Effect of "renal-dose" dopamine on renal function following cardiac surgery

Relationship between intraoperative dopamine infusion and postoperative acute kidney injury in patients undergoing open abdominal aorta aneurysm repair

Background

Acute kidney injury (AKI) is one of the most common complications in patients undergoing open abdominal aortic aneurysm (AAA) repair. Dopamine has been frequently used in these patients to prevent AKI. We aimed to clarify the relationship between intraoperative dopamine infusion and postoperative AKI in patients undergoing open AAA repair.

Methods

We analyzed 294 patients who underwent open AAA repair at a single tertiary center from 2009 to 2018, retrospectively. The primary outcome was the incidence of postoperative AKI, determined by the Kidney Disease Improving Global Outcomes definition, after open AAA repair. Secondary outcomes included survival outcome, hospital and intensive care unit length of stay, and postoperative renal replacement therapy (RRT).

Results

Postoperative AKI occurred in 21.8% (64 out of 294 patients) The risk of postoperative AKI by intraoperative dopamine infusion was greater after adjusting for risk factors (odds ratio [OR] 2.56; 95% confidence interval [CI], 1.09–5.89; P = 0.028) and after propensity score matching (OR 3.22; 95% CI 1.12–9.24; P = 0.030). On the contrary, intraoperative norepinephrine use was not associated with postoperative AKI (use vs. no use; 19.3 vs. 22.4%; P = 0.615). Patients who used dopamine showed higher requirement for postoperative RRT (6.8 vs. 1.2%; P = 0.045) and longer hospital length of stay (18 vs. 16 days, P = 0.024).

Conclusions

Intraoperative dopamine infusion was associated with more frequent postoperative AKI, postoperative RRT, and longer hospital length of stay in patients undergoing AAA repair, when compared to norepinephrine. Further prospective randomized clinical trial may be necessary for this topic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01624-6.

A procedure for determining subject-specific pulse oxygen saturation response

The oxyhemoglobin dissociation curve describes the relationship between the partial pressure of oxygen and the percent of hemoglobin saturated with oxygen and varies with chemical and physical factors that differ for every patient. If variability could be determined, patient-specific oxygen therapy could be administered. We have developed a procedure for characterizing variations in the oxygen dissociation curve. The purpose of this study was to validate this procedure in surgical patients. The procedure uses an automated system to alter oxygen therapy during surgery, within safe operational levels, and fit to Hill's equation non-invasive measurements of end-tidal oxygen and peripheral pulse oxygen saturation. The best-fit parameters for the Hill equation, estimated by iterative least squares, provide an apparent dissociation curve, meaningful of the patient-specific pulse oximeter response. Thirty-nine patients participated in this study. Using patient-specific parameter values increases correlation when compared with standard values. The procedure improved the model fit of patient saturation values significantly in 19 patients. This paper has demonstrated a procedure for determining patient-specific pulse oximeter response. This procedure determined best-fit parameters resulting in a significantly improved fit when compared with standard values. These best-fit parameters increased the coefficient of determination R² in all cases. Graphical Abstract This patient-specific procedure improves fit significantly compared to standard estimates.

Evaluation and application of a method for estimating nasal end-tidal O2 fraction while administering supplemental O2

This paper describes a method for estimating the oxygen enhanced end-tidal fraction of oxygen (F_etO_e), the end-tidal fraction of oxygen (F_etO₂) that is raised by administering supplemental oxygen. The paper has two purposes: the first is to evaluate the method's accuracy on the bench and in volunteers; the second purpose is to demonstrate how to apply the method to compare two techniques of oxygen administration. The method estimates F_etO_e by analyzing expired oxygen as oxygen washes out of the lung. The method for estimating F_etO_e was first validated using a bench simulation in which tracheal oxygen was measured directly. Then it was evaluated in 30 healthy volunteers and compared to the bench simulation. Bland-Altman analysis compared calculated and observed F_etO_e/F_etO₂ measurements. After the method was evaluated, it was implemented to compare the F_etO_e obtained when administering oxygen using two different techniques (pulsed and continuous flow). A total of eighteen breath washout conditions were evaluated on the bench. F_etO_e estimates and tracheal F_etO₂ had a mean difference of - 0.016 FO₂ with 95% limits of agreement from - 0.048 to 0.016 FO₂. Thirteen breath washouts per volunteer were analyzed. Extrapolated and observed F_etO₂ had a mean difference of - 0.001 FO₂ with 95% limits of agreement from - 0.006 to 0.004 FO₂. Pulsed flow oxygen (PFO) achieved the same F_etO_e values as continuous flow oxygen (CFO) using 32.1% ± 2.27% (mean ± SD) of the CFO rate. This paper has demonstrated that the method estimates F_etO₂ enhanced by administering supplemental oxygen with clinically insignificant differences. This paper has also shown that PFO can obtain F_etO₂ similar to CFO using approximately one-third of the oxygen volume. After evaluating this method, we conclude that the method provides useful estimates of nasal F_etO₂ enhanced by supplemental oxygen administration.

Prevention of Cardiac Surgery-Associated Acute Kidney Injury

Numerous strategies have been evaluated to prevent early CSA-AKI. Although correction of hemodynamic problems is paramount, there are no clinical studies that compare different hemodynamic management or monitoring strategies with regard to their effect on kidney function. Pharmacologic strategies including diuretics, different classes of vasodilators and drugs with anti-inflammatory effects such as N-acetyl-cysteine, do not appear to be effective. Most of the studies are underpowered and use physiological rather than clinical endpoints. Further trials are warranted with fenoldopam and nesiritide (rhBNP). Observational and underpowered randomized studies show beneficial renal effects of off-pump technique and avoidance of aortic manipulation. There is very limited evidence for preoperative fluid loading and preemptive RRT. Potentially nephrotoxic agents should be used with caution in patients at risk of CSA-AKI. Tranexamic acid or aminocaproic acid should be preferred over aprotinin. No pharmacologic intervention has been adequately tested in the prevention of late CSA-AKI. A single-center study, including a predominance of patients after cardiac surgery, showed a decrease of kidney injury with tight glycemic control.

