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

Perinatal risk factors associated with acute kidney injury severity and duration among infants born extremely preterm

BACKGROUND

We evaluated time-varying perinatal risk factors associated with early (≤7 post-natal days) and late (>7 post-natal days) severe acute kidney injury (AKI) occurrence and duration.

METHODS

A secondary analysis of Preterm Erythropoietin Neuroprotection Trial data. We defined severe AKI (stage 2 or 3) per neonatal modified Kidney Disease: Improving Global Outcomes criteria. Adjusted Cox proportional hazards models were conducted with exposures occurring at least 72 h before severe AKI. Adjusted negative binomial regression models were completed to evaluate risk factors for severe AKI duration.

RESULTS

Of 923 participants, 2% had early severe AKI. In the adjusted model, gestational diabetes (adjusted HR (aHR) 5.4, 95% CI 1.1-25.8), non-steroidal anti-inflammatory drugs (NSAIDs) (aHR 3.2, 95% CI 1.0-9.8), and vancomycin (aHR 13.9, 95% CI 2.3-45.1) were associated with early severe AKI. Late severe AKI occurred in 22% of participants. Early severe AKI (aHR 2.5, 95% CI 1.1-5.4), sepsis (aHR 2.5, 95% CI 1.4-4.4), vasopressors (aHR 2.9, 95% CI 1.8-4.6), and diuretics (aHR 2.6, 95% CI 1.9-3.6) were associated with late severe AKI. Participants who had necrotizing enterocolitis or received NSAIDs had longer severe AKI duration.

CONCLUSION

We identified major risk factors for severe AKI that can be the focus of future research.

IMPACT STATEMENT

Time-dependent risk factors for severe acute kidney injury (AKI) and its duration are not well defined among infants born <28 weeks' gestation. Over 1 in 5 infants born <28 weeks' gestation experienced severe AKI, and this study identified several major time-dependent perinatal risk factors occurring within 72 h prior to severe AKI. This study can support efforts to develop risk stratification and clinical decision support to help mitigate modifiable risk factors to reduce severe AKI occurrence and duration.

Acute Kidney Injury and Renal Replacement Therapy: A Review and Update for the Perioperative Physician

Post-operative acute kidney injury is a devastating complication with significant morbidity and mortality associated with it. The perioperative anesthesiologist is in a unique position to potentially mitigate the risk of postoperative AKI, however, understanding the pathophysiology, risk factors and preventative strategies is paramount. There are also certain clinical scenarios, where renal replacement therapy may be indicated intraoperatively including severe electrolyte abnormalities, metabolic acidosis and massive volume overload. A multidisciplinary approach including the nephrologist, critical care physician, surgeon and anesthesiologist is necessary to determine the optimal management of these critically ill patients.

Norepinephrine and Vasopressin in Hemorrhagic Shock: A Focus on Renal Hemodynamics

During hemorrhagic shock, blood loss causes a fall in blood pressure, decreases cardiac output, and, consequently, O₂ transport. The current guidelines recommend the administration of vasopressors in addition to fluids to maintain arterial pressure when life-threatening hypotension occurs in order to prevent the risk of organ failure, especially acute kidney injury. However, different vasopressors exert variable effects on the kidney, depending on the nature and dose of the substance chosen as follows: Norepinephrine increases mean arterial pressure both via its α-1-mediated vasoconstriction leading to increased systemic vascular resistance and its β1-related increase in cardiac output. Vasopressin, through activation of V1-a receptors, induces vasoconstriction, thus increasing mean arterial pressure. In addition, these vasopressors have the following different effects on renal hemodynamics: Norepinephrine constricts both the afferent and efferent arterioles, whereas vasopressin exerts its vasoconstrictor properties mainly on the efferent arteriole. Therefore, this narrative review discusses the current knowledge of the renal hemodynamic effects of norepinephrine and vasopressin during hemorrhagic shock.

