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

Investigating the relationship between high-dose norepinephrine administration and the incidence of delayed cerebral infarction in patients with aneurysmal subarachnoid hemorrhage: A single-center retrospective evaluation

BACKGROUND

One of the longest-standing treatments to prevent delayed cerebral infarction (DCI) in patients with aneurysmal subarachnoid hemorrhage (aSAH) remains raising the blood pressure to a certain level of mean arterial pressure. This may require high doses of norepinephrine, which has been associated with severe end organ damage. With this study, we aimed to investigate the effects of norepinephrine on the incidence of DCI in a clinical setting.

METHODS

We conducted a retrospective evaluation of patients with aSAH admitted to our institution between November 2018 and March 2021. Potential risk factors for DCI were analyzed and significant predictors were assessed by means of a logistic regression analysis to account for potential confounders.

RESULTS

In this study, 104 patients were included. Hereof, 39 (38%) showed radiologic signs of DCI between day three and 14 post-intervention. These patients had more frequent vasospasms (n = 37 vs. 30, p = 0.022), a higher Hunt & Hess score (3 ± 2 vs. 2 ± 1, p = 0.004), a lower initial Glasgow Coma Scale score (9 ± 5 vs. 12 ± 4, p = 0.003) and received a higher median norepinephrine dose (20,356μg vs. 6,508μg, p < 0.001). A logistic regression analysis revealed that only high-dose norepinephrine administration (OR 2.84, CI 1.56-7.8) and vasospasm (OR 3.07, CI 1.2-7.84) appeared to be significant independent risk factors for DCI.

CONCLUSION

Our results indicate a significant association between higher dose norepinephrine administration and the occurrence of DCI. Future research including greater sample sizes and a prospective setting will be necessary to further investigate the relationship.

When the Renal (Function) Begins to Fall: A Mini-Review of Acute Kidney Injury Related to Acute Respiratory Distress Syndrome in Critically Ill Patients

Acute kidney injury (AKI) is one of the most frequent causes of organ failure encountered in patients in the intensive care unit (ICU). Because of its predisposition to occur in the most critically ill patients, it is not surprising to observe a high frequency of AKI in patients with acute respiratory distress syndrome (ARDS). However, few studies have been carried out to assess the epidemiology of AKI in subgroups of ARDS patients using recommended KDIGO criteria. Moreover, the mechanisms involved in the physio-pathogenesis of AKI are still poorly understood, in particular the impact of mechanical ventilation on the kidneys. We carried out a review of the literature, focusing on the epidemiology and physiopathology of AKI in patients with ARDS admitted to the ICU. We addressed the importance of clinical management, focusing on mechanical ventilation for improving outcomes, on AKI. Finally, we also propose candidate treatment strategies and management perspectives. Our literature search showed that AKI is particularly common in ICU patients with ARDS. In association with the classic risk factors for AKI, such as comorbidities and iatrogeny, changes in mechanical ventilation parameters, which have been exclusively evaluated for their outcomes on respiratory function and death, must be considered carefully in terms of their impact on the short-term renal prognosis.

In-silico analysis of closed-loop vasopressor control of phenylephrine versus norepinephrine

We have previously demonstrated in in-silico, pre-clinical animal models, and finally human clinical studies the ability of a novel closed-loop vasopressor titration system to manage norepinephrine infusion rates to keep mean arterial blood pressure in a very tight range, reduce hypotension time and severity, and reduce overtreatment. We hypothesized that the same controller could, with modification for pharmacologic differences, suitably titrate a lower-potency longer duration of action agent like phenylephrine. Using the same physiologic simulation model as was used previously for in-silico testing of our controller for norepinephrine, we first updated the model to include a new vasopressor agent modeled after phenylephrine. A series of simulation tests patterned after our previous norepinephrine study was then conducted, this time using phenylephrine for management, in order to both test the system with the new agent and allow for comparisons between the two. Hundreds of simulation trials were conducted across a range of patient and environmental variances. The controller performance was characterized based on time in target, time above and below target, coefficient of variation, and using Varvel's criteria. The controller kept the simulated patients' MAP in target for 94% of management time in the simple scenarios and more than 85% of time in the most challenging scenarios. Varvel criteria were all under 1% error for expected pharmacologic responses and were consistent with those established for norepinephrine in our previous studies. The controller was able to acceptably titrate phenylephrine in this simulated patient model consistent with performance previously seen for norepinephrine after adjusting for the anticipated differences between the two agents.

Practice Patterns in the Initiation of Secondary Vasopressors and Adjunctive Corticosteroids during Septic Shock in the US

RATIONALE

A central component of septic shock treatment is the infusion of vasopressors, most commonly starting with norepinephrine. However, the optimal approach and practice patterns to initiating adjunctive vasopressors and corticosteroids are unknown.

OBJECTIVES

To characterize practice pattern variation in the norepinephrine dose at which secondary vasopressors and adjunctive corticosteroids are initiated and to identify factors associated with a treatment strategy favoring secondary vasopressors to a treatment strategy favoring adjunctive corticosteroids among patients with septic shock on norepinephrine.