Renal Insufficiency After Cardiac Surgery

The new millennium ushered in a number of changes in cardiac surgery. Off-pump coronary artery bypass surgery became technically easier so that multivessel surgery became less of a challenge and cardiologists were supplied with new catheters that accessed lesions that were previously thought of as being unapproachable. New drugs were introduced that made the management of heart failure patients feasible on an outpatient basis, and new devices extend the bridging period to transplantation. However, these advances have not necessarily been attended by significant improvements in outcome, possibly because the less challengng a procedure becomes, the sicker the patients that can be managed. This observation is particularly true with the incidence and outcome of renal failure after cardiac surgery. Bypass factors have been manipulated without much effect, and the traditional drugs that were found to increase renal blood flow in animal experiments did not translate into clinical improvement in renal outcome. Recent research has given us insight into the pathophysiology of ischemic acute renal failure, and it has been found that the paradigm was not as simple as previously thought, possibly accounting for the failure of the more traditional renal drugs (dopamine, mannitol and diuretics). However, these new insights open up the possibility of novel targets for renal protection and repair.

Acute kidney injury following cardiac surgery: current understanding and future directions

Acute kidney injury (AKI) complicates recovery from cardiac surgery in up to 30 % of patients, injures and impairs the function of the brain, lungs, and gut, and places patients at a 5-fold increased risk of death during hospitalization. Renal ischemia, reperfusion, inflammation, hemolysis, oxidative stress, cholesterol emboli, and toxins contribute to the development and progression of AKI. Preventive strategies are limited, but current evidence supports maintenance of renal perfusion and intravascular volume while avoiding venous congestion, administration of balanced salt as opposed to high-chloride intravenous fluids, and the avoidance or limitation of cardiopulmonary bypass exposure. AKI that requires renal replacement therapy occurs in 2–5 % of patients following cardiac surgery and is associated with 50 % mortality. For those who recover from renal replacement therapy or even mild AKI, progression to chronic kidney disease in the ensuing months and years is more likely than for those who do not develop AKI. Cardiac surgery continues to be a popular clinical model to evaluate novel therapeutics, off-label use of existing medications, and nonpharmacologic treatments for AKI, since cardiac surgery is fairly common, typically elective, provides a relatively standardized insult, and patients remain hospitalized and monitored following surgery. More efficient and time-sensitive methods to diagnose AKI are imperative to reduce this negative outcome. The discovery and validation of renal damage biomarkers should in time supplant creatinine-based criteria for the clinical diagnosis of AKI.

Major publications in the critical care pharmacotherapy literature: January-December 2013

PURPOSE

Ten recently published articles with important implications for critical care pharmacotherapy are summarized.

SUMMARY

The Critical Care Pharmacotherapy Literature Update (CCPLU) group is a national assembly of experienced intensive care unit (ICU) pharmacists across the United States. Group members monitor 25 peer-reviewed journals on an ongoing basis to identify literature relevant to pharmacy practice in the critical care setting. After evaluation by CCPLU group members, selected articles are chosen for summarization and distribution to group members nationwide based on (1) applicability to critical care practice, (2) relevance to pharmacy practitioners, and (3) quality of evidence or research methodology. Hundreds of relevant articles were evaluated by the group during the period January-December 2013, of which 98 were summarized and disseminated nationally to CCPLU group members. Among those 98 publications, 10 deemed to be of particularly high utility to critical care practitioners were included in this review. The 10 articles address topics such as rapid lowering of blood pressure in patients with intracranial hemorrhage, adjunctive therapy to prevent renal injury due to acute heart failure, triple-drug therapy to improve neurologic outcomes after cardiac arrest, and continuous versus intermittent infusion of β-lactam antibiotics in severe sepsis.

CONCLUSION

There were many important additions to the critical care pharmacotherapy literature in 2013, including an updated guideline on the management of myocardial infarction and reports on advances in research focused on improving outcomes in patients with stroke or cardiac arrest and preventing the spread of drug-resistant pathogens in the ICU.

Peripheral chemoreceptor control of cardiovascular function at rest and during exercise in heart failure patients

Peripheral chemoreceptor activity/sensitivity is enhanced in chronic heart failure (HF), and sensitivity is linked to greater mortality. This study aimed to determine the role of the peripheral chemoreceptor in cardiovascular control at rest and during exercise in HF patients and controls. Clinically stable HF patients (n = 11; ejection fraction: 39 ± 5%) and risk-matched controls (n = 10; ejection fraction: 65 ± 2%) performed randomized trials with or without dopamine infusion (2 μg·min(-1)·kg(-1)) at rest and during 40% maximal voluntary contraction handgrip (HG) exercise, and a resting trial of 2 min of inspired 100% oxygen. Both dopamine and hyperoxia were used to inhibit the peripheral chemoreceptor. At rest in HF patients, dopamine decreased ventilation (P = 0.02), decreased total peripheral resistance index (P = 0.003), and increased cardiac and stroke indexes (P ≤ 0.01), yet there was no effect of dopamine on these variables in controls (P ≥ 0.7). Hyperoxia lowered ventilation in HF (P = 0.01), but not in controls (P = 0.9), indicating suppression of the peripheral chemoreceptors in HF. However, no decrease of total peripheral resistance index was observed in HF. As expected, HG increased heart rate, ventilation, and brachial conductance of the nonexercising arm in controls and HF patients. During dopamine infusion, there were no changes in mean arterial pressure, heart rate, or ventilation responses to HG in either group (P ≥ 0.26); however, brachial conductance increased with dopamine in the control group (P = 0.004), but decreased in HF (P = 0.02). Our findings indicate that the peripheral chemoreceptor contributes to cardiovascular control at rest in HF patients and during exercise in risk-matched controls.

Interventions for protecting renal function in the perioperative period

BACKGROUND

Various methods have been used to try to protect kidney function in patients undergoing surgery. These most often include pharmacological interventions such as dopamine and its analogues, diuretics, calcium channel blockers, angiotensin-converting enzyme (ACE) inhibitors, N-acetyl cysteine (NAC), atrial natriuretic peptide (ANP), sodium bicarbonate, antioxidants and erythropoietin (EPO).

OBJECTIVES

This review is aimed at determining the effectiveness of various measures advocated to protect patients' kidneys during the perioperative period.We considered the following questions: (1) Are any specific measures known to protect kidney function during the perioperative period? (2) Of measures used to protect the kidneys during the perioperative period, does any one method appear to be more effective than the others? (3) Of measures used to protect the kidneys during the perioperative period,does any one method appear to be safer than the others?

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 2, 2012), MEDLINE (Ovid SP) (1966 to August 2012) and EMBASE (Ovid SP) (1988 to August 2012). We originally handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery) (1985 to 2004). However, because these journals are properly indexed in MEDLINE, we decided to rely on electronic searches only without handsearching the journals from 2004 onwards.

