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

International Renal Interest Society best practice consensus guidelines for the diagnosis and management of acute kidney injury in cats and dogs

Acute kidney injury (AKI) is defined as an injury to the renal parenchyma, with or without a decrease in kidney function, as reflected by accumulation of uremic toxins or altered urine production (i.e., increased or decreased). AKI might result from any of several factors, including ischemia, inflammation, nephrotoxins, and infectious diseases. AKI can be community- or hospital-acquired. The latter was not previously considered a common cause for AKI in animals; however, recent evidence suggests that the prevalence of hospital-acquired AKI is increasing in veterinary medicine. This is likely due to a combination of increased recognition and awareness of AKI, as well as increased treatment intensity (e.g., ventilation and prolonged hospitalization) in some veterinary patients and increased management of geriatric veterinary patients with multiple comorbidities. Advancements in the management of AKI, including the increased availability of renal replacement therapies, have been made; however, the overall mortality of animals with AKI remains high. Despite the high prevalence of AKI and the high mortality rate, the body of evidence regarding the diagnosis and the management of AKI in veterinary medicine is very limited. Consequently, the International Renal Interest Society (IRIS) constructed a working group to provide guidelines for animals with AKI. Recommendations are based on the available literature and the clinical experience of the members of the working group and reflect consensus of opinion. Fifty statements were generated and were voted on in all aspects of AKI and explanatory text can be found either before or after each statement.

Augmented Renal Clearance in Critical Illness: An Important Consideration in Drug Dosing

Augmented renal clearance (ARC) is a manifestation of enhanced renal function seen in critically ill patients. The use of regular unadjusted doses of renally eliminated drugs in patients with ARC might lead to therapy failure. The purpose of this scoping review was to provide and up-to-date summary of the available evidence pertaining to the phenomenon of ARC. A literature search of databases of available evidence in humans, with no language restriction, was conducted. Databases searched were MEDLINE (1946 to April 2017), EMBASE (1974 to April 2017) and the Cochrane Library (1999 to April 2017). A total of 57 records were included in the present review: 39 observational studies (25 prospective, 14 retrospective), 6 case reports/series and 12 conference abstracts. ARC has been reported to range from 14-80%. ARC is currently defined as an increased creatinine clearance of greater than 130 mL/min/1.73 m² best measured by 8-24 h urine collection. Patients exhibiting ARC tend to be younger (<50 years old), of male gender, had a recent history of trauma, and had lower critical illness severity scores. Numerous studies have reported antimicrobials treatment failures when using standard dosing regimens in patients with ARC. In conclusion, ARC is an important phenomenon that might have significant impact on outcome in critically ill patients. Identifying patients at risk, using higher doses of renally eliminated drugs or use of non-renally eliminated alternatives might need to be considered in ICU patients with ARC. More research is needed to solidify dosing recommendations of various drugs in patients with ARC.

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.

Cardiac complications associated with goal-directed therapy in high-risk surgical patients: a meta-analysis

Patients with limited cardiopulmonary reserve are at risk of mortality and morbidity after major surgery. Augmentation of oxygen delivery index (DO2I) with i.v. fluids and inotropes (goal-directed therapy, GDT) has been shown to reduce postoperative mortality and morbidity in high-risk patients. Concerns regarding cardiac complications associated with fluid challenges and inotropes may prevent clinicians from performing GDT in patients who need it most. We hypothesized that GDT is not associated with an increased risk of cardiac complications in high-risk, non-cardiac surgical patients. We performed a systematic search of Medline, Embase, and CENTRAL databases for randomized controlled trials (RCTs) of GDT in high-risk surgical patients. Studies including cardiac surgery, trauma, and paediatric surgery were excluded. We reviewed the rates of all cardiac complications, arrhythmias, myocardial ischaemia, and acute pulmonary oedema. Meta-analyses were performed using RevMan software. Data are presented as odds ratios (ORs), [95% confidence intervals (CIs)], and P-values. Twenty-two RCTs including 2129 patients reported cardiac complications. GDT was associated with a reduction in total cardiovascular (CVS) complications [OR=0.54, (0.38-0.76), P=0.0005] and arrhythmias [OR=0.54, (0.35-0.85), P=0.007]. GDT was not associated with an increase in acute pulmonary oedema [OR=0.69, (0.43-1.10), P=0.12] or myocardial ischaemia [OR=0.70, (0.38-1.28), P=0.25]. Subgroup analysis revealed the benefit is most pronounced in patients receiving fluid and inotrope therapy to achieve a supranormal DO2I, with the use of minimally invasive cardiac output monitors. Treatment of high-risk surgical patients GDT is not associated with an increased risk of cardiac complications; GDT with fluids and inotropes to optimize DO2I during early GDT reduces postoperative CVS complications.