Effect of liver resection-induced increases in hepatic venous pressure gradient on development of postoperative acute kidney injury

BACKGROUND

The impact of changes in portal pressure before and after liver resection (defined as ΔHVPG) on postoperative kidney function remains unknown. Therefore, we investigated the effect of ΔHVPG on (i) the incidence of postoperative AKI and (ii) the renin-angiotensin system (RAAS) and sympathetic nervous system (SNS) activity.

METHODS

We included 30 patients undergoing partial liver resection. Our primary outcome was postoperative AKI according to KDIGO criteria. For our secondary outcome we assessed the plasma renin, aldosterone, noradrenaline, adrenaline, dopamine and vasopressin concentrations prior and 2 h after induction of anaesthesia, on the first and fifth postoperative day. HVPG was measured prior and immediately after liver resection.

RESULTS

ΔHVPG could be measured in 21 patients with 12 patients HVPG showing increases in HVPG (∆HVPG≥1 mmHg) while 9 patients remained stable. AKI developed in 7/12 of patients with increasing HVPG, but only in 2/9 of patients with stable ΔHVPG (p = 0.302). Noradrenalin levels were significantly higher in patients with increasing ΔHVPG than in patients with stable ΔHVPG. (p = 0.009). Biomarkers reflecting RAAS and SNS activity remained similar in patients with increasing vs. stable ΔHVPG.

CONCLUSIONS

Patients with increased HVPG had higher postoperative creatinine concentrations, however, the incidence of AKI was similar between patients with increased versus stable HVPG.

Outcome of acute kidney injury: how to make a difference?

BACKGROUND

Acute kidney injury (AKI) is one of the most frequent organ failure encountered among intensive care unit patients. In addition to the well-known immediate complications (hydroelectrolytic disorders, hypervolemia, drug overdose), the occurrence of long-term complications and/or chronic comorbidities related to AKI has long been underestimated. The aim of this manuscript is to briefly review the short- and long-term consequences of AKI and discuss strategies likely to improve outcome of AKI.

MAIN BODY

We reviewed the literature, focusing on the consequences of AKI in all its aspects and the management of AKI. We addressed the importance of clinical management for improving outcomes AKI. Finally, we have also proposed candidate future strategies and management perspectives.

CONCLUSION

AKI must be considered as a systemic disease. Due to its short- and long-term impact, measures to prevent AKI and limit the consequences of AKI are expected to improve global outcomes of patients suffering from critical illnesses.

Association of intraoperative hypotension with acute kidney injury after liver resection surgery: an observational cohort study

Background

Acute kidney injury (AKI) is a major complication following liver resection. The aim of this study was to determine the risk factors for AKI after hepatic resection and whether intraoperative hypotension (IOH) was related to AKI.

Methods

Adult patients (≥ 18 years) undergoing liver resection between November 2017 and November 2019 at our hospital were retrospectively reviewed. AKI was defined as ≥50% increase in serum creatinine from baseline value within 48 h after surgery. IOH was defined as the lowest absolute mean arterial pressure (MAP) < 65 mmHg for more than 10 cumulative minutes during the surgery. Patients were divided into AKI group and non-AKI group, and were stratified by age ≥ 65 years.

Results

796 patients who met our inclusion and exclusion criteria were analyzed. After multivariable regression analysis, the IOH (OR, 2.565; P = 0.009) and age ≥ 65 years (OR, 2.463; P = 0.008) were risk factors for AKI. The IOH (OR, 3.547; P = 0.012) and received red blood cell (OR, 3.032; P = 0.036) were risk factors of AKI in age ≥ 65 years patients.

Conclusions

The IOH and age ≥ 65 years were risk factors for postoperative AKI, and IOH was associated with AKI in age ≥ 65 years patients following liver resection.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s12882-020-02109-9.

Renal effects of norepinephrine-induced variations in mean arterial pressure after liver transplantation: A randomized cross-over trial

BACKGROUND

Acute kidney injury is commonly seen after liver transplantation. The optimal perioperative target mean arterial pressure (MAP) for renal filtration, perfusion and oxygenation in liver recipients is not known. The effects of norepinephrine-induced changes in MAP on renal blood flow (RBF), oxygen delivery (RDO₂ ), glomerular filtration rate (GFR) and renal oxygenation (=renal oxygen extraction, RO₂ Ex) were therefore studied early after liver transplantation.

