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Biomedical subjects

H Reyford

Publications and source records attributed to H Reyford.

17 recordsLinked to original sources
PubMed1996

Isoform-dependent effects of halothane in human skinned striated fibers.

BACKGROUND: Reports of the effects of halothane on isoform contractile proteins of striated muscles are conflicting. To determine whether halothane affects cardiac and skeletal contractile proteins differently, the authors examined the effects of two doses of halothane (0.44 and 1.26 mM, equivalent to 0.75 and 2.25 vol%, respectively) on the Ca++ sensitivity and maximal force in human skinned cardiac, type I (slow twitch), and type II (fast twitch) skeletal muscle fibers. METHODS: Left ventricular muscle strips and skeletal muscle biopsy specimens were obtained from eight and ten patients undergoing cardiac and orthopedic surgery, respectively. Sarcolemma and sarcoplasmic reticulum were destroyed with ethylene glycol bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus Brij 58. Ca++ sensitivity was studied by observing the isometric tension developed by skinned fibers challenged with increasing concentrations of Ca++. Muscle fiber type was determined in each skeletal fiber by the difference in strontium-induced tension measurements. RESULTS: Halothane shifted the Ca++ tension curves toward higher Ca++ concentrations and increased the Ca++ concentrations for half-maximal activation in both cardiac and type I skeletal muscle fibers (from 1.96 microM and 1.06 microM under control conditions to 2.92 microM and 1.71 microM in presence of 0.75 vol% halothane, respectively) without changing the slope of this relationship (Hill coefficient). In contrast, no significant effect was observed in type II fibers. Halothane also decreased the maximal activated tension in the three groups of fibers with a lesser effect in type II fibers. CONCLUSIONS: Halothane decreases Ca++ sensitivity and maximal force in human skinned cardiac and type I fibers at 20 degrees C. It is concluded that the negative inotropic effects of halothane depend on contractile proteins isoforms.

Anesthetics, Inhalation↗
PubMed1995

Evaluation of the Augustine Guide for difficult tracheal intubation.

Successful tracheal intubation with Augustine Guide (Augustine Medical, Inc., Eden Prairie, MN) in patients with normal airways has recently been described. There are no studies describing Augustine Guide (AG) use in patients with difficult airways. Accordingly, we studied AG intubation in a population of patients with expected difficult airways due to cervical spine pathology, limited mouth opening, obesity, facial trauma or deformity due to previous operation or radiation and in patients with unexpectedly difficult airways. A total of 44 patients were studied. The AG was used as a primary intubating tool in patients with known difficult airways (n = 36) and as a secondary intubating tool in patients with unexpected inability to intubate using conventional direct laryngoscopy (n = 8). Airway difficulty was predicted by history and physical examination. Intubations were performed under general anaesthesia in 40 of the 44 patients studied. In four patients with predictably difficult airways, topical anaesthesia and sedation were used. Backup methods to achieve intubation were available. Thirty-two of the 36 with known or suspected difficult airways were classified as Mallampati Class III or IV. In the remaining eight patients the preoperative examination suggested an easy airway; however, after induction of general anaesthesia, their laryngeal inlet could not be seen using direct laryngoscopy. Using the AG, all were intubated successfully (36/44 at the first attempt, in 8/44 repositioning of the AG to allow successful laryngeal entry of the stylet was necessary). There were no failures or complications secondary to AG use. This study shows that the AG is a useful device for oral tracheal intubation in patients with known or unexpectedly difficult airways.

Adult↗
PubMed1995

[Cervicofacial cellulitis of dental origin and tracheal intubation].

OBJECTIVES: To evaluate the difficulty of intubation in relation with the localisation and spread of cervico-facial cellulitis of odontogenic origin and to recognize the optimal technique of intubation in such circumstances. STUDY DESIGN: Prospective clinical open study. PATIENTS: Hundred patients, including 16 children, undergoing surgical drainage of a cervico-facial cellulitis of odontogenic origin under general anesthesia were studied. METHODS: Difficulty of intubation was evaluated with the following four criteria: active mouth opening in the awake patient, Mallampati's classifying system, presence of trismus, clinical and radiological control of localisation and extension of the cellulitis (mandibular, maxillar or mouth floor). In case of a foreseen difficult intubation, a fibrescope was used in the awake patient. Otherwise the endotracheal tube was inserted after administration of propofol (3 mg.k-1) and alfentanil (10 to 20 micrograms.kg-1). A Cormack's grading was performed during intubation. RESULTS: Mouth opening depended on the localisation of the cellulitis. Trismus occurred more often with mandibular than maxillary localisations. Trismus and a Mallampati's class > 2 were associated with difficulty in intubation (Cormack's grade > 2), except in maxillary localisations. CONCLUSIONS: The localisation of cellulitis of odontogenic origin is responsible for the difficulty grade of intubation. Awake fibreoptic intubation should be systematically performed in patients with a floor of the mouth cellulitis to reduce the risk of rupture of the abscess by a laryngoscope blade. As trismus associated with mandibular localisations is not relieved by general anaesthesia, awake fibreoptic endotracheal intubation should be preferred.

