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

Development of a Physiologically Based Pharmacokinetic Modelling Approach to Predict the Pharmacokinetics of Vancomycin in Critically Ill Septic Patients

BACKGROUND AND OBJECTIVES

Sepsis is characterised by an excessive release of inflammatory mediators substantially affecting body composition and physiology, which can be further affected by intensive care management. Consequently, drug pharmacokinetics can be substantially altered. This study aimed to extend a whole-body physiologically based pharmacokinetic (PBPK) model for healthy adults based on disease-related physiological changes of critically ill septic patients and to evaluate the accuracy of this PBPK model using vancomycin as a clinically relevant drug.

METHODS

The literature was searched for relevant information on physiological changes in critically ill patients with sepsis, severe sepsis and septic shock. Consolidated information was incorporated into a validated PBPK vancomycin model for healthy adults. In addition, the model was further individualised based on patient data from a study including ten septic patients treated with intravenous vancomycin. Models were evaluated comparing predicted concentrations with observed patient concentration-time data.

RESULTS

The literature-based PBPK model correctly predicted pharmacokinetic changes and observed plasma concentrations especially for the distribution phase as a result of a consideration of interstitial water accumulation. Incorporation of disease-related changes improved the model prediction from 55 to 88% within a threshold of 30% variability of predicted vs. observed concentrations. In particular, the consideration of individualised creatinine clearance data, which were highly variable in this patient population, had an influence on model performance.

CONCLUSION

PBPK modelling incorporating literature data and individual patient data is able to correctly predict vancomycin pharmacokinetics in septic patients. This study therefore provides essential key parameters for further development of PBPK models and dose optimisation strategies in critically ill patients with sepsis.

Renal perfusion in sepsis: from macro- to microcirculation

The pathogenesis of sepsis-associated acute kidney injury is complex and likely involves perfusion alterations, a dysregulated inflammatory response, and bioenergetic derangements. Although global renal hypoperfusion has been the main target of therapeutic interventions, its role in the development of renal dysfunction in sepsis is controversial. The implications of renal hypoperfusion during sepsis probably extend beyond a simple decrease in glomerular filtration pressure, and targeting microvascular perfusion deficits to maintain tubular epithelial integrity and function may be equally important. In this review, we provide an overview of macro- and microcirculatory dysfunction in experimental and clinical sepsis and discuss relationships with kidney oxygenation, metabolism, inflammation, and function.

Update on Vasopressors and Inotropes in Septic Shock

Vasopressors and inotropes are used in septic shock in patients who remain hypotensive despite adequate fluid resuscitation. The goal is to increase blood pressure to optimize perfusion to organs. Generally, goal-directed therapy to supra-normal oxygen transport variables cannot be recommended due to lack of benefit. Traditionally, vasopressors and inotropes in septic shock have been started in a step-wise fashion starting with dopamine. Recent data suggest that there may be true differences among vasopressors and inotropes on local tissue perfusion as measured by regional hemodynamic and oxygen transport. When started early in septic shock, norepinephrine decreases mortality, optimizes hemodynamic variables, and improves systemic and regional (eg, renal, gastric mucosal, splanchnic) perfusion. Epinephrine causes a greater increase in cardiac index (CI) and oxygen delivery (DO2 ) and increases gastric mucosal flow, but increases lactic acid and may not adequately preserve splanchnic circulation owing to its predominant vasoconstrictive alpha (α ) effects. Epinephrine may be particularly useful when used earlier in the course of septic shock in young patients and those who do not have any known cardiac abnormalities. Unlike epinephrine, dopamine does not preferentially increase the proportion of CI that preferentially goes to the splanchnic circulation. Dopamine is further limited because it cannot increase CI by more than 35% and is accompanied by tachycardia or tachydysrhythmias. Dopamine, as opposed to norepinephrine, may worsen splanchnic oxygen consumption (VO2 ) and oxygen extraction ratio (O2 ER). Low-dose dopamine has not been shown to consistently increase the glomerular filtration rate or prevent renal failure, and, indeed, worsens splanchnic tissue oxygen use. Routine use of concurrently administered dopamine with vasopressors is not recommended. Phenylephrine should be used when a pure vasoconstrictor is desired in patients who may not require or do not tolerate the beta (β ) effects of dopamine or norepinephrine with or without dobutamine. Patients with high filling pressure and hypotension may benefit from the combination of phenylephrine and dobutamine. Investigational approaches to vasopressor-refractory hypotension in septic shock include the use of vasopressin and corticosteroids.

