Dopamine and renal salvage in the critically ill patient

Peripheral chemoreflex restrains skeletal muscle blood flow during exercise in participants with treated hypertension

We tested the hypothesis that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Fourteen patients with treated hypertension (age 69 ± 11 years, 136 ± 12/80 ± 11 mmHg; mean ± SD) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2 µg kg-1 min-1) to inhibit the peripheral chemoreflex, at baseline, during isocapnic hypoxic rebreathing and during rhythmic handgrip exercise (3 min, 50% maximum voluntary contraction). At baseline, dopamine did not change mean blood pressure (95 ± 10 vs. 98 ± 10 mmHg, P = 0.155) but increased brachial artery blood flow (59 ± 20 vs. 48 ± 16 ml min-1, P = 0.030) and vascular conductance (0.565 ± 0.246 vs. 0.483 ± 0.160 ml min-1 mmHg-1; P = 0.039). Dopamine attenuated the increase in mean blood pressure (∆3 ± 4 vs. ∆8 ± 6 mmHg, P = 0.007) to isocapnic hypoxic rebreathing and reduced peripheral chemoreflex sensitivity by 28 ± 37% (P = 0.044). Rhythmic handgrip exercise induced increases in brachial artery blood flow and vascular conductance (both P < 0.05 vs. rest after 45 s) that were greater with dopamine than saline (e.g. Δ76 ± 54 vs. Δ60 ± 43 ml min-1 and Δ0.730 ± 0.440 vs. Δ0.570 ± 0.424 ml min-1 mmHg-1, respectively, at 60 s; main effect of condition both P < 0.0001). Our results indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow and vascular conductance increases to exercise in treated human hypertension. KEY POINTS: It was hypothesised that in human hypertension, an increased tonicity/sensitivity of the peripheral chemoreflex causes a sympathetically mediated restraint of nutritive blood flow to the exercising muscles. Treated patients with hypertension (n = 14) were studied under conditions of intravenous 0.9% saline (control) and low-dose dopamine (2 µg kg-1 min-1) to inhibit the peripheral chemoreflex. Low-dose dopamine reduced resting ventilation and peripheral chemoreflex sensitivity, and while mean blood pressure was unchanged, brachial artery blood flow and vascular conductance were increased. Low-dose dopamine augmented the brachial artery blood flow and vascular conductance responses to rhythmic handgrip. These findings indicate that the peripheral chemoreflex is tonically active at rest and restrains the blood flow, and vascular conductance increases to exercise in treated human hypertension.

Running from a Bear: How We Teach Vasopressors, Adrenoreceptors, and Shock

Vasopressors are widely used in the management of shock among critically ill patients. The physiology of vasopressors and adrenoreceptors and their effects on end organs therefore represent important, high-yield topics for learners in the critical care environment. In this report, we describe our approach to teaching this core concept using the stereotypical human physiologic response when running from a bear, in the context of the relevant supporting literature. We use escaping from a threatening predator as a lens to describe the end-organ effects of activating adrenoreceptors together with the effects of endogenous and exogenous catecholamines and vasopressors. After reviewing this foundational physiology, we transition to the clinical environment, reviewing the pathophysiology of various shock states. We then consolidate our teaching by integrating the physiology of adrenoreceptors with the pathophysiology of shock to understand the appropriateness of each therapy to various shock phenotypes. We emphasize to learners the importance of generating a hypothesis about a patient's physiology, testing that hypothesis with an intervention, and then revising the hypothesis as needed, a critical component in the management of critically ill patients.

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.

