Effects of norepinephrine on regional blood flow and oxygen extraction capabilities during endotoxic shock

Endothelial Activation and Microcirculatory Disorders in Sepsis

The vascular endothelium is crucial for the maintenance of vascular homeostasis. Moreover, in sepsis, endothelial cells can acquire new properties and actively participate in the host's response. If endothelial activation is mostly necessary and efficient in eliminating a pathogen, an exaggerated and maladaptive reaction leads to severe microcirculatory damage. The microcirculatory disorders in sepsis are well known to be associated with poor outcome. Better recognition of microcirculatory alteration is therefore essential to identify patients with the worse outcomes and to guide therapeutic interventions. In this review, we will discuss the main features of endothelial activation and dysfunction in sepsis, its assessment at the bedside, and the main advances in microcirculatory resuscitation.

Evaluation and Management of Abdominal Compartment Syndrome in the Emergency Department

BACKGROUND

Abdominal compartment syndrome is a potentially deadly condition that can be missed in the emergency department setting.

OBJECTIVE

The purpose of this narrative review article is to provide a summary of the background, pathophysiology, diagnosis, and management of abdominal compartment syndrome with a focus on emergency clinicians.

DISCUSSION

Abdominal compartment syndrome is caused by excessive pressure within the abdominal compartment due to diminished abdominal wall compliance, increased intraluminal contents, increased abdominal contents, or capillary leak/fluid resuscitation. History and physical examination are insufficient in isolation, and the gold standard is intra-abdominal pressure measurement. Abdominal compartment syndrome is defined as an intra-abdominal pressure >20 mm Hg with evidence of end-organ injury. Management involves increasing abdominal wall compliance (e.g., analgesia, sedation, and neuromuscular blocking agents), evacuating gastrointestinal contents (e.g., nasogastric tubes, rectal tubes, and prokinetic agents), avoiding excessive fluid resuscitation, draining intraperitoneal contents (e.g., percutaneous drain), and decompressive laparotomy in select cases. Patients are critically ill and often require admission to a critical care unit.

CONCLUSIONS

Abdominal compartment syndrome is an increasingly recognized condition with the potential for significant morbidity and mortality. It is important for clinicians to be aware of the current evidence regarding the diagnosis, management, and disposition of these patients.

Coupled plasma haemofiltration filtration in severe sepsis: systematic review and meta-analysis

INTRODUCTION

Coupled plasma filtration and adsorption (CPFA) has been used in the treatment of severe sepsis with the intention of removing the proinflammatory and anti-inflammatory mediators from the systemic circulation. It is believed that this interrupts and moderates the septic cascade, but there is uncertainty about the benefits of this therapy.

METHODS

A systematic review and meta-analysis were performed to estimate the effects of CPFA on mortality in severe sepsis. The Cochrane CENTRAL Register of Controlled Trials, CINAHL, EMBASE, MEDLINE-EBSCO-Host, MEDLINE and ProQuest, were searched from 1997 to 2013. Randomised controlled trials, prospective cohort studies and retrospective cohort studies were included using the Centre for Reviews and Dissemination (CRD) framework. Data were abstracted using standard pro forma, and studies independently reviewed by two authors to confirm inclusion criteria. Quality of studies and risk of bias were assessed using the Grading of Recommendations, Assessment, Development and Evaluation Working Group (GRADE) and Critical Appraisal Skills (CASP) criteria, respectively. Meta-analysis was performed using Review Manager (RevMan V.5.1) software. The primary outcome was 28-day mortality. Secondary outcomes were mediator adsorption (picograms/mL), mean arterial BP (mm Hg) and oxygenation ratio.

RESULTS

17 studies met the inclusion criteria (n=441 patients, 242 CPFA). 14 studies reported the primary outcome of 28-day mortality. There were 88 deaths in CPFA patients versus 118 in those receiving haemofiltration: OR 0.34 (95% CI 0.24 to 0.13). Point estimates of effect on the secondary outcomes of mean arterial pressure and oxygen ratio favoured CPFA. Studies were small and heterogenous.

CONCLUSIONS

Evidence for CPFA in severe sepsis is sparse, of poor quality and further research is required, however, this meta-analysis noted improvements in survival rates of those patients treated with CPFA.

Contrast-enhanced ultrasonography to evaluate changes in renal cortical microcirculation induced by noradrenaline: a pilot study

Introduction

We used contrast-enhanced ultrasound (CEUS) to estimate the effect of an increase in mean arterial pressure (MAP) induced by noradrenaline infusion on renal microvascular cortical perfusion in critically ill patients.

Methods

Twelve patients requiring a noradrenaline infusion to maintain a MAP more than 60 mmHg within 48 hours of intensive care unit admission were included in the study. Renal CEUS scans with destruction-replenishment sequences and Sonovue® (Bracco, Milano Italy) as a contrast agent, were performed at baseline (MAP 60 to 65 mmHg) and after a noradrenaline-induced increase in MAP to 80 to 85 mmHg.

Results

There was no adverse effect associated with ultrasound contrast agent administration or increase in noradrenaline infusion rate. Adequate images were obtained in all patients at all study times. To reach the higher MAP target, median noradrenaline infusion rate was increased from 10 to 14 μg/min.

Noradrenaline-induced increases in MAP were not associated with a significant change in overall CEUS derived mean perfusion indices (median perfusion index 3056 (interquartile range: 2438 to 6771) arbitrary units (a.u.) at baseline versus 4101 (3067 to 5981) a.u. after MAP increase, P = 0.38). At individual level, however, we observed important heterogeneity in responses (range -51% to +97% changes from baseline).

Conclusions

A noradrenaline-induced increase in MAP was not associated with an overall increase in renal cortical perfusion as estimated by CEUS. However, at individual level, such response was heterogeneous and unpredictable suggesting great variability in pressure responsiveness within a cohort with a similar clinical phenotype.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0653-3) contains supplementary material, which is available to authorized users.

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.

Interpretation of blood pressure signal: physiological bases, clinical relevance, and objectives during shock states

Achievement of a mean blood pressure (MBP) target is one of the hemodynamic goals to ensure an adequate blood perfusion pressure in critically ill patients. Arterial catheter allows for a continuous and precise monitoring of arterial pressure signal. In addition to giving a precise MBP monitoring, analysis of the blood pressure wave provides information that may help the clinician to interpret hemodynamic status. The interpretation of BP wave requires the understanding of simple principles. In this review, we first discuss the physiological mechanism responsible for arterial pressure generation. We then emphasize the interpretation of the static indexes and the dynamic indexes generated by heart-lung interactions derived from arterial pressure wave. Finally, we focus on MBP value as a therapeutic target in critically ill patients. We discuss the recommended target MBP value by reviewing available data from experimental and clinical studies.

Noradrenaline: friend or foe?

