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Biomedical subjects

R Hughes

Publications and source records attributed to R Hughes.

At least 145 records · Page 8Linked to original sources
PubMed1986

Antagonism of atracurium-induced neuromuscular blockade by neostigmine or edrophonium.

Antagonism of atracurium-induced neuromuscular blockade by neostigmine or edrophonium has been studied using the tetanic (50 Hz) and train-of-four (2 Hz) or single twitch responses of the adductor pollicis muscle in 22 anaesthetized patients. A further nine patients not given an anticholinesterase acted as a control group. In two groups (six patients for each anticholinesterase) in whom antagonism was attempted at 95-98% blockade of the tetanic response, recovery of the tetanic response after two or three doses of edrophonium 0.75 mg kg-1 i.v. was not statistically different from that in the control group; recovery after two doses of neostigmine 2.5 mg i.v. was significantly faster (P less than 0.001). Recovery of the single twitch response after antagonism with edrophonium, although longer than that with neostigmine (P less than 0.01), was significantly shorter than in the control group (P less than 0.05). When edrophonium is given at the commencement of recovery, the initial rapid antagonism of tetanic block is not sustained, whereas antagonism by neostigmine is more persistent and the recovery phase is significantly shortened. In a further two groups of patients (n = 5) given atracurium 0.3 mg kg-1 i.v., antagonism was not attempted until the peak height of the tetanic contraction had reached approximately 50% of the control value.(ABSTRACT TRUNCATED AT 250 WORDS)

Atracurium↗
PubMed1986

Recovery of spontaneous breathing following neuromuscular blockade with atracurium.

Atracurium 0.3 mg kg-1 was given to two groups of patients to compare the recovery of spontaneous breathing with that of peripheral neuromuscular function. Anaesthesia was maintained in one group (n = 6) with an infusion of etomidate (mean flow rate 24 micrograms kg-1 min-1) and in the other group (n = 5) with 0.5% halothane. From the time of discontinuing ventilation, about 5 min after the reappearance of the tetanic response, spontaneous breathing returned in an average time of 135 s (range 18-300) in the patients given etomidate and in 68 s (range 0-123) in the patients who received halothane (ns). The duration of action of atracurium was not significantly prolonged by halothane, probably because of the low concentration used. Adequate recovery of respiratory muscle function occurred within 30 min of administration of atracurium at a time when there was less than 25% recovery of the tetanic response of the adductor pollicis muscle. It was concluded that recovery of the muscles of respiration from neuromuscular blockade by atracurium occurred more rapidly than recovery of the muscles of the hand, but an adequate tidal volume in the absence of other clinical signs should not be regarded as a reliable indicator of complete return of neuromuscular function.

Adult↗
PubMed1986

Recovery of respiration following neuromuscular blockade with atracurium and alcuronium.

Eleven fit unpremedicated patients took part in the study. Group I (five patients) received atracurium 0.3 mg kg-1 and group II (six patients) received alcuronium 0.2 mg kg-1. The simultaneous recovery of respiration, judged by serial measurements of the tidal volume and blood-gas values, and peripheral neuromuscular function, judged by the response of the adductor pollicis muscle, were studied. Anaesthesia was maintained with 66% nitrous oxide in oxygen, supplemented by 0.5% halothane. The tetanic response reappeared 17.6 +/- 0.92 min (group I) and 19.2 +/- 2.6 min (group II) after the administration of the drug, and spontaneous breathing at 24.0 +/- 2.08 min (group I) and 23.6 +/- 2.1 min (group II). Adequate recovery of respiratory muscle function was present in group I within 15 min of the onset of spontaneous respiration, whereas in group II this recovery took 30 min. At this time there was marked peripheral neuromuscular blockade with the peak tetanic height value less than 25% of control in both groups. It was concluded that recovery of the respiratory muscles from neuromuscular block by atracurium and alcuronium occurred more rapidly than the recovery of the small muscles of the hand, but that adequate tidal volume, in the absence of other clinical signs, should not be regarded as a reliable indication of complete return of neuromuscular function.

Adolescent↗
PubMed1985

Lipoxene: a new group of trihydroxy pentaenes of eicosapentaenoic acid derived from porcine leukocytes.

Incubation of porcine leukocytes with [1-14C]-15-hydroperoxyeicosapentaenoic acid (15-HPEPE) results in the formation of a group of polar metabolites which after separation and purification by RP-HPLC and SP-HPLC were found to be a series of new compounds containing three hydroxy groups and four conjugated double bonds. The structures of these new metabolites were established by U. V. spectrophotometry and GC/MS to be trihydroxy pentaenes of EPA, i.e., 5,6,15-trihydroxy-7,9,11,13,17-eicosapentaenoic acid and 5,14,15-trihydroxy-6,8,10,12,17-eicosapentaenoic acid. Because of the additional double bond at C17-18, these two new metabolites of EPA were proposed to be lipoxene A and lipoxene B, respectively.

Animals↗
PubMed1985

Use of artificial liver support.

