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Biomedical subjects

M Bloomfield

Publications and source records attributed to M Bloomfield.

11 recordsLinked to original sources
PubMed2003

Effects of midazolam and sarmazenil on the equine electroencephalogram during anaesthesia with halothane in oxygen.

The electroencephalographic (EEG) effects of a rapid infusion of midazolam and sarmazenil following a bolus of midazolam were investigated in eight Welsh mountain ponies anaesthetized with 0.8% halothane in oxygen. The peak plasma concentration of midazolam was 2.13 +/- 0.34 ng/mL (mean +/- SD) occurring 5 min after the start of the infusion. Sarmazenil concentrations were not measured. The 95% spectral edge frequency of the EEG decreased by a maximum of 39.8 +/- 15.8%, 10 min after the start of the midazolam infusion. No changes were seen in median frequency of the EEG or the second differential of the middle latency auditory evoked response. The variability of median frequency (F50) and spectral edge frequency (F95) were reduced by a maximum of 80 +/- 7 and 84 +/- 7%, respectively. The sarmazenil infusion reversed the effects of a bolus of midazolam on the variability of F50 and the magnitude and variability of F95. The second differential of the middle latency auditory evoked potential (DD) was increased by 56.4 +/- 69.3%, 10 min after the start of the sarmazenil infusion. There were no statistically significant differences in EEG variables between the baseline of the midazolam infusion and 10 min after the start of the sarmazenil infusion. Midazolam infusion resulted in specific and unusual changes in the EEG of anaesthetized ponies. These changes were completely reversed by sarmazenil infusion. The data presented suggest that sarmazenil has no intrinsic effect upon the EEG.

Anesthesia↗
PubMed2001

Morphine, pethidine and buprenorphine disposition in the cat.

Pharmacokinetics of morphine, buprenorphine and pethidine were determined in 10 cats. Six cats received morphine (0.2 mg/kg) intravenously and four intramuscularly. Five received buprenorphine (0.01 mg/kg) intravenously and six intramuscularly. Six received pethidine (5 mg/kg) intramuscularly. Jugular venous blood samples were collected at time points to 24 h, and plasma morphine concentrations were measured by high performance liquid chromatograpy (HPLC), buprenorphine by radioimmunoassay (RIA) and pethidine by gas chromatography. Our data for morphine show elimination half-life (t1/2el) 76.3 min intravenous (i.v.) and 93.6 min intramuscular (i.m.); mean residence time (MRT) 105.0 and 120.5 min; clearance (Clp) 24.1 and 13.9 mL/kg/min; and volume of distribution (V(dss)) 2.6 and 1.7 L/kg, respectively. Comparable data for buprenorphine are t1/2el 416.8 and 380.2 min; MRT 417.6 and 409.8 min; Clp 16.7 and 23.7 mL/kg/min; and V(dss) 7.1 and 8.9 L/kg. For i.m. pethidine, t1/2el 216.4 min; MRT 307.5 min; Clp 20.8 mL/kg/min and V(dss) 5.2 L/kg. For i.m. dosing, the tmax for morphine, buprenorphine and pethidine were 15, 3 and 10 min, respectively. The pharmacokinetics of the three opioids in cats are broadly comparable with those of the dog, although there is a suggestion that the cat may clear morphine more slowly.

Analgesics, Opioid↗
PubMed1999

An experimental design approach to the optimisation of a flow injection analysis method for glycine.

A flow injection analysis method for the determination of glycine, based on the reaction with ortho-phtalaldehyde and N-acetylcysteine in a basic buffer, was optimised. In the first step screening of the variables, to select the most important ones, was performed using: (i) a half-fraction factorial design and (ii) a quarter-fraction factorial design, for five factors at two levels. The effects of the factors on the peak height were calculated from both screening designs and compared. For the half-fraction factorial design (resolution IV), the significance of the factor effects on the peak height was checked by: (i) comparing them with a critical effect, calculated from two-factor interactions and based on a t-test, (ii) using a non parametric approach and (iii) drawing a normal probability plot. For the quarter-fraction factorial design (resolution III) the significance of the effects of the factors on the peak height was checked using: (i) a randomization test method, (ii) the non parametric method and (iii) a normal probability plot. In the second step, the factor found to be of importance was optimised using the uniplex method.

Acetylcysteine↗
PubMed1999

Pancreatic alpha cell function in the fetal foal during late gestation.

Plasma glucagon concentrations were measured in chronically catheterized fetal ponies and their mothers between 260 days of gestation and term (approximately 335 days). Fetal alpha cell responses to arginine and variations in fetal glycaemia were also examined during late gestation. Immunoreactive glucagon was present in fetal plasma at 260 days of gestation and its concentration in utero increased after 320 days and then again at birth. Maternal plasma glucagon concentrations were higher after 300 days than earlier in gestation but were lower than the corresponding fetal value throughout the period of gestation studied. Fetal alpha cells responded rapidly to intravenous arginine infusion but not to changes in the fetal glucose level induced by maternal fasting for 36 h or by intrafetal infusion of glucose. The maximal increment in fetal plasma glucagon in response to arginine occurred at the end of the 5 min infusion and was positively correlated to the basal pre-infusion plasma glucagon concentrations. Fetal plasma glucagon concentrations were unaffected by either hyper- or hypoglycaemia. In contrast, maternal plasma glucagon levels were significantly increased by fasting. These observations indicate that equine pancreatic alpha cells are functional in utero but that they are unresponsive to variations in glycaemia until after birth.

Amino Acids↗
PubMed1997

Endocrine changes in cerebrospinal fluid, pituitary effluent, and peripheral plasma of anesthetized ponies.

