Dopamine administration in oliguria and oliguric renal failure

The benefit of low-dose dopamine during vigorous diuresis for congestive heart failure associated with renal insufficiency: does it protect renal function?

BACKGROUND

Low-dose dopamine, a renal vasodilator, has been used empirically to improve renal function or outcome in critically ill patients with oliguria or acute renal failure.

HYPOTHESIS

This study was designed to investigate the efficacy of low-dose dopamine (2 micrograms/kg/min) as a renal-protective agent during vigorous diuresis for congestive heart failure (CHF) associated with mild or moderate renal insufficiency.

METHODS

Of 20 study patients (mean age 74.3 +/- 15 years) with severe CHF, 10 (Group A) were randomized to a treatment strategy of intravenous bumetanide (1 mg b.i.d.) alone and another 10 (Group B) to low-dose dopamine and a similar diuretic regimen for a duration of 5 days or less if clinical edema remitted.

RESULTS

Group B patients showed a significant improvement in renal function and urinary output: serum blood urea nitrogen 48.9 +/- 10.3 to 32.1 +/- 14.4 mg/dl (p < 0.05); serum creatinine 1.97 +/- 0.24 to 1.49 +/- 0.39 mg/dl (p < 0.05); creatinine clearance 35.6 +/- 11.6 to 48.8 +/- 12.3 ml/min (p < 0.05); and indexed urinary output 0.56 +/- 0.16 to 2.02 +/- 0.72 ml/kg/h (p < 0.05). Group A patients showed a significant increase in urinary output but nonsignificant renal functional deterioration.

CONCLUSION

The renal-protective effect of low-dose dopamine in the setting of CHF and vigorous diuresis is supported by this study.

Kidney dysfunction in the postoperative period

The development of perioperative acute renal failure is associated with a high incidence of morbidity and mortality. Although this incidence varies with different surgical procedures and with the definition used for renal failure, we now understand better the aetiology of the underlying problem. However, successful strategies to provide renal protection or strategies for 'rescue therapy' are either lacking, unsubstantiated by randomized clinical trials, or show no significant efficacy. The present review considers the physiology and pharmacology of the kidney; the characterization of tests of renal function; the cause of postoperative renal dysfunction; what is presently available for its prevention and treatment; and the effect of postoperative renal impairment on patient outcome.

Vasoactive drugs and the kidney

Protection of renal function and prevention of acute renal failure (ARF) are important goals of resuscitation in critically ill patients. Beyond fluid resuscitation and avoidance of nephrotoxins, little is known about how such prevention can be achieved. Vasoactive drugs are often administered to improve either cardiac output or mean arterial pressure in the hope that renal blood flow will also be improved and, thereby, renal protection achieved. Some of these drugs (especially low-dose dopamine) have even been proposed to have a specific beneficial effect on renal blood flow. However, when all studies dealing with vasoactive drugs and their effects on the kidney are reviewed, it is clear that none have been demonstrated to achieve clinically important benefits in terms of renal protection. It is also clear that, with the exception of low-dose dopamine, there have been no randomized controlled trials of sufficient statistical power to detect differences in clinically meaningful outcomes. In the absence of such data, all that is available is based on limited physiological gains (changes in renal blood flow or urine output) with one or another drug in one or another subpopulation of patients. Furthermore, given our lack of understanding of the pathogenesis of ARF, it is unclear whether haemodynamic manipulation is an appropriate avenue to achieve renal protection. There is a great need for large randomized controlled trials to test the clinical, instead of physiological, effects of vasoactive drugs in critical illness.

Understanding renal dose dopamine

Low-dose dopamine is a widely administered drug used often in critical care settings to prevent or treat patients with low urinary output. There are new data to support that low-dose dopamine may have side effects and not always increase renal perfusion to the kidneys. This article is a review of the current use of low-dose dopamine, the role of dopamine in the kidneys, and the potential risks of infusing this drug to patients.

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.