Clinical review: Goal-directed therapy-what is the evidence in surgical patients? The effect on different risk groups

Patients with limited cardiac reserve are less likely to survive and develop more complications following major surgery. By augmenting oxygen delivery index (DO₂I) with a combination of intravenous fluids and inotropes (goal directed therapy (GDT)), postoperative mortality and morbidity of high-risk patients may be reduced. However, although most studies suggest that GDT may improve outcome in high-risk surgical patients, it is still not widely practiced. We set out to test the hypothesis that GDT results in greatest benefit in terms of mortality and morbidity in patients with the highest risk of mortality and have undertaken a systematic review of the current literature to see if this is correct. We performed a systematic search of Medline, Embase and CENTRAL databases for randomized controlled trials (RCTs) and reviews of GDT in surgical patients. To minimize heterogeneity we excluded studies involving cardiac, trauma, and paediatric surgery. Extremely high risk, high risk and intermediate risks of mortality were defined as >20%, 5 to 20% and <5% mortality rates in the control arms of the trials, respectively. Meta analyses were performed and Forest plots drawn using RevMan software. Data are presented as odd ratios (OR; 95% confidence intervals (CI), and P-values). A total of 32 RCTs including 2,808 patients were reviewed. All studies reported mortality. Five studies (including 300 patients) were excluded from assessment of complication rates as the number of patients with complications was not reported. The mortality benefit of GDT was confined to the extremely high-risk group (OR = 0.20, 95% CI 0.09 to 0.41; P < 0.0001). Complication rates were reduced in all subgroups (OR = 0.45, 95% CI 0.34 to 0.60; P < 0.00001). The morbidity benefit was greatest amongst patients in the extremely high-risk subgroup (OR = 0.27, 95% CI 0.15 to 0.51; P < 0.0001), followed by the intermediate risk subgroup (OR = 0.43, 95% CI 0.27 to 0.67; P = 0.0002), and the high-risk subgroup (OR 0.56, 95% CI 0.36 to 0.89; P = 0.01). Despite heterogeneity in trial quality and design, we found GDT to be beneficial in all high-risk patients undergoing major surgery. The mortality benefit of GDT was confined to the subgroup of patients at extremely high risk of death. The reduction of complication rates was seen across all subgroups of GDT patients.

Significance of the renal functional reserve in reflux nephropathy: an evaluation according to the degree of glomerular damage

OBJECTIVE

In the treatment of progressive reflux nephropathy (RN), the therapeutic benefit and prognosis of the renal function in RN patients appears to be influenced by the degree of renal functional reserve. We designed this study to determine the presence and characteristics of the renal functional reserve in RN patients.

MATERIALS AND METHODS

In the 35 RN patients with renal scars (19 males; mean age 16.1 years), an exogenous renal clearance test was performed to measure the glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF). In the second half of this test, the renal functional reserve was estimated by measuring the GFR and ERPF during low-dose dopamine infusion. These measurements were then compared with the glomerular size, which had been previously determined by a renal biopsy.

RESULTS

Among the patients with a normal glomerular size (-2SD to +2SD), the GFR markedly increased after low-dose dopamine infusion (from 112.15 +/- 52.51 to 182.07 +/- 69.95 mL/min, p < 0.0001), whereas an increase in ERPF was not significant. Among the patients with an enlarged glomerular size (+2SD to +4SD), the GFR and ERPF increased significantly over the baseline values (from 54.60 +/- 32.90 to 114.00 +/- 65.48 mL/min, p = 0.0076; from 281.01 +/- 152.54 to 622.43 +/- 392.73 mL/min, p = 0.0155, respectively). Among the patients with an extremely enlarged glomerular size (>+4SD), both the GFR and ERPF remained almost completely unchanged.