METHODS

Ten patients with an intra- and post-operative vasopressor-dependent systemic vasodilation were studied early after liver transplantation during sedation and mechanical ventilation. To achieve target MAP levels of 60, 75 and 90 mm Hg, the norepinephrine infusion rate was randomly and sequentially titrated. At each target MAP, data on cardiac index (CI), RBF and GFR were obtained by transpulmonary thermodilution (PiCCO), the renal vein thermodilution technique and renal extraction of chromium ethylenediaminetetraaceticacid (⁵¹ Cr-EDTA), respectively. Renal oxygen consumption (RVO₂ ) and extraction (RO₂ Ex) were calculated according to standard formulas.

RESULTS

At a target MAP of 75 mm Hg, CI (13%), RBF (18%), RDO₂ (24%), GFR (31%) and RVO₂ (20%) were higher while RO₂ Ex was unchanged compared to a target MAP of 60 mm Hg. Increasing MAP from 75 up to 90 mm Hg increased RVR by 38% but had no further effects on CI, RBF, RDO₂ or GFR.

CONCLUSIONS

In patients undergoing liver transplantation, RBF and GFR are pressure-dependent at MAP levels below 75 mm Hg. Our results suggest that MAP should probably be targeted to approximately 75 mm Hg for optimal perioperative renal filtration, perfusion and oxygenation in patients undergoing liver transplantation.

N-acetylcysteine versus Dopamine to Prevent Acute Kidney Injury after Cardiac Surgery in Patients with Preexisting Moderate Renal Insufficiency

Objective

Acute kidney injury after cardiac surgery is associated with mortality and morbidity. Therefore, strategies to prevent acute kidney injury are very important. The aim of this placebo-controlled randomized double-blind study was to compare the prophylactic efficacy of N-Acetylcysteine and dopamine administration in patients with pre-existing moderate renal insufficiency who were undergoing cardiopulmonary bypass.

Methods

This study included 135 patients with pre-existing moderate renal insufficiency who were scheduled for coronary artery bypass grafting surgery. Serum creatinine and GFR were recorded preoperatively and on the first and second postoperative days.

Results

On the first and second postoperative days, the drugs used showed statistically significant differences among the creatinine groups (P<0.001). According to Tukey's HSD, on the first and second PO, the creatinine of Group N, D and P were significantly different (P<0.001). On the first and second PO, the used drugs showed statistically significant differences among the effects of eGFR (P<0.001). According to Tukey's HSD on the first postoperative day, the average eGFR score of Group N compared to D and P were significantly difference (P<0.001). On the second postoperative day, the eGFR of Group N and D showed no difference (P=0.37), but P showed a difference (P<0.001).

Conclusion

We found that the prophylactic use of intravenous N-Acetylcysteine had a protective effect on renal function, whereas the application of renal dose dopamine did not have a protective effect in patients with pre-existing moderate renal failure.

Renal function and oxygenation are impaired early after liver transplantation despite hyperdynamic systemic circulation

Background

Acute kidney injury (AKI) occurs frequently after liver transplantation and is associated with the development of chronic kidney disease and increased mortality. There is a lack of data on renal blood flow (RBF), oxygen consumption, glomerular filtration rate (GFR) and renal oxygenation, i.e. the renal oxygen supply/demand relationship, early after liver transplantation. Increased insight into the renal pathophysiology after liver transplantation is needed to improve the prevention and treatment of postoperative AKI. We have therefore studied renal hemodynamics, function and oxygenation early after liver transplantation in humans.

Methods

Systemic hemodynamic and renal variables were measured during two 30-min periods in liver transplant recipients (n = 12) and post-cardiac surgery patients (controls, n = 73). RBF and GFR were measured by the renal vein retrograde thermodilution technique and by renal extraction of Cr-EDTA (= filtration fraction), respectively. Renal oxygenation was estimated from the renal oxygen extraction.

