Is there a preferred technique for weaning the difficult-to-wean patient? A systematic review of the literature.

OBJECTIVE: To answer the following question: In difficult-to-wean patients, which of the three commonly used techniques of weaning (T-piece, synchronized intermittent mandatory ventilation, or pressure support ventilation) leads to the highest proportion of successfully weaned patients and the shortest weaning time? DATA SOURCES: Computerized literature searches in MEDLINE (1975-1996), Cinahl (1982-1996), and Healthplan (1985-1996), exploding all Mesh headings pertaining to Mechanical Ventilation and Weaning. Searches were restricted to the English language, adults, and humans. Personal files were hand searched, and references of selected articles were reviewed. STUDY SELECTION: a) POPULATION: Patients requiring a gradual weaning process from the ventilator (either requiring prolonged initial ventilation of >72 hrs or a failed trial of spontaneous breathing after >24 hrs of ventilation); b) INTERVENTIONS: At least two of the following three modes of weaning from mechanical ventilation must have been compared: T-piece, synchronized intermittent mandatory ventilation, or pressure support ventilation; c) OUTCOMES: At least one of the following: weaning time (time from initiation of weaning to extubation) or successful weaning rate (successfully off the ventilator for >48 hrs); and d) STUDY DESIGN: Controlled trial. DATA EXTRACTION: Two reviewers independently reviewed the articles and graded them according to their methodologic rigor. Data on the success of weaning and the time to wean were summarized for each study. DATA SYNTHESIS: The search strategy identified 667 potentially relevant studies; of these, 228 had weaning as their primary focus, and of these, 48 addressed modes of ventilation during weaning. Only 16 of these 48 studies had one of the specified outcomes, and only ten of these were controlled trials. Of the ten trials, only four fulfilled all our selection criteria. The results of the trials were conflicting, and there was heterogeneity among studies that precluded meaningful pooling of the results. CONCLUSIONS: There are few trials designed to determine the most effective mode of ventilation for weaning, and more work is required in this area. From the trials reviewed, we could not identify a superior weaning technique among the three most popular modes, T-piece, pressure support ventilation, or synchronized intermittent mandatory ventilation. However, it appears that synchronized intermittent mandatory ventilation may lead to a longer duration of the weaning process than either T-piece or pressure support ventilation. Finally, the manner in which the mode of weaning is applied may have a greater effect on the likelihood of weaning than the mode itself.

Pressure ulcer prevention: a randomized controlled trial of 2 risk-directed strategies for patient surface assignment.

OBJECTIVE: To compare the clinical utility, in terms of incidence of pressure ulcer (PU) development, and economic impact of 2 programs of patient surface assignment for PU prevention. DESIGN: Randomized controlled clinical trial with economic evaluation. SETTING: 30-bed multidisciplinary intensive care unit (ICU), serving as the regional trauma center. PATIENTS: 144 consecutive eligible patients at risk for the development of PUs. INTERVENTION: PU risk was assessed on admission using the Skin Ulcer Risk Evaluation (SURE) Score, and patients were randomized to either the experimental (purchase) or control group (purchase/rent). Based on their SURE Score, patients were assigned a specialty surface if needed. Patients received head-to-toe skin assessments twice weekly, new PUs were documented, a new SURE Score was calculated, and specialty surfaces were upgraded or downgraded as necessary. OUTCOMES: The incidence of PUs by site and severity, and cost. ANALYSES: Multivariate logistic regression and decision modeling. RESULTS: No significant differences were detected between groups with respect to baseline population characteristics, nor in the development of PUs. Predictors of PU development were ICU length of stay and SURE Score. The experimental (purchase) group was the less costly strategy. Under baseline assumptions, surface costs per at-risk patient were $76 CDN and $171 CDN in the experimental and control groups, respectively. The savings of $95 CDN per at-risk patient translates into conservative annual savings of $47,500 CDN. CONCLUSIONS: Using an objective, risk-based method of patient surface assignment, the authors compared the clinical and economic outcomes of 2 programs of PU prevention. In a direct comparison of alternatives, the strategy that emphasized purchased rather than rented products proved to be the more economical. Finally, this approach illustrates how by prospectively capturing data on both the costs and consequences of competing alternatives, a more objective and informed decision-making process can result.