Adolescent↗
PubMed1994

[Lack of sensitivity to per-anesthetic malignant hyperthermia in 32 patients who developed neuroleptic malignant syndrome].

The aim of this study was to verify whether a relationship exists between neuroleptic malignant syndrome (NMS) and anaesthetic-induced malignant hyperthermia (MH) or not. The in vitro halothane-caffeine tests were performed on muscle tissue obtained from 32 patients with documented NMS episodes. The diagnosis of NMS relied on Levenson's criteria. The results, expressed in accordance with the criteria of the European MH Group, defined 29 subjects as MH non-susceptible. Three patients were classified as MH equivocal. These findings demonstrate the lack of any link between NMS and MH. Therefore, patients with a history of NMS are not likely to be at risk of developing MH and special measures against MH are not required for anaesthesia in these patients.

Adolescent↗
PubMed1994

Intermittent left bundle branch block revealed during anaesthesia.

Intermittent left bundle branch block is uncommon. During anaesthesia,, left bundle branch block may be related to hypertension or tachycardia and its occurrence makes the diagnosis of acute myocardial ischaemia or infarction difficult. Patients with intermittent left bundle branch block often develop established left bundle branch block, which may represent an earlier state of ischaemic heart disease. Cardiological investigation of our patient after operation did not point towards an organic cause of intermittent left bundle branch block.

Aged↗
PubMed1994

Halothane and isoflurane decrease calcium sensitivity and maximal force in human skinned cardiac fibers.

BACKGROUND: Reports of the direct effects of volatile anesthetics on cardiac myofibrils, studied in various mammalian species but not in humans, have conflicted. To determine whether volatile anesthetics directly affect cardiac contractile proteins in humans, we examined the effects of various equianesthetic doses of halothane (0.46, 0.83, and 1.23 mM, equivalent to 0.75, 1.50, and 2.25%, respectively) and isoflurane (0.63, 1.22, and 1.93 mM, equivalent to 1.15, 2.30, and 3.50%, respectively) on the Ca2+ sensitivity and maximal force in human skinned cardiac fibers. METHODS: Left ventricular muscle strips were obtained from seven patients undergoing cardiac surgery. Sarcolemma was disrupted with EGTA (ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid), and sarcoplasmic reticulum was destroyed with EGTA plus BRIJ 58 detergent. Ca2+ sensitivity was studied by observing the isometric tension developed by skinned fiber bundles challenged with solutions of increasing Ca2+ concentrations expressed in pCa (where pCa = -log10[Ca2+]). Maximal force was measured with a pCa 4.8 solution. RESULTS: Both anesthetics shifted the pCa-tension curves toward higher Ca2+ concentrations and decreased pCa for half-maximal activation in a dose-dependent and reversible fashion (from 5.71 for control to 5.56 and 5.55 for 1 MAC halothane and isoflurane, respectively) without changing the slope of this relationship (Hill coefficient). No differences between agents were observed at equianesthetic concentrations. The two agents also decreased the maximal activated tension in a dose-dependent fashion (-27 and -28% vs. control for 2 MAC halothane and isoflurane, respectively). CONCLUSIONS: The current study indicates that halothane and isoflurane decrease Ca2+ sensitivity and maximal force in human skinned cardiac fibers at 20 degrees C. If these effects extend to higher temperatures, they may contribute to the negative inotropic effect of these agents.

Aged↗
PubMed1993

Fiber-type caffeine sensitivities in skinned muscle fibers from humans susceptible to malignant hyperthermia.

BACKGROUND: The response to contracture tests may depend upon the relative proportion of muscle fiber types within the muscle specimen. To determine whether a difference in fiber-type caffeine sensitivities exists between malignant hyperthermia susceptible (MHS) and malignant hyperthermia-nonsusceptible (MHN) skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers dissected from vastus lateralis muscle from 15 MHS and 16 MHN patients. METHODS: Muscle fiber type was determined in each fiber by the difference in strontium-induced tension measurements and in 36 fibers, after contracture testing, by ATPase enzyme histochemistry. Caffeine sensitivity was defined as the threshold concentration inducing more than 10% of the maximal tension obtained with a calcium 1.6 x 10(-2) mM solution. RESULTS: Significant difference in the mean (+/- SD) caffeine sensitivity was found between type I MHS fibers (2.63 +/- 0.85 mM) versus type II MHS fibers (3.47 +/- 1.2 mM) and between type I MHN fibers (5.89 +/- 1.8 mM) versus type II MHN fibers (10.46 +/- 2.6 mM). The mean (+/- SD) caffeine sensitivities for a given muscle fiber type (I or II) were different between groups of MHS and MHN patients. Both type I and II MHS fibers had significantly lower caffeine sensitivities, and this increase in caffeine sensitivity was significantly smaller in type I than in type II fiber. CONCLUSIONS: The current study indicates that a truly MHS patient cannot have a false-negative result solely related to abnormal type II fibers contained in a given muscle strip. Although the occurrence of a very high proportion of type I fibers in MHN human muscle could result in a false-positive contracture outcome, such an occurrence is expected to be rare.