Acute renal failure and dialysis in the chronically critically ill patient

Acute renal failure is a common clinical problem in the intensive care unit (ICU) and is associated with significant morbidity and mortality. There is no "magic bullet" to prevent acute renal failure or to modify the clinical course of established renal failure. The approach to therapy is directed to the early initiation of dialysis therapy. Continuous dialysis therapy is becoming the preferred form of dialysis in the ICU.

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.

Intraoperative management of renal function in the surgical patient at risk. Focus on aortic surgery

Although the search for effective methods of renal prophylaxis during aortic surgery spans many decades, definitive answers are scarce. The literature is voluminous, yet the amount of work clearly relevant to the specific clinical situation of perioperative prophylaxis is small. Given the significant morbidity and subsequent mortality involved with perioperative ARF, it is difficult to sit back and do nothing when pharmacologic agents empirically are believed to possibly benefit the patient. Care must be taken to apply data from different clinical scenarios in the literature to the situation at hand. Drugs felt to be innocuous, even in low doses, may be insidiously counterproductive or damaging if they are not managed properly. Maintaining an adequate preload and stable hemodynamics seems to be the most logical universal approach at this time. Furosemide treatment without maintaining an adequate volume status once diuresis commences may be detrimental, which is true with the diuretic effects induced by mannitol or dopamine. The tachycardia resulting from a relative hypovolemia and from the beta effects of dopamine can cause myocardial ischemia from increased oxygen demand. Low urine output does not portend a negative outcome in the face of an adequate intravascular volume any more than an induced diuresis prevents renal injury. Currently, minimization of renal ischemia and maintenance of an adequate intravascular volume and renal hemodynamics are the keys to optimizing renal outcome during aortic surgery. Other maneuvers are not definitive and should be cautiously undertaken.

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.

Prolonged low-dose dopamine infusion induces a transient improvement in renal function in hemodynamically stable, critically ill patients: a single-blind, prospective, controlled study

OBJECTIVE

To evaluate the length of the effects of long-term (48 hrs), low-dose dopamine infusion on both renal function and systemic hemodynamic variables in stable nonoliguric critically ill patients.

DESIGN

Prospective, single-blind, controlled clinical study.

SETTING

University hospital, 19-bed multidisciplinary intensive care unit.

PATIENTS

Eight hemodynamically stable, critically ill patients with a mild nonoliguric renal impairment (creatinine clearance between 30 and 80 mL/min).

INTERVENTIONS

Each patient consecutively received 4 hrs of placebo, followed by a 3 microg/kg/min dopamine infusion during 48 hrs, then a new 4-hr placebo period. We measured cardiac output and other hemodynamic variables by using a pulmonary artery catheter. The bladder was emptied to determine urine volume and to collect urine samples. Measurements were performed at six times: after the initial control of 4 hrs of placebo (C1); after 4 hrs (H4), 8 hrs (H8), 24 hrs (H24), and 48 hrs (H48) of dopamine infusion; and after the second control of 4 hrs of placebo (C2).

MEASUREMENTS AND MAIN RESULTS

We saw no significant change in systemic hemodynamic variables with dopamine at all times of infusion. Diuresis, creatinine clearance, and the fractional excretion of sodium (FENa) at C1 and C2 were not different. Urine flow, creatinine clearance, and FENa increased significantly 4 hrs after starting dopamine (for all these changes, p < .01 vs. C1 and C2). The maximum changes were obtained at H8, with an increase of 50% for diuresis, 37% for creatinine clearance, and 85% for FENa (for all these changes, p < .01 vs. C1 and C2). But these effects waned progressively from H24, and both creatinine clearance and FENa at H48 did not differ from control values.

CONCLUSIONS

In stable critically ill patients, preventive low-dose dopamine increased creatinine clearance, diuresis, and the fractional excretion of sodium without concomitant hemodynamic change. These effects reached a maximum during 8 hrs of dopamine infusion. But despite a slight persistent increase in diuresis, improvement in creatinine clearance and FENa disappeared after 48 hrs. According to these data, it is likely that tolerance develops to dopamine-receptor agonists in critically ill patients at risk of developing acute renal failure.

