Pre-admission clinic.
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Anesthesia Department, Hospital↗
Biomedical subjects
F Chung
Publications and source records attributed to F Chung.
Circadian rhythm of glycogen in the hamster diaphragm.
The purpose of this study was to determine the diurnal fluctuation of glycogen stores for the whole hemidiaphragm and within a specific myofibrillar ATPase (M-ATPase) fibre type and diaphragmatic region. Fifty-six golden Syrian hamsters were randomly divided into six groups according to the time of sampling biopsies from the diaphragm: 03:00, 07:00, 11:00, 15:00, 19:00, and 23:00. The right hemidiaphragm was quick frozen and biochemically assayed for glycogen levels. Biopsies from the left hemidiaphragm of the same animal were cut from the anterior costal and crural regions, and stained with periodic acid--Schiff (PAS) and for M-ATPase. Optical density measures of PAS-stained fibres were determined to quantitate glycogen in different M-ATPase fibre types and diaphragmatic regions. Biochemical assay of the entire hemidiaphragm showed slightly greater glycogen content of biopsies taken at 11:00 and 15:00 than at 03:00, 19:00, and 23:00 (range of differences: 6.4-10.0%). However, glycogen levels within a specific M-ATPase fibre type and diaphragm region were not different in biopsies sampled at different times. Because the hamster has a small diurnal variation of glycogen in the diaphragm, which is similar to the small diurnal variation of glycogen in human skeletal muscle, this species may be a good animal model for metabolic studies of the diaphragm that could be affected by diurnal glycogen variability.
Adenosine Triphosphatases↗
Supplemental oxygen does not reduce myocardial ischemia in premedicated patients with critical coronary artery disease.
This randomized, prospective clinical study investigated the effects of supplemental inspired oxygen on arterial hemoglobin desaturation and myocardial ischemia in premedicated patients who have critical coronary artery stenosis, identified predictors for these adverse events, and examined the temporal relationship between hemoglobin desaturation and myocardial ischemia. Before elective coronary artery bypass surgery, 104 patients were monitored continuously by using a real-time electrocardiogram (V4 and V5 leads) recorder and a digital pulse oximeter. After a 2-h baseline monitoring period (Interval A), patients were given sublingual lorazepam 0.03 mg/kg, and were randomized to receive continuous supplemental inspired oxygen by nasal catheters [4 L/min (Oxygen Group, n = 52)] or to receive no supplemental inspired oxygen (Control Group, n = 52) (Interval B). One hour later, all patients received intramuscular morphine 0.15 mg/kg with perphenazine 0.05 mg/kg (Interval C). Interval C lasted 1 h, and the study was terminated. In the Oxygen Group, the incidence of desaturation was 25% before premedication and 11.5% after premedication (NS). In the Control Group after premedication, the incidence of desaturation increased from 25% to 56.9% (P < 0.001). There was no significant difference in the incidence of myocardial ischemia before or after premedication within or between the two groups. Arterial hemoglobin desaturation was not associated temporally with myocardial ischemia at any time. Predictors of desaturation after premedication included absence of supplemental O2, increased weight, age, and occurrence of desaturation before premedication. There were no identifiable predictors for myocardial ischemia after premedication. During Intervals A and C, episodes of hemoglobin desaturation were associated with small but statistically significant increases in mean heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
The continuing medical education needs of anaesthetists.
