Preoperative and intraoperative predictors of postoperative acute respiratory distress syndrome in a general surgical population.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is a devastating condition with an estimated mortality exceeding 30%. There are data suggesting risk factors for ARDS development in high-risk populations, but few data are available in lower incidence populations. Using risk-matched analysis and a combination of clinical and research data sets, we determined the incidence and risk factors for the development of ARDS in this general surgical population. METHODS: We conducted a review of common adult surgical procedures completed between June 1, 2004 and May 31, 2009 using an anesthesia information system. This data set was merged with an ARDS registry and an institutional death registry. Preoperative variables were subjected to multivariate analysis. Matching and multivariate regression was used to determine intraoperative factors associated with ARDS development. RESULTS: In total, 50,367 separate patient admissions were identified, and 93 (0.2%) of these patients developed ARDS. Preoperative risk factors for ARDS development included American Society of Anesthesiologist status 3-5 (odds ratio [OR] 18.96), emergent surgery (OR 9.34), renal failure (OR 2.19), chronic obstructive pulmonary disease (OR 2.16), number of anesthetics during the admission (OR 1.37), and male sex (OR 1.65). After matching, intraoperative risk factors included drive pressure (OR 1.17), fraction inspired oxygen (OR 1.02), crystalloid administration in liters (1.43), and erythrocyte transfusion (OR 5.36). CONCLUSIONS: ARDS is a rare condition postoperatively in the general surgical population and is exceptionally uncommon in low American Society of Anesthesiologists status patients undergoing scheduled surgery. Analysis after matching suggests that ARDS development is associated with median drive pressure, fraction inspired oxygen, crystalloid volume, and transfusion.

A randomized trial of recombinant human granulocyte-macrophage colony stimulating factor for patients with acute lung injury.

RATIONALE: Despite recent advances in critical care and ventilator management, acute lung injury and acute respiratory distress syndrome continue to cause significant morbidity and mortality. Granulocyte-macrophage colony stimulating factor may be beneficial for patients with acute respiratory distress syndrome. OBJECTIVES: To determine whether intravenous infusion of granulocyte-macrophage colony stimulating factor would improve clinical outcomes for patients with acute lung injury/acute respiratory distress syndrome. DESIGN: A randomized, double-blind, placebo-controlled clinical trial of human recombinant granulocyte-macrophage colony stimulating factor vs. placebo. The primary outcome was days alive and breathing without mechanical ventilatory support within the first 28 days after randomization. Secondary outcomes included mortality and organ failure-free days. SETTING: Medical and surgical intensive care units at three academic medical centers. PATIENTS: One hundred thirty individuals with acute lung injury of at least 3 days duration were enrolled, out of a planned cohort of 200 subjects. INTERVENTIONS: Patients were randomized to receive human recombinant granulocyte-macrophage colony stimulating factor (64 subjects, 250 µg/M) or placebo (66 subjects) by intravenous infusion daily for 14 days. Patients received mechanical ventilation using a lung-protective protocol. MEASUREMENTS AND MAIN RESULTS: There was no difference in ventilator-free days between groups (10.7 ± 10.3 days placebo vs. 10.8 ± 10.5 days granulocyte-macrophage colony stimulating factor, p = .82). Differences in 28-day mortality (23% in placebo vs. 17% in patients receiving granulocyte-macrophage colony stimulating factor (p = .31) and organ failure-free days (12.8 ± 11.3 days placebo vs. 15.7 ± 11.9 days granulocyte-macrophage colony stimulating factor, p = .16) were not statistically significant. There were similar numbers of serious adverse events in each group. CONCLUSIONS: In a randomized phase II trial, granulocyte-macrophage colony stimulating factor treatment did not increase the number of ventilator-free days in patients with acute lung injury/acute respiratory distress syndrome. A larger trial would be required to determine whether treatment with granulocyte-macrophage colony stimulating factor might alter important clinical outcomes, such as mortality or multiorgan failure. (ClinicalTrials.gov number, NCT00201409 [ClinicalTrials.gov]).

A description of intraoperative ventilator management in patients with acute lung injury and the use of lung protective ventilation strategies.

