Fluid-management strategies in acute lung injury--liberal, conservative, or both?

Current Practice Review in the Management of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) presents as an acute inflammatory lung injury characterized by refractory hypoxemia and non-cardiac pulmonary edema. An estimated 10% of patients in the intensive care unit and 25% of those who are mechanically ventilated are diagnosed with ARDS. Increased awareness is warranted as mortality rates remain high and delays in diagnosing ARDS are common. The COVID-19 pandemic highlights the importance of understanding ARDS management. Treatment of ARDS can be challenging due to the complexity of the disease state and conflicting existing evidence. Therefore, it is imperative that pharmacists understand both pharmacologic and non-pharmacologic treatment strategies to optimize patient care. This narrative review provides a critical evaluation of current literature describing management practices for ARDS. A review of treatment modalities and supportive care strategies will be presented.

Early-Phase Urine Output and Severe-Stage Progression of Oliguric Acute Kidney Injury in Critical Care

Background: The relationship between urine output (UO) and severe-stage progression in the early phase of acute kidney injury (AKI) remains unclear. This study aimed to investigate the relationship between early-phase UO^6−12h [UO within 6 h after diagnosis of stage 1 AKI by Kidney Disease: Improving Global Outcomes (KDIGO) UO criteria] and severe-stage progression of AKI and to identify a reference value of early-phase UO^6−12h for guiding initial therapy in critical care.

Methods: Adult patients with UO < 0.5 ml/kg/h for the first 6 h after intensive care unit (ICU) admission (meeting stage 1 AKI by UO) and UO^6−12h ≥ 0.5 ml/kg/h were identified from the Medical Information Mart for Intensive Care (MIMIC) III database. The primary outcome was progression to stage 2/3 AKI by UO. After other variables were adjusted through multivariate analysis, generalized additive model (GAM) was used to visualize the relationship between early-phase UO^6−12h and progression to stage 2/3 AKI by UO. A two-piecewise linear regression model was employed to identify the inflection point of early-phase UO^6−12h above which progression risk significantly leveled off. Sensitivity and subgroup analyses were performed to assess the robustness of our findings.

Results: Of 2,984 individuals, 1,870 (62.7%) with KDIGO stage 1 UO criteria progressed to stage 2/3 AKI. In the multivariate analysis, early-phase UO^6−12h showed a significant association with progression to stage 2/3 AKI by UO (odds ratio, 0.40; 95% confidence interval, 0.34–0.46; p < 0.001). There was a non-linear relationship between early-phase UO^6−12h and progression of AKI. Early-phase UO^6−12h of 1.1 ml/kg/h was identified as the inflection point, above which progression risk significantly leveled off (p = 0.780). Patients with early-phase UO^6−12h ≥ 1.1 ml/kg/h had significantly shorter length of ICU stay (3.82 vs. 4.17 days, p < 0.001) and hospital stay (9.28 vs. 10.43 days, p < 0.001) and lower 30-day mortality (11.05 vs. 18.42%, p < 0.001). The robustness of our findings was confirmed by sensitivity and subgroup analyses.

Conclusions: Among early-stage AKI patients in critical care, there was a non-linear relationship between early-phase UO^6−12h and progression of AKI. Early-phase UO^6−12h of 1.1 ml/kg/h was the inflection point above which progression risk significantly leveled off.

Usefulness of bioelectrical impedance analysis and ECW ratio as a guidance for fluid management in critically ill patients after operation

We determined the relationship between changes in bioelectrical impedance analysis (BIA) parameters and response of critically ill patients to fluid therapy during early postoperative period. Associations between BIA values indicating volume status of postoperative patient and clinical outcomes were also evaluated. From May 2019 to April 2020, patients who were admitted to the surgical intensive care unit (SICU) of our institution at more than 48 h after surgery were enrolled. Volume status was measured with a portable BIA device every morning for five days from SICU admission. Overhydration was defined as the case where extracellular water (ECW) ratio > 0.390 measured by BIA. Participants were daily classified into an overhydration or a normohydration group. The relationship between daily hydration status and postoperative outcome was evaluated. Most of the 190 participants showed the overhydration status in the first 48 h after surgery. The overhydration status on day 3 was significant predictor of postoperative morbidities (OR 1.182) and in-hospital mortality (OR 2.040). SOFA score was significant factor of postoperative morbidities (OR 1.163) and in-hospital mortality (OR 3.151) except for the overhydration status on day 3. Cut-off values of overhydration status by ECW ratio at day 3 for predicting postoperative morbidities and in-hospital mortality were > 0.3985 and > 0.4145, respectively. BIA would be a useful and convenient tool to assess the volume status of patients requiring intensive fluid resuscitation in early postoperative period. Overhydration status by ECW ratio on postoperative day 3 needs careful monitoring and appropriate interventions to improve clinical outcomes.

Impact of protocolized diuresis for de-resuscitation in the intensive care unit

Objective

Administration of diuretics has been shown to assist fluid management and improve clinical outcomes in the critically ill post-shock resolution. Current guidelines have not yet included standardization or guidance for diuretic-based de-resuscitation in critically ill patients. This study aimed to evaluate the impact of a multi-disciplinary protocol for diuresis-guided de-resuscitation in the critically ill.

Methods

This was a pre-post single-center pilot study within the medical intensive care unit (ICU) of a large academic medical center. Adult patients admitted to the Medical ICU receiving mechanical ventilation with either (1) clinical signs of volume overload via chest radiography or physical exam or (2) any cumulative fluid balance ≥ 0 mL since hospital admission were eligible for inclusion. Patients received diuresis per clinician discretion for a 2-year period (historical control) followed by a diuresis protocol for 1 year (intervention). Patients within the intervention group were matched in a 1:3 ratio with those from the historical cohort who met the study inclusion and exclusion criteria.

Results

A total of 364 patients were included, 91 in the protocol group and 273 receiving standard care. Protocolized diuresis was associated with a significant decrease in 72-h post-shock cumulative fluid balance [median, IQR − 2257 (− 5676–920) mL vs 265 (− 2283–3025) mL; p < 0.0001]. In-hospital mortality in the intervention group was lower compared to the historical group (5.5% vs 16.1%; p = 0.008) and higher ICU-free days (p = 0.03). However, no statistically significant difference was found in ventilator-free days, and increased rates of hypernatremia and hypokalemia were demonstrated.

Conclusions

This study showed that a protocol for diuresis for de-resuscitation can significantly improve 72-h post-shock fluid balance with potential benefit on clinical outcomes.

Critical hemodynamic therapy oriented resuscitation helping reduce lung water production and improve survival

BACKGROUND

Increased extravascular lung water (EVLW) in shock is common in the critically ill patients. This study aimed to explore the effect of cardiac output (CO) on EVLW and its relevant influence on prognosis.

METHODS

The hemodynamic data of 428 patients with pulse-indicated continuous CO catheterization from Department of Critical Care Medicine, Peking Union Medical College Hospital were retrospectively collected and analyzed. The patients were assigned to acute respiratory distress syndrome group, cardiogenic shock group, septic shock group, and combined shock (cardiogenic and septic) group according to their symptoms. Information on 28-day mortality and renal function was also collected.

