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Biomedical subjects

C A Rawlings

Publications and source records attributed to C A Rawlings.

At least 73 records · Page 4Linked to original sources
PubMed1982

Neurologic, psychiatric, and cardiovascular complications in children struck by lightning.

The neurologic changes following lightning injury include coma with cerebral edema, inappropriate secretion of antidiuretic hormone (ADH), seizures, cerebellar ataxia, and painful sensory disturbances. Deteriorating neurologic status may warrant the use of intracranial pressure monitoring devices. Myocardial injury and transient hypertension are generally evident at the onset. Monitoring of the cardiac rhythm may be needed for as long as a week for late onset arrythmia. Abnormalities of memory, mood, and affect noted on recovery of consciousness may persist for months, necessitating close psychiatric and neurlologic follow-up.

Brain Diseases↗
PubMed1982

Clinical laboratory evaluations of seven heartworm infected beagles: during disease development and following treatment.

Clinical laboratory evaluations were performed in 7 beagles for 12 months following experimental infection with Dirofilaria immitis and for 14 months following adulticide and microfilaricide treatment. Few abnormalities were detected. A mild basophilia and thrombocytopenia developed late during the year of infection and after arsenical treatment there were transient increases in eosinophils, SGPT, and SAP. Coagulation and blood gas studies were normal. The minimal changes were attributed to either: (1) the one year infection with 50 infective larvae was an insufficient insult or (2) an idiosyncrasy in the host-parasite relationship is required in order to produce marked alterations in clinical laboratory evaluations.

Animals↗
PubMed1982

Cardiopulmonary effects of intravenous xylazine, ketamine, and atropine in the dog.

Atropine (0.04 mg/kg of body weight) and the combination of xylazine (1.1 mg/kg) and ketamine (11 mg/kg) were administered IV to dogs, and cardiopulmonary variables were measured. The drug combination caused hypoventilation, as reflected by increased PaCO2 and a 30% decrease in cardiac index, whereas arterial pressure, left atrial pressure, and peripheral resistance were increased. These variables began returning toward base-line values during anesthesia and were not different from base-line values by 30 minutes.

Anesthesia↗
PubMed1981

Effect of long-term aspirin treatment on platelet adhesion to chronically damaged canine pulmonary arteries.

The effect of aspirin on platelet adhesion to chronically damaged pulmonary arteries was studied in 18 dogs. Chronic injury was produced in all dogs by infection with the canine heartworm Dirofilaria immitis (DI). Ten dogs were subjected to 4 days of chronic injury. Eight dogs were subjected to 30 days of chronic injury. Five of the 4 day injury and 4 of the 30 day injury dogs received aspirin daily; (325 mg/day orally). Aspirin was started 3 days prior to infection with DI. Pulmonary arteries were perfusion fixed in situ at physiologic pressure. The damaged pulmonary arteries were located by Evan's blue staining (2 ml/kg of 1% dye given one hr prior to perfusion) and prepared for scanning electron microscopy. Both groups of dogs with 4 day DI infection had monolayers of platelets adhered to exposed subendothelium. Aspirin treated dogs had enhanced platelet adhesion to damaged arteries. Aspirin treatment for 33 days reduced platelet adhesion. The damaged arteries of treated dogs infected with DI for 30 days had very few platelets adhering to the damaged surface. However, non-treated dogs subjected to 30 days of infection had platelet adhesion equivalent to the 4 day non-treated infection group. These results suggest that although aspirin is ineffective in preventing platelet adhesion in short term therapy it is effective when given for longer time periods. This inhibitory effect may occur due to platelet membrane changes rather than because of aspirin inhibition of cyclooxygenase.

Animals↗
PubMed1981

Development and resolution of radiographic lesions in canine heartworm disease.