BACKGROUND: The incidence of acute lung injury (ALI) in hypoxic patients undergoing surgery is currently unknown. Previous studies have identified lung protective ventilation strategies that are beneficial in the treatment of ALI. The authors sought to determine the incidence and examine the use of lung protective ventilation strategies in patients receiving anesthetics with a known history of ALI. METHODS: The ventilation parameters that were used in all patients were reviewed, with an average preoperative PaO2/Fio2 [corrected] ratio of ≤ 300 between January 1, 2005 and July 1, 2009. This dataset was then merged with a dataset of patients screened for ALI. The median tidal volume, positive end-expiratory pressure, peak inspiratory pressures, fraction inhaled oxygen, oxygen saturation, and tidal volumes were compared between groups. RESULTS: A total of 1,286 patients met criteria for inclusion; 242 had a diagnosis of ALI preoperatively. Comparison of patients with ALI versus those without ALI found statistically yet clinically insignificant differences between the ventilation strategies between the groups in peak inspiratory pressures and positive end-expiratory pressure but no other category. The tidal volumes in cc/kg predicted body weight were approximately 8.7 in both groups. Peak inspiratory pressures were found to be 27.87 cm H2O on average in the non-ALI group and 29.2 in the ALI group. CONCLUSION: Similar ventilation strategies are used between patients with ALI and those without ALI. These findings suggest that anesthesiologists are not using lung protective ventilation strategies when ventilating patients with low PaO2/Fio2 [corrected] ratios and ALI, and instead are treating hypoxia and ALI with higher concentrations of oxygen and peak pressures.

A bibliometric search of citation classics in anesthesiology.

BACKGROUND: Articles cited counts are catalogued and help identify landmark papers. This study provides a citation classics of anesthesiology literature using the framework of subspecialties to provide a review of well-developed areas of research in anesthesiology. METHODS: A comprehensive list of the most-cited articles in anesthesia was compiled using a bibliometric database and general search terms such as "anesthesia" as well as subspecialty-specific search terms. Queries were reviewed for relevance to anesthesiology practice, categorized by subspecialty, and ranked according to their citation counts. RESULTS: The database resulted in 2519 articles published between 1945 and 2008. The specialty areas most represented were chronic pain medicine (11%), pharmacology (9%), and pain sciences (9%). CONCLUSIONS: This citations classic allows for advances in anesthesiology and its subspecialties to be highlighted as well to provide useful manuscripts to guide patient care, direct future research, and serve as sources for future academic pursuit.

A description of intraoperative ventilator management and ventilation strategies in hypoxic patients.

BACKGROUND: Hypoxia is a common finding in the anesthetized patient. Although there are a variety of methods to address hypoxia, it is not well documented what strategies are used by anesthesiologists when faced with a hypoxic patient. Studies have identified that lung protective ventilation strategies have beneficial effects in both oxygenation and mortality in acute respiratory distress syndrome. We sought to describe the ventilation strategies in anesthetized patients with varying degrees of hypoxemia as defined by the Pao(2) to fraction of inspired oxygen (Fio(2)) (P/F) ratio. METHODS: We conducted a review of all operations performed between January 1, 2005, and July 31, 2009, using a general anesthetic, excluding cardiac and thoracic procedures, to assess the ventilation settings that were used in patients with different P/F ratios. Patients older than 18 years who received a general anesthetic were included. Four cohorts of arterial blood gases (ABGs) were identified with P/F >300, 300 > or = P/F > 200, 200 > or = P/F > 100, 100 > or = P/F. Using the standard predicted body weight (PBW) equation, we calculated the milliliters per kilogram (mL/kg PBW) with which the patient's lungs were being ventilated. Positive end-expiratory pressure (PEEP), peak inspiratory pressures (PIPs), Fio(2), oxygen saturation (Sao(2)), and tidal volume in mL/kg PBW were compared. RESULTS: A total of 28,706 ABGs from 11,445 operative cases met criteria for inclusion. There were 19,679 ABGs from the P/F >300 group, 5364 ABGs from the 300 > or = P/F > 200 group, 3101 ABGs from the 200 > or = P/F > 100 group, and 562 ABGs from the 100 > or = P/F group identified. A comparison of ventilation strategies found statistical significance but clinically irrelevant differences. Tidal volumes ranged between 8.64 and 9.16 and the average PEEP varied from 2.5 to 5.5 cm H(2)O. There were substantial differences in the average Fio(2) and PIP among the groups, 59% to 91% and 22 to 29 cm H(2)O, respectively. CONCLUSION: Similar ventilation strategies in mL/kg PBW and PEEP were used among patients regardless of P/F ratio. The results of this study suggest that anesthesiologists, in general, are treating hypoxemia with higher Fio(2) and PIP. The average Fio(2) and PIP were significantly escalated depending on the P/F ratio.