METHODS

We used a multicenter ICU database to identify patients with septic shock who were started on norepinephrine followed by an additional vasopressor or corticosteroids. We used multi-level models to determine the hospital risk-adjusted norepinephrine dose at which additional vasopressors and corticosteroids were started, the percentage of variation in norepinephrine dose at the time of adjunctive treatment associated with hospital of admission, and the factors associated with choosing an 'additional vasopressor first' strategy vs. a 'corticosteroid first' strategy.

RESULTS

Among 4,401 patients with septic shock on norepinephrine, 1940 (44.0%) were started on adjuncts (1357 received an 'additional vasopressor first' strategy and 583 received a "corticosteroid first strategy). The hospital risk-adjusted norepinephrine dose at which vasopressors were initiated ranged 6.4 mcg/min (95% CI 5.9-7.0 mcg/min) to 92.6 mcg/min (95% CI 72.8-113.0 mcg/min). The hospital risk-adjusted norepinephrine dose at which corticosteroids was initiated ranged 3.0 mcg/min (95% CI 2.4-3.8 mcg/min) to 32.7 mcg/min (95% CI 24.9-43.0 mcg/min). 25.1% (intraclass correlation coefficient 95% CI 24.8%, 25.5%) of the variation in norepinephrine dose at which additional vasopressors were initiated was explained by hospital site after adjusting for all hospital- and patient-level covariates. Hospital of admission was strongly associated with receiving an 'additional vasopressor first' over a 'corticosteroids first' strategy (median odds ratio 3.28 (95% CI 2.81-3.83)).

CONCLUSIONS

Practice patterns for adjunctive therapies to norepinephrine during septic shock are variable and are determined in large part by hospital of admission. These results inform several future studies seeking to improve septic shock management.

New strategies to optimize renal haemodynamics

PURPOSE OF REVIEW

This review discusses the macrocirculatory and microcirculatory aspects of renal perfusion, as well as novel methods by which to measure renal blood flow. Finally, therapeutic options are briefly discussed, including renal-specific microcirculatory effects.

RECENT FINDINGS

The optimal mean arterial pressure (MAP) needed for preservation of renal function has been debated but is most likely a MAP of 60-80 mmHg. In addition, attention should be paid to renal outflow pressure, typically central venous pressure. Heterogeneity in microcirculation can exist and may be mitigated through appropriate use of vasopressors with unique microcirculatory effects. Excessive catecholamines have been shown to be harmful and should be avoided. Both angiotensin II and vasopressin may improve glomerular flow through a number of mechanisms. Macrocirculatory and microcirculatory blood flow can be measured through a number of bedside ultrasound modalities, sublingual microscopy and urinary oxygen measurement, SUMMARY: Acute kidney injury (AKI) is a common manifestation of organ failure in shock, and avoidance of hemodynamic instability can mitigate this risk. Measurement of renal haemodynamics is not routinely performed but may help to guide therapeutic goals. A thorough understanding of pathophysiology, measurement techniques and therapeutic options may allow for a personalized approach to blood pressure management in patients with septic shock and may ultimately mitigate AKI.

Vasopressor Therapy and Blood Pressure Management in the Setting of Acute Kidney Injury

Acute kidney injury (AKI) is common in the setting of shock. Hemodynamic instability is a risk factor for the development of AKI, and pathophysiological mechanisms include loss of renal perfusion pressure and impaired microcirculation. Although restoration of mean arterial pressure (MAP) may mitigate the risk of AKI to some extent, evidence on this is conflicting. Also debatable is the optimal blood pressure needed to minimize the risk of kidney injury. A MAP of 65 mm Hg traditionally has been considered adequate to maintain renal perfusion pressure, and studies have failed to consistently show improved outcomes at higher levels of MAP. Therapeutic options to support renal perfusion consist of catecholamines, vasopressin, and angiotensin II. Although catecholamines are the most studied, they are associated with adverse events at higher doses, including AKI. Vasopressin and angiotensin II are noncatecholamine options to support blood pressure and may improve microcirculatory hemodynamics through unique mechanisms, including differential vasoconstriction of efferent and afferent arterioles within the nephron. Future areas of study include methods by which clinicians can measure renal blood flow in a macrocirculatory and microcirculatory way, a personalized approach to blood pressure management in septic shock using patient-specific measures of perfusion adequacy, and novel agents that may improve the microcirculation within the kidneys without causing adverse microcirculatory effects in other organs.

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.

Emergency Department Management of Acute Kidney Injury, Electrolyte Abnormalities, and Renal Replacement Therapy in the Critically Ill

Acute kidney injury (AKI) is a common sequela of critical illness. Clinical manifestation of AKI varies and can include electrolyte abnormalities, anion gap, or non-anion-gap metabolic acidosis. Treatment strategies require careful identification of the cause of the AKI, relying on both clinical history and laboratory data. Once the cause has been identified, treatment can then target the underlying cause and avoid further insults. Conservative management should first be attempted for patients with AKI. If conservative management fails, renal replacement therapy or hemodialysis can be used.