N-acyl dopamine derivates as lead compound for implementation in transplantation medicine

Conjugates of fatty acids with ethanolamine, amino acids or monoamine neurotransmitters occur widely in nature giving rise to so-called endocannabinoids. Anandamide and 2-arachidonoyl glycerol are the best characterized endocannabinoids activating both cannabinoid receptors (CB1 and CB2) and transient receptor potential vanilloid type 1 (TRPV1) channels (anandamide) or activating cannabinoid receptors only (2-arachidonoyl glycerol). TRPV1 is also activated by vanilloids, such as capsaicin, and endogenous neurolipins, e.g. N-arachidonoyl dopamine (NADA) and N-oleoyl dopamine (OLDA). Because donor dopamine treatment has shown to improve transplantation outcome in renal and heart recipients, this review will mainly focus on the biological activities of N-acyl dopamine derivates (NADD) as potential non-hemodynamic alternative for implementation in transplantation medicine. Hence the influence of NADD on transplantation relevant entities, i.e. cold inflicted injury, cytoprotection, I/R-injury, immune-modulation and inflammation will be summarized. The cytoprotective properties of endogenous endocannabinoids in this context will be briefly touched upon.

N-octanoyl-dopamine is an agonist at the capsaicin receptor TRPV1 and mitigates ischemia-induced [corrected] acute kidney injury in rat

Since stimulation of transient receptor potential channels of the vanilloid receptor subtype 1 (TRPV1) mitigates acute kidney injury (AKI) and endogenous N-acyl dopamine derivatives are able to activate TRPV1, we tested if synthetic N-octanoyl-dopamine (NOD) activates TRPV1 and if it improves AKI. These properties of NOD and its intrinsic anti-inflammatory character were compared with those of dopamine (DA). TRPV1 activation and anti-inflammatory properties of NOD and DA were tested using primary cell cultures in vitro. The influence of NOD and DA on AKI was tested in a prospective, randomized, controlled animal study with 42 inbred male Lewis rats (LEW, RT1), treated intravenously with equimolar concentrations of DA or NOD one hour before the onset of warm ischemia and immediately before clamp release. NOD, but not DA, activates TRPV1 channels in isolated dorsal root ganglion neurons (DRG) that innervate several tissues including kidney. In TNFα stimulated proximal tubular epithelial cells, inhibition of NFκB and subsequent inhibition of VCAM1 expression by NOD was significantly stronger than by DA. NOD improved renal function compared to DA and saline controls. Histology revealed protective effects of NOD on tubular epithelium at day 5 and a reduced number of monocytes in renal tissue of DA and NOD treated rats. Our data demonstrate that NOD but not DA activates TRPV1 and that NOD has superior anti-inflammatory properties in vitro. Although NOD mitigates deterioration in renal function after AKI, further studies are required to assess to what extend this is causally related to TRPV1 activation and/or desensitization.

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.

Evidence-based renal protection in cardiac surgery

Acute renal dysfunction is a common serious complication of cardiac surgery. Although a diversity of mechanisms exist by which the kidney can be damaged during cardiac surgery, atheroembolism, ischemia-reperfusion, and inflammation are believed to be primary contributors to perioperative renal insult. In addition, the high metabolic demands of active tubular reabsorption and the oxygen diffusion shunt characteristic of renal circulation make the kidney particularly vulnerable to ischemic injury. Remote effects of acute renal injury likely contribute to the strong association of this condition with other major postoperative morbidities and mortality and justify the search for renoprotective agents, even when dialysis is never required. Nonpharmacologic preventive strategies include procedure planning that is based on risk stratification, avoidance of nephrotoxins, and meticulous perioperative clinical care, including optimizing intravascular volume and attention to modifiable risk factors such as minimizing hemodilution. Although numerous pharmacologic interventions to prevent or treat acute renal injury have shown promise in animal models, randomized placebo-controlled clinical trials that have looked at measures of significant adverse outcomes such as death and dialysis have not confirmed a benefit.

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.

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.

