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Biomedical subjects

J E Hall

Publications and source records attributed to J E Hall.

At least 55 records · Page 3Linked to original sources
PubMed2003

Cricoid yoke: the effect of surface area and applied force on discomfort experienced by conscious volunteers.

BACKGROUND AND OBJECTIVE: The application of cricoid force is central to techniques that reduce the risk of gastric regurgitation and the subsequent pulmonary aspiration associated with obstetric and emergency anaesthesia. The discomfort associated with cricoid force in awake preoperative patients increases the incidence of coughing, struggling and pain during induction of anaesthesia. This study determined if increasing the surface area of a cricoid yoke reduced the associated discomfort in volunteers. METHODS: Fifty volunteers participated in a randomized single-blinded study. The cricoid yoke was positioned using standard anatomical landmarks and forces of 10, 20, 30 and 40 N were applied in a random order for 20s, using two different yoke attachments with surface areas of 3 and 10 cm2. A rest of 30s was allowed between the application of forces. Discomfort was graded by volunteers on a scale from 0 to 10 (0: no discomfort; 10: worse discomfort imaginable). A score of 10 was allocated if the volunteers could not tolerate the applied force for 20s. RESULTS: Median scores for the small yoke were always higher than those for the large yoke at each force. There were significant differences between the scores for the small and large yokes at 10 and 20 N (P < 0.001) and 30 N (P = 0.0233), but there was no significant difference at 40 N. CONCLUSIONS: The larger yoke was tolerated better by volunteers when clinically relevant cricoid forces were applied.

Adult↗
PubMed2003

Adverse airway events during brief nasal inhalations of volatile anaesthetics: the effect of humidity and repeated exposure on incidence in volunteers preselected by response to desflurane.

Twelve volunteers known to have airways that responded adversely to 2.0 MAC desflurane were recruited. Each volunteer inhaled three single breaths of each of 0.5, 1.0 and 2.0 MAC of sevoflurane, halothane, isoflurane, desflurane and balance air, with breaths of air between, whilst breathing nasally through a face mask attached to one of three filters that provided three different levels of humidification. The incidence of any adverse airway events was recorded. The anaesthetic inhaled significantly affected the incidence of adverse airway events (p < 0.001), with the least to most irritant being sevoflurane, halothane, isoflurane and desflurane. Increasing the concentration of anaesthetic also significantly increased the incidence of adverse airway events (p < 0.001). The filter used, and hence the level of humidification, did not affect the incidence of adverse airway events (p = 0.09), but repeated exposure caused a significant reduction in the incidence of adverse airway events (p < 0.001).

Adult↗
PubMed2003

An evaluation of the modified Airway Management Device.

We evaluated the modified Airway Management Device (AMDTM) in 60 spontaneously breathing anaesthetised patients. The insertion and removal of the device was very easy and atraumatic. The airway was secured on the first attempt in 41 patients (70%; 95% CI 57-80%). The most important problem was loss of airway, which occurred in 11 patients (19%; 11-30%) during maintenance of anaesthesia. The AMD was dislodged during maintenance in one patient. There was a loss of the airway in 12 patients (20%; 12-31%); in 10, it was maintained with simple airway manoeuvres or a laryngeal mask airway and tracheal intubation was required in two patients. Ten of these patients were male and two were female; the failure rate was 33% (12-31%) among the male patients and 6% (2-22%) among the female patients. The cuff volumes ranged from 4 ml to 80 ml and cuff pressures from 6 cm H2O to 92 cm H2O. Blood was seen on removal in three patients (6%; 2-16%) and nine patients (18%; 10-30%) experienced sore throat after removal of the device.

Adult↗
PubMed2003

The rigid nasendoscope as a tool for difficult tracheal intubation: a manikin study.

We examined the use of the 30 degrees rigid nasendoscope in aiding difficult tracheal intubations. A Cormack and Lehane grade 4 difficult intubation (no view of glottis or epiglottis) was set up on a manikin. After 10 s of tuition, 40 anaesthetists attempted to pass a standard gum elastic bougie between the cords, with and without the nasendoscope, in randomised order. A bougie curved to an 'optimal curve' was also tested. Using the standard bougie 13/40 (33%) passed the bougie between the cords without the nasendoscope, compared with 31/40 (78%) when using the nasendoscope (p < 0.001). The 'optimal curve' bougie resulted in 29/40 (73%) and 39/40 (98%) success rates without and with the nasendoscope, respectively (p = 0.004). The nasendoscope is a simple and easy to use tool in grade 4 intubation, and results are improved further by the use of an 'optimal curve' bougie.