Septic shock, systemic inflammation and pharmacological vasodilatation are often complicated by systemic hypotension despite aggressive fluid resuscitation and an increased cardiac output. If the physician wishes to restore arterial pressure to higher levels (> 80-85 mmHg), with the aim of sustaining cerebral and coronary perfusion pressure, the administration of systemic vasopressor agents, such as norepinephrine (noradrenaline), becomes necessary. However, because norepinephrine (NE) induces vasoconstriction in many vascular beds (visibly in the skin), it may decrease renal and visceral blood flow, impairing visceral organ function. This unproven fear deters clinicians from using NE more consistently. Vasodilated states, however, are often associated with impaired peripheral vascular responsiveness. In such states, unlike under normal circulatory conditions, NE may actually improve visceral organ blood flow by selectively increasing organ perfusion pressure. Data available from animal studies show that the increased organ perfusion pressures achieved with NE results in improved GFR and renal blood flow. In fact, recent sophisticated physiological analysis of its effects on the kidney shows that, even after controlling for the pressure effect, NE therapy is associated with an increase in renal blood flow after endotoxin administration. In particular, the renal Pzf (pressure at which there is no further blood flow) is decreased such that, at a constant pressure, renal blood flow increases after NE. There are no controlled human data to define the effects of NE on the kidney in the clinical context. However, many patient series have now been reported. They show a seemingly positive effect of NE administration on GFR and urine output. Our clinical experience in septic patients and cardiac patients with inflammatory or pharmacological vasodilatation is also positive. We have demonstrated a positive effect on coronary blood flow. There is no reason to fear the effect of NE. If it is used to support a vasodilated circulation after adequate intravascular filling has occurred and after a normal or increased cardiac output has been established, it is likely to be a friend not a foe.

Increasing arterial blood pressure with norepinephrine does not improve microcirculatory blood flow: a prospective study

Introduction

Our goal was to assess the effects of titration of a norepinephrine infusion to increasing levels of mean arterial pressure (MAP) on sublingual microcirculation.

Methods

Twenty septic shock patients were prospectively studied in two teaching intensive care units. The patients were mechanically ventilated and required norepinephrine to maintain a mean arterial pressure (MAP) of 65 mmHg. We measured systemic hemodynamics, oxygen transport and consumption (DO₂ and VO₂), lactate, albumin-corrected anion gap, and gastric intramucosal-arterial PCO₂ difference (ΔPCO₂). Sublingual microcirculation was evaluated by sidestream darkfield (SDF) imaging. After basal measurements at a MAP of 65 mmHg, norepinephrine was titrated to reach a MAP of 75 mmHg, and then to 85 mmHg. Data were analyzed using repeated measurements ANOVA and Dunnett test. Linear trends between the different variables and increasing levels of MAP were calculated.

Results

Increasing doses of norepinephrine reached the target values of MAP. The cardiac index, pulmonary pressures, systemic vascular resistance, and left and right ventricular stroke work indexes increased as norepinephrine infusion was augmented. Heart rate, DO₂ and VO₂, lactate, albumin-corrected anion gap, and ΔPCO₂ remained unchanged. There were no changes in sublingual capillary microvascular flow index (2.1 ± 0.7, 2.2 ± 0.7, 2.0 ± 0.8) and the percent of perfused capillaries (72 ± 26, 71 ± 27, 67 ± 32%) for MAP values of 65, 75, and 85 mmHg, respectively. There was, however, a trend to decreased capillary perfused density (18 ± 10,17 ± 10,14 ± 2 vessels/mm², respectively, ANOVA P = 0.09, linear trend P = 0.045). In addition, the changes of perfused capillary density at increasing MAP were inversely correlated with the basal perfused capillary density (R² = 0.95, P < 0.0001).

Conclusions

Patients with septic shock showed severe sublingual microcirculatory alterations that failed to improve with the increases in MAP with norepinephrine. Nevertheless, there was a considerable interindividual variation. Our results suggest that the increase in MAP above 65 mmHg is not an adequate approach to improve microcirculatory perfusion and might be harmful in some patients.

Phenylephrine versus norepinephrine for initial hemodynamic support of patients with septic shock: a randomized, controlled trial

Introduction

Previous findings suggest that a delayed administration of phenylephrine replacing norepinephrine in septic shock patients causes a more pronounced hepatosplanchnic vasoconstriction as compared with norepinephrine. Nevertheless, a direct comparison between the two study drugs has not yet been performed. The aim of the present study was, therefore, to investigate the effects of a first-line therapy with either phenylephrine or norepinephrine on systemic and regional hemodynamics in patients with septic shock.

Methods

We performed a prospective, randomized, controlled trial in a multidisciplinary intensive care unit in a university hospital. We enrolled septic shock patients (n = 32) with a mean arterial pressure below 65 mmHg despite adequate volume resuscitation. Patients were randomly allocated to treatment with either norepinephrine or phenylephrine infusion (n = 16 each) titrated to achieve a mean arterial pressure between 65 and 75 mmHg. Data from right heart catheterization, a thermodye dilution catheter, gastric tonometry, acid-base homeostasis, as well as creatinine clearance and cardiac troponin were obtained at baseline and after 12 hours. Differences within and between groups were analyzed using a two-way analysis of variance for repeated measurements with group and time as factors. Time-independent variables were compared with one-way analysis of variance.

Results

No differences were found in any of the investigated parameters.

Conclusions

The present study suggests there are no differences in terms of cardiopulmonary performance, global oxygen transport, and regional hemodynamics when phenylephrine was administered instead of norepinephrine in the initial hemodynamic support of septic shock.

Trial registration

ClinicalTrial.gov NCT00639015

Diastolic arterial blood pressure: a reliable early predictor of survival in human septic shock

BACKGROUND

Emphasis in therapy of human septic shock is shifting towards reliable end points and predictors of survival. Rationale is to study whether the evolution of cardiovascular reactivity in view of the administered doses of norepinephrine is an early predictor of in-hospital survival and to determine the optimal threshold of norepinephrine therapy and its consequences on renal function.

METHODS

Observational study of a prospective cohort of patients in septic shock, hospitalized in intensive care unit at least 24 hours before requiring norepinephrine. Excluded were patients requiring <72 hours of continuous norepinephrine (16 patients) or who received corticosteroids. Hemodynamic parameters (heart rate, blood pressure, urinary output, and temperature) were continuously monitored.

RESULTS

Of 68 patients, 45 survived [intensive care unit stay of 24 (12-36) days, hospital stay of 36 (27-66) days], and 23 died 5 (3-10) days after septic shock onset and norepinephrine treatment. Multivariate analysis revealed four independent positive predictive factors of short-term (10 days) outcome: Simplified Acute Physiology Score (SAPS) II <50 [odds ratio (OR) 6.4, 95% confidence interval (95% CI) 1.3-30.7, p < 0.011], and on day 3 Logistic Organ Dysfunction System (LODS) score <6 (OR 29.1, 95% CI 2.7-314.3, p = 0.0056), norepinephrine concentration <0.5 mug/kg/min (OR 17.6, 95% CI 2.2-142.0, p < 0.0007), diastolic arterial pressure >50 mm Hg (OR 24.8, 95% CI 2.9-215.9, p < 0.004), but not systolic arterial pressure.