Development and validation of an acute kidney injury risk index for patients undergoing general surgery: results from a national data set.

BACKGROUND: The authors sought to identify the incidence, risk factors, and mortality impact of acute kidney injury (AKI) after general surgery using a large and representative national clinical data set. METHODS: The 2005-2006 American College of Surgeons-National Surgical Quality Improvement Program participant use data file is a compilation of outcome data from general surgery procedures performed in 121 US medical centers. The primary outcome was AKI within 30 days, defined as an increase in serum creatinine of at least 2 mg/dl or acute renal failure necessitating dialysis. A variety of patient comorbidities and operative characteristics were evaluated as possible predictors of AKI. A logistic regression full model fit was used to create an AKI model and risk index. Thirty-day mortality among patients with and without AKI was compared. RESULTS: Of 152,244 operations reviewed, 75,952 met the inclusion criteria, and 762 (1.0%) were complicated by AKI. The authors identified 11 independent preoperative predictors: age 56 yr or older, male sex, emergency surgery, intraperitoneal surgery, diabetes mellitus necessitating oral therapy, diabetes mellitus necessitating insulin therapy, active congestive heart failure, ascites, hypertension, mild preoperative renal insufficiency, and moderate preoperative renal insufficiency. The c statistic for a simplified risk index was 0.80 in the derivation and validation cohorts. Class V patients (six or more risk factors) had a 9% incidence of AKI. Overall, patients experiencing AKI had an eightfold increase in 30-day mortality. CONCLUSIONS: Approximately 1% of general surgery cases are complicated by AKI. The authors have developed a robust risk index based on easily identified preoperative comorbidities and patient characteristics.

Preoperative and intraoperative predictors of cardiac adverse events after general, vascular, and urological surgery.

BACKGROUND: The authors sought to determine the incidence and risk factors for perioperative cardiac adverse events (CAEs) after noncardiac surgery using detailed preoperative and intraoperative hemodynamic data. METHODS: The authors conducted a prospective observational study at a single university hospital from 2002 to 2006. All American College of Surgeons-National Surgical Quality Improvement Program patients undergoing general, vascular, and urological surgery were included. The CAE outcome definition included cardiac arrest, non-ST elevation myocardial infarction, Q-wave myocardial infarction, and new clinically significant cardiac dysrhythmia within the first 30 postoperative days. RESULTS: Four years of data demonstrated that of 7,740 noncardiac operations, 83 patients (1.1%) experienced a CAE within 30 days. Nine independent predictors were identified (P < or = 0.05): age > or = 68, body mass index > or = 30, emergent surgery, previous coronary intervention or cardiac surgery, active congestive heart failure, cerebrovascular disease, hypertension, operative duration > or = 3.8 h, and the administration of 1 or more units of packed red blood cells intraoperatively. The c-statistic of this model was 0.81 +/- 0.02. Univariate analysis demonstrated that high-risk patients experiencing a CAE were more likely to experience an episode of mean arterial pressure < 50 mmHg (6% vs. 24%, P = 0.02), experience an episode of 40% decrease in mean arterial pressure (26% vs. 53%, P = 0.01), and an episode of heart rate > 100 (22% vs. 34%, P = 0.05). CONCLUSIONS: In comparison with current risk stratification indices, the inclusion of intraoperative elements improves the ability to predict a perioperative CAE after noncardiac surgery.

Improvement in the quality of randomized controlled trials among general anesthesiology journals 2000 to 2006: a 6-year follow-up.

