Biomedical subjects
V A Lawrence
Publications and source records attributed to V A Lawrence.
The impact of new clinical guidelines on the North American blood economy.
Explore the source record for details and available documents.
The relationship between disease and function and perceived health in very frail elders.
OBJECTIVE: To study associations between disease and observed function and self-perceived health in very frail elders. DESIGN AND SETTING: Cross-sectional survey of nine nursing homes in San Antonio, TX. PARTICIPANTS: 194 elderly long-stay nursing home residents dependent in at least two ADLs and without severe cognitive impairment. MEASURES: Burden of disease (BOD) was chart abstracted using a standardized protocol that assessed types and severities of 59 categorizations of chronic and acute medical conditions. Observed function and self-perceived health status were assessed independently by the Katz Activities of Daily Living scale (ADL) and the Sickness Impact Profile (SIP), respectively. RESULTS: Summary BOD scores had a low, but statistically significant, univariate correlation with ADL scores (r = 0.21, P = 0.003) and no significant correlation with SIP scores (R = -0.008). Multiple linear regression analyses, including the 24 most frequent disease categories, showed that disease explained significant amounts of ADL (r2 = 0.25, P = 0.001) and borderline significant amounts of SIP (r2 = 0.16, P = 0.11). Models including both disease and sociodemographic, cognitive, and affective variables showed disease added significant incremental explantation beyond the other factors to ADL (incremental r2 = 0.14, P = 0.04), but not to SIP (incremental r2 = 0.08, P > 0.10). CONCLUSIONS: Disease, observed function, and self-perceived health status are separate, but interrelated entities, with disease having a stronger relationship to observed function than self-perceived health. Comprehensive assessment of frail elders may need to include all three areas, and studies that focus on one area should take into account the other two as potential important covariates.
Preoperative HIV testing: is it less expensive than universal precautions?
Universal precautions are officially recommended to prevent HIV transmission in health care settings but for elective surgery some advocate routine preoperative HIV testing. These strategies have not been tested in clinical trials but universal precautions are very expensive and not cost-effective. Thus, for elective surgery, routine testing might save resources by permitting selective use of additional barrier precautions. We performed an economic evaluation to compare both strategies, using a simple approach to determine if routine testing (RT) is less expensive than universal precautions (UP). Conservatively assuming equal effectiveness in preventing HIV transmission, we compared a minimized estimate for the average cost of RT with a maximized estimate for the average cost of UP per elective operation. The minimized estimate for RT (US$57) was greater than the maximized estimate for UP (US$36) per procedure. Results were stable or strengthened by sensitivity analysis. Routine HIV testing is not a valid economic alternative to UP for elective surgery. The simple methodology used in this study can be a preliminary strategy to review other strategies for preventing HIV transmission. This method is particularly useful when data are inadequate for a formal economic evaluation to determine the utility of collecting the detailed information necessary for a full comparison.
Evidence-based vs emotion-based medical decision-making: routine preoperative HIV testing vs universal precautions.
Explore the source record for details and available documents.
Postoperative complications after thoracic and major abdominal surgery in patients with and without obstructive lung disease.
STUDY OBJECTIVE: To determine the risk of thoracic and major abdominal surgery in patients with chronic obstructive pulmonary disease (COPD). DESIGN: Retrospective cohort study with controls. SETTING: A 692-bed teaching hospital. PATIENTS: A cohort of 26 patients with severe COPD (FEV1 < 50 percent predicted) undergoing thoracic and major abdominal surgery was matched by age and type of operation to 52 patients with mild-moderate COPD and 52 patients with no COPD. MEASUREMENTS AND RESULTS: The 26 patients with severe COPD had rates of cardiac, vascular, and minor pulmonary complications similar to patients with mild-moderate COPD and without COPD, but experienced higher rates of serious pulmonary complications (23 percent vs 10 percent vs 4 percent, p = 0.03) and death (19 percent vs 4 percent vs 2 percent, p = 0.02). All deaths and instances of ventilatory failure in the patients with severe COPD occurred in the subset undergoing coronary artery bypass surgery. Logistic regression revealed that increased age, higher American Society of Anesthesiologists class, an abnormal chest radiograph, and perioperative bronchodilator administration were associated with higher cardiac or serious pulmonary complication rates. Spirometry was not an independent predictor of postoperative complications. CONCLUSIONS: Clinical variables appear better than preoperative spirometry in predicting postoperative cardiopulmonary complications. The utility of preoperative spirometry as well as the benefits of perioperative bronchodilators in patients in stable condition remain to be determined.
