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Biomedical subjects

J W Davis

Publications and source records attributed to J W Davis.

At least 199 records · Page 11Linked to original sources
PubMed1988

Refractory vasospasm occurring in a trauma patient receiving dihydroergotamine and heparin.

A case of severe vasospasm producing ischemia associated with the administration of dihydroergotamine and heparin for prophylaxis of deep venous thrombosis is presented. We feel that the intensity of the vasospasm was related to the ergot in combination with the use of pressors and the presence of an operative site contiguous to the spastic artery. Based on our experience and a review of the world's literature, we feel that risk of vasospasm in trauma patients outweighs the potential additional benefit of this combination of drugs over heparin prophylaxis alone.

Adult↗
PubMed1988

Base deficit as a guide to volume resuscitation.

The base deficit (BD), is a potentially useful indicator of volume deficit in trauma patients. To evaluate BD as an index for fluid resuscitation, the records of 209 trauma patients with serial arterial blood gases (ABG's) were reviewed. The patients were grouped according to initial BD: mild, 2 to -5; moderate, -6 to -14; and severe, less than -15. The volume of resuscitative fluid administered, change in BD, mean arterial pressure (MAP), and presence of ongoing hemorrhage were analyzed for differences between the BD groups. The MAP decreased significantly and the volume of fluid required for resuscitation increased with increasing severity of BD group. A BD that increased (became more negative) with resuscitation was associated with ongoing hemorrhage in 65%. The data suggest that the BD is a useful guide to volume replacement in the resuscitation of trauma patients.

Adolescent↗
PubMed1988

Quantification of regional myocardial dysfunction after acute ischemic injury.

Quantification of myocardial performance after regional ischemic injury is difficult because available performance indexes are markedly dependent on concurrent load changes. To develop a more load-insensitive index of myocardial function during ischemia, eight conscious dogs were instrumented to measure left ventricular pressure with micromanometers and myocardial segment length with ultrasonic dimension transducers. Preload was varied by transient vena caval occlusion during control conditions, after 15 min of coronary occlusion, and at intervals during 24 h of reperfusion. Acute ischemia shifted the linear relationship between segmental stroke work (SW) and end-diastolic segment length (EDL) rightward, diminishing the slope and increasing the chi-intercept. Preload recruitable work area (PRWA), defined as the area under the SW-EDL curve, reflected changes in both slope and intercept. During acute ischemia, conventional performance indexes and PRWA decreased significantly and required up to 24 h of reperfusion to return to control values. Of all parameters examined, PRWA was most responsive to prolonged ischemic dysfunction after reperfusion and was insensitive to concurrent load changes. Thus PRWA provides improved precision in quantifying of myocardial dysfunction after regional ischemic injury. This parameter should be especially useful in assessing the subtle effects of acute interventions designed to modify functional recovery.

Algorithms↗
PubMed1988

Beneficial effects of endotracheal extubation on ventricular performance. Implications for early extubation after cardiac operations.

Early endotracheal extubation has been shown to be a safe postoperative management option in patients having cardiac operations. However, few objective data exist on the response of ventricular performance to early termination of controlled ventilation. Seven patients undergoing routine elective coronary artery bypass grafting or adult repair of atrial septal defect were studied after intraoperative placement of left ventricular micromanometers, left ventricular minor axis dimension crystals, and left atrial and intrapleural pressure catheters. Physiologic data were recorded intraoperatively, during controlled mandatory ventilation in the intensive care unit, and during spontaneous respiration immediately after extubation. Extubation to spontaneous breathing was associated with a significant decline in intrapleural pressure and significant increases in left ventricular end-diastolic diameter, ejection diameter shortening, stroke work, and cardiac output. The augmented left ventricular diastolic filling seemed to result from the fall in intrapleural pressure and perhaps from normalization of right ventricular afterload. The preload recruitable stroke work relationship showed that myocardial contractility remained constant after extubation, and ventricular function improved primarily because of increased preload associated with shifting of the capacitance blood volume toward the chest. Thus endotracheal extubation enhances cardiac performance after uncomplicated cardiac surgical procedures, and by this mechanism early extubation may be clinically beneficial as a routine adjunct to postoperative care.