Renal-Dose Dopamine: From Hypothesis to Paradigm to Dogma to Myth and, Finally, Superstition?

Acute renal failure (ARF) is common in the critically ill and is associated with a high mortality rate. Its pathogenesis is not understood. Because animal models use ischemia to induce experimental ARF, there is the widespread belief that lack of blood flow is responsible for ARF. Low-dose dopamine (LDD) has been shown to increase renal blood flow in animal and in human volunteers. Thus, it has been administered to humans for almost 3 decades in the belief that it would lead to renal arterial vasodilation and increase renal blood flow (RBF). However, the etiology of ARF in critical illness is likely multifactorial, and the contribution of hypovolemia and reduced renal perfusion is unknown. Furthermore, interindividual variation in the pharmacokinetics of dopamine typically results in poor correlation between blood levels and administered dose, making accurate and reliable delivery of LDD difficult. Finally, dopamine is a proximal tubular diuretic that increases Na+ delivery to tubular cells, thus increasing their oxygen demands. Accordingly, even if LDD were able to preferentially increase RBF, there is no guarantee that it would restore renal parenchymal oxygen homeostasis. More important, 2 meta-analyses and a large double-blind, prospective, multiple-center, randomized controlled trial have failed to demonstrate that dopamine protects the kidney in critically ill patients with ARF. Currently, there is insufficient evidence to support the use of renal-dose dopamine in the intensive care unit.

Pharmacotherapy Update on the Use of Vasopressors and Inotropes in the Intensive Care Unit

This paper summarizes the pharmacologic properties of vasoactive medications used in the treatment of shock, including the inotropes and vasopressors. The clinical application of these therapies is discussed and recent studies describing their use and associated outcomes are also reported. Comprehension of hemodynamic principles and adrenergic and non-adrenergic receptor mechanisms are salient to the appropriate therapeutic utility of vasoactive medications for shock. Vasoactive medications can be classified based on their direct effects on vascular tone (vasoconstriction or vasodilation) and on the heart (presence or absence of positive inotropic effects). This classification highlights key similarities and differences with respect to pharmacology and hemodynamic effects. Vasopressors include pure vasoconstrictors (phenylephrine and vasopressin) and inoconstrictors (dopamine, norepinephrine, and epinephrine). Each of these medications acts as vasopressors to increase mean arterial pressure by augmenting vascular tone. Inotropes include inodilators (dobutamine and milrinone) and the aforementioned inoconstrictors. These medications act as inotropes by enhancing cardiac output through enhanced contractility. The inodilators also reduce afterload from systemic vasodilation. The relative hemodynamic effect of each agent varies depending on the dose administered, but is particularly apparent with dopamine. Recent large-scale clinical trials have evaluated vasopressors and determined that norepinephrine may be preferred as a first-line therapy for a broad range of shock states, most notably septic shock. Consequently, careful selection of vasoactive medications based on desired pharmacologic effects that are matched to the patient's underlying pathophysiology of shock may optimize hemodynamics while reducing the potential for adverse effects.

Review article: inotrope and vasopressor use in the emergency department

Shock is a common presentation to the ED, with the incidence of septic shock increasing in Australasia over the last decade. The choice of inotropic agent is likely dependent on previous experience and local practices of the emergency and other critical care departments. The relatively short duration of stay in the ED before transfer leaves little room for evaluating the appropriateness of and response to the agent chosen. Delays in transfer to inpatient facilities means that patients receive advanced critical care within the ED for longer, requiring initiation and titration of vasoactive agents in the ED. This article discusses the general concepts of shock and the indicators for inotrope and vasopressor use, revises the various agents available and reviews the current evidence for their use.