Results

In the liver transplant group, GFR decreased by 40% (p < 0.05), compared to the preoperative value. Cardiac index and systemic vascular resistance index were 65% higher (p < 0.001) and 36% lower (p < 0.001), respectively, in the liver transplant recipients compared to the control group. GFR was 27% (p < 0.05) and filtration fraction 40% (p < 0.01) lower in the liver transplant group. Renal vascular resistance was 15% lower (p < 0.05) and RBF was 18% higher (p < 0.05) in liver transplant recipients, but the ratio between RBF and cardiac index was 27% lower (p < 0.001) among the liver-transplanted patients compared to the control group. Renal oxygen consumption and extraction were both higher in the liver transplants, 44% (p < 0.01) and 24% (p < 0.05) respectively.

Conclusions

Despite the hyperdynamic systemic circulation and renal vasodilation, there is a severe decline in renal function directly after liver transplantation. This decline is accompanied by an impaired renal oxygenation, as the pronounced elevation of renal oxygen consumption is not met by a proportional increase in renal oxygen delivery. This information may provide new insights into renal pathophysiology as a basis for future strategies to prevent/treat AKI after liver transplantation.

Trial registration

ClinicalTrials.gov, NCT02455115. Registered on 23 April 2015.

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.

Hemodynamic variables and progression of acute kidney injury in critically ill patients with severe sepsis: data from the prospective observational FINNAKI study

Introduction

Knowledge of the association of hemodynamics with progression of septic acute kidney injury (AKI) is limited. However, some recent data suggest that mean arterial pressure (MAP) exceeding current guidelines (60–65 mmHg) may be needed to prevent AKI. We hypothesized that higher MAP during the first 24 hours in the intensive care unit (ICU), would be associated with a lower risk of progression of AKI in patients with severe sepsis.

Methods

We identified 423 patients with severe sepsis and electronically recorded continuous hemodynamic data in the prospective observational FINNAKI study. The primary endpoint was progression of AKI within the first 5 days of ICU admission defined as new onset or worsening of AKI by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. We evaluated the association of hemodynamic variables with this endpoint. We included 53724 10-minute medians of MAP in the analysis. We analysed the ability of time-adjusted MAP to predict progression of AKI by receiver operating characteristic (ROC) analysis.

Results

Of 423 patients, 153 (36.2%) had progression of AKI. Patients with progression of AKI had significantly lower time-adjusted MAP, 74.4 mmHg [68.3-80.8], than those without progression, 78.6 mmHg [72.9-85.4], P < 0.001. A cut-off value of 73 mmHg for time-adjusted MAP best predicted the progression of AKI. Chronic kidney disease, higher lactate, higher dose of furosemide, use of dobutamine and time-adjusted MAP below 73 mmHg were independent predictors of progression of AKI.

Conclusions

The findings of this large prospective multicenter observational study suggest that hypotensive episodes (MAP under 73 mmHg) are associated with progression of AKI in critically ill patients with severe sepsis.

An increase in renal dopamine does not stimulate natriuresis after fava bean ingestion

BACKGROUND

Fava beans (Vicia faba) contain dihydroxyphenylalanine (dopa), and their ingestion may increase dopamine stores. Renal dopamine regulates blood pressure and blood volume via a natriuretic effect.

OBJECTIVE

The objective was to determine the relation between dietary fava beans, plasma and urinary catechols, and urinary sodium excretion in 13 healthy volunteers.

DESIGN

Catechol and sodium data were compared by using a longitudinal design in which all participants consumed a fixed-sodium study diet on day 1 and the fixed-sodium diet plus fava beans on day 2. Blood was sampled at 1, 2, 4, and 6 h after a meal, and 3 consecutive 4-h urine samples were collected.

RESULTS

Mean (±SD) plasma dopa was significantly greater 1 h after fava bean consumption (11,670 ± 5440 compared with 1705 ± 530 pg/mL; P = 0.001) and remained elevated at 6 h. Plasma dopamine increased nearly 15-fold during this period. Fava bean consumption also increased urinary dopamine excretion to 306 ± 116, 360 ± 235, and 159 ± 111 μg/4-h urine sample compared with 45 ± 21, 54 ± 29, and 44 ± 17 μg in the 3 consecutive 4-h samples after the control diet (P ≤ 0.005). These substantial increases in plasma and urinary dopa and dopamine were unexpectedly associated with decreased urinary sodium.