Learning needs assessment is the term applied to the process of identifying or diagnosing a learner's educational needs. It is the foundation of a systematic continuing medical education (CME) programme. Needs assessment has been identified as the most pressing problem of medical education directors in North America. Furthermore, the CME learning needs, interests or motivations of anaesthetists have never been studied. The amount of time and effort required for needs assessment is probably a major deterrent to this activity. The investigators adopted simple and straightforward means of assessing the "perceived learning needs" and topic interests of anaesthetists. Questionnaires were sent by mail to anaesthetists practicing in teaching and non-teaching hospitals in the Toronto area. The questionnaire presented a list of CME content areas. The respondents were asked to indicate on scale of 1 to 10 their Current Expertise, Ideal-Desired Expertise, and Interest-Motivation levels for each content area. Need Score for each content area was calculated by taking the difference between Ideal and Current Expertise responses. A total of 101/305 anaesthetists (29%) responded to the survey. Most of the respondents had been in anaesthesia practice for less than ten years. Regional nerve block, acute pain control, and medicolegal considerations received high overall ranks in both the need and interest categories. Paediatric anaesthesia, anaesthesia for trauma surgery and thoracic anaesthesia had top ranks among the subspecialty fields. Regional anaesthesia techniques received higher need and interest ranks than intravenous and inhalational techniques. The learning needs of anaesthetists of a large urban centre have been identified, and this information is useful to CME planners.
Anesthesiology↗
Preadmission anaesthesia consultation clinic.
Many surgical procedures are delayed or cancelled due to inadequate preoperative assessment and preparation. We describe the case referral pattern and efficiency of our preadmission anaesthesia consultation clinic, which was designed to minimize this problem. Data were collected prospectively on the first 400 patients referred to the clinic. Sixty per cent of referrals were related to the cardiovascular system, in particular coronary artery disease (27%). Eighty-one per cent of referrals were considered appropriate. With ideal functioning of the clinic, delays and cancellations could potentially be reduced to 0.75% and 1.5% of cases respectively. The clinic was well accepted and appreciated by patients. We conclude that this represents a potential important reduction in hospital costs and improvement in operating room efficiency.
Ambulatory Surgical Procedures↗
Postoperative haemodynamic and pharmacological responses in patients with positive technetium pyrophosphate single-photon emission computed tomography following CABG.
The aim of this prospective study was to evaluate the postoperative haemodynamic variables and medication requirements in patients with perioperative myocardial infarction (PMI), following elective coronary artery bypass graft (CABG) surgery, as documented by technetium pyrophosphate scintigraphy using single-photon emission computed tomography (TcPPi-SPECT). A high-dose fentanyl anaesthetic technique was applied. Twelve of 58 patients (21%) developed PMI with an infarcted myocardial mass of 35.7 +/- 3.9 g. Over the 48 hr postoperative period, patients with positive TcPPi-SPECT (n = 12) did not differ from those with negative TcPPi-SPECT (n = 46) in mean heart rate (below 100 bpm), systolic blood pressure (100-120 mmHg) or central venous pressure (8-16 mmHg). However, patients with positive TcPPi-SPECT had higher pulmonary artery diastolic pressures at 5-8 hr after surgery. No differences were found in the incidence and dosage requirements for postoperative sedative or vasoactive drugs (morphine, diazepam, propranolol, lidocaine, nitroglycerin and nitroprusside) between the two groups. There was no difference in the incidence of dopamine requirement between the groups (positive-scan: 16.7%, negative-scan: 13.0%). However, the dopamine dosage for inotropic support was higher in the positive TcPPi-SPECT group over 24 hr (318.5 +/- 125.2 mg vs 71.2 +/- 24.7 mg, P less than 0.05) and 48 hr (869.1 +/- 19.0 mg vs 142.3 +/- 49.4 mg, P less than 0.001) periods after surgery. We postulate that careful control of postoperative haemodynamic variables did not prevent but may limit the extent of PMI in elective CABG patients.
Coronary Artery Bypass↗
Respiratory interaction after spinal anesthesia and sedation with midazolam.
