Low dose norepinephrine in patients with septic shock and oliguria: effects on afterload, urine flow, and oxygen transport

From a pressure-guided to a perfusion-centered resuscitation strategy in septic shock: Critical literature review and illustrative case

PURPOSE

To support a paradigm shift in the management of septic shock from pressure-guided to perfusion-centered, expected to improve outcome while reducing adverse effects from vasopressor therapy and aggressive fluid resuscitation.

MATERIAL AND METHODS

Critical review of the literature cited in support of vasopressor use to achieve a predefined mean arterial pressure (MAP) of 65 mmHg and review of pertinent clinical trials and studies enabling deeper understanding of the hemodynamic pathophysiology supportive of a perfusion-centered approach, accompanied by an illustrative case.

RESULTS

Review of the literature cited by the Surviving Sepsis Campaign revealed lack of controlled clinical trials supporting outcome benefits from vasopressors. Additional literature review revealed adverse effects associated with vasopressors and worsened outcome in some studies. Vasopressors increase MAP primarily by peripheral vasoconstriction and in occasions by a modest increase in cardiac output when using norepinephrine. Thus, achieving the recommended MAP of 65 mmHg using vasopressors should not be presumed indicative that organ perfusion has been restored. It may instead create a false sense of hemodynamic stability hampering shock resolution.

CONCLUSIONS

We propose focusing the hemodynamic management of septic shock on reversing organ hypoperfusion instead of attaining a predefined MAP target as the key strategy for improving outcome.

Renal autoregulation in experimental septic shock and its response to vasopressin and norepinephrine administration

Evidence suggests that septic shock patients with chronic arterial hypertension may benefit from resuscitation targeted to achieve higher blood pressure values than other patients, possibly as a result of altered renal autoregulation. The effects of different vasopressor agents on renal autoregulation may be important in this context. We investigated the effects of arginine vasopressin (AVP) and norepinephrine (NE) on renal autoregulation in ovine septic shock. Sepsis was induced by fecal peritonitis. When shock developed (decrease in mean arterial pressure to <65 mmHg and no fluid-responsiveness), animals were randomized to receive NE or AVP in a crossover design. Before the switch to the second vasopressor, the first vasopressor was discontinued for 30 minutes to ensure complete washout of the first vasopressor. Renal autoregulation was evaluated by recording the change in renal blood flow (RBF) in response to manual, stepwise reductions in renal inflow pressure. In this model, the lower limit of renal autoregulation was not significantly altered 6 hours after sepsis induction (59±9 vs. 64±7 mmHg at baseline, p=0.096). After development of shock, the autoregulatory threshold was lower with AVP than with NE (59±5 vs. 65±7 mmHg, p=0.010). However, RBF was higher with NE both at the start of autoregulatory measurements (206±58 vs. 170±52 mL/min; p=0.050) and at the autoregulatory threshold (191±53 vs. 150±47 mL/min; p=0.008). As vasopressors may have different effects on renal autoregulation, blood pressure management in patients with septic shock should be individualized and take into account drug-specific effects.

Renal perfusion in sepsis: from macro- to microcirculation

The pathogenesis of sepsis-associated acute kidney injury is complex and likely involves perfusion alterations, a dysregulated inflammatory response, and bioenergetic derangements. Although global renal hypoperfusion has been the main target of therapeutic interventions, its role in the development of renal dysfunction in sepsis is controversial. The implications of renal hypoperfusion during sepsis probably extend beyond a simple decrease in glomerular filtration pressure, and targeting microvascular perfusion deficits to maintain tubular epithelial integrity and function may be equally important. In this review, we provide an overview of macro- and microcirculatory dysfunction in experimental and clinical sepsis and discuss relationships with kidney oxygenation, metabolism, inflammation, and function.

Acute kidney injury following acute pancreatitis: A review

BACKROUND. Acute kidney injury (AKI) is a common serious complication of severe acute pancreatitis (SAP) and an important marker of morbidity and mortality in critically ill septic patients. AKI due to severe acute pancreatitis can be the result of hypoxemia, release of pancreatic amylase from the injured pancreas with impairment of renal microcirculation, decrease in renal perfusion pressure due to abdominal compartment syndrome, intraabdominal hypertension or hypovolemia. Endotoxins and reactive oxygen species (ROS) also play an important role in the pathophysiology of SAP and AKI. Knowledge of the pathophysiology and diagnosis of AKI following SAP might improve the therapeutic outcome of critically ill patients.