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery for which a treatment measure was used for the purpose of providing renal protection during the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 72 studies for inclusion in this review. Two review authors extracted data from all selected studies and entered them into RevMan 5.1; then the data were appropriately analysed. We performed subgroup analyses for type of intervention, type of surgical procedure and pre-existing renal dysfunction. We undertook sensitivity analyses for studies with high and moderately good methodological quality.

MAIN RESULTS

The updated review included data from 72 studies, comprising a total of 4378 participants. Of these, 2291 received some form of treatment and 2087 acted as controls. The interventions consisted most often of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, NAC, ANP, sodium bicarbonate, antioxidants and EPO or selected hydration fluids. Some clinical heterogeneity and varying risk of bias were noted amongst the studies, although we were able to meaningfully interpret the data. Results showed significant heterogeneity and indicated that most interventions provided no benefit.Data on perioperative mortality were reported in 41 studies and data on acute renal injury in 44 studies (all interventions combined). Because of considerable clinical heterogeneity (different clinical scenarios, as well as considerable methodological variability amongst the studies), we did not perform a meta-analysis on the combined data.Subgroup analysis of major interventions and surgical procedures showed no significant influence of interventions on reported mortality and acute renal injury. For the subgroup of participants who had pre-existing renal damage, the risk of mortality from 10 trials (959 participants) was estimated as odds ratio (OR) 0.76, 95% confidence interval (CI) 0.38 to 1.52; the risk of acute renal injury (as reported in the trials) was estimated from 11 trials (979 participants) as OR 0.43, 95% CI 0.23 to 0.80. Subgroup analysis of studies that were rated as having low risk of bias revealed that 19 studies reported mortality numbers (1604 participants); OR was 1.01, 95% CI 0.54 to 1.90. Fifteen studies reported data on acute renal injury (criteria chosen by the individual studies; 1600 participants); OR was 1.03, 95% CI 0.54 to 1.97.

AUTHORS' CONCLUSIONS

No reliable evidence from the available literature suggests that interventions during surgery can protect the kidneys from damage. However, the criteria used to diagnose acute renal damage varied in many of the older studies selected for inclusion in this review, many of which suffered from poor methodological quality such as insufficient participant numbers and poor definitions of end points such as acute renal failure and acute renal injury. Recent methods of detecting renal damage such as the use of specific biomarkers and better defined criteria for identifying renal damage (RIFLE (risk, injury, failure, loss of kidney function and end-stage renal failure) or AKI (acute kidney injury)) may have to be explored further to determine any possible benefit derived from interventions used to protect the kidneys during the perioperative period.

Acute kidney injury clinical trial design: old problems, new strategies

Apart from supportive dialysis there are no universally accepted interventions in acute kidney injury (AKI). We have summarized the outcomes of all published randomized, placebo-controlled studies of non-dialysis treatment of AKI. Forty-nine trials were identified, only one of which was in a paediatric population. Sixteen trials had positive outcomes; these trials are not comparable in terms of methodology used or outcomes assessed, and they share many of the problems of the negative trials. We discuss the flaws in clinical trial design that have contributed to poor or uncertain outcomes and propose minimum requirements for future trials. In particular, future trials should incorporate biomarkers specific to the etiology of the AKI, and treatment should match the phase of injury.

Pharmacological therapies for the prevention of acute kidney injury following cardiac surgery: a systematic review

Post-cardiac surgery acute kidney injury (AKI) is common and is associated with a significant increase in morbidity and mortality. We aimed to systematically review randomised trials that assessed the renoprotective utility of pharmacological agents in patients undergoing cardiac surgery. We searched PubMed, Embase and the Cochrane Central Register of Controlled Trials for randomised controlled trials comparing renoprotective pharmacological interventions with control in adult patients undergoing cardiac surgery with cardiopulmonary bypass. We extracted data for mortality, need for renal replacement therapy (RRT), incidence of AKI, and creatinine clearance at 24-48 h. About 49 randomised controlled trials involving 4605 patients were included. Pharmacological interventions included dopamine, fenoldopam, calcium channel antagonists, natriuretic peptides, diuretics, and N-acetylcysteine. Most trials were of poor quality, with small sample sizes, under-reporting of randomisation procedure, allocation concealment and method of blinding. No pharmacological intervention significantly reduced mortality. Fenoldopam and Atrial Natriuretic Peptide (ANP) reduced the need for renal replacement therapy by 5% (NNT 20, 95% CI 11.3, 83.0) and 3.5% (NNT 29, 95% CI 17.1, 84.4), respectively. Brain Natriuretic Peptide resulted in a 10% reduction in the incidence of AKI (NNT 11, 95% CI 6.2, 32.0). Dopamine caused a significant reduction in creatinine clearance (-4.26 ml/min, 95% CI -7.14, -1.39). The quality of studies that have assessed pharmacological renoprotective agents in cardiac surgery is generally poor. Fenoldopam, ANP and BNP show evidence of renoprotection. Randomised studies evaluating the effect of novel renoprotective agents that are powered to detect clinically relevant differences in outcomes are required.

Novel aspects of pharmacological therapies for acute renal failure

Acute renal failure (ARF) comprises several syndromes that are associated with a sudden decrease in renal function. ARF is common among critically ill patients, is typically multifactorial and is of great prognostic significance. Indeed, even moderate changes in renal function significantly add to the morbidity and worsen mortality associated with ARF. Recent definitions, namely the renal Risk, Injury, Failure, Loss of renal function and End-stage kidney disease (RIFLE) classification or Acute Kidney Injury Network (AKIN) criteria, which incorporate the levels of oliguria in addition to fractional serum creatinine elevation, are important because the magnitude of kidney injury according to those definitions correlates very well with both short- and long-term patient survival. However, preventive strategies are most effective when started before oliguria or elevated serum creatinine is detectable, as those criteria already reflect established renal tubular cell injury. New biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty acid binding protein (L-FABP) or kidney injury molecule-1 (KIM-1) that increase prior to the serum creatinine elevation are promising and have been proven to be useful in this regard in a few clinical trials. In addition, genetic profiling may define patients at risk earlier and help to individualize preventive strategies. Well established strategies include limiting dehydration and hypotension by the use of intravenous isotonic fluids at an optimal and individualized rate, as well as avoiding exposure to nephrotoxins, which include aminoglycosides, amphotericin or non-ionic contrast. Generally accepted and evidence-based pharmacological preventive or therapeutic options have not yet been established, although many drugs (e.g. renal vasodilators, diuretics and HMG-CoA reductase inhibitors [statins]) have been tested. New promising agents interfere with the apoptotic signalling that can occur in the setting of toxin exposure or ischaemia-reperfusion injury, limit inflammatory responses or modulate endothelial cell activation. In the future, these new approaches will enable us to extend our therapeutic repertoire.