Artificial liver support is used to remove toxic substances accumulating in the circulation of patients with fulminant hepatic failure. Charcoal haemoperfusion with infusion of prostacyclin (PGI2) to prevent platelet damage has become a routine treatment and has led to improved survival. In 76 patients treated 29 (38%) survived to leave hospital and of these 31 patients were treated when in Grade III coma and 20 (65%) survived. Charcoal haemoperfusion also reduced the incidence of cerebral oedema which is a major cause of death in fulminant hepatic failure. Most episodes (congruent to 80%) of cerebral oedema can be managed using the osmotic agent mannitol. In a complete liver support system both protein-bound and compounds of a middle relative molecular mass as well as water soluble compounds should be removed. An albumin-coated resin has been developed to remove these compounds and in preliminary clinical studies it has been shown to have good blood compatibility and satisfactory adsorption properties. The importance of combined systems has been confirmed in studies on the removal of inhibitors of brain Na+K+-ATPase, where both resin and charcoal columns removed significant amounts of the inhibitory activity.

Animals↗
PubMed1984

Experimental and clinical evaluation of neuromuscular blocking agents.

Neuromuscular blocking agents can be evaluated in anesthetized cats, dogs, or rhesus monkeys using dose-response relationships to assess the degree of separation between neuromuscular blocking activity and effects on cardiovascular and autonomic systems. Histamine release can be studied in anesthetized dogs by establishing whether any induced hypotension is reduced by pretreatment with H1 and H2 receptor antagonists. In anesthetized cats, the role of the liver in metabolism is investigated after administration of the drug by the hepatic portal vein and determining whether this "first pass" effect through the liver reduces potency. The involvement of the kidneys in the elimination of the drug can be assessed by ascertaining whether or not the potency and duration of action are enhanced after bilateral renal ligation. In anesthetized man, the simultaneous measurement of the tetanic (50 Hz) and single twitch contractions of the adductor pollicis muscle of the hand has proved a valuable technique for the quantitative assessment of skeletal muscle relaxants. Furthermore, the tetanic response overcomes the relative insensitivity of the single twitch, and tetanic fade provides a measure of the effects of these drugs at presynaptic sites. Cumulative effects may be evident as a prolonged recovery after repeated dosage or after an infusion. The effectiveness of neostigmine as an antagonist should be investigated both from partial and complete block, and recovery of respiration should be compared with that of peripheral neuromuscular blockade.

Animals↗
PubMed1984

Infusion of atracurium for long surgical procedures.

A continuous infusion of atracurium , at an average rate of 0.0061 +/- 0.0003 mg kg-1 min-1 for 128-233 min, to 12 anaesthetized patients undergoing prolonged surgical procedures, provided readily controllable neuromuscular blockade, and good operating conditions. When the infusion was discontinued, full spontaneous recovery from 90-100% blockade in a mean time of 42.2 +/- 3.1 min was as prompt as that after bolus administration of the drug. There was no evidence of recurarization . Induced reversal with neostigmine, preceded by atropine, shortened the recovery time to a mean of 16.4 +/- 2.2 min. It was concluded that the administration of atracurium by infusion was suitable for long surgical procedures.

Adult↗
PubMed1984

Use of atracurium in caesarean section.

Following induction of anaesthesia with methohexitone, and tracheal intubation facilitated by suxamethonium, atracurium 0.3 mg kg-1 was administered to 53 patients undergoing Caesarean section. Surgical relaxation and cardiovascular stability were good. On completion of surgery, recovery from neuromuscular blockade occurred spontaneously in 45 patients and in the remaining eight patients, neostigmine and atropine produced rapid and effective antagonism. There was no evidence of recurarization in any patient. In the neonates there were no adverse effects on Apgar scores or on the time to sustained respiration attributable to the use of atracurium . The drug concentration in the umbilical vein measured in 15 patients indicated that atracurium did not cross the placenta in amounts likely to be of clinical significance.

Adult↗
PubMed1984

Use of atracurium in cardiac surgery involving cardiopulmonary bypass with induced hypothermia.

Atracurium was administered by infusion to 12 anaesthetized patients undergoing cardiac surgery with cardiopulmonary bypass and induced hypothermia. Following an initial bolus dose of 0.6 mg kg-1, an infusion of atracurium was continued at an average rate of 0.0066 +/- 0.0003 mg kg-1 min-1 (0.4 mg kg-1 h-1) which was sufficient to maintain 90-95% block of the single twitch or train-of-four responses before bypass. Adequate surgical relaxation was provided with approximately half the rate of infusion of 0.0034 +/- 0.0003 mg kg-1 min-1 (0.2 mg kg-1 h-1) during cardiopulmonary bypass with induced hypothermia (25-26 degrees C) for 70-166 min. This rate of infusion during hypothermia was significantly slower (P less than 0.001) than that during normothermia. Thus, atracurium appeared to be suitable for use by continuous infusion in cardiac surgery and the temperature-dependent inactivation of atracurium was used to advantage because less drug was required during induced hypothermia.

Adult↗
PubMed1983

Ultrastructural study of motor endings on long chain intrafusal fibers in muscle spindles of the cat.

Five complete poles of long nuclear chain intrafusal fibers of cat tenuissimus muscle spindles embedded in a plastic medium were cut in serial, 1 micron thick transverse sections and stained with toluidine blue. Each fiber pole displayed one plate-type motor ending positioned outside the encapsulated part of the spindle. Ultrastructurally, the endings resembled extrafusal end-plates and were more complex, in terms of prominence of sole-plate and degree of post-junctional folding, than any other motor ending present in the spindles. They were identified as the terminals of static (fast) skeletofusimotor axons, which preferentially innervate the longest nuclear chain fibers of cat spindles.

Animals↗