CONCLUSION

The failure of fava bean consumption to provoke natriuresis may indicate that dopa concentrations in commercially available beans do not raise renal dopamine sufficiently to stimulate sodium excretion, at least when beans are added to a moderate-sodium diet in healthy volunteers. This trial was registered at clinicaltrials.gov as NCT01064739.

Impact of dopamine infusion on renal function in hospitalized heart failure patients: results of the Dopamine in Acute Decompensated Heart Failure (DAD-HF) Trial

BACKGROUND

Worsening renal function (WRF) and hypokalemia related to diuretic use for acute decompensated heart failure (ADHF) are common and associated with poor prognosis. Low-dose dopamine infusion improves renal perfusion; its effect on diuresis or renal function specifically in ADHF is not known.

METHODS AND RESULTS

Sixty consecutive ADHF patients (age 75.7 ± 11.2 years; 51.7% female; left ventricular ejection fraction 35.3 ± 12.1%) were randomized, after receiving a 40 mg intravenous furosemide bolus, to either high-dose furosemide (HDF, 20 mg/h continuous infusion for 8 hours) or low-dose furosemide combined with low-dose dopamine (LDFD, furosemide 5 mg/h plus dopamine 5 μg kg(-1) min(-1) continuous infusion for 8 hours). Both strategies were compared for total diuresis, WRF (defined as a rise in serum creatinine of >0.3 mg/dL from baseline to 24 hours), electrolyte balance, and 60-day postdischarge outcomes. Mean hourly excreted urine volume (272 ± 149 mL in HDF vs 278 ± 186 mL in LDFD group; P = .965) and changes in dyspnea score (Borg index: -4.4 ± 2.1 in HDF group vs -4.7 ± 2.0 in LDFD group; P = .575) during the 8 hours of protocol treatment were similar in the two groups. WRF was more frequent in the HDF (n = 9; 30%) than in the LDFD group (n = 2; 6.7%; P = .042). Serum potassium changed from 4.3 ± 0.5 to 3.9 ± 0.4 mEq/L at 24 hours (P = .003) in the HDF group and from 4.4 ± 0.5 to 4.2 ± 0.5 mEq/L at 24 hours (P = .07) in the LDFD group. Length of stay and 60-day mortality or rehospitalization rates (all-cause, cardiovascular, and worsening HF) were similar in the two groups.

CONCLUSIONS

In ADHF patients, the combination of low-dose furosemide and low-dose dopamine is equally effective as high-dose furosemide but associated with improved renal function profile and potassium homeostasis.

Inotrope and vasopressor therapy of septic shock

The ultimate goals of hemodynamic therapy in shock are to restore effective tissue perfusion and to normalize cellular metabolism. In sepsis, both global and regional perfusion must be considered. In addition, mediators of sepsis can perturb cellular metabolism, leading to inadequate use of oxygen and other nutrients despite adequate perfusion; one would not expect organ dysfunction mediated by such abnormalities to be corrected by hemodynamic therapy. Despite the complex pathophysiology of sepsis, an underlying approach to its hemodynamic support can be formulated that is particularly pertinent with respect to vasoactive agents. Both arterial pressure and tissue perfusion must be taken into account when choosing therapeutic interventions and the efficacy of hemodynamic therapy should be assessed by monitoring a combination of clinical and hemodynamic parameters. It is relatively easy to raise blood pressure, but somewhat harder to raise cardiac output in septic patients. How to optimize regional blood and microcirculatory blood flow remains uncertain. Specific end points for therapy are debatable and are likely to evolve. Nonetheless, the idea that clinicians should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis remains a fundamental principle. The practice parameters were intended to emphasize the importance of such an approach so as to provide a foundation for the rational choice of vasoactive agents in the context of evolving monitoring techniques and therapeutic approaches.