CONCLUSION

The renal functional reserve was present even among progressive RN patients with a glomerular size ranging between +2SD and +4SD.

Low-dose dopamine in the intensive care unit

For much of the last four decades, low-dose dopamine has been considered the drug of choice to treat and prevent renal failure in the intensive care unit (ICU). The multifactorial etiology of renal failure in the ICU and the presence of coexisting multisystem organ dysfunction make the design and execution of clinical trials to study this problem difficult. However, in the last decade, several meta-analyses and one large randomized trial have all shown a lack of benefit of low-dose dopamine in improving renal function. There are multiple reasons for this lack of efficacy. While dopamine does cause a diuretic effect, it does very little to improve mortality, creatinine clearance, or the incidence of dialysis. Evidence is also growing of its adverse effects on the immune, endocrine, and respiratory systems. It may also potentially increase mortality in sepsis. It is the opinion of the authors that the practice of using low-dose dopamine should be abandoned. Other drugs and treatment modalities need to be explored to address the serious issue of renal failure in the ICU.

Acute renal failure in the elderly: particular characteristics

Elderly individuals comprise the faster growing patient population group and acute renal failure (ARF) is quite common among them, although exact numbers are not known. We reviewed the literature with regards to the characteristics of ARF in elderly patients and describe some useful guidelines. The ageing kidney is characterized by many structural and functional changes, which are mainly due to various chronic disorders, such as hypertension, diabetes and atherosclerosis, which are highly prevalent in these patients. A number of structural and functional changes characteristic of the ageing kidney make elderly people especially prone to renal damage. ARF in the elderly is frequently of multifactorial origin and often with an atypical presentation, like the "intermediate syndrome", which combines characteristics of pre-renal azotemia and acute tubular necrosis. Physical examination and laboratory blood and urine indices may sometimes be misleading occasionally leading to misdiagnosis. Prophylaxis remains the preferred approach to therapy: one should avoid nephrotoxic drugs and poly-pharmacy, adjust drug doses and achieve adequate hydration of the patient as cautiously as possible. Dialysis therapies can be used for treatment of ARF irrespective of age and carry a good prognosis.

Comparison of Systemic and Renal Effects of Dopexamine and Dopamine in Norepinephrine-Treated Septic Shock

OBJECTIVES

Vasopressor-induced vasoconstriction may compromise renal and splanchnic blood flow in patients with septic shock, resulting in secondary organ failures. The authors compared the effects of the vasodilatatory agent dopexamine against renal-dose dopamine and placebo in patients with norepinephrine therapy and septic shock, using 24-hour serum creatinine clearance (C(crea)) as a major endpoint. The primary hypothesis to be tested was that dopexamine is more effective than dopamine and that dopamine shows better effects than placebo regarding organ failures and C(crea).

DESIGN

A prospective, randomized, controlled, double-blinded study.

SETTING

Intensive care unit in a tertiary care university hospital.

PARTICIPANTS

Sixty-one patients with septic shock defined according to established criteria.

INTERVENTIONS

Patients received either dopexamine (2 microg/kg/min, n = 20), dopamine (3 microg/kg/min, n = 21), or placebo (n = 20).

RESULTS

The trial groups were similar in terms of baseline characteristics. The authors found no significant differences among the dopexamine, dopamine, and placebo groups with regard to a comprehensive number of renal function parameters including C(crea) and organ-failure scores. There was a significant increase in heart rate after dopexamine infusion; other hemodynamic parameters remained unchanged in the dopexamine group. In a post hoc analysis that included only patients with renal impairment at study inclusion (n = 28), patients who received dopamine showed significant improvements in C(crea) when compared with placebo. Dopexamine was not effective in this subgroup.

CONCLUSIONS

Dopexamine is no more effective than dopamine or placebo regarding renal function in patients with septic shock requiring norepinephrine. Both therapies do not influence organ-failure scores.

A comparison between fenoldopam and low-dose dopamine in early renal dysfunction of critically ill patients*

OBJECTIVE

Fenoldopam mesylate is a selective dopamine-1 agonist, with no effect on dopamine-2 and alpha1 receptors, producing a selective renal vasodilation. This may favor the kidney oxygen supply/demand ratio and prevent acute renal failure. The aim of the study was to investigate if fenoldopam can provide greater benefit than low-dose dopamine in early renal dysfunction of critically ill patients.