RESULTS

The CO and EVLW index (EVLWI) in the cardiogenic and combined shock groups were lower than those in the other groups (acute respiratory distress syndrome group vs. cardiogenic shock group vs. septic shock group vs. combined shock group: CO, 5.1 [4.0, 6.2] vs. 4.7 [4.0, 5.7] vs. 5.5 [4.3, 6.7] vs. 4.6 [3.5, 5.7] at 0 to 24 h, P = 0.009; 4.6 [3.8, 5.6] vs. 4.8 [4.1, 5.7] vs. 5.3 [4.4, 6.5] vs. 4.5 [3.8, 5.3] at 24 to 48 h, P = 0.048; 4.5 [4.1, 5.4] vs. 4.8 [3.8, 5.5] vs. 5.3 [4.0, 6.4] vs. 4.0 [3.2, 5.4] at 48 to 72 h, P = 0.006; EVLWI, 11.4 [8.7, 19.1] vs. 7.9 [6.6, 10.0] vs. 8.8 [7.4, 11.0] vs. 8.2 [6.7, 11.3] at 0 to 24 h, P < 0.001; 11.8 [7.7, 17.2] vs. 7.8 [6.3, 10.2] vs. 8.7 [6.6, 12.2] vs. 8.0 [6.6, 11.1] at 24 to 48 h, P < 0.001; and 11.3 [7.7, 18.7] vs. 7.5 [6.3, 10.0] vs. 8.8 [6.3, 12.2] vs. 8.4 [6.4, 11.2] at 48 to 72 h, P < 0.001. The trend of the EVLWI in the septic shock group was higher than that in the cardiogenic shock group (P < 0.05). Moreover, there existed some difference in the pulmonary vascular permeability index among the cardiogenic shock group, the septic shock group, and the combined shock group, without statistical significance (P > 0.05). In addition, there was no significant difference in tissue perfusion or renal function among the four groups during the observation period (P > 0.05). However, the cardiogenic shock group had a higher 28-day survival rate than the other three groups [log rank (Mantel-Cox) = 31.169, P < 0.001].

CONCLUSION

Tissue-aimed lower CO could reduce the EVLWI and achieve a better prognosis.

Association of perioperative weight-based fluid balance with 30-day mortality and acute kidney injury among patients in the surgical intensive care unit

PURPOSE

Perioperative positive fluid balance has negative effects on short-term outcomes, such as surgical complications, although the associations with postoperative mortality remain unclear. This study evaluated the associations of perioperative fluid balance (FB) with 30-day mortality and acute kidney injury (AKI) after postoperative intensive care unit (ICU) admission.

METHODS

This retrospective study evaluated data from adult patients who were admitted to the ICU after surgery during 2012-2016. Weight-based cumulative FB (%) was calculated for 3 time periods [postoperative day (POD) 0 (24 h), 0-1 (48 h), and 0-2 (72 h)] and was categorized as positive (≥ 5%), mild to moderate positive (5-10%), severe positive (> 10%), normal (0-5%), or negative (< 0%).

RESULTS

Data from 7896 patients were included in the analysis. The multivariable Cox regression model revealed that increased 30-day mortality was associated with positive FB groups (≥ 5%) compared to normal FB groups (0-5%) during 3 time periods [hazard ratio (HR) on POD 0 (24 h): 1.87, HR on POD 1 (48 h): 1.91, and HR on POD 2 (72 h): 4.62, all P < 0.05]. These trends were more evident in the severe positive FB group across the three time periods. Additionally, similar association was found for incidence of AKI during POD 0-2.

CONCLUSION

Perioperative cumulative weight-based FB was positively associated with increased postoperative 30-day mortality or postoperative AKI in ICU patients; this association was consistent with the positive FB on POD 0 (24 h), 0-1 (48 h), and 0-2 (72 h).

Barriers to clinical research in trauma

As with all areas of medicine, high-quality clinical research is essential to improving the care of trauma patients. This research is crucial in developing evidence-based treatments that decrease cost, decrease morbidity, and improve mortality. Trauma continues to extract a significant toll on society and is the single largest cause of years of life lost in the United States. The need to conduct high-quality clinical research in trauma is not disputed. However, significant challenges and barriers unique to the field of trauma make performing this research more difficult. It is critical to be aware of these challenges and barriers to performing clinical research involving trauma patients so these challenges can be accounted for and solutions implemented to minimize their impact on research. This review will focus on the barriers and challenges that are encountered while performing clinical research in trauma.

Principles of fluid management and stewardship in septic shock: it is time to consider the four D's and the four phases of fluid therapy

In patients with septic shock, the administration of fluids during initial hemodynamic resuscitation remains a major therapeutic challenge. We are faced with many open questions regarding the type, dose and timing of intravenous fluid administration. There are only four major indications for intravenous fluid administration: aside from resuscitation, intravenous fluids have many other uses including maintenance and replacement of total body water and electrolytes, as carriers for medications and for parenteral nutrition. In this paradigm-shifting review, we discuss different fluid management strategies including early adequate goal-directed fluid management, late conservative fluid management and late goal-directed fluid removal. In addition, we expand on the concept of the “four D’s” of fluid therapy, namely drug, dosing, duration and de-escalation. During the treatment of patients with septic shock, four phases of fluid therapy should be considered in order to provide answers to four basic questions. These four phases are the resuscitation phase, the optimization phase, the stabilization phase and the evacuation phase. The four questions are “When to start intravenous fluids?”, “When to stop intravenous fluids?”, “When to start de-resuscitation or active fluid removal?” and finally “When to stop de-resuscitation?” In analogy to the way we handle antibiotics in critically ill patients, it is time for fluid stewardship.

Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations

Although the utility and benefits of anesthesia and analgesia are irrefutable, their practice is not void of risks. Almost all drugs that produce anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity, and compensatory autoregulatory responses. Whereas anesthesia-related depression of cardiac performance and arterial vasodilation are well recognized adverse effects contributing to anesthetic risk, far less emphasis has been placed on effects impacting venous physiology and venous return. The venous circulation, containing about 65–70% of the total blood volume, is a pivotal contributor to stroke volume and cardiac output. Vasodilation, particularly venodilation, is the primary cause of relative hypovolemia produced by anesthetic drugs and is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances. Depending on factors such as patient status and monitoring, a state of relative hypovolemia may remain clinically undetected, with impending consequences owing to impaired oxygen delivery and tissue perfusion. Concurrent processes related to comorbidities, hypothermia, inflammation, trauma, sepsis, or other causes of hemodynamic or metabolic compromise, may further exacerbate the condition. Despite scientific and technological advances, clinical monitoring and treatment of relative hypovolemia still pose relevant challenges to the anesthesiologist. This short perspective seeks to define relative hypovolemia, describe the venous system’s role in supporting normal cardiovascular function, characterize effects of anesthetic drugs on venous physiology, and address current considerations and challenges for monitoring and treatment of relative hypovolemia, with focus on insights for future therapies.

Relationship between Race and the Effect of Fluids on Long-term Mortality after Acute Respiratory Distress Syndrome. Secondary Analysis of the National Heart, Lung, and Blood Institute Fluid and Catheter Treatment Trial

RATIONALE

Short-term follow-up in the Fluid and Catheter Treatment Trial (FACTT) suggested differential mortality by race with conservative fluid management, but no significant interaction.

OBJECTIVE

In a post hoc analysis of FACTT including 1-year follow-up, we sought to estimate long-term mortality by race and test for an interaction between fluids and race.

METHODS

We performed a post hoc analysis of FACTT and the Economic Analysis of Pulmonary Artery Catheters (EAPAC) study (which included 655 of the 1,000 FACTT patients with near-complete 1-year follow up). We fit a multistate Markov model to estimate 1-year mortality for all non-Hispanic black and white randomized FACTT subjects. The model estimated the distribution of time from randomization to hospital discharge or hospital death (available on all patients) and estimated the distribution of time from hospital discharge to death using data on patients after hospital discharge for patients in EAPAC. The 1-year mortality was found by combining these estimates.