Acute lung injury: pathophysiology, assessment and current therapy

Acute respiratory distress syndrome (ARDS) is a clinically defined entity describing the severity of diffuse alveolar injury caused by direct or indirect injury to the lung. Pathophysiology, clinical course and outcome of ARDS depend on the underlying cause, the severity of the disease and co-morbidities. Pulmonary function tests show restrictive lung disease, which is characterised by a reduction in lung compliance and functional residual capacity, resulting in marked ventilation-perfusion inequality. Current ventilator strategies aim to minimise ventilator-induced lung injury by targeting mechanical ventilation between the lower and upper inflection point of the pressure volume curve. This includes recruitment manoeuvres and the use of high PEEP to open the atelectatic lung and the use of permissive hypercapnia and the limitation of peak inspiratory pressure below 35 cm H2O to avoid overinflation. The clinical benefit of newer modes of ventilatory support such as inverse ratio ventilation, high frequency oscillatory ventilation, surfactant replacement, prone positioning and inhaled nitric oxide has yet to be determined in children.

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.

Effects of dopamine and epinephrine infusions on renal hemodynamics in severe malaria and severe sepsis

OBJECTIVE

To describe and compare the effects of dopamine and epinephrine in various doses on renal hemodynamics and oxygen transport in patients with severe malaria and severe sepsis.

DESIGN

Prospective, controlled, crossover trial.

SETTING

The intensive care unit of an infectious diseases hospital in Viet Nam.

PATIENTS

Fourteen patients with severe falciparum malaria and five with severe sepsis.

INTERVENTIONS

In an open, crossover design, we observed the effects on renal and systemic hemodynamics and oxygen transport of separate stepped infusions of epinephrine and dopamine. We measured renal blood flow (RBF) and cardiac output by the thermodilution method using fluoroscopically guided catheters. Creatinine clearance at each time point was calculated from the renal plasma flow and the renal arteriovenous difference in plasma creatinine.

MEASUREMENTS AND MAIN RESULTS

Dopamine at a "renal" dose (2.5 microg/kg/min) was associated with a mean (95% confidence interval) fractional increase in the absolute renal blood flow index (RBFI) of 37% (13% to 61%) and in RBF as a fraction of cardiac output (RBF/CO) of 35% (10% to 59%; p = .007 and p = .014, respectively). The consequent 39% (14% to 64%) increase in renal oxygen supply (p = .002) was accompanied by a 32% (20% to 44%) decrease in the renal oxygen extraction ratio (p = .0003), leading to no net change in renal oxygen consumption. At higher doses (10 microg/kg/min), both RBF and RBF/CO were not significantly different from baseline values and decreased further as the dose was reduced again. There was no obvious explanation for this hysteresis. There was no change in renal oxygen consumption throughout the study. Because lactic acidosis developed, epinephrine was only given to eight of the 19 patients, and the full stepped epinephrine infusion was given to four patients. Epinephrine infusion was associated, both in absolute terms and when compared with dopamine, with a significant increase in renal vascular resistance (p = .0008 and .0005, respectively), a decrease in RBF/CO (p = .002 and .03), and a compensatory increase in the renal oxygen extraction ratio (p = .005 and .0001). RBFI and renal oxygen consumption remained constant throughout the epinephrine infusion profile. Neither epinephrine nor dopamine significantly affected creatinine clearance or urine output. Twelve patients (63%) were in established renal failure (plasma creatinine, >3 mg/dL) at the time of the study, although the presence or absence of renal failure did not significantly influence the effects of the study drugs. However, overall, the presence of renal failure was associated with a lower mean renal oxygen consumption, a lower mean renal oxygen consumption as a fraction of systemic oxygen consumption, and a higher mean renal vascular resistance.

CONCLUSION

Although dopamine increased and epinephrine decreased fractional renal blood flow, there was no evidence that either drug produced either a beneficial or a deleterious effect on renal oxygen metabolism or function at any of the doses investigated.

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

OBJECTIVE

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

DESIGN

Prospective, single-blind, randomized study.

SETTING

University hospital, 19-bed multidisciplinary intensive care unit.

PATIENTS

Twelve hemodynamically stable patients with mild nonoliguric renal impairment.