Acute low back pain and economics of therapy: the iterative loop approach.
We use the measurement iterative loop as a conceptual framework to examine the economics of common therapies for acute non-specific low back pain. The measurement iterative loop systematically assesses the interlocking facets of an illness from the community health perspective, including quantifying burden of illness, etiology, assessment of therapeutic effectiveness, and economic evaluation of therapies. The iterative loop reveals that: (1) burden of illness, although known to be substantial, is so far inaccurately measured, (2) little is known about such factors as provider and patient compliance; and (3) the economics of therapy can guide us in this time of clinical uncertainty when no therapy appears clearly superior. For therapies with at least some support from randomized controlled trials, bedrest appears to be economically superior. Besides burden of illness, compliance, and current therapies, future research should address such "therapeutic" options as early return to work and patient self-management.
Operative risk in patients with severe obstructive pulmonary disease.
BACKGROUND: We wanted to determine the risk of postoperative pulmonary complications and mortality in patients with severe chronic obstructive pulmonary disease. METHODS: We reviewed 107 consecutive operations performed in 89 patients with severe chronic obstructive pulmonary disease (forced expiratory volume in 1 second, less than 50% of predicted). RESULTS: Postoperative pulmonary complications occurred in 31 operations (29%) and were significantly related to the type and duration of surgery. Also, American Society of Anesthesiologists class approached significance as a predictor. Postoperative pulmonary complications occurred at higher rates in coronary artery bypass grafting and major abdominal procedures (60% and 56%) than in other operations involving general or spinal anesthesia (27%) or in procedures performed with the patient under regional or local anesthesia (16%). When the durations of the operations were classified as less than 1 hour, 1 to 2 hours, 2 to 4 hours, and more than 4 hours, the rates of postoperative pulmonary complications were 4%, 23%, 38%, and 73%, respectively. Regarding American Society of Anesthesiologists class, postoperative pulmonary complications occurred in 10% of patients in class II, 28% of those in class III, and 46% of those in class IV. In terms of life-threatening complications, there were six deaths and only two cases of nonfatal ventilatory failure. Notably, mortality clustered primarily in coronary artery bypass graft procedures. Five of 10 patients receiving coronary artery bypass grafts died, compared with one death after 97 non-coronary artery bypass graft operations (50% vs 1%). CONCLUSIONS: Although the risk of coronary artery bypass grafting deserves further study, noncardiac surgery carries an acceptable operative risk in patients with severe chronic obstructive pulmonary disease.
The unproven utility of the preoperative urinalysis: economic evaluation.
The clinical effectiveness of the preoperative urinalysis is unproven, yet it is routinely obtained before surgery. To determine if the routine urinalysis might be economically beneficial, we evaluated its cost-effectiveness and cost-benefit. In the setting of elective clean-wound, non-prosthetic knee procedures, we estimated that: (1) nearly U.S. $7,000,000 is spent annually on preoperative urinalyses and associated costs; (2) given the best estimate of the increase in risk of wound infection attributable to urinary tract infection, 4.58 wound infections may be prevented annually, at a cost of $1,500,000 per wound infection prevented; (3) the cost of treating additional cases of wound infection, given no preoperative urinalysis, is approximately five hundred-fold less than the cost of screening with routine urinalyses. We conclude that the routine preoperative urinalysis is clinically and economically unsound before clean-wound, non-prosthetic knee surgery and probably before other types of clean-wound surgery. For this relatively inexpensive test, aggregate costs are disproportionately high and appear to outweight clinical benefits.