Acute kidney injury: current perspectives

Acute kidney injury (AKI) increases morbidity and mortality, particularly for the critically ill. Recent definitions standardizing AKI to reflect graded changes in serum creatinine and urine output (per the Risk, Injury, Failure, Loss, and End-stage renal failure [RIFLE] and Acute Kidney Injury Network [AKIN] criteria) with severity of renal injury and developments in AKI pathobiology are being utilized to identify biomarkers of early kidney injury. These developments may be useful in the early intervention of preventing AKI. Although there has been progress in the management of AKI, therapeutic challenges include appropriate prophylaxis prior to contrast administration, use of diuretics, vasopressors, and the type and dose of renal replacement therapy. Future use of bioartificial dialyzers, plasma therapies, and the possibility of stem cell regeneration of injured kidney tissue are being actively investigated to provide alternative treatment options for AKI. This review aims to provide an overview of current practices, available therapies, and continued research in AKI therapy.

Inotrope and vasopressor therapy of septic shock

When fluid administration fails to restore an adequate arterial pressure and organ perfusion in patients with septic shock, therapy with vasoactive agents should be initiated. The ultimate goals of such therapy in shock are to restore effective tissue perfusion and to normalize cellular metabolism. The efficacy of hemodynamic therapy in sepsis should be assessed by monitoring a combination of clinical and hemodynamic parameters. Although specific end points for therapy are debatable, and therapies will inevitably evolve as new information becomes available, the idea that clinicians should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis remains a fundamental principle.

Norepinephrine increases tolerance to acute anemia

OBJECTIVE

Extreme anemia threatens myocardial oxygen supply by 1) a decline of arterial oxygen content and 2) by a decline of mean aortic pressure (MAP) and thus coronary perfusion pressure. Standard treatment of low arterial oxygen content includes ventilation with pure oxygen and the transfusion of red blood cells. However, it is unknown whether the stabilization of MAP and coronary perfusion pressure with norepinephrine as the sole therapeutic modality may also increase tolerance to extreme anemia and thus improve outcome.

DESIGN

Prospective, randomized, controlled study.

SETTING

Experimental animal laboratory of a university hospital.

SUBJECTS

A total of 28 anesthetized, mechanically ventilated pigs.

INTERVENTIONS AND MEASUREMENTS

In the first protocol, 14 anesthetized pigs were hemodiluted by exchange of whole blood for 6% hydroxyethyl starch (200,000:0.5) until the individual critical hemoglobin concentration was reached. For the next 6 hrs, animals were either observed without any further intervention (control group) or their MAP was maintained by adapted infusion of norepinephrine (norepinephrine group). The main outcome variable of this protocol was the 6-hr mortality in both groups. In the second protocol, 14 anesthetized pigs received hemodilution until death. In seven animals, no intervention was performed during the hemodilution procedure, whereas in the other seven animals, MAP was maintained at >60 mm Hg by adapted infusion of norepinephrine. The main outcome variable of this protocol was the maximum exchangeable blood volume until death.

MAIN RESULTS

MAP stabilization with norepinephrine reduced the 6-hr mortality at the critical hemoglobin concentration from 100% to 14%. Maintaining MAP by adapted norepinephrine infusion during the hemodilution procedure allowed for the exchange of 125 (110/126) (median [quartile 1/quartile 3]) mL/kg blood (163% of blood volume) in the norepinephrine group, whereas only 76 (73/91) mL/kg blood (104% of blood volume) could be exchanged in the control group.

CONCLUSIONS

Application of norepinephrine can be judged a first-line intervention to bridge acute anemia via a stabilization of MAP and coronary perfusion pressure. However, due to the relevant side effects of norepinephrine, its sole long-term use during extreme anemia without concomitant transfusion of erythrocytes is not advised.

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.

Catecholamines and vasopressin during critical illness

This article summarizes the effects of catecholamines and vasopressin on the cardiovascular system, focusing on their metabolic and immunologic properties. Particular attention is dedicated to the septic shock condition.

'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.