Recognition, Diagnostics, and Management of Pediatric Severe Sepsis and Septic Shock in the Emergency Department

Several new studies have emerged in recent years that have attempted to aid emergency department providers in recognizing and treating pediatric patients with severe sepsis and septic shock. National guidelines and supporting literature are unanimous in recommendations that early recognition and timely therapeutics are necessary for improved survival and decreased morbidity. The literature is less concrete in defining how emerging advances in the field can aid in time-sensitive care of these patients. This article summarizes the recent literature as it pertains to the initial presentation of severe sepsis and septic shock in the pediatric patient within the emergency department.

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.

Development of a Physiologically Based Pharmacokinetic Modelling Approach to Predict the Pharmacokinetics of Vancomycin in Critically Ill Septic Patients

BACKGROUND AND OBJECTIVES

Sepsis is characterised by an excessive release of inflammatory mediators substantially affecting body composition and physiology, which can be further affected by intensive care management. Consequently, drug pharmacokinetics can be substantially altered. This study aimed to extend a whole-body physiologically based pharmacokinetic (PBPK) model for healthy adults based on disease-related physiological changes of critically ill septic patients and to evaluate the accuracy of this PBPK model using vancomycin as a clinically relevant drug.

METHODS

The literature was searched for relevant information on physiological changes in critically ill patients with sepsis, severe sepsis and septic shock. Consolidated information was incorporated into a validated PBPK vancomycin model for healthy adults. In addition, the model was further individualised based on patient data from a study including ten septic patients treated with intravenous vancomycin. Models were evaluated comparing predicted concentrations with observed patient concentration-time data.

RESULTS

The literature-based PBPK model correctly predicted pharmacokinetic changes and observed plasma concentrations especially for the distribution phase as a result of a consideration of interstitial water accumulation. Incorporation of disease-related changes improved the model prediction from 55 to 88% within a threshold of 30% variability of predicted vs. observed concentrations. In particular, the consideration of individualised creatinine clearance data, which were highly variable in this patient population, had an influence on model performance.

CONCLUSION

PBPK modelling incorporating literature data and individual patient data is able to correctly predict vancomycin pharmacokinetics in septic patients. This study therefore provides essential key parameters for further development of PBPK models and dose optimisation strategies in critically ill patients with sepsis.

American College of Critical Care Medicine Clinical Practice Parameters for Hemodynamic Support of Pediatric and Neonatal Septic Shock

OBJECTIVES

The American College of Critical Care Medicine provided 2002 and 2007 guidelines for hemodynamic support of newborn and pediatric septic shock. Provide the 2014 update of the 2007 American College of Critical Care Medicine "Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock."

DESIGN

Society of Critical Care Medicine members were identified from general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (2006-2014). The PubMed/Medline/Embase literature (2006-14) was searched by the Society of Critical Care Medicine librarian using the keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation, and American College of Critical Care Medicine guidelines in the newborn and pediatric age groups.

MEASUREMENTS AND MAIN RESULTS

The 2002 and 2007 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and American Heart Association/Pediatric Advanced Life Support sanctioned recommendations. The review of new literature highlights two tertiary pediatric centers that implemented quality improvement initiatives to improve early septic shock recognition and first-hour compliance to these guidelines. Improved compliance reduced hospital mortality from 4% to 2%. Analysis of Global Sepsis Initiative data in resource rich developed and developing nations further showed improved hospital mortality with compliance to first-hour and stabilization guideline recommendations.

CONCLUSIONS

The major new recommendation in the 2014 update is consideration of institution-specific use of 1) a "recognition bundle" containing a trigger tool for rapid identification of patients with septic shock, 2) a "resuscitation and stabilization bundle" to help adherence to best practice principles, and 3) a "performance bundle" to identify and overcome perceived barriers to the pursuit of best practice principles.

The intensive care medicine agenda on acute kidney injury

Acute kidney injury (AKI) is a common complication in the critically ill. Current standard of care mainly relies on identification of patients at risk, haemodynamic optimization, avoidance of nephrotoxicity and the use of renal replacement therapy (RRT) in established AKI. The detection of early biomarkers of renal tissue damage is a recent development that allows amending the late and insensitive diagnosis with current AKI criteria. Increasing evidence suggests that the consequences of an episode of AKI extend long beyond the acute hospitalization. Citrate has been established as the anticoagulant of choice for continuous RRT. Conflicting results have been published on the optimal timing of RRT and on the renoprotective effect of remote ischaemic preconditioning. Recent research has contradicted that acute tubular necrosis is the common pathology in AKI, that septic AKI is due to global kidney hypoperfusion, that aggressive fluid therapy benefits the kidney, that vasopressor therapy harms the kidney and that high doses of RRT improve outcome. Remaining uncertainties include the impact of aetiology and clinical context on pathophysiology, therapy and prognosis, the clinical benefit of biomarker-driven interventions, the optimal mode of RRT to improve short- and long-term patient and kidney outcomes, the contribution of AKI to failure of other organs and the optimal approach for assessing and promoting renal recovery. Based on the established gaps in current knowledge the trials that must have priority in the coming 10 years are proposed together with the definition of appropriate clinical endpoints.

