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

Clinical review: interpretation of arterial pressure wave in shock states

In critically ill patients monitored with an arterial catheter, the arterial pressure signal provides two types of information that may help the clinician to interpret haemodynamic status better: the mean values of systolic, diastolic, mean and pulse pressures; and the magnitude of the respiratory variation in arterial pressure in patients undergoing mechanical ventilation. In this review we briefly discuss the physiological mechanisms responsible for arterial pressure generation, with special focus on resistance, compliance and pulse wave amplification phenomena. We also emphasize the utility of taking into consideration the overall arterial pressure set (systolic, diastolic, mean and pulse pressures) in order to define haemodynamic status better. Finally, we review recent studies showing that quantification of respiratory variation in pulse and systolic arterial pressures can allow one to identify the mechanically ventilated patients who may benefit from volume resuscitation.

Early and innovative interventions for severe sepsis and septic shock: taking advantage of a window of opportunity

The pathogenic, diagnostic and therapeutic landscape of sepsis is no longer confined to the intensive care unit: many patients from other portals of entry to care, both outside and within the hospital, progress to severe disease. Approaches that have led to improved outcomes with other diseases (e.g., acute myocardial infarction, stroke and trauma) can now be similarly applied to sepsis. Improved understanding of the pathogenesis of severe sepsis and septic shock has led to the development of new therapies that place importance on early identification and aggressive management. This review emphasizes approaches to the early recognition, diagnosis and therapeutic management of sepsis, giving the clinician the most contemporary and practical approaches with which to treat these patients.

Effekte von Dopamin auf die zelluläre und humorale Immunantwort von Patienten mit Sepsis

In vitro and in vivo studies have demonstrated that apart from its hemodynamic action dopamine can modulate immune responses. Dopamine reduces the synthesis of proinflammatory and induces the synthesis of anti-inflammatory mediators. Dopamine inhibits neurohormone synthesis, lymphocyte proliferation and platelet aggregation. It reduces the phagocytic activity of neutrophils and induces apoptosis. Particularly with regard to sepsis, where high serum dopamine levels are reached by enhanced endogenous production, exogenous application and impaired clearance, this immunomodulation may have a clinical impact. This review summarizes dopamine-mediated immunomodulating effects to advance the knowledge regarding dopamine as an immune regulator under septic conditions.

Glucocorticoids in the treatment of severe sepsis and septic shock

PURPOSE OF REVIEW

Septic shock remains one of the leading causes of death in intensive care units. In recent years, there is general use of low to moderate doses of corticosteroids in the treatment of septic shock. However, there are wide variations in the practical modality of this treatment, mainly with regard to patients' selection, treatment's dose, timing, route of administration, duration, and weaning. This review provides opinion-based guidelines for the use of corticosteroids in severe sepsis and septic shock.

RECENT FINDINGS

A summary of the latest understanding of the mechanisms of action of corticosteroids and the most recent observations in the clinical and biologic responses to corticosteroids in severe sepsis and septic shock is presented.

SUMMARY

In septic shock, intravenous hydrocortisone should be started immediately after a 250 microg corticotropin test, at a dose of 200-300 mg per day. When adrenal insufficiency is confirmed, treatment should be continued at full doses for 7 days. Otherwise, hydrocortisone should be stopped. It is worth considering adding enteral fludrocortisone at a dose of 50 microg per day for 7 days. In severe sepsis, despite growing evidence to support the use of a moderate dose of corticosteroids, the efficacy and safety of this treatment needs to be assessed in a large-scale study.

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

OBJECTIVE

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

DESIGN AND SETTING

Prospective controlled experiment in a university animal laboratory.

SUBJECTS

Eight anaesthetized dogs.

INTERVENTIONS

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

MEASUREMENTS AND RESULTS

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

CONCLUSIONS

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

Hemodynamic variables related to outcome in septic shock

OBJECTIVE

To assess the impact of hemodynamic variables on the outcome of critically ill patients in septic shock and to identify the optimal threshold values related to outcome with special reference to continuously monitored mean arterial pressure (MAP) and mixed venous oxygen saturation (SvO2).

DESIGN AND SETTING

Retrospective cohort study in a university hospital intensive care unit (ICU).

PATIENTS

All consecutive 111 patients with septic shock treated in our ICU between 1 Jan. 1999 and 30 Jan. 2002.

MEASUREMENTS AND RESULTS

The data on the hemodynamic and respiratory monitoring and circulation-related laboratory tests over the first 48 h of treatment in the ICU were collected from the clinical data management system. Data from 6 h and 48 h were analyzed separately. The 30-day mortality rate was 33% (36 of 111). Univariate analysis and forward stepwise logistic regression analysis were performed using the 30-day mortality as the primary endpoint. Mean MAP and lactate on arrival during 6 h, while mean MAP, the area of SvO2 under 70%, and mean CVP during 48 h were independently associated with mortality. MAP level of 65 mmHg and SvO2 of 70% had the highest areas under receiver characteristics curves.