INTERVENTIONS

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

MEASUREMENTS AND MAIN RESULTS

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

CONCLUSIONS

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

Dopamine in heart failure and critical care

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

Lack of renoprotective effects of dopamine and furosemide during cardiac surgery

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

Oliguria during corrective spinal surgery for idiopathic scoliosis: the role of antidiuretic hormone

Patients undergoing surgery for idiopathic scoliosis were studied to determine the incidence and aetiology of oliguria during the perioperative period and to evaluate the efficacy of low dose dopamine in preventing its occurrence. Thirty patients, aged 6-18 years undergoing elective surgery were studied. Anaesthesia was standardized. Patients were randomized to receive either dopamine infusion (3 micrograms.kg-1.min-1) (Group A) (n = 15) or dextrose infusion (control) (Group B) (n = 15). Serum and urinary electrolytes and osmolalities and serum antidiuretic hormone (ADH) concentrations were measured. Urine output and haemodynamic parameters were recorded. Intraoperative oliguria occurred in 7% of patients in Group A and 47% in Group B (P < 0.05). Postoperative oliguria occurred in 20% of patients in Group A and 47% in Group B (P > 0.05). Urine and serum biochemical analysis revealed a statistically significant decrease in serum sodium and osmolality (P < 0.005) and an increase in urinary sodium and osmolality in both groups. Serum ADH concentrations were increased in both groups (P < 0.05), returning to baseline 18 h postoperatively. We conclude that oliguria during corrective spinal surgery occurs in association with excess ADH secretion as opposed to perioperative hypovolaemia. Dopamine increases urine output in the perioperative period but does not prevent the release of ADH and its subsequent biochemical effects.

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

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

IMPLICATIONS

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

Anesthesia for Renal Transplantation

Renal transplantation is the preferred mode of replace ment therapy for most patients with end-stage renal disease (ESRD) and accounts for nearly 60% of all organ transplants in the United States. While as many as 35,000 people remain on the list waiting to receive a cadaveric kidney, living-related renal transplantation offers a shorter waiting period and greater survival. Maximization of the health of the kidney recipient before transplantation can improve ultimate outcome. Proper anesthetic management is facilitated by under standing the physiology and pharmacology of ESRD. Maintaining intraoperative blood volume is a key to good graft function, especially the living-related pediat ric kidney recipient. Recent improvements in combined immnosuppression therapy have improved the overall outcome in transplant recipients. The average 3-year survival is nearly 75%.

The American-European Consensus Conference on ARDS, part 2: Ventilatory, pharmacologic, supportive therapy, study design strategies, and issues related to recovery and remodeling. Acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) continues as a contributor to the morbidity and mortality of patients in intensive care units throughout the world, imparting tremendous human and financial costs. During the last 10 years there has been a decline in ARDS mortality without a clear explanation. The American-European Consensus Committee on ARDS was formed to re-evaluate the standards for the ICU care of patients with acute lung injury (ALI), with regard to ventilatory strategies, the more promising pharmacologic agents, and the definition and quantification of pathologic features of ALI that require resolution. It was felt that the definition of strategies for the clinical design and coordination of studies between centers and continents was becoming increasingly important to facilitate the study of various new therapies for ARDS.

The American-European Consensus Conference on ARDS, part 2. Ventilatory, pharmacologic, supportive therapy, study design strategies and issues related to recovery and remodeling

The acute respiratory distress syndrome (ARDS) continues as a contributor to the morbidity and mortality of patients in intensive care units throughout the world, imparting tremendous human and financial costs. During the last ten years there has been a decline in ARDS mortality without a clear explanation. The American-European Consensus Committee on ARDS was formed to re-evaluate the standards for the ICU care of patients with acute lung injury (ALI), with regard to ventilatory strategies, the more promising pharmacologic agents, and the definition and quantification of pathological features of ALI that require resolution. It was felt that the definition of strategies for the clinical design and coordination of studies between centers and continents was becoming increasingly important to facilitate the study of various new therapies for ARDS.