CONCLUSIONS

Septic shock survival increases when dose of 0.5 mug/kg/min of norepinephrine continuously improves vascular tone within the first 48 hours, or when diastolic arterial pressure (>50 mm Hg) is restored. Norepinephrine has beneficial effects on renal function. Predictive value of LODS score on day 3 is demonstrated, while SAPS II is confirmed as the only reliable predictive factor in first 24 hours.

SHORT-TERM EFFECTS OF PHENYLEPHRINE ON SYSTEMIC AND REGIONAL HEMODYNAMICS IN PATIENTS WITH SEPTIC SHOCK

Clinical studies evaluating the use of phenylephrine in septic shock are lacking. The present study was designed as a prospective, crossover pilot study to compare the effects of norepinephrine (NE) and phenylephrine on systemic and regional hemodynamics in patients with catecholamine-dependent septic shock. In 15 septic shock patients, NE (0.82 +/- 0.689 microg x kg(-1) x min(-1)) was replaced with phenylephrine (4.39 +/- 5.23 microg x kg(-1) x min(-1)) titrated to maintain MAP between 65 and 75 mmHg. After 8 h of phenylephrine infusion treatment was switched back to NE. Data from right heart catheterization, acid-base balance, thermo-dye dilution catheter, gastric tonometry, and renal function were obtained before, during, and after replacing NE with phenylephrine. Variables of systemic hemodynamics, global oxygen transport, and acid-base balance remained unchanged after replacing NE with phenylephrine except for a significant decrease in heart rate (phenylephrine, 89 +/- 18 vs. NE, 93 +/- 18 bpm; P < 0.05). However, plasma disappearance rate (phenylephrine, 13.5 +/- 7.1 vs. NE, 16.4 +/- 8.7% x min(-1)) and clearance of indocyanine green (phenylephrine, 330 +/- 197 vs. NE, 380 +/- 227 mL x min(-1) x m(-2)), as well as creatinine clearance (phenylephrine, 81.3 +/- 78.4 vs. NE, 94.3 +/- 93.5 mL x min(-1)) were significantly decreased by phenylephrine infusion (each P < 0.05). In addition, phenylephrine increased arterial lactate concentrations as compared with NE infusion (1.7 +/- 1.0 vs. 1.4 +/- 1.1 mM; P < 0.05). After switching back to NE, all variables returned to values obtained before phenylephrine infusion except creatinine clearance and gastric tonometry values. Our results suggest that for the same MAP, phenylephrine causes a more pronounced hepatosplanchnic vasoconstriction as compared with NE.

Effects of vasopressin, norepinephrine, and l-arginine on intestinal microcirculation in endotoxemia*

OBJECTIVE

The effects of vasopressin, norepinephrine, and L-arginine alone or combined on intestinal microcirculation were evaluated in the septic mouse by intravital microscopy, with which we measured the erythrocyte flux and velocity in villus tip arterioles and the density of perfused villi.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Female BALB/c mice weighing between 18 and 21 g.

INTERVENTIONS

Anesthetized and ventilated mice received at t0 an intravenous injection of Escherichia coli endotoxin (2 mg/kg bolus intravenously), inducing after 1 hr (t60) a decrease in mean arterial blood pressure to 40-50 mm Hg associated with a significant decrease in erythrocyte flux and velocity in villus tip arterioles and in the density of perfused villi. The mice then received a randomly different treatment for endotoxin-induced shock. Treatments consisted in continuous intravenous infusion for 1 hr with either saline (control group), norepinephrine, vasopressin, L-arginine, vasopressin+L-arginine, or norepinephrine+L-arginine. The doses of vasopressors (used alone or combined with L-arginine) were titrated to restore mean arterial pressure to the baseline level.

MEASUREMENTS AND MAIN RESULTS

At the end of the treatment (t120), we observed in the control group further decreases in arteriolar flux and velocity and in the density of perfused villi. In the groups treated by a vasopressor alone, mean arterial pressure returned to baseline and there were no additional decreases in arteriolar flux and velocity or in the density of perfused villi. However, these latter three variables did not return to their preshock baseline values. Even though L-arginine did not restore mean arterial pressure, the infusion of L-arginine alone prevented the decrease in flux or erythrocyte velocity occurring between t60 and t120 and conserved to some extent the density of perfused villi compared with that in the control groups. In addition, we found that simultaneous administration of norepinephrine or vasopressin with L-arginine improved all microcirculation variables more efficiently than either vasopressor alone.

CONCLUSIONS

From these data, we conclude that a) restoring mean arterial pressure after 1 hr of endotoxemia was not sufficient to restore ad integrum intestinal mucosa microvascular perfusion; b) L-arginine could have a beneficial effect at the microcirculatory level, which was independent of mean arterial pressure; and c) administration of L-arginine combined with the maintenance of perfusion pressure by vasopressive drugs allowed a better preservation of intestinal microcirculation at an early stage of endotoxemia.

Critical oxygen delivery during cardiopulmonary bypass in dogs

BACKGROUND AND OBJECTIVE

To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37 degrees C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs.

METHODS

Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow.

RESULTS

At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 +/- 1.1 mL min(-1) kg(-1) in Group C and 6.8 +/- 1.8 mL min(-1) kg(-1) in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 +/- 1.6 mL min(-1) kg(-1); Group P: 7.6 +/- 2.0 mL min(-1) kg(-1)). Critical pump flows determined from lactate measurements were 55.6 +/- 13.8 mL min(-1) kg(-1) in Group C and 60.8 +/- 13.9 mL min(-1) kg(-1) in Group P (n.s.).

CONCLUSIONS

Oxygen delivery values greater than 7-8 mL min(-1) kg(-1) were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

Terlipressin or norepinephrine in hyperdynamic septic shock: a prospective, randomized study

OBJECTIVE

To compare, in patients with hyperdynamic septic shock, the effects of norepinephrine or terlipressin on hemodynamic variables and renal function.

DESIGN

Prospective, randomized, open-label study.

SETTING

Intensive care unit of a university, tertiary, and referral center.

PATIENTS

Twenty adult patients with hyperdynamic septic shock, after fluid resuscitation.

INTERVENTIONS

Patients were randomized to receive norepinephrine or terlipressin. Global hemodynamic variables, oxygen consumption, urine flow, creatinine clearance, and arterial blood lactate levels were measured.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, systemic vascular resistance, pulmonary vascular resistance, and left and right ventricular stroke work were significantly increased with both drugs. With terlipressin, but not with norepinephrine, a significant decrease in heart rate (from 113 +/- 17 to 104 +/- 11 beats.min(-1), p < .01) and cardiac index (from 5.1 +/- 1.7 to 4.2 +/- 1.6 L.min(-1).m(-2)) was observed, with no change in stroke volume. Oxygen delivery index (from 784 +/- 131 to 701 +/- 92 mL.min(-1).m(-2)) and consumption index (from 244 +/- 69 to 210 +/- 54 mL.min(-1).m(-2)) were significantly decreased with terlipressin, but not with norepinephrine. Blood lactate concentrations were significantly decreased with both drugs. Urine flow and creatinine clearance were increased with both drugs.