BACKGROUND: We previously assessed all randomized controlled trials (RCTs) from four anesthesiology journals from January 2000 to December 2000. We identified key areas for improvement in the study protocol design and implementation and in data analyses. This study was repeated for the year 2006 to determine if improvements have occurred during the 6-yr interval. METHODS: All RCTs published in 2006 in four anesthesiology journals (Anesthesiology, Anesthesia & Analgesia, Anaesthesia, and Canadian Journal of Anesthesia) were retrieved using a MEDLINE search. Of 2164 articles published in 2006, 200 papers met these search criteria and were considered valid for analysis. We completed a 14-item, validated assessment tool used in our previous study to determine a quality score for each article. Four clinical reviewers each assessed 50 articles, and one reviewer assessed all 200 articles. Points were assigned by consensus. Scores were weighted and compared with the results from the year 2000. RESULTS: Quality scores improved from the year 2000 to 2006, from a mean overall quality score of 44% (95% CI = 42, 46) to a mean score of 58% (95% CI = 55, 60). Specific areas of study, quality assessment demonstrating improvement, included sample size estimates (52% vs 86%, P < 0.0001), major end-points (44% vs 99%, P < 0.0001), and discussion of side effects (68% vs 82%, P = 0.0019). Low quality scores remained for randomization blinding (4% vs 19% P < 0.0001), observer blinding to continuing studies (1% vs 5% P = 0.116), and post-beta estimates in trials with negative outcomes (16% vs 18%, P < 0.87). CONCLUSIONS: There appears to have been a general improvement in the overall quality of RCT reporting among the major anesthesiology journals from the year 2000 to 2006. However, many articles could be improved with respect to randomization blinding, observer blinding to continuing study results (i.e., no unplanned interim data analysis), and a full discussion of Type II error in negative trials. Responsibility to improve the quality of the anesthesiology literature rests with investigators to design, implement and report high quality RCTs, and with peer reviewers and journal editors to set the standard for manuscript reporting. Periodic reassessments of the literature can serve to improve and maintain the quality of clinical trials reporting.

Specificity improvement for network distributed physiologic alarms based on a simple deterministic reactive intelligent agent in the critical care environment.

Automated physiologic alarms are available in most commercial physiologic monitors. However, due to the variability of data coming from the physiologic sensors describing the state of patients, false positive alarms frequently occur. Each alarm requires review and documentation, which consumes clinicians' time, may reduce patient safety through 'alert fatigue' and makes automated physician paging infeasible. To address these issues a computerized architecture based on simple reactive intelligent agent technology has been developed and implemented in a live critical care unit to facilitate the investigation of deterministic algorithms for the improvement of the sensitivity and specificity of physiologic alarms. The initial proposed algorithm uses a combination of median filters and production rules to make decisions about what alarms to generate. The alarms are used to classify the state of patients and alerts can be easily viewed and distributed using standard network, SQL database and Internet technologies. To evaluate the proposed algorithm, a 28 day study was conducted in the University of Michigan Medical Center's 14 bed Cardiothoracic Intensive Care Unit. Alarms generated by patient monitors, the intelligent agent and alerts documented on patient flow sheets were compared. Significant improvements in the specificity of the physiologic alarms based on systolic and mean blood pressure was found on average to be 99% and 88% respectively. Even through significant improvements were noted based on this algorithm much work still needs to be done to ensure the sensitivity of alarms and methods to handle spurious sensor data due to patient or sensor movement and other influences.

How Do Healthcare Professionals Personalize Their Software? A Pilot Exploration Based on an Electronic Health Records Search Engine.

To improve user experience, many health IT systems provide personalization options allowing end users to tailor the software to their needs and preferences. However, few studies have investigated if healthcare professionals actually make full use of this feature. As an initial step towards understanding end users' software personalization behavior in healthcare, we conducted a pilot study to examine how clinicians, staff, and researchers customized a search engine designed to facilitate information retrieval from electronic health records. The results show that a majority of the end users (82.4%) did not make an effort to modify the system's default settings. Among those who did, they more often changed its 'look-and-feel' than its functionality offerings. We conclude that future research is warranted to study the rationale underlying healthcare professionals' software personalization decisions both to optimize user experience and to avoid building complex and costly personalization options that are unused or underutilized.

Do outcomes vary according to the source of admission to the pediatric intensive care unit?