DESIGN

Prospective, multiple-center, randomized, controlled trial.

SETTING

University and city hospital intensive care units.

PATIENTS

One hundred adult critically ill patients with early renal dysfunction (intensive care unit stay<1 wk, hemodynamic stability, and urine output<or=0.5 mL/kg over a 6-hr period and/or serum creatinine concentration>or=1.5 mg/dL and<or= 3.5 mg/dL).

INTERVENTIONS

Patients were randomized to receive 2 microg/kg/min dopamine (group D) or 0.1 microg/kg/min fenoldopam mesylate (group F). Drugs were administered as continuous infusion over a 4-day period.

MEASUREMENTS AND MAIN RESULTS

Systemic hemodynamic and renal function variables were recorded daily. The two groups were well matched at enrollment for illness severity and hemodynamic and renal dysfunction. No differences in heart rate or systolic, diastolic, or mean arterial pressure were observed between groups. Fenoldopam produced a more significant reduction in creatinine values compared with dopamine after 2, 3, and 4 days of infusion (change from baseline at time 2, -0.32 vs. -0.03 mg/dL, p=.047; at time 3, -0.45 vs. -0.09 mg/dL, p=.047; and at time 4, -.041 vs. -0.09 mg/dL, p=.02, in groups F and D, respectively). The maximum decrease in creatinine compared with baseline was significantly greater in group F than group D (-0.53+/-0.47 vs. -0.34+/-0.38 mg/dL, p=.027). Moreover, 66% of patients in group F had a creatinine decrease>10% of the baseline value at the end of infusion, compared with only 46% in dopamine group (chi-square=4.06, p=.04). Total urinary output during drug infusion was not significantly different between groups. After 1 day, urinary output was lower in group F compared with group D (p<.05).

CONCLUSIONS

In critically ill patients, a continuous infusion of fenoldopam at 0.1 microg/kg/min does not cause any clinically significant hemodynamic impairment and improves renal function compared with renal dose dopamine. In the setting of acute early renal dysfunction, before severe renal failure has occurred, the attempt to reverse renal hypoperfusion with fenoldopam is more effective than with low-dose dopamine.

Antimicrobial therapy in critically ill patients: a review of pathophysiological conditions responsible for altered disposition and pharmacokinetic variability

Antimicrobials are among the most important and commonly prescribed drugs in the management of critically ill patients. Selecting the appropriate antimicrobial at the commencement of therapy, both in terms of spectrum of activity and dose and frequency of administration according to concentration or time dependency, is mandatory in this setting. Despite appropriate standard dosage regimens, failure of the antimicrobial treatment may occur because of the inability of the antimicrobial to achieve adequate concentrations at the infection site through alterations in its pharmacokinetics due to underlying pathophysiological conditions. According to the intrinsic chemicophysical properties of antimicrobials, hydrophilic antimicrobials (beta-lactams, aminoglycosides, glycopeptides) have to be considered at much higher risk of inter- and intraindividual pharmacokinetic variations than lipophilic antimicrobials (macrolides, fluoroquinolones, tetracyclines, chloramphenicol, rifampicin [rifampin]) in critically ill patients, with significant frequent fluctuations of plasma concentrations that may require significant dosage adjustments. For example, underexposure may occur because of increased volume of distribution (as a result of oedema in sepsis and trauma, pleural effusion, ascites, mediastinitis, fluid therapy or indwelling post-surgical drainage) and/or enhanced renal clearance (as a result of burns, drug abuse, hyperdynamic conditions during sepsis, acute leukaemia or use of haemodynamically active drugs). On the other hand, overexposure may occur because of a drop in renal clearance caused by renal impairment. Care with all these factors whenever choosing an antimicrobial may substantially improve the outcome of antimicrobial therapy in critically ill patients. However, since these situations may often coexist in the same patient and pharmacokinetic variability may be unpredictable, the antimicrobial policy may further benefit from real-time application of therapeutic drug monitoring, since this practice, by tailoring exposure to the individual patient, may consequently be helpful both in improving the outcome of antimicrobial therapy and in containing the spread of resistance in the hospital setting.

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+.

