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Biomedical subjects

D E Longnecker

Publications and source records attributed to D E Longnecker.

13 recordsLinked to original sources
PubMed1979

Influence of anaesthetic agents on the survival of rats following acute ischaemia of the bowel.

We compared the effects of ketamine and halothane anaesthesia on the survival of rats subjected to superior mesenteric artery occlusion. Survival was significantly greater with halothane. Animals anaesthetized with ketamine developed arterial hypocarbia during bowel ischaemic shock, while those receiving halothane did not. Arterial hypoxaemia was not present in either group. Haematocrits increased in both groups following bowel ischaemia. Excess lactate was increased significantly in non-survivors compared with survivors. The survival data contrast with previous results obtained after haemorrhagic hypotension and emphasize the need to consider differing therapeutic approaches in the various shock states.

Anesthesia, Inhalation↗
PubMed1979

Renin response to hemorrhage in awake and anesthetized rats.

Anesthetic agents have been shown to alter survival in animals subjected to hemorrhage. Since survival after hemorrhage is increased by inhibitors of the renin-angiotensin system, we asked whether anesthetic agents altered renin release during hemorrhage. We studied 33 rats which were subjected to one hour of hemorrhagic hypotension at a mean arterial pressure of 40 mm Hg. Animals were either awake or anesthetized with halothane or ketamine. Anesthesia alone did not alter plasma renin activity (PRA), whereas hemorrhage resulted in approximately a ten-fold increase in PRA in both awake and anesthetized animals. After the shed blood was returned to the animal, intravenous saralasin, an angiotensin II competitive inhibitor, produced a 21-24 mm Hg decrease in blood pressure in all animals, regardless of the severe hemorrhage is unaltered by halothane or ketamine anesthesia, that the renin-angiotensin system provides a similar amount of blood pressure support in both awake and anesthetized animals, and that the anesthetic influence on survival following severe hemorrhage does not result from anesthetic-induced alterations of the renin-angiotensin system.

Animals↗
PubMed1978

Alterations in venous compliance in hemorrhagic shock.

Nine dogs and one primate were placed on total cardiopulmonary bypass and subjected to a simulated hemorrhagic shock procedure. Venous compliance was determined by occluding the venous outflow catheters; venous flow and pressure drop were used to calculate resistance. Individual measurements were made for the superior (SVC) and inferior vena caval (IVC) beds. During hypotension, compliance increased equally in the SVC and IVC; following reinfusion, IVC compliance was consistently lower than SVC compliance. Resistance of the sVC system increased slightly more rapidly during early hypotension than did that of the IVC, but SVC resistance then decreased and remained significantly below that of the IVC system throughout the posthypotension period. These results are interpreted as indicating a different response of the two vascular beds, particularly an increase in IVC arteriolar resistance with a decrease in venous tone. To the extent that the splanchnic bed contributes to the IVC system changes, they are contrary to the concept of a maintained venous tone and decreased arteriolar tone after hemorrhagic shock.

Animals↗
PubMed1976

Sensitivity of small subcutaneous vessels to altered respiratory gases and local pH.

Television microscopy was used to quantitate the responses of small arteries and veins, in the wings of unanesthetized bats, to alterations in the inspired concentrations of O2 and CO2. Mean arterial pressure, heart rate, and the diameters of small arteries (28-54 mum) and veins (50-128 mum) were measured during a 90-min protocol--30 min with an inspiratory gas mixture of 20% O2 and 80% N2 (control period); 30 min with a gas mixture containing 5% O2 (hypoxic period) or 12, 20, or 28% CO2 (hypercapnic period); and 30 min with the original control gas. The hypoxic responses were dilatation of arteries and no change in the veins in both innervated and surgically denervated wings. Hypercapnia resulted in artery dilatation in innervated wings. Hypercapnia resulted in artery dilatation in innervated wings and constriction in denervated wings. The veins constricted in both innervated and denervated wings during the hypercapnia period. In another series, topical application of Krebs solutions (pH ranging from 7.7 to 6.7) to exposed segments of small arteries and veins produced dilatation of both vessels with decreasing pH. Artery dilatation during hypoxia and vein constriction during hypercapnia involve non-neural mechanisms, while both a neural stimulus for dilatation and a non-neural stimulus for constriction are components in the response of innervated arteries to hypercapnia. The non-neural stimulus for artery and vein constriction during hypercapnia is not a local decrease in pH.

