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Biomedical subjects

M F Roizen

Publications and source records attributed to M F Roizen.

At least 73 records · Page 4Linked to original sources
PubMed1994

Guidelines, practice policies, and parameters: the case for geriatrics.

OBJECTIVE: As the population ages, the care of older persons becomes more important. At the same time, practice guidelines that provide recommendations for appropriate care are being published in greater numbers. The purpose of this work is to determine the proportion of guidelines that contain specific information about older persons. DESIGN: Through a random sample of published guidelines listed in the AMA Directory of Practice Parameters, 1992 Edition, we determined the proportion of guidelines that contain specific age-related information. We also determined if, over time, there was a difference in the proportion of practice guidelines containing information about older persons. RESULTS: 45.9% (95% CI, range 33.4-58.4) of guidelines that could conceivably pertain to older persons contain no age information; 24.6% (95% CI, range 13.8-35.4) of guidelines contain information only about persons less than 65 years of age; 29.5% (95% CI, range 18.1-41.0) of guidelines contain specific information about older persons. Moreover, there were no secular trends in the proportion of guidelines pertaining to older persons. CONCLUSIONS: Only a minority of practice guidelines contain information about older persons. Possible causes and solutions to this shortfall are discussed.

Age Factors↗
PubMed1994

Predictive and diagnostic tests of renal failure: a review.

Postoperative acute renal insufficiency is a discouraging complication with a mortality rate that remains persistently high, despite improved techniques of dialysis and advances in the perioperative management of hemodynamic, metabolic, and infective complications. A complete understanding of the role of renal hemodynamics in the pathophysiology of acute renal failure still has not emerged. Serial determination of creatinine clearance is currently the most sensitive test for predicting the onset of perioperative renal dysfunction; however, the test is not practical for measuring renal function under operating room conditions. Furthermore, testing creatinine clearance is time-consuming, labor intensive, and may cause significant delay in identifying the onset of renal dysfunction. That early therapy modifies the prognosis of renal dysfunction remains an untested hypothesis until a measurement that predicts renal outcome is found that is sensitive, specific, and easily obtainable. The ability to measure intrarenal blood flow distribution may offer promise for improving our predictive and diagnostic abilities to assess perioperative acute renal failure. Methodologic constraints, however, limit the practicality of this measurement in the perioperative setting at this time. Instead, we rely on indirect variables that do not bear a reliable relationship to glomerular filtration rate and renal function.

Acute Kidney Injury↗
PubMed1994

Association of preoperative risk factors with postoperative acute renal failure.

We performed a systematic review of 28 studies that examined preoperative risk factors for postoperative renal failure. Included in the studies were 10,865 patients who underwent either vascular, cardiac, general, or biliary surgery. No two studies used the same criteria for acute renal failure. Variability in definitions of renal failure, lack of consistent criteria for establishing risk factors, and nonuniformity in the statistical methods employed result in a literature that is not adequate to support a comprehensive quantitative review. Of the 30 variables considered in the studies, preoperative renal risk factors, such as increased serum creatinine, increased blood urea nitrogen, and preoperative renal dysfunction were repeatedly found to predict postoperative renal dysfunction. The literature provides little quantitative information concerning the degree of risk associated with other factors. Cardiac risk factors, such as left ventricular dysfunction, were reported to be predictive of postoperative renal failure more consistently than was advanced age.

Acute Kidney Injury↗
PubMed1994

Efficacy of methylnaltrexone versus naloxone for reversal of morphine-induced depression of hypoxic ventilatory response.