METHODS AND RESULTS

An overview of the pathophysiology, diagnosis and potential treatment options based on a literature search of clinical human and experimental studies from 1987 to 2013.

CONCLUSIONS

Early recognition of AKI and SAP in order to prevent severe complication like septic shock, intraabdominal hypertension or abdominal compartment syndrome leading to multiple organ dysfunction syndrome is a crucial tool of therapeutic measures in intensive care.

2013 WSES guidelines for management of intra-abdominal infections

Despite advances in diagnosis, surgery, and antimicrobial therapy, mortality rates associated with complicated intra-abdominal infections remain exceedingly high.The 2013 update of the World Society of Emergency Surgery (WSES) guidelines for the management of intra-abdominal infections contains evidence-based recommendations for management of patients with intra-abdominal infections.

Norepinephrine increases cardiac preload and reduces preload dependency assessed by passive leg raising in septic shock patients

OBJECTIVE

To assess the effects of norepinephrine on cardiac preload, cardiac index, and preload dependency during septic shock.

DESIGN

Prospective interventional study.

SETTING

Medical Intensive Care Unit.

PATIENTS

We included 25 septic shock patients (62 ± 13 yrs old, Simplified Acute Physiology Score II 53 ± 12, lactate 3.5 ± 2.1 mmol/L, all receiving norepinephrine at baseline at 0.24 [25%-75% interquartile range: 0.12-0.48] μg/kg/min) with a positive passive leg raising test (defined by an increase in cardiac index ≥ 10%) and a diastolic arterial pressure ≤ 40 mm Hg.

INTERVENTIONS

We performed a passive leg raising test (during 1 min) at baseline. Immediately after, we increased the dose of norepinephrine (to 0.48 [0.36-0.71] μg/kg/min) and, when the hemodynamic status was stabilized, we performed a second passive leg raising test (during 1 min). We finally infused 500 mL saline.

MEASUREMENTS AND MAIN RESULTS

Increasing the dose of norepinephrine significantly increased central venous pressure (+23% ± 12%), left ventricular end-diastolic area (+9% ± 6%), E mitral wave (+19% ± 23%), and global end-diastolic volume (+9% ± 6%). Simultaneously, cardiac index significantly increased by 11% ± 7%, suggesting that norepinephrine had recruited some cardiac preload reserve. The second passive leg raising test increased cardiac index to a lesser extent than the baseline test (13% ± 8% vs. + 19% ± 6%, p < .05), suggesting that norepinephrine had decreased the degree of preload dependency. Volume infusion significantly increased cardiac index by 26% ± 15%. However, cardiac index increased by <15% in four patients (fluid unresponsive patients) while the baseline passive leg raising test was positive in these patients. In three of these four patients, the second passive leg raising test was also negative, i.e., the second passive leg raising test (after norepinephrine increase) predicted fluid responsiveness with a sensitivity of 95 [76-99]% and a specificity of 100 [30-100]%.

CONCLUSIONS

In septic patients with a positive passive leg raising test at baseline suggesting the presence of preload dependency, norepinephrine increased cardiac preload and cardiac index and reduced the degree of preload dependency.

Inotrope and vasopressor therapy of septic shock

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

WSES consensus conference: Guidelines for first-line management of intra-abdominal infections

Intra-abdominal infections are still associated with high rate of morbidity and mortality.A multidisciplinary approach to the management of patients with intra-abdominal infections may be an important factor in the quality of care. The presence of a team of health professionals from various disciplines, working in concert, may improve efficiency, outcome, and the cost of care.A World Society of Emergency Surgery (WSES) Consensus Conference was held in Bologna on July 2010, during the 1st congress of the WSES, involving surgeons, infectious disease specialists, pharmacologists, radiologists and intensivists with the goal of defining recommendations for the early management of intra-abdominal infections.This document represents the executive summary of the final guidelines approved by the consensus conference.

Inotrope and vasopressor therapy of septic shock

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

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.

The cardiopulmonary effects of dobutamine and norepinephrine in isoflurane-anesthetized foals

OBJECTIVE

To evaluate the cardiovascular effects of norepinephrine (NE) and dobutamine (DB) in isoflurane-anesthetized foals.

STUDY DESIGN

Prospective laboratory study.