Renal, but not systemic, hemodynamic effects of dopamine are influenced by the severity of congestive heart failure

OBJECTIVE

To determine whether the short-term systemic and renal hemodynamic response to dopamine is influenced by clinical severity of congestive heart failure.

DESIGN

Effects of increasing doses of dopamine were assessed in patients consecutively admitted for acutely decompensated congestive heart failure.

SETTING

Intensive care unit.

PATIENTS

We enrolled 16 congestive heart failure patients stratified by clinical severity (New York Heart Association [NYHA] class III, n = 8; NYHA class IV, n = 8) and two additional NYHA class III patients as controls.

INTERVENTIONS

Measurements were carried out throughout five 20-min experimental periods: baseline, dopamine infusion at 2, 4, and 6 microg x kg(-1) x min(-1), and recovery. Controls received a similar amount of saline.

MEASUREMENTS AND MAIN RESULTS

Systemic and renal hemodynamics were determined respectively by right cardiac catheterization and radioisotopes (iodine 131-labeled hippuran and iodine 125-labeled iothalamate clearance). The peak increase in heart rate and cardiac index occurred at a dopamine dose of 4-6 microg x kg(-1) x min(-1). The dose-response relation was similar in NYHA classes III and IV. Improvement in effective renal plasma flow and glomerular filtration rate, peaking at 4 microg x kg(-1) x min(-1), was more rapid and marked in NYHA class III than class IV patients, in whom the renal fraction of cardiac output failed to increase. The systemic and renal effects of dopamine were independent of age. No change occurred in controls.

CONCLUSIONS

The dose of dopamine producing an optimal improvement of systemic and renal hemodynamics in congestive heart failure is higher than usually reported. A greater clinical severity of congestive heart failure impairs the renal effects of dopamine, probably through a selective loss in renal vasodilating capacity.

Recombinant human atrial natriuretic peptide in ischemic acute renal failure: A randomized placebo-controlled trial*

OBJECTIVE

Acute renal failure is associated with significant morbidity and mortality rates. Need for dialysis is an independent risk factor for early mortality after complicated cardiac surgery. Human atrial natriuretic peptide (h-ANP) is a potent endogenous natriuretic and diuretic substance. Exogenous administration of h-ANP increases glomerular filtration rate and renal blood flow in clinical acute renal failure. We have studied the effects of h-ANP on renal outcome in ischemic acute renal failure.

DESIGN

A prospective, double-blind, randomized, placebo-controlled study.

SETTING

Cardiothoracic intensive care units of two tertiary care centers.

PATIENTS

Sixty-one patients with normal preoperative renal function suffering from postcardiac surgical heart failure requiring significant inotropic and vasoactive support.

INTERVENTIONS

The patients were randomized to receive a continuous infusion of either recombinant h-ANP (50 ng.kg(-1).min(-1)) or placebo when serum creatinine increased by >50% from baseline. The treatment with h-ANP/placebo continued until serum creatinine decreased below the trigger value for inclusion or the patients fulfilled predefined criteria for dialysis.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was dialysis on or before day 21 after the start of treatment. Secondary renal outcome variables were dialysis-free survival at day 21 and creatinine clearance. Twenty-nine patients were assigned h-ANP and 30 placebo. Six (21%) patients in the h-ANP group compared with 14 (47%) in the placebo group needed dialysis before or at day 21 (hazard ratio, 0.28; 95% confidence interval, 0.10-0.73; p =.009). Eight (28%) patients in the h-ANP group compared with 17 (57%) in the placebo group suffered from the combined end point dialysis or death before or at day 21 (hazard ratio, 0.35; 95% confidence interval, 0.14-0.82; p =.017). h-ANP improved creatinine clearance in contrast to placebo (p =.040).

CONCLUSIONS

Infusion of h-ANP at a rate of 50 ng.kg(-1).min(-1) enhances renal excretory function, decreases the probability of dialysis, and improves dialysis-free survival in early, ischemic acute renal dysfunction after complicated cardiac surgery.

Should We Give Prophylactic “Renal‐Dose” Dopamine After Coronary Artery Bypass Surgery?

OBJECTIVE

A prospective double-blind randomized study undertaken to assess the effect of postoperative prophylactic "renal-dose" dopamine on post-coronary artery bypass grafting surgery's clinical outcome.