Methylnaltrexone (MNTX) is a quaternary derivative of naltrexone. It does not cross the blood-brain barrier and, thus, it reverses peripherally mediated effects of morphine without blocking its centrally located analgesic effects. The effects of MNTX on morphine-induced depression of hypoxic ventilatory response are unknown. We evaluated the efficacy of MNTX, compared with naloxone, in reversing this effect. On three sessions separated by a week, 10 healthy male volunteers received morphine, 0.125 mg/kg, as a bolus at 20 min after completing a control hypoxic ventilatory challenge. At 60 min, naloxone, 5 micrograms/kg, MNTX, 0.3 mg/kg, or placebo was administered in a randomized double-blind order. Four isocapnic hypoxic ventilatory challenges were conducted: 0 min (control), 40 min (postmorphine), and 80 and 120 min (postreversal) and the hypoxic respiratory responses were recorded. Morphine administration was associated with a significant depression in hypoxic responses: The slope of the response (L/min/Spo2) and the predicted ventilation at 80% O2 saturation (VE80) (L/min) decreased significantly in the three sessions (P < 0.05). Naloxone injection reversed the respiratory depression at 80 min (85% of the control value of the slope and 89% of VE80), whereas MNTX and placebo did not. At 120 min, the slope (69%) and VE80 (80%) after naloxone administration were not significantly different from control. MNTX slope (69%) was not statistically different from the control, whereas VE80 (70%) was still depressed (P < 0.05). Placebo slope and VE80, at 120 min, remained lower than the control (P < 0.05). These data show that MNTX is not as effective as naloxone for reversal of morphine-mediated depression of respiration during acute hypoxia.

Adult↗
PubMed1994

Relative effectiveness of four preoperative tests for predicting adverse cardiac outcomes after vascular surgery: a meta-analysis.

Various noninvasive tests have been proposed to stratify perioperative cardiovascular risk, including dipyridamole thallium scintigraphy (DTS), ejection fraction estimation by radionuclide ventriculography (RNV), ischemia monitoring by ambulatory electrocardiography (AECG), and dobutamine stress echocardiography (DSE). Which of these tests is most effective for predicting adverse perioperative cardiac outcome? To answer this question, and also to stimulate future studies, we evaluated 56 studies examining one or more of the four tests. We conducted meta-analysis on 20 studies that met the inclusion criteria. Outcome measures evaluated were cardiac death or myocardial infarction occurring during hospital stay or within 1 mo after surgery. Relative risk (RR), which is the probability of adverse cardiac outcome when the test is positive divided by the probability of adverse outcome when the test is negative, was used to combine evidence from different studies. An empirical Bayes procedure with a normal-normal hierarchic model was then used to obtain a meta-analytic confidence interval for the overall median of the relative risks. The between-study variance was estimated using the method of moments approach described by DerSimonian and Laird (Controlled Clin Trials 1986;7:177-88). Combined (median) RR [95% confidence interval (CI)] and the number of studies included in our meta-analysis for different evaluative tests were as follows: DTS 4.6 (2.1-10.4) (n = 6); RNV 3.7 (1.6-8.3) (n = 5); AECG 2.7 (1.4-5.1) (n = 6), and DSE 6.2 (1.7-22.8) (n = 3). We conclude that while DTS, RNV, AECG, and DSE are effective (the 95% CIs are greater than 1.0) in predicting the cardiac outcome after vascular surgery, the data are not definitive in determining the optimal test (95% CIs for RR overlap). Future studies should include DSE, as this test shows great promise for predicting adverse cardiac events after vascular surgery.

Coronary Angiography↗
PubMed1994

A comparison of two formulations for etomidate, 2-hydroxypropyl-beta-cyclodextrin (HPCD) and propylene glycol.

The unphysiologic osmolality of commercial preparations of etomidate dissolved in propylene glycol has limited its use as a drug to induce anesthesia. We wanted to determine whether hydroxypropyl-beta-cyclodextrin (HPCD) is a more suitable solvent than propylene glycol by comparing pharmacokinetics, pharmacodynamics, and side effects of etomidate preparations in each solvent. Twenty-four healthy, male volunteers, randomly assigned to either the male volunteers, randomly assigned to either the HPCD or the propylene glycol group received etomidate, 0.3 mg/kg, dissolved in one of the two test solvents. We recorded arterial blood pressure, heart rate, electrocardiogram, electroencephalogram, pain on injection, myoclonic movements, and venous sequelae. Systolic and diastolic blood pressure and heart rate were similar in both groups. Frequency and severity of pain on injection differed significantly between groups. In the propylene glycol group, five subjects suffered venous sequelae: in three, thrombophlebitis resolved after 5 days; in one, after 10 days; and in the other, after 12 days. In the HPCD group, only one subject suffered severe pain on injection and none had venous sequelae. We conclude that HPCD may be superior to propylene glycol as a solvent for etomidate. HPCD is associated with less pain, less thrombophlebitis, and no hemolysis without clinically important alteration of pharmacokinetics or pharmacodynamics of etomidate.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1994

Preoperative evaluation of patients: a review.

