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Biomedical subjects

F Chung

Publications and source records attributed to F Chung.

At least 55 records · Page 3Linked to original sources
PubMed1998

HIV-specific cytotoxic T-lymphocyte activity in immunologically normal HIV-infected persons.

BACKGROUND: CD8+ T-cell counts usually increase soon after infection with HIV, whereas CD4+ cell counts decrease. The result of these changes in T-cell subpopulation subsets in most HIV-infected subjects is inversion of the CD4 : CD8 ratio from greater than 1.0 typical of uninfected persons to less than 1.0 after infection. SUBJECTS: Six HIV-infected individuals were identified in whom the CD4 : CD8 ratio remained normal throughout follow-up (4.0-11.25 years). They all maintained levels of CD4+ cells above 500 x 10(6)/l and had never received antiretroviral therapy. Because HIV-specific cytotoxic T lymphocytes (CTL) have been implicated in control of HIV during the asymptomatic phase of disease, we screened these individuals for the presence of HIV-specific CTL activity. METHODS: CTL activity was assessed in freshly isolated peripheral blood mononuclear cells (PBMC) and in phytohaemagglutinin-stimulated interleukin-2 expanded cell lines established from PBMC. Cytotoxicity to HIV-1 env, gag, pol and nef gene products was surveyed in a 4 h 51Cr-release assay using autologous Epstein-Barr virus (EBV) transformed B cells infected with vaccinia constructs expressing each of these HIV genes. The immunodominant CTL epitope and MHC class I antigen restriction specificity of HIV-specific CTL was mapped when present. Plasma viral load was assessed by branched DNA assay. Attempts were made to isolate virus from these individuals by the PBMC coculture assay. RESULTS: None of the six immunologically normal HIV-infected (INHI) subjects exhibited direct HIV-specific CTL activity in their freshly isolated PBMC compared with 16 (47%) out of 34 HIV disease progressors (P = 0.03, chi2 test) and one out of 10 seronegative subjects. Three of the six INHI subjects had detectable memory HIV-specific precursor CTL (pCTL) activity in in vitro-activated T-cell lines compared with 25 (73.5%) out of 34 HIV-1 disease progressors and in none out of 10 seronegative individuals. All three INHI subjects had Gag-specific pCTL, and none had reverse transcriptase-specific pCTL. Plasma HIV viraemia in all six INHI subjects was below the level of detection by branched DNA assay (< 500 copies/ml). Virus could not be isolated from four of these individuals despite multiple attempts to do so by PBMC coculture assays. CONCLUSION: Direct HIV-specific CTL activity mediated by activated circulating PBMC was undetectable in six INHI individuals under conditions where it is frequently observed in HIV disease progressors. Despite the absence of cells activated for killing HIV-infected targets in the circulation of these individuals, they appeared able to control their HIV infection by maintaining normal levels of CD4 and CD8 cells and low viral load.

Adult↗
PubMed1998

Unanticipated admission after ambulatory surgery--a prospective study.

PURPOSE: To determine the incidence, the reasons, and the predictive factors for unanticipated admission after ambulatory surgery. METHODS: Preoperative, intraoperative, and postoperative data were collected prospectively on 15,172 consecutive ambulatory surgical patients during a 32-month period. The data were built into a statistical model, and predictive factors were identified and classified. RESULTS: The overall incidence of unanticipated admission was 1.42%. Admitted patients were more likely to be older, male, and ASA status II or III. Duration of anaesthesia was longer, and surgery was more likely to be completed after 3 pm. Length of stay in the Postanaesthesia Care Unit and the Ambulatory Surgery Unit was longer. Surgical reasons were cited in 38.1% of admitted patients; anaesthesia-related reasons were cited in 25%; social reasons accounted for 19.5%, and medical reasons for 17.2%. Ear, nose and throat (ENT) patients had the highest unanticipated admission rate (18.2%), followed by urology (4.8%) and chronic pain block (3.9%). Gynaecological patients had the lowest rate (0.4%). Among the predictive factors found were male, ASA status II and III, long duration of surgery, surgery finishing after 3 pm, postoperative bleeding, excessive pain, nausea and vomiting, and excessive drowsiness or dizziness. CONCLUSION: Earlier operating time for certain surgical procedures, screening for proper support at home, and implementation of clinical pathways to deal aggressively with problems such as pain, nausea and vomiting should decrease the incidence of unanticipated admission.