Attitude of Health Personnel↗
PubMed2003

Evaluation of personal, environmental and biological exposure of paediatric anaesthetists to nitrous oxide and sevoflurane.

Paediatric anaesthetists are at higher risk of exposure to waste anaesthetic gases, which often exceed set safety limits. Recommended personal diffusive sampling techniques for monitoring exposure to waste anaesthetic gases may not give a true profile of exposure and hence biological sampling may also be necessary. We evaluated the exposure of paediatric anaesthetists to nitrous oxide and sevoflurane as assessed by personal environmental and biological samples. The influence of venue and technique, and the strength of the relationship among the various sampling techniques were analysed. The study found that exposure to nitrous oxide during paediatric anaesthetic inductions is still a major problem, although exposure to sevoflurane was usually within the accepted limits. The type of breathing system used and the presence of scavenging seem to influence this exposure, though surprisingly, the induction technique or the methods of airway control do not. No significant relationship was found between the various biological indicators measured.

Adolescent↗
PubMed2003

A comparison of the forces exerted during laryngoscopy using disposable and non-disposable laryngoscope blades.

The concern that re-usable equipment may be a source of cross-infection has prompted the increased use of disposable laryngoscope blades. We conducted a study investigating the duration of laryngoscopy and the peak force generated using various laryngoscope blades. Five blades were studied: one reusable Macintosh 3 blade, one disposable metal blade and three plastic disposable blades. Sixty anaesthetists performed laryngoscopy on a mannequin using each of the five blades presented in a random order. This was then repeated with a rigid collar applied to the mannequin. The mean force applied with the collar off with the metal blades was 32.8 and 30.8 N, and with the plastic blades 37.3, 39.6 and 41.5 N, respectively (p < 0.0001). The mean force applied with the collar on with the metal blades was 30.5 and 32.5 N, and with the plastic blades 35.5, 34.9 and 31.4 N, respectively (p < 0.0001). The mean duration of laryngoscopy with the collar off for the metal blades was 5.6 and 5.4 s, and with the plastic blades 10, 7.2 and 7.5 s (p < 0.0001). The duration of laryngoscopy with the collar applied for the metal blades was 7.1 and 7.5 s, and with the plastic blades 11.8, 9.7 and 9.0 s (p < 0.0001). The use of plastic blades results in both greater peak force and duration of laryngoscopy.

Creutzfeldt-Jakob Syndrome↗
PubMed2002

The use of nitrous oxide in anaesthetic practice: a questionnaire survey.

Where practicable, exposure to a hazardous substance should be eliminated or adequately controlled. A postal questionnaire survey was sent to 10% of consultants from the Association of Anaesthetists of Great Britain and Ireland, to identify the level of use of nitrous oxide in current anaesthetic practice and identify any change of practice over the last 5 years. Details of anaesthetic practice were requested in three areas: nitrous oxide usage, availability of medical air on anaesthetic machines and the use of total intravenous anaesthesia. Replies were received from 320 consultants (75%). Of these, 49% felt that, over the last 5 years, their use of nitrous oxide had decreased. Twenty per cent of anaesthetists felt that there should be some restriction in availability of nitrous oxide. Where medical air was available, 32% felt that they would use it frequently. A total of 263 (83%) stated that they use total intravenous anaesthesia to some extent. The results showed that, although 49% of consultant anaesthetists had reduced their use of nitrous oxide, this was due to medical considerations rather than concerns over health and pollution issues arising from the use of nitrous oxide.

Air Pollutants, Occupational↗
PubMed2002

An assessment of the ability of impedance respirometry distinguish oesophageal from tracheal intubation.