CONCLUSIONS

In patients with hyperdynamic septic shock, both norepinephrine and terlipressin were effective to raise mean arterial blood pressure. With terlipressin, but not norepinephrine, the improvement in blood pressure was achieved at the expense of cardiac index and oxygen consumption, which were significantly decreased. Renal function was improved with both drugs. In further studies, alternative strategies to maintain cardiac index should be explored, such as a synergy between low-dose terlipressin and dobutamine.

Terlipressin in catecholamine-resistant septic shock patients

To determine the effects on hemodynamics, laboratory parameters, and renal function of terlipressin used in septic-shock patients with hypotension not responsive to high-dose norepinephrine (>2.0 microg x kg(-1) x min(-1)) and dopamine (25 microg x kg(-1) x min(-1)), a prospective, open-label study was carried out in 17 patients. Patients received one or two boluses of 1 mg of terlipressin. In all patients terlipressin induced a significant increase in mean arterial pressure (MAP), systemic vascular resistance, pulmonary vascular resistance, and left and right ventricular stroke work. The increase in MAP was accompanied by a significant decrease in heart rate and cardiac index, but stroke volume remained unchanged. Oxygen delivery and consumption were significantly decreased. Blood lactate concentrations significantly decreased over the study period. Bilirubin, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were significantly increased. Thrombocytes were significantly decreased. No change in prothrombin time was observed. Renal function, assessed by urine flow and creatinine clearance, was significantly improved. Pulmonary function assessed by Pao2/Fio2 ratio was not affected. A significant reduction in norepinephrine and dopamine infusion rates was observed in all patients. Eight patients died during their ICU stay from late multiple organ failure. Within the limitations of the present study (open-label design, small group of patients), it can be concluded that in septic shock patients with hypotension nonresponsive to fluid resuscitation and high-dose vasopressors, terlipressin can be effective to restore MAP. Cardiac index should be closely monitored because it was significantly decreased by terlipressin. Renal function was significantly improved. Mesenteric circulation was not evaluated, but hepatic function was altered during the study period. Further studies are required to determine whether terlipressin is safe in terms of outcome in septic shock patients.

Increasing mean arterial pressure in patients with septic shock: effects on oxygen variables and renal function

OBJECTIVE

To measure the effects of increasing mean arterial pressure on oxygen variables and renal function in septic shock.

DESIGN

Prospective, open-label, randomized, controlled study.

SETTING

Medical-surgical intensive care unit of a tertiary care teaching hospital.

PATIENTS

Twenty-eight patients with a diagnosis of septic shock who required fluid resuscitation and pressor agents to increase and maintain mean arterial pressure > or =60 mm Hg.

INTERVENTIONS

Patients were treated with fluid and norepinephrine to achieve and maintain a mean arterial pressure of 65 mm Hg. Then they were randomized in two groups: In the first group (control group, n = 14), mean arterial pressure was maintained at 65 mm Hg, and in the second group (n = 14), mean arterial pressure was increased to 85 mm Hg by increasing the dose of norepinephrine.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic variables (mean arterial pressure, heart rate, mean pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, left and right ventricular stroke indexes), metabolic variables (oxygen delivery, oxygen consumption-calorimetric method, arterial lactate), and renal function variables (urine flow, serum creatinine, creatinine clearance) were measured. After introduction of norepinephrine, similar values of hemodynamic, metabolic, and renal function variables were obtained in both groups. No changes were observed in group 1 during the study period. Increasing mean arterial pressure from 65 to 85 mm Hg with norepinephrine in group 2 resulted in a significant increase in cardiac index from 4.8 (3.8-6.0) to 5.8 (4.3-6.9) L.min.m. Arterial lactate and oxygen consumption did not change. No changes were observed in renal function variables: urine flow, 63 (14-127) and 70 (15-121) mL; serum creatinine, 170 (117-333) and 153 (112-310) mumol.L; and creatinine clearance, 50 (12-77) and 67 (13-89) mL.min.1.73 m.

CONCLUSIONS

Increasing mean arterial pressure from 65 to 85 mm Hg with norepinephrine neither affects metabolic variables nor improves renal function.

Sepsis and the Kidney

Acute renal failure (ARF) secondary to sepsis is a highly prevalent diagnosis in the ICU setting and continues to be associated with a high rate of morbidity and mortality. The pathophysiology of sepsis-induced acute renal failure involves ischemic or toxic injury to the renal tubular epithelia, resulting in necrosis or apoptosis, and clinically is characterized as acute tubular necrosis. The management of sepsis-induced ARF includes both conventional intermittent hemodialysis and continuous renal replacement therapies. Experimental therapies to improve outcomes in sepsis-associated ARF include the provision of plasmapheresis and adsorption therapies, and the recent development and deployment of a renal tubule assist device.

Lingual, splanchnic, and systemic hemodynamic and carbon dioxide tension changes during endotoxic shock and resuscitation

Sublingual and intestinal mucosal blood flow and Pco2 were studied in a canine model of endotoxin-induced circulatory shock and resuscitation. Sublingual Pco2 (PsCO2) was measured by using a novel fluorescent optrode-based technique and compared with lingual measurements obtained by using a Stowe-Severinghaus electrode [lingual Pco2 (PlCO2)]. Endotoxin caused parallel changes in cardiac output, and in portal, intestinal mucosal, and sublingual blood flow (Q̇s). Different blood flow patterns were observed during resuscitation: intestinal mucosal blood flow returned to near baseline levels postfluid resuscitation and decreased by 21% after vasopressor resuscitation, whereas Q̇s rose to twice that of the preshock level and was maintained throughout the resuscitation period. Electrochemical and fluorescent Pco2 measurements showed similar changes throughout the experiments. The shock-induced increases in PsCO2 and PlCO2 were nearly reversed after fluid resuscitation, despite persistent systemic arterial hypotension. Vasopressor administration induced a rebound of PsCO2 and PlCO2 to shock levels, despite higher cardiac output and Q̇s, possibly due to blood flow redistribution and shunting. Changes in PlCO2 and PsCO2 paralleled gastric and intestinal Pco2 changes during shock but not during resuscitation. We found that the lingual, splanchnic, and systemic circulations follow a similar pattern of blood flow variations in response to endotoxin shock, although discrepancies were observed during resuscitation. Restoration of systemic, splanchnic, and lingual perfusion can be accompanied by persistent tissue hypercarbia, mainly lingual and intestinal, more so when a vasopressor agent is used to normalize systemic hemodynamic variables.