Estabilización posresucitación y transporte

Cardiopulmonary resuscitation does not end with restoration of spontaneous circulation; rather, it must be continued with the application of all the measures that allow organ function to be maintained. The initial goal of hemodynamic treatment is to achieve normal blood pressure for the patient's age by means of fluids and/or vasoactive drugs. The aim of respiratory treatment is to normalize ventilation and oxygenation without causing further lung injury, avoiding hyperoxia and hyperventilation as well as hypoxia and hypercapnia. Neurological stabilization aims to reduce secondary brain damage, by avoiding hypertension and hypotension, maintaining normal ventilation and oxygenation, and treating hyperglycemia, agitation and seizures. Although no specific studies in children are available, data from adults have shown that early moderate hypothermia attenuates brain damage secondary to cardiorespiratory arrest, without increasing complications. After the arrest, the need for analgesia and/or sedation must be considered. The process of transportation to the pediatric intensive care unit (PICU) requires the following steps: stabilizing the patient, checking for and stabilizing fractures and external wounds, ensuring a stable airway and intravenous lines, assessing the need for nasogastric and bladder tubes, taking blood samples for analyses, contacting the PICU and informing the staff about the child's condition, choosing the optimal vehicle for transportation according to the child's condition and the distance, checking pediatric equipment and medications, selecting experienced staff and, finally, maintaining close surveillance and monitoring during transportation.

Prophylactic fenoldopam for renal protection in sepsis: a randomized, double-blind, placebo-controlled pilot trial

OBJECTIVE

Acute renal failure is common in septic patients. Fenoldopam, a dopamine-1 receptor agonist, increases renal blood flow and may, therefore, reduce the risk of acute renal failure in such patients. Accordingly, we sought to determine the safety and efficacy of fenoldopam for the prevention of acute renal failure in septic patients.

DESIGN

Prospective, double-blind, placebo-controlled trial.

SETTING

Three multidisciplinary intensive care units at a university hospital.

PATIENTS

Three hundred septic patients with baseline serum creatinine concentrations <150 micromol/L.

INTERVENTIONS

We randomized patients to a continuous infusion of either fenoldopam (n = 150) at 0.09 microg x kg x min or placebo (n = 150) while in the intensive care unit. The primary outcome measure was the incidence of acute renal failure, defined as a serum creatinine concentration increase to >150 micromol/L, during study drug infusion.

MEASUREMENTS AND MAIN RESULTS

The incidence of acute renal failure was significantly lower in the fenoldopam group compared with the control group (29 vs. 51 patients; p = .006). The odds ratio of developing acute renal failure for patients treated with fenoldopam was estimated to be 0.47 (p = .005). The difference in the incidence of severe acute renal failure (creatinine >300 mumol/L), however, failed to achieve statistical significance (10 vs. 21; p = .056). The length of intensive care unit stay in surviving patients was significantly lower in the fenoldopam group compared with the control group (10.64 +/- 9.3 vs. 13.4 +/- 14.0; p < .001). There were no complications of fenoldopam infusion. A direct effect of treatment on the probability of death, beyond its effect on acute renal failure, was not significant (odds ratio = 0.68, p = .1).

CONCLUSIONS

Compared with placebo, low-dose fenoldopam resulted in a smaller increase in serum creatinine in septic patients. The clinical significance of this finding is uncertain. A large multiple-center trial is now needed to confirm these findings.

Practice parameters for hemodynamic support of sepsis in adult patients: 2004 update

OBJECTIVE

To provide the American College of Critical Care Medicine with updated guidelines for hemodynamic support of adult patients with sepsis.

DATA SOURCE

Publications relevant to hemodynamic support of septic patients were obtained from the medical literature, supplemented by the expertise and experience of members of an international task force convened from the membership of the Society of Critical Care Medicine.

STUDY SELECTION

Both human studies and relevant animal studies were considered.

DATA SYNTHESIS

The experts articles reviewed the literature and classified the strength of evidence of human studies according to study design and scientific value. Recommendations were drafted and graded levels based on an evidence-based rating system described in the text. The recommendations were debated, and the task force chairman modified the document until <10% of the experts disagreed with the recommendations.

CONCLUSIONS

An organized approach to the hemodynamic support of sepsis was formulated. The fundamental principle is that clinicians using hemodynamic therapies should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis by monitoring a combination of variables of global and regional perfusion. Using this approach, specific recommendations for fluid resuscitation, vasopressor therapy, and inotropic therapy of septic in adult patients were promulgated.

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+.

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.

Oropharyngeal aspiration in pediatric patients with endotracheal intubation

OBJECTIVE

To determine the prevalence and factors associated with oropharyngeal aspiration in pediatric patients submitted to mechanical ventilation and endotracheal intubation.