Prevention and treatment of acute kidney injury in patients undergoing cardiac surgery: a systematic review

BACKGROUND

Acute kidney injury (AKI) is common in patients undergoing cardiac surgery and is associated with a high rate of death, long-term sequelae and healthcare costs. We conducted a systematic review of randomized controlled trials for strategies to prevent or treat AKI in cardiac surgery.

METHODS

We screened Medline, Scopus, Cochrane Renal Library, and Google Scholar for randomized controlled trails in cardiac surgery for prevention or treatment of AKI in adults.

RESULTS

We identified 70 studies that contained a total of 5,554 participants published until November 2008. Most studies were small in sample size, were single-center, focused on preventive strategies, and displayed wide variation in AKI definitions. Only 26% were assessed to be of high quality according to the Jadad criteria. The types of strategies with possible protective efficacy were dopaminergic agents, vasodilators, anti-inflammatory agents, and pump/perfusion strategies. When analyzed separately, dopamine and N-acetylcysteine did not reduce the risk for AKI.

CONCLUSIONS

This summary of all the literature on prevention and treatment strategies for AKI in cardiac surgery highlights the need for better information. The results advocate large, good-quality, multicenter studies to determine whether promising interventions reliably reduce rates of acute renal replacement therapy and mortality in the cardiac surgery setting.

Dopamine increases renal oxygenation: a clinical study in post-cardiac surgery patients

BACKGROUND

Imbalance of the renal medullary oxygen supply/demand relationship can cause ischaemic acute renal failure (ARF). The use of dopamine for prevention/treatment of ischaemic ARF has been questioned. It has been suggested that dopamine may increase renal oxygen consumption (RVO(2)) due to increased solute delivery to tubular cells, which may jeopardize renal oxygenation. Information on the effects of dopamine on renal perfusion, filtration and oxygenation in man is, however, lacking. We evaluated the effects of dopamine on renal blood flow (RBF), glomerular filtration rate (GFR), RVO(2) and renal O(2) demand/supply relationship, i.e. renal oxygen extraction (RO(2)Ex).

METHODS

Twelve uncomplicated, mechanically ventilated and sedated post-cardiac surgery patients with pre-operatively normal renal function were studied. Dopamine was sequentially infused at 2 and 4 ug/kg/min. Systemic haemodynamics were evaluated by a pulmonary artery catheter. Absolute RBF was measured using two independent techniques: by the renal vein thermodilution technique and by infusion clearance of paraaminohippuric acid (PAH), with a correction for renal extraction of PAH. The filtration fraction (FF) was measured by the renal extraction of (51)Cr-EDTA.

RESULTS

Neither GFR, tubular sodium reabsorption nor RVO(2) was affected by dopamine, which increased RBF (45-55%) with both methods, decreased renal vascular resistance (30-35%), FF (21-26%) and RO(2)Ex (28-34%). The RBF/CI ratio increased with dopamine. Dopamine decreased renal PAH extraction, suggestive of a flow distribution to the medulla.

CONCLUSIONS

In post-cardiac surgery patients, dopamine increases the renal oxygenation by a pronounced renal pre-and post-glomerular vasodilation with no increases in GFR, tubular sodium reabsorption or renal oxygen consumption.

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

BACKGROUND

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

HYPOTHESIS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine and its analogues, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes that included renal failure and mortality as well as changes in renal function tests, such as urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 2), MEDLINE (1966 to June, 2007), and EMBASE (1988 to June, 2007); and handsearched six journals (Anesthesia and Analgesia, Anesthesiology, Annals of Surgery, British Journal of Anaesthesia, Journal of Thoracic and Cardiovascular Surgery, and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adults undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 53 studies for inclusion in this review. As well as data analysis from all the studies, we performed subgroup analysis for type of intervention, type of surgical procedure, and pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high and moderately good methodological quality.

MAIN RESULTS

The review included data from 53 studies, comprising a total of 2327 participants. Of these, 1293 received some form of treatment and 1034 acted as controls. The interventions mostly consisted of different pharmaceutical agents, such as dopamine and its analogues, diuretics, calcium channel blockers, ACE inhibitors, or selected hydration fluids. The results indicated that certain interventions showed minimal benefits. All the results suffered from significant heterogeneity. Hence we cannot draw conclusions about the effectiveness of these interventions in protecting patients' kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from the available literature to suggest that interventions during surgery can protect the kidneys from damage. There is a need for more studies with high methodological quality. One particular area for further study may be patients with pre-existing renal dysfunction undergoing surgery.

Renal function and dysfunction

Recent publications regarding perioperative renal dysfunction provide a 'potpourri' of topics worthy of discussion. The risk of perioperative renal dysfunction is higher in patients with heart failure, but other pre-existing conditions, such as genetic polymorphism, may have prognostic implications. Evaluation of renal risk and protective interventions are discussed for a number of specific operative entities, including cardiac surgery (with or without cardiopulmonary bypass), aortic surgery and renal revascularization. New publications on a wide variety of nephrotoxic insults are presented, including antifibrinolytic agents, obstructive jaundice, prostaglandin inhibitors, cyclosporine A, radiocontrast dyes and volatile anesthetic agents. Renal transplantation is discussed as a specific entity. Finally, we discuss recent papers describing outcome in patients in chronic renal failure undergoing cardiac surgery.

Preoxygenation with the Mapleson D system requires higher oxygen flows than Mapleson A or circle systems

PURPOSE

This study investigates the efficacy of preoxygenation with Mapleson A and Mapleson D breathing systems vs the circle system with CO2 absorber.

METHODS

Thirteen healthy volunteers underwent tidal volume breathing for three minutes via facemask using Mapleson A, Mapleson D breathing systems or the circle system with CO2 absorber while breathing 100% O2 at flow rates of 5 L.min-1 and 10 L.min-1. Each volunteer acted as his/her own control by going through each of six preoxygenation protocols in random order. Fractional end-tidal O2 concentration (FETO2) was measured at 30-sec intervals. The results were compared among the three anesthesia systems at the two fresh gas flow rates.