Comparison of the renal effects of low to high doses of dopamine and dobutamine in critically ill patients: a single-blind randomized study

OBJECTIVE

The renal effects of dopamine in critically ill patients remain controversial. Low-dose dobutamine has been reported to improve renal function. We compared the effects of various doses of dopamine and dobutamine on renal function in critically ill patients.

DESIGN

Prospective, single-blind, randomized study.

SETTING

University hospital, 19-bed multidisciplinary intensive care unit.

PATIENTS

Twelve hemodynamically stable patients with mild nonoliguric renal impairment.

INTERVENTIONS

Each patient randomly received four different doses of dopamine and dobutamine (placebo, 3, 7, and 12 microg/kg/min). Each infusion lasted for 4 hrs. Cardiac output and systemic hemodynamic variables were measured using a pulmonary arterial catheter at the beginning (HO) and the end (H4) of each infusion. The bladder was emptied at HO and H4 to determine urine volume and to collect samples.

MEASUREMENTS AND MAIN RESULTS

The cardiac index increased significantly with both dopamine and dobutamine (p < .001). Mean arterial pressure (MAP) increased, with the maximum effect of 20% seen with 12-microg/kg/min dopamine infusion (p < .01). No change in MAP was seen with dobutamine. Dobutamine infusions did not change any renal variables. Conversely, all dopamine infusions significantly increased diuresis, creatinine clearance, and the fractional excretion of sodium (p < .01). Creatinine clearance increased from 61+/-16.9 (SD) mL/min to a maximum of 85.7+/-30 mL/min at the 7-microg/kg/min dose; fractional excretion of sodium increased from 0.26%+/-0.28% to a maximum of 0.62%+/-0.51% at the 12-microg/kg/min dose (p < .01). During dopamine infusions, there was a significant relationship between MAP and creatinine clearance (p = .018).

CONCLUSIONS

At all doses studied, 4-hr infusions of dopamine significantly increased creatinine clearance, diuresis, and the fractional excretion of sodium in stable critically ill patients. Conversely, dobutamine did not modify these variables. Although the level of MAP might partially contribute to the improvement in renal variables, it is more likely that the activation of renal dopamine receptors played a prominent role.

Lack of renoprotective effects of dopamine and furosemide during cardiac surgery

Because development of acute renal failure is one of the most potent predictors of outcome in cardiac surgery patients, the prevention of renal dysfunction is of utmost importance in perioperative care. In a double-blind randomized controlled trial, the effectiveness of dopamine or furosemide in prevention of renal impairment after cardiac surgery was evaluated. A total of 126 patients with preoperatively normal renal function undergoing elective cardiac surgery received a continuous infusion of either "renal-dose" dopamine (2 microg/kg per min) (group D), furosemide (0.5 microg/kg per min) (group F), or isotonic sodium chloride as placebo (group P), starting at the beginning of surgery and continuing for 48 h or until discharge from the intensive care unit, whichever came first. Renal function parameters and the maximal increase of serum creatinine above baseline value within 48 h (deltaCrea(max)) were determined. The increase in plasma creatinine was twice as high in group F as in groups D and P (P < 0.01). Acute renal injury (defined as deltaCreamax) >0.5 mg/dl) occurred more frequently in group F (six of 41 patients) than in group D (one of 42) and group P (zero of 40) (P < 0.01). (The difference between group D and group P was not significant.) Creatinine clearance was lower in group F (P < 0.05). Two patients in group F required renal replacement therapy. The mean volume of infused fluids, blood urea nitrogen, serum sodium, serum potassium, and osmolar- and free-water clearance was similar in all groups. It was shown that continuous infusion of dopamine for renal protection was ineffective and was not superior to placebo in preventing postoperative dysfunction after cardiac surgery. In contrast, continuous infusion of furosemide was associated with the highest rate of renal impairment. Thus, renaldose dopamine is ineffective and furosemide is even detrimental in the protection of renal dysfunction after cardiac surgery.