RESULTS

Non-Hispanic black (n = 217, 25%) or white identified subjects (n = 641, 75%) were included. There was a significant interaction between race and fluid treatment (P = 0.012). One-year mortality was lower for black subjects assigned to conservative fluids (38 vs. 54%; mean mortality difference, 16%; 95% confidence interval, 2-30%; P = 0.027 between conservative and liberal). Conversely, 1-year mortality for white subjects was 35% versus 30% for conservative versus liberal arms (mean mortality difference, -4.8%; 95% confidence interval, -13% to 3%; P = 0.23).

CONCLUSIONS

In our cohort, conservative fluid management may have improved 1-year mortality for non-Hispanic black patients with ARDS. However, we found no long-term benefit of conservative fluid management in white subjects.

Restrictive Fluid Resuscitation Leads to Better Oxygenation than Non-Restrictive Fluid Resuscitation in Piglets with Pulmonary or Extrapulmonary Acute Respiratory Distress Syndrome

BACKGROUND

Early goal-directed therapy (EGDT) is used to reduce mortality from septic shock and could be used in early fluid resuscitation of acute respiratory distress syndrome (ARDS). The aim of the present study was to assess the effects of restrictive (RFR) and nonrestrictive fluid resuscitation (NRFR) on hemodynamics, oxygenation, pulmonary function, tissue perfusion, and inflammation in piglets with pulmonary or extrapulmonary ARDS (ARDSp and ARDSexp).

MATERIAL AND METHODS

Chinese miniature piglets (6-8 weeks; 15 ± 1 kg) were randomly divided into 2 groups (n=12/group) for establishing ARDSp and ARDSexp models, and were further divided into 2 subgroups (n=6/subgroup) for performing RFR and NRFR. Piglets were anesthetized and hemodynamic, pulmonary, and oxygenation indicators were collected at different time points for 6 hours. The goal of EGDT was set for PiCCO parameters (mean arterial pressure (MAP), urine output and cardiac index (CI), and central venous oxygen saturation (ScvO2).

RESULTS

Piglets under RFR had lower urine output compared with NRFR, as well as lower total fluid volume (P<0.05). EVLW was decreased in ARDSp+RFR and NRFR, as well as in ARDSexp+RFR, but EVLW increased in ARDSexp+NRFR (P<0.05). PaO2/FiO2 decreased in ARDSp using both methods, but was higher with RFR (P<0.05), and was increased in ARDSexp+RFR. Other pulmonary indicators were comparable. The anti-inflammatory cytokines IL-10 and LXA4 were increased in ARDSexp after RFR (P<0.05), but not in the other groups.

CONCLUSIONS

RFR led to better oxygenation in ARDSp and ARDSexp compared with NRFR, but fluid restriction improved oxygenation in ARDSexp only.

Extent, risk factors, and outcome of fluid overload after pediatric heart surgery*

OBJECTIVES

Fluid overload is associated with poor PICU outcomes in different populations. Little is known about fluid overload in children undergoing cardiac surgery. We described fluid overload after cardiac surgery, identified risk factors of worse fluid overload and also determined if fluid overload predicts longer length of PICU stay, prolonged mechanical ventilation (length of ventilation) and worse lung function as estimated by the oxygenation index.

DESIGN

Retrospective cohort study.

SETTING

Montreal Children's Hospital PICU, Montreal, Canada.

PATIENTS

Patients 18 years or younger undergoing cardiac surgery (2005-2007).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cumulative fluid overload % was calculated as [(total fluid in - out in L)/admission weight (kg) × 100] and expressed as PICU peak cumulative fluid overload % throughout admission and PICU day 2 cumulative fluid overload %. Primary outcomes were length of stay and length of ventilation. The secondary outcome was oxygenation index. Fluid overload risk factors were evaluated using stepwise linear regression. Fluid overload-outcome relations were evaluated using stepwise Cox regression (length of stay, length of ventilation) and generalized estimating equations (daily PICU cumulative fluid overload % and oxygenation index repeated measures). There were 193 eligible surgeries. Peak cumulative fluid overload % was 7.4% ± 11.2%. Fluid overload peaked on PICU day 2. Lack of past cardiac surgery (p = 0.04), cyanotic heart disease (p = 0.03), and early postoperative fluids (p = 0.0001) was independently associated with higher day 2 fluid overload %. Day 2 fluid overload % predicted longer length of stay (adjusted hazard ratio, 0.95; 95% CI, 0.92-0.99; p = 0.009) and length of ventilation (adjusted hazard ratio, 0.97; 95% CI, 0.94-0.99; p = 0.03). In patients without cyanotic heart disease, worse daily fluid overload % predicted worse daily oxygenation index.

CONCLUSION

Fluid overload occurs early after cardiac surgery and is associated with prolonged PICU length of stay and ventilation. Future fluid overload avoidance trials may confirm or refute a true fluid overload-outcome causative association.

Comparison of outcomes from sepsis between patients with and without pre-existing left ventricular dysfunction: a case-control analysis

Introduction

The aim of this study was to determine if there are differences between patients with pre-existing left ventricular dysfunction and those with normal antecedent left ventricular function during a sepsis episode in terms of in-hospital mortality and mortality risk factors when treated in accordance with a sepsis treatment algorithm.

Methods

We performed a retrospective case-control analysis of patients selected from a quality improvement database of 1,717 patients hospitalized with sepsis between 1 January 2005 and 30 June 2010. In this study, 197 patients with pre-existing left ventricular systolic dysfunction and sepsis were compared to 197 case-matched patients with normal prior cardiac function and sepsis.

Results

In-hospital mortality rates (P = 0.117) and intubation rates at 24 hours (P = 0.687) were not significantly different between cases and controls. There was no correlation between the amount of intravenous fluid administered over the first 24 hours and the PaO₂/FiO₂ ratio at 24 hours in either cases or controls (r² = 0.019 and r² = 0.001, respectively). Mortality risk factors for cases included intubation status (P = 0.016, OR = 0.356 for no intubation), compliance with a sepsis bundle (P = 0.008, OR = 3.516 for failed compliance), a source of infection other than the lung (P = 0.019, OR = 2.782), and the initial mixed venous oxygen saturation (P = 0.004, OR = 0.997). Risk factors for controls were the initial platelet count (P = 0.028, OR = 0.997) and the serum lactate level (P = 0.048, OR = 1.104). Patients with pre-existing left ventricular dysfunction who died had a lower initial mean mixed venous oxygen saturation than those who survived (61 ± 18% versus 70 ± 16%, P = 0.002).

Conclusions

Clinical outcomes were not different between septic patients with pre-existing left ventricular dysfunction and those with no cardiac disease. There was no correlation between fluid administration and oxygenation at 24 hours in either cohort. The mortality risk factor profile of patients with pre-existing left ventricular dysfunction was different when compared with control patients, and may be related to oxygen delivery determinants.