Thoracic radiography of 7 Beagles was performed before heartworm infection, during a 1-year heartworm infection, and for 1 year following appropriate treatment. Cardiac and vascular lesions on thoracic radiographs were compared with angiographic changes. Within 3 months of obstructed blood flow in the caudal lobar arteries, associated increased focal parenchymal densities were detected. These lesions were regarded as characteristic of heartworm disease. Although the most severe arteriographic changes were in the caudal lobar arteries, lobar arterial changes on a lateral view were best detected in the right cranial lobar artery. These arteries increased in size during infection and decreased in size after treatment. It was concluded that the dorsoventral view is best for evaluation of the caudal lobar arteries. The most marked parenchymal lesions were detected during the first 6 months following adulticide treatment. These lesions and the other radiographic alterations then decreased in severity. Persistence of the parenchymal lesions were related to persistence of heartworm infection.

Animals↗
PubMed1981

Arterial blood gas and acid-base values in dogs with various diseases and signs of disease.

Results of arterial blood gas and acid-base analysis on initial samples prior to therapy were reviewed for 220 dogs admitted to the University of Georgia Veterinary Teaching Hospital. Acidemia or alkalemia was detected in 61 of 220 dogs (28%). The most common acid-base abnormality was metabolic acidosis (79 of 220 dogs--36%). Primary metabolic acidosis was the acid-base category associated most frequently with the combination of vomiting and diarrhea, dehydration, and the combination of polydipsia and polyuria, whereas normal mean arterial PCO2 and [HCO3-] values and primary metabolic acidosis were detected with equal frequency in vomiting, diarrhea, and cyanosis. Arterial hypoxemia was found most frequently in patients with restrictive respiratory tract disease (restricted lung expansion), lower respiratory tract disease, heartworm disease, and circulatory system disease. Significantly lower (P less than or equal to 0.05) arterial pH and PO2 were detected initially in dogs that eventually died, as compared with dogs that were improved at the time of discharge from the hospital. Mean [HCO3-] values also were lower initially in dogs that eventually died, as compared with those that improved, but the differences were not statistically significant.

Acid-Base Imbalance↗
PubMed1981

Platelet adhesion and myointimal proliferation in canine pulmonary arteries.

Pulmonary arteries were studied by scanning and transmission electron microscopy in 15 preconditioned dogs. Five dogs were control animals, while 10 dogs were studied 4 and 30 days following transplantation of adult heartworms into the pulmonary arteries. Evan's blue dye was used to locate areas of vascular damage. Pulmonary arteries from control dogs exhibited no Evan's blue staining. The surface and ultrastructural characteristics of these blood vessels were comparable to normal peripheral blood vessels. Pulmonary arteries removed from dogs after 4 days of heartworm infection exhibited extensive staining with Evan's blue. These stained areas had disrupted endothelium with many platelets adhered to the exposed subendothelium. In addition, leukocytes were attached to adjacent areas of damaged endothelium. Pulmonary arteries of dogs infected with heartworms for 30 days also exhibited extensive staining with Evan's blue. The blue-stained areas in this group had two typical responses. On some portions the lesions were similar to those seen at 4 days (ie, loss of endothelium with platelet and leukocyte adhesion), while other stained areas had complex lesions that projected from the surface into the lumen of the blood vessel. These lesions were endothelialized, and transmission electron microscopy revealed that they consisted of large numbers of smooth muscle cells that had migrated through the internal elastic lamina. The findings in the 30-day infection group suggest that the proliferative lesion formation was a result of an ongoing active process of endothelial loss and plateletleukocyte adhesion. The characteristic response of canine pulmonary arteries to the presence of heartworms (endothelial loss, platelet-leukocyte adhesion, and development of myoproliferative intimal lesions) suggests that this condition is a potential model for study of the early vascular changes that produce myointimal proliferation.

Animals↗
PubMed1981

Renal function after prolonged hypotensive anesthesia and surgery in dogs with reduced renal mass.