Can the use of low-dose dopamine for treatment of acute renal failure be justified?

The use of dopamine for the prevention and treatment of acute renal failure is widespread. Its use is based on physiology suggesting selective renal vasodilation when it is infused at low dose. This article reviews the available data on the clinical use of dopamine. When used to prevent acute renal failure in high-risk treatments there is no evidence of benefit of dopamine but, given the low incidence of significant renal failure, the studies are underpowered. In treatment of acute renal failure, the quality of the data is poor. Only in one small randomised trial of moderate acute renal failure in patients with malaria was a clinically significant benefit of dopamine shown. The rest of the data, in the form of case series, showed either no benefit of dopamine or small benefits of little clinical significance. Again, these studies are of insufficient power for conclusions to be drawn as to the overall benefits and risks. We conclude that benefits of dopamine use cannot be ruled out by currently available data but its use cannot be advised until trials examining clinically important endpoints in large numbers of patients have been performed.

Low-Dose Dopamine in Coronary Artery Bypass Patients with Preoperative Renal Dysfunction

Fifty-two patients undergoing coronary artery bypass surgery with preoperative renal dysfunction were studied to evaluate the effects of low-dose dopamine on renal function during the postoperative period. Patients were randomly assigned to the dopamine-treated group or an untreated control group. The treatment period was 24 hours commencing on induction of anesthesia. Serum creatinine levels were followed up for 6 days postoperatively. The degree of preoperative renal dysfunction was higher in the dopamine group but the pattern of change in the creatinine levels was similar in both groups, with an initial fall and a rise to maximum levels at 48 to 72 hours postoperatively, followed by a fall on day 6. We could not demonstrate any beneficial effect of low-dose dopamine in patients with preoperative renal dysfunction undergoing coronary artery bypass surgery.

Dopamine depresses minute ventilation in patients with heart failure

BACKGROUND

Low-dose dopamine is frequently used in patients in the intensive care setting. Dopamine may inhibit chemoreceptor afferents and hence decrease chemoreflex sensitivity to hypoxia.

METHODS AND RESULTS

In a double-blind, randomized, crossover study, we determined the effects of dopamine (5 microg x kg(-1) x min(-1)) and placebo infusion on oxygen saturation, minute ventilation, and sympathetic nerve activity during normoxia and 5 minutes of hypoxia in 10 normal young subjects. We further investigated the effects of dopamine and placebo on minute ventilation during normoxic breathing in 8 patients with severe heart failure and in 8 age-matched control subjects. Dopamine did not decrease minute ventilation during normoxia in normal subjects. During hypoxia, minute ventilation was 12.9+/-1.3 L/min on dopamine and 15.8+/-1.5 L/min on placebo (P<0.0001). Oxygen saturation during hypoxia was lower with dopamine (78+/-3%) than placebo (84+/-2%; P<0.0001). Sympathetic nerve activity during hypoxia was not enhanced with dopamine despite the lower O2 saturation. Subjects were able to maintain a voluntary apnea to a lower oxygen saturation on dopamine than on placebo (P<0.05). In heart failure patients breathing room air, but not in age-matched control subjects, dopamine decreased minute ventilation despite decreased oxygen saturation and increased PETCO2 during dopamine (all P< or =0.02).

CONCLUSIONS

Dopamine inhibits chemoreflex responses during hypoxic breathing in normal humans, preferentially affecting the ventilatory response more than the sympathetic response. Dopamine also depresses ventilation in normoxic heart failure patients breathing room air. Ventilatory inhibition by low-dose dopamine may adversely influence outcome in hypoxic patients, especially in patients with heart failure.