Cardiac Output↗
PubMed1987

Effect of a maxillary glossectomy prosthesis on articulation and swallowing.

Swallowing was found to be substantially improved with the prosthesis. Less aspiration, less time necessary to complete the swallow, and greater variation in food consistency tolerated were all positive results of the prosthesis. In addition, videofluoroscopic studies of tongue movements during speech revealed that tip-alveolar /t-d/ and back-velar /k-g/ productions were more normal with the prosthesis. With the prosthesis, the understandibility of /t/ and /d/ was improved 20% and that of /k/ and /g/, 33%. It is clear that compromises must be effected in prosthesis design to facilitate improvement in both speech and swallowing. A large prosthetic mass in the oral cavity can also negatively change speech resonance. These issues are being investigated, as are acoustic and perceptual studies of speech articulation. Future research should address whether a combination of maxillary and mandibular prostheses would result in better speech and swallowing function. A mandibular prosthesis could replace missing teeth and alveolar contour that might influence speech and swallowing. A mandibular prosthesis might also allow construction of a smaller maxillary glossectomy prosthesis to interact with the mandibular prosthesis.

Articulation Disorders↗
PubMed1987

An integrated oncology course for second year medical students.

A required course for second year medical students explores an integrated approach to the patient with cancer. Lectures detail the role of each medical discipline in the management of cancer. Panel discussions illustrate the cooperation necessary between clinical specialties in the diagnosis and treatment of these diseases. A small group session provides a problem-solving exercise around a patient with cancer, and laboratory sessions present the opportunity for students to receive hands-on experience in detecting tumor masses in anatomical models as well as the opportunity for students to test their stools for occult blood. Evaluation of the course has shown that students increase significantly their knowledge about cancer, that "practice-effect" is not a factor from pre- to post-test, and that although students improve in their capacity to solve problems they are less proficient in this than retention of facts. Student surveys have indicated generally good acceptance of most aspects of the course.

Curriculum↗
PubMed1987

Second cancers in patients with chronic lymphocytic leukemia.

Among 419 persons diagnosed as having chronic lymphocytic leukemia (CLL) in western Washington State between 1974 and 1983 and followed through January 1985, 9 subsequently developed other lymphoid cancers and 48 developed nonlymphoid cancers. Only 2 lymphoid and 21 nonlymphoid cancers were expected based on the rates of the western Washington population as a whole. Lung cancer accounted for about one-third of the excess rate observed. Three of the nonlymphoid tumors that occurred in the patients with CLL were classified as malignant fibrous histiocytomas, which represents an exceptionally high relative incidence for this histologic type. The excess risk of nonlymphoid cancers was present in both sexes, across all age categories, and in every length-of-follow-up interval. These results, taken together with those obtained from earlier investigations, suggest that persons with CLL are at increased risk of developing a second tumor, particularly in the lung. The reasons for this increased risk remain to be elucidated.

Adult↗
PubMed1987

Inorganic pyrophosphatase activity in cell-free extracts of Ureaplasma urealyticum.

Cell-free extracts of Ureaplasma urealyticum strains Pi and T960 (CX8) (serovars 6 and 8, respectively) metabolized inorganic pyrophosphate (PPi). The inorganic pyrophosphatase (PPase) activity was greatest with Mg2+ as cofactor, but Mn2+ acted as a poor substitute. The PPases of the two serovars differed electrophoretically. Although the highest PPase activity was obtained using PPi as substrate, the enzyme could also utilize to a lesser degree both tripolyphosphate and trimetaphosphate. No activity was observed against beta-glycerophosphate, naphthyl phosphates, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, thiamin pyrophosphate, phosphoribosylpyrophosphate, ADP or ATP. Acid- and alkaline-phosphatase activities were observed with naphthyl phosphates as substrates, but they did not have the same electrophoretic mobility on gels as the PPase activity. U. urealyticum PPase was inhibited by oxidized glutathione, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, phenylglyoxal, p-chloromercuribenzoic acid, Mn2+, Zn2+ and Ca2+. Neither reduced glutathione, L-cysteine nor Co2+ enhanced activity. PPi can act as a substrate or regulator of certain metabolic reactions, and PPi metabolism can function in bacterial bioenergetics; its role in ureaplasmas is presently unclear.