The effect of prolonged hypotensive anesthesia and surgery on renal function was studied in 8 dogs with decreased renal mass. Renal mass was reduced by unilateral nephrectomy and ligation of 4 of the 6 terminal renal artery branches of the opposite kidney. One week after reduction in renal mass, the dogs were azotemic with a serum urea nitrogen (SUN) value of 65.8 +/- 11.5 mg/dl. Glomerular filtration rate, as estimated by 14C-inulin clearance, was 0.66 +/- 0.19 ml/kg of body weight/hour. A mean arterial pressure of less than 75 mm of Hg was maintained for 4 hours in dogs given 2.3 +/- 0.7% halothane. An exploratory laparotomy lasting 1 hour was performed. The day after the hypotensive episode, 3 dogs began vomiting, became dehydrated, and had SUN values greater than 100 mg/dl. The SUN values returned to base-line values after the dogs were rehydrated. Eight days after the hypotensive episode, 14C-inulin clearance decreased 15.2 +/- 8.2% (P less than 0.005) compared with base-line clearance values. Light microscopic and electron microscopic observations of the kidneys did not demonstrate acute renal failure. Prolonged hypotensive anesthesia can cause a decrease in renal function, and may cause prerenal uremia and/or acute renal failure.

Anesthesia, Inhalation↗
PubMed1981

Exercise in the dog with Dirofilaria immitis infection.

Cardiopulmonary function in Beagles that had been infected 18 months previously with 100 infective Dirofilaria immitis larvae was studied before and after an exercise program. The treadmill exercise program lasted for 2.5 months at 5 days per week until the dogs were running for 20 minutes at 11.3 km/hr up a 9% grade. Although the Beagles had mild pulmonary hypertension (mean pulmonary arterial pressure before training of 26.8 +/- 2.2 [SD] mm of Hg) and radiographic signs of cardiopulmonary disease, the dogs tolerated the program without signs of congestive heart failure or further development of pulmonary hypertension. Pulmonary arterial pressure was not increased during the 20-minute exercise period when measured at the completion of the 10-week exercise program.

Animals↗
PubMed1980

Acute response of pulmonary blood flow and right ventricular function to Dirofilaria immitis adults and microfilaria.

Pulmonary arterial pressures, right ventricular pressures, and right ventricular force of contraction (max dP/dt) were measured before and after the surgical addition of Dirofilaria immitis adults and microfilaria. Six adult anesthetized and heparinized dogs were studied during thoracotomy to compare these pressure measurements with left caudal pulmonary arterial flow. Diversion of pulmonary flow was performed to obtain incremental increases in pulmonary flow through the left caudal lobar artery and to increase right ventricular afterload. The addition of adult heartworm disease, microfilaria, or both did not produce either pulmonary arterial hypertension or increase right ventricular pressure and force of contraction.

Animals↗
PubMed1980

Cardiopulmonary function in the dog with Dirofilaria immitis infection: during infection and after treatment.

Cardiopulmonary function in seven Beagles (under pentobarbital anesthesia) was determined before they were inoculated with Dirofilaria immitis larvae, at 6 and at 12 months after 50 infective larvae were inoculated, and at 7 and 12 months after adulticide and microfilaricide treatment was begun. Pulmonary hypertension (26.4 mm of Hg +/- 3.5 (SD)) was present at 12 months after the dogs were inoculated, as compared with base-line pulmonary arterial pressure (16.0 mm of Hg +/- 2.4), and was resolved within 7 months after initial adulticide treatment (19.8 mm of Hg +/- 1.4). Pulmonary artery pressure response to hypoxia (33.3 mm of Hg +/- 2.4) at 12 months after inoculation (vs base line of 25.3 mm of Hg +/- 2.2) and to isoproterenol infusion (37.6 mm of Hg +/- 4.8) at 12 months (vs base line of 14.3 mm of Hg +/- 1.7) revealed an accelerated pulmonary hypertensive response. This pulmonary hypertensive response to isoproterenol infusion (17.7 mm of Hg +/- 1.4) at 7 months after treatment resolved following treatment. The pulmonary hypertensive response to hypoxia was still present (32.5 mm of Hg +/- 3.0) 7 months after treatments. Resolution of pulmonary hypertension reinforces the clinical decision to treat dirofilariasis in an effort to prevent further development of pulmonary hypertension, as well as to permit resolution of this clinical sign.