RESULTS

At a fresh gas flow rate of 5 L.min-1, the Mapleson A and circle systems achieved F(ETO2) values of 90.8+/-1.4% and 90.0+/-1.1%, respectively, compared with the lower F(ETO2) (81.5+/-6.3%, P<0.05), achieved with the Mapleson D system. When breathing O2 at 10 L.min-1, the F(ETO2) values after three minutes were similar with the Mapleson A, circle, and Mapleson D breathing systems (91.8+/-2.3%, 91.2+/-1.7%, 90.6+/-2.7%, respectively).

CONCLUSION

When using the Mapleson A and the circle systems for preoxygenation, an oxygen flow rate of 5 L.min-1 can adequately preoxygenate the patient within three minutes, while an oxygen flow of 10 L.min-1 is required to achieve a similar fractional end-tidal O2 concentration with the Mapleson D system.

Low-dose dopamine: a physiologically based review

BACKGROUND

In an attempt to prevent or alter the course of acute renal failure, many surgeons continue to use low-dose dopamine. This article critically reviews the physiologic reasons why low-dose dopamine is not clinically efficacious.

METHODS

A critical review of English language literature.

RESULTS

The effect of dopamine on renal blood flow remains controversial. If dopamine does increase renal blood flow, the vascular anatomy of the kidney would limit its effectiveness. Rather than improving renal function, dopamine has been shown to impair renal oxygen kinetics, inhibit feedback systems that protect the kidney from ischemia, and may worsen tubular injury. Dopamine has not been proven useful in the prevention or alteration of the course of acute renal failure as a result of heart failure, cardiac surgery, abdominal aortic surgery, sepsis, and transplantation. Dopamine has been associated with multiple complications involving the cardiovascular, pulmonary, gastrointestinal, endocrine, and immune systems.

CONCLUSIONS

Based on the anatomy and physiology of the kidney, low-dose dopamine would not be expected to improve renal failure and this has been demonstrated by the lack of efficacy in clinical trials.

'Low-dose' dopamine worsens renal perfusion in patients with acute renal failure

'Low-dose' dopamine is frequently used in intensive care units (ICU) for its presumed renoprotective effects, but prospective and retrospective studies have so far not proven prevention or amelioration of renal injury. Data on renal perfusion following dopamine infusion are limited. In order to circumvent the problem of patient heterogeneity in the ICU setting, we used a crossover design in a prospective, double-blind randomized controlled study to investigate the effect of 'low-dose' dopamine on renal resistance indices, as determined by Doppler ultrasound. Forty patients, 10 without and 30 with acute renal failure (ARF, defined as doubling of baseline creatinine or an increase above 2 mg/dl), were included. Dopamine (2 mug/kg min) or placebo was given intravenously in alternating sequence for four subsequent periods of 60 min, starting randomly with either dopamine or placebo. Resistive (RI) and pulsatility index (PI) were closely correlated, positively related to serum creatinine values at baseline and highly reproducible during the two paired infusion periods. Dopamine reduced renal vascular resistance in patients without ARF (median RI/PI from 0.70 to 0.65/1.20 to 1.07, P<0.01) but increased resistance indices in patients with ARF (median RI/PI from 0.77 to 0.81/1.64 to 1.79, P<0.01) in the absence of effects on systemic hemodynamics. Subgroup analysis of patients with ARF revealed that dopamine induced renal vasoconstriction above 55 years (n=22) and in patients not receiving norepinephrine (n=20). In conclusion 'low-dose' dopamine can worsen renal perfusion in patients with ARF, which adds to the rationale for abandoning the routine use of 'low-dose' dopamine in critically ill patients.

Renal failure secondary to acute tubular necrosis: epidemiology, diagnosis, and management

Acute tubular necrosis (ATN) is a form of acute renal failure (ARF) that is common in hospitalized patients. In critical care units, it accounts for about 76% of cases of ARF. Despite the introduction of hemodialysis > 30 years ago, the mortality rates from ATN in hospitalized and ICU patients are about 37.1% and 78.6%, respectively. The purpose of this review is to discuss briefly the cause, diagnosis, and epidemiology of ARF, and to review in depth the clinical trials performed to date that have examined the influence of growth factors, hormones, antioxidants, diuretics, and dialysis. In particular, the role of the dialysis modality, dialyzer characteristics, and dosing strategies are discussed.

Interventions for protecting renal function in the perioperative period

BACKGROUND

A number of methods have been used to try to protect kidney function in patients undergoing surgery. These include the administration of dopamine, diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors and hydration fluids.

OBJECTIVES

For this review, we selected randomized controlled trials, which employed different methods to protect renal function during the perioperative period. In examining these trials, we looked at outcomes such as renal failure and mortality, as well as changes in the renal function tests, including urine output, creatinine clearance, free water clearance, fractional excretion of sodium and renal plasma flow.

SEARCH STRATEGY

We searched the Cochrane Central register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to 2004) and EMBASE (1988 to 2004) and hand searched six journals (British Journal of Anaesthesia; Anesthesia and Analgesia; Anesthesiology; Annals of Surgery; Journal of Thoracic and Cardiovascular Surgery and Journal of Vascular Surgery).

SELECTION CRITERIA

We selected all randomized controlled trials in adult population undergoing surgery where a treatment measure was used for the purpose of renal protection in the perioperative period.

DATA COLLECTION AND ANALYSIS

We selected 37 studies for inclusion in this review. As well as analysis of the data from all the studies, we also performed subgroup analysis for type of interventions, types of surgical procedures and those with pre-existing renal dysfunction. We undertook sensitivity analysis on studies with high methodological quality.

MAIN RESULTS

The review included data from 37 studies, comprising a total of 1227 patients. Of these, 658 received some form of treatment and 569 acted as controls. The interventions were mostly employing different pharmaceutical agents such as dopamine, diuretics, calcium channel blockers. ACE inhibitors or selected hydration fluids. The results indicated that certain interventions showed some benefits, but all the results suffered from significant heterogeneity. Hence we can draw no conclusions about the effectiveness of these interventions in protecting the kidneys during surgery.

AUTHORS' CONCLUSIONS

There is no reliable evidence from available literature to suggest that interventions during surgery can protect the kidneys from damage. However, there is a need for more studies of high methodological quality. One particular area for further studies may be on patients with pre-existing renal dysfunction undergoing surgery.