Accidental oesophageal intubation is still an important cause of anaesthetic morbidity and mortality. This study investigated the use of impedance respirometry to determine the position of a tracheal tube. Seventy-nine patients undergoing general anaesthesia requiring tracheal intubation with muscle relaxation were recruited to the study. After pre-oxygenation, tracheal tubes were placed in both the oesophagus and trachea; a breathing system was attached to one tube chosen randomly. A blinded observer was required to correctly identify the position of the tube within six tidal ventilations. The position of every tube connected to the breathing system was correctly identified. The median time to correctly identify tracheal and oesophageal tubes was 3 and 5 s, respectively. The median number of breaths to identify tracheal and oesophageal tubes was two for both groups. Every tube position was identified within the required six breaths. Impedance respirometry is a reliable method for diagnosing tracheal tube position.

Adult↗
PubMed2002

Comparison of morphine alone with morphine plus clonidine for postoperative patient-controlled analgesia.

BACKGROUND: Clonidine is an alpha 2 adrenergic agonist with analgesic properties. This study aimed to see if the addition of clonidine to morphine when given by patient-controlled analgesia (PCA) would improve analgesia beyond the first 12 h after surgery. METHODS: Sixty patients undergoing lower abdominal surgery were recruited into a randomized double blind study. At the end of surgery Group C received an infusion of clonidine 4 micrograms kg-1 over 20 min, PCA clonidine 20 micrograms and morphine 1 mg bolus. Group M received an infusion of saline and then PCA morphine 1 mg bolus. Pain, sedation and nausea and vomiting were assessed after 12, 24 and 36 h, and satisfaction with analgesia was assessed at 36 h. RESULTS: Pain scores were significantly lower in Group C between 0 and 12 h, but thereafter there was no difference. Morphine consumption was the same for both groups until 24-36 h. Nausea and vomiting was significantly reduced in Group C between 0 and 24 h. Patients in Group C were significantly happier with their pain relief (four-point scale).

Abdomen↗
PubMed2001

Surgical treatment of congenital kyphosis.

STUDY DESIGN: In this study, 26 cases of congenital kyphosis and kyphoscoliosis treated surgically were retrospectively reviewed. OBJECTIVE: To assess the clinical outcomes and surgical indications for posterior only versus anteroposterior surgery in the child. SUMMARY OF BACKGROUND DATA: Congenital kyphosis usually is progressive without surgical intervention. Current recommended treatment includes posterior arthrodesis for deformities of less than 50 degrees to 60 degrees, and anterior release or decompression, anterior fusion, and posterior instrumented arthrodesis for large deformities and cord compression. METHODS: Cases involving myelodysplasia, spinal dysgenesis, and skeletal dysplasia were excluded from the study. Kyphoscoliosis was included if the kyphotic deformity was greater than the scoliotic deformity. Patients were grouped by age and surgical technique. The patients in group P1 underwent posterior arthrodesis at an age younger than 3 years, and those in group P2 underwent the procedure at an age older than 3 years. The patients in group AP1 underwent anterior and posterior procedures at an age younger than 3 years, and those in group AP2 underwent the procedures at an age older than 3 years. The preoperative deformity, complications, and postoperative deformity correction were analyzed. There were nine Type 1 (failure of formation), nine Type 2 (failure of segmentation), and eight Type 3 (mixed) deformities. Four patients had associated spinal dysraphism. Three patients with Type 1 deformities had clinical or radiographic evidence of cord compression. RESULTS: In Group P1, five patients at an average age of 16 months underwent posterior arthrodesis alone for an average kyphotic deformity of 49 degrees. The immediate postoperative correction improved over a period of 6 years and 9 months by an additional 10 degrees, resulting in a final deformity of 26 degrees. Pseudarthrosis developed in two patients, requiring fusion mass augmentation or anterior arthrodesis. Neither patient was instrumented. In Group P2, five patients at an average age of 13 years and 7 months underwent posterior arthrodesis with instrumentation for kyphotic deformity of 59 degrees. Approximately 30 degrees of intraoperative correction was achieved safely using compression instrumentation and positioning. No further correction occurred with growth. The final residual kyphotic deformity was 29 degrees after a follow-up period of 4 years and 5 months. In Group AP1, seven patients underwent anterior release or vertebra resection for deformity correction and posterior arthrodesis for an average kyphotic deformity of 48 degrees at the age of 16 months. There were no iatrogenic neurologic injuries. The final residual kyphotic deformity was 22 degrees after a follow-up period of 6 years and 3 months. In Group AP2, nine patients underwent anterior release or decompression with posterior arthrodesis for kyphotic deformity of 77 degrees at the age of 11 years and 6 months. The deformity was corrected to 37 degrees, with no significant loss over a follow-up period of 5 years and 2 months. There were two postoperative neurologic complications. CONCLUSIONS: After reviewing their experience, the authors made the following observations: 1) The pseudarthrosis rate was low even without routine augmentation of fusion mass if instrumentation was used; 2) gradual correction of kyphosis may occur with growth in patients younger than 3 years with Types 2 and 3 deformities after posterior fusion, but appears to be unpredictable; 3) the risk of neurologic injury with anterior and posterior fusion for kyphotic deformity was associated with greater age, more severe deformity, and preexisting spinal cord compromise.