Fluid management in the critically ill child

Fluid management has a major impact on the duration, severity and outcome of critical illness. The overall strategy for the acutely ill child should be biphasic. Aggressive volume expansion to support tissue oxygen delivery as part of early goal-directed resuscitation algorithms for shock--especially septic shock--has been associated with dramatic improvements in outcome. Recent data suggest that the cost-benefit of aggressive fluid resuscitation may be more complex than previously thought, and may depend on case-mix and the availability of intensive care. After the resuscitation phase, critically ill children tend to retain free water while having reduced insensible losses. Fluid regimens that limit or avoid positive fluid balance are associated with a reduced length of hospital stay and fewer complications. Identifying the point at which patients change from the 'early shock' pattern to the later 'chronic critical illness' pattern remains a major challenge. Very little data are available on the choice of fluids, and most of the information that is available arises from studies of critically ill adults. There is therefore an urgent need for high-quality trials of both resuscitation and maintenance fluid regimens in critically ill children.

Incidence and risk factors for acute lung injury after open thoracotomy for thoracic diseases

BACKGROUND

Acute lung injury (ALI) is a major cause of morbidity and mortality after open thoracotomy. The purpose of the study was to identify the incidence and risk factors for ALI so as to prevent its occurrence and improve surgical results.

METHODS

A prospective controlled study was carried out in 364 patients undergone open thoracotomy. Fifty-eight high risk elderly patients and 56 young patients as matched controls were prospectively entered into the study. The two groups were compared to identify the possible risk factors for ALI.

RESULTS

ALI occurred exclusively in elderly patients, accounted for 2.7% of the whole series (10/364) and 7.9% of elderly patients (10/127). The mortality for patients with ALI was 30%, significantly higher than those without (1.0%, P=0.001). Upon univariate analysis, increased age, obesity, chronic obstructive pulmonary disease (COPD), poor spirometry, and positive fluid balance on postoperative day 1 were associated with increased risk of developing ALI. Upon multivariate analysis, only poor spirometry and excessive positive fluid balance on postoperative day 1 were revealed as independent risk factors for ALI.

CONCLUSIONS

ALI after open thoracotomy has a high mortality. COPD and excessive positive fluid balance on the first postoperative day are significant predictors, suggesting stringent patient selection and timely conservative fluid management may be helpful in reducing this extremely devastating complication.

Pharmacological interventions in acute respiratory distress syndrome

Pharmacological interventions are commonly considered in acute respiratory distress syndrome (ARDS) patients. Inhaled nitric oxide (iNO) and neuromuscular blockers (NMBs) are used in patients with severe hypoxemia. No outcome benefit has been observed with the systematic use of iNO. However, a sometimes important improvement in oxygenation can occur shortly after starting administration. Therefore, its ease of use and its good tolerance justify iNO optionally combined with almitirne as a rescue therapy on a trial basis. Recent data from the literature support the use of a 48-h infusion of NMBs in patients with a PaO2 to FiO2 ratio <120 mmHg. No strong evidence exists on the increase of ICU-acquired paresis after a short course of NMBs. Fluid management with the goal to obtain zero fluid balance in ARDS patients without shock or renal failure significantly increases the number of days without mechanical ventilation. On the other hand, patients with hemodynamic failure must receive early and adapted fluid resuscitation. Liberal and conservative fluid strategies therefore are complementary and should ideally follow each other in time in the same patient whose hemodynamic state progressively stabilizes. At present, albumin treatment does not appear to be justified for limitation of pulmonary edema and respiratory morbidity. Aerosolized β2-agonists do not improve outcome in patients with ARDS and one study strongly suggests that intravenous salbutamol may worsen outcome in those patients. The early use of high doses of corticosteroids for the prevention of ARDS in septic shock patients or in patients with confirmed ARDS significantly reduced the duration of mechanical ventilation but had no effect or even increased mortality. In patients with persistent ARDS after 7 to 28 days, a randomized trial showed no reduction in mortality with moderate doses of corticosteroids but an increased PaO2 to FiO2 ratio and thoracopulmonary compliance were found, as well as shorter durations of mechanical ventilation and of ICU stay. Conflicting data exist on the interest of low doses of corticosteroids (200 mg/day of hydrocortisone) in ARDS patients. In the context of a persistent ARDS with histological proof of fibroproliferation, a corticosteroid treatment with a progressive decrease of doses can be proposed.

Acute kidney injury: the beginning of the end of the dark ages

There has been enormous progress in the understanding of acute kidney injury (AKI) over the past 5 years. This article reviews some of the salient new findings, the challenges revealed by these findings and new insights into the pathogenesis of ischemic AKI. Clinical studies have demonstrated that even a small, transient rise in serum creatinine increases the risk of mortality in hospitalized patients and that a single event of AKI increases the risk for developing chronic kidney disease. Although the overall mortality rate from AKI has improved over the past 2 decades, it continues to be significant. Current treatment is focused on maintaining renal perfusion and avoiding volume overload. However, new therapeutic targets are emerging for the treatment of AKI as our understanding of the pathogenesis of ischemic injury and inflammation increases. Early diagnosis, however, continues to be challenging as the search continues for sensitive and specific biomarkers.

Get to the point in intensive care medicine--the sooner the better?

Timing of therapy plays a pivotal role in intensive care patients. Although being evident and self-explanatory, it has to be considered that the appropriateness of a specific therapeutic intervention is likewise important. In view of antibiotic therapy of critically ill patients, the available evidence supports the concept of hitting hard, early (as soon as possible and at least before the onset of shock) and appropriately. There is increasing evidence that a positive fluid balance is not only a cosmetic problem but is associated with increased morbidity. However, prospective studies are needed to elucidate whether a positive net fluid balance represents the cause or the effect of a specific disease. Since central venous pressure (CVP) is an unreliable marker of fluid responsiveness, its clinical use to guide fluid therapy is questionable. Dynamic hemodynamic parameters seem to be superior to CVP in predicting fluid responsiveness in hemodynamically unstable patients. Sedation is often used to facilitate mechanical ventilation. Since there is no best evidence-based sedation protocol, weaning strategies should take the risk of iatrogenic arterial hypotension secondary to high doses of vasodilatory sedative agents into account. In this regard, the concept of daily wake-up calls should be challenged, because higher cumulative doses of sedatives may be required. The right dose and timing for renal replacement therapy is still discussed controversially and remains a subjective decision of the attending physician. New renal biomarkers may perhaps be helpful to validate when (and how) renal replacement therapy should be performed best. Last but not least, all therapeutic interventions should take the individual co-morbidities and underlying pathophysiological conditions into account.

Pharmacotherapy for acute respiratory distress syndrome

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a continuum of a clinical syndrome of respiratory failure due to refractory hypoxia. Acute respiratory distress syndrome is differentiated from ALI by a greater degree of hypoxemia and is associated with higher morbidity and mortality. The mortality for ARDS ranges from 22-41%, with survivors usually requiring long-term rehabilitation to regain normal physiologic function. Numerous pharmacologic therapies have been studied for prevention and treatment of ARDS; however, studies demonstrating clear clinical benefit for ARDS-related mortality and morbidity are limited. In this focused review, controversial pharmacologic therapies that have demonstrated, at minimum, a modest clinical benefit are discussed. Three pharmacologic treatment strategies are reviewed in detail: corticosteroids, fluid management, and neuromuscular blocking agents. Use of corticosteroids to attenuate inflammation remains controversial. Available evidence does not support early administration of corticosteroids. Additionally, administration after 14 days of disease onset is strongly discouraged. A liberal fluid strategy during the early phase of comorbid septic shock, balanced with a conservative fluid strategy in patients with ALI or ARDS during the postresuscitation phase, is the optimum approach for fluid management. Available evidence supports an early, short course of continuous-infusion cisatracurium in patients presenting with severe ARDS. Evidence of safe and effective pharmacologic therapies for ARDS is limited, and clinicians must be knowledgeable about the areas of controversies to determine application to patient care.