Fenoldopam mesylate and renal function in patients undergoing liver transplantation: a randomized, controlled pilot trial

To test the relative effects on serum creatinine (CRE), blood urea nitrogen (BUN), and urine output of small-dose dopamine and fenoldopam in patients undergoing liver transplantation, we randomized 43 patients to 1 of 2 continuous infusions over 48 h, starting with anesthesia induction: fenoldopam, 0.1 microg . kg(-1) . min(-1) or dopamine, 2 microg . kg(-1) . min(-1). We used predetermined hemodynamic and intravascular volume goals (intrathoracic blood volume index 800-1000 mL/m(2), extravascular lung water index <7 mL/kg) to manage patients with an algorithm for use of mannitol and furosemide to maintain urine output >1 mL . kg(-1) . h(-1). At postoperative day 3, the median CRE increase was 0.2 mg/dL (interquartile range [IQR] -0.2-0.5) with fenoldopam and 0.5 mg/dL (IQR 0.3-0.9, P = 0.004) in the dopamine group. The BUN increase was median 2 mg/dL (IQR -2-8) versus 8.5 mg/dL (IQR 5-12, P = 0.01), respectively, with fenoldopam versus dopamine. Urine output was similar; however, significantly fewer fenoldopam patients required furosemide compared with dopamine patients (median 1 [IQR 0-3] versus 3 [IQR 2-4], respectively, P = 0.003). The hemodynamic effects of dopamine and fenoldopam were similar. Compared with dopamine, in the setting of liver transplantation, fenoldopam is associated with better CRE and BUN values.

Bench-to-bedside review: Inotropic drug therapy after adult cardiac surgery -- a systematic literature review

Many adult patients require temporary inotropic support after cardiac surgery. We reviewed the literature systematically to establish, present and classify the evidence regarding choice of inotropic drugs. The available evidence, while limited in quality and scope, supports the following observations; although all β-agonists can increase cardiac output, the best studied β-agonist and the one with the most favourable side-effect profile appears to be dobutamine. Dobutamine and phosphodiesterase inhibitors (PDIs) are efficacious inotropic drugs for management of the low cardiac output syndrome. Dobutamine is associated with a greater incidence of tachycardia and tachyarrhythmias, whereas PDIs often require the administration of vasoconstrictors. Other catecholamines have no clear advantages over dobutamine. PDIs increase the likelihood of successful weaning from cardiopulmonary bypass as compared with placebo. There is insufficient evidence that inotropic drugs should be selected for their effects on regional perfusion. PDIs also increase flow through arterial grafts, reduce mean pulmonary artery pressure and improve right heart performance in pulmonary hypertension. Insufficient data exist to allow selection of a specific inotropic agent in preference over another in adult cardiac surgery patients. Multicentre randomized controlled trials focusing on clinical rather than physiological outcomes are needed.

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+.

Increasing Renal Blood Flow

BACKGROUND AND OBJECTIVES

Many clinicians believe that low-dose dopamine (LDD) [2 micro g/kg/min] increases renal blood flow (RBF) and medium-dose norepinephrine (MD-NE) [0.4 micro g/kg/min] decreases RBF. They also believe that MD-NE might induce mesenteric and/or coronary ischemia. In fact, the effects of these drugs on renal and vital organ blood flow are poorly understood. The aim of this study was to compare the effects of 6 h of IV LDD and MD-NE infusion on mammalian renal, coronary, mesenteric, and sagittal blood flow.

DESIGN

Randomized, controlled, experimental animal study.

SETTING

Animal laboratory of tertiary physiology institute.

SUBJECTS

Seven Merino cross sheep were studied.

MEASUREMENTS AND RESULTS

We performed a staged insertion of transit-time flow probes around ascending aorta, sagittal sinus and circumflex coronary, superior mesenteric, and left renal arteries. We then randomized these animal with long-term embedded flow probes to either 6 h of placebo (saline solution) or drugs (MD-NE at 0.4 micro g/kg/min or LDD at 2 micro g/kg/min), and performed continuous measurement of systemic pressures, cardiac output (CO), and flow to vital organs. We also sampled blood and urine for the measurement of lactate, creatinine, and creatinine clearances at preset intervals.

RESULTS

Compared to placebo, LDD did not affect systemic hemodynamics. However, it increased mean RBF by 20% (267.3 +/- 87.6 mL/min vs 222.0 +/- 74.4 mL/min, p = 0.028) without a detectable effect on other vital regional circulations. MD-NE, however, increased mean arterial pressure (101.0 +/- 8.3 mL/min vs 84.2 +/- 5.2 mL/min, p = 0.018) [mean +/- SD] and CO (4.93 +/- 1.45 L/min vs 3.81 +/- 0.57 L/min, p = 0.028). It also increased coronary blood flow (36.0 +/- 15.7 mL/min vs 23.0 +/- 10.7 mL/min, p = 0.018) and RBF (286.5 +/- 79.0 mL/min vs 222.0 +/- 74.4 mL/min, p = 0.018). MD-NE had no detectable effect on mesenteric or sagittal sinus flow. LDD infusion increased urine output, but did not change creatinine clearance. MD-NE infusion increased urine output significantly more than LDD but not creatinine clearance.

CONCLUSIONS

Both LDD (2 micro g/kg/min) and MD-NE (0.4 micro g/kg/min) increased RBF and urine output. However, the effect of MD-NE was more pronounced. LDD did not affect other vital organ flows, but MD-NE increased coronary blood flow without any changes in mesenteric and sagittal sinus blood flow.

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.

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.

Mannitol and dopamine in patients undergoing cardiopulmonary bypass: a randomized clinical trial

In this prospective, randomized, placebo-controlled, double-blinded study, we determined the effects of two commonly used adjuncts, mannitol and dopamine, on beta(2)-microglobulin (beta(2)M) excretion rates in patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass (CPB). beta(2)M excretion rate has been described as a sensitive marker of proximal renal tubular function. One-hundred patients with a preoperative serum creatinine level <or=1.5 mg/dL were prospectively randomized into 4 groups: 1). placebo, 2). mannitol 1 g/kg added to the CPB prime, 3). dopamine 2 microg kg(-1x. min(-1) from the induction of anesthesia to 1 h post-CPB, or 4). mannitol plus dopamine. The primary outcome measure was beta(2)M excretion rate at 1 h post-CPB. Secondary outcome measures included beta(2)M excretion rate at 6 and 24 h post-CPB; urinary flow rate and creatinine clearance at 1, 6, and 24 h post-CPB; and the highest postoperative serum creatinine level. Length of intensive care stay and hospitalization, as well as adverse events, were also considered secondary outcomes. Dopamine significantly increased beta(2)M excretion rate at 1 h post-CPB (2.48 +/- 3.61 microg/min) compared with placebo (0.59 +/- 1.04 microg/min; P = 0.001). This effect was not ameliorated by the addition of mannitol (beta(2)M excretion rate, 2.05 +/- 2.77 microg/min; P = 0.007 compared with placebo). beta(2)M excretion rate was similar in patients given placebo or mannitol alone (P = 0.831). Rather than being a protective drug in the setting of CPB, dopamine alone or in combination with mannitol increases beta(2)M excretion rate, which may be a measure of renal tubular dysfunction. The clinical implications of this increase and whether it is also seen in patients with established renal dysfunction undergoing CPB require additional investigation.