OBJECTIVE: To investigate the effects of inhalation and total IV anesthesia on pituitary-adrenal activity in ponies. ANIMALS: 9 healthy ponies: 5 geldings and 4 mares. PROCEDURE: Catheters were placed in the cavernous sinus below the pituitary gland and in the subarachnoid space via the lumbosacral space. After 72 hours, administration of acepromazine was followed by induction of anesthesia with thiopentone and maintenance with halothane (halothane protocol), or for the IV protocol, anesthesia induction with detomidine and ketamine was followed by maintenance with IV infusion of a detomidine-ketamine-guaifenesin combination. Arterial blood pressure and gas tensions were measured throughout anesthesia. Peptide and catecholamine concentrations were measured in pituitary effluent, peripheral plasma, and CSF. Peripheral plasma cortisol, glucose, and lactate concentrations also were measured. RESULTS: Intravenous anesthesia caused less cardiorespiratory depression than did halothane. ACTH, metenkephalin, arginine vasopressin, and norepinephrine pituitary effluent and peripheral plasma concentrations were higher during halothane anesthesia, with little change during intravenous anesthesia. Pituitary effluent plasma beta-endorphin and peripheral plasma cortisol concentrations increased during halothane anesthesia only. Dynorphin concentrations did not change in either group. Hyperglycemia developed during intravenous anesthesia only. Minimal changes occurred in CSF hormonal concentrations during anesthesia. CONCLUSION: The pituitary gland has a major role in maintaining circulating peptides during anesthesia. Compared with halothane, IV anesthesia appeared to suppress pituitary secretion.

Adrenocorticotropic Hormone↗
PubMed1991

Intrapleural bupivacaine analgesia in chest trauma: a randomized double-blind controlled trial.

A randomized double-blind study was undertaken to investigate whether 0.25 per cent bupivacaine administered intrapleurally is an effective and reasonably safe method of obtaining analgesia in patients with thoracic injuries. A total of 120 patients complaining of pain after chest injury were entered into the trial. All had thoracostomy tubes already in situ. Of 60 patients who were given the test dose of bupivacaine intrapleurally, 37 obtained satisfactory pain relief for 2 or more hours compared with only 9 of 60 patients who received saline P less than 0.000001). Duration of analgesia in the test group (mean 3.9 h) was significantly longer than that in the control group (mean 0.9 h) P less than 0.005). There were no important side-effects attributable to the bupivacaine administered. We conclude that intrapleural bupivacaine is an effective and reasonably safe method for obtaining analgesia in patients who have chest drain tubes inserted.

Adolescent↗
PubMed1991

Aneuploidy in Drosophila, IV. Inhalation studies on the induction of aneuploidy by nitriles.

The Drosophila ZESTE system was used to monitor the induction of sex chromosome aneuploidy following inhalation exposure of adult females to four nitriles: acetonitrile, propionitrile, acrylonitrile and fumaronitrile. Acetonitrile and propionitrile were highly effective aneuploidogens, inducing both chromosome loss and chromosome gain following brief exposures to low concentrations of these chemicals, and these nitriles also induced rapid paralysis. Acrylonitrile-induced chromosome loss only but did not induce paralysis. Fumaronitrile, in contrast with the results reported in yeast, was ineffective in inducing chromosome loss or gain. Virtually all exceptional offspring induced by acetonitrile and propionitrile were recovered in the first sampled eggs, corresponding to treated mature oocytes. Additionally, the time interval between treatment and sampling was shown to be important, suggesting rapid loss or detoxification of the nitriles. Genetic analysis demonstrated that most aneuploids resulted from induced segregation errors during the first division of meiosis. Cold treatments were found to be ineffective in enhancing the effects of acetonitrile, suggesting important differences between the Drosophila and yeast aneuploidy detection systems. Possible mechanisms by which nitriles may disrupt chromosome segregation in Drosophila oocytes are considered.

Acetonitriles↗
PubMed1986

Sociology of an interstellar vehicle.

The successful functioning of an interstellar flight is dependent on the sociology of the crew. The crew needs to be homogeneous culturally to minimise conflict. A genetically similar crew is suggested as well, in order to provide an initial gene pool for a species differentiation after the establishment of a colony around another star. The goal of interstellar flight should be to extend man or his related descendants throughout the Galaxy and eventually the Universe.

Astronauts↗
PubMedDate not supplied

Effects of ketamine on the equine electroencephalogram during anesthesia with halothane in oxygen.

OBJECTIVE: To investigate the effects of ketamine on the electroencephalogram (EEG) of the horse. STUDY DESIGN: Prospective experimental study. ANIMALS: Eight Welsh mountain pony geldings weighing between 280 and 330 kg, 5 to 9 years old. METHODS: During halothane anesthesia at an end-tidal halothane concentration between 0.75 and 0.85%, the EEG frequency power spectrum and the auditory evoked potential were recorded while an infusion of ketamine was given. Ketamine 200 mg was infused over 5 minutes in 8 ponies. The effects of ketamine on the EEG were recorded continuously during the infusion and for a further 55 minutes. RESULTS: The ketamine infusion produced a plasma ketamine concentration that was significantly greater than the baseline until 7 minutes after the start of the infusion. The highest recorded ketamine concentration was 4.2+/-1.1 microg/ml recorded at 5 minutes after the start of the infusion. The spectral edge and median frequency of the EEG and the midlatency of the auditory evoked potential were compared with those recorded before the start of the infusion. The spectral edge, median frequencies and mid-latency of the auditory evoked potential were reduced by 21+/-13%, 31+/-20% and 19+/-36% respectively (mean +/- SD). Only the reduction in spectral edge frequency reached statistical significance. CONCLUSIONS: These results compared with those from other anesthetic and sedative agents suggest that the spectral edge frequency is an indicator of general central nervous system depression whereas the median frequency may be an indicator of antinociception.

Anesthesia↗