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.

Update on Vasopressors and Inotropes in Septic Shock

Vasopressors and inotropes are used in septic shock in patients who remain hypotensive despite adequate fluid resuscitation. The goal is to increase blood pressure to optimize perfusion to organs. Generally, goal-directed therapy to supra-normal oxygen transport variables cannot be recommended due to lack of benefit. Traditionally, vasopressors and inotropes in septic shock have been started in a step-wise fashion starting with dopamine. Recent data suggest that there may be true differences among vasopressors and inotropes on local tissue perfusion as measured by regional hemodynamic and oxygen transport. When started early in septic shock, norepinephrine decreases mortality, optimizes hemodynamic variables, and improves systemic and regional (eg, renal, gastric mucosal, splanchnic) perfusion. Epinephrine causes a greater increase in cardiac index (CI) and oxygen delivery (DO2 ) and increases gastric mucosal flow, but increases lactic acid and may not adequately preserve splanchnic circulation owing to its predominant vasoconstrictive alpha (α ) effects. Epinephrine may be particularly useful when used earlier in the course of septic shock in young patients and those who do not have any known cardiac abnormalities. Unlike epinephrine, dopamine does not preferentially increase the proportion of CI that preferentially goes to the splanchnic circulation. Dopamine is further limited because it cannot increase CI by more than 35% and is accompanied by tachycardia or tachydysrhythmias. Dopamine, as opposed to norepinephrine, may worsen splanchnic oxygen consumption (VO2 ) and oxygen extraction ratio (O2 ER). Low-dose dopamine has not been shown to consistently increase the glomerular filtration rate or prevent renal failure, and, indeed, worsens splanchnic tissue oxygen use. Routine use of concurrently administered dopamine with vasopressors is not recommended. Phenylephrine should be used when a pure vasoconstrictor is desired in patients who may not require or do not tolerate the beta (β ) effects of dopamine or norepinephrine with or without dobutamine. Patients with high filling pressure and hypotension may benefit from the combination of phenylephrine and dobutamine. Investigational approaches to vasopressor-refractory hypotension in septic shock include the use of vasopressin and corticosteroids.

Current Concepts in Severe Sepsis and Septic Shock

Sepsis is a frequent cause of presentation to the emergency department (ED). Early identification and aggressive management in the ED is paramount to improving morbidity and mortality associated with sepsis. As a result, pharmacists in the ED should be familiar with and assist with the optimization of therapy for sepsis in this patient population. This article will discuss the epidemiology and economic impact of sepsis and the definitions, pathophysiology, and clinical presentation of sepsis and its related syndromes. In addition, the authors will discuss the elements related to treatment of sepsis from the Surviving Sepsis Campaign Guidelines that are particularly germane to the management of sepsis in the ED. Direct support such as source control, early broad-spectrum antibiotic therapy, hemodynamic assessment, and continuous monitoring are essential. In addition, early aggressive fluid resuscitation with titration of therapy to mixed venous oxygen saturation >70%, tight glycemic control and choice of vasopressors and inotropes have been shown to decrease mortality in sepsis. Mechanical ventilation with low tidal volumes, renal replacement therapies, early enteral nutritional support, and stress ulcer prophylaxis are also important considerations in septic patients. Controversies in therapy such as the utility of drotrecogin α activated, low-dose corticosteroids, and vasopressin are also discussed.

Blood pressure targets for vasopressor therapy: a systematic review

Physicians often prescribe vasopressors to correct pathological vasodilation and improve tissue perfusion in patients with septic shock, but the evidence to inform practice on vasopressor dosing is weak. We undertook a systematic review of clinical studies evaluating different blood pressure targets for the dosing of vasopressors in septic shock. We searched MEDLINE, EMBASE, CENTRAL (to November 2013), reference lists from included articles, and trial registries for randomized controlled trials (RCTs) and observational and crossover intervention studies comparing different blood pressure targets for vasopressor therapy in septic shock. Two reviewers independently selected eligible studies and extracted data on standardized forms. We identified 2 RCTs and 10 crossover trials but no observational studies meeting our criteria. Only one RCT measured clinical outcomes after comparing mean arterial pressure targets of 80 to 85 mmHg versus 65 to 70 mmHg. There was no effect on 28-day mortality, but confidence intervals were wide (hazard ratio, 95% confidence interval [95% CI] 0.84 - 1.38). In contrast, this intervention was associated with a greater risk of atrial fibrillation (relative risk, 2.36; 95% CI, 1.18 - 4.72) and a lower risk of renal replacement therapy in hypertensive patients (relative risk, 0.75; 95% CI, 0.57 - 1.0). Crossover trials suggest that achieving higher blood pressure targets by increasing vasopressor doses increases heart rate and cardiac index with no effect on serum lactate. Our findings underscore the paucity of clinical evidence to guide the administration of vasopressors in critically ill patients with septic shock. Further rigorous research is needed to establish an evidence base for vasopressor administration in this population.