Ambulatory Surgical Procedures↗
PubMed1998

Pharmacokinetics of doxacurium during normothermic and hypothermic cardiopulmonary bypass surgery.

PURPOSE: To compare the pharmacokinetic behaviour of doxacurium in patients undergoing normothermic or hypothermic cardiopulmonary bypass (CPB) for coronary artery bypass graft surgery. METHODS: Twenty patients in two equal groups were studied. Anaesthesia was induced with sufentanil and midazolam after a standard premedication. Doxacurium was administered at 3 x ED95 (80 micrograms.kg-1), and anaesthesia was maintained with 0.5 microgram.kg-1 hr-1 sufentanil, 0.05 mg.kg-1 midazolam and isoflurane 0.5-1%. Systemic temperature for patients in the normothermic and hypothermic groups was maintained at 33-36 C and 26-30 C respectively. Timed blood and urine samples were collected and pharmacokinetic parameters were estimated using a non-compartmental approach. RESULTS: For the normothermic and hypothermic groups, terminal elimination half-life (t1/2 beta) was 100.1 +/- 28 and 183.8 +/- 60 min (P < 0.05) respectively, elimination half-life during the CPB phase (T1/2 CPB) 114.5 +/- 10 and 183.8 +/- 60 min (P < 0.05), mean residence time 108.8 +/- 25 and 164.8 +/- 34 min (P < 0.05) and apparent volume of distribution at steady state 0.20 +/- 0.03 and 0.26 +/- 0.04 L.kg-1 (P < 0.05). Compared with the hypothermic group, the normothermic group had a higher rate of renal clearance (1.40 +/- 0.4 vs 0.93 +/- 0.3 ml.min-1.kg-1; P < 0.05) and a higher value for renal clearance as a percentage of the total clearance (76.2 +/- 10 vs 58.3 +/- 20%). CONCLUSION: The elimination rate of doxacurium during normothermic CPB is faster than that in hypothermic CPB.

Aged↗
PubMed1998

Predictors of hospital mortality and mechanical ventilation in patients with cervical spinal cord injury.

PURPOSE: The objective of this study was to identify predictors of death and mechanical ventilation in patients with traumatic cervical spinal cord injury. METHODS: From 1981 to 1994, 72 patients with traumatic cervical spinal cord injury resulting in neurological deficits were identified in this retrospective study. For each patient, neurological and associated injuries, physiological variables, complications, hospital mortality and the need for mechanical ventilation were recorded. Univariate and multivariate logistic regression analyses were done to identify predictors of mortality and the need for mechanical ventilation. RESULTS: Fifteen patients (21%) died in the first three months after injury. Univariate analyses identified age, heart disease, neurological level at C4 and above, GCS < or = 13, forced vital capacity and cough, to be associated with mortality. Multivariate logistic regression identified age (P = 0.01), neurological level (P = 0.03) and GCS (P = 0.05) as independent predictors of mortality. In 41 patients (57%), the lungs were mechanically ventilated. Univariate analyses identified. The following predictors of the need for mechanical ventilation: neurological level at C5 and above, complete cord lesions, copious sputum, pneumonia and lung collapse. Multivariate logistic regression identified copious sputum (P = 0.01) and pneumonia (P = 0.01) as independent predictors of the need for mechanical ventilation. CONCLUSION: Age, neurological level and GCS are independent predictors of mortality in patients with traumatic cervical spinal cord injury. Copious sputum and pneumonia are independent predictors of the need for mechanical ventilation.

Adolescent↗
PubMed1998

Topical tetracaine versus topical tetracaine plus intracameral lidocaine for cataract surgery.

