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Biomedical subjects

D C Sawyer

Publications and source records attributed to D C Sawyer.

14 recordsLinked to original sources
PubMed1992

Topical ocular anesthetics in ocular irritancy testing: a review.

The routine use of topical anesthetics to alleviate discomfort associated with in vivo ocular irritancy testing has been advocated. This review provides information about the adverse effects of topical ocular anesthetics and answers the questions: are topical anesthetics practical and effective in ocular irritancy protocols, is long-term use contraindicated, will topical anesthetics alter the response of a test substance, and are there significant side-effects which might cause pain and suffering in test animals? There was no evidence to support the use of a specific topical anesthetic. Further, information about using systemic analgesics or combinations with local anesthetics that would effectively alleviate discomfort associated with ocular irritancy testing without affecting test results was not found. Comprehensive studies are needed to identify the most effective combination of drugs that would ameliorate discomfort associated with ocular irritation testing.

Administration, Topical↗
PubMed1992

Analgesia and behavioral responses of dogs given oxymorphone-acepromazine and meperidine-acepromazine after methoxyflurane and halothane anesthesia.

This study was designed to test analgesia, duration, and cardiovascular changes induced by meperidine (MEP) and oxymorphone (OXY) following methoxyflurane (MOF) and halothane (HAL) anesthesia. Eight healthy dogs were given atropine and acepromazine, and anesthesia was induced with thiamylal and maintained with 1.5 minimal alveolar concentration of MOF or HAL for 1 hour during controlled ventilation. Eight treatments were given with each anesthetic: 3 with MEP (0.5, 1.0, and 2.0 mg/kg, IV), 3 with oxymorphone (OXY; 0.05, 0.1, and 0.2 mg/kg, IV), and 2 placebos with sterile water. Test drugs were given at the end of anesthesia when early signs of recovery were evident. Minimal threshold stimulus/response nociception was assessed by use of an inflatable soft plastic colonic balloon. Blood pressures and pulse rate were measured with a noninvasive monitor. Meperidine and OXY were found to be effective analgesics and could be reversed with naloxone. Intravenous administration of 2.0 mg of MEP/kg provided analgesia for 36 +/- 6 minutes and 39 +/- 15 minutes after MOF and HAL, respectively. In contrast, OXY was effective at all 3 doses with effects of IV administration of 0.2 mg of OXY/kg lasting 154 +/- 13 minutes and 152 +/- 12 minutes, after MOF and HAL, respectively. Analgesia could not be demonstrated after anesthesia for acepromazine, MOF, or HAL. Blood pressure was not changed by either anesthetic nor was it influenced by MEP or OXY. Pulse rate was significantly depressed by the higher doses of OXY following HAL, but was not changed by MEP following either anesthetic.(ABSTRACT TRUNCATED AT 250 WORDS)

Acepromazine↗
PubMed1991

Dose-response of intravenous butorphanol to increase visceral nociceptive threshold in dogs.

This study was designed to determine the effective analgesic dose of butorphanol administered intravenously to obtund visceral nociception, as well as to determine duration of this effect. Additionally, cardiovascular changes and sedative effects were defined. Eight healthy dogs were each given five doses of butorphanol (0.025, 0.05, 0.1, 0.2, and 0.4 mg/kg) plus a sterile water placebo intravenously in a randomized blinded format. Antinociception was assessed using an inflatable Silastic balloon inserted into the colon. Blood pressures and pulse rates were measured with a noninvasive monitor. The greatest efficacy and longest duration of antinociception were produced by 0.4 mg/kg of butorphanol, with a duration of 38 +/- 9 min. Arterial blood pressure and pulse rate did not vary at antinociceptive doses. Mild sedation was observed at all doses, which generally lasted longer than the antinociceptive effects. These data suggest that butorphanol can be given alone intravenously to provide visceral antinociception lasting 30-45 min without significant side effects.

Animals↗
PubMed1991

Comparison of direct and indirect blood pressure measurement in anesthetized dogs.

This study was conducted to determine whether blood pressures and pulse rate could be determined accurately by indirect measurements from the front and hind legs of 15- to 40-kg dogs anesthetized with isoflurane. Indirect measurements from each animal were compared to direct measurements obtained from a catheter placed into the abdominal aorta via the femoral artery at four ranges of systolic pressure. When systolic pressure was above 80 mm Hg, indirect measurements were either the same as direct measurements or slightly lower. However, when systolic pressures were below 80 mm Hg, indirect systolic pressure measurements were 6 to 15% higher than direct measurements. Larger differences in diastolic pressures were found, which resulted in differences in mean pressure. The most accurate measurements were found when the cuff width-to-limb circumference ratio was between 0.4 and 0.6 and when systolic pressure was between 80 and 100 mm Hg.