Ventilatory care in a selection of Ontario hospitals: bigger is not necessarily better! Critical Care Research Network (CCR-Net).

OBJECTIVE: To determine whether there is variability in the structure and process of ventilatory care in intensive care units (ICUs) of the hospitals of Southwestern Ontario. DESIGN: Self-administered questionnaire-based survey. SETTING: ICUs of selected community and teaching hospitals of Southwestern Ontario. PARTICIPANTS: Head of respiratory therapy service of respective hospitals; in those hospitals without respiratory therapists, the ICU nurse manager. INTERVENTION: Self-administered questionnaire. OUTCOME MEASURE(S): The availability of different models of ventilators and respiratory therapist and physician coverage were assessed. In addition, the use of clinical practice guidelines, respiratory therapists, and the nursing role in ventilatory care were determined. RESULTS: In general, the structure of ventilatory care, including availability of different modes of ventilation, and coverage by respiratory therapists and physicians was more comprehensive in larger hospitals. However, the availability of some modes of ventilation varied more than expected among hospitals of comparable size. Similarly, variability in the process of ventilatory care, defined by the availability of clinical practice guidelines and the roles of respiratory therapists varied both within and among hospitals of different size. CONCLUSIONS: The structure and process of ventilatory care in this sample of Southwestern Ontario ICUs was found to be variable. Not all this variability could be accounted for by hospital size, suggesting a potential for improvement in overall ventilatory care. Further study is required before any specific recommendations can be considered.

Withdrawal and withholding of life support in the intensive care unit: a comparison of teaching and community hospitals. The Southwestern Ontario Critical Care Research Network.

OBJECTIVES: To compare the incidence of withdrawal or withholding of life support (WD/WHLS), and to identify similarities and differences in the process of the withdrawal of life support (WDLS) between teaching and community hospitals' intensive care units (ICUs). DESIGN: Prospective cohort study, with some data obtained by retrospective chart review. SETTING: The ICUs of three teaching hospitals and six community hospitals. PATIENTS: All patients who died in these nine ICUs over a 6-mo period. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data on admitting diagnosis, cause of death, mode of death (death despite active treatment, withdrawal or withholding of life support), those initiating and involved in WDLS, and modalities of life support withdrawn were gathered for patients dying in the ICU over a 6-mo period. One hundred sixty patients in community hospitals and 292 in teaching hospitals died in their respective ICUs over the 6-mo period. We found a difference in the distribution of mode of death between community hospitals and teaching hospitals, resulting from a greater proportion of patients dying as a result of withholding life support in community hospitals (11.9% vs. 3.8% withheld, respectively, p = .004). Among the six community hospitals and three teaching hospitals, we found a difference in the proportion of patients dying despite active treatment compared with those dying as a result of WD/WHLS (p = .042 and p = .044, respectively). Initiation of WDLS by physicians was more frequent at teaching hospitals (81% vs. 61%, p = .0005), while families more commonly initiated WDLS at community hospitals (34% vs. 19%, p = .005). A greater proportion of patients in teaching hospitals were receiving mechanical ventilation (99% vs. 89%) and vasopressors (76% vs. 65%) before WDLS. Similar proportions had mechanical ventilation withdrawn (68% and 74%, community hospitals and teaching hospitals, respectively), while there was a trend for fewer patients in community hospitals to have vasopressors withdrawn (56% vs. 70%, p = .082). The time to death after WDLS had begun was longer in community hospitals compared with teaching hospitals (0.74 +/- 1.38 days vs. 0.27 +/- 0.79 [SD] days, p = .0028). CONCLUSIONS: The incidence of WD/WHLS was similar in community hospitals and teaching hospitals; however, withholding of life support was more common in community hospitals. The process of WDLS appears to differ between community hospitals and teaching hospitals.

A systematic review of the cost-effectiveness of noncardiac transitional care units.

