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Biomedical subjects

G Pennington

Publications and source records attributed to G Pennington.

12 recordsLinked to original sources
PubMed1999

Effect of individual or combined ablation of the nuclear groups of the lamina terminalis on water drinking in sheep.

The subfornical organ (SFO), organum vasculosum of the lamina terminalis (OVLT), and median preoptic nucleus (MnPO) were ablated either individually or in various combinations, and the effects on drinking induced by either intravenous infusion of hypertonic 4 M NaCl (1.3 ml/min for 30 min) or water deprivation for 48 h were studied. Ablation of either the OVLT or SFO alone did not affect drinking in response to intravenous 4 M NaCl, although combined ablation of these two circumventricular organs substantially reduced but did not abolish such drinking. Ablation of the MnPO or MnPO and SFO together also substantially reduced, but did not abolish, drinking in response to intravenous hypertonic NaCl. Only near-total destruction of the lamina terminalis (OVLT, MnPO, and part or all of the SFO) abolished acute osmotically induced drinking. The large lesions also reduced drinking after water deprivation, whereas none of the other lesions significantly affected such drinking. None of these lesions altered feeding. The results show that all parts of the lamina terminalis play a role in the drinking induced by acute increases in plasma tonicity. The lamina terminalis appears to play a less crucial role in the drinking response after water deprivation than for the drinking response to acute intravenous infusion of hypertonic saline.

Animals↗
PubMed1998

The impact of vasodilators on random-pattern skin flap survival in the rat following mainstream smoke exposure.

This study demonstrates that acute mainstream cigarette smoke exposure is deleterious to dorsal random-pattern skin flap survival in the rat. Three vasodilators were also studied for their ability to mediate flap survival after smoke exposure. Sprague-Dawley rats (10 per group) were exposed to two cigarettes per day over a 14-day period. This is an exposure equivalent to that of an average cigarette smoker. Dorsal McFarlane caudally based random-pattern skin flaps (4 x 10 cm) were created on day 7 of the smoke exposure. Enteral phenoxybenzamine (0.56 mg per kilogram per day), enteral nifedipine (10 mg per kilogram per day), and topical nitroglycerin (1.3 cm or 7.5 mg per day) were administered after creation of the dorsal skin flaps in two doses daily during smoke exposure. Fluorescein was used to delineate areas of viability accurately. A pad digitizer was utilized to calculate designated skin flap areas to +/-1.0 mm2. Experimental animals demonstrated a 23% decrease (p < 0.01) in skin flap area survival compared with the control animals. The phenoxybenzamine group demonstrated a 5.5% increase in flap area survival (p=0.068), the nifedipine group demonstrated a 4.1% increase in flap area survival (p=0.049), and the nitroglycerin group demonstrated an 8.9% increase in flap area survival (p=0.049). These data suggest that phenoxybenzamine appears to affect skin flap survival marginally after smoke exposure. However, nifedipine and nitroglycerin improve random-pattern skin flap survival significantly after mainstream cigarette smoke exposure in the rat. These results imply that pharmacological intervention with vasodilators may ultimately prove clinically useful for random-pattern skin flap salvage in the cigarette-smoking patient.

Animals↗
PubMed1991

Endomyocardial biopsies in pediatric patients with no irradiation. Use of internal jugular venous approach and echocardiographic guidance.

Heart transplants in pediatric patients have moved from an experimental, end-stage treatment to a valuable therapy for inoperable congenital heart disease and dilated cardiomyopathies. Cardiac rejection is a frequent problem in children with heart transplants. The technical difficulties of obtaining biopsies in small children have encouraged the use of noninvasive methods of detection although endomyocardial biopsy continues to be the most reliable method of surveillance for cardiac rejection. We examined our experience over 7 years with 4 patients (ages 8 months to 10 years) who had a total of 88 endomyocardial biopsies using echocardiographic guidance. The biopsies were done using a Caves-Schultz biotome via the right internal jugular vein. Biopsies were performed in the procedure room, 61%; pediatric intensive care unit, 18%; hospital private room, 18%; and catheterization laboratory, 3% of the time. At 5.0, 6.5, or 8.5 French biotome was used depending on the size of the patient. Twelve episodes of rejection were detected in these patients. The time for venous access was 17 +/- 15 min, and the biopsies took 25 +/- 11 min using this approach. Biopsies were obtained from the right ventricular free wall, apex, and septum to detect focal rejection for a total of 4-6 tissue samples per biopsy. Neither general anesthesia nor fluoroscopy was needed for these biopsies. Costs ranged from $1120 in the patient room to $1590 in the pediatric intensive care unit. Five different biopsies using a femoral approach with fluoroscopic guidance averaged $2250 and did not include the functional assessment obtained using echocardiography. Using the echocardiogram one can see the ventricular muscle and completely avoid perforation. Thus, this technique is technically feasible in children with few complications at a reduced cost, compared to fluoroscopically guided biopsies.