Early norepinephrine decreases fluid and ventilatory requirements in pediatric vasodilatory septic shock

AIMS

We previously reported that vasodilatation was common in pediatric septic shock, regardless of whether they were warm or cold, providing a rationale for early norepinephrine (NE) to increase venous return (VR) and arterial tone. Our primary aim was to evaluate the effect of smaller fluid bolus plus early-NE versus the American College of Critical Care Medicine (ACCM) approach to more liberal fluid boluses and vasoactive-inotropic agents on fluid balance, shock resolution, ventilator support and mortality in children with septic shock. Secondly, the impact of early NE on hemodynamic parameters, urine output and lactate levels was assessed using multimodality-monitoring.

METHODS

In keeping with the primary aim, the early NE group (N-27) received NE after 30ml/kg fluid, while the ACCM group (N-41) were a historical cohort managed as per the ACCM Guidelines, where after 40-60ml/kg fluid, patients received first line vasoactive-inotropic agents. The effect of early-NE was characterized by measuring stroke volume variation(SVV), systemic vascular resistance index (SVRI) and cardiac function before and after NE, which were monitored using ECHO + Ultrasound-Cardiac-Output-Monitor (USCOM) and lactates.

RESULTS

The 6-hr fluid requirement in the early-NE group (88.9+31.3 to 37.4+15.1ml/kg), and ventilated days [median 4 days (IQR 2.5-5.25) to 1day (IQR 1-1.7)] were significantly less as compared to the ACCM group. However, shock resolution and mortality rates were similar. In the early NE group, the overall SVRI was low (mean 679.7dynes/sec/cm5/m2, SD 204.5), and SVV decreased from 23.8±8.2 to 18.5±9.7, p=0.005 with NE infusion suggesting improved preload even without further fluid loading. Furthermore, lactate levels decreased and urine-output improved.

CONCLUSION

Early-NE and fluid restriction may be of benefit in resolving shock with less fluid and ventilator support as compared to the ACCM approach.

Personalizing blood pressure management in septic shock

This review examines the available evidence for targeting a specific mean arterial pressure (MAP) in sepsis resuscitation. The clinical data suggest that targeting an MAP of 65-70 mmHg in patients with septic shock who do not have chronic hypertension is a reasonable first approximation. Whereas in patients with chronic hypertension, targeting a higher MAP of 80-85 mmHg minimizes renal injury, but it comes with increased risk of arrhythmias. Importantly, MAP alone should not be used as a surrogate of organ perfusion pressure, especially under conditions in which intracranial, intra-abdominal or tissue pressures may be elevated. Organ-specific perfusion pressure targets include 50-70 mmHg for the brain based on trauma brain injury as a surrogate for sepsis, 65 mmHg for renal perfusion and >50 mmHg for hepato-splanchnic flow. Even at the same MAP, organs and regions within organs may have different perfusion pressure and pressure-flow relationships. Thus, once this initial MAP target is achieved, MAP should be titrated up or down based on the measures of organ function and tissue perfusion.

RAGE controls leukocyte adhesion in preterm and term infants

BACKGROUND

Insufficient leukocyte recruitment may be one reason for the high incidence of life-threatening infections in preterm infants. Since the receptor of advanced glycation end products (RAGE) is a known leukocyte adhesion molecule and highly expressed during early development, we asked whether RAGE plays a role for leukocyte recruitment in preterm and term infants.

METHODS

Leukocyte adhesion was analyzed in dynamic flow chamber experiments using isolated leukocytes of cord blood from extremely premature (<30 weeks of gestation), moderately premature (30-35 weeks of gestation) and mature neonates (>35 weeks of gestation) and compared to the results of adults. For fluorescent microscopy leukocytes were labeled with rhodamine 6G. In the respective age groups we also measured the plasma concentration of soluble RAGE (sRAGE) by ELISA and Mac-1 and LFA-1 expression on neutrophils by flow cytometry.

RESULTS

The adhesive functions of fetal leukocytes significantly increase with gestational age. In all age groups, leukocyte adhesion was crucially dependent on RAGE. In particular, RAGE was equally effective to mediate leukocyte adhesion when compared to ICAM-1. The plasma levels of sRAGE were high in extremely premature infants and decreased with increasing gestational age. In contrast, expression of β2-Integrins Mac-1 and LFA-1 which are known ligands for RAGE and ICAM-1 did not change during fetal development.

CONCLUSION

We conclude that RAGE is a crucial leukocyte adhesion molecule in both preterm and term infants.