Low dose dopamine in postpartum pre-eclamptic women with oliguria: a double-blind, placebo controlled, randomised trial

OBJECTIVE

To assess the effect of low dose dopamine on the urine output in postpartum pre-eclamptic or eclamptic women with oliguria.

DESIGN

A double blind, randomised controlled study.

SETTING

The high care area of the labour ward in a teaching hospital.

SAMPLE

Forty postpartum pre-eclamptic women with oliguria, defined as < 30 mL/hour, who have not responded to a 300 mL crystalloid fluid challenge.

INTERVENTION

Dopamine was infused at a rate of 1 to 5 microg/kg per minute, or sterile water was given as placebo in the same dilution.

MAIN OUTCOME MEASURE

Urine output, blood pressure and pulse was measured for six hours before and for six hours after the intervention.

RESULTS

Women who received dopamine (344 mL over 6 hours) showed a clinically and statistically significant (P = 0.0014, Mann-Whitney U test) higher median urine output compared with those receiving placebo (135 mL over 6 hours) for the duration of therapy. The respective 95% confidence intervals were 212.3 to 712.7 mL compared with 73.8 to 244.7 mL. No differences in blood pressure or pulse were found between the two groups.

CONCLUSIONS

The use of low dose dopamine in a labour setting improved urine output in postpartum pre-eclamptic women with oliguria who had not responded to a single fluid challenge without a detrimental effect on the blood pressure or pulse.

The use of diuretics and dopamine in acute renal failure: a systematic review of the evidence

OBJECTIVE: To evaluate the impact of diuretics and dopamine for both the prevention and treatment of renal dysfunction in the acute care setting. STUDY IDENTIFICATION AND SELECTION: Studies were identified via MEDLINE, and through bibliographies of primary and review articles. Articles were then screened by the author for studies addressing the use of diuretics or dopamine in the prevention and/or treatment of renal dysfunction. DATA ABSTRACTION AND LITERATURE APPRAISAL: From individual studies, data were abstracted regarding design features, population, intervention and outcomes. Studies were graded by levels according to their design. RESULTS: A total of 10 studies using diuretics and 30 involving dopamine were identified. Level I evidence exists against the use of diuretics for radiocontrast-induced acute tubular necrosis, and loop diuretics given after vascular surgery. There is level II evidence that diuretics do not improve outcome in patients with established acute renal failure. Level II evidence also exists against the use of dopamine in the prevention of acute tubular necrosis in multiple subsets of patients. CONCLUSIONS: Routine use of diuretics or dopamine for the prevention of acute renal failure cannot be justified on the basis of available evidence.

Dopaminergic receptor-mediated effects in the mesenteric vasculature and renal vasculature of the chronically instrumented newborn piglet

OBJECTIVE

To determine the effects of stimulation of vascular dopaminergic receptor subtype 1 (dopamine-1) receptors in the renal and mesenteric vascular beds of a neonatal model.

DESIGN

Prospective, unblinded, dose-response evaluation in an awake animal.

SETTING

University research laboratory.

SUBJECTS

Thirty newborn piglets, obtained and instrumented at 1 to 3 days of age and studied 48 hrs later.

INTERVENTIONS

Animals were chronically instrumented with transit time ultrasound flow probes around the left renal and superior mesenteric arteries. They were then intravenously infused with either dopamine (2 to 32 micrograms/kg/min) or fenoldopam (1 to 100 micrograms/kg/min), which is a selective agonist of the dopamine-1 receptor.

MEASUREMENTS AND MAIN RESULTS

Blood pressure was only significantly increased by the highest infusion rate of dopamine (32 micrograms/kg/min), from a mean of 78 mm Hg at baseline to 87 mm Hg. Mesenteric and renal vascular resistances were unchanged by dopamine at any dose. Dopamine at 32 micrograms/kg/min decreased renal blood flow by 16.6 +/- 19.6 (SD) % and increased renal vascular resistance by 39.6 +/- 41.1% (p < .05). Mesenteric blood flow increased by 15% at 32 micrograms/kg/min (p < .05) but mesenteric vascular resistance was not affected by dopamine. Fenoldopam reduced blood pressure at infusion rates of 5, 10, and 100 micrograms/kg/min. Fenoldopam had no effect on renal vascular resistance at any dose. Fenoldopam reduced mesenteric vascular resistance at 5 micrograms/kg/min and at all higher doses.