IMPLICATIONS

In many clinical settings, an increased beta-2-microglobulin (beta(2)M) excretion rate indicates renal tubular injury. In this cardiopulmonary bypass (CPB) study, a dopamine infusion (alone or with mannitol) resulted in an increased beta(2)M excretion rate. It is unclear whether this dopamine-related increase implies renal injury after CPB, and further investigations are required to examine the mechanism/clinical relevance of this observation.

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.

Diltiazem may preserve renal tubular integrity after cardiac surgery

PURPOSE

To evaluate the influence of dopamine and diltiazem on renal function and markers for acute renal failure, including urinary alpha-glutathion s-transferase (alpha-GST), alpha-1-microglobulin (alpha(1)-MG) and N-acetyl-ss-glucosaminidase (ss-NAG) after extracorporeal circulation.

METHODS

In a randomized, placebo-controlled, double-blind trial we evaluated the efficacy of dopamine (2.5 micro g x kg(-1) x min(-1)), diltiazem (2 micro g x kg(-1) x min(-1)) or placebo administered over 48 hr postoperatively to maintain renal tubular integrity in 60 elective cardiac surgery patients. alpha-GST, alpha(1)-MG, ss-NAG, and creatinine clearance were measured from urine collected during surgery (T0), the first four hours (T1), 24 hr (T2) and 48 hr (T3) postoperatively.

RESULTS

Cumulative urine output in the diltiazem group (9.0 +/- 2.8 L) increased significantly compared with placebo (7.0 +/- 1.6 L), but not compared with dopamine (7.8 +/- 1.8 L). Creatinine clearance showed no significant intergroup differences. In all groups alpha(1)-MG increased from T0 to T3, but we found no significant intergroup differences. alpha-GST increased significantly from T0 to T3 in the placebo (2.1 +/- 1.8 to 11.4 +/- 8.6 micro g x L(-1)) and in the dopamine groups (2.7 +/- 1.8 to 13.6 +/- 14.9 micro g x L(-1)), but not in the diltiazem group (1.8 +/- 1.4 to 3.2 +/- 3.2 micro g x L(-1)). Forty-eight hours postoperatively alpha-GST was significantly lower in the diltiazem group than in both other groups.

CONCLUSIONS

Diltiazem stimulates urine output, reduces excretion of alpha-GST and ss-NAG and may be useful to maintain tubular integrity after cardiac surgery.

A case series of low-dose fenoldopam in seventy cardiac surgical patients at increased risk of renal dysfunction

OBJECTIVE

To evaluate the usefulness of low-dose fenoldopam mesylate in patients at risk of developing renal dysfunction after cardiac surgery requiring cardiopulmonary bypass.

DESIGN

A prospective, single-center, observational study.

SETTING

University teaching hospital.

PARTICIPANTS

Seventy patients scheduled for elective cardiac surgery with one or more predefined risk factors for renal dysfunction.

INTERVENTIONS

After induction of anesthesia, fenoldopam (0.03 microg/kg/min) was administered throughout surgery and into the postoperative period, until the patient was stable and weaned from all other vasoactive agents. Perioperatively, fenoldopam was also used as a second-line antihypertensive agent as required.

MEASUREMENTS AND MAIN RESULTS

No patient developed renal failure that required dialysis, whereas 7.1% (5/70) developed non-dialysis-dependent renal dysfunction. Four out of these 5 patients had 2 or more risk factors (9.5%). Higher preoperative creatinine levels, a history of hypertension, myocardial infarction within 5 days of surgery, and a preoperative diagnosis of chronic renal insufficiency were all good predictors of postoperative non-dialysis-dependent renal dysfunction. Discharge serum creatinine levels were lower than preoperative levels (1.16 +/- 0.36 mg/dL v 1.26 +/- 0.34 mg/dL, p < 0.05).

CONCLUSION

These findings suggest that renal function was preserved in patients at increased risk for renal dysfunction after cardiac surgery when low-dose fenoldopam was used in the perioperative period. However, a randomized, controlled trial is required to establish efficacy.

Dopamine therapy for patients at risk of renal dysfunction following cardiac surgery: science or fiction?

OBJECTIVES

We aimed to evaluate the renoprotective role of renal-dose dopamine on cardiac surgical patients at high risk of postoperative renal dysfunction. The latter included older patients or those with pre-existing renal disease, elevated preoperative serum creatinine (Cr), poor ventricular function, hypertension, diabetes mellitus and unstable angina requiring intravenous therapy.

METHODS

Fifty patients undergoing cardiopulmonary bypass (CPB) who fulfilled the entry criteria were prospectively randomized into two groups: Group 1 received a 'renal-dose' (3 microg kg(-1) min(-1)) dopamine infusion starting at anaesthetic induction for 48 h whilst saline infusion acted as placebo in Group 2. The anaesthetic and CPB regimes were standardized. Urinary excretion of retinol binding protein (RBP) indexed to Cr, an accurate and sensitive marker of early renal tubular damage, was assessed daily for 6 days. Additional outcome measures included daily fluid balance, blood urea and serum Cr. Statistical comparisons were made using ANOVA and Mann-Whitney U-test.

RESULTS

No significant difference was found between the groups in their age, gender, preoperative NYHA class, ejection fraction, baseline serum Cr and duration of CPB and aortic cross-clamping. Renal replacement therapy was not required in any instance. Both groups demonstrated a similar and significant rise in urinary RBP throughout the study period. Dopamine-treated patients achieved more negative average fluid balance than those on placebo (5 vs. 229 ml, P<0.05).

CONCLUSIONS

Renal-dose dopamine therapy failed to offer additional renoprotection to patients considered at increased risk of renal dysfunction after CPB.