Patients undergoing surgery move through a continuum of medical care to which a primary care physician, an internist, an anaesthesiologist, and a surgeon contribute to ensure the best outcome possible. No aspect of medicine requires greater cooperation than the performance of surgery and the perioperative care of a patient. For the anaesthesiologist, this responsibility should start in a preoperative clinic. The importance of integrating practice is even greater because of the increasing life span of our population. As the number of elderly patients increases, so does the need for preoperative consultation to plan for comorbidities and multiple drug regimens, knowledge of which is crucial to successful patient management. At a time when medical information is encyclopaedic, it is difficult for even the most conscientious anaesthesiologist or surgeon to keep abreast of medical issues relevant to perioperative patient management. Thus, a proposed preoperative assessment clinic facilitates those most sought-after goals, increased quality and reduced costs. As part of this process, ordering only laboratory tests warranted by a patient's symptoms and medical history is important to avoid risks of unnecessary testing and of follow-up of false-positive results.

Adult↗
PubMed1993

Pulse oximetry, capnography, and blood gas measurements: reducing cost and improving the quality of care with technology.

Pulse oximetry appears to improve quality of care by the early detection of hypoxia noninvasively. We tested the hypothesis that the widespread use of pulse oximetry over a 5-year period in the operating rooms at our institution had resulted in a reduction in blood gas measurements and in departmental operating costs. The total number of blood gas determinations per hour of anesthetic time at our institution decreased by 44%, from 7.64 to 4.26 measurements per 100 operating room hours. The number of capnography units in the operating rooms increased from 8 to 14, the number of pulse oximeters increased from 0 to 22, and oximeter use increased from 0 to 100% for all anesthetics. The total cost to provide oximetry, capnography, and blood gas measurements in 1989-1990 was less than the cost to provide blood gas measurements alone in 1985-1986. The introduction of these technologies was accomplished without an increase in cost: $76,880 in 1985-1986 versus $71,025 in 1989-1990.

Anesthesiology↗
PubMed1993

Assessment of renal blood flow with contrast ultrasonography.

Sonicated albumin microspheres, a digitalizing ultrasound system, and a mathematical model for flow were used to determine whether blood flow in the canine kidney could be assessed with contrast ultrasound. Albunex ultrasound contrast microspheres were injected into the aorta while ultrasound images of the kidney and aorta were recorded simultaneously. Ultrasound data were obtained during contrast injections at 93 different renal blood flow rates in nine dogs. Contrast dose was calibrated to ultrasound system response for both aortic and renal images. A linear relationship between microbubble concentration used and pixel intensity was established (r = 0.89 for aortic images and r = 0.91 for renal images). Renal blood flow was manipulated from baseline by means of a hydraulic renal artery occluder and by intravenous dopamine or fenoldopam infusion. Blood flow calculated with contrast ultrasonography was compared with direct measurement obtained with an electromagnetic flow probe at each flow rate. Direct measurement correlated with rates calculated with contrast ultrasonography (r = 0.84, 95% confidence limits from 0.75 to 0.90). Overall, calculations tended to overestimate absolute flow measurements, and overestimation of flow tended to be greater during pharmacologically manipulated flow rates. We conclude the changes and trends in renal blood flow can be serially assessed in vivo with contrast ultrasonography, but technical limitations of present commercial ultrasounds systems preclude absolute quantification at this time.

Albumins↗
PubMed1993

A proposal to use confidence intervals for visual analog scale data for pain measurement to determine clinical significance.