EFFECTS OF DOPAMINE AND NOREPINEPHRINE ON SYSTEMIC AND HEPATOSPLANCHNIC HEMODYNAMICS, OXYGEN EXCHANGE, AND ENERGY BALANCE IN VASOPLEGIC SEPTIC PATIENTS

Dopamine is widely used to improve systemic and hepatosplanchnic hemodynamics and oxygenation during sepsis. However, some studies have suggest that norepinephrine may have beneficial effects on regional blood flow and metabolism, whereas dopamine might have deleterious effects related to redistribution of blood flow away from the intestinal mucosa or by decreasing directly the cell redox state. In 12 vasoplegic septic patients, we compared the effects of norepinephrine and dopamine on systemic and hepatosplanchnic hemodynamics, oxygenation, and energy metabolism. Catecholamines were administered in a crossover randomized order to maintain mean arterial pressure (MAP) at 80 mmHg. Hepatosplanchnic blood flow (Qspl) was determined using a continuous infusion of indocyanine green dye. Despite a similar MAP, the cardiac index was higher with dopamine than with norepinephrine (6.3 [5.3-7.3] vs. 4.3 [3.8-4.9] L.min.m) (P <0.001). Qspl was similar with both catecholamines, but the ratio of Qspl to cardiac output was significantly lower with dopamine (23.9% [17.5-33.5]) than with norepinephrine (33.5% [25.8-37]) (P <0.05). Although global O2 delivery and O2 consumption were higher with dopamine (782 [707-859] vs. 553 [512-629] mL.min.m, P <0.001 and 164 [134-192] vs. 128 [111-149] mL.min.m, P <0.001, respectively), hepatosplanchnic O2 delivery and consumption were not different. Hepatic lactate uptake was lower (0.47 [0.3-0.89] vs. 1.01 [0.69-1.34] mmol.min) (P <0.01), and hepatic venous lactate-to-pyruvate ratio was higher (15.3 [7.6-21.1] vs. 11.2 [6.6-15.1], P <0.05) with dopamine than with norepinephrine. In vasoplegic septic patients, maintaining mean arterial pressure, hepatosplanchnic hemodynamics, and oxygen exchange with dopamine requires a consequent increased cardiac output, which is responsible for an increased global oxygen demand when compared with norepinephrine. In addition, dopamine impairs the hepatic energy balance. Its position as a preferential treatment compared with norepinephrine in this context may therefore be questionable.

Renal effects of norepinephrine in septic and nonseptic patients

OBJECTIVE

To assess the effects of a norepinephrine-induced vasoconstriction on renal function in septic and nonseptic patients.

DESIGN

Open-label prospective study.

SETTING

Medical-surgical ICU in an urban teaching hospital.

PATIENTS

Fourteen patients with septic shock and 12 uninfected patients with head trauma (Glasgow coma score, < 8).

INTERVENTIONS

Patients received norepinephrine infusion to increase systemic vascular resistance index (SVRI), and to raise mean arterial BP (MAP) to > 70 mm Hg in the septic group and cerebral perfusion pressure (CPP) to > 70 mm Hg in the head trauma group.

MEASUREMENTS AND MAIN RESULTS

MAP and SVRI increased in both groups (p < 0.001), and CPP significantly increased in the head trauma group (p < 0.001). The cardiac index was not modified in either group. Norepinephrine infusion reestablished urine flow in 12 of the 14 septic patients (p < 0.001), with a decrease in serum creatinine levels (p < 0.001) and an increase in creatinine clearance rate (p < 0.001) after 24 h. Urine parameters were not affected in the head trauma group.

CONCLUSION

Within the limitation of the present study, norepinephrine administration induces a marked vasoconstriction in septic and nonseptic patients. Norepinephrine has positive effects on renal function in septic patients but has no significant effect on the same urinary parameters when administered to uninfected patients with normal renal function.

Early and exclusive use of norepinephrine in septic shock

BACKGROUND

The timing and use of norepinephrine (noradrenaline) (NE) in septic shock remain a matter of controversy.

AIM

To study the outcome of septic patients treated with early and exclusive NE.

SETTING

Tertiary Intensive Care Unit.

PATIENTS

142 patients with septic shock.

INTERVENTION

Exclusive NE infusion within 24 hours of admission to ICU.

METHODS AND MAIN RESULTS

Retrospective analysis of data from a unit database identified 142 patients. Their median admission simplified acute physiology score (SAPS II) score was 46 [38, 56] with 98 (69%) receiving mechanical ventilation. Mean arterial pressure (MAP) at the start of NE infusion was 60 [58, 68]mmHg. NE infusion was started at a median of 1.3 [0.3, 5.0]h after ICU admission. Restoration and maintenance of target MAP was achieved initially in all patients and, in 61.3%, within 30 min. The median peak dose of NE was 0.28 [0.14, 0.61]microg/(kg min) and the duration of infusion was 88 [42, 175]h. SAPS II predicted mortality was 40.8%, however, only 34.5% (P = 0.27) died. Among the most severely ill patients (SAPS II score >56) actual mortality was 50.0% versus 74.7% predicted (P = 0.07).

CONCLUSIONS

Early and exclusive use of NE in hyperdynamic septic shock achieved a stable MAP >75 mmHg in all patients. Survival compared favorably with that predicted by illness severity scores.

Increasing Renal Blood Flow

BACKGROUND AND OBJECTIVES

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

DESIGN

Randomized, controlled, experimental animal study.

SETTING

Animal laboratory of tertiary physiology institute.

SUBJECTS

Seven Merino cross sheep were studied.

MEASUREMENTS AND RESULTS

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

RESULTS

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

CONCLUSIONS

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

Comparative effects of vasopressin, norepinephrine, and L-canavanine, a selective inhibitor of inducible nitric oxide synthase, in endotoxic shock

Norepinephrine (NE), a standard of care, AVP, an alternative candidate, and L-canavanine (LC), a selective inhibitor of inducible nitric oxide synthase, were compared for efficacy and innocuousness on global and regional hemodynamics, plasmatic and tissue lactate-to-pyruvate ratio (L/P), tissue high-energy phosphates, renal function, and tissue capillary permeability in a rat model of endotoxic normokinetic shock. Mean arterial pressure (MAP) decreased ( approximately 35%) but aortic blood flow increased during endotoxin infusion (P < 0.05 vs. control). Additionally, there was a decrease in mesenteric (MBF) and renal (RBF) blood flows along with regional-to-systemic ratio (P < 0.05 vs. control). All tested drugs restored MAP to basal levels but slightly decreased abdominal aortic flow; however, RBF and MBF remained unchanged. Endotoxin significantly decreased diuresis and inulin clearance ( approximately 3- to 4-fold), whereas AVP or LC attenuated this drop (P < 0.05 vs. control). In contrast, NE did not improve endotoxin-induced renal dysfunction. Endotoxin induced gut and lung hyperpermeability (P < 0.05 vs. control). Endotoxin-induced gut hyperpermeability was inhibited by AVP, LC, and NE. Endotoxin-induced lung hyperpermeability was further worsened by NE ( approximately 2-fold increase) but not AVP infusion (P < 0.05 vs. endotoxin). LC significantly improved endotoxin-induced pulmonary hyperpermeability. Endotoxin increased renal lactate and decreased renal ATP. NE did not change renal lactate or renal ATP. AVP and LC decreased renal lactate and normalized renal ATP. Finally, endotoxin was associated with increased lactate levels and L/P ( approximately 2- and 1.5-fold increases vs. control, respectively), whereas AVP and LC, but not NE, normalized both parameters after endotoxin challenge. These results suggest that, in a short-term endotoxic shock model, AVP improves systemic hemodynamics without side effects and has particular beneficial effects on renal function.