Acute renal failure in infants, children and adults

Acute renal failure (ARF) occurs in many critically ill patients regardless of age. A combination of events often seen in critical care settings, including shock, sepsis, hypoxia, and the use of potentially nephrotoxic medications, combine to make ARF an ongoing and important management issue in critical care medicine. Since the events leading to the development of ARF differ in infants, children, adults, and the elderly, the pathophysiology, clinical features, and treatment modalities do indeed have remarkable similarities among the different age groups.

Management of acute renal failure: new perspectives

Despite major developments in medicine, surgery, and intensive care, acute renal failure (ARF) still remains a common problem affecting approximately 5% of all general hospital patients. Mortality of all forms of ARF continues to be greater than 50%, and this percentage has not decreased significantly over the last 30 years. There are multiple factors, which may explain the persistence of such high mortality; the most important of these is probably the evolution of the disease spectrum underlying the development of ARF. At present, ARF is more often observed in older or more complex patients frequently in association with multiorgan system failure. The annual cost of managing ARF is staggering. This article reviews several of the new strategies and approaches that have been developed to aid in the management and prevention of ARF. For example, the use of biocompatible membranes has been proven to positively influence the course of ARF, which necessitates renal replacement therapy. Although continuous renal replacement therapy has a theoretical advantage compared with intermittent hemodialysis in critically ill and hemodynamically unstable patients, there are no well-controlled clinical studies to support a beneficial effect on mortality. There is, however, good evidence that calcium channel blockers play a positive role in the management of ARF, especially that associated with cadaveric kidney transplantation. Vasoactive agents, such as dopamine, may have the advantage of increasing the urine output in patients with oliguric ARF; however, their efficacy in otherwise altering the course of ARF is not well substantiated. Finally, growth factors and atrial natriuretic peptide appear to have the potential for accelerating renal recovery and decreasing morbidity and mortality from this commonly encountered medical problem. Prospective randomized clinical studies are the key to many of the dilemmas encountered with ARF.

Renal hemodynamics during norepinephrine and low-dose dopamine infusions in man

OBJECTIVE

To characterize the effects of pressor doses of norepinephrine and low-dose dopamine (3 micrograms/kg/min) on renal hemodynamics in man, as well as to determine the clinical relevance of combining dopamine with norepinephrine.

DESIGN

Prospective, single-blind, randomized study.

SETTING

Clinical research unit of a tertiary care hospital. SUBJECTS. Six healthy male volunteers ranging in age between 20 and 28 yrs.

INTERVENTIONS

The subjects were assigned randomly to four treatments (1 wk apart) in which renal hemodynamics and electrolyte excretion were assessed. Treatments consisted of 180-min infusions of the following: a) 0.9% sodium chloride (control); b) pressor doses of norepinephrine; c) dopamine at 3 micrograms/kg/min; and d) pressor doses of norepinephrine and dopamine at 3 micrograms/kg/min. Pressor doses of norepinephrine was defined as doses required to increase mean arterial pressure (MAP) by 20 mm Hg.

MEASUREMENTS AND MAIN RESULTS

Glomerular filtration rate and renal blood flow were derived from inulin and para-aminohippurate clearances, respectively. Urine output and urine solute excretion were also determined. The mean norepinephrine dose required to increase MAP by 22 +/- 2 mm Hg was 118 +/- 30 ng/kg/min (range 76 to 164). After the addition of dopamine, similar doses of norepinephrine resulted in an MAP increase of 15 +/- 4 mm Hg. Glomerular filtration rate and urine output were comparable under all conditions. The infusion of norepinephrine decreased renal blood flow from 1241 +/- 208 to 922 +/- 143 mL/min/1.73 m2 (p = .03). The addition of dopamine returned renal blood flow to baseline values. The clearance of urine sodium increased significantly with the infusion of dopamine alone (p = .03). All subjects completed the four treatment periods. Adverse events, manifested mostly as palpitations and flushing, were rare and self-limiting.

CONCLUSIONS

The addition of dopamine (3 micrograms/kg/min) to pressor doses of norepinephrine normalized renal blood flow in healthy volunteers. These hemodynamic changes were not reflected in urine output and glomerular filtration rate; hence, these monitoring parameters may be unreliable indicators of renal function in the setting of vasopressor therapy. In addition, systemic effects were observed with dopamine (3 micrograms/kg/min), as indicated by a decrease in MAP.

