and clinical aspects

Fluid and electrolyte balance is often poorly understood and inappropriate prescribing can cause increased post-operative morbidity and mortality. The efficiency of the physiological response to a salt or water deficit, developed through evolution, contrasts with the relatively inefficient mechanism for dealing with salt excess. Saline has a Na+:Cl-of 1:1 and can produce hyperchloraemic acidosis, renal vasoconstriction and reduced glomerular filtration rate. In contrast, the more physiological Hartmann's solution with a Na+:Cl-of 1·18:1 does not cause hyperchloraemia and Na excretion following infusion is more rapid. Salt and water overload causes not only peripheral and pulmonary oedema, but may also produce splanchnic oedema, resulting in ileus or acute intestinal failure. This overload may sometimes be an inevitable consequence of resuscitation, yet it may take 3 weeks to excrete this excess. It is important to avoid unnecessary additional overload by not prescribing excessive maintenance fluids after the need for resuscitation has passed. Most patients require 2–2·5 litres water and 60–100?mmol?Na\d for maintenance in order to prevent a positive fluid balance. This requirement must not be confused with those for resuscitation of the hypovolaemic patient in whom the main aim of fluid therapy is repletion of the intravascular volume. Fluid and electrolyte balance is a vital component of the metabolic care of surgical and critically-ill patients, with important consequences for gastrointestinal function and hence nutrition. It is also of importance when prescribing artificial nutrition and should be given the same careful consideration as other nutritional and pharmacological needs.

Hemodynamics and renal function during administration of low-dose dopamine in severely ill patients

CONTEXT

Although a large number of studies have been performed regarding the renal and hemodynamic effects of the infusion of low-dose dopamine (LDD) in severely ill patients, there is still controversy on this subject.

OBJECTIVE

To evaluate the effects of dopamine (2 microg/kg/min) on systemic hemodynamics (lowest mean arterial pressure, MAP, highest heart rate, HR, central venous pressure, CVP), creatinine clearance (CLcr), diuresis and fractional sodium excretion (FENa+).

TYPE OF STUDY

A non-randomized, open, prospective clinical trial.

SETTING

An intensive care unit in a tertiary university hospital.

PARTICIPANTS

22 patients with hemodynamic stability admitted to the intensive care unit.

PROCEDURES

Patients were submitted to three two-hour periods: without dopamine (P1), with dopamine (P2) and without dopamine (P3).

MAIN MEASUREMENTS

The above mentioned variables were measured during each period. CLcr was assessed based upon the formula U x V/P, where U is urinary creatinine (mg/dl), V is diuresis in ml/min and P is serum creatinine (mg/dl). FENa+ was calculated based upon the formula: urinary sodium (mEq/l) x P/plasma sodium (mEq/l) x U) x 100. Results were presented as mean and standard deviation. The Student t test was used and results were considered significant if p was less than 0.05.

RESULTS

Twelve patients (seven males and five females) were included, with a mean age of 55.45 years. There was no significant variation in MAP, HR, CVP, CLcr or FENa+ with a dopamine dose of 2 microg/kg/min. On the other hand, diuresis significantly increased during P2, from 225.4 to 333.9 ml.

CONCLUSION

Infusion of 2 microg/kg/min of dopamine for 2 hours increases diuresis. At the doses studied, dopamine does not induce significant alterations in MAP, HR, CVP, CLcr and FENa+.

Use of dopamine in acute renal failure: a meta-analysis

OBJECTIVE

To determine whether low-dose dopamine administration reduces the incidence or severity of acute renal failure, need for dialysis, or mortality in patients with critical illness.

DATA SOURCES AND STUDY SELECTION

We performed a MEDLINE search of literature published from 1966 to 2000 for studies addressing the use of dopamine in the prevention and/or treatment of renal dysfunction.

DATA EXTRACTION

Data were abstracted regarding design characteristics, population, intervention, and outcomes. Results of individual randomized clinical trials were pooled using a fixed effects model and a Mantel-Haenszel weighted chi-square analysis.