PURPOSE: To compare topical tetracaine 0.5% alone and with intracameral lidocaine 1% as a local anesthetic agent in phacoemulsification with intraocular lens (IOL) implantation. SETTING: The Toronto Hospital-Western Division, Toronto, Canada. METHODS: Fifty-nine consecutive patients (60 eyes) having phacoemulsification with implantation of a foldable acrylic IOL (AcrySof) were randomized into 1 of 2 groups: The intracameral balanced salt solution (BSS) group received topical tetracaine 0.5% plus intracameral BSS; the intracameral lidocaine group received topical tetracaine 0.5% with preservative-free intracameral lidocaine 1%. The patients' subjective experience of pain was measured at 4 points during surgery using a 4-point pain scale. Patient and surgeon satisfaction with the anesthesia used was measured using a 5-point satisfaction scale. Central endothelial cell counts were obtained preoperatively and 1 month postoperatively. Best corrected visual acuity (BCVA) was measured preoperatively and 1 hour, 1 day, 1 week, and 1 month postoperatively. RESULTS: The mean pain score after phacoemulsification was significantly higher in the intracameral BSS group than in the intracameral lidocaine group (0.63 +/- 0.7 [SD] and 0.23 +/- 0.4, respectively, P < .019). The mean pain score at the end of surgery was also significantly higher in the intracameral BSS group than in the intracameral lidocaine group (0.60 +/- 0.6 and 0.21 +/- 0.4, respectively; P < .014). The surgeon satisfaction score was significantly lower for the intracameral BSS group than for the intracameral lidocaine group (3.90 +/- 1.2 and 4.73 +/- 0.8, respectively; P < .0007). There was no difference in patient satisfaction between the intracameral BSS and intracameral lidocaine groups (4.60 +/- 0.6 and 4.70 +/- 0.8). Endothelial cell loss 1 month postoperatively was similar between the 2 groups (6.1% +/- 8% and 6.7% +/- 6%). Ninety-seven percent of patients (29/30) in each group noted BCVA improvement from preoperatively. The rate of potential visual acuity recovery was similar in both groups. CONCLUSION: Topical tetracaine 0.5% with intracameral lidocaine was safe and effective in patients having phacoemulsification with IOL implantation. The advantage of using intracameral lidocaine 1% over a placebo was a significant decrease in the patients' subjective experience of pain and in the surgeon's satisfaction with the anesthesia used. None of the other parameters measured in this study differed significantly between the 2 groups.

Administration, Topical↗
PubMed1998

Should adult patients drink fluids before discharge from ambulatory surgery?

UNLABELLED: We studied 726 consenting patients to determine whether withholding oral fluids from adult ambulatory surgical patients before discharge would decrease the incidence of postoperative nausea and vomiting (PONV) and shorten the duration of stay in the ambulatory surgery unit (ASU). Patients were randomly assigned to the drinking or nondrinking group. Both groups received a standard regimen of general anesthesia, fluid replacement, and analgesia. In the ASU, patients in the drinking group were given mandatory oral fluids to drink before discharge. Nausea and pain were assessed by using a visual analog scale 15, 30, 60, 90, 105, 120, 150, and 180 min postoperatively. The time to drink, sit up, void, and ambulate, and the time until discharge were recorded. Patients were interviewed by telephone 24 h postoperatively. There was no significant difference in the frequency of PONV between the drinking and the nondrinking groups either in the hospital or after discharge. Patients in the drinking group required more time to begin ambulating (105 +/- 38 vs 98 +/- 34 min; P < 0.02) and to void (112 +/- 40 vs 105 +/- 37 min; P < 0.01). Patients in the drinking group also stayed in the ASU longer (85 +/- 49 vs 81 +/- 47 min; P < 0.03). Time to postanesthetic discharge was also significantly longer in the drinking group than the nondrinking group (106 +/- 40 vs 98 +/- 36 min; P < 0.015). A similar percentage of patients in both groups were "very satisfied" with their ambulatory surgical care. There was no difference in postoperative complications and need for medical help. Withholding early postoperative oral fluids facilitated earlier ambulation and decreased the stay in the ASU but did not decrease the incidence of PONV. Thus, in this ambulatory surgical population, there does not seem to be justification to require drinking before discharge. IMPLICATIONS: To answer the question of whether adult outpatients should drink before discharge after minor surgical procedures, 726 patients were randomized to either drink approximately 150 mL of liquid or not to drink. Neither drinking nor nondrinking worsened postoperative nausea or vomiting or prolonged hospital stay. Therefore, patients should be allowed to choose whether they drink before discharge.