Cations, Divalent↗
PubMed1987

Lack of effect of aspirin on cigarette smoke-induced increase in circulating endothelial cells.

A random-order, double-blind crossover study was done to compare the effects of placebo and two different doses of aspirin on the endothelial cell count of venous blood before and after smoking. Each of 17 male habitual smokers with coronary artery disease smoked two cigarettes during each of three 20-min periods separated by 2 weeks. Each patient was asked to take a tablet containing 150 mg of aspirin, 300 mg of aspirin or a placebo 12 h before each experimental smoking period and to abstain from smoking in the interim. Endothelial cell counts were determined by means of differential centrifugation and phase-contrast microscopy and nicotine by gas chromatography. After ingestion of placebo, the mean endothelial cell counts (+/- SD) were 2.7 +/- 0.8 and 4.5 +/- 0.9 per counting chamber before and after smoking respectively (p less than 0.001). Endothelial cell counts and plasma nicotine concentrations were not significantly correlated. Neither the mean presmoking values nor smoking-induced changes in either variable were affected either dose of aspirin. The data suggest that smoking caused acute endothelial cell desquamation which was not prevented by aspirin.

Adult↗
PubMed1987

The end-systolic pressure-volume relationship in conscious dogs.

The end-systolic pressure-volume relationship (ESPVR) has been shown to be an afterload-insensitive descriptor of ventricular inotropic state in the isolated heart. The purpose of this study was to examine the effects of changes in afterload, heart rate, intravascular volume, autonomic tone, and inotropic state on the ESPVR in conscious dogs. In 30 dogs, left ventricular and pleural pressures were measured with micromanometers, and left ventricular volume was assessed with global ultrasonic crystals. The ESPVR was obtained during vena caval occlusions in each dog during pharmacologic afterload interventions at control and after autonomic blockade. Analysis of variance techniques were used to compare the slopes (Emax) and intercepts (Vd) of ESPVR regression lines in a given study. All estimates of the ESPVR in conscious dogs involved large extrapolations to obtain estimates of Vd. Repeat determinations of Emax at control in the unblocked state were significantly different in six of eight dogs (p less than .05). After autonomic blockade, these differences were significant in only one of eight dogs. Changes in heart rate and volume loading had minimal effects on the ESPVR. In the absence of autonomic blockade, increases in inotropic state with either calcium or dobutamine tended to cause parallel shifts in the ESPVR. After autonomic blockade, Emax increased with augmentation of inotropic state, while Vd was unchanged. ESPVRs obtained at different afterloads showed statistically significant differences in Emax and in Vd in 12 of 14 dogs. However, no statistically significant relationship of Emax to afterload was observed. Thus, the ESPVR is probably valid in conscious dogs, but measurement with an intact cardiovascular system is hampered by statistically significant variability in Emax and Vd with changes in afterload. Baseline variability is magnified by the autonomic nervous system, probably mediated through sympathetic reflexes.

Analysis of Variance↗
PubMed1987

Sequence of mitral valve motion and transmitral blood flow during manual cardiopulmonary resuscitation in dogs.

