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Biomedical subjects

R H Cox

Publications and source records attributed to R H Cox.

At least 127 records · Page 7Linked to original sources
PubMed1980

Carotid sinus control of pulsatile hemodynamics in halothane-anesthetized dogs.

The open-loop characteristics of the carotid sinus baroreceptor reflex control of pulsatile arterial pressure-flow relations were studied in halothane-anesthetized dogs. Pressures and flows were measured in the ascending aorta, the celiac, mesenteric, renal, and iliac arteries and were used to compute values of regional vascular impedance and hydraulic power. The carotid sinuses were bilaterally isolated and perfused under conditions of controlled mean pressure with a constant sinusoidal component. Measurements were made with the vagi intact and after bilateral vagotomy. Maximum values of open-loop gain averaged -0.78 +/- 0.08 before and -1.42 +/- 0.20 after vagotomy. Vagotomy produced significant increases in the variation of all hemodynamic variables with carotid sinus pressure that were nonuniformly affected in the various regional vascular beds. Aortic and regional vascular impedance showed significant variations with carotid sinus pressure that were augmented by vagotomy. Aortic impedance exhibited a minimum at the normal set point. These results indicate that a) carotid sinus baroreflexes are well preserved with halothane anesthesia, b) thoracic baroreceptor-mediated reflexes exert significant hemodynamic effects on systemic hemodynamics around normal set point values of arterial pressure, c) systemic baroreceptors exert control over large as well as small vessel properties, and d) the baroreceptor-mediated reflexes produce significant influences on hydraulic power and its components.

Anesthesia↗
PubMed1980

Effects of anesthesia on carotid sinus reflex control of arterial hemodynamics in the dog.

The detailed characteristics of the carotid sinus reflex control of regional pressure-flow relations were compared in dogs anesthetized with chloralose, pentobarbital, or halothane. The carotid sinuses were isolated and perfused under conditions of controlled pulsatile pressure. Pressure and flow were measured in the ascending aorta and the celiac, mesenteric, renal, and iliac artery. Mean arterial pressure and peripheral resistance were highest under chloralose and lowest under halothane. For cardiac output this relation was reversed. Set point values of reflex gain and overall range of control were similar under chloralose and halothane and lowest under pentobarbital. These results were found both before and after bilateral cervical vagotomy. Operating point values of regional resistance were generally largest with chloralose and smallest with halothane. Operating point sensitivities of regional resistances were generally smallest under pentobarbital and similar under chloralose and halothane. Vagotomy was associated with increases in set point values of mean arterial pressure, set point gain, and overall range of control under all three anesthetics. With chloralose as a reference, halothane does not depress cardiovascular reflex mechanisms. Carotid sinus reflexes under halothane were as sensitive and well maintained as they were under chloralose. These reflexes were significantly depressed under pentobarbital compared with chloralose.

Anesthetics↗
PubMed1980

Alterations in carotid sinus reflex control of arterial hemodynamics associated with experimental hyperlipemia in the racing greyhound.

We administered a high cholesterol diet to racing greyhounds and studied its effects on the characteristics of carotid sinus reflex control of arterial pressure-flow relations. Dogs were anesthetized with halothane, and pressure and flow were simultaneously measured in the ascending aorta and the celiac, mesenteric, renal, and iliac arteries. The carotid sinuses were isolated bilaterally and perfused with a physiological salt solution under controlled conditions. The variation of regional pressure-flow relations and regional vascular resistance was assessed as a function of mean carotid sinus pressure (MCSP) with the vagi bilaterally sectioned to eliminate aortic arch afferents. Some differences were found in set point (i.e., MCSP = mean arterial pressure) values of hemodynamic variables; cardiac output and renal and iliac flows were significantly lower. Control and set point values of mean arterial pressure were not significantly different between the two groups. The variation of every hemodynamic variable with the exception of heart rate with carotid sinus pressure was attenuated markedly in the diet-treated dogs. Substantial lesions were found involving the entire carotid sinus region of every diet-fed animal. These results suggest that pathological alterations in the carotid sinus region are at least in part responsible for a reduction in the sensitivity of carotid sinus baroreflexes associated with atherosclerosis.

Animals↗
PubMed1980

Primary monomorphic adenoma of the middle ear.

The benign, monomorphic adenoma, derived from the respiratory epithelium of the middle ear, is a well circumscribed, greyish, avascular tumor. Its histology--documented by light and electron micrographs contained in this report--supports a distinct entity and pathogenesis apart from the malignant adenocarcinoma. Utilizing two case reports, this compendium emphasizes the clinical presentations, as well as radiographic and audiometrical characteristics, of the tumor. The first case represents the typical tumor with conductive hearing loss. The second case is the first reported facial paralysis associated with hemorrhagic infarction of an adenoma which was reversible by surgical resection of the tumor. Based on the histology and four year postoperative follow-up, the authors conclude the adenoma may be effectively managed by surgical resection.

Adenoma↗
PubMed1980

An approach to the anesthetic requirements for a chronic animal preparation.

The general anesthetic requirements for the preparation of a chronic experimental animal are discussed with respect to the implantation of an electromagnetic flow probe around the ascending aorta of the dog. After preanesthetic management and induction, several techniques for the maintenance of anesthesia are briefly considered. A technique is emphasized that combines a light general anesthetic with a regional nerve block and best fulfills the general anesthetic requirements.

Anesthesia, General↗
PubMed1979

Gunshot injury to the temporal bone: an analysis of thirty-five cases.