DATA SYNTHESIS

We identified a total of 58 studies (n = 2149). Of these, outcome data were reported in 24 studies (n = 1019) and 17 of these were randomized clinical trials (n = 854). Dopamine did not prevent mortality, (relative risk, 0.90 [0.44-1.83]; p =.92), onset of acute renal failure (relative risk, 0.81 [0.55-1.19]; p =.34), or need for dialysis, (relative risk, 0.83 [0.55-1.24]; p =.42). There was sufficient statistical power to exclude any large (>50%) effect of dopamine on the risk of acute renal failure or need for dialysis.

CONCLUSIONS

The use of low-dose dopamine for the treatment or prevention of acute renal failure cannot be justified on the basis of available evidence and should be eliminated from routine clinical use.

Pharmacodynamic effects of dopamine stratified by race

The purpose of this investigation was to evaluate the effects of dopamine on heart rate (HR), systolic blood pressure (SBP), aldosterone, plasma renin activity (PRA), bradykinin, prolactin, corticotropin (ACTH), urinary output (UO), and urinary sodium (UNa) stratified by race. Sixteen healthy age- and weight-matched Caucasian and African American male subjects participated in this single-blind, three-phase study. The three phases included the following treatments and assessments: (i) 90-minute infusion of D(5)W 100 mL/h and control piggyback (control period); (ii) 90-minute infusion D(5)W 100 mL/h and 3 microg/kg/min dopamine (dopamine phase); (iii) assessments repeated 24 hours after dopamine administration (washout period). Plasma was analyzed for dopamine concentrations. Dopamine significantly increased HR and SBP across the study population. In addition, UO and UNa increased, prolactin was reversibly depressed, bradykinin and ACTH were unchanged, and aldosterone significantly rebounded on washout. With regard to race differences, SBP significantly increased in African Americans compared with Caucasians, and UNa significantly increased in Caucasians compared with African Americans. In summary, 3 microg/kg/min dopamine produced significant renal, hormonal, and hemodynamic changes in healthy men. Selected effects varied by race.

Low-dose "renal" dopamine

Low dose renal dopamine continues to be infused in patients at risk for renal dysfunction or as a therapy after acute renal failure has been established. This article reviews the impact of acute renal failure on patients and reviews the history and use of dopamine therapy for patients. A discussion of the rationale, positive and equivocal evidence, side effects, and possible clinical indications for low-dose renal dopamine therapy is included.

Is renal dose dopamine protective or therapeutic? Yes

In conclusion, dopamine has the unique ability, compared with other catecholamines, to improve renal blood flow, glomerular filtration rate, sodium excretion, and creatinine clearance, independent of its cardiac effects. In addition, low-dose dopamine can decrease renal and systemic vascular resistance, suppress aldosterone secretion, and interact with atrial natriuretic factor. Because of these clinically significant properties, dopamine has been used successfully to improve and treat acute oliguric renal failure in a variety of clinical situations as just described. In addition, there were no adverse or toxic cardiac effects, such as tachyarrhythmias or hypertension, detected with low-dose dopamine in studies reviewed for this publication. By increasing renal and mesenteric vasodilation, dopamine has been shown to be beneficial in preserving renal function in cardiac surgery, vascular surgery, liver transplantation, contrast-induced nephropathy, hypertension, and pediatric patients. A therapeutic renal effect has been observed in patients with hepatorenal syndrome or severe ovarian hyperstimulation syndrome, in patients requiring vasopressors and IABP, and in selected cases of acute oliguric renal failure and shock. Furthermore, the combination of low-dose dopamine with furosemide or prostaglandin results in enhanced renal effects. Further investigation is necessary to evaluate the important and specific therapeutic role of low-dose dopamine through prospective, randomized, double-blind studies. Until those data are available, the plethora of clinical evidence supporting the ability of low-dose dopamine to augment renal function continues to grow. For those who are skeptical, we offer the following suggestion: "The obscure we see eventually, the obvious takes a little longer"--E.R. Murrow.