The combined use of midazolam and spinal anesthesia is common in clinical practice. Despite the known potential for each to alter ventilation, the effect of their interaction has not been examined. Nineteen healthy volunteers were studied to assess the impact of intravenous midazolam (0.05 or 0.075 mg/kg), spinal anesthesia (T3-T8; mean level, T6), and their combination on resting ventilation and ventilatory responses to progressive hyperoxic hypercapnia. Resting ventilatory pattern was altered significantly by each condition. Midazolam caused a 29% decrease in resting tidal volume and a 24% decrease in mean inspiratory flow rate, while respiratory frequency increased by 14% and minute ventilation remained unchanged. By contrast, spinal anesthesia alone caused a 32% increase in tidal volume, a 24% increase in mean inspiratory flow rate, and a 13% increase in minute ventilation accompanied by a 14% decrease in respiratory frequency. The combination of midazolam and spinal anesthesia caused a significant decrease in minute ventilation (19%), tidal volume (28%), and mean inspiratory flow rate (27%), all of which were significantly more than the predicted sum of the individual interventions. Midazolam and spinal anesthesia each produced a significant decrease in hypercapnic ventilatory response slope, whereas their combination provoked no net change in hypercapnic ventilatory response slope. Interpretation of the hypercapnic ventilatory response data was complicated by shifts in the position of the ventilatory response curve, particularly under the spinal anesthesia condition. It is concluded that intravenous midazolam depresses resting ventilation, spinal anesthesia stimulates resting ventilation, and their combination has a modest synergistic effect of depressing resting ventilation.
Adult↗
Ventilatory failure induced by tracheal banding in the hamster.
Previous animal models of hypercapnic ventilatory failure are limited in that the resistive load has only been applied acutely and often in anesthetized animals. We therefore developed a chronic animal model of hypercapnic ventilatory failure by increasing airway resistance via tracheal banding over several days. To test the efficacy of this model, we compared arterial blood gases, pulmonary function, and internal area of the trachea 6 days after the banding or sham procedure in 20 hamsters. Six days later, banded animals had an increased airway resistance as indicated by a 66% reduction in internal cross-sectional area of the trachea and a 6.5-fold increase in pulmonary resistance compared with control hamsters. The increased airway resistance resulted in a severe respiratory acidosis and hypoxemia in the awake banded hamsters. Banded hamsters were also hyperinflated. This animal model will be useful for investigating the various mechanisms that contribute to hypercapnic ventilatory failure and interventions that may promote recovery.
Acidosis, Respiratory↗
A comparison of propranolol and diazepam for preoperative anxiolysis.
The effectiveness of propranolol, a nonsedating anxiolytic premedication, was studied by monitoring preoperative anxiety and postoperative recovery of cognitive function in 92 healthy ASA physical status I females aged 15-42 yr undergoing outpatient dilatation and curettage (D&C) for therapeutic abortion. In a randomized double-blind design, patients received one of the following oral medications 1-1.5 hr preoperatively: (1) diazepam 10 mg (n = 31); (2) propranolol 80 mg (n = 31); (3) placebo (n = 30). Anxiety throughout the hospital stay was monitored using the State-Trait Anxiety Inventory (STAI). Postoperative cognitive recovery was assessed using the digit span and Trieger tests. STAI anxiety levels were recorded on admission to hospital, immediately before entering the operating room, and two hours postoperatively. There was no difference among the anxiolytic properties of the three medications and all three patient groups showed a significant decrease in anxiety levels after administration of the medication. Tests of cognitive function after anaesthesia showed the fastest return to baseline status in patients receiving propranolol, possibly because beta adrenergic blockade blunted the autonomic signs of light anaesthesia and less anaesthetic was administered. None of the study premedications was demonstrated to have an anxiolytic advantage, but propranolol did offer a faster return of cognitive function in the postoperative period.
Adolescent↗
Analgesic and pulmonary effects of continuous intercostal nerve block following thoracotomy.