Norepinephrine and vital organ blood flow during experimental hyperdynamic sepsis

OBJECTIVE

To study the effect of norepinephrine (NE) infusion on cerebral, coronary, renal and mesenteric blood flow during sepsis.

DESIGN AND SETTING

Randomised placebo-controlled animal trial in the animal laboratory of university physiology institute.

ANIMALS

Seven merino cross-ewes.

INTERVENTIONS

Chronic implantation of flow probes (aorta, renal, mesenteric and coronary artery and sagittal sinus). Induction of sepsis by intravenous bolus of E. coli (3 x 10(9)). After the onset of hyperdynamic sepsis sheep were randomly allocated to either NE (0.4 microg kg(-1) min(-1)) or placebo for 6 h.

MEASUREMENTS AND RESULTS

E. coli induced hypotension, fever, oliguria, tachycardia and tachypnoea. It increased cardiac output and renal, mesenteric and coronary blood flows. Sagittal flow remained unchanged. Compared to placebo NE infusion restored mean arterial blood pressure and further increased cardiac output. The increases in renal, mesenteric and coronary blood flow were unaffected. Sagittal flow was also unaltered. Compared to placebo NE increased myocardial performance, mean urine output and creatinine clearance at 2 h.

CONCLUSIONS

We conclude that hyperdynamic sepsis increases blood flow to heart, gut and kidney and that NE further increases cardiac output, blood pressure, myocardial performance, and urine output and creatinine clearance while maintaining regional blood flow.

Dopamine does not correct oxygen consumption/oxygen delivery relation abnormality during vasomotor shock induced by interleukin-1beta

We previously showed that interleukin 1beta (IL-1beta) induces vasomotor shock and impairs the oxygen consumption (VO2)/oxygen delivery (DO2) relation by increasing the slope of the supply-independent line in rabbits. In the present study, we investigated the inotropic effect of dopamine on the VO2/DO2 abnormality induced by IL-1beta. Twelve rabbits were divided into two groups (n = 6, each) and were given 10 microg/kg of IL-1beta or saline (control) intravenously. After baseline measurements were obtained, dopamine was infused continuously at a rate of 20 microg/kg/min throughout the study in both groups. All rabbits were subjected to stepwise cardiac tamponade to reduce the DO2 to <5 mL/min/kg by inflation of a handmade balloon placed into the pericardial sac. The VO2/DO2 relation was then analyzed by the dual-line method. Dopamine failed to correct the IL-1beta-induced decrease in mean arterial pressure to the baseline level. Dopamine significantly increased cardiac index in both groups, resulting in significant increases in DO2 (IL-1beta, 28.5 +/- 6.0 mL/min/kg from baseline 24.1 +/- 3.5 mL/min/kg; control, 27.7 +/- 2.9 mL/min/kg from baseline 22.9 +/- 2.9 mL/min/kg), but did not affect VO2 (IL-1beta, 10.0 +/- 0.5 mL/min/kg from baseline 9.9 +/- 0.7 mL/min/kg; control, 10.2 +/- 0.4 mL/min/kg from baseline 10.2 +/- 0.2 mL/min/kg). The IL-1beta group showed a significantly greater supply-independent line slope than that of controls (IL-1beta, y = 0.14x + 6.3; control, y = 0.06x + 8.6) during stepwise decreases in DO2. These results indicate that continuous infusion of dopamine at 20 microg/kg/min increases DO2 but does not correct the vasomotor disturbance or VO2/DO2 abnormality caused by IL-1beta.

Effect of increasing norepinephrine dosage on regional blood flow in a porcine model of endotoxin shock

OBJECTIVE

To evaluate the effect of a norepinephrine-induced differential increase in mean arterial pressure on splanchnic and renal perfusion in a porcine model of volume-resuscitated endotoxic shock.

DESIGN

Prospective, controlled, acute interventional study.

SETTING

Animal research laboratory.

SUBJECTS

Fourteen landrace pigs, seven treated with norepinephrine and seven used as endotoxemic controls.

INTERVENTIONS

In an acute endotoxic shock model, norepinephrine was used to reverse hypotension in seven fluid-resuscitated pigs, anesthetized with alpha-chloralose and equipped with flow probes around the portal vein and renal artery, renal and jejunal mucosal laser Doppler flowmetry, and jejunal tonometry. Mean arterial pressure was increased by 10 and then 20 mm Hg above the shock level with norepinephrine. Seven shocked, fluid-resuscitated only animals served as the comparison group.

MEASUREMENTS AND MAIN RESULTS

Measurements were performed before 2-hr endotoxin infusion and at the end of each increased level of mean arterial pressure. Raising mean arterial pressure with norepinephrine by 10 mm Hg significantly increased cardiac output, systemic oxygen extraction, and portal vein blood flow; stabilized metabolic acidosis; and tended to restore renal and jejunal mucosal flows to preshock levels. Increasing mean arterial pressure by 20 mm Hg further increased cardiac output and oxygen delivery but without improving portal vein, renal artery, and jejunal mucosal blood flows.

CONCLUSIONS

Norepinephrine, administered to increase mean arterial pressure by 10 mm Hg in an acute model of volume-resuscitated endotoxic shock, improved systemic and regional perfusion. The administration of norepinephrine to increase mean arterial pressure 20 mm Hg above shock did not increase renal and splanchnic blood flows, despite an enhanced cardiac output.

Noradrenaline and the kidney: friends or foes?

Septic shock, systemic inflammation and pharmacological vasodilatation are often complicated by systemic hypotension, despite aggressive fluid resuscitation and an increased cardiac output. If the physician wishes to restore arterial pressure (>80-85 mmHg), with the aim of sustaining organ perfusion pressure, the administration of systemic vasopressor agents, such as noradrenaline, becomes necessary. Because noradrenaline induces vasoconstriction in many vascular beds (visibly in the skin), however, it may decrease renal and visceral blood flow, impairing visceral organ function. This unproven fear has stopped clinicians from using noradrenaline more widely. In vasodilated states, unlike in normal circulatory conditions, however, noradrenaline may actually improve visceral organ blood flow. Animal studies show that the increased organ perfusion pressures achieved with noradrenaline improve the glomerular filtration rate and renal blood flow. There are no controlled human data to define the effects of noradrenaline on the kidney, but many patient series show a positive effect on glomerular filtration rate and urine output. There is no reason to fear the use of noradrenaline. If it is used to support a vasodilated circulation with a normal or increased cardiac output, it is likely to be the kidney's friend not its foe.

Effects of alpha - and beta -adrenergic stimulation on hepatosplanchnic perfusion and oxygen extraction in endotoxic shock

OBJECTIVE

To examine the effects of adrenergic stimulation on hepatosplanchnic perfusion, oxygen extraction, and tumor necrosis factor-alpha production during endotoxic shock.

DESIGN

In vivo, prospective, randomized, controlled, repeated-measures, experimental study.

SETTING

Experimental physiology laboratory in a university teaching hospital.

SUBJECTS

Twenty-one anesthetized and mechanically ventilated dogs.