Is renal dose dopamine protective or therapeutic? No

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

Refractory Heart Failure: A Therapeutic Approach

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

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

OBJECTIVE

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

DESIGN

Prospective, clinical study using sequential periods.

SETTING

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

PATIENTS

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

INTERVENTION

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

MEASUREMENTS AND RESULTS

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

CONCLUSION

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

Triage of critically ill patients: an overview of interventions

The recognition of tissue hypoxia or cumulative oxygen debt is of fundamental importance for triage and resuscitation of critically ill patients during the ¿golden hour¿ in the emergency department (ED). The measurement of central venous blood oxygen saturation, plasma lactate concentration, cardiac output, systemic oxygen transport and use, and non-vital organ oxygenation and function can enhance the detection of systemic and regional hypoperfusion and tissue hypoxia. Systemic and organ-specific oxygenation indices may guide the choice of therapy to optimize resuscitation of the macrocirculation and microcirculation in critically ill ED patients.

Increasing organ blood flow during cardiopulmonary bypass in pigs: comparison of dopamine and perfusion pressure

OBJECTIVE

To determine whether low-dose dopamine infusion (5 micrograms/kg/min) during cardiopulmonary bypass selectively increases perfusion to the kidney, splanchnic organs, and brain at low (45 mm Hg) as well as high (90 mm Hg) perfusion pressures.

DESIGN

Randomized crossover trial.

SETTING

Animal research laboratory in a university medical center.

SUBJECTS

Ten female Yorkshire pigs (weight 29.9 +/- 1.2 kg).

INTERVENTION

Anesthetized pigs were placed on normothermic cardiopulmonary bypass at a 100-mL/kg/min flow rate. After baseline measurements, the animal was subjected, in random sequence, to 15-min periods of low perfusion pressure (45 mm Hg), low perfusion pressure with dopamine (5 micrograms/kg/min), high perfusion pressure (90 mm Hg), and high perfusion pressure with dopamine. Regional perfusion (radioactive microspheres) was measured in tissue samples (2 to 10 g) from the renal cortex (outer two-third and inner one-third segments), stomach, duodenum, jejunum, ileum, colon, pancreas, and cerebral hemispheres.

MEASUREMENTS AND MAIN RESULTS

Systemic perfusion pressure was altered by adjusting pump flow rate (r2 = .61; p < .05). In the kidney, cortical perfusion pressure increased from 178 +/- 16 mL/min/100 g at the low perfusion pressure to 399 +/- 23 mL/min/100 g at the high perfusion pressure (p < .05). Perfusion pressure augmentation increased the ratio of outer/inner renal cortical blood flow from 0.9 +/- 0.1 to 1.2 +/- 0.1 (p < .05). At each perfusion pressure, low-dose dopamine had no beneficial effect on renal perfusion or flow distribution. Similar results were found in the splanchnic organs, where regional perfusion was altered by perfusion pressure but not by dopamine. In contrast, neither changing perfusion pressure nor adding low-dose dopamine altered blood flow to the cerebral cortex.

CONCLUSIONS

These data indicate that the lower autoregulatory limits of perfusion to the kidneys and splanchnic organs differ from those limits to the brain during normothermic bypass. Selective vasodilation from low-dose dopamine was not found in renal, splanchnic, or cerebral vascular beds. Increasing the perfusion pressure by pump flow, rather than by the addition of low-dose dopamine, enhanced renal and splanchnic but not cerebral blood flows during cardiopulmonary bypass.