Adolescent↗
PubMed1998

Programmed atrial sensitivity: a critical determinant in atrial fibrillation detection and optimal automatic mode switching.

Automatic mode switching (AMS) prevents tracking of paroxysmal atrial fibrillation (AF) in dual chamber pacing. The correct detection of AF can be affected by the programmed atrial sensitivity (AS). We prospectively studied the relationship between AS, AF undersensing, and AMS, using unfiltered bipolar intracardiac atrial electrograms recorded from 17 patients during sinus rhythm (SR) and in AF. Overall, 780 rhythms were recorded and replayed onto three dual chamber pacemaker models using different AMS algorithms (Thera DR 7940, Marathon DDDR 294-09, and Meta DDDR 1254), and the ventricular responses were measured. AS was randomly programmed in steps from the highest available AS to half of the mean atrial P wave amplitude (PWA), and the percentage of appropriate AMS responses (defined as a ventricular pacing rate at the expected AMS mode) were recorded. AMS efficacy was related to the programmed AS settings in an exponential manner. At low AS settings, a higher percentage of tests were associated with absence of, or with intermittent AMS and tracking of AF, whereas at higher AS, oversensing of noise during SR occurred. An optimal AS measured approximately 1.3 mV, representing about one-third of the PWA measured during SR, although oversensing of SR and undersensing of AF continued to occur in 14% of tests and time, respectively, due to the high variation in PWA during AF. Thus, a fixed AS cannot eliminate AF undersensing without inviting noise oversensing, suggesting the need for automatic adjustments of AS, or the use of a rate-limiting algorithm to prevent rate oscillation during intermittent AF sensing. In conclusion, AMS functions of existing pacemakers were significantly limited by the undersensing of AF and oversensing of noise. Proper adjustment of the AS is important to enable effective AMS during AF.

Algorithms↗
PubMed1997

Assessment of a new ultrafiltration blood processing system.

PURPOSE: To report our clinical experience with a new blood processing device which uses ultrafiltration. We assessed safety and efficacy by evaluating: 1 ) the quality and the quantity of intraoperative shed blood processed and reinfused to the patient 2) homologous blood requirements 3) clinical status of the patient post-transfusion. METHODS: With Ethics Committee approval, the ultrafiltration device was used in six consenting patients undergoing major elective spinal surgery. Blood samples for haematology and biochemistry tests were collected from patients post-induction of anaesthesia (baseline), 1 hr and 24 hr post-autotransfusion. Volumes of blood collected and processed, and all autologous and homologous transfusions were recorded. Patients were assessed post-operatively for any adverse effects. RESULTS: Five patients had donated blood preoperatively. One patient required homologous blood products in addition to autologous blood. In two patients, the filtration cartridge became blocked and required changing midprocessing. No patient sustained device-related complications. One patient had postoperative haematuria which resolved spontaneously within two hours. CONCLUSION: The ultrafiltration device was safe and effective in reducing homologous blood requirements in six patients undergoing elective spinal surgery. Further evaluation of the ultrafiltration device will be necessary, especially in view of the blockage of the filtration cartridge.

Blood Transfusion, Autologous↗
PubMed1997

Music increases satisfaction in elderly outpatients undergoing cataract surgery.

