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Biomedical subjects

J F Richeson

Publications and source records attributed to J F Richeson.

12 recordsLinked to original sources
PubMed1992

The association between interdisciplinary collaboration and patient outcomes in a medical intensive care unit.

We prospectively studied the relationship between interdisciplinary collaboration and patient outcomes in the medical intensive care unit (MICU) using nurses' and residents' reports of amount of collaboration involved in making decisions about transferring patients from the MICU to a unit with a less intense level of care. Either readmission to the MICU or death was considered a negative patient outcome. Nurses' reports of collaboration were significantly (p = 0.02) and positively associated with patient outcome, controlling for severity of illness. Patient predicted risk of negative outcome decreased from 16%, when the nurse reported no collaboration in decision making, to 5% when the process was fully collaborative. There was an interaction of collaboration with availability of alternative choices in the transfer decision-making situation. When alternatives were available, collaboration was more strongly associated with patient outcome. There was no significant relationship between residents' reports of collaboration and patient outcomes. The correlation between amount of collaboration reported by nurses and residents about the same decisions was quite low (r = 0.10).

Adult↗
PubMed1990

Unstable angina pectoris.

The pathophysiology of unstable angina has been better elucidated in the past five years and has led to more rational therapy. Coronary arteries in patients with unstable angina have atherosclerotic plaques which are often complex and are the site of platelet activation and fibrin deposition. Nitrates, one of the oldest therapies, are efficacious and act not only by dilating coronary vessels but by reducing preload and afterload. Beta blockers have a salutary effect by decreasing myocardial oxygen demand. Calcium channel blockers attenuate smooth muscle contraction and thereby act to decrease coronary artery spasm. Beta blockers and calcium channel blockers are equally efficacious in unstable angina. The antiplatelet agent, aspirin, has been shown to reduce fatal or non-fatal myocardial infarction and probably overall mortality. The use of heparin acutely for unstable angina has been demonstrated to decrease refractory angina and myocardial infarction, and acutely is probably better than aspirin. For patients with reduced ejection fractions (0.30-0.49), a prospective randomized trial has shown that coronary artery bypass graft surgery offers an improved three-year survival compared with medical therapy; however, surgery does not prevent myocardial infarction. Percutaneous transluminal coronary angioplasty may be a reasonable therapeutic alternative for some patients with single-vessel disease who are refractory to medical therapy but there are as yet no controlled trials of this question. To date a clinical benefit from thrombolytic therapy has not been demonstrated.

Angina, Unstable↗
PubMed1990

Comparison of phenylephrine bolus and infusion methods in baroreflex measurements.

Phenylephrine (PE) bolus and infusion methods have both been used to measure baroreflex sensitivity in humans. To determine whether the two methods produce the same values of baroreceptor sensitivity, we administered intravenous PE by both bolus injection and graded infusion methods to 17 normal subjects. Baroreflex sensitivity was determined from the slope of the linear relationship between the cardiac cycle length (R-R interval) and systolic arterial pressure. Both methods produced similar peak increases in arterial pressure and reproducible results of baroreflex sensitivity in the same subjects, but baroreflex slopes measured by the infusion method (9.9 +/- 0.7 ms/mmHg) were significantly lower than those measured by the bolus method (22.5 +/- 1.8 ms/mmHg, P less than 0.0001). Pretreatment with atropine abolished the heart rate response to PE given by both methods, whereas plasma catecholamines were affected by neither method of PE administration. Naloxone pretreatment exaggerated the pressor response to PE and increased plasma beta-endorphin response to PE infusion but had no effect on baroreflex sensitivity. Thus our results indicate that 1) activation of the baroreflex by the PE bolus and infusion methods, although reproducible, is not equivalent, 2) baroreflex-induced heart rate response to a gradual increase in pressure is less than that seen with a rapid rise, 3) in both methods, heart rate response is mediated by the vagus nerves, and 4) neither the sympathetic nervous system nor the endogenous opiate system has a significant role in mediating the baroreflex control of heart rate to a hypertensive stimulus in normal subjects.

Adult↗
PubMed1989

Sequential topographical portrayal of myocardial blood flow.

Methods to portray myocardial blood flow in a two-dimensional continuum are advantageous in that they allow blood flow history to be overlaid on histological or histochemical descriptions of the consequences of ischemia. We describe here autoradiographic methods that allow such portrayals at three separate times during the evolution of ischemic injury. A computer-based image-analysis system was used to derive such flow maps by taking advantage of the physical characteristics of radioactive isotopes.

Animals↗
PubMed1989

Origin of the giant R wave in acute transmural myocardial infarction in the pig.

An increase in R wave amplitude and a diminution of S wave amplitude, together with ST segment elevation, have been described as very early electrocardiographic changes during clinical and experimental acute myocardial infarction. The genesis of these QRS changes remains unclear. We assessed the quantitative relationship between the local conduction delay and the formation of the giant R wave, using multiple epicardial, intramural unipolar, and bipolar electrodes in 30 open-chest pigs with acute transmural myocardial ischemia. Blood pressure, heart rate, serum electrolytes, hematocrit, and left ventricular size remained constant, or varied insignificantly throughout the experiments. In nonischemic pigs, transmural left ventricular activation occurred nearly simultaneously, and the activation time was not correlated with the net QRS potential. During acute ischemia, a giant R wave developed at all of the electrodes located within the ischemia region; R wave amplitude began to increase 1 min after coronary artery ligation (p less than 0.05), compared to control amplitude and peaked at 8 min (p less than 0.0001). The degree of conduction delay at a given site was correlated linearly with the local R wave amplitude (average of correlation coefficients +/- SEM at 1 min, r = 0.64 +/- 0.08, and at 8 min, r = 0.81 +/- 0.06). The magnitude of the R wave potential and the conduction delay were greater in regions deep inside the ischemic zone than in the border and normal areas (p less than 0.0001), and were greater in subepicardial than in subendocardial areas (p less than 0.05). In summary, during transmural ischemia, conduction is markedly slowed, and an orderly and discrete wavefront advances toward the center of the ischemic zone from lateral and subendocardial areas. When depolarization is complete in the rest of the heart, this slow activation front becomes temporally isolated and its progression gives rise to a giant R wave, which appears in recordings from overlying electrodes.