The GENESIS project (GENeralized Early Sepsis Intervention Strategies): a multicenter quality improvement collaborative

BACKGROUND

Improved outcomes for severe sepsis and septic shock have been consistently observed with implementation of early best practice intervention strategies or the 6-hour resuscitation bundle (RB) in single-center studies. This multicenter study examines the in-hospital mortality effect of GENeralized Early Sepsis Intervention Strategies (GENESIS) when utilized in community and tertiary care settings.

METHODS

This study was comprised of 2 strategies to assess treatment. The first was a prospective before-and-after observational comparison of historical controls to patients receiving the RB after implementation of GENESIS in 4 community and 4 tertiary hospitals. The second was a concurrent examination comparing patients not achieving all components of the RB to those achieving all components of the RB in 1 community and 2 tertiary care hospitals after implementation of GENESIS. These 4 subgroups merged to comprise a control (historical controls treated before GENESIS and RB not achieved after GENESIS) group and treatment (patients treated after GENESIS and RB achieved after GENESIS) group for comparison.

RESULTS

The control group comprised 1554 patients not receiving the RB (952 before GENESIS and 602 RB not achieved after GENESIS). The treatment group comprised 4801 patients receiving the RB (4109 after GENESIS and 692 RB achieved after GENESIS). Patients receiving the RB (treatment group) experienced an in-hospital mortality reduction of 14% (42.8%-28.8%, P < .001) and a 5.1 day decrease in hospital length of stay (20.7 vs 15.6, P < .001) compared to those not receiving the RB (control group). Similar mortality reductions were seen in the before-and-after (43% vs 29%, P < .001) or concurrent RB not achieved versus achieved (42.5% vs 27.2%, P < .001) subgroup comparisons.

CONCLUSIONS

Patients with severe sepsis and septic shock receiving the RB in community and tertiary hospitals experience similar and significant reductions in mortality and hospital length of stay. These findings remained consistent when examined in both before-and-after and concurrent analyses. Early sepsis intervention strategies are associated with 1 life being saved for every 7 treated.

Fluid management in critically ill patients: the role of extravascular lung water, abdominal hypertension, capillary leak, and fluid balance

INTRODUCTION

Capillary leak in critically ill patients leads to interstitial edema. Fluid overload is independently associated with poor prognosis. Bedside measurement of intra-abdominal pressure (IAP), extravascular lung water index (EVLWI), fluid balance, and capillary leak index (CLI) may provide a valuable prognostic tool in mechanically ventilated patients.

METHODS

We performed an observational study of 123 mechanically ventilated patients with extended hemodynamic monitoring, analyzing process-of-care variables for the first week of ICU admission. The primary outcome parameter was 28-day mortality. ΔmaxEVLWI indicated the maximum difference between EVLWI measurements during ICU stay. Patients with a ΔmaxEVLWI <-2 mL/kg were called 'responders'. CLI was defined as C-reactive protein (milligrams per deciliter) over albumin (grams per liter) ratio and conservative late fluid management (CLFM) as even-to-negative fluid balance on at least two consecutive days.

RESULTS

CLI had a biphasic course. ΔmaxEVLWI was lower if CLFM was achieved and in survivors (-2.4 ± 4.8 vs 1.0 ± 5.5 mL/kg, p = 0.001; -3.3 ± 3.8 vs 2.5 ± 5.3 mL/kg, p = 0.001, respectively). No CLFM achievement was associated with increased CLI and IAPmean on day 3 and higher risk to be nonresponder (odds ratio (OR) 2.76, p = 0.046; OR 1.28, p = 0.011; OR 5.52, p = 0.001, respectively). Responders had more ventilator-free days during the first week (2.5 ± 2.3 vs 1.5 ± 2.3, p = 0.023). Not achieving CLFM and being nonresponder were strong independent predictors of mortality (OR 9.34, p = 0.001 and OR 7.14, p = 0.001, respectively).

CONCLUSION

There seems to be an important correlation between CLI, EVLWI kinetics, IAP, and fluid balance in mechanically ventilated patients, associated with organ dysfunction and poor prognosis. In this context, we introduce the global increased permeability syndrome.

Aiming for a negative fluid balance in patients with acute lung injury and increased intra-abdominal pressure: a pilot study looking at the effects of PAL-treatment

INTRODUCTION

Achievement of a negative fluid balance in patients with capillary leak is associated with improved outcome. We investigated the effects of a multi-modal restrictive fluid strategy aiming for negative fluid balance in patients with acute lung injury (ALI).

METHODS

In this retrospective matched case-control study, we included 114 mechanically ventilated (MV) patients with ALI. We compared outcomes between a group of 57 patients receiving PAL-treatment (PAL group) and a matched control group, abstracted from a historical cohort. PAL-treatment combines high levels of positive end-expiratory pressure, small volume resuscitation with hyperoncotic albumin, and fluid removal with furosemide (Lasix®) or ultrafiltration. Effects on extravascular lung water index (EVLWI), intra-abdominal pressure (IAP), organ function, and vasopressor therapy were recorded during 1 week. The primary outcome parameter was 28-day mortality.

RESULTS

At baseline, no significant intergroup differences were found, except for lower PaO2/FIO2 and increased IAP in the PAL group (174.5 ± 84.5 vs 256.5 ± 152.7, p = 0.001; 10.0 ± 4.2 vs 8.0 ± 3.7 mmHg, p = 0.013, respectively). After 1 week, PAL-treated patients had a greater reduction of EVLWI, IAP, and cumulative fluid balance (-4.2 ± 5.6 vs -1.1 ± 3.7 mL/kg, p = 0.006; -0.4 ± 3.6 vs 1.8 ± 3.8 mmHg, p = 0.007; -1,451 ± 7,761 vs 8,027 ± 5,254 mL, p < 0.001). Repercussions on cardiovascular and renal function were limited. PAL-treated patients required fewer days of intensive care unit admission and days on MV (23.6 ± 15 vs 37.1 ± 19.9 days, p = 0.006; 14.6 ± 10.7 vs 25.5 ± 20.2 days, respectively) and had a lower 28-day mortality (28.1% vs 49.1%, p = 0.034).

CONCLUSION

PAL-treatment in patients with ALI is associated with a negative fluid balance, a reduction of EVLWI and IAP, and improved clinical outcomes without compromising organ function.

[Volume replacement in intensive care medicine]

Volume substitution represents an essential component of intensive care medicine. The amount of fluid administered, the composition and the timing of volume replacement seem to affect the morbidity and mortality of critically ill patients. Although restrictive volume strategies bear the risk of tissue hypoperfusion and tissue hypoxia in hemodynamically unstable patients liberal strategies favour the development of avoidable hypervolemia with edema and resultant organ dysfunction. However, neither strategy has shown a consistent benefit. In order to account for the heavily varying oxygen demand of critically ill patients, a goal-directed, demand-adapted volume strategy is proposed. Using this strategy, volume replacement should be aligned to the need to restore tissue perfusion and the evidence of volume responsiveness. As the efficiency of volume resuscitation for correction of tissue hypoxia is time-dependent, preload optimization should be completed in the very first hours. Whether colloids or crystalloids are more suitable for this purpose is still controversially discussed. Nevertheless, a temporally limited use of colloids during the initial stage of tissue hypoperfusion appears to represent a strategy which uses the greater volume effect during hypovolemia while minimizing the risks for adverse reactions.