DESIGN

Prospective cross-sectional study.

SETTING

Four pediatric intensive care units.

PATIENTS

Fifty infants and children with endotracheal intubation submitted to mechanical ventilation.

INTERVENTIONS

Aspiration was determined by administering Evans blue dye in the oral cavity and searching the dye agent in the specimens obtained from two tracheal aspirates performed at 5- and 30-min intervals. During this period, the frequency of swallowing movements was continuously monitored using surface electromyography (biofeedback). The association between aspiration and age, sedation level, mean airway pressure, swallowing dynamics, and intubation route was tested using the chi-square and relative risk (95% confidence interval). Results also were adjusted by multivariate analysis.

MEASUREMENTS AND MAIN RESULTS

The overall prevalence of aspi-ration was 28% (n = 14). At the univariate analysis, aspiration was associated with sedation level (p =.03), frequency of swallowing movements (p =.0003), and orotracheal route (p =.03). The relative risk (95% confidence interval) for aspiration was 2.92 (1.32-6.42) in patients considered to be inadequately sedated (Hartwig 8-18); 14.08 (1.99-99.67) in patients presenting frequent swallowing (>30 movements in 30 mins); and 5.57 (0.8-38.85) in patients with orotracheal intubation. The multivariate analysis identified that the orotracheal route (p =.03) and frequent swallowing movements (p =.0007) were independently associated with aspiration.

CONCLUSIONS

Aspiration around the tracheal tube is a frequent finding (28%) in children undergoing mechanical ventilation. The frequent swallowing movements and the orotracheal intubation route were significantly associated with aspiration. These results suggest that the nasotracheal intubation route could be recommended as the first choice for reducing this potential clinical complication.

New approaches to the treatment of sepsis

The clinical spectrum of sepsis, severe sepsis, and septic shock is responsible for a growing number of deaths and excessive health care expenditures. Until recently, despite multiple clinical trials, no intervention provided a beneficial outcome in septic patients. Within the last 2 years, studies that involved drotrecogin alfa (activated), corticosteroid therapy, and early goal-directed therapy showed efficacy in those with severe sepsis and septic shock. These results have provided optimism for reducing sepsis-related mortality.

Is There Still a Place for Dopamine in the Modern Intensive Care Unit?

For many years, dopamine was considered an essential drug in the intensive care unit (ICU) for its cardiovascular effects and, even more, for its supposedly protective effects on renal function and splanchnic mucosal perfusion. There is now ample scientific evidence that low dose dopamine is ineffective for prevention and treatment of acute renal failure and for protection of the gut. Until recently, low-dose dopamine was considered to be relatively free of side effects. However, it is now clear that low-dose dopamine, besides not achieving the preset goal of organ protection, may also be deleterious because it can induce renal failure in normo- and hypovolemic patients. Furthermore, dopamine may cause harm by impairing mucosal blood flow and by aggravating reduced gastric motility. Dopamine also suppresses the secretion and function of anterior pituitary hormones, thereby aggravating catabolism and cellular immune dysfunction and inducing central hypothyroidism. In addition, dopamine blunts the ventilatory drive, increasing the risk of respiratory failure in patients who are being weaned from mechanical ventilation. We conclude that there is no longer a place for low-dose dopamine in the ICU and that, in view of its side effects, its extended use as a vasopressor may also be questioned.

Bad medicine: low-dose dopamine in the ICU

Low-dose dopamine administration (ie, doses < 5 microg/kg/min) has been advocated for 30 years as therapy in oliguric patients on the basis of its action on dopaminergic renal receptors. Recently, a large, multicenter, randomized, controlled trial has demonstrated that low-dose dopamine administered to critically ill patients who are at risk of renal failure does not confer clinically significant protection from renal dysfunction. In this review, we present the best evidence and summarize the effects of low-dose dopamine infusion in critically ill patients. We review the history and physiology of low-dose dopamine administration and discuss the reasons why dopamine is not clinically effective in the critically ill. In addition to the lack of renal efficacy, we present evidence that low-dose dopamine administration worsens splanchnic oxygenation, impairs GI function, impairs the endocrine and immunologic systems, and blunts ventilatory drive. We conclude that there is no justification for the use of low-dose dopamine administration in the critically ill.

