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Biomedical subjects

M F Roizen

Publications and source records attributed to M F Roizen.

At least 19 recordsLinked to original sources
PubMed1992

Can patients use an automated questionnaire to define their current health status?

Patient management decisions rarely incorporate standardized health status assessments, since accurate and reliable measures are difficult and expensive to obtain. In prior research with various methods for obtaining health data from patients, it was found that physicians' acceptance of a method was improved if it provided an individualized printout. It was also determined that patients will readily complete a health status questionnaire on a computer when the computer does not look like a computer. Patients' acceptance was greatest when they were presented with a single line of large, pressure-sensitive buttons with which they could respond to questions about their health histories. Using such an instrument, the HealthQuiz, the current study found the same discrepancy rate (3%) between patients' responses to health questions presented on HealthQuiz and during interview as between their responses to questions asked during two separate interviews. Further, to ascertain health status, rules determined by an expert panel were applied to patients' responses to health questions presented on the HealthQuiz screen. It was found that the numerical health status derived from answers to the automated presentation of questions was similar to numerical health status derived by a physician after a patient-physician interview.

Aged↗
PubMed1992

Simple computer measurement of pulmonary VCO2 per breath.

Measurements of the volume of CO2 exhaled per breath (VCO2/br) are preferable to end-tidal PCO2, when the exhaled flow and CO2 waveforms may be changing during unsteady states, such as during alterations in positive end-expiratory pressure or alterations in cardiac output. We describe computer algorithms that determine VCO2/br from digital measurements of exhaled flow (including discontinuous signals common in anesthesia circuits) and CO2 concentration at the airway opening. Fractional concentration of CO2 is normally corrected for dynamic response and transport delay (TD), measured in a separate procedure. Instead, we determine an on-line adjusted TD during baseline ventilation. In six anesthetized dogs, we compared the determination of VCO2/br with a value measured in a simultaneous collection of expired gas. Over a wide range of tidal volume (180-700 ml), respiratory rate (3-30 min-1), and positive end-expiratory pressure (0-14 cmH2O), VCO2/br was more accurate with use of the adjusted TD than the measured TD (P less than 0.05).

Algorithms↗
PubMed1992

Risk of human immunodeficiency virus in surgeons, anesthesiologists, and medical students.

We postulated that three factors determined the occupational risk of infection from the human immunodeficiency virus (HIV) for surgeons, anesthesiologists, and medical students: first, the risk of needlestick exposure per year (range for surgeons 3.8-6.2, weighted average 4.2; range for anesthesiologists 0.86-2.5, weighted average 1.3; range for third-year medical students 0-5, best estimate 5); second, the risk of seroconversion from a needlestick exposure (0.42%-0.50%); and third, prevalence of HIV in the population served (0.32%-23.6%, depending on geographic location). Thus, the calculated range for occupational risk of HIV infection for a surgeon over a 30-yr period (assuming no change in HIV prevalence or benefit from protective measures) was 0.17%-13.9%; for an anesthesiologist, 0.05%-4.50%. The corresponding range of occupational risk for a medical student during the third year was 0.007%-0.59%. The range of risk is large because the variation in prevalence of HIV infection from one area to another is great. The authors validated the methodology first by using an equation, with estimates from the literature for factors in the equation, to calculate the risk of infection for hepatitis B and then by comparing the results with known rates of infection in the prevaccine era. Calculated occupational risk of hepatitis B infection for anesthesiologists was in the lower range of actual prevalence of infection (calculated range 2.32%-20.6%; known range 6%-26%). Calculated risk versus prevalence for surgeons was fairly close (7.31%-53.4% versus 24.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesiology↗
PubMed1992

Echocardiographic analysis of dysfunctional and normal myocardial segments before and immediately after coronary artery bypass graft surgery.