CONCLUSIONS

These data demonstrate the absence of dopaminergic receptor-mediated vasodilation in the porcine neonatal renal vascular bed. In the mesenteric artery, dopamine-1 receptor-mediated vasodilation may be obtained. Dopamine itself, probably because of stimulation of other receptors, causes renal artery vasoconstriction and does not increase superior mesenteric artery blood flow.

Is renal dose dopamine protective or therapeutic? No

This article argues that dopamine infused in low doses has not been shown to avert the onset of or ameliorate the course of acute renal failure in critically ill patients. The inotropic and diuretic effects of dopamine are discussed, and its adverse effects are described. An attempt is made to offer an evidence-based role for low-dose dopamine, namely as a diuretic in ventilated, euvolemic patients, resistant to conventional diuretic therapy.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Renal effects of low-dose dopamine in patients with sepsis syndrome or septic shock treated with catecholamines

OBJECTIVE

To evaluate the renal effects of low-dose dopamine in patients with sepsis syndrome or septic shock treated with catecholamines.

DESIGN

Prospective, clinical study using sequential periods.

SETTING

A 12-bed surgical intensive care unit in a university hospital.

PATIENTS

14 patients with sepsis syndrome and 15 patients with septic shock treated with exogenous catecholamines were studied. They had no diuretic treatment.

INTERVENTION

Two periods of 2 h each with and without 2 micrograms.kg-1.min-1 of dopamine infusion. Hemodynamic and renal data were obtained at the end of each period. Measurements were repeated after 48 h of dopamine infusion in patients with sepsis syndrome. All data were evaluated by the Wilcoxon rank test.

MEASUREMENTS AND RESULTS

In patients with sepsis syndrome, diuresis and creatinine clearance increased significantly by 100% and 60%, respectively, during low-dose dopamine infusion without any change in systemic hemodynamics. The renal response to dopamine decreased significantly after 48 h of dopamine infusion (P < 0.01). In patients with septic shock treated with catecholamines, no variation of either systemic hemodynamics or renal function was noted during low-dose dopamine infusion.

CONCLUSION

The renal effects of low-dose dopamine in patients with sepsis syndrome decrease with time. No renal effect of low-dose dopamine was observed in patients with septic shock treated with catecholamines. These findings suggest a desensitization of renal dopaminergic receptors.

Renal dysfunction in obstructive jaundice

The association between renal dysfunction and obstructive jaundice is well established. Despite a substantial number of clinical reviews and prospective studies, the exact incidence and extent of the problem has not been determined accurately. Various pathogenic mechanisms and therapeutic strategies have been proposed but renal dysfunction remains a persistent problem in hepatobiliary practice. The intention of this review is to determine the current extent of the problem, outline the proposed pathophysiological mechanisms and assess the current therapeutic options.

Prospective study of postoperative renal function in obstructive jaundice and the effect of perioperative dopamine

A prospective study was undertaken to assess postoperative renal dysfunction in patients with obstructive jaundice and to determine the effectiveness of dopamine in reducing its incidence. A total of 23 patients undergoing surgical relief of obstructive jaundice (serum bilirubin level above 100 mumol l-1) were randomized into two groups. Those in the control group (n = 10) received 3 litres 5 per cent dextrose intravenously during the 24 h before surgery plus a bolus of intravenous frusemide 1 mg kg-1 at induction of anaesthesia. The second group (n = 13) received a similar fluid and frusemide regimen plus an infusion of dopamine 3 micrograms kg-1 min-1 starting at induction of anaesthesia and continuing for 48 h after surgery. Postoperative oliguria occurred in two of the ten patients in the control group and in three of the 13 given dopamine (P = 0.74). No patient developed acute renal failure. There was no significant difference in mean levels of serum bilirubin, urea and creatinine, creatinine clearance and 24-h urinary output, on the day before and on days 1-5 after operation, between the two groups. It is concluded that, with careful preoperative resuscitation and control of fluid and electrolyte balance, the incidence of postoperative renal dysfunction in patients with obstructive jaundice is not as high as in some previous studies and is unaltered by administration of perioperative low-dose dopamine.