Acute renal failure in hospitalized patients: part II

BACKGROUND

Acute renal failure (ARF) is a common condition in hospitalized patients. Research has been unable to identify the optimal target for therapeutic intervention; hence, effective prevention of and/or treatment for ARF remain elusive.

OBJECTIVE

To examine the usefulness of current and potential pharmacologic treatments in seriously ill, hospitalized patients.

DATA SOURCES

A MEDLINE search (1996-June 2002) was conducted using the search terms kidney (drug effects) and acute kidney failure (drug therapy). Bibliographies of selected articles were also examined to include all relevant investigations.

STUDY SELECTION AND DATA EXTRACTION

Review articles, meta-analyses, and clinical trials describing prevention of and treatment for hospital-acquired ARF were identified. Results from prospective, controlled trials were given priority when available.

CONCLUSIONS

Appropriate management of ARF includes prospective identification of at-risk patients, fluid administration, and optimal hemodynamic support. Drug treatments, including low-dose dopamine and diuretics, have demonstrated extremely limited benefits and have not been shown to improve patient outcome. Experimental agents influence cellular processes of renal dysfunction and recovery; unfortunately, relatively few drugs show promise for the future.

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.

Therapeutic Options for the Treatment of Impaired Gut Function

Abstract. Tissue hypoxia, especially in the splanchnic area, is still considered to be an important cofactor in the pathogenesis of multiple organ failure. Therefore, the specific effects of the various therapeutic interventions on splanchnic perfusion and oxygenation are of particular interest. Restoring and maintaining oxygen transport and tissue oxygenation is the most important step in the supportive treatment of patients with sepsis and impaired gut perfusion. Therefore, supportive treatment should be focused on an adequate volume resuscitation and appropriate use of vasoactive drugs. Adequate volume loading may be the most important step in the treatment of patients with septic shock. An elevated oxygen delivery may be beneficial in some patients, but the increase of oxygen delivery should be guided by the measurement of parameters assessing global and regional oxygenation. Forcing an elevation in oxygen delivery by the use of very high dosages of catecholamines can be harmful. Vasopressors should be used for achieving an adequate perfusion pressure. For norepinephrine, no negative effects on gut perfusion have been demonstrated. Epinephrine and dopamine should be avoided because they seem to redistribute blood flow away from the splanchnic region. There are no convincing data yet to support the routine use of low-dose dopamine or dopexamine to improve an impaired gut perfusion. There is even evidence that low-dose dopamine may reduce the mucosal perfusion in the gut in some patients. It has been suggested that dopexamine can improve splanchnic perfusion, but because these effects remain somewhat controversial, a general recommendation for dopexamine to improve gut perfusion is not justified.

Oliguria in the ICU. Systematic approach to diagnosis and treatment

Perioperative oliguria is common but rarely implies acute renal failure. We should interpret oliguria as a sign of intravascular hypovolemia and treat it as prerenal until proven otherwise. On the other hand, the absence of oliguria does not exclude acute renal failure. The most reliable clinical indicator of progressive renal dysfunction is a serial decline in creatinine clearance estimation, a measure of glomerular filtration rate.

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.

Dopamine in heart failure and critical care

Dopamine is widely used in critical care to prevent renal function loss. Nevertheless sufficient evidence is still lacking of reduction in end points like mortality or renal replacement therapy. Dopaminergic treatment in chronic heart failure (CHF) has provided an example of unexpected adverse outcome. Pharmacoepidemiological data. Provide additional evidence, finding excess mortality in current ibopamine users (relative risk 2.03 in NYHA I-II CHF, 1.37 in NYHA III-IV), while no relation was found with antiarrhythmic use. In critical care, studies after infrarenal aortic surgery or during septic shock, respectively, failed to find, expected specific renal effects of dopamine. Effects on splanchnic flow mainly depend on baseline flow levels. The implications of recently documented unwanted effects of dopamine, like reduced ventilation and oxygenation during hypoxia, are discussed. In conclusion, controlled clinical trials remain mandatory to assess the overall clinical effects of dopamine in critical care.

