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Biomedical subjects

R L Wears

Publications and source records attributed to R L Wears.

At least 19 recordsLinked to original sources
PubMed1992

Length-based endotracheal tube and emergency equipment in pediatrics.

HYPOTHESIS: Pediatric endotracheal (ET) tubes can be accurately selected based on body length using a specialized emergency tape. POPULATION: Derivation set: Two hundred five children undergoing elective surgery. Validation set: Two hundred thirteen children undergoing elective surgery. Each child served as his or her own control. METHODS: Derivation phase: Two hundred twenty-one children undergoing ET intubation for elective surgery had their body length and leak pressures measured. The 205 children who had leak pressures between 10 and 40 cm H2O constituted the derivation set. The body length for a given ET tube size was derived from the interquartile range of patient lengths in this derivation set. Sizes for other resuscitative equipment items were chosen by a panel of experts using a modified Delphi technique. This information was placed by length on a color-coded tape. Validation phase: The tape was validated by using it to select ET tube size in another group of 203 children undergoing elective surgery. Criteria for acceptable fit in this group included leak pressure as above and the anesthesiologists' decision to accept the tube size or to retintubate. In the validation phase, length-based ET tube selections were compared with age-based rules: (age + 16)/4, and (age + 18)/4. RESULTS: The tape selected the appropriate ET tube size by leak pressure criterion in 77% of the cases and was within +/- 0.5 mm of the "correct" size 99% of the time. This was significantly better (P less than .005) than two widely used age-based rules, which gave the correct initial size in only 47% and 9% of these cases, and were within +/- 0.5 mm for 86% and 59%. The anesthesiologists chose to continue with the tape-sized tube rather than to reintubate in 89% of cases. CONCLUSION: A system for length-based selection of emergency equipment represents a significant adjunct to emergency physicians and paramedics who must deal with critically ill children. Length-based ET tube selection is clearly superior to age-based rules, which are difficult to remember and require accurate estimation of a patient's age.

Body Height↗
PubMed1992

Prophylactic antibiotics for the prevention of infectious complications including empyema following tube thoracostomy for trauma: results of meta-analysis.

Since 1977, six clinical trials have been performed on the subject of routine antibiotic prophylaxis in patients requiring tube thoracostomy for trauma. No definitive conclusions have been reached regarding the efficacy of antibiotic use in this setting. The results of these clinical trials were pooled to generate an unbiased estimate of the efficacy of antibiotic prophylaxis for tube thoracostomy using the technique of meta-analysis. Meta-analysis is a statistical method for synthesizing results from separate but similar experiments, grouping them, and comparing each to the null hypothesis. Meta-analysis allows synthesis of all of the available data on antibiotic prophylaxis for tube thoracostomy to resolve the controversy surrounding this issue generated by different but similar clinical studies with conflicting results. Despite different conclusions of value when taken individually, the combined analysis does not support the null hypothesis (no effect of antibiotics). The statistical method is highly significant despite different mechanisms of injury, pathologic findings, and antibiotics employed.

Anti-Bacterial Agents↗
PubMed1991

An analysis of emergency physicians' cumulative career risk of HIV infection.

STUDY OBJECTIVE: To determine point and range estimates of the cumulative career risk of occupationally acquired human immunodeficiency virus (HIV) infection by emergency physicians as well as to determine if the efficacy of universal precautions was seriously diminished by prolonged risk over time. DESIGN: Monte Carlo estimation of a mathematical model of cumulative risk. Eight scenarios were estimated for high versus low prevalence of HIV, no precautions versus universal precautions, and prevalence increasing to a steady state versus peaking and then declining. MEASUREMENTS AND MAIN RESULTS: For high-prevalence areas, not using universal precautions, and assuming HIV seroprevalence increases to a steady-state level, the median estimate of cumulative risk of HIV infection over a 30-year career was 1.4% (90% of tolerance range, 0.2% to 14.0%); for low-prevalence emergency departments, the median was 0.1% (0.001% to 3.6%). Universal precautions with a presumed effectiveness of approximately 40% resulted in an approximate 30% decrease in risk. CONCLUSIONS: Although the per-exposure risk is small, the cumulative risk of HIV infection may be disproportionately large. The efficacy of universal precautions does not appear to be substantially diminished over time.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Diagnostic and prognostic importance of comparing the initial to the previous electrocardiogram in patients admitted for suspected acute myocardial infarction.