OBJECTIVE: To examine associations between mortality, length of stay, and the sources of admission to tertiary pediatric intensive care. DESIGN: A retrospective analysis of prospectively collected data. SETTING: A tertiary medical center with a 16-bed medical-surgical intensive care unit and a 15-bed cardiac pediatric intensive care unit (PICU). PATIENTS: All admissions from July 1, 1998, through June 30, 2004. Multivariable regression methods compared length of stay and mortality between the sources of PICU admission, controlling for multiple variables, including severity of illness. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 8,897 eligible admissions, 74% were directly from the study hospital's emergency department or operating rooms, while 26% were from indirect sources, including the study hospital's wards (11%) or interhospital transfer from either non-PICU (12%) or PICU settings (3%). Compared with emergency department admissions, ward admissions had higher odds of mortality (odds ratio 1.65, 95% confidence interval 1.08-2.51), transfer admissions from non-PICU settings did not have elevated odds of mortality (odds ratio 0.80, 95% confidence interval 0.51-1.25), and inter-PICU transfer admissions had higher odds of mortality (odds ratio 1.43, 95% confidence interval 0.80-2.56), although not reaching statistical significance. Compared with emergency department admissions, ward admissions stayed almost 4 days longer in the PICU, while interhospital transfer admissions from non-PICU and PICU settings stayed 2 and 6 days longer, respectively. CONCLUSIONS: Outcomes of tertiary pediatric intensive care vary significantly by source of admission. Strategies aimed at reduction of mortality at the tertiary PICU should target transfer admissions from the hospital's wards and from PICUs of other hospitals.

Predictors of postoperative acute renal failure after noncardiac surgery in patients with previously normal renal function.

BACKGROUND: The authors investigated the incidence and risk factors for postoperative acute renal failure after major noncardiac surgery among patients with previously normal renal function. METHODS: Adult patients undergoing major noncardiac surgery with a preoperative calculated creatinine clearance of 80 ml/min or greater were included in a prospective, observational study at a single tertiary care university hospital. Patients were followed for the development of acute renal failure (defined as a calculated creatinine clearance of 50 ml/min or less) within the first 7 postoperative days. Patient preoperative characteristics and intraoperative anesthetic management were evaluated for associations with acute renal failure. Thirty-day, 60-day, and 1-yr all-cause mortality was also evaluated. RESULTS: A total of 65,043 cases between 2003 and 2006 were reviewed. Of these, 15,102 patients met the inclusion criteria; 121 patients developed acute renal failure (0.8%), and 14 required renal replacement therapy (0.1%). Seven independent preoperative predictors were identified (P < 0.05): age, emergent surgery, liver disease, body mass index, high-risk surgery, peripheral vascular occlusive disease, and chronic obstructive pulmonary disease necessitating chronic bronchodilator therapy. Several intraoperative management variables were independent predictors of acute renal failure: total vasopressor dose administered, use of a vasopressor infusion, and diuretic administration. Acute renal failure was associated with increased 30-day, 60-day, and 1-yr all-cause mortality. CONCLUSIONS: Several preoperative predictors previously reported to be associated with acute renal failure after cardiac surgery were also found to be associated with acute renal failure after noncardiac surgery. The use of vasopressor and diuretics is also associated with acute renal failure.

Understanding Patient Questions about their Medical Records in an Online Health Forum: Opportunity for Patient Portal Design.

There are many benefits of online patient access to their medical records through technologies such as patient portals. However, patients often have difficulties understanding the clinical data presented in portals. In response, increasingly, patients go online to make sense of this data. One commonly used online resource is health forums. In this pilot study, we focus on one type of clinical data, laboratory results, and one popular forum, MedHelp. We examined patient question posts that contain laboratory results to gain insights into the nature of these questions and of the answers. Our analyses revealed a typology of confusion (i.e., topics of their questions) and potential gaps in traditional healthcare supports (i.e., patients' requests and situational factors), as well as the supports patients may gain through the forum (i.e., what the community provides). These results offer preliminary evidence of opportunities to redesign patient portals, and will inform our future work.

Accepting critically ill transfer patients: adverse effect on a referral center's outcome and benchmark measures.