An evaluation of pharmacological strategies for the prevention and treatment of acute renal failure

Acute renal failure (ARF) occurs frequently in hospitalised patients, and is associated with significant morbidity and mortality. The most common and generalised forms of acute renal failure are pre-renal conditions and intra-renal acute tubular necrosis (ATN). Pre-renal ARF in its pure state should be entirely reversible by restoring renal perfusion, but in some cases ATN has already occurred. ATN remains a more vexing problem, and is seen most often with hypotension, perioperative or systemic inflammatory stresses, radiocontrast administration, and exposure to nephrotoxins. Among the available pharmacological options for prevention or treatment of ATN, there is a remarkable lack of definitive evidence supporting specific therapy in any setting. Although loop diuretics, mannitol, and dopamine are frequently used for prevention and/or treatment of ATN, clinical studies have failed to prove value. Other drugs with theoretical value, specifically atrial natriuretic peptide analogues, adenosine blockers, and calcium antagonists, have been insufficiently studied to recommend use. Other pharmacological options may arise in the future. Ensuring adequate intravascular fluid volume remains the only approach to managing ATN which can be considered relatively effective and safe. Given the abundant theoretical basis for the prevention and treatment of ATN with drugs, well conducted clinical studies with relevant outcome measures are clearly warranted.

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.

Effect of small-dose dopamine on mesenteric blood flow and renal function in a pig model of cardiopulmonary resuscitation with vasopressin

Vasopressin (antidiuretic hormone) seems a promising alternative to epinephrine for cardiopulmonary resuscitation (CPR) in cardiac arrest victims, mediating a pronounced blood flow shift toward vital organs. We evaluated the effects of small-dose dopamine on splanchnic blood flow and renal function after successful resuscitation with this potent vasoconstrictor in an established porcine CPR model. After 4 min of cardiac arrest and 3 min of CPR, animals received 0.4 U/kg vasopressin and were continuously infused with either dopamine 4 microg x kg(-1) x min(-1) (n = 6), or saline placebo (n = 6). Defibrillation was performed 5 min after drug administration; all animals were observed for 6 h after return of spontaneous circulation. During the postresuscitation phase, average mean +/- SD superior mesenteric artery blood flow was significantly (P = 0.002) higher in the dopamine group compared with the placebo group (1185+/-130 vs 740+/-235 mL/min), whereas renal blood flow was comparable between groups (255+/-40 vs 250+/-85 mL/min). The median calculated glomerular filtration rate had higher values in the dopamine group (70-120 mL/min) than in the placebo group (40-70 mL/min; P = 0.1 at 0 min and P = 0.08 at 360 min). We conclude that small-dose dopamine administration may be useful in improving superior mesenteric artery blood flow and renal function after successful resuscitation with vasopressin.

IMPLICATIONS

Long-term survival after cardiac arrest may be determined by the ability to ensure adequate organ perfusion during cardiopulmonary resuscitation and in the postresuscitation phase. In this regard, small-dose dopamine improved postresuscitation blood flow to the mesenteric bed when vasopressin was used as an alternative vasopressor in an animal model of cardiac arrest.

Supportive therapy of the sepsis syndrome

Adequate volume loading may be the most important step in the treatment of patients with septic shock. Techniques allowing us to achieve and tightly control volume loading and regional perfusion are considered to be helpful. An elevated oxygen delivery may be beneficial in some patients but the increase of oxygen delivery should be guided by the measurement of parameters assessing global and regional oxygenation. Forcing an increase in oxygen delivery by the use of very high dosages of catecholamines can be harmful. Vasopressors should be used for achieving an adequate perfusion pressure. For norepinephrine, no negative effects on regional perfusion have been demonstrated. Epinephrine and dopamine should be avoided because they seem to redistribute blood flow away from the splanchnic region. There are no convincing data yet to support the routine use of low dose dopamine or dopexamine in patients with sepsis. Neither low dose dopamine nor dopexamine has been proven to prevent renal failure in septic patients. Furthermore, there is evidence that low dose dopamine may reduce mucosal perfusion in the gut in some patients. There is some suggestion that dopexamine can improve splanchnic perfusion but since these effects remain somewhat controversial, there is no reason for a general recommendation for dopexamine in septic patients.

The effects of low-dose dopamine infusions on haemodynamic and renal parameters in patients with septic shock requiring treatment with noradrenaline

OBJECTIVE

To investigate whether low-dose dopamine (LDD) has a significant effect on systemic haemodynamic variables and renal function when used in conjunction with high-dose noradrenaline in optimally volume-resuscitated patients with septic shock.