Echocardiography has revealed evidence of "subnormal" regional contraction patterns that result from myocardial ischemia and are often accompanied by nonadjacent "hyperkinetic" regions. Whether these regions of hyperkinetic wall motion persist unchanged or revert to normal after coronary artery bypass graft (CABG) surgery has not been studied in humans. Using echocardiography, we evaluated both dysfunctional and normal myocardial regions for changes in segmental wall motion and percent of systolic wall thickening that occurred immediately after CABG surgery in 32 patients. Segmental wall motion analysis before CABG surgery in these patients revealed that 170 (66%) of 256 myocardial segments were subnormal, of which 115 (67%) improved and 102 (60%) returned to normal immediately after CABG surgery. Eleven myocardial segments that were hyperkinetic before CABG surgery returned to normal after CABG surgery. Preoperatively, 162 (63%) of 256 myocardial segments had systolic wall thickening less than 30%, which increased from 11.8% +/- 8.9% to 24.3% +/- 14.3% (mean +/- SD) (P less than 0.01) postoperatively. Conversely, a reverse trend was found when systolic wall thickening was greater than 30% before CABG surgery: thickening decreased from 46.2% +/- 13.8% to 33.4% +/- 14.8% after CABG surgery (P less than 0.01). Thus, we conclude that immediately after CABG surgery, there is a recovery of function in some myocardial segments and a reduction in function in others. Furthermore, we conclude that the semiquantitative assessment of percent of systolic wall thickening is a more reliable (consistent) echocardiographic index of myocardial function compared with the qualitative assessment of segmental wall motion immediately after CABG surgery.

Adult↗
PubMed1992

Osmolalities of propylene glycol-containing drug formulations for parenteral use. Should propylene glycol be used as a solvent?

Propylene glycol (PG) is a widely used vehicle for water-insoluble drugs. Injection of drugs formulated with this solvent often results in pain, thrombosis, or thrombophlebitis that can be reduced by premedication with local anesthetics or opioids. Because osmolality and pH that are unphysiologic may cause these adverse effects, we assessed the contribution of PG to the osmolality of parenteral drug formulations. Osmolality of PG measured in distilled water showed that PG content and osmolality were directly related: 2% wt/vol PG, 264 mOsm/L; 100% PG, 15, 200 mOsm/L. The osmolalities of commercially available preparations of drugs dissolved in PG ranged from 365 mOsm/L (2% PG content) to 12,800 mOsm/L (83.46% PG), with most above 1000 mOsm/L. Replacement of PG by a solvent with lower osmolality in Germany has effectively reduced the incidence of side effects for one drug. Until PG can be replaced in drugs, we recommend diluting drugs in a large volume of saline solution; this may help to minimize the undesirable effects of this solvent.

Anesthesiology↗
PubMed1992

A comparison of methods for the detection of myocardial ischemia during noncardiac surgery: automated ST-segment analysis systems, electrocardiography, and transesophageal echocardiography.

Clinicians often fail to detect intraoperative ischemic electrocardiographic (ECG) changes when viewing oscilloscopes. Automated ST-segment monitors promise to increase the detection of such ECG changes. We investigated the capacity of two commercially available ST-segment monitors to detect intraoperative myocardial ischemia in patients at high risk for developing intraoperative myocardial ischemia during vascular and other noncardiac procedures. The ST-segment monitors were compared with two reference monitors: (a) printed eight-lead ECGs, as interpreted by a cardiologist, and (b) the presence of segmental wall motion abnormalities and thickening abnormalities detected by transesophageal echocardiography (TEE). We also examined the capacity of the printed ECG to diagnose myocardial ischemia when compared with TEE. We studied 44 patients who underwent TEE, printed multilead ECG, oscilloscope monitoring of leads V5 and II, and measurement of ST-segment deviation from the baseline using an automated Hewlett Packard ST-segment device. The sensitivities for the Hewlett Packard system were 40% for TEE-diagnosed myocardial ischemia and 75% for ECG-diagnosed ischemia. Comparison of the printed ECG with TEE revealed that ST-segment changes in the printed ECG, as analyzed by a cardiologist, were 25% sensitive and 62% specific for the detection of TEE-diagnosed myocardial ischemia. When T-wave inversions were added to ST-segment depression as a criterion for the diagnosis of myocardial ischemia by the printed ECG, the sensitivity of ECG for the detection of intraoperative myocardial ischemia, as determined by TEE, was 40% and specificity was 58%. Twenty-three of the 44 patients were simultaneously monitored in leads I, II, and V5 with an automated Marquette ST-segment monitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Reassessment of preoperative laboratory testing has changed the test-ordering patterns of physicians.