Caffeine↗
PubMed1992

Effect of Bay K 8644 on the magnitude of isoflurane and halothane contracture of skeletal muscle from patients susceptible to malignant hyperthermia.

Isoflurane has a lesser ability than halothane to induce contracture in malignant hyperthermia (MH) muscle in vitro. This does not necessarily imply that isoflurane is not as potent an MH trigger as halothane in vivo. A hypothesis was tested that in vitro treatment with Bay K 8644, an activator of both the dihydropyridine receptors as well as the sodium channels of the T-tubules, potentiates isoflurane-induced MH-susceptible skeletal muscle contracture. In addition to the usual halothane-caffeine test, other muscle bundles were exposed to 10 microM Bay K 8644-halothane and equipotent anesthetic concentrations (expressed in multiple minimum alveolar concentration [MAC]) of isoflurane either alone or combined with Bay K 8644. In 14 MH-susceptible muscle bundles, the mean maximum contracture induced by 2 MAC isoflurane was 0.20 +/- 0.22 g (mean +/- SD), and this value was significantly less than that obtained with 2 MAC halothane (0.68 +/- 0.40 g). Bay K 8644 did not induce muscle contracture on its own but consistently enhanced both the 0.5 MAC isoflurane and halothane to the same maximal isometric tension (1.09 +/- 0.35 g and 1.11 +/- 0.37 g, respectively). Such an effect was not observed in the MH-nonsusceptible group. Under the conditions of this in vitro study, 0.5 MAC isoflurane appears to be as potent as halothane in inducing muscle contracture in skeletal muscle bundles from individuals susceptible to MH.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Effects of calcium-free solution, calcium antagonists, and the calcium agonist BAY K 8644 on mechanical responses of skeletal muscle from patients susceptible to malignant hyperthermia.

The purpose of this investigation was to determine if alteration in the function of the dihydropyridine receptor may in turn modify halothane-induced contractures in muscle bundles from patients susceptible to malignant hyperthermia (MH). The effects of Ca(2+)-free Krebs Ringer (KR) solution, 5 microM verapamil, 5 microM nifedipine, and 10 microM of the Ca2+ agonist BAY K 8644 on halothane-induced contracture were therefore investigated. The halothane-induced contracture was prevented in the absence of extracellular Ca2+ and significantly reduced in the presence of verapamil or nifedipine. BAY K 8644 significantly enhanced the 0.5-, 1.0-, and 1.5-vol % halothane-induced contracture in MH-susceptible muscle bundles. When BAY K 8644 was dissolved in Ca(2+)-free KR solution, no contracture was observed in MH-susceptible muscle bundles. These results on cut MH-susceptible human muscle bundles support the hypothesis that halothane-induced contracture in MH can be modified by the binding of Ca2+ agonists or antagonists to the dihydropyridine receptor. The role of Ca2+ entry phenomena remains unclear, but the results suggest that extracellular Ca2+ is required to reprime or to bind to some sites of the dihydropyridine receptors.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

[Anesthetic technics for the difficult intubation].

Numerous anaesthetic techniques exist for a patient who presents with a difficult endotracheal intubation. They all require an anaesthetic protocol which cannot be improvised. When intubation is expected to be difficult at the pre-anaesthetic examination, the use of a fiberoptic bronchoscope is the technique of choice for intubating adults under local anaesthesia, and children under general anaesthesia. When a fiberoptic bronchoscope is not available, several alternatives can be suggested: local anaesthesia of the glottis, retro-molar and retrograde intubation, or the use of a guide threaded over a lighted stylet; these techniques can be used in an anaesthetized patient breathing spontaneously. In the paralyzed patient impossible to intubate, various trans-laryngeal techniques of ventilation can be used in emergency: jet ventilation via the trans-crico-thyroid route, the use of a cricotomy cannula, or a minitracheotomy set.

Anesthesia↗
PubMed1985

Melanotic meningioma. Report of a case and review of the literature.

Melanotic tumours of the central nervous system constitute a group of expanding lesions whose prognosis is variable, depending upon their histopathological nature. The report of this case of melanotic meningioma finds its interest in the exceptional nature of this type of tumour and in the difficulty of ascertaining whether it is benign or malignant.

Adult↗
PubMedDate not supplied

[Diagnosis of susceptibility to malignant hyperthermia in children].

The realisation and reliability of the halothane-caffeine contracture tests in children to detect the susceptibility to malignant hyperthermia (MH) is still controversial. The present study concerned 26 children aged 2 to 13 years, (mean 9.5 +/- 1.3 years) who were tested either because of a personal symptomatology (14 cases) or as a member of a susceptible MH family (12 cases). Half of the children had a positive test (MHS and MHE) as is found in adults. Furthermore comparison of threshold concentrations of halothane and caffeine as well as the 32 nmol caffeine-induced contractures dit not show significant differences related to age. These results support the possibility to perform under good conditions and with good reliability the diagnostic test of susceptibility to malignant hyperthermia in children from 2 years on.

Anesthesia, General↗