METHODS

Eighty-five consecutive patients undergoing CABG operation were randomized to receive either 3-5 microg/kg/min dopamine (group D, n = 41) or saline as placebo (group P, n = 45) for 48 postoperative hours. Clinical outcome parameters were collected for four postoperative days.

RESULTS

Preoperative and operative parameters were similar in both groups. Four patients from group P and none from group D reached an end-point of the study (oliguria, renal dysfunction) and received dopamine. Two patients from group P and none from group D needed an additional inotropic support. Mean arterial pressure values were similar during the first 24 hours after operation, but left atrial pressure values tended to be higher in group P (10 +/- 4 vs 7 +/- 3 mmH2O, p = 0.18). The mean pH was higher in group D at 8 hours after operation (7.38 +/- 0.2 vs 7.36 +/- 0.3, p = NS), due to higher bicarbonate levels (23 +/- 2 mmol/l vs 21 +/- 2, p = 0.49). The incidence of lung congestion in chest X-rays and CT scans was significantly higher in group P (50% vs 29%, p = 0.073 at 48 hours postoperatively). Room air blood O2 saturation and maximal expiratory volume tended to be higher in group D (at 72 hours after operation- 92 +/- 4 vs 90%+/- 5, p = 0.29 and 646 +/- 276 vs 485 ml +/- 206, p = 0.16, respectively). There was no statistical difference in urine output but the amount of furosemide given to patients in group P was significantly higher (during the first 8 hours 2.5 +/- 0.5 vs. 0.3 mg +/- 1.6, p = 0.07). Plasma creatinine levels were significantly lower in group D (at 24 hours 0.93 +/- 0.02 vs 1.05 mg/dL +/- 0.02, p = 0.02). Mobilization after surgery was faster in group D.

CONCLUSIONS

Prophylactic dopamine administration after coronary artery bypass grafting surgery improves patient hemodynamic and renal status, reduces the need for additional medical support (inotropes and furosemide) and thus, provides stable postoperative course.

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.

Use of creatinine clearances to monitor the effect of low-dose dopamine in critically ill surgical patients

INTRODUCTION

Despite uncertain evidence of its efficacy, "low-dose dopamine" (2-5 microg/kg/min) has often been used to augment renal perfusion in critically ill surgical patients. The 2-h creatinine clearance (CC) has been shown to be a monitor of renal function in critically ill patients. We therefore studied the use of sequential CC determinations to monitor the effect of low-dose dopamine (LDD) in surgical intensive care unit (SICU) patients. We hypothesized that sequential CC measurements could demonstrate whether individual patients had positive responses in renal function to LDD.

METHODS

Data were prospectively collected for patients on LDD in a university SICU. CC were recorded for these patients immediately before and after the institution of LDD or before and after the cessation of LDD. APACHE II scores, gender, urine creatinine, age, blood pressure, heart rate, and urine output (UO) were also recorded for these patients; P < 0.05.

RESULTS

Twenty-four pairs of CC values were observed during the study. The mean APACHE II score for the patients was 15.1. In 10 cases after initiation of LDD, the mean CC increased from 52.5 +/- 23.7 ml/min to 68.1 +/- 33.8 ml/min (P = 0.056). UO also increased from 48.0 +/- 27 to 75.9 +/- 49 ml/h (NS). In 14 cases after discontinuation of LDD, CC decreased from 85.6 +/- 36.3 ml/min to 63.6 +/- 45.5 ml/min (P = 0.044) and UO decreased from 105.1 +/- 73.9 to 89.6 +/- 76.7 ml/h (NS). Overall, 13 of the 24 patients had a 25% change or more in CC upon initiation or cessation of LDD.

CONCLUSIONS

LDD institution increased CC in individual patients in the SICU population. Because using LDD in the absence of a discernable improvement in renal function is costly and may harbor risks, we recommend following CC in patients on LDD to determine which patients derive benefit from the intervention.

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.

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.

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.