Two hundred fifty-eight patients were admitted to the hospital for suspected acute myocardial infarction. Electrocardiograms recorded on admission (initial ECG) and the most recent available electrocardiogram recorded before admission (previous ECG) were compared to determine whether changes from the previous to initial ECG predicted acute myocardial infarction or complications of coronary artery disease. Initial ECGs were classed as either positive or negative, with positive indicating either infarction, injury, ischemia, strain, left ventricular hypertrophy, left bundle branch block, or paced rhythm. Negative ECGs were those that did not include any of the positive criteria. Positive and negative ECGs were subgrouped as showing change or no change from previous ECG. We found that patients with a negative initial ECG that had changed from the previous ECG had a 2.1 times greater risk for requiring interventions than those patients whose ECGs were unchanged. We also found that patients with a positive initial ECG that had changed from the previous ECG had a greater risk for interventions (2.0 times), complications (2.6 times), life-threatening complications (4.2 times), and acute myocardial infarction (6.6 times) than the sum of patients in all other ECG categories. We conclude that change is a useful predictor for interventions in patients with negative initial ECGs and a useful predictor for interventions, complications, and acute myocardial infarction in patients with positive initial ECGs.

Coronary Disease↗
PubMed1990

Load and go versus stay and play: analysis of prehospital i.v. fluid therapy by computer simulation.

A computer-simulation model of prehospital hemorrhage and fluid resuscitation was used to determine under what circumstances it is advantageous to begin fluid resuscitation in the field instead of immediately transporting to the hospital. Four hypothetical bleeding rates (15, 25, 50, and 100 mL/min) were examined for short and long prehospital times. No significant difference in survival was noted for bleeding rates of 15 mL/min for either short or long time; a small but statistically significant increase in survival was noted for bleeding rates of 25 mL/min and long transport times. For both short and long times, all higher bleeding rates showed greater survival with prehospital fluid resuscitation and higher blood pressure at the onset of definitive care.

Computer Simulation↗
PubMed1989

The utility of the presence or absence of chest pain in patients with suspected acute myocardial infarction.

In 422 patients admitted from the emergency department (ED) for suspected acute myocardial infarction, the hypothesis that chest pain that persists on arrival in the ED or recurs during the initial ED evaluation is a useful predictor of acute myocardial infarction (AMI) and complications of coronary ischemia was tested. Compared with patients whose chest pain spontaneously ceased before arrival in the ED, patients whose chest pain persisted or recurred during the initial ED evaluation had a 2.3 times greater risk of interventions (P less than .001), a 1.7 times greater risk of complications (P = .045), a 3.8 times greater risk of life-threatening complications (P = .04), and a 2.4 times greater risk of AMI (P = .005). A third group of patients with suspected AMI never experienced chest pain. This group of patients who never experienced chest pain had a three times higher risk of death (P = .02) compared with patients whose chest pain persisted or recurred in the ED, and a 2.1 times greater risk of intervention (P = .01), a 5.2 times greater risk of life-threatening complication (P = .015), and a 7.9 times greater risk of death (P = .025) compared with patients whose chest pain resolved before arrival in the ED. It was concluded that patients with chest pain that resolves spontaneously before arrival to the ED have a better in-hospital prognosis than any other group.

Chest Pain↗
PubMed1989

Initial ECG in Q wave and non-Q wave myocardial infarction.

The initial ECGs in 440 patients admitted for suspected acute myocardial infarction were retrospectively analyzed to determine predictive values of these ECGs for acute myocardial infarction and to determine differences in the initial ECG for Q wave and non-Q wave myocardial infarction. One hundred (23%) of the study patients were diagnosed as having an acute myocardial infarction. Acute injury was seen in 47% of these patients (positive predictive value [PPV], 84%; 95% confidence interval [CI], 72% to 92%), ischemia in 15% (PPV, 39%; 95% CI, 24% to 57%), and left ventricular hypertrophy with strain in 11% (PPV, 19%; 95% CI, 4% to 29%). Forty-three patients were diagnosed as having a Q wave infarction and 50 patients as having a non-Q wave infarction. Seventy-two percent of the patients with a Q wave infarction had acute injury as the initial ECG interpretation compared with 38% in the non-Q wave infarction group (P less than .001). In contrast, only 17% of patients with Q wave infarction had an initial ECG interpretation of ischemia or strain as compared with 36% of patients with non-Q wave infarction (P = .03). Because of the relatively high incidence of acute myocardial infarction in patients admitted with an initial ECG interpretation of ischemia or left ventricular hypertrophy with strain, prospective studies must be performed to determine if selective patients with acute ST segment depression or ischemic T wave inversion in the setting of suspected acute myocardial infarction may benefit from early thrombolytic therapy.