OBJECTIVE: To critically appraise and summarize the studies examining the cost-effectiveness of noncardiac transitional care units (TCUs). DATA SOURCES: We conducted a computerized literature search using MEDLINE, and Current Contents from January 1, 1986 to December 31, 1995 and HealthSTAR from January 1, 1989 to December 31, 1995 with the key words intermediate care unit, respiratory care unit, and step-down unit. Bibliographies of all selected articles and review articles were examined. Personal files were also reviewed. STUDY SELECTION: (1) POPULATION: patients in a noncardiac TCU of an acute-care institution; (2) intervention: addition of a noncardiac TCU to the institution; and (3) outcomes: patient outcome-survival and associated costs. DATA EXTRACTION: The necessary data were abstracted and study validity was evaluated by two independent reviewers using a modification of previously published criteria. DATA SYNTHESIS: The studies were summarized qualitatively; upon inspection, they were too heterogeneous to allow quantitative analysis. While the studies all claimed that their TCUs were cost-effective, the economic evaluation designs were flawed to such an extent that the validity of the conclusions is suspect. CONCLUSIONS: To date, the evidence in the literature is insufficient to determine under which circumstances, if any, TCUs are a cost-effective alternative technology to the traditional institution with only ICU and general ward beds.

A retrospective review of a large cohort of patients undergoing the process of withholding or withdrawal of life support.

OBJECTIVES: To determine the proportion of patients who died as a result of the withdrawal or withholding of life support (WD/WHLS) in the intensive care units (ICUs) of three teaching hospitals and to describe the process involved by determining: a) why the decision was made to withdraw support (WDLS); b) when WDLS took place; and c) how the WDLS process was conducted. DESIGN: Retrospective cohort study. SETTING: Three university-affiliated ICUs. PATIENTS: Four hundred nineteen patients who died in one of three academic, tertiary care ICUs over a 1-yr period. INTERVENTIONS: Retrospective chart review. Data collected included age, gender, admitting diagnoses, comorbid disease, Acute Physiology and Chronic Health Evaluation II score, and mode of death (brain death, death due to withholding of life support, death due to WDLS, or death despite ongoing therapy). For those patients dying due to WDLS, the reason for WDLS, person initiating discussion, timing of WDLS, degree of organ dysfunction, order of withdrawal of life support modalities, and the use of sedatives and analgesics were recorded. MEASUREMENTS AND MAIN RESULTS: Seventy percent of patients died by WD/WHLS and 8.4% were brain dead. Patients undergoing WD/WHLS were older and had a longer length of stay than patients dying from other causes. Poor prognosis was the most common reason given for WDLS, reflected by significant organ dysfunction at the time of WDLS. Future quality of life was a less frequently cited reason. Most patients undergoing WDLS did so early in their ICU stay, although time to WDLS appeared to reflect diagnostic group. Few meetings occurred before WDLS and death occurred soon after initiating WDLS. There was a preference of withdrawing mechanical ventilation last and large amounts of morphine (mean 21 +/- 33 [SD] mg/hr) and benzodiazepines (mean 8.6 +/- 11 mg/hr) were used. Little variability in practice was apparent among the studied ICUs. CONCLUSIONS: Similar to other studies, WD/WHLS was the most common cause of death in academic ICUs and poor patient prognosis was considered the most important factor in deciding on WDLS. However, in contrast to other studies, future quality of life was not as frequently cited a reason for WDLS and larger amounts of morphine were used during WDLS. These discrepancies suggest areas for potential future research.

Assessing the efficiency of the admission process to a critical care unit: does the literature allow the use of benchmarking?

OBJECTIVES: To determine the ability of the current literature to supply appropriate data for benchmarking admission practice to a multidisciplinary critical care unit. DESIGN: Retrospective review of data collected prospectively on a cohort of 614 patients and a systematic review of the literature. SETTING: A 30-bed multidisciplinary critical care unit at a university teaching hospital. PATIENTS: Consecutive admissions to the critical care unit over a 6-month period. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: For each patient, demographic data and admitting diagnosis were recorded on admission. Information necessary to calculate the Acute Physiology and Chronic Health Evaluation II and Therapeutic Intervention Scoring System (TISS) scores were collected daily. TISS variables were categorized as "active" or "non-active" treatment variables. Patients were then identified on a daily basis as receiving or not receiving active treatment. A review of the literature, using MEDLINE and the search term "Therapeutic Intervention Scoring Index" (as a textword), was conducted to identify studies that had similarly divided their patients. Using the method of benchmarking, the proportion of patients admitted who received active treatment during their stay in the critical care units was compared between the index critical care unit and those in the literature. A greater proportion of the patients admitted to our unit received active treatment (97.7%) when compared to other studies in the literature (20-66%). However, a number of potential confounding factors were present, such as the availability of intermediate care units, overnight recovery room ventilation, and critical care bed availability between the index critical care unit and those described in the literature. CONCLUSIONS: The current literature does not provide adequate data on critical care unit admission practices to allow useful application of the method of benchmarking. There is a need for publicly accessible large databases to allow individual critical care units to determine their level of efficiency when compared to similar institutions.