Vasopressor weaning in patients with septic shock

The purpose of this article is to propose optimal weaning of vasopressors in patients with septic shock. Topics discussed include pathophysiology of sepsis and septic shock, treatment guidelines for sepsis, autoregulation of blood flow, vasopressors used in septic shock, weaning recommendations, monitor alarms in the intensive care unit, and new directions in sepsis research.

[Perioperative acute kidney injury and failure]

Perioperative period is very likely to lead to acute renal failure because of anesthesia (general or perimedullary) and/or surgery which can cause acute kidney injury. Characterization of acute renal failure is based on serum creatinine level which is imprecise during and following surgery. Studies are based on various definitions of acute renal failure with different thresholds which skewed their comparisons. The RIFLE classification (risk, injury, failure, loss, end stage kidney disease) allows clinicians to distinguish in a similar manner between different stages of acute kidney injury rather than using a unique definition of acute renal failure. Acute renal failure during the perioperative period can mainly be explained by iatrogenic, hemodynamic or surgical causes and can result in an increased morbi-mortality. Prevention of this complication requires hemodynamic optimization (venous return, cardiac output, vascular resistance), discontinuation of nephrotoxic drugs but also knowledge of the different steps of the surgery to avoid further degradation of renal perfusion. Diuretics do not prevent acute renal failure and may even push it forward especially during the perioperative period when venous retourn is already reduced. Edema or weight gain following surgery are not correlated with the vascular compartment volume, much less with renal perfusion. Treatment of perioperative acute renal failure is similar to other acute renal failure. Renal replacement therapy must be mastered to prevent any additional risk of hemodynamic instability or hydro-electrolytic imbalance.

Drug absorption, distribution, metabolism and excretion considerations in critically ill adults

INTRODUCTION

All critically ill patients require medication to treat organ dysfunction. However, the pharmacokinetics of drugs used to treat these patients is complex due to frequent alterations in drug absorption, distribution, metabolism, and excretion (ADME).

AREAS COVERED

This review examines pharmacokinetic aspects of drug administration for adult intensive care unit (ICU) patients. Specifically, the authors examine the ADME changes that occur and which should be considered by clinicians when delivering drug therapy to critically ill patients.

EXPERT OPINION

Dosage pharmacokinetics determined from single-dose or limited-duration administration studies in healthy volunteers may not apply to critically ill patients. Organ dysfunction among these patients may be due to pre-existing disease or the effects of a systemic or locoregional inflammatory response precipitated by their illness. Alterations in pharmacokinetics observed among the critically ill include altered bioavailability after enteral administration, increased volume of distribution and blood-brain barrier permeability and changes in P-glycoprotein and cytochrome P450 enzyme function. However, the effect of these changes on clinically important outcomes remains uncertain and poorly studied. Future investigations should examine not only pharmacokinetic changes among the critically ill, but also whether recognition of these changes and alterations in drug therapy directed as a consequence of their observation alters patient outcomes.

Introduction to drug pharmacokinetics in the critically ill patient

Despite regular use of drugs for critically ill patients, overall data are limited regarding the impact of critical illness on pharmacokinetics (PK). Designing safe and effective drug regimens for patients with critical illness requires an understanding of PK. This article reviews general principles of PK, including absorption, distribution, metabolism, and elimination, and how critical illness can influence these parameters. In the area of drug absorption, we discuss the impact of vasopressor use, delayed gastric emptying and feeding tubes, and nutrient interactions. On the topic of drug distribution, we review fluid resuscitation, alterations in plasma protein binding, and tissue perfusion. With drug metabolism, we discuss hepatic enzyme activity, protein binding, and hepatic blood flow. Finally, we review drug elimination in the critically ill patient and discuss the impact of augmented renal clearance and acute kidney injury on drug therapies. In each section, we highlight select literature reviewing the PK impact of these conditions on a drug PK profile and, where appropriate, provide general suggestions for clinicians on how to modify drug regimens to manage PK challenges.

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.

Relation between mean arterial pressure and renal function in the early phase of shock: a prospective, explorative cohort study

INTRODUCTION

Because of disturbed renal autoregulation, patients experiencing hypotension-induced renal insult might need higher levels of mean arterial pressure (MAP) than the 65 mmHg recommended level in order to avoid the progression of acute kidney insufficiency (AKI).

METHODS

In 217 patients with sustained hypotension, enrolled and followed prospectively, we compared the evolution of the mean arterial pressure (MAP) during the first 24 hours between patients who will show AKI 72 hours after inclusion (AKIh72) and patients who will not. AKIh72 was defined as the need of renal replacement therapy or "Injury" or "Failure" classes of the 5-stage RIFLE classification (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease) for acute kidney insufficiency using the creatinine and urine output criteria. This comparison was performed in four different subgroups of patients according to the presence or not of AKI at the sixth hour after inclusion (AKIh6 as defined as a serum creatinine level above 1.5 times baseline value within the first six hours) and the presence or not of septic shock at inclusion.The ability of MAP averaged over H6 to H24 to predict AKIh72 was assessed by the area under the receiver operating characteristic curve (AUC) and compared between groups.