This study examined the beneficial effects and potential systemic toxicity from continuous intercostal nerve block by repeated bolus injections of bupivacaine. In this double-blind, randomized study, 20 post-thoracotomy patients were assigned to receive four doses of either: 20 ml 0.5% bupivacaine with epinephrine 5 micrograms.ml-1 (bupivacaine group, n = 10), or 20 ml preservative-free saline (placebo group, n = 10) through two indwelling intercostal catheters every six hours. Patients receiving intercostal bupivacaine injections had greater decreases in visual analogue pain scores (VAS) (P less than 0.05) and lower 24 hr morphine requirements, 16.6 +/- 4.6 mg vs 35.8 +/- 7.2 mg, than patients in the placebo group (P less than 0.05). Higher post-injection values of forced expiratory volume in one second, forced vital capacity and peaked expiratory flow rate were also observed in the bupivacaine group (P less than 0.01). Repeated intercostal bupivacaine administration did lead to systemic accumulation, but the peak bupivacaine level after 400 mg was low at 1.2 +/- 0.2 microgram.ml-1. Thus, the technique of continuous intercostal nerve block described in this study is an effective treatment for the control of post-thoracotomy pain.
Adult↗
Transoesophageal echocardiogram may fail to diagnose perioperative myocardial infarction.
We report a case in which a 55-yr-old man undergoing aortocoronary bypass was monitored with electrocardiogram and transoesophageal echocardiogram. Intraoperative electrocardiogram and simultaneous ECG recordings using the Holter monitor showed an ST elevation of greater than 2 mm and new Q wave formation in leads AVF and V5 during skin closure. However, the transoesophageal echocardiogram showed no wall motion abnormalities. No significant haemodynamic abnormalities were observed during the period of intraoperative ECG changes. He was treated with nitroglycerin infusion. Confirmation of a perioperative myocardial infarct was documented by postoperative 12-lead ECG and CPK-MB. A post-operative transthoracic echocardiogram showed a hypokinetic left ventricle with an anteroapical infarct. Thus transoesophageal echocardiography failed to detect an apical wall motion abnormality when the probe was placed at the midpapillary level. This limitation can be overcome by periodically obtaining apical views or by using probes with more than one imaging plane.
Aorta↗
Outpatient anesthesia. Which is the best anaesthetic technique?
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Ambulatory Surgical Procedures↗
Muscle and species reactivity of mouse monoclonal antibodies to human eye muscle membrane antigens.
We studied the tissue and species reactivity of mouse monoclonal antibodies (MCAB) produced by immunizing mice with a 100,000g ultracentrifuged preparation of human eye muscle (HEM) membranes. Twenty-three MCABs, 20 of which reacted in an enzyme-linked immunosorbent assay (ELISA) with HEM membrane, 2 with human thyroid membrane, and 1 nonreactive negative control, were selected for the study. The muscle and species specificity of 6 of the most reactive and more restrictively reactive MCAB were studied in more detail. All reacted in ELISA with human skeletal muscle membrane and, to a lesser extent, with human cardiac muscle membrane, but not with human brain membrane. The 6 MCAB cross-reacted with eye muscle membrane prepared from pig but not rat, although reactivity with human tissue was greatest for all MCAB tested. When tested in immunoblotting with HEM and thyroid membranes, 3 of 6 MCAB reacted with a 64-kDa protein in HEM, 2 of which also reacted with an antigen of the same molecular weight in thyroid membrane. In a complement-mediated antibody-dependent cytotoxicity assay, 5 of 19 MCAB lysed HEM cells, 6 of 21 lysed human skeletal muscle cells, and 10 of 22 lysed human thyroid cells. These findings support results from earlier clinical studies which showed that eye muscle membrane reactive autoantibodies in the serum of patients with thyroid-associated ophthalmopathy cross-react with membrane prepared from other striated muscle. The significance of eye muscle, skeletal muscle, and thyroid cross-reactivity of MCAB is discussed in the context of autoimmune thyroid disease and ophthalmopathy.
Abdominal Muscles↗
Low-dose sufentanil and lidocaine supplementation of general anaesthesia.