Circulatory sequelae of administering CPAP in hyperdynamic sepsis are time dependent.

Evidence questions the circulation's ability to acutely compensate for abrupt changes in O2 delivery (Qo2). Because both sepsis and continuous positive airway pressure (CPAP) may alter the metabolic regulation of tissue oxygenation, we designed an experiment to determine the interaction, if any, between sepsis and time on circulatory homeostasis after the application of CPAP. Twenty-four sheep were randomized to cecal ligation and perforation (CLP) or sham procedure (Sham) and then rerandomized to receive either CPAP (10 mmHg) or no CPAP (No CPAP; CLP/CPAP, n = 8; CLP/No CPAP, n = 8; Sham/CPAP, n = 4; Sham/No CPAP, n = 4). Forty-eight hours later, CLP animals demonstrated an elevated cardiac index (+63%), systemic Qo2 (+49%), and systemic O2 uptake (+28%). Organ blood flow, measured with radiolabeled microspheres, was augmented to the heart and depressed in organs comprising the splanchnic circulation. Compared with the CLP/No CPAP group and both Sham groups, myocardial Qo2 in the CLP/ CPAP group was significantly elevated when measured both 2 and 8 h after CPAP. These changes were unrelated to differences in mean heart work between the study groups. Simultaneously, QO2 to all of the small gut, large gut, pancreas, and kidney in the CLP/CPAP group was elevated during the 2-h study yet reverted to levels not different from baseline by the 8-h study. These data demonstrate 1) a unique sepsis x time interaction with the use of 10 mmHg of CPAP, particularly in the "nonvital" circulations, and 2) CPAP effects on the septic coronary circulation, which were unexplained by changes in external determinants of myocardial O2 need.

Assessing the safety of pediatric laparoscopic surgery.

We studied deviations from normal physiology in piglets (n = 10; average weight 5.75 kg) during carbon dioxide (CO2) pneumoperitoneum. Cardiopulmonary data were gathered during varying intraabdominal pressures (IAP = 8, 12, 15, 20 mm Hg), each sustained for 10 mins. Each animal was its own preinsufflation and exsufflation control. A rapid, significant rise in arterial CO2 pressure from preinsufflation (46.5 +/- 6.7 mm Hg) to insufflation at 20 mm Hg (72.9 +/- 15 mm Hg; p < 0.05) initiated further cardiac adjustments. Responses included a sustained increase in cardiac index (presufflation = 3.1 +/- 1.4; 20 mm Hg IAP = 3.6 +/- 1.2), increased heart rate (preinsufflation = 121 +/- 21; 20 mm Hg IAP = 150 +/- 28; p < 0.05), and left ventricular stroke work (20 mm IAP = 22.7 +/- 8.9; exsufflation 20 min = 15.3 +/- 9.4 g.m/m2; p < 0.05). There was a significant arterial-end CO2 tidal difference throughout insufflation, as great as 15 mm Hg (p < 0.05), suggesting increasing ventilation dead space. Core temperature decreased significantly from preinsufflation (35.3 +/- 1.3 degrees C) to 20 mm Hg IAP (33.6 +/- 1.5 degrees C, p < 0.05). We suggest the following guidelines based on the above data: (a) preoperative examination screening for cardiopulmonary abnormalities; (b) fluid replacement to normal hydration only; (c) cuffed endotracheal tubes for effective ventilation; (d) careful adjustment of minute ventilation to achieve normocapnia; (e) CO2 warming; (f) maximal insufflation pressure of 12 mm Hg; (g) postoperative care emphasizing respiratory and thermoregulation status.