Anesthesia↗
PubMed1991

Dose response to butorphanol administered subcutaneously to increase visceral nociceptive threshold in dogs.

Butorphanol (0.025, 0.05, 0.1, 0.2, 0.4, and 0.8 mg/kg of body weight, and placebo) was given SC to 8 healthy unmedicated dogs to determine its efficacy for visceral analgesia, using a colonic balloon for minimal threshold nociceptor stimulation. Degree of sedation; systolic, diastolic, and mean arterial pressure; and pulse rate were recorded. The highest 3 dosages, 0.2, 0.4, and 0.8 mg/kg, were found to be most effective, with 0.8 mg/kg the only dosage that was significantly different from control responses at the 45-minute interval. Duration of analgesia ranged from 23 to 53 minutes for all 6 dosages and dosing durations were not significantly different from one another. Blood pressures did not change, but pulse rate was significantly decreased by 0.8 mg of butorphanol/kg. We concluded that butorphanol is an effective visceral analgesic of relatively short duration in the dog.

Analgesia↗
PubMed1991

Suffering and euthanasia.

Suffering is a powerful but elusive concept in veterinary medicine. Because the companion animal cannot talk, assessment of suffering requires the best judgment of veterinarian, family, and other interested participants. Determining whether euthanasia is appropriate rests on a similar consensus but is based on the entire medical and social situation. Clinicians need skill, sensitivity, and a well-developed sense of timing to uncover what clients really feel and want. Offering the family options, such as to be present during the euthanasia, makes the veterinarian's task easier and helps clients cope.

Animals↗
PubMed1979

Effect of anesthesia on cardiovascular and renal function in the newborn piglet.

The effects of anesthetic agents, nitrous oxide-oxygen, nitrous oxide-oxygen plus ketamine, pentobarbital sodium and halothane, were determined in piglets 6 to 76 hr of age. After observations of cardiovascular and renal function in the unanesthetized state, the drugs were administered and observations were repeated in the anesthetized state. All of the anesthetics caused a decrease in cardiac output and an increase in total peripheral resistance in the newborn piglet. Both nitrous oxide-oxygen plus ketamine and halothane produced a decrease in heart rate while pentobarbital caused an increase and halothane a decrease in systemic blood pressure. Changes in renal function were minimal. Changes in renal blood flow were inconsistent and renal vascular resistance was not modified by any of the drugs. There was little evidence of redistribution of intrarenal blood flow and no significant changes in glomerular filtration rate or sodium excretion. Plasma renin concentration increased after halothane. It was concluded that changes in renal and cardiovascular function due to anesthesia in the newborn were small. Differences between newborn and adult animals may be related to several factors including the state of development of the autonomic nervous system and species differences used in different studies.

Anesthetics↗
PubMed1978

Pathologic changes induced by an euthanasia agent.

Dogs and cats killed by intravenous injection of either 0.3 ml/kg body weight T-61 or 100 mg/kg body weight pentoarbital and necropsied at less than 5 minutes or at 15 minutes after injection did not have gross or microscopic pathological changes. However, dogs and cats killed with T-61 at a dose of 1.0--1.5 ml/kg body weight and necropsied at 15 minutes after injection had significant gross and microscopic pathological lesions. Grossly, the lungs were severely edematous, did not collapse, and were deep red. Microscopically, the lungs had severe pulmonary edema and endothelial necrosis. Endothelial swelling of glomerular tuft vessels was also present. These lung and kidney lesions are classified as an euthanasia artefact.

Amides↗
PubMed1977

Cardiovascular effects of gallamine triethiodide and succinylcholine chloride during halothane anesthesia in the dog.

The cardiovascular effects of gallamine triethiodide and succinylcholine chloride were studied in Beagle dogs during controlled halothane anesthesia. Small but significant increases in heart rate and mean arterial presssure were observed 1 minute after intravenous injection of succinylcholine chloride. Intravenous injection of gallamine triethiodide did not produce significant cardiovascular changes.

Anesthesia, Inhalation↗
PubMed1976

Cardiopulmonary effects of rebreathing and nonrebreathing systems during halothane anesthesia in the cat.