RESULTS

The MAP averaged over H6 to H24 or over H12 to H24 was significantly lower in patients who showed AKIh72 than in those who did not, only in septic shock patients with AKIh6, whereas no link was found between MAP and AKIh72 in the three others subgroups of patients. In patients with septic shock plus AKIh6, MAP averaged over H6 to H24 or over H12 to H24 had an AUC of 0.83 (0.72 to 0.92) or 0.84 (0.72 to 0.92), respectively, to predict AKIh72 . In these patients, the best level of MAP to prevent AKIh72 was between 72 and 82 mmHg.

CONCLUSIONS

MAP about 72 to 82 mmHg could be necessary to avoid acute kidney insufficiency in patients with septic shock and initial renal function impairment.

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.

An Official ATS/ERS/ESICM/SCCM/SRLF Statement: Prevention and Management of Acute Renal Failure in the ICU Patient: an international consensus conference in intensive care medicine

OBJECTIVES

To address the issues of Prevention and Management of Acute Renal Failure in the ICU Patient, using the format of an International Consensus Conference.

METHODS AND QUESTIONS

Five main questions formulated by scientific advisors were addressed by experts during a 2-day symposium and a Jury summarized the available evidence: (1) Identification and definition of acute kidney insufficiency (AKI), this terminology being selected by the Jury; (2) Prevention of AKI during routine ICU Care; (3) Prevention in specific diseases, including liver failure, lung Injury, cardiac surgery, tumor lysis syndrome, rhabdomyolysis and elevated intraabdominal pressure; (4) Management of AKI, including nutrition, anticoagulation, and dialysate composition; (5) Impact of renal replacement therapy on mortality and recovery.

RESULTS AND CONCLUSIONS

The Jury recommended the use of newly described definitions. AKI significantly contributes to the morbidity and mortality of critically ill patients, and adequate volume repletion is of major importance for its prevention, though correction of fluid deficit will not always prevent renal failure. Fluid resuscitation with crystalloids is effective and safe, and hyperoncotic solutions are not recommended because of their renal risk. Renal replacement therapy is a life-sustaining intervention that can provide a bridge to renal recovery; no method has proven to be superior, but careful management is essential for improving outcome.

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.

Pharmacological optimization of tissue perfusion

After fluid resuscitation, vasoactive drug treatment represents the major cornerstone for correcting any major impairment of the circulation. However, debate still rages as to the choice of agent, dose, timing, targets, and monitoring modalities that should optimally be used to benefit the patient yet, at the same time, minimize harm. This review highlights these areas and some new pharmacological agents that broaden our therapeutic options.

Clinical practice parameters for hemodynamic support of pediatric and neonatal septic shock: 2007 update from the American College of Critical Care Medicine

BACKGROUND

The Institute of Medicine calls for the use of clinical guidelines and practice parameters to promote "best practices" and to improve patient outcomes.

OBJECTIVE

2007 update of the 2002 American College of Critical Care Medicine Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock.

PARTICIPANTS

Society of Critical Care Medicine members with special interest in neonatal and pediatric septic shock were identified from general solicitation at the Society of Critical Care Medicine Educational and Scientific Symposia (2001-2006).

METHODS

The Pubmed/MEDLINE literature database (1966-2006) was searched using the keywords and phrases: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation (ECMO), and American College of Critical Care Medicine guidelines. Best practice centers that reported best outcomes were identified and their practices examined as models of care. Using a modified Delphi method, 30 experts graded new literature. Over 30 additional experts then reviewed the updated recommendations. The document was subsequently modified until there was greater than 90% expert consensus.

RESULTS

The 2002 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and AHA sanctioned recommendations. Centers that implemented the 2002 guidelines reported best practice outcomes (hospital mortality 1%-3% in previously healthy, and 7%-10% in chronically ill children). Early use of 2002 guidelines was associated with improved outcome in the community hospital emergency department (number needed to treat = 3.3) and tertiary pediatric intensive care setting (number needed to treat = 3.6); every hour that went by without guideline adherence was associated with a 1.4-fold increased mortality risk. The updated 2007 guidelines continue to recognize an increased likelihood that children with septic shock, compared with adults, require 1) proportionally larger quantities of fluid, 2) inotrope and vasodilator therapies, 3) hydrocortisone for absolute adrenal insufficiency, and 4) ECMO for refractory shock. The major new recommendation in the 2007 update is earlier use of inotrope support through peripheral access until central access is attained.

CONCLUSION

The 2007 update continues to emphasize early use of age-specific therapies to attain time-sensitive goals, specifically recommending 1) first hour fluid resuscitation and inotrope therapy directed to goals of threshold heart rates, normal blood pressure, and capillary refill 70% and cardiac index 3.3-6.0 L/min/m.