Fenoldopam: renal and splanchnic effects in patients undergoing coronary artery bypass grafting

Impairment of renal and splanchnic perfusion during and after cardiopulmonary bypass may be responsible for acute renal failure and endotoxin-mediated systemic inflammation, respectively. We hypothesised that fenoldopam, a selective dopamine receptor agonist, would preserve renal function after cardiopulmonary bypass through its selective renal vasodilatory and natriuretic effects, and increase gastrointestinal mucosal perfusion by selective splanchnic vasodilation. We examined the effects of fenoldopam on haemodynamic parameters, creatinine clearance, fractional excretion of sodium, urine output, free water clearance and gastric mucosal pH in 31 patients undergoing elective coronary revascularisation. Patients were randomly assigned to receive continuous infusions of fenoldopam 0.1 microg x kg(-1) x min(-1) (n = 16) or placebo (n = 15). Renal parameters were measured: during a 24-h period before hospital admission, during cardiopulmonary bypass, from completion of cardiopulmonary bypass until 4 h later, from 4 to 8 h after cardiopulmonary bypass, and from 8 to 14 h after cardiopulmonary bypass. Gastric intramucosal pH was measured using a gastric tonometer before, during and after cardiopulmonary bypass. In the placebo group, but not the fenoldopam group, mean (SD) creatinine clearance decreased after separation from cardiopulmonary bypass, from 107 (36) to 71 (22) ml x min(-1) (p < 0.01) and from 107 (36) to 79 (26) ml x min(-1) (p < 0.01) for the 0-4 h and 4-8 h intervals after cardiopulmonary bypass, respectively. Changes in intramucosal pH were similar in both groups. The findings are consistent with the hypothesis that fenoldopam possesses a renoprotective effect in patients undergoing cardiopulmonary bypass.

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.

Care of the critically ill parturient: oliguria and renal failure

The incidence of acute renal failure in pregnancy has decreased. This decrease is less marked in developing countries in which resources are more scarce. The clinical diagnosis of acute renal failure is crude due to the variability of clinical signs and the late occurrence of basic biochemical abnormalities. Obstetric and gynaecological diseases are found among the traditional pre-renal, intra-renal and post-renal causes of acute renal failure. The cornerstone of management is the identification of high-risk cases and the prevention of acute renal failure by maintaining intravascular volume. The evidence for the efficacy of other prophylactic medical interventions, such as the use of loop diuretics, mannitol, low-dose dopamine and others, is poor. Management of established acute renal failure includes restoration of intravascular volume, treatment of any reversible causes, especially pregnancy complications such as pre-eclampsia, strict fluid balance and correction of any electrolyte abnormality or metabolic acidosis. Dialysis is a supportive measure until the kidneys recover.

Long-term infusion of atrial natriuretic peptide (ANP) improves renal blood flow and glomerular filtration rate in clinical acute renal failure

BACKGROUND

Short-term infusion of atrial natriuretic peptide (ANP) increases renal blood flow (RBF) and glomerular filtration rate (GFR) in patients with acute renal dysfunction. In the present study we evaluated the effects of long-term infusion (>48 h) of ANP on (RBF) and (GFR) in 11 postcardiac surgical patients requiring pharmacological circulatory support and with acute renal impairment.

METHODS

Urinary clearance of Cr-EDTA and PAH as well as central hemodynamic measurements were performed for 2-3 consecutive 30-min periods during ANP infusion (50 ng. kg-1. min-1), one hour after abrupt discontinuation of ANP and again immediately after reinstitution of ANP infusion.

RESULTS

During ANP infusion, urine flow (UF), GFR, RBF and renal vascular resistance (RVR) were 6.4+/-1.1 ml. min-1, 19.9+/-3.1 ml. min-1, 408+/-108 ml. min-1 and 0.286+/-0.054 mmHg. min. ml-1, respectively. UF, GFR and RBF decreased significantly by 28% (P<0.001), 32% (P<0.01) and 31% (P<0.05), respectively when ANP infusion was discontinued. RVR increased by 93% (P<0.05) while there was no change in filtration fraction. After reinstitution of ANP infusion, all measured renal variables returned to baseline. There was no significant correlation between the number of ANP treatment days and the percentage decrease in GFR (r=0.18) or RBF (r=0.22) during ANP withdrawal. Central hemodynamic variables were not affected by ANP withdrawal.

CONCLUSIONS

ANP infusion improves RBF and GFR in patients with acute renal impairment after cardiac surgery. This renal vasodilatory effect is maintained during a long-term infusion and seems to be hemodynamically safe.

Low-dose dopamine in patients with early renal dysfunction: a placebo-controlled randomised trial. Australian and New Zealand Intensive Care Society (ANZICS) Clinical Trials Group

BACKGROUND

Low-dose dopamine is commonly administered to critically ill patients in the belief that it reduces the risk of renal failure by increasing renal blood flow. However, these effects have not been established in a large randomised controlled trial, and use of dopamine remains controversial. We have done a multicentre, randomised, double-blind, placebo-controlled study of low-dose dopamine in patients with at least two criteria for the systemic inflammatory response syndrome and clinical evidence of early renal dysfunction (oliguria or increase in serum creatinine concentration).

METHODS

328 patients admitted to 23 participating intensive-care units (ICUs) were randomly assigned a continuous intravenous infusion of low-dose dopamine (2 microg kg(-1) min(-1)) or placebo administered through a central venous catheter while in the ICU. The primary endpoint was the peak serum creatinine concentration during the infusion. Analyses excluded four patients with major protocol violations.

FINDINGS

The groups assigned dopamine (n=161) and placebo (n=163) were similar in terms of baseline characteristics, renal function, and duration of trial infusion. There was no difference between the dopamine and placebo groups in peak serum creatinine concentration during treatment (245 [SD 144] vs 249 [147] micromol/L; p=0.93), in the increase from baseline to highest value during treatment (62 [107] vs 66 [108] micromol/L; p=0.82), or in the numbers of patients whose serum creatinine concentration exceeded 300 micromol/L (56 vs 56; p=0.92) or who required renal replacement therapy (35 vs 40; p=0.55). Durations of ICU stay (13 [14] vs 14 [15] days; p=0.67) and of hospital stay (29 [27] vs 33 [39] days; p=0.29) were also similar. There were 69 deaths in the dopamine group and 66 in the placebo group.

INTERPRETATION

Administration of low-dose dopamine by continuous intravenous infusion to critically ill patients at risk of renal failure does not confer clinically significant protection from renal dysfunction.