Diuretics in acute renal failure

Studies on the ability of loop diuretics, mannitol, dopamine, and atrial natriuretic peptide to ameliorate or reverse human acute renal failure are reviewed. A precise role for diuretic therapy in this clinical setting has not been established. Most reports are retrospective, poorly controlled, or simply anecdotal. There is a need for prospective, randomly allocated studies on adequate numbers of patients. While the use of diuretic agents may improve fluid balance management in patients at risk of developing acute renal failure, maintenance of adequate effective circulating volume and oxygen delivery probably provides the best-proven protection.

Enhanced intravenous urography in renal trauma with low-dose dopamine

Intravenous pyelography is the standard first-line investigation for suspected renal trauma. A faint, and/or delayed visualization, or nonvisualization of the damaged renal unit is not uncommon. Low-dose dopamine (3 micrograms/kg/min) increases renal blood flow without deleterious side effects. An experimental rat model was developed to evaluate the effects of low-dose dopamine on intravenous pyelograms in animals with unilateral renal trauma. A consistent and significant improvement in the visualization of the injured kidney was noted in the dopamine-treated animals compared with controls that received equivalent volumes of normal saline.

Dopamine and renal salvage in the critically ill patient

Dopamine is a catecholamine used widely in critically ill patients and those undergoing major surgery, often as a 'renal protective' agent. Direct renal vasodilatation with 'low-dose' dopamine is the widely accepted basis for its use--hence the term 'renal dose' dopamine. However, recent evidence has revealed that the renal effects of this agent are far more complex. Moreover, some of these effects may be undesirable in the 'at-risk' kidney. The increased renal blood flow (RBF) of dopamine may be largely attributable to its inotropic (myocardial) action, even with low doses (i.e. less than 5 micrograms/kg/min). Similar increases in RBF can also be demonstrated with other (non-dopaminergic) inotropes. The early evidence for direct renal vasodilatation in response to dopamine has been brought into question by more recent research. The diuresis and natriuresis commonly seen following dopamine administration is now known to be due to a direct renal tubular (or 'diuretic') action. Furthermore, increasing knowledge regarding the pathophysiology of acute (ischaemic) renal failure, including RBF and the concept of 'oxygen supply and demand' in relation to tubular function, suggests that dopamine may mask important signs of renal ischaemia. Whether or not dopamine is truly beneficial to renal function currently remains unanswered. As it stands however, there is sufficient evidence to question its routine use in the setting of renal dysfunction in the critically ill patient.

A comparison of dopexamine and dopamine to prevent renal impairment in patients undergoing orthotopic liver transplantation

The efficacy of low-dose dopamine as a renal protective agent was compared with that of dopexamine in patients who underwent orthotopic liver transplantation. Twelve patients who received a continuous infusion of dopexamine (1-3 micrograms/kg/minute) were matched for age, diagnosis, pre-operative creatinine clearance and blood loss with 12 patients who received a low-dose infusion of dopamine (2 micrograms/kg/minute). The catecholamine infusion was started after induction of anaesthesia and continued for 48 hours after surgery. Patients in the dopexamine group had less evidence of renal impairment and failure than those in the dopamine group during 7 days after the operation, although the differences between groups did not achieve statistical significance. Similarly there were no significant differences between the two groups in peri-operative urine output, urine/plasma osmolality ratio or creatine clearance. Dopexamine is at least as effective as dopamine for renal protection in patients who undergo liver transplantation.