Effects of dopamine infusion on cardiac and renal blood flows in dogs

In veterinary medicine, dopamine is currently being administered clinically by infusion for treatment of kidney disorders at low doses (< or = 3 microg/kg/min) and for assessment of hemodynamics at high doses (> or = 5 microg/kg/min). However, since high doses of dopamine cause peripheral vasoconstriction due to its effect on alpha adrenoceptors, high doses have no longer been recommended. The present study was conducted to explore possible regimens for the use of dopamine infusion in dogs. The regional (renal and cardiac) blood flow for 60 min was measured by using colored microspheres at three doses (3, 10 and 20 microg/kg/min) of dopamine infusion in healthy anesthetized mongrel dogs. The effects on kidney and peripheral hemodynamics at each dose and the resultant cardiac output, mean arterial blood pressure and total peripheral resistance were determined. Renal blood flow increased markedly at 3 microg/kg/min dopamine. Improvement in hemodynamics indicated by marked increase in cardiac blood flow, cardiac output and mean arterial blood pressure and decreased total peripheral resistance was observed at higher doses (10 and 20 microg/kg/min). At 10 microg/kg/min, in addition to the satisfactory increase in cardiac blood flow, there was also a stable satisfactory increase in renal blood flow. However, at 20 microg/kg/min, increased myocardial oxygen consumption (manifested by marked increased in cardiac output), arrythmia and irregular increase in renal blood flow were detected. This study suggests that the clinical use of dopamine infusion in dogs could be safely expanded to moderately higher doses.

Strategies for management of acute renal failure

Acute renal failure (ARF) is often defined as the sudden inability of the kidneys to regulate water and solute balance. ARF may be more broadly defined as rapid deterioration of renal function resulting in the accumulation of nitrogenous wastes such as urea and creatinine. Clinically, oliguria is defined as urine flow of less than 2 mL/kg/h and anuria has no measurable urine production. In animals, the most common cause of ARF is nephrotoxicity; ischemia ranks second, with interstitial and glomerular diseases following.

Critical care of the hematopoietic stem cell patient

Hematopoietic stem cell transplantation is evolving into a treatment modality with expanding indications and volume and with excellent outcomes, although it carries significant risk for morbidity and mortality affecting most major organ systems and often requires ICU care. With continuing improvements in supportive care and specific therapy of complications following HCT including the open-lung strategy of mechanical ventilation, use of nitric oxide, less toxic myeloablative regimens, newer classes of antibiotics, and improved immunosuppression strategies, it is hoped that mortality in this setting will continue to decline in coming years.

The Year in Review: Critical Care Medicine

Background: There have been significant recent advances in the pharmacotherapeutic management of critically ill patients. The purpose of this article is to review and discuss the most pertinent published literature in the areas of neurology, cardiovascular diseases, infectious diseases, nephrology, hematology, and gastroenterology as it pertains to critical care in order to provide an update for the critical care practitioner.

Methods: We performed a Medline search from July 1999 to December 2000 utilizing terms relating to the pharmacotherapy of the specific aforementioned topics in critical care medicine. We focused on English-language clinical studies performed in adult intensive care unit (ICU) patients. From these articles we selected those that would have a practical impact on drug therapy in the ICU or the development of drug usage guidelines for critically ill patients. Review articles were generally not included.

Results: The following topics were found to be either new developments or of potentially significant impact in the management of adult critically ill patients. In the area of neurology, advances were found with respect to optimization of regimens for sedative and neuromuscular blocking agents, validation of sedation scales and tools, and in the treatment of head injury patients. In the cardiovascular diseases, most studies related to the hemodynamic support of septic shock. We focus on developments in fluid resuscitation, optimization of global and regional oxygen transport variables, the repositioning of vasopressor agents, and a return to the use of steroids. Given the high mortality rate associated with the development of acute renal failure in the ICU, there has been a consistent attempt to develop preventative and treatment strategies for these patients, including optimization of antimicrobial dosing methods. Several epidemiological and longitudinal studies document changes in multi-drug antimicrobial resistance patterns. The use of treatment guidelines for antimicrobials in the critically ill improves outcomes in most patients. Significant attention has focused on the characterization of anemia in the ICU and the development of alternative pharmacological strategies in its treatment. Finally, in gastroenterology, the main focus has been the investigation of methods to optimize the delivery of enteral nutrition given its proven benefits in critically ill patients.

Conclusions: Significant advances in the areas of neurological, cardiovascular, infectious diseases, renal, hematological, and gastrointestinal issues in the pharmacotherapy of critically ill patients have been published over the course of the past year. Many of these studies have yielded data that may be incorporated into the pharmacotherapeutic management of ICU patients, hence maximizing outcomes.