Angiotensin II decreases the renal MRI blood oxygenation level-dependent signal

Acute experimental reduction of renal blood flow decreases the renal blood oxygenation level-dependent (BOLD) MRI signal in animals. Angiotensin II also reduces renal blood flow, but the ability of BOLD MRI to dynamically detect this response has not yet been investigated in humans. Six healthy male volunteers underwent an individual dose-finding study to identify the intravenous doses of angiotensin II, norepinephrine, and sodium nitroprusside necessary to induce a 15-mm Hg peak mean arterial blood pressure change. MRI studies followed within 3 weeks, when angiotensin II (8.8+/-1.4 ng/kg), norepinephrine (52+/-12 ng/kg), and sodium nitroprusside (2.0+/-0.3 microg/kg) were given twice in an unblocked, randomized sequence while imaging experiments were performed on a 1.5-T Siemens Sonata. A multiecho echo-planar imaging sequence was used to acquire T2* maps with a temporal resolution of 1 respiratory cycle. Averaged over a renal cortex dominated region of interest, angiotensin II caused a shortening of T2* between 6% and 10%. Sodium nitroprusside and norepinephrine, although of equal potency concerning blood pressure responses, did not alter the renal BOLD signal. The renal BOLD response to angiotensin II appeared with short onset latency (as early as 10 seconds after peripheral intravenous angiotensin II bolus administration) suggesting that this response is a consequence of altered perfusion rather than increased renal oxygen consumption. The methods described here are suitable to assess renal responsiveness to angiotensin II and may, thus, be of great value in human hypertension research.

The effects of increasing doses of noradrenaline on systemic and renal circulations in acute bacteraemic dogs

OBJECTIVE

To determine the dose-response effects of noradrenaline on the systemic and renal circulations during septic shock.

DESIGN AND SETTING

Prospective controlled experiment in a university animal laboratory.

SUBJECTS

Eight anaesthetized dogs.

INTERVENTIONS

Transonic flow probes were surgically placed on the aorta via a left lateral thoracotomy and on the left renal artery. Blood pressure was measured from the femoral artery. Acute bacteraemia shock was induced by injecting Escherichia coli bacteria intravenously. Increasing doses of noradrenaline (0.1, 0.2, 0.3, 0.4, 0.5 microg kg(-1) min(-1)) were infused intravenously for 30 min at 30-min intervals. The model was first validated in four dogs.

MEASUREMENTS AND RESULTS

Mean arterial pressure, central venous pressure, cardiac output, and renal blood flow were measured. Systemic vascular resistance was derived. Induction of bacteraemia decreased mean arterial pressure, central venous pressure and systemic vascular resistance. Cardiac output slightly increased. Noradrenaline produced linear dose-dependent increases in both mean arterial pressure and systemic vascular resistance. The response was attenuated during bacteraemia. Under non-bacteraemic conditions the maximum dose of noradrenaline reduced the renal blood flow from 12+/-1 to 10+/-1 ml kg(-1) min(-1). Bacteraemia further reduced renal blood flow to 7+/-1 ml kg(-1) min(-1), which was partly restored by the maximum dose of noradrenaline to 11+/-3 ml kg(-1) min(-1).

CONCLUSIONS

Noradrenaline can restore mean arterial pressure in bacteraemic shock and increases in mean arterial pressure are dose-dependent. The noradrenaline response is attenuated by bacteraemic shock. In bacteraemic shock noradrenaline also improves renal perfusion, as perfusion pressure increases. However, renal blood flow is not fully restored, suggesting that an element of impairment of renal blood flow exists due to the bacteraemia or noradrenaline.

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

OBJECTIVE

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

DATA SOURCE

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

STUDY SELECTION

Both human studies and relevant animal studies were considered.

DATA SYNTHESIS

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

CONCLUSIONS

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

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.

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.

The effects of anisodamine and dobutamine on gut mucosal blood flow during gut ischemia/reperfusion

AIM: To determine if anisodamine is able to augment mucosal perfusion during gut I/R ischemia-reperfusion.

METHODS: A jejunal sac was formed in Sprague Dawley rat. A Laser Doppler probe and a tonometer were inserted into the sac which was filled with saline. The superior mesenteric artery was occluded (SMAO) for 60 minutes followed by 90 minutes of reperfusion. At the end of 60 minutes of SMAO, either 0.2 mg/kg of anisodmine or dobutamine was injected into the jejunal sac. Laser Doppler mucosal blood flow and regional PCO₂ (PrCO₂) measurements were made.