[Microcirculation of intensive care patients. From the physiology to the bedside]

The microcirculation is unique in its anatomy and physiology and is a self-contained organ system within the human body. It is the site where gas exchange and nutrient supply takes place, but it is also the site which experiences pathological alterations during various shock states and therefore compromises the oxygen supply to tissues and organs. Systemic inflammation for example leads amongst others to increased heterogeneous blood flow, formation of interstitial edema, altered viscosity, leukocyte activation, disturbances in the coagulation system, and to a breakdown of the endothelial barrier function. These alterations inevitably lead to limitations of the oxygen supply to tissues. Without interruption of these pathomechanisms, the dysfunction of the microcirculation will consequently result in organ dysfunction. In this review article a short description of the microcirculatory physiology, the interaction between the macrocirculation and the microcirculation, as well as microcirculatory alterations generated by a systemic inflammatory response will be given. Finally, various therapy options will be described, which, experimentally, can lead to an improvement in microcirculatory dysfunction.

Recent advances in sepsis and septic shock

Sepsis remains a common problem in all age groups. Recently surviving sepsis campaign has taken up a worldwide initiative by publishing international guidelines 2008 with a hope to disseminate information regarding management of sepsis for all age groups. This article presents a review of recent advances as they apply to pediatric age group supported by the available evidence with reference to standard definitions of pediatric sepsis and septic shock and management in the emergency room and pediatric intensive care unit.

Medical therapy of acute kidney injury

Pharmacologic interventions for the prevention and therapy of acute kidney injury (AKI) can be roughly divided into 2 main strategies: Optimising renal perfusion and modulation of intrarenal pathophysiological mechanisms, i.e. formation of free oxygen radicals, inflammation, tubular cast formation and renal (tubular) regeneration. Improvement of impaired renal perfusion can be achieved by optimising systemic haemodynamics by volume expansion and the appropriate use of inotropes and/or vasopressors. Up to now prospective randomised controlled trials on selective renal vasodilatation have turned out rather unsuccessful, with the exception of the adenosine antagonist theophylline, in certain indications like drug-induced renal failure or contrast nephropathy. Studies in humans on pharmacological interventions interfering with intrarenal pathophysiological mechanisms of AKI are also sparse. Investigated compounds comprise N-acetyl-cysteine, mannitol and antioxidants like selenium or vitamin C. The results are heterogeneous and a significant beneficial effect of either substance could not yet be convincingly demonstrated.

Evaluation and initial management of acute kidney injury

The evaluation and initial management of patients with acute kidney injury (AKI) should include: (1) an assessment of the contributing causes of the kidney injury, (2) an assessment of the clinical course including comorbidities, (3) a careful assessment of volume status, and (4) the institution of appropriate therapeutic measures designed to reverse or prevent worsening of functional or structural kidney abnormalities. The initial assessment of patients with AKI classically includes the differentiation between prerenal, renal, and postrenal causes. The differentiation between so-called "prerenal" and "renal" causes is more difficult, especially because renal hypoperfusion may coexist with any stage of AKI. Using a modified Delphi approach, the multidisciplinary international working group, generated a set of testable research questions. Key questions included the following: Is there a difference in prognosis between volume-responsive and volume-unresponsive AKI? Are there biomarkers whose patterns (dynamic changes) predict the severity and recovery of AKI (maximal stage of AKI, need for RRT, renal recovery, mortality) and guide therapy? What is the best biomarker to assess prospectively whether AKI is volume responsive? What is the best biomarker to assess the optimal volume status in AKI patients? In evaluating the current literature and ongoing studies, it was thought that the answers to the questions posed herein would improve the understanding of AKI, and ultimately patient outcomes.

Noradrenaline for management of septic shock refractory to fluid loading and dopamine or dobutamine in full-term newborn infants

AIM

To determine the effects of noradrenaline in full-term newborns with refractory septic shock.

METHODS

Newborns of >35 weeks' gestation with persistent septic shock, despite adequate fluid resuscitation and high dose of dopamine/dobutamine were eligible. In this prospective observational study, we recorded respiratory and hemodynamic parameters prior to and 3 h after starting noradrenaline infusion.

RESULTS

Twenty-two newborns were included (gestational age [GA] 39 +/- 1.7 weeks, birth weight (BW) 3110 +/- 780 g). Before starting noradrenaline, the infants received a mean volume expansion of 31 +/- 15 mL/kg and a mean infusion rate of dopamine of 14 +/- 5 microg/kg/min or dobutamine of 12 +/- 6 microg/kg/min. Three hours after starting noradrenaline (rate 0.5 +/- 0.4 microg/kg/min), the mean arterial blood pressure rose from 36 +/- 5 to 51 +/- 7 mmHg (p < 0.001). Urine output increased from 1 +/- 0.5 to 1.7 +/- 0.4 mL/kg/h (p < 0.05). Blood lactate concentration decreased from 4.8 +/- 2.3 to 3.3 +/- 1.8 mmol/L (p < 0.01). Despite an initial correction of hypotension, four infants died later.

CONCLUSION

Noradrenaline was effective in increasing systemic blood pressure. An increase in urine output and a decrease in blood lactate concentration suggest that noradrenaline may have improved cardiac function and tissue perfusion.