Dopexamine: studies in the general intensive care unit and after liver transplantation

1. It has been suggested that the use of dopaminergic agents in the critically ill patient may reduce the incidence of renal failure and hence mortality. 2. Dopexamine hydrochloride is a new synthetic catecholamine. Like dopamine, it stimulates dopaminergic receptors. It also stimulates beta 2-adrenoceptors. Unlike dopamine, dopexamine has minimal effect at beta 1-adrenoceptors and no alpha-adrenoceptor activity. 3. Stimulation of renal dopaminergic and beta 2-adrenoceptors independently results in dilation of the renal vasculature. A natriuresis and diuresis is also promoted by dopaminergic stimulation. 4. A comparison between the administration of low dose dopamine and dopexamine in patients undergoing orthotopic liver transplantation resulted in less renal impairment and failure in the dopexamine group, although this did not achieve statistical significance. 5. Dopexamine elimination is reduced in the absence of hepatic function. 6. A patient with terminal liver failure was treated with dopexamine and although oxygen delivery was unchanged, oxygen consumption doubled. This suggests that dopexamine affects other organs as well as the kidneys.

Do we need a dopaminergic agent in the management of the critically ill?

1. The stimulation of dopaminergic receptors is in principle attractive to increase urine and sodium excretion in patients with compromised renal blood flow. 2. However, a protective role of dopaminergic agents on renal function has not been well established. Most of the trials have been performed with dopamine, a substance which can have vasoconstrictive properties, even at relatively low doses in the critically ill patient. 3. Perhaps other dopaminergic agents without alpha-adrenergic effects such as dopexamine could be more advantageous. Randomized, prospective, controlled clinical studies should be performed to test the hypothesis that dopaminergic agents can reduce the incidence of acute tubular necrosis in critically ill patients.

Low-dose dopamine during cardiopulmonary bypass in patients with renal dysfunction

Thirty-six patients with preoperative renal dysfunction were studied to evaluate the effects of dopamine (D) and dopamine-nitroprusside (DN) on renal function during cardiopulmonary bypass (CPB). No differences from the control group (C) were found in creatinine clearance, fractional sodium excretion, osmolarity and free-water clearance. Sodium output/intake ratio during CPB was higher in group D than in groups C and DN (P less than 0.05); water output/intake ratio was higher in group D than in group C (P less than 0.05). Urine lysozime levels and alpha-glycosidase/creatinine ratios increased similarly in the three groups, suggesting ischemic tubular cell damage. No patients showed acute postoperative renal failure or a worsening of their renal dysfunction. The data suggest an increased water and sodium excretion during CPB with a dopamine infusion, possibly resulting from a renal vasodilator effect that was abolished by simultaneous nitroprusside administration.

Pathophysiology and prevention of acute renal failure: the role of the anaesthetist

Ischaemic renal tubular damage in the perioperative period can lead to acute renal failure (ARF) with a very high mortality rate (60-75 per cent). Recent research suggests that this tubular injury is caused by an imbalance of the oxygen supply and demand of medullary thick ascending limb (mTAL) tubular cells. High oxygen demand is secondary to active reabsorption of solute which is increased in states of intravascular volume depletion. The restricted supply of oxygen is secondary to the organization of blood flow to the inner medulla. Because the vasa recta loop into the inner medulla and a countercurrent exchange process for oxygen is established, the oxygen tension in this area may normally be as low as 10-20 mmHg. In hypoperfusion states, mTAL injury occurs and is exacerbated by intravascular volume depletion, hypoxaemia and endothelial cell swelling which reduces perfusion of these vulnerable and metabolically active mTAL cells. The anaesthetist must prevent or attenuate postoperative renal dysfunction by identifying high-risk patients preoperatively, optimizing intravascular volume status and cardiac output in the perioperative period, as well as responding appropriately to hypoperfusion states. Therapeutic implications relate to this pathophysiological sequence and several physiological and pharmacological considerations are discussed.