Adolescent↗
PubMed2001

Neuroendocrine aspects of aging in women.

In women, the loss of ovarian function at menopause is associated with marked changes in hypothalamic and pituitary function. In addition, the steady decline in serum levels of LH, FSH, and FAS with age following menopause provides clear evidence for age-related neuroendocrine changes independent of the changes occurring owing to loss of ovarian feedback on the hypothalamic and pituitary components of the reproductive axis. An increase in the overall amount of GnRH secreted occurs despite a 30% decrease in GnRH pulse frequency with aging. This observation implies that the amount of GnRH secreted with each secretory bolus is greater in older postmenopausal women when compared with younger postmenopausal women. Thus, there may be a prominent pituitary component to the age-related decline in gonadotropin secretion. Recent studies indicate that the response to estrogen negative feedback at the hypothalamic level is preserved with aging, whereas the response to estrogen positive feedback may decrease with reproductive aging; however, the response to estrogen positive feedback in women has not been investigated with respect to aging, per se. It will be important to determine whether these age-related changes in hypothalamic-pituitary function contribute to reproductive senescence in normal women, as has been suggested for similar changes in animal models.

Aging↗
PubMed2001

Antihypertensive effect of alpha- and beta-adrenergic blockade in obese and lean hypertensive subjects.

The purpose of this study was to determine the contribution of the adrenergic system in mediating hypertension in obese and lean patients. Thirteen obese, hypertensive patients with a body mass index (BMI) > or =28 kg/m2 (obese) and nine lean patients with a BMI < or =25 kg/m2 (lean) were recruited. After a 1-week washout period, participants underwent daytime ambulatory blood pressure monitoring (ABPM). Participants were then treated with the alpha-adrenergic antagonist doxazosin, titrating to 4 mg QHS in 1 week. In the next week, the beta-adrenergic antagonist atenolol was added at an initial dose of 25 mg/day and titrated to 50 mg/day within 1 week. One month after the addition of atenolol, all patients underwent a second ABPM session. There were no differences between the obese and lean subjects in baseline systolic (SBP), diastolic (DBP), or mean arterial pressures (MAP) measured by office recording or ABPM. However, obese subjects had higher heart rates than lean subjects (87.5+/-2.4 v 76.8+/-4.9 beats/min). After 1 month of treatment with the adrenergic blockers, obese patients had a significantly lower SBP (130.0+/-2.5 v 138.9+/-2.1 mm Hg, P = .02) and MAP (99.6+/-2.3 v 107.0+/-1.5 mm Hg, P = .02) than lean patients. Obese patients also tended to have a lower DBP than lean patients (84.3+/-2.5 v 90.9+/-1.6 mm Hg, P = .057), but there was no significant difference in heart rate after 1 month of adrenergic blockade. These results indicate that blood pressure is more sensitive to adrenergic blockade in obese than in lean hypertensive patients and suggest that increased sympathetic activity may be an important factor in the maintenance of hypertension in obesity.

Adrenergic alpha-Antagonists↗
PubMed2001

Obesity hypertension: role of leptin and sympathetic nervous system.