CONCLUSIONS

MAP, SvO2, CVP, and initial lactate were independently associated with mortality in septic shock, with threshold values supporting those published in recent guidelines.

Short-lasting systemic and regional benefits of early crystalloid infusion after intravenous inoculation of dogs with live Escherichia coli

We investigated the systemic and regional hemodynamic effects of early crystalloid infusion in an experimental model of septic shock induced by intravenous inoculation with live Escherichia coli. Anesthetized dogs received an intravenous infusion of 1.2 x 10(10) cfu/kg live E. coli in 30 min. After 30 min of observation, they were randomized to controls (no fluids; N = 7), or fluid resuscitation with lactated Ringer's solution, 16 ml/kg (N = 7) or 32 ml/kg (N = 7) over 30 min and followed for 120 min. Cardiac index, portal blood flow, mean arterial pressure, systemic and regional oxygen-derived variables, blood lactate, and gastric PCO2 were assessed. Rapid and progressive cardiovascular deterioration with reduction in cardiac output, mean arterial pressure and portal blood flow (approximately 50, approximately 25 and approximately 70%, respectively) was induced by the live bacteria challenge. Systemic and regional territories showed significant increases in oxygen extraction and in lactate levels. Significant increases in venous-arterial (approximately 9.6 mmHg), portal-arterial (approximately 12.1 mmHg) and gastric mucosal-arterial (approximately 18.4 mmHg) PCO2 gradients were also observed. Early fluid replacement, especially with 32 ml/kg volumes of crystalloids, promoted only partial and transient benefits such as increases of approximately 76% in cardiac index, of approximately 50% in portal vein blood flow and decreases in venous-arterial, portal-arterial, gastric mucosal-arterial PCO2 gradients (7.2 +/- 1.0, 7.2 +/- 1.3 and 9.7 +/- 2.5 mmHg, respectively). The fluid infusion promoted only modest and transient benefits, unable to restore the systemic and regional perfusional and metabolic changes in this hypodynamic septic shock model.

Hemodynamic assessment of critically ill patients using echocardiography Doppler

PURPOSE OF REVIEW

The evaluation of hemodynamic status in critically ill patients is a leading recommended indication of transesophageal echocardiography in the intensive care unit. Advantages and diagnostic yield of transesophageal echocardiography in this setting are particularly relevant when considering limitations and questioned prognostic impact of pulmonary artery catheterization.

RECENT FINDINGS

Recent clinical studies have been performed to validate and assess the value of transesophageal echocardiography in determining cardiac output, cardiac preload dependence, right ventricular function, and left ventricular filling pressure. In addition, diagnostic capacity and therapeutic impact of transesophageal echocardiography have been widely reported in various intensive care unit settings.

SUMMARY

Transesophageal echocardiography appears well suited for the determination of cardiac index and to track its variations after therapeutic interventions. Although repeated measurements of left ventricular end-diastolic dimension allows to accurately track preload variations, a single determination is not reliable to predict fluid responsiveness in intensive care unit patients. Identification of preload dependence in hemodynamically unstable patients currently tends to rely mainly on dynamic parameters that use cardiopulmonary interactions under mechanical ventilation. Transesophageal echocardiography also allows to adequately assess right ventricular function and left ventricular filling pressure using combined Doppler modalities. Adequate education and training of intensivists and anesthesiologists is crucial to further develop the use of transesophageal echocardiography in the intensive care unit setting. Despite the absence of randomized controlled studies documenting transesophageal echocardiography benefits on patient outcome, present evidence and experience strongly recommend a larger use of echocardiography Doppler for a comprehensive functional hemodynamic assessment of critically ill patients with circulatory failure.

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.

Effects of levosimendan on systemic and regional hemodynamics in septic myocardial depression

OBJECTIVE

Calcium desensitization plays an important part in the pathophysiology of septic myocardial depression. We postulated that levosimendan, a new calcium sensitizer, would be beneficial in sepsis-induced cardiac dysfunction.

DESIGN AND SETTING

Prospective, randomized, controlled study in two university hospital intensive care units.

PATIENTS AND PARTICIPANTS

Twenty-eight patients with persisting left ventricular dysfunction related to septic shock after 48 h of conventional treatment including dobutamine (5 microg/kg per minute).

INTERVENTIONS

After 48 h of conventional treatment patients were randomized to receive a 24-h infusion of either levosimendan (0.2 microg/kg per minute, n=15) or dobutamine (5 microg/kg per minute, n=13).