Preoperative spirometry before abdominal operations. A critical appraisal of its predictive value.
Preoperative spirometry is commonly ordered before abdominal surgery, with the goal of predicting and preventing postoperative pulmonary complications. We assessed the evidence for this practice with a systematic literature search and critical appraisal of published studies. The search identified 135 clinical articles, of which 22 (16%) were actual investigations of the use and predictive value of preoperative spirometry. All 22 studies had important methodological flaws that preclude valid conclusions about the value of screening preoperative spirometry. The available evidence indicates that spirometry's predictive value is unproved. Unanswered questions involve (1) the yield of spirometry, in addition to history and physical examination, in patients with clinically apparent lung disease; (2) spirometry's yield in detecting surgically important occult disease; and (3) its utility, or beneficial effect on patient outcome. Spirometry's full potential for risk assessment in the individual patient has not yet been realized.
The unproven utility of preoperative urinalysis. Clinical use.
We investigated the utility, ie, relevance to clinical outcome, of routine preoperative urinalysis with a retrospective study of 200 clean-wound, orthopedic, nonprosthetic knee procedures. Physicians primarily order a preoperative urinalysis to detect infection, because of the purported relationship between remote infection and surgical wound infection. We found that preoperative urinalysis is uniformly ordered, with a high prevalence of abnormal results (15%) but a low physician-response rate (29%). Wound infection was rare, but there was no difference in frequency of wound infection between patients with normal and abnormal results of urinalysis. We conclude that the utility of routine preoperative urinalysis is unproven. Current practice does not agree with the rationale for ordering this test, nor does published literature support it. Although data are inadequate to fully define the appropriate use of preoperative urinalysis, we suggest clinical recommendations and avenues for further research.
Cancer and resuscitation. Does the diagnosis affect the decision?
We asked if physicians are less likely to resuscitate patients with cancer because of the diagnostic label alone. We composed a questionnaire of nine patient vignettes with similar expected mortality rates, identical quality of life, and witnessed cardiopulmonary arrest. Internists and neurologists in a university training program were asked to decide, for each "patient," whether to administer cardiopulmonary resuscitation (CPR) before and after being informed of similar mortality rates. Decisions for CPR were less frequent for cancer vignettes than for vignettes of other chronic medical illnesses before and after mortality information was given. Analysis indicated that decisions varied among physicians according to their subspecialties. Overall, women favored resuscitation less often than did men. The diagnosis of cancer appears to have a negative impact on physicians' CPR decisions over and above that due to inaccurate prognostic assumptions about cancer. A physician's subspecialty and gender may also influence resuscitation decisions for patients in general.
Aspirin and folate binding: in vivo and in vitro studies of serum binding and urinary excretion of endogenous folate.
To clarify the effect of aspirin on folate balance, we studied serum concentration, protein binding, and urinary excretion of endogenous folate. A healthy woman twice followed an 11-day protocol of constant diet, blood sampling twice daily, collection of all urine, and 650 mg of aspirin by mouth every 4 hours on the middle 3 days. As determined by equilibrium dialysis and Lactobacillus casei assay, aspirin induced a brisk, significant but reversible fall in total and bound serum folate and a small but insignificant rise in urinary folate excretion. Aspirin in vitro also displaced significant amounts of bound serum folate. Thus, aspirin in therapeutic doses can contribute to subnormal serum folate values, and if it increases urinary folate excretion even slightly, may impair folate balance.
Demographic analysis of serum folate and folate-binding capacity in hospitalized patients.
Serum folate levels and unsaturated folate-binding capacity (UFBC) in a mixed population of outpatients and inpatients were analyzed with respect to race, sex, and age. The results supported the relatively high prevalence of subnormal serum folates in patient populations, did not find lower serum folates in the elderly, and revealed significantly higher UFBC in Negro patients, in male patients, and in patients older than 50 years.