PURPOSE: Music has long been known to reduce anxiety, minimize the need for sedatives, and make patients feel more at ease. The purpose of the study was to evaluate the effect of music in elderly outpatients undergoing elective cataract surgery with retrobulbar block and monitored anaesthetic care using fentanyl or alfentanil and midazolam. METHODS: One hundred and twenty one patients were prospectively and randomly assigned to hear: relaxing suggestions, white noise, operating room noise or relaxing music via audio-cassette headphones. Vital signs were documented before and after retrobulbar block and every 15 min thereafter. Anxiety was assessed using the State-Trait Anxiety Inventory (STAI) before and after surgery. Visual analogue scales (VAS) were used to assess anxiety and patient satisfaction postoperatively with a standardized questionnaire. Between group comparisons were made using Chi-Square, or ANOVA, where appropriate. RESULTS: There were no differences between groups in STAI or anxiety VAS scores at any time. Differences were noted in systolic blood pressure, but not in other vital signs. Patients' ratings of the whole operative experience, satisfaction with the tape played, general level of relaxation and preference for the chosen tape for subsequent surgery were different (music > relaxing suggestions > white noise and OR noise, P < 0.05). CONCLUSIONS: Elderly patients undergoing cataract surgery under retrobulbar block were more satisfied with their experience if they heard relaxing music, rather than relaxing suggestions or white noise or OR noise. The type of auditory stimuli to which the patients were exposed did not influence the level of anxiety.

Aged↗
PubMed1997

Recall after total intravenous anaesthesia due to an equipment misuse.

PURPOSE: To present a case of recall after total intravenous anaesthesia (TIVA) with propofol-alfentanil infusions to point out an uncommon misuse of the Bard InfusOR syringe driver. CLINICAL FEATURES: A healthy patient underwent diagnostic dilatation and curettage and laparoscopy for lysis of peritoneal adhesions. After induction, anaesthesia was maintained with propofol-alfentanil infusions using the Bard InfusOR syringe drivers. Ten minutes into maintenance, the patient was moving. The flashing green light confirmed delivery of the medication and the alarms were not activated. However, the latch of the movable lever in the propofol syringe driver was found to be improperly positioned at the top of the plunger and only a small amount of propofol had been delivered. Postoperatively, the patient could recall the abdomen being touched during laparoscopy. An explanation was given and the patient was satisfied. CONCLUSION: The Bard InfusOR syringe driver is not designed to detect a malposition of the lever on the syringe plunger. The anaesthetist must ensure proper placement of the lever and visual confirmation of medication delivery in order to prevent awareness due to this particular problem.

Adult↗
PubMed1997

Evaluation of morphine versus fentanyl for postoperative analgesia after ambulatory surgical procedures.

Adequate postoperative analgesia without side effects is necessary to facilitate same-day discharge of ambulatory patients after ambulatory surgery. This study compared the use of intravenous morphine and fentanyl after painful ambulatory procedures with respect to analgesic efficacy, the incidence of side effects, and impact on the patient's readiness for discharge. Fifty-eight patients undergoing ambulatory surgery were prospectively randomized to receive morphine or fentanyl for postoperative analgesia and studied in double-blind fashion. The drugs were administered in equipotent doses in the postanesthesia care unit (PACU) and were titrated against pain scores until a visual analog score < 40 mm was achieved and the patient was satisfied with the level of analgesia. In the ambulatory surgical unit, oral analgesia was available. Pain scores, amount of analgesia used, the incidence of side-effects (nausea and vomiting, sedation and dizziness), the times to achieve recovery milestones, and fitness for discharge were studied. Equal amounts of morphine and fentanyl were used in the PACU, but pain scores were higher in the fentanyl group in the ambulatory surgical unit. In addition, the fentanyl group required more oral analgesia than the morphine group (69% vs 17%; P < 0.0002). The incidence of in-hospital side effects was similar. However, the morphine group had a more frequent incidence of postdischarge nausea and vomiting than the fentanyl group (59% vs 24%; P < 0.016). There was no significant difference in the duration of stay in the PACU (morphine vs fentanyl, 69 +/- 15 min vs 71 +/- 20 min), the times to achieve recovery milestones, and fitness for discharge (morphine vs fentanyl, 136 +/- 41 min vs 132 +/- 40 min). The short duration of fentanyl was not associated with faster discharge times; most patients required additional analgesia to control pain. Morphine produced a better quality of analgesia but was associated with an increased incidence of nausea and vomiting, the majority of which occurred after discharge.