METHODS

Norepinephrine (0.05, 0.10, 0.20, and 0.40 microg kg(-1) minute(-1)) and dobutamine (2.5, 5.0, and 10 microg kg(-1) minute(-1)) were alternately administered to seven healthy, 1- to 2-week-old isoflurane-anesthetized foals. Arterial and pulmonary arterial blood pressure, right atrial pressure, pulmonary artery occlusion pressure, heart rate, body temperature, cardiac output, arterial and mixed venous blood pH, partial pressure of carbon dioxide, partial pressure of oxygen [arterial partial pressure of oxygen (PaO(2)) and mixed venous partial pressure of oxygen (PvO(2))], and packed cell volume were measured. Standard base excess, bicarbonate concentration, systemic and pulmonary vascular resistance, cardiac index (CI), stroke volume, left and right stroke work indices, oxygen delivery (DO(2)), consumption, and extraction were calculated. Results Norepinephrine infusion resulted in significant increases in arterial and pulmonary arterial pressure, systemic and pulmonary vascular resistance indices, and PaO(2); heart rate was decreased. Dobutamine infusion resulted in significant increases in heart rate, stroke volume index, CI, and arterial and pulmonary arterial blood pressure. Systemic and pulmonary vascular resistance indices were decreased while the ventricular stroke work indices increased. The PaO(2) decreased while DO(2) and oxygen consumption increased. Oxygen extraction decreased and PvO(2) increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Norepinephrine primarily augments arterial blood pressure while decreasing CI. Dobutamine primarily augments CI with only modest increases in arterial blood pressure. Both NE and DB could be useful in the hemodynamic management of anesthetized foals.

Catecholamines and vasopressin during critical illness

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

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.

Vasopressor and inotropic support in septic shock: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for vasopressor and inotropic support in septic shock that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and to improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSION

An arterial catheter should be placed as soon as possible in patients with septic shock. Vasopressors are indicated to maintain mean arterial pressure of <65 mm Hg, both during and following adequate fluid resuscitation. Norepinephrine or dopamine are the vasopressors of choice in the treatment of septic shock. Norepinephrine may be combined with dobutamine when cardiac output is being measured. Epinephrine, phenylephrine, and vasopressin are not recommended as first-line agents in the treatment of septic shock. Vasopressin may be considered for salvage therapy. Low-dose dopamine is not recommended for the purpose of renal protection. Dobutamine is recommended as the agent of choice to increase cardiac output but should not be used for the purpose of increasing cardiac output above physiologic levels.

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

OBJECTIVE

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

DATA SOURCE

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

STUDY SELECTION

Both human studies and relevant animal studies were considered.

DATA SYNTHESIS

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

CONCLUSIONS

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

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.

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.

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.

Therapeutic Options for the Treatment of Impaired Gut Function

Abstract. Tissue hypoxia, especially in the splanchnic area, is still considered to be an important cofactor in the pathogenesis of multiple organ failure. Therefore, the specific effects of the various therapeutic interventions on splanchnic perfusion and oxygenation are of particular interest. Restoring and maintaining oxygen transport and tissue oxygenation is the most important step in the supportive treatment of patients with sepsis and impaired gut perfusion. Therefore, supportive treatment should be focused on an adequate volume resuscitation and appropriate use of vasoactive drugs. Adequate volume loading may be the most important step in the treatment of patients with septic shock. An elevated oxygen delivery may be beneficial in some patients, but the increase of oxygen delivery should be guided by the measurement of parameters assessing global and regional oxygenation. Forcing an elevation in oxygen delivery by the use of very high dosages of catecholamines can be harmful. Vasopressors should be used for achieving an adequate perfusion pressure. For norepinephrine, no negative effects on gut perfusion have been demonstrated. Epinephrine and dopamine should be avoided because they seem to redistribute blood flow away from the splanchnic region. There are no convincing data yet to support the routine use of low-dose dopamine or dopexamine to improve an impaired gut perfusion. There is even evidence that low-dose dopamine may reduce the mucosal perfusion in the gut in some patients. It has been suggested that dopexamine can improve splanchnic perfusion, but because these effects remain somewhat controversial, a general recommendation for dopexamine to improve gut perfusion is not justified.

Renal blood flow regulation, autoregulation, and vasomotor nephropathy

Renal blood flow and renal perfusion pressure are regulated by two control mechanisms. The first, extrinsic, actually involves a complex interaction of vasomotor effects between opposing neurohormonal systems. The second, intrinsic mechanism, renal autoregulation, depends on changes in afferent arteriolar tone in response to the renal perfusion pressure itself. This article reviews these two mechanisms, how they normally respond to stress, and the clinical implications of certain situations in which these control mechanisms are disrupted.