RESULTS: Mucosal blood flow was significantly increased at 30, 60 and 90 minutes of reperfusion (R₃₀, R₆₀, R₉₀) when intraluminal anisodamine or dobutamine was present compared to intraluminal saline only (44 ± 3.3% or 48 ± 4.1% vs 37 ± 2.6% at R₃₀, 57 ± 5.0% or 56 ± 4.7% vs 45 ± 2.7% at R₆₀, 64 ± 3.3% or 56 ± 4.2% vs 48 ± 3.4% at R₉₀, respectively P < 0.05). Blood flow changes were also reflected by lowering of jejunal PrCO₂ measurements after intraluminal anisodamine or dobutamine compared with that of the saline controls (41 ± 3.1 mmHg or 44 ± 3.0 mmHg vs 49 ± 3.7 mmHg at R₃₀, 38 ± 3.7 mmHg or 40 ± 2.1 mmHg vs 47 ± 3.8 mmHg at R₆₀, 34 ± 2.1 mmHg or 39 ± 3.0 mmHg vs 46 ± 3.4 mmHg at R₉₀, respectively, P < 0.05). Most interesting finding was that there were significantly higher mucosal blood flow and lower jejunal PrCO₂ in anisodamine group than those in dobutamine group at 90 minutes of reperfusion (64 ± 3.3% vs 56 ± 4.2% for blood flow or 34 ± 2.1 mmHg vs 39 ± 3.0 mmHg for PrCO₂, respectively, P < 0.05), suggesting that anisodamine had a more lasting effect on mucosal perfusion than dobutamine.

CONCLUSION: Intraluminal anisodamine and dobutamine can augment mucosal blood flow during gut I/R and alleviate mucosal acidosis. The results provided benificial effects on the treatment of splanchnic hypoperfusion following traumatic or burn shock.

Use of vasopressor agents in critically ill patients

Distributive shock is a common problem in intensive care. Systemic hypotension is a medical emergency and will cause end-organ injury if not reversed. There are relatively few medications available to treat distributive shock. Catecholamines are most widely used for this indication and work by stimulating alpha- and/or beta-adrenergic receptors. Vasopressin and corticosteroids may have a role in reversing refractory shock and work primary through nonadrenergic mechanisms. Shock is difficult to define using hemodynamic criteria, because the same hemodynamic values can be normal in one patient, yet represent shock in another. Thus, the appropriate therapeutic endpoints for vasopressor therapy are not uniform for all patients. Similarly, the available evidence comparing vasopressor agents in terms of safety and efficacy is limited. When used at doses necessary to reverse distributive shock, less potent vasoconstrictors (eg, dopamine) do not appear to be safer than more potent ones (eg, norepinephrine) and do not appear to be as effective.

Current controversies in shock and resuscitation

Many controversies and uncertainties surround resuscitation of hemorrhagic shock caused by vascular trauma. Whereas the basic pathophysiology is better understood, much remains to be learned about the many immunologic cascades that lead to problems beyond those of initial fluid resuscitation or operative hemostasis. Fluid therapy is on the verge of significant advances with substitute oxygen carriers, yet surgeons are still beset with questions of how much and what type of initial fluid to provide. Finally, the parameters chosen to guide therapy and the methods used to monitor patients present other interesting issues.

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.

Low-dose "renal" dopamine

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

Pathophysiology and management of renal insufficiency in the perioperative and critically ill patient

Acute renal failure remains a common, devastating complication of the postoperative period and in the critically ill patient. The most common cause is the progression of prerenal insufficiency to ATN. Despite improved understanding of the pathogenic mechanisms, including impaired hemodynamic autoregulation, medullary hypoxia, and proximal tubular obstruction and transtubular backleak, the treatment, to date, remains largely supportive. Avoidance by ensuring hemodynamic stability, with provision of adequate renal perfusion, provides the best means for minimizing the complications of this organ dysfunction.