According to the thoracic pump model of cardiopulmonary resuscitation (CPR), the heart serves as a passive conduit for blood flow from the pulmonary to the systemic vasculature, necessitating an open mitral valve and anterograde transmitral blood flow during chest compression. To assess the applicability of this model to manual CPR techniques, two-dimensional echocardiograms were recorded from the right chest wall and/or the esophagus in nine dogs (18 to 26 kg) during manual CPR. The aortic valve opened with chest compression and closed with release, while the pulmonary and tricuspid valve leaflets closed with compression and opened during release. The mitral valve remained open during ventilation alone and during abdominal compressions. With the onset of brief, high-velocity (high-impulse) chest compressions, the mitral valve closed rapidly and the left ventricle was deformed, whether compressions were applied to the sternum or the left mid-chest wall. The mitral valve reopened with release of each compression. Left atrial echocardiographic contrast injections confirmed the absence of anterograde transmitral blood flow during high-impulse compression and its presence during release. Failure of mitral leaflet approximation during chest compression was observed only when a very low-velocity, prolonged (low-impulse) compression technique was used, or when regions that did not directly overlie the heart were compressed. Consistent with these observations, simultaneous recordings of the left ventricular and left atrial pressures during high-impulse sternal compressions in five dogs (19 to 25 kg) demonstrated peak and mean left ventriculoatrial pressure gradients of 38.5 +/- 4.0 and 13.5 +/- 2.9 mm Hg, respectively, and these pressure gradients declined with less impulsive compressions. The observations made during all but low-impulse chest compressions are inconsistent with the thoracic pump model, and support direct cardiac compression as the primary mechanism of forward blood flow with more impulsive manual chest compression techniques.

Animals↗
PubMed1987

Relation between reversal of diastolic creep and recovery of systolic function after ischemic myocardial injury in conscious dogs.

Although prolonged functional abnormalities after transient myocardial ischemia have been well described, the interrelationship between postischemic systolic and diastolic alterations remains controversial. Therefore, 24 chronically instrumented conscious dogs were studied with left ventricular and pleural micromanometers, ultrasonic dimension transducers in the left anterior descending (LAD) coronary distribution, and vena caval and coronary artery occluders. The LAD was occluded for 15 minutes and reperfused for 24 hours while vena caval occlusions were performed at intervals to measure myocardial segment length at 0 mm Hg transmural diastolic left ventricular pressure (L0). Coronary occlusion produced an immediate fall in systolic function as assessed by ejection shortening and stroke work and also induced a 16 +/- 4% increase in L0, which was termed diastolic creep. Throughout reperfusion, reversal of diastolic abnormalities correlated strongly with recovery of segmental shortening and stroke work (p less than 0.001). Correlation between systolic dysfunction and diastolic creep was also observed during alteration of inotropic state by dopamine, during initial reperfusion hyperfunction, and during pharmacologic manipulation of afterload. In 5 additional dog hearts fixed in diastole by rapid glutaraldehyde infusion after coronary occlusion, myocardial creep measured by the segment length transducers paralleled sarcomere elongation measured by electron microscopy. Thus, the direct correlation between diastolic creep and systolic dysfunction throughout reperfusion and during hemodynamic alterations suggests that diastolic properties of postischemic myocardium may not be entirely passive and that systolic and diastolic dysfunction induced by ischemia may have a common basis at the cellular level.

Animals↗
PubMed1986

Cholelithiasis in sickle cell anemia: surgical considerations.

Gallstones are frequently found in patients with sickle cell anemia. The differentiation between acute calculous biliary tract disease and sickle cell crisis can be difficult and should be based on the clinical presentation, comparison with previous episodes of abdominal pain, and judicious use of hepatobiliary radionuclide scanning. Emergency cholecystectomy is associated with a high morbidity and should be avoided if possible. Elective cholecystectomy is associated with a lower but still significant risk of complications. We believe patients with sickle cell anemia and symptomatic cholelithiasis should have elective cholecystectomy. Careful management is essential to minimize the danger of postoperative complications.

Acute Disease↗
PubMed1986

Smoking-induced changes in endothelium and platelets are not affected by hydroxyethylrutosides.