Visual analog scales (VAS) ranging from 0 cm (no pain) to 10 cm (worst imaginable pain) are used widely for pain measurement, but various investigators have not treated these data consistently. Conventional statistical tests of such data, although evaluating the "statistical significance" may obscure the clinical value of a treatment. On the other hand, confidence intervals (CIs) can illuminate both statistical and clinical importance. CIs give a range of values based on the observed data which contain, with a specified probability, a true but unknown variable typifying a population. We reviewed 112 articles published recently in anesthesia journals for statistical reporting of VAS data. Of the 112 articles, only two used CIs to report mean pain scores and one used CIs to report differences in median pain scores between the study groups. Only two articles presented 95% CI for the mean pain scores graphically. Analgesic techniques that produce VAS values in the range of 0-3 have been reported to represent adequate analgesia. A graphical method using CIs is proposed that allows ready interpretation of VAS data. With this approach, one evaluates whether the 95% CI for the mean pain score in a group during a particular period lies entirely within the zone defined as "analgesic success" (0-3). Such an analysis allows a visual assessment of whether a particular technique would produce clinically important effects in the population at large. This approach seems to provide more information than the use of conventional hypothesis testing in the interpretation of VAS data for pain measurement.

Confidence Intervals↗
PubMed1993

The initial clinical experience of 1819 physicians in maintaining anesthesia with propofol: characteristics associated with prolonged time to awakening.

In October 1989, propofol underwent Phase IV Food and Drug Administration testing that involved 25,981 patients, 1722 institutions, and 1819 anesthesiologists. Participants were 18-80 yr of age and ASA physical status I-III; they could not have a continuing pregnancy or prior adverse anesthetic experience. Anesthesiologists completed detailed forms to describe their use of propofol in this three-step study: propofol for induction only (Step 1), for induction and then maintenance by intermittent bolus injection (Step 2), or for continuous infusion (Step 3). In early 1992, our group of anesthesiologists and epidemiologists analyzed the resulting data base. We evaluated data from 14,882 patients (8095 given bolus injections and 6787 given continuous infusion) to determine factors predicting prolonged time (> 15 min after cessation of all anesthesia) to awakening, one measure of recovery from anesthesia. The incidence of prolonged awakening was 6.8% (1016 patients); the median and mean (+/- SD) times to awakening were, respectively, 5 min and 7.2 +/- 7.3 min. The following variables were associated (P < 0.05) with prolonged awakening from propofol maintenance anesthesia: a total dose of propofol > 8 mg/kg, male gender, endotracheal intubation, age > 65 yr, abdominal surgery, continuous infusion of propofol, and concomitant use of isoflurane or benzodiazepines. These results support the clinical impression that recovery from propofol anesthesia is remarkably rapid; although the vast majority of physicians participating in this study were using propofol for maintenance for the first time, only 6.8% of patients had awakening times exceeding 15 min.

Adolescent↗
PubMed1993

Effects on recovery when isoflurane is used to supplement propofol-nitrous oxide anesthesia.

During propofol-nitrous oxide (N2O) anesthesia, volatile anesthetics are frequently administered to treat signs of inadequate anesthesia and to decrease the possibility of intraoperative awareness. Because the clinical effects of this combination have not been examined rigorously, we used data from the 1989-90 Phase IV clinical trial with propofol to evaluate recovery from propofol-N2O anesthesia with and without supplementation with isoflurane. In this study involving 15,806 patients at 1722 institutions, propofol was administered for induction and maintenance of anesthesia with N2O for procedures lasting less than 60 min. At the discretion of the anesthesiologist, volatile anesthetics were administered as needed during maintenance of anesthesia (the incidence of use of inhaled anesthetics was 14.7% for isoflurane, 2.2% for enflurane, and 0.2% for halothane). Other intraoperative medications included opioid analgesics, muscle relaxants, and anticholinergic drugs. The present study concerns the subset of 7796 patients given propofol-N2O maintenance anesthesia (intermittent bolus or continuous infusion) with or without isoflurane supplementation for procedures lasting less than 60 min. Isoflurane was used more frequently for procedures lasting 30-60 min than for those less than 30 min. Nevertheless, the maintenance dose of propofol was significantly (P < 0.05) less with isoflurane (178 vs 235 mg). Adjunctive use of isoflurane prolonged the time to awakening and to becoming oriented, but discharge times were similar for the two groups. The incidence of postoperative nausea, vomiting, recall, and excitement did not differ between the two groups. We conclude that the addition of isoflurane to a propofol-N2O anesthetic does not alter recovery from anesthesia.

Adolescent↗