Fluid management in acute lung injury and ards

ARDS is particularly characterized by pulmonary edema caused by an increase in pulmonary capillary permeability. It is considered that limiting pulmonary edema or accelerating its resorption through the modulation of fluid intake or oncotic pressure could be beneficial. This review discusses the principal clinical studies that have made it possible to progress in the optimization of the fluid state during ARDS. Notably, a randomized, multicenter study has suggested that fluid management with the goal to obtain zero fluid balance in ARDS patients without shock or renal failure significantly increases the number of days without mechanical ventilation. On the other hand, it is accepted that patients with hemodynamic failure must undergo early and adapted vascular filling. Liberal and conservative filling strategies are therefore complementary and should ideally follow each other in time in the same patient whose hemodynamic state progressively stabilizes. At present, although albumin treatment has been suggested to improve oxygenation transiently in ARDS patients, no sufficient evidence justifies its use to mitigate pulmonary edema and reduce respiratory morbidity. Finally, the resorption of alveolar edema occurs through an active mechanism, which can be pharmacologically upregluated. In this sense, the use of beta-2 agonists may be beneficial but further studies are needed to confirm preliminary promising results.

Volume loading reduces pulmonary vascular resistance in ventilated animals with acute lung injury: evaluation of RV afterload

During mechanical ventilation, increased pulmonary vascular resistance (PVR) may decrease right ventricular (RV) performance. We hypothesized that volume loading, by reducing PVR, and, therefore, RV afterload, can limit this effect. Deep anesthesia was induced in 16 mongrel dogs (8 oleic acid-induced acute lung injury and 8 controls). We measured ventricular pressures, dimensions, and stroke volumes during positive end-expiratory pressures of 0, 6, 12, and 18 cmH2O at three left ventricular (LV) end-diastolic pressures (5, 12, and 18 mmHg). Oleic acid infusion (0.07 ml/kg) increased PVR and reduced respiratory system compliance ( P < 0.05). With positive end-expiratory pressure, PVR was greater at a lower LV end-diastolic pressure. Increased PVR was associated with a decreased transseptal pressure gradient, suggesting that leftward septal shift contributed to decreased LV preload, in addition to that caused by external constraint. Volume loading reduced PVR; this was associated with improved RV output and an increased transseptal pressure gradient, which suggests that rightward septal shift contributed to the increased LV preload. If PVR is used to reflect RV afterload, volume loading appeared to reduce PVR, thereby improving RV and LV performance. The improvement in cardiac output was also associated with reduced external constraint to LV filling,; since calculated PVR is inversely related to cardiac output, increased LV output would reduce PVR. In conclusion, our results, which suggest that PVR is an independent determinant of cardiac performance, but is also dependent on cardiac output, improve our understanding of the hemodynamic effects of volume loading in acute lung injury.

Pulmonary effects of positive end-expiratory pressure and fluid therapy in experimental lung injury

The separate effects of positive end-expiratory pressure (PEEP) and intravascular volume administration on the histopathologic lung injury were not investigated in experimental lung injury previously. The authors hypothesized that high PEEP and a restrictive volume therapy would yield the best oxygenation and the least degree of lung injury. Pigs (52.8 ± 3.4 kg) underwent saline lavage-induced lung injury. The animals were ventilated either with low PEEP (mean PEEP 9 to 12 cm H₂O) and liberal volume therapy using hydroxyethyl starch (LowP/Vol+) or high PEEP (mean PEEP 21 cm H₂O) combined with recruitment maneuvers and liberal (HighP/Vol+) or restrictive volume therapy (HighP/Vol-). After 6.5 hours, lung injury was determined by using a histopathologic score evaluating overdistension, edema, exsudation, and inflammation. When volume therapy was liberal, high PEEP (HighP/Vol+) improved the Pao₂/Fio₂ index (416 ± 80 mm Hg) compared to low PEEP (LowP/Vol+, 189 ± 55 mm Hg; P < .05) but there was no difference in the median (interquartile range) lung injury score: 1.6 (1.2-1.9) and 1.9 (1.4-2.0). High PEEP with restrictive volume therapy (HighP/Vol-) did not further improve oxygenation (400 ± 55 mm Hg) but ameliorated the degree of lung injury: 0.9 (0.8-1.4) (P < .05). In lavage-induced lung injury, high PEEP improved oxygenation, but restrictive volume administration markedly reduced the lung injury score, mainly by reduced edema.

Prognostic value of extravascular lung water index in critically ill children with acute respiratory failure

PURPOSE

In critically ill adults, a reduction in the extravascular lung water index (EVLWi) decreases time on mechanical ventilation and improves survival. The purpose of this study is to assess the prognostic value of EVLWi in critically ill children with acute respiratory failure and investigate its relationships with PaO(2), PaO(2)/FiO(2) ratio, A-aDO(2), oxygenation index (OI), mean airway pressure, cardiac index, pulmonary permeability, and percent fluid overload.

METHODS

Twenty-seven children admitted to PICU with acute respiratory failure received volumetric hemodynamic and blood gas monitoring following initial stabilization and every 4 h thereafter, until discharge from PICU or death. All patients are grouped in two categories: nonsurvivors and survivors.

RESULTS

Children with a fatal outcome had higher values of EVLWi on admission to PICU, as well as higher A-aDO(2) and OI, and lower PaO(2) and PaO(2)/FIO(2) ratio. After 24 h EVLWi decreased significantly only in survivors. As a survival indicator, EVLWi has good sensitivity and good specificity. Changes in EVLWi, OI, and mean airway pressure had a time-dependent influence on survival that proved significant according to the Cox test. Survivors spent fewer hours on mechanical ventilation. We detected a correlation of EVLWi with percent fluid overload and pulmonary permeability.

CONCLUSIONS

Like OI and mean airway pressure, EVLWi on admission to PICU is predictive of survival and of time needed on mechanical ventilation.

Taking the septic patient to the operating room

The acutely septic patient is a multifaceted challenge for the anesthetist. Unlike most elective surgery patients, acutely septic patients have severe systemic disease before the physiologic insults of anesthesia and surgery. The decision to operate is usually informed by the urgent or emergent need to correct a severe surgical problem and weighed against the higher risks of morbidity and mortality from the procedure itself. The care of the septic patient in the intensive care unit can help guide operating room management. However, the acuity and time course of intraoperative events, including hemorrhage and drug-induced shock states, compel the anesthetist to respond aggressively with therapies that may or may not be strongly substantiated with long-term data in the intensive care unit setting. The anesthesiologist must place considerations concerning short-term survival from the acute insult of surgery ahead of longer-term considerations.

Hypervolemia induces and potentiates lung damage after recruitment maneuver in a model of sepsis-induced acute lung injury

Introduction

Recruitment maneuvers (RMs) seem to be more effective in extrapulmonary acute lung injury (ALI), caused mainly by sepsis, than in pulmonary ALI. Nevertheless, the maintenance of adequate volemic status is particularly challenging in sepsis. Since the interaction between volemic status and RMs is not well established, we investigated the effects of RMs on lung and distal organs in the presence of hypovolemia, normovolemia, and hypervolemia in a model of extrapulmonary lung injury induced by sepsis.