Effects of norepinephrine plus dobutamine or norepinephrine alone on left ventricular performance of septic shock patients

OBJECTIVE

To determine the hemodynamic effects of the combination of norepinephrine-dobutamine in adult patients with septic shock. Specifically, we tested the hypothesis that norepinephrine in addition to dobutamine would improve cardiac index (CI) and stroke volume index (SVI) and increase left-ventricular afterload.

DESIGN

Prospective, descriptive, interventional study with no control group.

SETTING

Intensive care unit of a university hospital.

PATIENTS

Fourteen patients (group 1) were transferred to the intensive care unit from other wards with septic shock not responsive to dobutamine infusion, low blood pressure (systolic blood pressure of <90 mm Hg), clinical and laboratory signs of infection, clinical signs of poor organ perfusion, and blood lactate of >2.0 mmol/L. They were enrolled and treated by the addition of norepinephrine, while the dose of dobutamine remained constant. Three of these patients required additional fluid loading to achieve adequate ventricular filling (pulmonary capillary wedge pressure [PCWP], 12-15 mm Hg). These patients were compared with 12 patients with septic shock with high CI (CI > 5/min/m2, and other signs as outlined previously) who were treated with norepinephrine alone (group 2).

INTERVENTIONS

Patients in group 1 were maintained with the same dobutamine dose, and norepinephrine was added (initial dose, 0.5 microg/kg/min, and increments of 0.3 microg/kg/min) until the correction of mean arterial blood pressure (MAP > or =75 mm Hg). Patients in group 2 received norepinephrine following the same protocol.

MEASUREMENTS AND MAIN RESULTS

At study entry, group 1 patients receiving dobutamine had similar MAPs but were significantly older and had significantly lower CIs and SVIs and higher systemic vascular resistance than group 2 patients. In group 1 norepinephrine, in addition to dobutamine, significantly increased MAP, CI, SVI, left ventricular stroke work index (LVSWI), and systemic vascular resistance (SVR). No change in heart rate or PCWP was observed. In group 2, norepinephrine used alone did not modify CI or SVI and it significantly improved MAP, LVSWI, and SVR. No changes in heart rate or PCWP were observed. Blood lactate was significantly decreased in both groups. Comparing the two groups, in response to norepinephrine titrated to increase MAP to a similar concentration, patients with dobutamine-resistant septic shock had a statistically significantly greater increase in CI and SVI than patients treated with norepinephrine alone. There were no other significant differences in hemodynamic and metabolic responses to norepinephrine between groups 1 and 2.

CONCLUSION

The addition of norepinephrine to treatment of patients with septic shock unresponsive to dobutamine significantly improves MAP, CI, SVI, and LVSWI. A different pattern of evolution was observed if norepinephrine was used alone in younger patients with higher CI at study entry, increases in MAP and LVSWI, and no concomitant change in CI or SVI. The use of norepinephrine in dobutamine-resistant septic shock may have some beneficial implications for the treatment of patients with inadequate myocardial performance associated with low SVR.

Supportive therapy of the sepsis syndrome

Adequate volume loading may be the most important step in the treatment of patients with septic shock. Techniques allowing us to achieve and tightly control volume loading and regional perfusion are considered to be helpful. An elevated oxygen delivery may be beneficial in some patients but the increase of oxygen delivery should be guided by the measurement of parameters assessing global and regional oxygenation. Forcing an increase in oxygen delivery by the use of very high dosages of catecholamines can be harmful. Vasopressors should be used for achieving an adequate perfusion pressure. For norepinephrine, no negative effects on regional perfusion have been demonstrated. Epinephrine and dopamine should be avoided because they seem to redistribute blood flow away from the splanchnic region. There are no convincing data yet to support the routine use of low dose dopamine or dopexamine in patients with sepsis. Neither low dose dopamine nor dopexamine has been proven to prevent renal failure in septic patients. Furthermore, there is evidence that low dose dopamine may reduce mucosal perfusion in the gut in some patients. There is some suggestion that dopexamine can improve splanchnic perfusion but since these effects remain somewhat controversial, there is no reason for a general recommendation for dopexamine in septic patients.

Is it time to reposition vasopressors and inotropes in sepsis?

OBJECTIVES

To review the literature on the current use of vasopressors and inotropes in patients with sepsis and sepsis syndrome with respect to the choice of agent, therapeutic end points, and safe and effective doses to be used. To examine the available evidence that supports or refutes goal-directed therapy toward supranormal oxygen transport in optimizing the outcome of critically ill sepsis syndrome patients.