Animals↗
PubMed1976

Influence of anesthetic agent on survival following hemorrhage.

One hundred and twenty-eight Sprague-Dawley rats were each anesthetized with one of four anaesthetics and subjected to a standard hemorrhage protocol to determine the effects of anesthetics on survival following hemorrhage. The anesthetics studied were: halothane, 1.26 vol per cent; fluroxene, 4.5 vol per cent; pentobarbital, 50 mg/kg ip; ketamine, 125 mg/kg, im. Mean arterial pressure was conrolled at 40 torr during 60 minutes of hemorrhage. Cumulative survival rates were determined at the end of hemorrhage and 24 hr, 48 hr, 72 hr, and 7 days after hemorrhage. Twenty-four-hour survival rates were: halothane, 50.0 per cent; fluroxene, 56.3 per cent; pentobarbital, 59.4 per cent; ketamine, 84.4 per cent. Seven-day survival rates were: halothane, 46.9 per cent; fluroxene, 18.7 per cent; pentobarbital, 53.1 per cent; ketamine; 81.3 per cent. Survival rates were significantly higher (P less than 0.05) in animals anesthetized with ketamine compared with survival rates associated with the other anesthetics. Long-term (72-hr and seven-day) survival rates were significantly (P less than 0.05) lower in animals anesthetized with fluroxene. Microscopic examination of livers and small intestines revealed significantly fewer (P less than 0.05) athologic changes in the splanchnic organs of hemorrhaged rats anesthetized with ketamine compared with animals anesthetized with the other drugs.

Anesthetics↗
PubMedDate not supplied

Clinical investigation of a new intravenous anesthetic--etoxadrol hydrochloride (CL-1848; U-37862A).

Twenty-eight patients were anesthetized with etoxadrol as primary agent. The anesthesia produced was characterized by profound analgesia and amnesia, while pharyngeal and laryngeal reflexes, as well as swallowing and lid reflexes, remained active. Systolic, diastolic, and pulse pressure were slightly increased, with associated tachycardia and tachypnea. A dose of 0.75 mg/kg produced anesthesia for an average of 26 (14 to 53) minutes. Alternating nystagmus was present for several hours and associated with dreams and/or visions that were pleasing to most patients. Six patients, however, had unpleasant dreams for up to 24 hours. One patient given an excessive dose (4.65 mg/kg) was cataleptic, amnesic, and analgesic for 6 days. The occurrence of unpleasant dreams and aberrations in over 20% of the patients suggests that the drug probably has little usefulness in anesthesia. However, the extreme safety of the drug (an LD50 equal to some 20 to 40 times the ED50) and the prolonged analgesia justified clinical testing. There was no evidence of metabolic or systemic organ system change from any of the clinical laboratory studies.

Adult↗
PubMedDate not supplied

Limitations of the cyanide electrode for use in plasma and whole blood.

Although the cyanide ion-specific electrode has been used for the measurement of cyanide in biologic fluids, its validity has not been documented under these conditions. Therefore, we analyzed 60 paired samples of blood and plasma in a blinded fashion and compared the cyanide ion concentrations obtained from the ion-specific electrode with those obtained from a standard chemical assay. There was poor correlation between results in plasma samples (r = .52, n = 26) and no correlation in whole blood (r = .02, n = 34). Until refinements of the electrode technique are made, this method cannot be recommended for the measurement of cyanide in biologic fluids.

Animals↗