BACKGROUND: Common methods of benchmarking clinical performance rarely, if ever, account for admission source and, in particular, the effect of a patient being transferred from one medical center to another. Small biases in comparisons of observed versus expected deaths can substantially affect how high-quality institutions compare with peer hospitals. With the most sophisticated and validated set of case-mix measures available for patients, the intensive care unit is an ideal setting in which to study the effect of a patient's being transferred from another hospital. OBJECTIVE: To determine the extent of bias in benchmarking outcomes when performance measures do not account for transfer patients' greater severity of illness. DESIGN: Prospectively developed cohort study. SETTING: Medical intensive care unit (MICU) at a tertiary care university hospital. PATIENTS: 4579 consecutive admissions for 4208 patients from 1 January 1994 to 1 April 1998. MEASUREMENTS: MICU and hospital lengths of stay, MICU readmission, and hospital mortality rates. RESULTS: Compared with directly admitted patients, MICU patients transferred from another hospital had significantly higher Acute Physiology Scores at the time of admission and discharge (P = 0.001). Even after full adjustment for case mix and severity of illness, transfer patients had a 38% longer MICU stay (95% CI, 32% to 45%), a 41% longer hospital stay (CI, 34% to 50%), and a 2.2 times greater odds of hospital mortality (CI, 1.7 to 2.8) than directly admitted patients. With identical efficiency and quality, a referral hospital with a 25% MICU transfer rate compared with another with a 0% transfer rate would be penalized by 14 excess deaths per 1000 admissions when a benchmarking program adjusts only for case mix and severity of illness and not for the source of admission. CONCLUSIONS: In a setting with the most thorough diagnostic-based, case-mix adjustment and the most physiologically precise severity-of-illness information, accepting transfer patients can adversely affect efficiency and quality benchmarks. Benchmarking and profiling efforts beyond intensive care units must also recognize and account for this phenomenon; otherwise, referral centers may have an incentive to refuse care for patients who could benefit from being transferred to their facility.

Neoadjuvant chemotherapy and radiotherapy for large extremity soft-tissue sarcomas.

PURPOSE: Treatment of extremity soft-tissue sarcomas yields excellent local control, but distant failure is common with large, high-grade tumors. A regimen of preoperative chemotherapy consisting of mesna, adriamycin, ifosfamide, and dacarbazine (MAID) interdigitated with radiotherapy followed by resection and postoperative chemotherapy with or without radiotherapy was designed to improve treatment outcome. We report the mature outcome data on 48 treated patients and compare them with the data of an historical matched control patient population. METHODS AND MATERIALS: Adult patients with high-grade extremity soft-tissue sarcomas >or=8 cm were treated with three cycles of preoperative chemotherapy combined with 44 Gy of radiotherapy followed by surgery. Three cycles of postoperative MAID were planned. For patients with positive surgical margins, 16 Gy was delivered postoperatively. RESULTS: All 48 patients (M0) received the MAID protocol treatment, and their outcome was superior to that of the historical control patients. The 5-year actuarial local control, freedom from distant metastasis, disease-free survival, and overall survival rate was 92% and 86% (p = 0.1155), 75% and 44% (p = 0.0016), 70% and 42% (p = 0.0002), and 87% and 58% (p = 0.0003) for the MAID and control patient groups, respectively. Acute hematologic toxicity in the MAID group included febrile neutropenia in 12 patients (25%). Wound healing complications occurred in 14 (29%) of 48 MAID patients. One MAID patient developed late fatal myelodysplasia. CONCLUSION: After aggressive chemoradiation and surgery, these patients showed a significant reduction in distant metastases, with a highly significant gain in disease-free and overall survival compared with a historical control group. On the basis of this experience, the Radiation Therapy Oncology Group conducted a multi-institutional trial.

Fluid management in patients with acute respiratory distress syndrome.

In a recent review of the data for fluid strategies and ARDS, fluid restriction or diuretic use was graded as "reasonably justifiable by available scientific evidence" and as "strongly supported by expert critical care opinion". Until the ARDS Network trial is published, only general guidelines regarding fluid management with or without specific vascular filling pressures from a pulmonary artery catheter can be made. Ultimately, the rationale for restricting fluid is to reduce hydrostatic pressures as much as possible. It seems most reasonable to maintain the lowest PAOP in ARDS patients that still maintains adequate circulating blood volume, mean arterial perfusion pressures, and cardiac output to provide sufficient oxygen delivery. Other clinical variables such as central venous pressure, urinary output, acid-base status, and lactate, serum urea nitrogen, and serum creatinine levels may help in judging the adequacy of a patient's intravascular volume, especially if central vascular pressure measurements are not available. Measures to reduce total body water, including flood restriction and diuretic use, seem to be of some benefit. Vasopressor use is especially important when systemic perfusion pressures are inadequate to maintain organ blood flow but should not be used to create supranormal levels of oxygen delivery.

An overview of end-of-life issues in the intensive care unit.