Biopsy↗
PubMed1990

Results of internal thoracic artery grafting over 15 years: single versus double grafts.

One hundred consecutive patients who had coronary artery bypass grafting using both internal thoracic arteries (ITAs) and saphenous veins, operated on during a 3-year period between 1972 and 1975, have been compared retrospectively with a series of 100 patients operated on during the same period who had one ITA graft along with saphenous vein grafts. The two groups were similar with respect to age, sex, risk factors for coronary artery disease, angina class, extent of coronary artery disease, left ventricular function, number of coronary bypass grafts performed, and completeness of revascularization. Single ITA operative mortality was 2% and double ITA, 9% (p = NS). The mean follow-up of hospital survivors was 14.4 +/- 2.7 years; all but 7 patients had follow-up for at least 10 years. At 13 years, the actuarial patency of the right ITA was 85% and the left ITA, 82%. These data strongly suggest a survival benefit for patients with double ITA grafts among hospital survivors (74% versus 59%; p = 0.05). Patients receiving two ITA grafts had a significant freedom from subsequent myocardial infarction (75% versus 59%, p less than 0.025), recurrent angina pectoris (36% versus 27%, p less than 0.025), and subsequent total ischemic events (32% versus 18%, p less than 0.01). These data also suggest improved freedom from coronary artery interventional therapy (percutaneous transluminal coronary angioplasty and reoperation) when two ITA grafts were used. These results support the use of bilateral internal thoracic artery grafting in selected patients.

Actuarial Analysis↗
PubMed1989

Intracerebroventricular saccharide infusions inhibit thirst induced by systemic hypertonicity.

The effect of intracerebroventricular (i.c.v.) infusion of various iso- and hypertonic saccharide solutions on water intake stimulated by intracarotid (i.c.) infusion of hypertonic NaCl was studied in sheep. Without an i.c.v. infusion, water intake during a 10-min period following an i.c. infusion of 4 M NaCl (1.4 ml/min over 20 min) was 1.5-2.0 litres. I.c.v. infusion of all saccharide solutions (made up in artificial cerebrospinal fluid (CSF) with no Na) tested, 0.27 or 0.7 M D-glucose, L-glucose, 2-deoxyglucose and sucrose, decreased (35-65%) water intake. In general, there was little or no difference in antidipsogenic effectiveness between the isotonic and the hypertonic solutions or between the different saccharides used. I.c.v. infusion of artificial CSF ([Na] = 150 mM) did not alter water intake. CSF [Na] was decreased by all of the saccharide infusions. CSF osmolality was increased by the hypertonic solutions, was decreased by the artificial CSF and was unchanged by the isotonic solutions infused. The observation that the antidipsogenic effectiveness of saccharides which readily cross the blood-brain barrier (BBB; D-glucose, 2-deoxyglucose) was similar to that of saccharides which do not readily cross the BBB (sucrose, L-glucose) contrasts with effects reported on sodium appetite and suggests that the Na sensors involved in the inhibition of hypertonic NaCl-stimulated water intake are located close to or on the surface of the brain ventricular system, i.e. are responsive to changes in CSF [Na].(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Extracorporeal membrane oxygenation for postoperative cardiac support in children.