Modification of the diuretic and natriuretic effects of a dopamine infusion by fluid loading in preoperative cardiac surgical patients

An intravenous infusion of dopamine at 2.5 microgram/kg/min was administered for 40 minutes to anesthetized cardiac surgical patients, and their renal function was measured. Five patients had the usual preoperative regimen of reduced fluid intake for the night and morning before surgery (nonhydrated), and five patients received normal saline, 2 mL/kg/hr intravenously, for 6 hours before anesthesia (hydrated). Renal function (measured by urine output, sodium excretion, free water clearance, and fractional excretion of sodium) was similar immediately before starting the dopamine infusion. All four variables were significantly higher in the hydrated group after 10 minutes; this difference becoming maximal after 40 minutes. Twenty minutes after stopping the dopamine infusion, renal function was similar in the two groups. This study indicates that preoperatively fluid-restricted patients demonstrate powerful salt and water conservation with reduced natriuretic and diuretic responses to a low-dose dopamine infusion when compared with hydrated patients. Patients with adequate fluid loading and intravascular volume will demonstrate a marked natriuresis and diuresis in response to low-dose dopamine infusion.

Renovascular interaction of epinephrine, dopamine, and intraperitoneal sepsis

OBJECTIVE

To determine the effect of intraperitoneal sepsis on the systemic and renal actions of the continous infusion of epinephrine or dopamine, and during the concurrent administration of both drugs.

DESIGN

Prospective, randomized study.

SETTING

Laboratory at a university hospital.

SUBJECTS

Seven conscious, chronically catheterized, adult merino sheep.

INTERVENTIONS

Epinephrine at 40 micrograms/min or dopamine at 2 micrograms/kg/min, or both drugs concurrently were infused for 4 hrs on separate study days in healthy sheep. This protocol was then repeated following the induction of sepsis after the intraperitoneal injection of 10(11) Escherichia coli, 10(12) Bacteroides fragilis, and bran.

MEASUREMENTS AND MAIN RESULTS

Systemic oxygen delivery (DO2) and consumption were measured using thermodilution cardiac output and measured oxygen content. Renal blood flow was measured using an electromagnetic flow transducer, and creatinine clearance was calculated as the quotient of renal blood flow and the renal extraction ratio of creatinine. Infusion of epinephrine augmented systemic DO2 and mean arterial pressure (MAP) during both healthy and septic studies. Systemic oxygen consumption was only increased during epinephrine infusion in the septic study. During the healthy animal study, renal blood flow was initially decreased during epinephrine infusion, but increased to 36% above baseline (p = .003). However, creatinine clearance remained unchanged. During the experimental sepsis study, the infusion of epinephrine had less marked effects on renal blood flow (unchanged from baseline), while an initial reduction (15 mins) in creatinine clearance (p = .04) was not sustained and had returned to baseline by 3 hrs. Dopamine alone produced no change in systemic oxygen variables or MAP during the studies on healthy or septic animals. Although dopamine produced renal vasodilation and an increase in renal blood flow in the healthy state, these results were not found during the septic state. In addition, concurrent infusion of dopamine with epinephrine did not alter the systemic or renal effects of epinephrine during the healthy or septic states.

CONCLUSIONS

These results do not support the routine use of low-dose dopamine, and demonstrate a change in renovascular responses to catecholamines during intraperitoneal sepsis. The infusion of epinephrine at 40 micrograms/min had few deleterious effects on the kidney, and augmented both MAP and systemic DO2. Its role as a catecholamine in the management of sepsis may need to be reconsidered.

Some Recent Controversies in Intensive Care

The ability of dopamine to reverse oliguria has led to its ubiquitous renal protective use in patients at risk of acute renal failure. However, this diuresis is due primarily to inhibition of distal tubular sodium reabsorption and not renal vasodilation. Recent controlled clinical studies have been unable to demonstrate a renal protective effect independent of changes in cardiac output.

Selective decontamination of the digestive tract (SDD) has the appealing theoretical ability to minimize upper gastrointestinal colonization with gram-negative bacteria and fungi, and subsequently reduce nosocomial infection and mortality. Such modification of flora does occur, but the initial studies showing a reduction in lower respiratory tract infections have not been supported by recent large double-blind randomized controlled trials. A reduction in mortality or length of stay of general intensive care patients given SDD has never been demonstrated, and it remains an experimental therapy with possible application for some patient subgroups.