The population of the earth is aging, and as medical techniques, pharmaceuticals, and devices push the boundaries of human physiological capabilities, more humans will go on to live longer. However, this prolonged existence may involve incapacities, particularly at the end-of-life, and especially in the intensive care unit. This arena involves not only patients and families, but also care givers. It involves topics from economics to existentialism, and surgery to spiritualism. It requires education, communication, acceptance of diversity, and an ultimate acquiescence to the inevitable. Here, we present a comprehensive overview of issues in the care of patients at the end-of-life stage that may cause physicians and other healthcare providers, medical, ethical, social, and philosophical concerns in the intensive care unit.

The most influential articles in critical care medicine.

PURPOSE: The study aimed to examine query strategies that would provide an exhaustive search method to retrieve the most referenced articles within specific categories of critical care. MATERIAL AND METHODS: A comprehensive list of the most cited critical care medicine articles was generated by searching the Science Citation Index Expanded data set using general critical care terms keywords such as "critical care," critical care journal titles, and keywords for subsubjects of critical care. RESULTS: The final database included 1187 articles published between 1905 and 2006. The most cited article was referenced 4909 times. The most productive search term was intensive care. However, this term only retrieved 25% of the top 100 articles. Furthermore, 662 of the top 1000 articles could not be found using any of the basic critical care search terms. Sepsis, acute lung injury, and mechanical ventilation were the most common areas of focus for the articles retrieved. CONCLUSION: Retrieving frequently cited, influential articles in critical care requires using multiple search terms and manuscript sources. Periodic compilations of most cited articles may be useful for critical care practitioners and researches to keep abreast of important information.

Pulse oximetry saturation to fraction inspired oxygen ratio as a measure of hypoxia under general anesthesia and the influence of positive end-expiratory pressure.

PURPOSE: In ICU patients with acute lung injury, the pulse oximetry saturation (Spo(2)) to fraction of inspired oxygen (Fio(2)) (S/F) ratio is a reliable surrogate measure for the P/F (Pao(2)/Fio(2)) ratio. Our goal was to determine the correlation of the S/F to the P/F in a large sample of patients undergoing general anesthesia and the influence of positive end-expiratory pressure (PEEP) on this measure. METHODS: We studied adult general anesthetics performed with arterial blood gas analysis. Intraoperative data were collected from an anesthesia information system. The S/F ratios corresponding to P/F ratios of 300 were determined. RESULTS: A total of 4439 values were collected. Linear correlation between S/F and P/F was identified (r = 0.46; P < .01) with a P/F of 300 corresponding to an S/F of 206. The correlation was stronger in patients with 5 to 9 cm PEEP (r = 0.52; P < .01), more than 9 cm H(2)O PEEP (r = 0.68; P < .01), and a P/F ratio of 300 or less (r = 0.61; P < .01). CONCLUSION: The S/F correlates with the P/F in our cohort of patients undergoing general anesthesia, especially those ventilated with PEEP more than 9 cm H(2)O and/or with P/F less than 300. It has use as a noninvasive measure to screen for increased pulmonary dysfunction and to trend oxygenation during a general anesthetic.

Review of a large clinical series: association of cumulative fluid balance on outcome in acute lung injury: a retrospective review of the ARDSnet tidal volume study cohort.

OBJECTIVE: To evaluate the independent influence of fluid balance on outcomes for patients with acute lung injury. DESIGN: Secondary analysis of a prospective cohort study conducted between March 1996 and March 1999. SETTING: The study involved 10 academic clinical centers (with 24 hospitals and 75 Intensive Care Units). PATIENTS: All patients for whom fluid balance data existed (844) from the 902 patients enrolled in the National Heart Lung Blood Institute's ARDS Network ventilator-tidal volume trial. INTERVENTIONS: The study had no interventions. MEASUREMENTS/RESULTS: On the first day of study enrollment, 683 patients were, on average, more than 3.5 L in positive fluid balance compared to 161 patients in negative fluid balance (P < .001). Cumulative negative fluid balance on day 4 of the study was associated with an independently lower hospital mortality (OR, 0.50; 95% CI, 0.28-0.89; P < .001) more ventilator and intensive care unit-free days. CONCLUSIONS: Negative cumulative fluid balance at day 4 of acute lung injury is associated with significantly lower mortality, independent of other measures of severity of illness.