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Biomedical subjects

J E Mahaffey

Publications and source records attributed to J E Mahaffey.

15 recordsLinked to original sources
PubMed1978

Osteomalacia and disorders of vitamin D metabolism.

A rapidly growing understanding of the biochemical and physiological processes that underlie the metabolism of vitamin D has provided new insights into the pathogenesis of oestomalacia. Many of the vitamin D--resistant osteomalacia syndromes can now be explained on the basis of defects in the metabolic conversion of vitamin D to the biologically active dihydroxylated metabolite 1,25(OH)2D and perhaps, in some instances, to impairement of the actions of 1,25(OH)2D on target tissues. The availability of this new information has made possible the synthesis of 1-hydroxylated forms of the vitamin for therapeutic use in states of vitamin D resistance. Although many questions regarding the pathogenesis and most effective approaches in the management of osteomalacia remain unanswered, considerable progress has been made in this direction as a result of continued research on the subject.

Bone Neoplasms↗
PubMed1977

Nephrogenous cyclic adenosine monophosphate as a parathyroid function test.

Nephrogenous cyclic AMP (NcAMP), total cyclic AMP excretion (UcAMP), and plasma immunoreactive parathyroid hormone (iPTH), determined with a multivalent antiserum, were prospectively measured in 55 control subjects, 57 patients with primary hyperparathyroidism (1 degrees HPT), and 10 patients with chronic hypoparathyroidism. In the group with 1 degrees HPT, NcAMP was elevated in 52 patients (91%), and similar elevations were noted in subgroups of 26 patients with mild (serum calcium </=10.7 mg/dl) or intermittent hypercalcemia, 19 patients with mild renal insufficiency (mean glomerular filtration rate, 64 ml/min), and 10 patients with moderate renal insufficiency (mean glomerular filtration rate, 43 ml/min). Plasma iPTH was increased in 41 patients (73%). The development of a parametric expression for UcAMP was found to be critically important in the clinical interpretation of results for total cAMP excretion. Because of renal impairment in a large number of patients, the absolute excretion rate of cAMP correlated poorly with the hyperparathyroid state. Expressed as a function of creatinine excretion, UcAMP was elevated in 81% of patients with 1 degrees HPT, but the nonparametric nature of the expression led to a number of interpretive difficulties. The expression of cAMP excretion as a function of glomerular filtration rate was developed on the basis of the unique features of cAMP clearance in man, and this expression, which provided elevated values in 51 (89%) of the patients with 1 degrees HPT, avoided entirely the inadequacies of alternative expressions. Results for NcAMP and UcAMP in nonazotemic and azotemic patients with hypoparathyroidism confirmed the validity of the measurements and the expressions employed.

Adolescent↗
PubMedDate not supplied

Influence of pH and hypoxia on the success of defibrillation.

Clinical impressions about the problem of defibrillation during states of acid-base imbalance and hypoxia have been influenced by studies involving the effect of these derangements on the ventricular fibrillation threshold. Based on body weight, energy requirements for defibrillation in normal dogs were compared to requirements in dogs subjected to commonly encountered acid-base disturbances and severe hypoxemia. No significant differences were found. Seventy-five percent of all animals in the study were electrically converted with low-to-moderate levels of energy. The incidence of spontaneous resumption of circulation following defibrillation was lowest in animals subjected to metabolic acidosis and hypoxia. The results suggest that pH and blood gas alterations, previously shown to influence the normal ventricular fibrillation threshold, do not significantly affect the normal defibrillation threshold.

Acid-Base Imbalance↗
PubMedDate not supplied

Effects of intraoperative PEEP on postoperative arterial oxygenation.

Previous studies have suggested that early postoperative hypozemia may be due to a reduction of functional residual capacity (FRC) during anesthesia and surgery. Positive end-expiratory pressure (PEEP) has been recommended as a means of maintaining FRC and improving arterial oxygenation. Fifteen selected patients undergoing peripheral surgical procedures were anesthetized with one of three types of ventilatory patterns: (1) spontaneous respiration; (2) controlled ventilation; and (3) controlled ventilation with 10 cm. of water PEEP. Pao2 were sampled at selected preoperative, intraoperative, and postoperative periods. Patients receiving PEEP maintained the highest mean Pao2 intraoperatively. However, the beneficial effect of intraoperative PEEP was not sustained in the recovery room, where all patients experienced the same degree of arterial hypoxemia.

Adult↗
PubMedDate not supplied

Crdiovascular effects of lidocaine during acid-base imbalance.

Although lidocaine HCl is often given to critically ill patients with ventricular tachyarrhythmias, it use is not without hazard. To investigate whether acid-base disturbances and their subsequent effects on molecular ioization influence cardiovascular (CV) response to lidocaine, dogs in normal acid-base balance, metabolic acidosis, respiratory acidosis, and respiratory alkalosis were given 2 or 4 mg/kg lidocaine IV. Heart rate (HR), PR and QT intervals, MAP, LVEDP, LV dp/dt, and LV dp/dt divided by CPIP were measured at intervals. In all groups a slight increase in mean HR occurred after 2 mg/kg. Generally, myocardial contractile force was depressed in direct proportion to dose. Essentially, the CV response to lidocaine was not altered by any clinically remarkable degree by pH disturbances. Responses differing from those observed during normal acid-base conditions could not be significantly correlated with changes in pH or PaCO2. Results suggest that, in the intact animal, the CV effects of lidocaine, administered in therapeutic doses, are not appreciably influenced by clinically encountered states of acid-base imbalance.

Acid-Base Imbalance↗
PubMedDate not supplied

Anesthetic management of an intracranial arteriovenous malformation in infancy.

The prevention and control of massive bleeding has always been a problem in neurosurgical procedures, particularly in patients with arteriovenous malformations, intracranial aneurysms, and large vascular tumors. During the past 25 years, new technics have reduced the risk of hemorrhage; however, these have been most suitable for adult patients. Vascular intracranial lesions during infancy present even more complex problems. This is a report of the anesthetic management of a 7-month-old infant with an aneurysm of the v cerebri magna (great vein of Galen). Anesthetic management consisted of (1) halothane-N2O-O2 general endotracheal anesthesia, (2) surface-induced profound hypothermia, and (3) low-flow extracorporeal circulation. Phenothiazine premedication was used with halothane anesthesia to antagonize reflex vasoconstriction during hypothermia, hypothermia and low cardiac output to lessen the possibility of hemorrhage, aneurysmal rupture, and neurologic damage, and surface-induced hypothermia because it provides better core perfusion than central cooling. This technic allowed a successful outcome in an otherwise high-risk procedure.

Anesthesia, Inhalation↗