INTERVENTIONS

An intrapericardial catheter was positioned. Catheters for blood sampling were inserted into the right femoral artery, hepatic vein, portal vein, and pulmonary artery. Ultrasonic flow probes were placed around the portal vein, the hepatic artery, the mesenteric artery, the left renal artery, and the left femoral artery. Animals received 2 mg/kg of Escherichia coli endotoxin, followed by fluid resuscitation. Seven dogs received intravenous isoproterenol (0.1 microg/kg x min(-1)), seven received phenylephrine (1 microg/kg x min(-1)), and seven served as controls. Thirty minutes later, cardiac tamponade was introduced to study organ perfusion and tissue oxygen extraction capabilities.

MAIN RESULTS

The isoproterenol group had a higher cardiac index and stroke index and lower systemic vascular resistance than the other groups. The phenylephrine group had a higher arterial pressure but a lower cardiac index than the isoproterenol group. The isoproterenol group had a higher hepatic artery blood flow than the other groups and a higher portal and mesenteric flow than the control group. Liver and gut mucosal blood flow was greater in the isoproterenol than in the phenylephrine group. The isoproterenol group had a lower global critical oxygen delivery than the other groups (8.8 +/- 1.3 vs. 13.1 +/- 2.0 (control) and 11.8 +/- 3.3 mL/kg x min(-1) (phenylephrine); both p < .05) and a higher liver critical oxygen extraction ratio than the control group. Isoproterenol tended to attenuate, but phenylephrine significantly increased, blood tumor necrosis factor levels.

CONCLUSIONS

During endotoxic shock, beta-stimulation can improve hepatosplanchnic perfusion and enhance tissue oxygen extraction capabilities, whereas alpha-stimulation does not. In addition, alpha-adrenergic stimulation can increase tumor necrosis factor levels.

Diaspirin cross-linked Hb and norepinephrine prevent the sepsis-induced increase in critical O(2) delivery

We hypothesized that support of arterial perfusion pressure with diaspirin cross-linked Hb (DCLHb) would prevent the sepsis-induced attenuation in the systemic O(2) delivery-O(2) uptake relationship. Awake septic rats were treated with a chronic infusion of DCLHb or a reference treatment [norepinephrine (NE)] to increase mean arterial pressure by 10-20% over 18 h. Septic and sham control groups received normal saline. Isovolemic hemodilution to create anemic hypoxia was then performed in a metabolic box during continuous measurement of systemic O(2) uptake. O(2) delivery was calculated from hemodynamic variables, and the critical point of O(2) delivery (DO(2 crit)) was determined using piecewise regression analysis of the O(2) delivery-O(2) uptake relationship. Sepsis increased DO(2 crit) from 4.99 +/- 0.17 to 6.69 +/- 0.42 ml x min(-1) x 100 g(-1) (P < 0.01), while O(2) extraction capacity was decreased (P < 0.05). DCLHb and NE infusion prevented the sepsis-induced increase in DO(2 crit) [4.56 +/- 0.42 ml x min(-1) x 100 g(-1) (P < 0.01) and 5.04 +/- 0.56 ml x min(-1) x 100 g(-1) (P < 0.05), respectively]. This was explained by a 59% increase in O(2) extraction capacity in the DCLHb group compared with septic controls (P < 0.05), whereas NE treatment decreased systemic O(2) uptake in anemic hypoxia (1.51 +/- 0.08 vs. 1.87 +/- 0.1 ml x min(-1) x 100 g(-1) in septic controls, P < 0.05). We conclude that DCLHb ameliorated O(2) extraction capacity in the septic microcirculation, whereas NE decreased the metabolic demands of the tissues.

Norepinephrine and N(G)-monomethyl-L-arginine in hyperdynamic septic shock in pigs: effects on intestinal oxygen exchange and energy balance

OBJECTIVES

To compare the effects of norepinephrine (NOR) and the nonselective nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), on intestinal blood flow, oxygen exchange, and energy metabolism over 24 hrs of hyperdynamic, normotensive porcine endotoxic shock.

DESIGN

Prospective, randomized, experimental study with repeated measures.

SETTING

Investigational animal laboratory.

SUBJECTS

Twenty-seven pigs were divided into three groups: seven animals received no vasopressor therapy (ETX) during endotoxic shock; ten animals were treated with NOR; and ten animals were treated with L-NMMA.

INTERVENTIONS

Pigs were anesthetized, mechanically ventilated, and instrumented. Eight hours later, endotoxic shock was initiated by an infusion of Escherichia coli lipopolysaccharide. Animals were resuscitated by hetastarch directed to maintain the intrathoracic blood volume and a mean arterial pressure (MAP) of >60 mm Hg. Twelve hours after the start of the endotoxin infusion, NOR or L-NMMA was administered for 12 hrs in the treatment groups to maintain a MAP at preshock levels.

MEASUREMENTS AND MAIN RESULTS

ETX caused a continuous fall in MAP, despite a sustained increase in the cardiac output achieved by fluid resuscitation. NOR maintained MAP at preshock levels because of a further rise in cardiac output, whereas hemodynamic stabilization during L-NMMA resulted from systemic vasoconstriction. NOR increased portal venous blood flow concomitant with decreased intestinal oxygen extraction, whereas L-NMMA influenced neither portal venous blood flow nor intestinal oxygen extraction. Mean capillary hemoglobin oxygen saturation of the ileal mucosa as well as the frequency distributions reflecting microcirculatory oxygen availability remained unchanged as well. Nevertheless, portal venous pH similarly decreased and portal venous lactate/pyruvate ratios increased in all three groups. The arterial-ileal mucosal PCO2 gap progressively increased in the ETX and L-NMMA groups, whereas NOR blunted this response.

CONCLUSIONS

Neither treatment could reverse the ETX-induced derangements of cellular energy metabolism as reflected by the increased portal venous lactate/pyruvate ratios. The NOR-induced attenuation of ileal mucosal acidosis was possibly caused by a different pattern of blood flow redistribution compared with L-NMMA.

Strong vasopressor support may be futile in the intensive care unit patient with multiple organ failure

OBJECTIVE

The aim of the study was to determine the prognosis in patients who needed norepinephrine treatment in our institution in relation to the degree of organ failure and the evolution of the disease process.

DESIGN

Retrospective case note analysis of outcome of those patients who needed norepinephrine according to our institutional regimen.

PATIENTS

A total of 100 consecutive patients admitted to our 31-bed medical-surgical intensive care unit (ICU) who were treated with norepinephrine for severe hypotension and evidence of end-organ hypoperfusion unresponsive to both fluid resuscitation and dopamine treatment at 20 microg/kg/min.

MEASUREMENTS

The degree of organ dysfunction at the time of starting norepinephrine treatment was assessed by the sequential organ failure assessment (SOFA) score. The time before starting norepinephrine treatment was defined as the time elapsed between ICU admission and that of starting norepinephrine administration. The patients were defined as survivors or nonsurvivors according to their ICU outcome.

RESULTS

There were relationships between mortality and the degree of organ dysfunction and mortality and the duration of ICU stay before starting norepinephrine treatment. The mortality rate was 100% in the 30 patients with a total SOFA score of >12 and a delay before starting norepinephrine treatment of >1 day. The mortality rate of the other patients was 63%. The lowest mortality was seen in patients with lower SOFA scores and early norepinephrine administration after admission.