A random-order, double-blind crossover study was carried out to compare the effects of placebo and hydroxyethylrutosides on the endothelial cell count, platelet aggregate ratio and plasma concentrations of beta-thromboglobulin and platelet factor 4 in venous blood before and after smoking. Each of 24 male habitual smokers and 22 male non-smokers smoked two cigarettes during each of two 20 min periods separated by 1 week. The subjects were asked to take 600 mg of o-(beta-hydroxyethyl)-rutosides (Venoruton) or a placebo four times before each experimental smoking period and to abstain from smoking for 12 h before each period. Blood was obtained just before and after experimental smoking. The mean endothelial cell count and beta-thromboglobulin concentration increased and platelet aggregate ratio decreased to a statistically significant extent after taking placebo or rutosides while the platelet factor 4 concentration did not change significantly on either occasion. Plasma nicotine concentrations were not significantly correlated with the other variables after smoking. Neither the mean presmoking values nor smoking-induced changes in any variable were significantly affected by rutosides. The data suggest that smoking caused acute endothelial cell desquamation and enhanced platelet function which were not prevented by rutosides.

Adult↗
PubMed1986

Vaso-occlusive crisis episodes in sickle cell disease.

Seventeen adult males and females with Hb-SS, Hb-SC (1) and Hb-S Thal (1) hemoglobinopathies were continuously studied for 3 years. Various hematological and biochemical parameters were measured in the venous blood of the subjects for blood gases, CBC profile, blood chemistry (SMA-18), fibrinogen, alpha-HBD and myoglobin levels, percent sickling, blood viscosity, oxygen affinity of whole blood, osmofragility of red blood cells and calcium and zinc contents in plasma and in RBC. The results were compared between those subjects who encountered more frequent vaso-occlusive crisis episodes (frequent sicklers) and those with fewer crisis episodes (infrequent sicklers), along with parameters between crisis and non-crisis states of frequent sicklers. Our studies showed that percent sickling, P50 for O2, CBC profile, PO2, serum calcium, ALP, LDH, alpha-HBD level, zinc and calcium levels in plasma and in RBC varied between crisis and non-crisis states of frequent sicklers and also between frequent sicklers and infrequent sicklers. A logical explanation of such variations may help in understanding the etiology of vaso-occlusive crisis episodes in sickle cell disease.

Adult↗
PubMed1986

The influence of manual chest compression rate on hemodynamic support during cardiac arrest: high-impulse cardiopulmonary resuscitation.

Considerable effort has been expended in recent years by a number of laboratories to improve methods of cardiopulmonary resuscitation. This article briefly summarizes 5 years of investigation by our group on hemodynamic support during external cardiac massage. In most studies, long-term canine preparations were used, and implanted transducers allowed precise hemodynamic measurements. Although cardiac output was depressed with all CPR methods, manual chest compressions of high velocity, moderate force, and brief duration at a rate of 120/min seemed to optimize systemic and coronary blood flow. This method was termed high-impulse CPR. High-impulse techniques now have been applied extensively in the clinical setting, and preliminary observations also support their efficacy in man. Based on this experience, it is suggested that the American Heart Association guidelines be changed to recommend a manual chest compression rate of 120/min during closed-chest cardiac massage.

Animals↗
PubMed1985

Combined functional oral rehabilitation after radical cancer surgery.

Formerly, patients requiring extensive reconstruction of the oral cavity and oropharynx after radical, ablative oncologic surgery faced the unhappy prospect of lengthy, multistaged repair to enjoy acceptable cosmesis and a functional oral cavity. The advent of the pectoralis major myocutaneous flap has made soft-tissue, single-stage closure of large oral cavity and oropharyngeal defects a reality. Unfortunately and frequently, restoration of mucocutaneous continuity of the mouth does not result in acceptable function. Advances in the materials and design of prostheses suggested the combination of myocutaneous flap reconstruction and functional, prosthetic restoration as a method of returning the patient with head and neck cancer to a state of acceptable function and appearance soon after major resection.

Adult↗