Electrocardiography↗
PubMed1989

How many myocardial infarctions should we rule out?

We used computer simulation to estimate the consequences of four admitting strategies (coronary care unit, intermediate care unit, routine ward care, or outpatient follow-up) on cost, outcome, admission threshold probabilities, and false-positive admission rates for patients with acute myocardial infarction. At virtually any probability of acute myocardial infarction, replacing more intensive by less intensive strategies saved money but increased mortality and decreased life expectancy. Therefore, choices among strategies may be made by using the most effective strategy for progressively lower and lower risk patients until the additional cost per additional life saved reaches a cutoff value; then, a less expensive strategy is selected. With sample cutoff values of $1 and $2 million per life saved, the marginal threshold admission probabilities were: (table; see text) These results imply that the acceptable proportion of false-positive admissions may be as high as 70% to 80%; lower rates could indicate excessively restrictive admitting policies. Clinicians may be operating closer to the optimal decision point than has previously been asserted.

Coronary Care Units↗
PubMed1989

Risk stratification according to the initial electrocardiogram in patients with suspected acute myocardial infarction.

Previously developed initial electrocardiogram (ECG) prediction rules were modified to stratify 426 patients with suspected acute myocardial infarction into low-, intermediate-, and high-risk groups (normal, abnormal, and positive ECG categories) for development of acute myocardial infarction and complications of coronary ischemia. Compared with patients with normal ECGs, patients with positive ECGs had a 2.9 times greater risk of interventions, a greater risk of life-threatening complications, and a 14.2 times greater risk of acute myocardial infarction. Compared with patients with abnormal ECGs, patients with positive ECGs had a 1.7 times greater risk of interventions, a 2.6 times greater risk of life-threatening complications, and a 4.9 times greater risk of acute myocardial infarction. This prediction scheme was further improved by assigning "high" risk to any patient requiring an acute intervention during the initial evaluation in the emergency department. Otherwise, risk was assigned according to the ECG category, with normal, abnormal, and positive ECGs corresponding to "low," "intermediate," and high risk, respectively. Hospitals with limited intensive care beds may be able to use these prediction rules as an aid in determining in-hospital disposition of patients with suspected acute myocardial infarction.

Electrocardiography↗
PubMed1988

Serum amylase levels in ectopic pregnancy.

Thirty-four women with abdominal complaints and a positive pregnancy test were evaluated for possible ectopic pregnancy (EP). Serum amylase levels were obtained as part of the diagnostic workup to note any correlation of enzyme levels with the presence of EP. Thirteen individuals (30%) were subsequently diagnosed as having an EP, and serum amylase levels in all of these patients were within normal limits, averaging 81 U/L. There was no statistically significant difference in amylase levels between the EP group and the non-EP group (P = .70). Serum amylase levels cannot reliably predict the presence of EP and should not be used as a screening or diagnostic test for this disorder.

Adolescent↗
PubMed1979

Circumventing the Henderson-Hasselbalch equation.

Prompt blood-gas analysis consisting of pH, PCO2, and PO2 is now almost universally accessible. PCO2 directly conveys the role of the respiratory mechanism in any acid-base disturbance. The metabolic condition, however, is hidden in a relationship between pH and PCO2 that is most faithfully expressed by the cumbersome Henderson-Hasselbalch equation (HHE). Two methods of quickly determining metabolic status from pH and PCO2, without resorting to the HHE, are discussed. The first method is well known and adjusts pH to represent only metabolic state by quantitatively cancelling the influence of hyper- or hypoventilation. The second method, not previously reported, uses measured pH to estimate the ratio [HCO3-]/PCO2, which, when multiplied by PCO2, equals bicarbonate ion concentration.

Acid-Base Imbalance↗