Animals↗
PubMed1980

Pulmonary vascular response during phases of canine heartworm disease: scanning electron microscopic study.

Pulmonary arteries and veins of 14 dogs in phases of heartworm disease (Dirofilaria immitis infection) were examined by scanning electron microscopy. Two dogs were infected with D immitis microfilaria only, whereas 12 dogs were infected with adult D immitis. Seven of the dogs infected with adult worms were untreated. Two of these 7 dogs had natural infections of unknown duration introduced by mosquito bite, whereas 5 were experimentally infected for 30 days. The remaining five dogs were experimentally infected for 1 year and had worms removed by drug therapy. These five dogs were maintained 12 months after treatment. Arteries and veins from dogs infected with microfilaria had a continuous sheet of endothelial cells. Arterial endothelium from the seven nontreated dogs infected with adult heartworms exhibited swirling patterns, pore formation, and separation of intercellular junctions. Arteries from all dogs had numerous endothelialized villus protrusions; veins had similar, less extensive changes. Arteries and veins from experimentally infected dogs were similar to naturally infected dogs, indicating the infection procedure produced lesions similar to that normally seen in heartworm disease. The extent of vascular lesions was reduced in four of the five treated dogs that had been infected with adult worms. Adult worms, not microfilaria, may produce the vascular lesions seen in heartworm disease. Lesions will regress if worms are removed from the circulation. Lesions may be caused by generation of humoral factors initiated by the presence of adult worms.

Animals↗
PubMed1980

Scanning electron microscopy of canine pulmonary arteries and veins.

In this communication we describe (1) a method for preparing pulmonary arteries and veins for examination by scanning electron microscopy and (2) the topographic characteristics of the luminal surface of these vessels. Seven healthy adult dogs were used in this study. The pulmonary vasculature was washed free of blood by perfusion with Tyrode's solution. Blood vessels were partially fixed in situ under physiologic pressure in 3 dogs (15 mm of Hg) or 2 times physiologic pressure in 4 dogs (30 mm of Hg) by perfusion with 1% glutaraldehyde. The pulmonary artery and aorta were tied off and the lungs were removed and immersed in 1% glutaraldehyde for 4 hours for additional fixation under pressure. Blood vessels were dissected free of surrounding tissue, further fixed in 2.5% glutaraldehyde, postfixed in osmium tetroxide, dehydrated, and critical point dried. The luminal surfaces were sufficiently flat to allow visualization of most of the topographic features of the luminal surface. Even 1 missing endothelial cell wound have been obvious. Contrary to previous reports, we did not find a dense population of finger-like projections on the surface of arterial endothelium. Rather, we found a modest number of small rounded blebs. The venous endothelial sheet was similar in appearance. These observations demonstrate that scanning electron microscopy may be used to study vascular lesions in pulmonary vaessels, as well as in more accessible peripheral vessels.

Animals↗
PubMed1979

Calibration and use of electromagnetic flow transducers.

Electromagnetic flowmeters frequently are used to measure volumetric blood flow in vessels. An in vitro method of calibration, using a constant supply-pressure system, was studied. Potential problems encountered in acute and chronic applications are discussed. Using this calibration system, manufacturers' recommended calibration factors were not in agreement with actual flow calibration factors, and zero, as determined electrically, was not the same as that determined mechanically. Transducer sensitivity decreased with increasing concentrations of red blood cells but was not affected by fluid viscosity. Application problems of vessel constriction by the transducer, transducer orientation about the vessel, and chronic instrumentation are discussed.

Electromagnetic Phenomena↗
PubMed1978

Pulmonary vascular response of dogs with heartworm disease.

Heartworm diseases in dogs is an infectious disease that produces pulmonary hypertension. Dogs with the early vascular changes of heartworm disease, but without the clinical cardiopulmonary signs and pulmonary hypertension, were studied. Dogs with early heartworm were identified that had an exaggerated hypertensive response to hypoxia and to postaglandin F2alpha as compared to those of normal dogs. The pulmonary hypertensive response of dogs with spontaneous heartworm disease varied widely between individuals.

Animals↗