Cardiopulmonary variables were measured in 3 groups of halothane-oxygen anesthetized cats. The groups, each containing 6 animals, were treated similarly except for maintenance anesthetic systems, and system variation was the basis for comparison. Groups were maintained, using a pediatric circle CO2 absorption system with an O2 flow of 0.5 L/minute, an Ayre's T-piece system with an O2 flow of 3 L/minute, and an adult circle CO2 absorption system with an O2 flow of 0.5 L/minute. Anesthesia was induced by mask, endotracheal intubation was done, and end-expired halothane was maintained at 1.4%. Measurements of cardiopulmonary variables were reported at 30-minute intervals for 135 minutes, the first measurements being made 15 minutes after induction. Control data were similar for all groups. Measured variables were not statistically or clinically different among groups, and change from control within groups was related to halothane anesthesia. The 3 systems produced similar cardiovascular and respiratory effects. Consequently, none of the systems proved superior to the other 2 on the basis of measured variables. Halothane anesthesia produced cardiopulmonary changes comparable to changes reported in other species anesthetized and maintained by similar techniques.

Anesthesia, Inhalation↗
PubMed1975

Electroretinography of acute hypoxic and increased intraocular pressure status in the dog.

A model for studying electroretinographic (ERG) responses during controlled hypoxia and acutely increased intraocular pressure (IOP) in dogs is described. The b-wave component of the ERG was critically affected before the a-wave. The critical perfusion pressure (PP) was 45 mm of Hg less than mean arterial blood pressure, and the dog will demonstrate altered b-wave amplitudes at hypoxic values of arterial oxygen pressure (Pao2) 0f 45 torr.

Animals↗
PubMed1975

Cardiopulmonary effects of fentanyl-droperidol, nitrous oxide, and atropine sulfate in dogs.

The cardiopulmonary effects of droperidol-fentanyl, nitrous oxide, and atropine were evaluated in 12 adult male Beagle dogs. All dogs were surgically instrumented with a cardiac output thermistor and arterial and venous catheters and were prepared with a chronic tracheostomy. Each dog was used as its own control, and data obtained when dogs were nonanesthetized and nonmedicated were compared with data recorded after the test drugs were administered. The dogs were randomly allotted to 3 groups of 4 dogs each. Group I dogs were given droperidol-fentanyl alone intravenously (IV); group II dogs were given droperidol-fentanyl IV with 67% nitrous oxide; and group III dogs were given atropine sulfate intramuscularly followed by droperidol-fentanyl IV with 67% nitrous oxide. Minute volume was decreased in the 3 groups of dogs for 3 to 5 minutes after droperidol-fentanyl was injected. This resulted in respiratory and metabolic acidosis in all dogs, as indicated by increased arterial carbon dioxide tension, decreased pH, and increased base deficit. In addition, droperidol-fentanyl given alone caused a decrease in systolic pressure and a slight decrease in heart rate. Group 1 dogs were sensitive to auditory stimulation. Cardiovascular changes were not seen when nitrous oxide was added; however, analgesia and muscle relaxation were improved. Premedication with atropine sulfate resulted in increased cardiac output, heart rate, and diastolic pressure, and subsequent administration of droperidol-fentanyl with nitrous oxide caused a transient increase in mean arterial and systolic pressure. This last anesthetic regimen, along with assisted or controlled respiration, seems to provide an excellent anesthetic state with minimal cardiopulmonary depression.

Analgesia↗
PubMedDate not supplied

Comparative evaluation of a new inhalation anesthetic, BAX-3224, and halothane in Macaca speciosa.

Two groups of 8 monkeys were anesthetized with either BAX-3224, a new fluorinated methyl-propyl ether, or with halothane, 3 hours daily for a total of 30 hours. Vomiting incidence was 12.5 percent with BAX-3224 during both induction and recovery, compared with 3.7 percent for halothane during induction and 7 percent for halothane during recovery. Induction time did not change during the course of study with either agent. Respiration was spontaneous and cardiopulmonary function was stable. Electroretinographic (ERG) responses were consistent, flicker-light responses similar, but visual evoked responses (VER) were not present during BAX-3224 anesthesia. A 33 percent incidence of electroencephalographic (EEG) silence occurred with BAX-3224, which was consistent with absence of VER. Hematologic and serum chemistry values were similar for both agents. Serum fluoride ion concentrations, measured before exposure and 4 times during the 10-day study, did not change after administration of either agent. This finding was significant for BAX-3224, a fluorinated ether. No cardiac arrhythmias were observed during BAX-3224 anesthesia, compared with a 17 percent incidence during halothane induction. Recovery time was 32 minutes following BAX-3224 and 14 minutes after halothane. BAX-3224 produced anesthesia similar to that of halothane, did not induce changes incompatible with recovery from anesthesia, and showed great potential as a new volatile liquid anesthetic agent with excellent biologic stability.

Anesthesia, Inhalation↗