Upper gastrointestinal hemorrhage (UGH) in the critically ill is associated with prolonged ventilatory support and coagulopathy, but clinically important bleeding is now uncommon. Prophylaxis with agents that increase gastric pH is effective in reducing UGH, but may be associated with a higher incidence of nosocomial pneumonia than occurs with alternatives such as sucralfate. Prophylaxis does not alter mortality, and it is now controversial which patients, if any, should routinely receive such treatment.

Sepsis and septic shock. II. Treatment

Mortality from septic shock is considerable despite the advantages of cardiovascular support and antibiotic therapy. This article reviews current therapy of septic shock including immunotherapy and further possibilities of septic shock treatment. The role of cytokines, their inhibitors and antibodies to endotoxin is mentioned. Although these treatments hold much promise for the future, careful evaluation of both the benefits and complications of therapy is needed before widespread clinical use can be recommended.

Serum aldosterone concentrations and urine output in oliguric intensive care unit patients receiving low-dose dopamine

OBJECTIVE

To determine whether the diuretic and natriuretic effects of low-dose dopamine (2.5 micrograms/kg/min) are associated with changes in serum aldosterone concentration.

DESIGN

Prospective clinical study.

SETTING

Surgical intensive care unit (SICU) of a university hospital.

PARTICIPANTS

Oliguric (urine output < 0.5 mL/kg/h) SICU patients. All patients were resuscitated to pulmonary artery occlusion pressure > 10 mm Hg, mean arterial pressure > 65 mm Hg, and cardiac index > 2.5 L/min/m2. Patients with a serum creatinine concentration > 176.8 mumol/L (2.0 mg/dL), those who received diuretics within 12 hours prior to entry into the study, and renal transplant recipients were excluded.

MAIN OUTCOME MEASURES

Hourly urine output (mean +/- SD) was recorded 2 hours before and for 6 hours after the initiation of low-dose dopamine. Urine sodium and serum aldosterone concentrations were obtained prior to and 6 hours after the start of low-dose dopamine.

RESULTS

Fifteen patients were enrolled in the study. Urine output (mean +/- SD) increased from 0.31 +/- 0.11 mL/kg/h before to 0.80 +/- 0.34 mL/kg/h following low-dose dopamine (p < 0.01). Urine sodium concentrations increased from 46 +/- 32 mmol/L baseline to 72 +/- 53 mmol/L following low-dose dopamine (p < 0.05), and serum aldosterone concentrations decreased from 415.82 +/- 341.48 pmol/L prior to low-dose dopamine infusion to 256.04 +/- 204.17 pmol/L (p < 0.05). Cardiac output, pulmonary artery occlusion pressure, mean arterial pressure, and heart rate did not change.

CONCLUSIONS

Low-dose dopamine significantly increases urine output and urine sodium excretion in oliguric, critically ill, surgical patients, and is associated with a decrease in serum aldosterone concentration. The diuretic and natriuretic effects of low-dose dopamine may be, in part, related to a dopamine-mediated inhibition of aldosterone secretion.

A review of anaesthesia for ruptured abdominal aortic aneurysm with special emphasis on preclamping fluid resuscitation

Ruptured abdominal aortic aneurysm (RAAA) remains a critical emergency with an average hospital mortality of 50%. There has been no significant improvement in survival despite advances in anaesthesia, surgery and intensive care over the last 30 years. It is believed that early diagnosis, aggressive surgical management and meticulous attention to haemodynamic status and coagulation may improve survival, but this is unsubstantiated. Mortality is closely linked to the degree of preoperative hypotension and other related factors such as massive blood transfusion and cardiac arrest. Survival depends not only on the severity of rupture, but also the ability to compensate physiologically, and is linked to the premorbid state of the patient. Management priorities are dictated chiefly by the clinical signs and symptoms at presentation. There is controversy regarding the appropriate preoperative fluid regimen for RAAA.