Animals↗
PubMed1988

The safety and efficacy of a controlled low-energy ('very-low-calorie') diet in the treatment of non-insulin-dependent diabetes and obesity.

We evaluated the safety and efficacy of a highly supplemented controlled low-energy (1764 kJ [420 kcal]) diet in the treatment of non-insulin-dependent diabetes and obesity. Six obese, diabetic women ranging from 143% to 297% of ideal body weight were studied in a metabolic ward for 48 days. The subjects ingested a weight-maintenance diet during an eight-day control period followed by 40 days of an experimental diet containing 1764 kJ (420 kcal) of a mixture of protein (43% of energy intake), carbohydrates (51%), and fat (6%), supplemented with minerals, trace elements, and vitamins. The subjects were monitored for balances of nitrogen and minerals, as well as for the appearance of cardiac arrhythmias by 24-hour electrocardiographic recordings. Weight loss was rapid and sustained and averaged 10.1% +/- 0.8% over 40 days. Fasting plasma glucose levels declined from 16.2 +/- 1.9 mmol/L (293 +/- 36 mg/dL) to 6.9 +/- 0.8 mmol/L (126 +/- 16 mg/dL) by day 35. Similarly, hemoglobin A1c levels fell from 0.11 +/- 0.009 (11.2% +/- 0.9%) to 0.8 +/- 0.001 (8.2% +/- 1.1%). Urinary C-peptide levels declined from 62.2 +/- 15.6 nmol/48 h to 20.0 +/- 5.9 nmol/48 h by days 39 to 40 and paralleled the decline in plasma glucose values, the majority of which occurred in the first seven days. Concentrations of serum cholesterol and triglycerides decreased. Balances for nitrogen, potassium, and magnesium were negative at -1.7 g/24 h, -2.2 mEq/24 h, and -2.9 mg/dL, respectively. Blood pressure decreased without orthostasis. Resting metabolic rate fell a mean of 18% but remained within normal limits. Triiodothyronine levels also declined. Twenty-four-hour ambulatory electrocardiographic readings disclosed no significant bradyarrhythmia or tachyarrhythmia for any patient. These studies, based on a limited number of subjects, demonstrate that a highly supplemented controlled low-energy diet is a safe and efficacious treatment for diabetes and obesity, leading to significant decreases in weight, blood pressure, and levels of plasma glucose and plasma lipids. Such diets may be the optimal initial treatment of moderate to markedly obese patients with non-insulin-dependent diabetes.

Adult↗
PubMed1987

Hospital and long-term survival of patients with acute pulmonary edema associated with coronary artery disease.

Cardiogenic acute pulmonary edema (APE) associated with coronary artery disease was diagnosed in 44 patients admitted over a 1-year period to a general university hospital. The patients' clinical characteristics at presentation were variable. Acute myocardial infarction (AMI) was present in 26 patients (59%). The hospital mortality rate was 46% (12 of 26 patients) in the presence of AMI and 6% (1 of 18) in its absence (p = 0.006). Long-term follow-up of all hospital survivors revealed that 8 of 30 (27%) had died at 1 year and that 21 of 30 patients (70%) had died at 6 years. However, there was no significant difference in subsequent survival between the AMI and non-AMI groups. A history of congestive heart failure was selected as the most important predictor of increased mortality risk by univariate analysis of the clinical characteristics of the hospital survivors (p = 0.02). The mortality rate at 6 years of follow-up was 85% (17 of 20 patients) in the presence of a history of congestive heart failure and 40% (6 of 10) in its absence.

Acute Disease↗
PubMed1978

A solid angle analysis of the epicardial ischemic TQ-ST deflection in the pig. A theoretical and experimental study.

The solid angle theory has long been applied to the interpretation of the ECG; however, quantitative evaluation of its applicability has been minimal. We applied solid angle analysis to the interpretation of the TQ-ST deflection during acute ischemia. Five anesthetized pigs were studied 1--3 hours after coronary occlusion. Multiple unipolar tracings were recorded from precisely determined positions on the epicardium overlying the ischemic and normal zones. The geometry of the hearts and ischemic zones was preserved, the margins of ischemia being defined as the outer border of Thioflavin S nonfluorescence. Wax replicas of the hearts with ischemic zones removed were constructed. Solid angles subtended at electrode positions on the replicas were calculated. A linear relationship (r = 0.84 - 0.97, P less than 0.001) was shown to exist between the observed TQ-ST deflection and the calculated solid angle. A small but patterned deviation from exact fit of the TQ-ST deflection with the calculated solid angle led us to investigate the possibility that dipole moment strength (phi) is not confined to the ischemic margins. Computations using idealized heart models with ischemic zones cylindrical and transmural in shape allowed us to distribute phi arbitrarily within the ischemic zone, comparing this predicted pattern of TQ-ST deflection with that observed experimentally. The experimental data appear most consistent with the condition in which phi is distributed over a 1-cm border region during the first several hours of ischemia. We conclude that the solid angle theory provides a rational basis for interpretation of the ischemic TQ-ST deflection; however, phi may be distributed over a marginal zone.

Acute Disease↗