This randomized double-blind study compared the effects of: (1) saline infusion (C); (2) sufentanil alone (1.0 micrograms.kg-1) (S); and (3) low-dose sufentanil (0.5 micrograms.kg-1) in combination with lidocaine (1.5 mg.kg-1) (LS): on the cardiovascular responses to tracheal intubation and on postoperative ventilation as monitored by respiratory inductive plethysmography in day-care surgical procedures of approximately 60 min duration. Thirty healthy, unpremedicated patients were studied. Thiopentone requirements were reduced by 40 and 28 per cent in the S and LS groups respectively compared with control (P less than 0.001). Both treatments suppressed HR and BP responses (P less than 0.005) to intubation. Postoperatively, PaCO2 was elevated (P less than 0.05) in group S. Dose-related respiratory depression was observed. The incidence of postoperative apnoea was significantly higher in both S and LS groups than compared with control (P less than 0.05). However, only patients in group S showed higher apnoea index and mean apnoea duration over the initial 10-20 min after surgery compared with control (P less than 0.005). In addition, group S showed slower respiratory frequency and prolonged expiratory time (P less than 0.005). In conclusion, an induction dose of sufentanil (1 microgram.kg-1) used in balanced anaesthesia of less than 70 min duration was associated with significant respiratory depression, particularly during the initial 10-20 min after surgery, whereas low-dose sufentanil (0.5 micrograms.kg-1) with lidocaine (1.5 mg.kg-1) had minimal postoperative respiratory depression and comparable attenuation of pressor responses to intubation.
Adjuvants, Anesthesia↗
A randomized comparison of midazolam and diazepam injectable emulsion in cataract surgery.
The purpose of this study was to compare the psychomotor recovery of patients sedated with either midazolam or Diazemuls using the digit symbol substitution test and the Trieger test. Sixty patients were allocated in random double-blind fashion to receive either midazolam or diazepam in oil emulsion (Diazemuls) as intravenous sedation for cataract surgery. Both groups received fentanyl 0.5 micrograms.kg-1 IV. Tests of cognition were performed by the patients prior to sedation and at half-hourly intervals for three hours after cataract surgery. In a dose ratio of 1:4, midazolam was found to produce better sedation but more prolonged recovery than Diazemuls. Anterograde amnesia was comparable in the two groups, while more patients in the Diazemuls group developed episodes of apnoea and venous irritation.
Aged↗
Age-related cognitive recovery after general anesthesia.
This study was designed to quantify the rate of mental recovery in elderly and young patients after general anesthesia for intraabdominal surgery (cholecystectomy). Forty patients (25-83 yr) were given four tests assessing neuropsychological function once preoperatively and on five occasions postoperatively. Two of the four neuropsychological tests showed impairment in scores in the elderly patients on the first postoperative day (Symbol Digit Modalities Test, P less than 0.004; The Trail Making Test, P less than 0.03). In addition, one of the tests (Symbol Digit Modalities Test) showed a deterioration in the younger patients (P less than 0.05). The changes that did occur in these tests on the first postoperative day reverted to baseline levels thereafter. There were no significant changes in the remaining two tests, the Mini Mental State Test or the Digit Span Test, at any time in either group. We conclude that postoperative mental deterioration is no greater in elderly than in young patients.
Adult↗
Does spinal anaesthesia interact with sedation to alter ventilatory responses?
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Adult↗
Pathophysiology and cardiorespiratory consequences of interstitial lung disease--review and clinical implications: a special communication.
The purpose of this special communication is to review the pathophysiology of interstitial lung disease (ILD) and its cardiorespiratory consequences at rest and during exercise. Patients with ILD tend to have a resting and disproportionate exercise tachycardia; resting or exercise-induced arterial desaturation; a rapid shallow breathing pattern; and in more severe cases an increase in pulmonary arterial pressure with an associated increase in right ventricular work. Although the acute exercise responses of patients with ILD have been documented, studies on their responses to exercise training are lacking. We, therefore, discuss some of the physiologic consequences of ILD and the clinical measures available to assess these patients at rest and during exercise. We present the implications of these changes for functional ability and propose that modified endurance training is important to the patient with ILD. Potential directions for clinical research in exercise training of patients with ILD are presented.
Exercise↗