Prolonged circulatory support for cardiac failure has been increasingly successful in adults but has had very limited use in children. From January 1982 to December 1985, 13 children with postoperative cardiac failure refractory to conventional therapy were treated with extracorporeal membrane oxygenation. Ages ranged from 9 days to 17.6 years (mean = 3.8 years); weights ranged from 2.8 to 50 kg (mean = 13.8 kg). Seven patients had obstructive lesions of the right ventricle, such as pulmonary stenosis and tetralogy; the other patients had tricuspid atresia, truncus arteriosus, complete transposition, total anomalous pulmonary venous connection, pericardial tamponade, and a drug reaction after heart transplantation. One patient (nonsurvivor), who could not be separated from cardiopulmonary bypass, required extracorporeal membrane oxygenation in the operating room. In the remaining 12, the interval between operation and the start of extracorporeal membrane oxygenation ranged from 9 to 50 hours (mean = 22.2 hours). Four patients were cannulated through the groin and nine through the chest. Peak flows ranged from 1.05 to 2.74 L/min/m2 (mean 1.92 L/min/m2). Duration of oxygenator support ranged from 12 hours to 9 days (mean = 3.4 days). Seven patients required reexploration for bleeding. Renal insufficiency developed in five patients, four of whom underwent hemodialysis or ultrafiltration during extracorporeal membrane oxygenation. Two patients had evidence of clots in the oxygenator circuit. Seven patients were weaned from extracorporeal membrane oxygenation. Failure to wean from the oxygenator was related to neurologic sequelae of prolonged hypotension before institution of oxygenation in three patients. Mediastinitis developed in three of the seven patients who were weaned. One of these three died in the hospital 74 days after being weaned from the oxygenator. There has been one late death 6 months after oxygenator support was withdrawn. At most recent examination, five children were well, with normal cardiac function 7 months to 4.3 years postoperatively (mean = 32 months). This series suggests that profound cardiac insufficiency in children after cardiac operations can be successfully managed with extracorporeal membrane oxygenation with excellent functional recovery, although major complications are common in this critically ill group of patients.

Adolescent↗
PubMed1979

Revascularization of the right coronary artery.

This study was undertaken to evaluate revascularization of the right coronary artery with regard to factors that enter into the decision to graft less significant lesions, such as graft flow, graft patency and progression of proximal disease. The results of grafting the right coronary artery were studied in 23 patients with lesions reducing luminal diameter by less than 50 percent (Group 1), 35 patients with luminal narrowing of 50 to 70 percent (Group 2) and 112 patients with greater than 70 percent luminal narrowing (Group 3). At operation there was no significant difference in saphenous vein graft flows among the three groups. Postoperatively the mean follow-up period was 20, 27 and 26 months, respectively. Graft patency was not significantly different among the three groups. Progression of the proximal lesion was studied and compared with that in 71 ungrafted right coronary arteries, 60 with less than 50 percent stenosis and 11 with more than 50 percent stenosis. Among vessels with less than 50 percent narrowing, the proximal lesion showed progression in 26 percent of the ungrafted vessels and in 83 percent of the grafted vessels (P less than 0.005); progression to total occlusion occurred in 3 percent of the former and in 28 percent of the latter (P less than 0.005). Progression to total occlusion was more frequently associated with a patent than with an occluded graft (P less than 0.05). The occurrence of significant progression in ungrafted vessels and the lack of effect on graft patency of the severity of the proximal disease suggest that revascularization of less significant lesions may be of value. However, the resultant increase in progression of proximal disease makes the patient dependent on the long-term patency of the vein graft.

Cardiac Catheterization↗
PubMedDate not supplied

Heart transplantation in patients over age fifty-five years.

The age limit for heart transplantation remains undefined. The shortage of available donors coupled with fears of increased morbidity and mortality in older patients has until recently resulted in a limited application of heart transplantation in patients over age 50 years. In 1986, however, data from the International Heart Transplant Registry demonstrated that 25% of all patients undergoing this procedure were over age 55 years. This study reviews our experience with 30 consecutive patients who underwent heart transplantation over a 15-month period. There were eight patients over age 55 years (group 1) and 22 patients under age 55 years (group 2). We compared the hospital course and incidence of infection and rejection and other complications after heart transplantation between the two groups. Carefully selected patients between ages 55 and 60 years can undergo transplantation with similar expectations to younger patients for survival, complications, and rehabilitation, including employability. Caution is warranted in extrapolating these optimistic data to patients older than age 50 years.

Age Factors↗