To test the hypothesis that physicians have substantially reduced the ordering of unwarranted preoperative tests, the authors reviewed 2,093 medical records of patients having four surgical procedures performed at three institutions in three cities in 1979, 1981, 1983, 1985 or 1987. Excluding hemoglobin measurements, the incidence of ordering preoperative laboratory tests unwarranted by findings on history or physical examination decreased from 32.2 to 25.9 percent during this decade, representing a 19.6 percent reduction. This decrease was irregular and varied from operation to operation, test to test and institution to institution. Overall, the percentage of preoperative tests ordered that were unwarranted decreased from 66.9 percent in 1979 to 60.1 percent in 1987. Extrapolating these results, the authors estimate that more than $320 million was saved annually by elimination of unwarranted tests and that the potential savings could exceed $1.35 billion a year. Unexpectedly, the preoperative ordering of medically indicated tests also decreased (from 92.9 to 80.9 percent, representing a 12.9 percent reduction). Because the benefit of performing justified tests is probably greater than the benefit of avoiding unwarranted tests, the net change has probably not been beneficial. A better system for obtaining justified tests and for eliminating the unwarranted tests may be necessary before a net benefit occurs. Punitive measures to reduce testing without prior establishment of such a system may save money, but impair health.

Chicago↗
PubMed1991

Preventive care guidelines: 1991. American College of Physicians. Canadian Task Force on the Periodic Health Examination. United States Preventive Services Task Force.

Clinicians increasingly are urged to integrate preventive services into their clinical practices. To facilitate this process, several groups have developed practice guidelines for preventing disease in asymptomatic patients. In this paper, we compare and contrast preventive guidelines from the American College of Physicians (ACP), the Canadian Task Force on the Periodic Health Examination (CTF), the United States Preventive Services Task Force (USPSTF), and other well-known authorities. We chose these groups because they based their recommendations on explicit methods that include critical appraisal of the pertinent literature. Recommendations from these authorities usually are consistent with each other. Moreover, the ACP, CTF, and USPSTF all favor a shift away from the relatively simple classification of patients by age and sex for general preventive interventions to the more complex stratification of patients by additional risk factors and the formulation of a selective prevention strategy that is specific to each risk profile. Some guidelines, particularly the criteria used to define patients who are at increased risk for preventable disease and who should have more intensive surveillance, are difficult to interpret. Further research is needed to address some areas of disagreement and ambiguity. In addition, new tools must be developed to help physicians apply preventive guidelines, particularly those that require noting many patient-specific characteristics.

Canada↗
PubMed1991

Assessment of retrograde cardioplegia distribution using contrast echocardiography.

Retrograde cardioplegia has gained popularity in coronary and noncoronary cardiac operations. We have used contrast echocardiography in the open-chest canine model to compare the distribution of cardioplegia delivered antegrade in the aortic root versus retrograde through the coronary sinus, and to determine the effect of coronary occlusion on that delivery. With no coronary occlusion, antegrade cardioplegia was distributed to the entire left ventricle and septum whereas retrograde cardioplegia was distributed to the left ventricular free wall but had inconsistent delivery to the septum. Acute occlusion of the left circumflex coronary artery resulted in 57.06% +/- 9.52% of the left ventricle not being perfused by antegrade cardioplegia and occlusion of both the left circumflex and anterior descending coronary arteries caused a 65.46% +/- 18.5% reduction in perfusion by antegrade cardioplegia. Acute coronary occlusion had no effect on retrograde cardioplegia distribution. We conclude that retrograde cardioplegia is less homogeneous than antegrade cardioplegia in the intact coronary circulation but that retrograde cardioplegia preserves cardioplegia distal to acutely occluded coronary arteries. Furthermore, contrast echocardiography is a useful method of assessing myocardial perfusion and may have useful clinical applications.