DATA SOURCES

All pertinent English and French articles dealing with hemodynamic support with selected vasopressors and inotropic agents in human sepsis and sepsis syndrome retrieved from a computerized MEDLINE search from 1985 to 1994.

STUDY SELECTION

Clinical studies with norepinephrine, epinephrine, phenylephrine, dopamine, and dobutamine in sepsis syndrome were considered if goal-directed therapy with oxygen transport variables was utilized. Emphasis was placed on prospective, randomized, controlled comparative trials. However, open-label, observational, and comparative studies, or case series, were also evaluated when limited data were available.

DATA EXTRACTION

From the selected studies, information was obtained regarding patient population, dosing regimen, type of therapeutic goals or end points (hemodynamic, or normal vs. supranormal oxygen transport variables) and outcome data (e.g., achievement of goals, resolution of the episode, mortality rate, and development of end-organ dysfunction).

DATA SYNTHESIS

When used in larger than usual doses, epinephrine, norepinephrine, and phenylephrine uniformly increased hemodynamic values. Epinephrine may increase oxygen transport values more reliably than norepinephrine. Dobutamine doses in the range of 2.5 to 6 microgram/kg/min increase oxygen transport variables and hemodynamics to predetermined goals in only 30% to 70% of patients. Larger infusion rates offer no further benefits.

CONCLUSIONS

Insufficient evidence exists to support goal-directed therapy with vasopressors and inotropes in the treatment of sepsis syndrome. No definitive recommendations can be made about the superiority of a vasopressor or inotropic agent due to the lack of data. However, it may be that evaluation of vasopressors earlier in sepsis syndrome will yield more promising results. Large, comparative, controlled trials assessing mortality rate and development of multiple organ system dysfunction are needed.

Effects of catecholamines on regional perfusion and oxygenation in critically ill patients

Multiple organ failure is the major cause of death in patients with sepsis. Bacterial translocation from the gut is considered to induce and maintain sepsis. Therefore, the splanchnic region plays an important role in the pathogenesis and treatment of sepsis. There is evidence for a very high risk of imbalance between oxygen delivery and oxygen consumption especially in the splanchnic region. Consequently, there is a crucial interest whether it is possible to influence the splanchnic perfusion by specific catecholamines. Unfortunately, only a few, conflicting studies have looked at the effects of the various catecholamines on regional blood flow. Therefore, a clear recommendation for a specific catecholamine regimen in septic shock is impossible. Furthermore, it is unknown whether the choice of a specific catecholamine in the treatment of septic shock affects the patient's outcome. In most patients, the use of vasopressors is indispensable because adequate haemodynamic perfusion pressure is not achieved with fluid therapy alone. The negative effects of vasopressors on splanchnic perfusion are known from studies carried out under non septic conditions. Norepinephrine and dopamine in doses of 10 micrograms/kg/min in septic animals are without negative effects on splanchnic perfusion. Preliminary results show Preliminary results show a decrease in splanchnic oxygenation in patients with septic shock treated with epinephrine. Catecholamines with beta mimetic effects are often used to increase DO2. The question as to whether dobutamine or dopamine should be used first in treatment of septic shock cannot be answered yet. Whether treatment with low dose dopamine or dopexamine actually improves renal function and splanchnic oxygenation is the purpose of ongoing studies.

Efficacy of epinephrine therapy in shock complicating pulmonary embolism

A case of shock and pulmonary embolism in a 57-year-old woman is described in which hemodynamics were unresponsive both to usual therapy (volume loading, dobutamine, thrombolysis) and then to norepinephrine. Epinephrine proved to be effective, above all by strong beta 1-inotropic effect.

The effects of norepinephrine on hemodynamics and renal function in severe septic shock states

OBJECTIVE

To investigate the effect of norepinephrine (NE) on hemodynamics, oxygen metabolism and renal function in patients with severe septic shock.

DESIGN

Prospective study.

SETTING

Post-operative ICU in a municipal general hospital.

PATIENTS

The study included 56 patients with extreme low resistance states due to abdominal sepsis, who remained hypertensive (MAP < 60 mmHg) despite optimal fluid therapy and dopamine > 20 micrograms/kg/min and cumulative doses of dopamine and dobutamine > 30 micrograms/kg/min, respectively.

INTERVENTIONS

After registration of baseline values dopamine was reduced to 2.5 micrograms/kg/min, and norepinephrine was administered starting at a dose of 0.05 micrograms/kg/min until a mean arterial pressure of more than 60 mmHg could be maintained.