MEASUREMENTS AND RESULTS

Data from right heart catheterization, echocardiography, gastric tonometry, laser-Doppler flowmetry, and lactate concentrations and creatinine clearance were obtained before and after the 24-h drug infusion. Dobutamine did not change systemic or regional hemodynamic variables. By contrast, at the same mean arterial pressure levosimendan decreased pulmonary artery occlusion pressure and increased cardiac index. Levosimendan decreased left ventricular end-diastolic volume and increased left ventricular ejection fraction. Levosimendan increased gastric mucosal flow, creatinine clearance, and urinary output while it decreased lactate concentrations.

CONCLUSIONS

These findings show that levosimendan improves systemic hemodynamics and regional perfusion in patients with septic cardiac dysfunction under conditions where administration of 5 microg/kg dobutamine per minute is no longer efficacious. Accordingly, our results suggest that levosimendan can be an alternative to the strategy of increasing the dose of dobutamine under such conditions.

Blood flow, not hypoxia, determines intramucosal PCO2

Monitoring tissue hypoxia in critically ill patients is a challenging task. Tissue PCO2 has long been proposed as a marker of tissue hypoxia, although there is considerable controversy on whether the rise in CO2 with hypoxia is caused by anaerobic metabolism and excess CO2 production or by the accumulation of aerobically produced CO2 in the setting of blood flow stagnation. The prevention of increases in intestinal PCO2 in aggressively resuscitated septic animals supports the notion that tissue CO2 accumulation is a function of decreases in blood flow, not of tissue hypoxia.

Septic shock

Septic shock, the most severe complication of sepsis, is a deadly disease. In recent years, exciting advances have been made in the understanding of its pathophysiology and treatment. Pathogens, via their microbial-associated molecular patterns, trigger sequential intracellular events in immune cells, epithelium, endothelium, and the neuroendocrine system. Proinflammatory mediators that contribute to eradication of invading microorganisms are produced, and anti-inflammatory mediators control this response. The inflammatory response leads to damage to host tissue, and the anti-inflammatory response causes leucocyte reprogramming and changes in immune status. The time-window for interventions is short, and treatment must promptly control the source of infection and restore haemodynamic homoeostasis. Further research is needed to establish which fluids and vasopressors are best. Some patients with septic shock might benefit from drugs such as corticosteroids or activated protein C. Other therapeutic strategies are under investigation, including those that target late proinflammatory mediators, endothelium, or the neuroendocrine system.

Effect of stress doses of hydrocortisone on S-100B vs. interleukin-8 and polymorphonuclear elastase levels in human septic shock

Stress doses of hydrocortisone are known to have immunomodulatory effects in patients with hyperdynamic septic shock. The prognosis correlates with the presence and severity of septic encephalopathy. However, neurological evaluation is influenced by the use of analgesia sedation during artificial ventilation. The objective of this study was to demonstrate the effect of stress doses of hydrocortisone during the initial phase of human septic shock on the serum values of the neurospecific protein S-100B in comparison to the inflammation markers interleukin (IL)-8 in serum and polymorphonuclear (PMN) elastase in plasma. A total of 24 consecutive patients, who met the American College of Chest Physicians/Society of Critical Care Medicine criteria for septic shock, were enrolled in this prospective, randomized, double-blind, single-center trial. The severity of illness at recruitment was graded using the Acute Physiology and Chronic Health Evaluation II and the Simplified Acute Physiology Score II scoring systems. Multi-organ dysfunction syndrome was described by the Sepsis-related Organ Failure Assessment (SOFA) score. All patients were prospectively randomized to receive either stress doses of hydrocortisone or placebo. Hydrocortisone was started in 12 patients with a loading dose of 100mg and followed by a continuous infusion of 0.18mg/kg/h for 6days. Median S-100B serum levels of the hydrocortisone group decreased from 0.32ng/mL at study entry to 0.07ng/mL 6days later without significant differences compared to the placebo group. Initial IL-8 serum levels were significantly higher in the hydrocortisone group up to 12h after study entry, and significantly decreased from 715 to 17pg/mL at the end of the observation period. Median PMN elastase plasma levels were not affected by hydrocortisone infusion. Patients with initial S-100B serum levels >0.50ng/mL revealed significantly higher SOFA scores up to 30h, IL-8 serum levels up to 12h, and PMN elastase plasma levels up to 36h after study entry than those patients with ≤0.50ng/mL. These effects were independent of the amount of fluid correction for hemodilution. Starting S-100B, IL-8 and PMN elastase values of the hydrocortisone group were within the ranges already known in patients with out-of-hospital cardiac arrest or severe traumatic brain injury. Stress doses of hydrocortisone resulted in a significant reduction in IL-8 serum, but not in S-100B serum and PMN elastase plasma concentrations in patients with hyperdynamic septic shock. For the first time, a similar extent of S-100B increase in serum of septic patients at the time of diagnosis was shown as reported for cardiac arrest or severe traumatic brain injury.