Albumins↗
PubMed1991

Effects of fenoldopam on renal blood flow and systemic hemodynamics during isoflurane anesthesia.

The authors compared the systemic hemodynamic and renal vascular effects of hypotension induced by fenoldopam with those produced by the most commonly used hypotensive agent, sodium nitroprusside, in 10 dogs. Mean arterial pressure decreased 26% +/- 3% from control following infusion with fenoldopam, and 30% +/- 2% following infusion with sodium nitroprusside (these decreases were not significantly different between the groups). Renal blood flow (RBF) was preserved during fenoldopam-induced hypotension (214 +/- 16 mL/min at baseline and 197 +/- 16 mL/min after fenoldopam-induced hypotension). In contrast, RBF decreased from 223 +/- 17 mL/min to 167 +/- 12 mL/min during sodium nitroprusside-induced hypotension (P less than 0.02). The differences in RBF between the two groups occurred in spite of the fact that cardiac output and pulmonary capillary wedge pressure were kept similar between the two groups. The authors conclude that fenoldopam, a selective dopamine1 (DA1) receptor agonist, preserves blood flow to the kidney during induced hypotension. On the other hand, sodium nitroprusside is a nonselective arteriolar and venous vasodilator that redistributes blood flow away from the kidneys during induced hypotension.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1991

Assessment of myocardial perfusion during CABG surgery with two-dimensional transesophageal contrast echocardiography.

No reliable, quantifiable index of tissue perfusion is currently available to assess the efforts of coronary artery bypass graft (CABG) surgery. We used two-dimensional transesophageal contrast echocardiography with sonicated Renografin-76 microbubbles to determine the distribution of myocardial blood flow during coronary artery bypass graft surgery in 15 patients. Sonicated Renografin-76 contrast agent was injected into the aortic root of all patients after institution of cardiopulmonary bypass and application of the aortic occlusive clamp. Eight patients had contrast agent injected directly into the free proximal end of the vein-CABG anastomosis. All patients again received aortic root injections during reperfusion after anastomosis of the proximal aortovein and distal coronary artery. Echocardiographic images of the left ventricle short axis at the level of the papillary muscles were obtained in real time and analyzed retrospectively from videotape. Injection of contrast provided information about the magnitude and geometric distribution of coronary artery-vein bypass run-off and enabled identification of poorly perfused myocardial regions. When predicted myocardial perfusion patterns, based on preoperative evaluation of epicardial vessel distribution derived from coronary angiography, were compared to actual perfusion patterns assessed with intraoperative echocardiography, contrast regional myocardial perfusion patterns were predicted 84% of the time (71-97%, 95% confidence limit). Regional myocardial perfusion deficits detected after coronary bypass grafting were associated with regional wall motion abnormalities detected after separation from cardiopulmonary bypass. Our technique makes possible on-line visualization of changes in regional blood flow in the heart before, during, and after CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The automated interview versus the personal interview. Do patient responses to preoperative health questions differ?