MEASUREMENTS AND RESULTS

During norepinephrine infusion (dosage ranging between 0.1-2 micrograms/kg/min, mean dose rate: 0.4 micrograms/kg/min) mean arterial pressure and systemic vascular resistance index increased significantly (p < 0.001). After 8 h a significant increase in stroke volume (p < 0.05) and decrease in heart rate (p < 0.05) could be observed. There was no significant change in cardiac index (CI), oxygen delivery (O2AVI) and oxygen consumption (VO2I). Creatinine clearance increased significantly (p < 0.005) from a control value of 75 +/- 37 ml/min to 102 +/- 43 ml/min after 48 h NE-treatment.

CONCLUSION

Our results suggest that norepinephrine can be used safely in the treatment of severe septic shock states. Mean arterial pressure and glomerular filtration rate improved markedly without deleterious effects on CI, O2AVI and VO2I.

Catecholamines in critical care. The commonly used catecholamines: receptor and clinical profile, indications and dosages

The pharmacology, pattern of receptor activation and resulting clinical impact of the currently most widely used intravenous catecholamines are reviewed. A brief physiological description of the alpha, beta and dopaminergic receptors is used in order to explain the clinical effects of norepinephrine, epinephrine, isoproterenol, dopamine, dobutamine and dopexamine. Each drug is discussed separately according to receptor profile, indications, dosages and current application in critical care. Tables are provided for comparison of relative strengths of these drugs regarding receptor activation, haemodynamic effects, organ perfusion and recommended dosages. The use of combinations of catecholamines to meet a variety of circulatory demands is commented upon.

Septic shock. When patients fail to respond to conventional therapy

Patients in septic shock require rapid evaluation and prompt initiation of therapy with appropriate antibiotics and fluids. When fluids do not restore perfusion, dopamine (Dopastat, Inotropin) therapy is begun. Some patients who fail to respond to these measures will respond to a combination of low-dose dopamine and regulation of blood pressure with norepinephrine (Levophed).

[Hemodynamic effects of dobutamine in hyperkinetic septic shock treated with norepinephrine]

A prospective study of the haemodynamic effects of dobutamine was carried out in six men and four women suffering from hyperkinetic septic shock, already treated with noradrenaline and dopamine. All ten patients had septic shock, defined as a mean arterial blood pressure of less than 70 mmHg and an urine output under 15 ml.h-1, persisting despite fluid loading, associated with positive blood cultures, increased white blood cell counts, and a septic area. Initial treatment consisted in fluid loading, so as to increase cardiac output whilst keeping pulmonary wedge pressure (Ppw) between 8 and 10 mmHg. Dopamine was then added, up to a dose of 15-20 micrograms.kg-1.min-1, in an attempt to improve coronary and renal blood flows. In patients in whom this failed, the amounts of dopamine were then decreased, down to 3 micrograms.kg-1.min-1, and replaced by noradrenaline. When patients had as steady cardiac index (CI) greater than 3 l.min-1.m-2 and a systemic arterial resistance index (RsaI) of less than 1,800 dyn.s.cm-5.m-2 for more than 60 min, they were included in the protocol. Dopamine was then replaced by increasing doses of dobutamine (0, 5, 7.5, 10, 15 and again 0 micrograms.kg-1.min-1). The usual haemodynamic parameters were measured and calculated once a steady state had been obtained at each dose (within 20 to 30 min). Ppw was kept between 8 and 10 mmHg by fluid loading with a 4% albumin solution. At the beginning of the study, patients had a mean blood pressure of 78 +/- 6 mmHg, a CI of 4.8 +/- 1.5 l.min-1.m-2 and a RsaI of 1,285 +/- 341 dyn.s.cm-5.m-2 RsaI.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of epinephrine on hemodynamics and oxygen metabolism in dopamine-resistant septic shock

The hemodynamic effects of epinephrine were prospectively studied in 13 patients with septic shock who remained hypotensive after both fluid loading and dopamine. Hemodynamic measurements were performed before and one hour after the start of epinephrine infusion. Systolic, diastolic, and mean arterial pressure increased in all patients (p less than 0.01). Cardiac index and systemic vascular resistance increased by 34 and 32 percent, respectively (p less than 0.05), but heart rate and pulmonary vascular resistance remained unchanged. There was a concomitant increase in oxygen delivery (p less than 0.01) and oxygen consumption (p less than 0.05), the magnitude of the latter being related to baseline lactacidemia (p less than 0.01). In view of the generally recognized physiologic goals of septic shock management, we conclude that epinephrine could be an appropriate alternative where fluid loading and dopamine have failed.