Methods

ALI was induced by cecal ligation and puncture surgery in 66 Wistar rats. After 48 h, animals were anesthetized, mechanically ventilated and randomly assigned to 3 volemic status (n = 22/group): 1) hypovolemia induced by blood drainage at mean arterial pressure (MAP)≈70 mmHg; 2) normovolemia (MAP≈100 mmHg), and 3) hypervolemia with colloid administration to achieve a MAP≈130 mmHg. In each group, animals were further randomized to be recruited (CPAP = 40 cm H₂O for 40 s) or not (NR) (n = 11/group), followed by 1 h of protective mechanical ventilation. Echocardiography, arterial blood gases, static lung elastance (Est,L), histology (light and electron microscopy), lung wet-to-dry (W/D) ratio, interleukin (IL)-6, IL-1β, caspase-3, type III procollagen (PCIII), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) mRNA expressions in lung tissue, as well as lung and distal organ epithelial cell apoptosis were analyzed.

Results

We observed that: 1) hypervolemia increased lung W/D ratio with impairment of oxygenation and Est,L, and was associated with alveolar and endothelial cell damage and increased IL-6, VCAM-1, and ICAM-1 mRNA expressions; and 2) RM reduced alveolar collapse independent of volemic status. In hypervolemic animals, RM improved oxygenation above the levels observed with the use of positive-end expiratory pressure (PEEP), but increased lung injury and led to higher inflammatory and fibrogenetic responses.

Conclusions

Volemic status should be taken into account during RMs, since in this sepsis-induced ALI model hypervolemia promoted and potentiated lung injury compared to hypo- and normovolemia.

Delta inflation: a bias in the design of randomized controlled trials in critical care medicine

INTRODUCTION

Mortality is the most widely accepted outcome measure in randomized controlled trials of therapies for critically ill adults, but most of these trials fail to show a statistically significant mortality benefit. The reasons for this are unknown.

METHODS

We searched five high impact journals (Annals of Internal Medicine, British Medical Journal, JAMA, The Lancet, New England Journal of Medicine) for randomized controlled trials comparing mortality of therapies for critically ill adults over a ten year period. We abstracted data on the statistical design and results of these trials to compare the predicted delta (delta; the effect size of the therapy compared to control expressed as an absolute mortality reduction) to the observed delta to determine if there is a systematic overestimation of predicted delta that might explain the high prevalence of negative results in these trials.

RESULTS

We found 38 trials meeting our inclusion criteria. Only 5/38 (13.2%) of the trials provided justification for the predicted delta. The mean predicted delta among the 38 trials was 10.1% and the mean observed delta was 1.4% (P < 0.0001), resulting in a delta-gap of 8.7%. In only 2/38 (5.3%) of the trials did the observed delta exceed the predicted delta and only 7/38 (18.4%) of the trials demonstrated statistically significant results in the hypothesized direction; these trials had smaller delta-gaps than the remainder of the trials (delta-gap 0.9% versus 10.5%; P < 0.0001). For trials showing non-significant trends toward benefit greater than 3%, large increases in sample size (380% - 1100%) would be required if repeat trials use the observed delta from the index trial as the predicted delta for a follow-up study.

CONCLUSIONS

Investigators of therapies for critical illness systematically overestimate treatment effect size (delta) during the design of randomized controlled trials. This bias, which we refer to as "delta inflation", is a potential reason that these trials have a high rate of negative results."Absence of evidence is not evidence of absence."

Acute lung injury after thoracic surgery

In this review, the authors discussed criteria for diagnosing ALI; incidence, etiology, preoperative risk factors, intraoperative management, risk-reduction strategies, treatment, and prognosis. The anesthesiologist needs to maintain an index of suspicion for ALI in the perioperative period of thoracic surgery, particularly after lung resection on the right side. Acute hypoxemia, imaging analysis for diffuse infiltrates, and detecting a noncardiogenic origin for pulmonary edema are important hallmarks of acute lung injury. Conservative intraoperative fluid administration of neutral to slightly negative fluid balance over the postoperative first week can reduce the number of ventilator days. Fluid management may be optimized with the assistance of new imaging techniques, and the anesthesiologist should monitor for transfusion-related lung injuries. Small tidal volumes of 6 mL/kg and low plateau pressures of < or =30 cmH2O may reduce organ and systemic failure. PEEP may improve oxygenation and increases organ failure-free days but has not shown a mortality benefit. The optimal mode of ventilation has not been shown in perioperative studies. Permissive hypercapnia may be needed in order to reduce lung injury from positive-pressure ventilation. NO is not recommended as a treatment. Strategies such as bronchodilation, smoking cessation, steroids, and recruitment maneuvers are unproven to benefit mortality although symptomatically they often have been shown to help ALI patients. Further studies to isolate biomarkers active in the acute setting of lung injury and pharmacologic agents to inhibit inflammatory intermediates may help improve management of this complex disease.

Acute pancreatitis and critical illness: a pancreatic tale of hypoperfusion and inflammation

Since it was first widely recognized at the end of the 19th century, acute pancreatitis has proven a formidable clinical challenge, frequently resulting in management within critical care settings. Because the early assessment of severity is difficult, the recognition of severe acute pancreatitis (SAP) and the implementation of critical care treatment precepts often are delayed. Although different management strategies for life-threatening features of SAP have been debated for decades, there has been little recent reduction in mortality rates, which can be as high as 30%. This article discusses severity designation at the time of diagnosis, reviews the pathophysiologic mechanisms so well characterized by the noxious combination of severe systemic inflammation and hypoperfusion, and provides a management algorithm that parallels current critical care strategies.

Clinical review: primary influenza viral pneumonia

Primary influenza pneumonia has a high mortality rate during pandemics, not only in immunocompromised individuals and patients with underlying comorbid conditions, but also in young healthy adults. Clinicians should maintain a high index of suspicion for this diagnosis in patients presenting with influenza-like symptoms that progress quickly (2 to 5 days) to respiratory distress and extensive pulmonary involvement. The sensitivity of rapid diagnostic techniques in identifying infections with the pandemic 2009 H1N1v influenza strain is currently suboptimal. The most reliable real-time reverse transcriptase-polymerase chain reaction molecular testing is available in limited clinical settings. Despite 6 months of pandemic circulation, most novel H1N1v pandemic strains remain susceptible to oseltamivir. Ensuring an appropriate oxygenation and ventilation strategy, as well as prompt initiation of antiviral therapy, is essential in management.

Dynamic changes in arterial waveform derived variables and fluid responsiveness in mechanically ventilated patients: a systematic review of the literature

OBJECTIVES

: A systematic review of the literature to determine the ability of dynamic changes in arterial waveform-derived variables to predict fluid responsiveness and compare these with static indices of fluid responsiveness. The assessment of a patient's intravascular volume is one of the most difficult tasks in critical care medicine. Conventional static hemodynamic variables have proven unreliable as predictors of volume responsiveness. Dynamic changes in systolic pressure, pulse pressure, and stroke volume in patients undergoing mechanical ventilation have emerged as useful techniques to assess volume responsiveness.

DATA SOURCES

: MEDLINE, EMBASE, Cochrane Register of Controlled Trials and citation review of relevant primary and review articles.

STUDY SELECTION

: Clinical studies that evaluated the association between stroke volume variation, pulse pressure variation, and/or stroke volume variation and the change in stroke volume/cardiac index after a fluid or positive end-expiratory pressure challenge.