Obesity may account for as much as 65% to 75% of human essential hypertension in most industrialized countries. Excess renal sodium reabsorption and a hypertensive shift of renal-pressure natriuresis play a key role in mediating obesity hypertension. Sympathetic activation contributes to obesity-induced sodium retention and hypertension because adrenergic blockade or renal denervation markedly attenuates these changes. Recent observations suggest that leptin and its multiple interactions with other neurochemical pathways in the hypothalamus may be a partial link between excess weight gain and increased sympathetic activity. Short-term administration of leptin into the cerebral ventricles increases renal sympathetic activity, and long-term intravenous leptin infusions in nonobese rodents at rates that raise plasma concentrations to the levels found in severe obesity increase arterial pressure and heart rate through adrenergic activation. Also, transgenic mice that overexpress leptin develop hypertension. Acute studies suggest that the renal sympathetic effects of leptin may depend on interactions with other neurochemical pathways in the hypothalamus, including melanocortin-4 receptors. However, it is unclear whether this pathway or others, such as neuropeptide Y, mediate the long-term effects of leptin on blood pressure. In addition, leptin has other actions, such as stimulation of nitric oxide formation and enhancement of insulin sensitivity, which may tend to reduce blood pressure in some conditions. Although the precise role of these complex interactions in human obesity has not been elucidated, this is an important area for further investigation, especially considering the current epidemic of obesity in most industrialized countries.

Animals↗
PubMed2001

Rapid hypotensive response to fasting in spontaneously hypertensive rats.

This study examined changes in renal function and mean arterial pressure (MAP) in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats during 48 h of fasting, independent of changes in sodium intake. Spontaneously hypertensive rats (n = 17) and WKY rats (n = 10) were instrumented with artery and vein catheters and sodium intake was clamped at 2.1 mEq/day. By day 2 of fasting, MAP decreased -10+/-1 mm Hg (P < .001) in SHR, but did not change significantly in WKY rats. Heart rate decreased significantly in both groups by day 2 of fasting and there was a significant increase in urine volume and sodium excretion. Thus, fasting caused a rapid decrease in MAP in SHR that was not due to decreased sodium intake, but may be related, in part, to volume loss and improved renal excretory function.

Animals↗
PubMed2001

Body composition and energy balance: lack of effect of short-term hormone replacement in postmenopausal women.

Postmenopausal women (PMW) commonly believe that hormone replacement (HR) leads to weight gain, and fear of weight gain and/or an actual increase in weight is one of the principle reasons evoked for the discontinuation of HR. However, the potential effects of physiologic HR on body composition have yet to be separated from the effects of lifestyle or aging. Therefore, we examined the effect of short-term hormone replacement and age on alterations in weight, body composition, and energy balance. A prospective study of 28 healthy PMW aged 45 to 55 years (younger PMW, studies completed n = 18) and 70 to 80 years (older PMW, studies completed n = 15) was conducted. The last menstrual period was more than 12 months previously. The women had a body mass index (BMI) less than 30 kg/m(2) and were taking no medication. Subjects were studied at baseline, after 1 month of transdermal estrogen (Estraderm, 50 microg/day) administration (E2), followed by a further month of transdermal estrogen with progesterone (100 mg per vagina twice daily) for the final 7 days (E2 + P). Anthropometric measurements and energy assessments were performed at each visit. Physiologic HR was achieved in each subject, and there was no difference between levels achieved in older and younger women. Resting energy expenditure and activity level were positively correlated with fat-free mass (P <.0001), while energy intake was not. Resting energy expenditure was lower in older compared with younger PMW when adjusted for fat-free mass (P <.005). Energy intake was also lower in the older PMW when corrected for fat-free mass (P <.0001); as was activity level (P <.05). There was no effect of hormonal treatment on any of the parameters measured. Changes in weight from baseline for E2 (0.37 +/- 0.25 and 0.61 +/- 0.27 kg in younger and older) and E2 + P (0.11 +/- 0.38 and 0.28 +/- 0.31 kg) were not statistically significant. In addition, there was no difference in BMI, fat mass, fat-free mass, total body water, or waist-to-hip ratio (WHR) between groups or with hormonal treatment. In conclusion, short-term transdermal HR is not associated with significant changes in weight or other anthropometric measures in younger or older PMW. These studies confirm the decrease in energy expenditure that occurs with aging, but indicates that there is no effect of HR on resting energy expenditure.

Aged↗