Adult↗
PubMed1997

Remifentanil compared with alfentanil for ambulatory surgery using total intravenous anesthesia. The Remifentanil/Alfentanil Outpatient TIVA Group.

The purpose of this study was to test the hypothesis that using a 1:4 ratio of remifentanil to alfentanil, a remifentanil infusion would provide better suppression of intraoperative responses and comparable recovery profiles after ambulatory laparoscopic surgery than an alfentanil infusion, as part of total intravenous anesthesia. Two hundred ASA physical status I, II, or III adult patients participated in this multicenter, double-blind, parallel group study. Patients were randomly assigned 2:1 to either the remifentanil-propofol or alfentanil-propofol regimens. The anesthesia sequence was propofol (2 mg/kg intravenously [IV] followed by 150 micrograms.kg-1.min-1), and either remifentanil (1 microgram/kg IV followed by 0.5 microgram.kg-1.min-1)of alfentanil (20 micrograms/kg IV followed by 2 micrograms.kg-1.min-1), and vecuronium. After trocar insertion, infusion rates were decreased (propofol to 75 micrograms.kg-1.min-1; remifentanil to 0.25 microgram.kg-1.min-1; alfentanil to 1 microgram.kg-1.min-1). Alfentanil and propofol were discontinued at 10 and 5 min, respectively, before the anticipated end of surgery (last surgical suture); remifentanil was discontinued at the end of surgery. Recovery times were calculated from the end of surgery. The median duration of surgery was similar between groups (39 min for remifentanil versus 34 min for alfentanil). A smaller proportion of remifentanil patients than alfentanil patients had any intraoperative responses (53% vs 71%, P = 0.029), had responses to trocar insertion (11% vs 32%, P < 0.001), or required dosage adjustments during maintenance (24% vs 41%, P < 0.05). Early awakening times were similar. Remifentanil patients qualified for Phase 1 discharge later and were given postoperative analgesics sooner than alfentanil patients (P < 0.05). Actual discharge times from the ambulatory center were similar between groups (174 min for remifentanil versus 204 min for alfentanil) (P = 0.06). In conclusion, remifentanil can be used for maintenance of anesthesia in a 1:4 ratio compared with alfentanil, for total IV anesthesia in ambulatory surgery. This dose of remifentanil provides more effective suppression of intraoperative responses and does not result in prolonged awakening.

Adult↗
PubMed1997

Suprascapular nerve block for postoperative pain relief in arthroscopic shoulder surgery: a new modality?

Arthroscopic shoulder surgery has a 45% incidence of severe postoperative pain. Opiates and interscalene nerve blocks have a high incidence of side effects, and intraarticular local anesthetic has been shown to be ineffective when used for postoperative pain relief. The suprascapular nerve supplies 70% of the sensory nerve supply to the shoulder joint, and local anesthetic block of this nerve is effective in certain shoulder pain disorders. To determine the efficacy of a suprascapular nerve block, subcutaneous saline was compared with a suprascapular nerve block using 10mL of 0.5% bupivacaine with 1:200,000 epinephrine before general anesthesia was induced. In the immediate postoperative period, a 51% reduction in demand and a 31% reduction in consumption of morphine delivered by a patient-controlled analgesic system was demonstrated. There was more than fivefold reduction in the incidence of nausea, as well as reduced visual analog and verbal pain scores for patients who received a suprascapular nerve block. The duration of hospital stay was reduced by 24% in the suprascapular nerve block group. A 24-h phone call interview revealed a 40% reduction in analgesic consumption and a reduction in verbal pain scores at rest and on abduction. There were no complications from the suprascapular nerve block. This study demonstrates that a suprascapular nerve block for pain relief in arthroscopic shoulder surgery is an effective and safe modality of postoperative pain relief.

Adult↗