CONCLUSIONS

Both the time of starting norepinephrine treatment after admission to the ICU and the degree of organ dysfunction have an important bearing on subsequent outcome. Although norepinephrine may be a lifesaving catecholamine in some cases, its administration to patients who have already developed multiple organ failure during their stay in the ICU is associated with a poor outcome.

Effects of dobutamine on gastric mucosal perfusion and hepatic metabolism in patients with septic shock

We prospectively evaluated the effects of dobutamine on gastric mucosal perfusion and hepatocytic clearance in patients with septic shock. After resuscitation with volume expansion and norepinephrine (12 patients) as needed, 14 hemodynamically stable patients (median age: 60 yr, median SAPS II score: 47) were given an infusion of 7.5 microg/kg/min dobutamine for 1 h. Gastric mucosal perfusion and hepatocytic clearance were assessed with tonometry and indocyanine green (ICG) elimination, respectively. All measurements were made before dobutamine infusion, after 1 h of dobutamine infusion, and 1 h after the infusion ended. Cardiac output (thermodilution technique) increased with dobutamine from a baseline median level of 4.0 L/min/m(2) (range: 1.7 to 7.4 L/min/m(2)) to 5.0 L/min/m(2) (range: 3.5 to 8.9 L/min/m(2)) (p = 0.004) and returned to baseline levels after dobutamine infusion ended. The gastric-arterial PCO(2) difference decreased from a baseline median level of 13 mm Hg (range: 5 to 54 mm Hg) to 7 mm Hg (range: 5 to 48 mm Hg) (p = 0.005). ICG elimination was low in all patients at baseline (median plasma disappearance rate: 12.2%; range: 7.6 to 16.2%) and did not change significantly during or after dobutamine infusion. In summary, dobutamine increases gastric mucosal perfusion but does not alter hepatocytic clearance in patients with septic shock. The absence of a beneficial effect of dobutamine on hepatocytic clearance may be related to profound alterations in hepatocellular metabolism during septic shock.

The 21-aminosteroid U74389G enhances hepatic blood flow and preserves sinusoidal endothelial cell function and structure in endotoxin-shocked dogs

BACKGROUND

21-Aminosteroids are potent anti-inflammatory and antioxidant drugs that provide remarkable endothelial protection in different models of tissue ischemia-reperfusion and inflammation. The effects of 21-aminosteroids in sepsis, a highly inflammatory condition leading to panendothelial activation and injury, are largely uninvestigated. We therefore explored the effects of the 21-aminosteroid U74386G on hepatic blood flow, endothelial cell function, and sinusoidal structure in a canine model of fluid-resuscitated, hyperdynamic endotoxic shock.

MATERIALS AND METHODS

Following invasive hemodynamic monitoring and placement of ultrasonic flow probes around the common hepatic artery and the portal vein, 12 anesthetized dogs received 2 mg/kg iv of Escherichia coli endotoxin, followed by generous saline infusion, before randomization into two groups. One group (N = 6) received U74389G as an iv bolus of 80 microg/kg, followed by a continuous infusion of 10 microg/kg. min. The other group (N = 6) received an equivalent volume of vehicle. Hyaluronic acid was measured in plasma for in vivo evaluation of endothelial cell function. Liver biopsies were taken after 4 h of endotoxic shock and prepared for light and electron microscopic examination.

RESULTS

Compared with the vehicle-treated controls, U74389G maintained a higher blood flow in the hepatic artery and in the portal vein, without markedly influencing the systemic hemodynamic response. The endotoxin-induced increase in plasma hyaluronic acid levels was significantly attenuated following U74389G treatment (70 +/- 14 vs 188 +/- 24 ng/mL after 3 h of endotoxic shock; P < 0.05). Morphological studies showed that the U74389G-treated group had less sinusoidal endothelial cell damage together with a dramatic reduction of neutrophil infiltration into the liver tissue.

CONCLUSION

U74389G can preserve the functional and structural integrity of endothelial cells in the hepatic sinusoid during hyperdynamic endotoxic shock. This endothelial-protective effect was associated with a better maintained hepatic blood flow and a significant attenuation of inflammatory liver injury.

Effects of norepinephrine on the renal vasculature in normal and endotoxemic dogs

Septic shock is often complicated by systemic hypotension despite normal or increased cardiac output. Restoration of arterial pressure usually requires the administration of systemic vasopressor agents, such as norepinephrine. However, because norepinephrine induces vasoconstriction in other vascular beds, it may decrease visceral blood flow, impairing visceral organ function. Because sepsis is often associated with impaired peripheral vascular responsiveness, we hypothesized that, unlike in normal circulatory conditions, norepinephrine would improve visceral organ blood flow in sepsis by selectively increasing organ perfusion pressure. Thus, in nine pentobarbital-anesthetized, mechanically ventilated dogs, we measured the effect of norepinephrine infusion (0.3 microgram/kg/min) on renal, hepatic, and portal steady-state pressure-flow relations (P/Q) and the dynamic vascular P/Q, created by transient inferior vena caval occlusion, under basal and endotoxic conditions. Norepinephrine increased organ perfusion pressures during both control and endotoxemic conditions. However, even after controlling for the pressure effect using a general linear model, NE was associated with an increase in renal blood flow both before and after endotoxin administration. We conclude that, unlike the effects of administering norepinephrine under baseline conditions, norepinephrine infusion during endotoxic shock actually increases renal blood flow and that this effect is not the result of an increase in perfusion pressure alone.

Intrahepatocellular erythrocyte inclusions and increased calcium precipitation in canine endotoxic shock

AIMS

To investigate the electron microscopic localization of membrane-bound and exchangeable calcium with specific calcium precipitation techniques during endotoxic shock in the dog.

METHODS

Ten pentobarbital anesthetized, mechanically ventilated, and paralyzed dogs were studied. Six dogs received 2 mg/kg E. coli endotoxin i.v. followed by a continuous 0.9% saline infusion to restore and maintain baseline cardiac filling pressures. Four dogs served as time-matched controls. Each experiment lasted for 3 h. After the completion of study, the livers of four endotoxic and two control dogs were fixed by perfusion of 3% glutaraldehyde via the portal vein. Liver sections were then prepared for electron microscopy and calcium localization studies.

RESULTS

Hepatocytes of endotoxic animals completely lost their plasma membrane-bound calcium. The most severely damaged cells showed extensive "blebbing" of the plasma membrane and contained numerous cytoplasmic erythrocyte inclusions. Endotoxin administration also caused excessive calcium precipitation inside hepatocytes in areas with pronounced sinusoidal damage.

CONCLUSIONS

In this acute model of fluid-resuscitated endotoxic shock in dogs, the use of specific calcium localization techniques enables the demonstration of disturbances in hepatocellular calcium handling, which appear to be closely related to structural alterations of the hepatocyte cell membrane. Erythrocyte uptake by hepatocytes is a previously undescribed phenomenon in canine endotoxic shock and may serve as an additional histologic marker of ultrastructural cell (membrane) damage.