Laboratory testing of presurgical patients has been shown to be excessive, thereby increasing costs, reducing resources for other health care uses, and increasing risks to both patients and physicians. As one step toward reducing the number of unnecessary preoperative tests ordered, we used an automated method to aid preoperative assessment of 239 patients in Chicago and in Winnipeg. The "HealthQuiz," a small hand-held device containing a computer chip and video screen, uses a decision tree to ask a minimum of 60 health-related questions (the patient's response to certain questions determines the number of questions presented). The device then generates a summary printout of patient answers, the health areas needing further attention, and the laboratory tests most likely to uncover clinically important abnormalities in that patient. HealthQuiz responses are intended to aid the physician and not to replace the personal interview. As an aid, the automated interview highlights possible problem areas for in-depth pursuit by the physician. The need for nonselective batteries of tests is eliminated because recommendations for tests are based on specific elements of a patient's history. To be effective, responses to the HealthQuiz should be the same as responses to similar questions asked by a physician. We tested that premise in this study. Patient's answers to the HealthQuiz were compared with their responses to a randomly selected set of the same questions in a personal interview. Ninety-seven percent of the response pairs were identical, and most of the 3% that differed involved changes from "not sure" replies to the HealthQuiz. Laboratory tests suggested by responses to the two methods of questioning did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Anesthesiology.

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Anesthesiology↗
PubMed1990

Preservation of renal blood flow during hypotension induced with fenoldopam in dogs.

The introduction of drugs that could induce hypotension with different pharmacological actions would be advantageous because side effects unique to a specific drug could be minimized by selecting appropriate therapy. Specific dopamine-1, (DA1) and dopamine-2 (DA2) receptor agonists are now under clinical investigation. Fenoldopam mesylate is a specific DA1 receptor agonist that lowers blood pressure by vasodilatation. The hypothesis that fenoldopam could be used to induce hypotension and preserve blood flow to the kidney was tested. Systemic aortic blood pressure and renal blood flow were measured continuously with a carotid arterial catheter and an electromagnetic flow probe respectively, in order to compare the cardiovascular and renal vascular effects of fenoldopam and sodium nitroprusside in ten dogs under halothane general anaesthesia. Mean arterial pressure was decreased 30 +/- 8 per cent from control with infusion of fenoldopam (3.4 +/- 2.0 micrograms.kg-1.min-1) and 34 +/- 4 per cent with infusion of sodium nitroprusside (5.9 micrograms.kg-1.min-1) (NS). Renal blood flow (RBF) increased during fenoldopam-induced hypotension 11 +/- 7 per cent and decreased 21 +/- 8 per cent during sodium nitroprusside-induced hypotension (P less than 0.01). Sodium nitroprusside is a non-selective arteriolar and venous vasodilator that can produce redistribution of blood flow away from the kidney during induced hypotension. Fenoldopam is a selective dopamine-1 (DA1) receptor agonist that causes vasodilatation to the kidney and other organs with DA1 receptors and preserves blood flow to the kidney during induced hypotension.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1990

Randomized comparison of recovery after propofol-nitrous oxide versus thiopentone-isoflurane-nitrous oxide anaesthesia in patients undergoing ambulatory surgery.

A randomized, prospective study was performed to compare recovery characteristics in 41 ASA physical status I-II patients scheduled for ambulatory surgery with either propofol or thiopentone-isoflurane anaesthesia. Particular attention was focused on the recovery time needed to meet discharge criteria. The propofol group received propofol 2 mg.kg-1 for induction followed by propofol infusion (6-9 mg.kg-1.h-1) 1 min after intubation. The thiopentone-isoflurane group received thiopentone 4 mg.kg-1 for induction followed by isoflurane (0.5-2%) 1 min after endotracheal intubation. Other drugs administered during or after anaesthesia were similar between the groups. The propofol group had significantly (P less than 0.05) faster clinical recovery than the isoflurane group with respect to times to response to commands, eye opening, orientation, ability to stand and void, tolerance to oral fluids, "home-readiness", and recovery of perceptual speed. Patients in the propofol group had significantly less (P less than or equal to 0.05) emesis than the patients given isoflurane. We conclude that in patients undergoing ambulatory surgery propofol infusion is preferable to thiopentone-isoflurane anaesthesia, because it may allow faster discharge home.

Adult↗