By retrospective analysis of 35 surviving gunshot injuries to the temporal bone and by presentation of 6 representative cases, the management and reconstructive procedures of these injuries in the Tulane University affiliated hospitals are presented. The most frequent single injury was facial nerve paralysis (16 cases), followed by external canal injury and conductive hearing loss. Anacusis occurred in 12 cases. In conductive hearing loss the intact posterior wall tympanoplasty with mastoidectomy (16 cases), or the modified radical mastoidectomy (5 cases), allowed middle ear reconstruction. Transmastoid facial canal decompression, combined with the above procedures or with a middle fossa craniotomy, was performed in 6 cases. Delayed facial reconstruction (5 cases) utilized microneural anastomosis between facial-facial and hypoglossal-facial nerves and fascia lata slings. Intracranial complications of thrombosis of internal carotid artery, dural venous lacerations, temporal lobe aphasia, bitemporal hemianopsia, cerebral abscesses and meningitis are also discussed.

Adolescent↗
PubMed1979

Arterial wall properties and dietary atherosclerosis in the racing greyhound.

The effects of experimental (dietary) atherosclerosis on arteries from racing greyhounds were studied. Measurements of pressure and external diameter were made on islated carotid and iliac arteries under active (norepinephrine, 5 microgram/ml) and passive (zero Ca2+ and 2 mM EGTA) smooth muscle conditions. Iliac arteries from diet-fed animals demonstrated substantial intimal lesions, but the carotid arteries were usually grossly involved. Arteries from atherosclerotic animals were stiffer during passive conditions, with the iliac arteries having the greater changes. In iliac arteries from treated animals, collagen and elastin contents were decreased, and the collagen-to-elastin ratio was increased; in carotid arteries from treated animals, elastin content was increased and the collagen-to-elastin ratio was decreased. The maximum range of control of arterial wall mechanics by smooth muscle was diminished in treated iliacs but unchanged in carotids. Both force development and constriction responses associated with smooth muscle activation were diminished in treated iliacs but unchanged in treated carotids. Mechanical properties of series elastic elements in treated iliacs were stiffer, but treated carotids were unchanged.

Animals↗
PubMed1979

Comparison of arterial wall mechanics in normotensive and spontaneously hypertensive rats.

Segments of carotid artery from Wistar (NW), Kyoto Wistar (WKY), and spontaneously hypertensive rats (SHR) were used to compare mechanical properties and connective tissue composition. Pressure-diameter measurements were made under conditions of active (5 microgram/ml norepinephrine) and passive (0 mM Ca2+ and 2 mM EGTA) smooth muscle. Systolic blood pressures averaged NW, 121 +/- 3; WKY, 124 +/- 4; and SHR, 187 +/- 5 MMHg. Passive mechanics were stiffest in SHR and most compliant in NW arteries. No differences in collagen-elastin ratio were found but collagen + elastin was lowest in SHR and highest in NW carotids. These results are not consistent with current concepts of the contribution of connective tissue elements to passive mechanics. Maximum stress development was NW, 561 +/- 49; WKY, 735 +/- 50; and SHR, 944 +/- 79 X 10(3) dyn/cm2. Diameter reductions to NE at 100 mmHg were NW, 17.6 +/- 2.4%; WKY, 16.7 +/- 2.0%; and SHR, 24.8 +/- 2.4%. The former suggests different contractile protein contents or more efficient intercellular force coupling in SHR. The latter suggests a more effective contractile apparatus as a result of stiffer passive muscle elements and/or a relatively larger wall thickness.

Animals↗
PubMed1978

Malignant hyperthermia in a Greyhound.

A rapid rise in rectal temperature (to 45 C) in a young male Greyhound was attributed to the use of halothane and succinylcholine. Circulatory failure and death occurred within approximately 90 minutes of the onset of the hyperthermia.

Anesthesia, Inhalation↗
PubMed1978

Tuberculous otitis media with complications.

Tuberculous otitis media, although uncommon today, is still a differential diagnosis of suppurative otitis media. Our patient's otitis progressed from a draining ear with hearing loss to include facial nerve paralysis and meningitis. Several surgical procedures including radical mastoidectomy were insufficient to halt progression of the disease. After culture of acid-fast bacilli from the aural drainage and the cerebrospinal fluid, antituberculous chemotherapy was started and the patient responded well to treatment.

Adult↗
PubMed1978

Direct effect of physiological doses of arginine vasopressin on the arterial wall in vivo.

Effects of topically applied arginine vasopressin (VPA), in 100-150 muU/ml blood concentration, on external diameter (D) and on dynamic elastic modulus (E*) of surgically denervated common carotid (CC) and femoral (FA) arteries have been studied before and after hypophysectomy in anesthetized dogs. Changes in D, E*, and flow resistance (R) of the CC and FA vascular beds before and after removal of the pituitary were also determined. It was found that VPA elicited a substantial (max 21-26%) decrease in E* and a smaller (max 5.9-6.9%) reduction in D of FA independent of the presence of absence of the pituitary gland. The VPA effect developed more rapidly after hypophysectomy than before. In the CC, VPA did not significantly affect values of E*. During the 1-h period after hypophysectomy, statistically significant decreases in E*-CC, E*-FA, and D-CC were observed, but D-FA did not change, although arterial pressure as well as R-FA and R-CC were diminished. These results give further support to physiological vascular actions of VPA and a possible role in short-term circulatory control. In large arteries, the effects of VPA also seem to be regionally differentiated.

Animals↗