Attitudes toward trauma care of surgeons practising in Ontario.

OBJECTIVE: To assess the attitudes of practising surgeons in the province of Ontario toward issues in trauma care management. DESIGN: A survey by questionnaire. SETTING: The study was carried out in a university-affiliated hospital. The survey respondents generally practised in a nonteaching setting; 48% were over the age of 50 years; 81% worked in an institution with 24-hour in-house physician coverage for the emergency department. SUBJECTS: All 2294 surgeons registered with the Ontario Medical Association were surveyed by completion and return of a questionnaire; 191 surgeons were registered in Ontario but were not practising in the province and were excluded from the survey. Questionnaires were completed by 575 surgeons, but 49 were no longer in active practice, so 526 responses form the basis of this analysis. RESULTS: The response rate to the questionnaire was 27%. One-third of the respondents wished to treat no trauma patients at all; 47% believed that trauma patients had a negative impact on their surgical practice; only 19% considered that trauma patients had a positive impact. Surgeons had negative attitudes toward trauma because of the night and weekend profile of trauma, its effect on elective surgical practice, the poor rate of reimbursement for time spent in trauma management, and the potential medicolegal liability of trauma cases. CONCLUSIONS: These results suggest that there are few surgeons in Ontario who are truly committed to providing care to the injured patient. Strategies to overcome the perceived negative aspects of trauma care must be addressed because a crisis in the availability of surgeons to provide this care seems inevitable.

Preoperative transdermal scopolamine does not reduce the level of nausea and frequency of vomiting after laparoscopic cholecystectomy.

OBJECTIVE: To determine the efficacy of scopolamine administered transdermally before laparoscopic cholecystectomy as a means of reducing postoperative nausea and vomiting. DESIGN: A randomized, double-blind, placebo-controlled study. SETTING: A tertiary-care, university-affiliated hospital. PATIENTS: A volunteer sample of 125 men and women between 20 and 60 years of age scheduled to undergo elective laparoscopic cholecystectomy. Expectant or nursing mothers were excluded, and 35 patients were excluded from the final analysis because of protocol violations. Forty-three patients received scopolamine and 47 patients received a placebo. INTERVENTION: A skin patch (scopolamine or placebo) was applied behind the right ear on the evening before operation and maintained for at least 24 hours postoperatively. MAIN OUTCOME MEASURES: The postoperative level of nausea assessed by the patient on a visual analogue scale, the frequency of vomiting and the frequency of antiemetic use. RESULTS: There was no significant difference in the level of nausea or in the frequency of emesis or use of antiemetics in the first 24 hours postoperatively between the control and study groups. Furthermore, there was no difference in the overall frequency of side effects. However, visual blurring was experienced by six patients in the study group compared with one in the control group (p = 0.082). CONCLUSION: Scopolamine administered transdermally before laparoscopic cholecystectomy does not reduce the frequency or level of nausea and vomiting postoperatively.

Does implementing pulse oximetry in a critical care unit result in substantial arterial blood gas savings?

OBJECTIVES: To examine the impact of pulse oximetry on the use of arterial blood gas and other laboratory determinations and to examine predictors of the use of arterial blood gas measurements. DESIGN: Before (preoximetry)/after (postoximetry) study. SETTING: Thirty-bed multidisciplinary critical care unit. PATIENTS: Consecutive admissions of 300 patients (150 before and 150 after oximetry). MEASUREMENTS: For each patient examined, the number of arterial blood gas determinations, serum electrolyte levels, complete blood chemistries, arterial lactate levels, and creatinine samples were recorded for the initial 9 days of the stay in the critical care unit. These data were stratified by nursing shift (day vs night) and by the source of the admission (medical vs surgical). Other information collected included demographic variables, the severity of illness, the length of stay in the critical care unit, and various ventilatory parameters. RESULTS: Introducing pulse oximetry was associated with a marginal (10.3 percent; p < 0.025) reduction in the use of arterial blood gas determinations. This decrease was accounted for by changes occurring on the night shift and in the surgical patient. These findings were also observed for serum electrolyte determinations. No significant differences in the use of arterial blood gas measurements were found for medical patients. No significant differences were found in the use of arterial lactate levels, complete blood chemistries, or creatinine determinations. Significant predictors of arterial blood gas determinations included the number of days intubated, the number of ventilator orders, the number of days on an inspired oxygen content (FIO2) greater than 50 percent, and the acute physiology and chronic health evaluation II (APACHE II) score. CONCLUSIONS: The implementation of pulse oximetry in this manner gives an idea how effective the technology will be in reducing the use of arterial blood gas determinations without guidelines for the use of pulse oximetry. As only a marginal decrease was observed in the total population of medical and surgical patients, and only on the night shift, formal and standardized guidelines for the most efficient use of pulse oximetry should be considered. If these were considered, pulse oximetry may indeed make a significant contribution to improving the efficiency of care services.