DATA EXTRACTION AND SYNTHESIS

: Data were abstracted on study design, study size, study setting, patient population, and the correlation coefficient and/or receiver operating characteristic between the baseline systolic pressure variation, stroke volume variation, and/or pulse pressure variation and the change in stroke index/cardiac index after a fluid challenge. When reported, the receiver operating characteristic of the central venous pressure, global end-diastolic volume index, and left ventricular end-diastolic area index were also recorded. Meta-analytic techniques were used to summarize the data. Twenty-nine studies (which enrolled 685 patients) met our inclusion criteria. Overall, 56% of patients responded to a fluid challenge. The pooled correlation coefficients between the baseline pulse pressure variation, stroke volume variation, systolic pressure variation, and the change in stroke/cardiac index were 0.78, 0.72, and 0.72, respectively. The area under the receiver operating characteristic curves were 0.94, 0.84, and 0.86, respectively, compared with 0.55 for the central venous pressure, 0.56 for the global end-diastolic volume index, and 0.64 for the left ventricular end-diastolic area index. The mean threshold values were 12.5 +/- 1.6% for the pulse pressure variation and 11.6 +/- 1.9% for the stroke volume variation. The sensitivity, specificity, and diagnostic odds ratio were 0.89, 0.88, and 59.86 for the pulse pressure variation and 0.82, 0.86, and 27.34 for the stroke volume variation, respectively.

CONCLUSIONS

: Dynamic changes of arterial waveform-derived variables during mechanical ventilation are highly accurate in predicting volume responsiveness in critically ill patients with an accuracy greater than that of traditional static indices of volume responsiveness. This technique, however, is limited to patients who receive controlled ventilation and who are not breathing spontaneously.

Management of sepsis: early resuscitation

Key links in the chain of survival for the management of severe sepsis and septic shock are early identification and comprehensive resuscitation of high-risk patients. Multiple studies have shown that the first 6 hours of early sepsis management are especially important from a diagnostic, pathogenic, and therapeutic perspective, and that steps taken during this period can have a significant impact on outcome. The recognition of this critical time period and the robust outcome benefit realized in previous studies provides the rationale for adopting early resuscitation as a distinct intervention. Sepsis joins trauma, stroke, and acute myocardial infarction in having "golden hours," representing a critical opportunity early on in the course of disease for actions that offer the most benefit.

Propagation prevention: a complementary mechanism for "lung protective" ventilation in acute respiratory distress syndrome

OBJECTIVE

To describe the clinical implications of an often neglected mechanism through which localized acute lung injury may be propagated and intensified.

DATA EXTRACTION AND SYNTHESIS

Experimental and clinical evidence from the medical literature relevant to the airway propagation hypothesis and its consequences.

CONCLUSIONS

The diffuse injury that characterizes acute respiratory distress syndrome is often considered a process that begins synchronously throughout the lung, mediated by inhaled or blood-borne noxious agents. Relatively little attention has been paid to possibility that inflammatory lung injury may also begin focally and propagate sequentially via the airway network, proceeding mouth-ward from distal to proximal. Were this true, modifications of ventilatory pattern and position aimed at geographic containment of the injury process could help prevent its generalization and limit disease severity. The purposes of this communication are to call attention to this seldom considered mechanism for extending lung injury that might further justify implementation of low tidal volume/high positive end-expiratory pressure ventilatory strategies for lung protection and to suggest additional therapeutic measures implied by this broadened conceptual paradigm.

[Minimally invasive cardiopulmonary monitoring with the PiCCO Plus system]

Insertion of a central venous catheter and an arterial catheter would be indicated in hemodynamically unstable or severely hypoxic patients in critical care units. In this setting, cardiorespiratory monitoring by transpulmonary thermodilution (TPTD) can be considered minimally invasive given that only a single arterial thermodilution catheter and a single central venous catheter are required to be connected to a specific monitor (the PiCCO Plus, Pulsion Medical Systems, Munich, Germany). TDTP simultaneously measures cardiac output, preloading, and cardiac function in hemodynamically unstable patients and predicts the response to volume. The technique can be managed by any health care professional. In hypoxic patients, TDTP identifies cases of pulmonary edema that might benefit from a negative fluid balance, evaluates pulmonary vascular permeability, facilitates our understanding of pathophysiologic mechanisms of hypoxemia, and predicts the likelihood of deleterious hemodynamic effects of positive end-expiratory pressures.

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.

Recent developments in the diagnosis and management of severe sepsis

The last 5 years have brought dramatic changes to the care of patients with severe sepsis. While early diagnosis remains a challenge and, regrettably, a rapid, sensitive, and specific diagnostic test is still lacking, the methods to identify those critically ill patients who are likely to die have become clearer. The presence of multiple organ failure, vasopressor-dependent shock, and high values in formalized scoring methods such as the APACHE (acute physiology and chronic health evaluation) and sequential organ failure assessment systems all have some utility for outcome prediction for groups of patients. Refinements in long-used supportive practices such as lower tidal volume ventilation and enhanced glucose control have improved outcomes. A growing appreciation of the importance of timely provision of antimicrobial therapy, circulatory resuscitation, and activated protein C administration have also improved survival. Optimal treatment candidates for, and the timing and dose of some treatments (eg, corticosteroids) remain controversial and are undergoing additional study. Perhaps the most important change in the care of patients with severe sepsis is awareness that the syndrome is more common, lethal, and expensive, than previously appreciated, and as such it warrants an organized approach to care provided by experts. Although there is still much to learn, numerous studies now indicate that improvements in outcomes are possible when treatment protocols that incorporate all known beneficial therapies are applied in a timely fashion.

Resuscitating patients with early severe sepsis: a Canadian multicentre observational study

BACKGROUND

Fluid resuscitation is a key factor in restoring hemodynamic stability and tissue perfusion in patients with severe sepsis. We sought to examine associations of the quantity and type of fluid administered in the first six hours after identification of severe sepsis and hospital mortality, intensive care unit (ICU) mortality, and organ failure.

METHODS

A retrospective, multicentre cohort study was undertaken at five Canadian tertiary care ICUs. We identified patients with severe sepsis admitted to the ICU between July 1, 2000, and June 30, 2002, using both administrative and clinical databases. Patients were included if they were hypotensive, had an infectious source, and at least two systemic inflammatory response syndrome criteria. We recorded total quantity and type of fluid administered for the first six hours after severe sepsis was identified. The first episode of hypotension defined the starting point for collection of fluid data. Multivariable regression analyses were performed to examine associations between quantity and type of fluid administered and hospital/ICU mortality, and organ failure.

RESULTS

Of 2,026 potentially eligible patient charts identified, 496 patients met eligibility criteria. The mean age and Acute Physiology and Chronic Health Evaluation score (APACHE II) were 61.8 +/- 16.5 yr and 29.0 +/- 8.0, respectively. No associations between quantity or type of fluid administered and hospital mortality or ICU mortality were identified, and there were no statistically significant associations between quantity or type of fluid administered and organ failure. However, more fluid resuscitation was associated with an increased risk of cardiovascular failure [odds ratio (OR) and 95% confidence interval (CI)] for 2-4 L 1.67 (1.03-2.70) and > 4 L 2.34 (1.23-4.44) and a reduced risk of renal failure [OR, 95% CI for 2-4 L 0.48 (0.28-0.83) and > 4 L 0.45 (0.22-0.92)] in the first 24 hr of severe sepsis. Administration of colloid and crystalloid fluid as compared to crystalloid fluid alone was associated with a lower risk of renal failure [OR, 95% CI 0.45 (0.26 to 0.76)].

CONCLUSION

An association between hospital mortality and quantity or type of fluid administered in the first six hours after the diagnosis of severe sepsis was not identifiable. These findings should be considered as hypothesis-generating and warrant confirmation or refutation by randomized controlled trials.