DESIGN

A prospective clinical study in which each patient acted as his/her own control.

SETTING

Teaching hospital Intensive Care Unit.

PATIENTS

Twenty-one patients with septic shock treated with high-dose noradrenaline were studied, 17 patients completed the study.

INTERVENTIONS

Fluid loading to an optimal left ventricular stroke work index (LVSWI) whilst on more noradrenaline than 10 mcg/min and dopamine of 2.5 mcg/kg per min. Three study periods each of 2 h with LDD present, withdrawn and restarted. During each period a complete haemodynamic profile and measurement of urine flow rate, creatinine clearance and sodium excretion was performed.

MEASUREMENT AND RESULTS

Removing and restarting LDD caused marked changes in cardiac index (CI, 17% fall, p < 0.01: 23% rise, p < 0.01), stroke volume (SV, 11% fall, p < 0.05: 14% rise, p < 0.05) and systolic blood pressure (SBP, 11% fall, p < 0.05: 14% rise, p < 0.05). Urine volume fell by 40% (p < 0.05) when dopamine was withdrawn. Significant reductions in sodium excretion (p < 0.05) and fractional sodium excretion (p < 0.05) also occurred on stopping LLD. Changes in creatinine clearance were not statistically significant.

CONCLUSION

Low-dose dopamine causes significant increases in SBP SV, cardiac output and urine flow during treatment with noradrenaline.

"Renal dose" dopamine in surgical patients: dogma or science?

OBJECTIVE

"Renal dose" dopamine is widely used in the perioperative period to provide renal protection. A comprehensive review of the literature was performed to determine whether dopamine does in fact confer protection on the kidneys of surgical patients.

SUMMARY BACKGROUND DATA

Studies in healthy animals and human volunteers reveal that dopamine causes diuresis and natriuresis, as well as some degree of renal vasodilatation.

RESULTS

Studies of the perioperative use of dopamine fail to demonstrate any benefit of dopamine in preventing renal failure. Studies in congestive heart failure, critical illness, and sepsis also fail to show any benefit of dopamine other than diuresis. Further, dopamine administration is not completely without risk, because of dopamine's catecholamine and neuroendocrine functions.

CONCLUSIONS

Routine use of prophylactic "renal dose" dopamine in surgical patients is not recommended.

Effects of low-dose dopamine on renal and systemic hemodynamics during incremental norepinephrine infusion in healthy volunteers

OBJECTIVES

To assess the effects of low-dose dopamine on norepinephrine-induced renal and systemic vasoconstriction in normotensive healthy subjects.

DESIGN

On separate days, either a low-dose dopamine (4 microg/kg/min) or a placebo (5% glucose) infusion was added in a single, blinded, randomized order to incremental norepinephrine infusions of 40, 80, and 150 ng/kg/min over a 60-min period each.

SETTING

Outpatient clinic of a university-affiliated hospital.

SUBJECTS

Normotensive healthy volunteers.

INTERVENTIONS

Infusions of norepinephrine and dopamine.

MEASUREMENTS AND MAIN RESULTS

Blood pressure and heart rate were measured with a semiautomated device, and glomerular filtration rate and effective renal plasma flow were determined with constant infusions of 125I-iothalamate and 131I-hippurate, respectively. Norepinephrine alone progressively increased mean arterial pressure to pressor levels, whereas this effect was attenuated by the addition of dopamine (p < .05 vs. norepinephrine alone). Glomerular filtration rate increased during lower norepinephrine doses and did not decrease at the highest norepinephrine dose. Addition of dopamine further increased glomerular filtration rate. Effective renal plasma flow decreased with each norepinephrine alone infusion step, but this decrease was completely prevented by concomitant dopamine infusion (p < .01 vs. norepinephrine). Sodium excretion tended to decrease with norepinephrine, but increased two- to three-fold after addition of dopamine (p < .01 vs. norepinephrine alone).

CONCLUSIONS

In healthy man, norepinephrine causes a large decrease in renal plasma flow but not in glomerular filtration rate. Concomitant dopamine administration prevents this decrease in renal plasma flow, increases sodium excretion, and also attenuates the norepinephrine-induced systemic blood pressure increase. These findings warrant further clinical evaluation of the effect of concomitant low-dose dopamine and norepinephrine administration in critically ill patients.

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.