Clinical utility and cost-effectiveness of an air suspension bed in the prevention of pressure ulcers.

OBJECTIVE: To determine, in critically ill patients at risk, both the clinical utility and cost-effectiveness of using an air suspension bed in the prevention of pressure ulcers. DESIGN: Randomized, parallel group, controlled clinical trial with accompanying cost-effectiveness analysis. SETTING: 30-bed multidisciplinary intensive care unit. PATIENTS: 100 consecutive patients at risk for the development of pressure ulcers randomly assigned to receive treatment on either an air suspension bed or a standard intensive care unit bed. Patients considered at risk were those at least 17 years of age with an Acute Physiology and Chronic Health Evaluation II (APACHE II) score greater than 15 who had an expected intensive care unit stay of at least 3 days. MAIN OUTCOME MEASURES: The development of pressure ulcers by site and severity and the costs associated with each of the two programs. RESULTS: The air suspension bed was associated with fewer patients developing single, multiple, or severe pressure ulcers. In patients at risk, the use of an air suspension bed in the prevention of pressure ulcers was a cost-effective therapy. CONCLUSIONS: Despite intense nursing care, pressure ulcers are more prevalent in the critically ill patient population than in the general hospital population. Air suspension therapy provides a clinically effective means of preventing pressure ulcers in these patients. In patients at risk, air suspension therapy was a cost-effective means of managing pressure ulcers compared with the standard hospital bed.

Modeling mortality in the intensive care unit: comparing the performance of a back-propagation, associative-learning neural network with multivariate logistic regression.

The objective of this study was to compare and contrast two techniques of modeling mortality in a 30 bed multi-disciplinary ICU; neural networks and logistic regression. Fifteen physiological variables were recorded on day 3 for 422 consecutive patients whose duration of stay was over 72 hours. Two separate models were built using each technique. First, logistic and neural network models were constructed on the complete 422 patient dataset and discrimination was compared. Second, the database was randomly divided into a 284 patient developmental dataset and a 138 patient validation dataset. The developmental dataset was used to construct logistic and neural net models and the predictive power of these models was verified on the validation dataset. On the complete dataset, the neural network clearly outperformed the logistic model (sensitivity and specificity of 1 and .997 vs. .525 and .966, area under ROC curve .9993 vs. .9259), while both performed equally well on the validation dataset (area under ROC of .82). The excellent performance of the neural net on the complete dataset reveals that the problem is classifiable. Since our dataset only contained 40 mortality events, it is highly likely that the validation dataset was not representative of the developmental dataset, which led to a decreased predictive performance by both the neural net and the logistic regression models. Theoretically, given an extensive dataset, the neural network should be able to perform mortality prediction with a sensitivity and a specificity approaching 95%. Clinically, this would be an extremely important achievement.(ABSTRACT TRUNCATED AT 250 WORDS)

Problems in assessing the technology of critical care medicine.

Technology assessment is becoming increasingly important in the area of critical care due both to the explosion of technology associated with this discipline and to the realization that future demand for these health care resources will undoubtedly exceed the ability to pay. Technology assessment remains both confusing and controversial to many physicians. This review tries to address some of the confusion by reviewing the basic strategies involved in this process. From there, problems and prospects for the evaluation of critical care as a program are presented, followed by the assessment of components within the area of critical care. Finally, recommendations are made on how technology assessment could proceed in the future to best achieve the efficient provision of this service.