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Biomedical subjects

T E Oh

Publications and source records attributed to T E Oh.

At least 19 recordsLinked to original sources
PubMed1992

Systemic absorption of glycine irrigation solution during endometrial ablation by transcervical endometrial resection.

OBJECTIVE: To study systemic absorption of glycine irrigation solution and its consequences during transcervical endometrial resection (TCER). DESIGN, SETTING, PATIENTS: A prospective study of 20 consecutive female patients who underwent elective TCER in a teaching hospital. METHOD: During the operation, patients were monitored with electrocardiography, automated oscillotonometry, pulse oximetry, capnography and a central venous pressure recorder. Plasma sodium and potassium levels were measured at 15-minute intervals. Blood haemoglobin concentration, serum osmolality, and plasma sodium, potassium and glycine concentrations were measured before and after surgery. RESULTS: Plasma glycine concentration increased in all patients after TCER. The highest concentration recorded was 5575 mumol/L. The increase correlated only with the maximum intraoperative decrease in plasma sodium, which was 7 mmol/L in two patients whose plasma glycine level increased by 3001 mumol/L and 5335 mumol/L. CONCLUSION: Systemic absorption of glycine irrigation solution occurred in all patients during TCER. Serial measurement of plasma sodium was necessary to detect this complication. A decrease in plasma sodium level by 7 mmol/L or more during surgery would indicate fluid absorption that could cause severe hyperglycinaemia and other potential complications.

Absorption↗
PubMed1992

Induction dose-response of propofol in unpremedicated children.

The induction dose requirements of propofol were compared in three age groups in 300 unpremedicated healthy Chinese children: group A, younger than 2 yr (n = 48); group B, 2-5 yr (n = 117); group C, 6-12 yr (n = 135). Patients in each group were allocated randomly to receive one of eight doses of propofol (1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4 and 2.6 mg kg-1). ED50 and ED95 for loss of eyelash reflex (LER) and acceptance of face mask (AFM) were determined using probit analysis. ED50 and ED95 for both LER and AFM were greatest in group A, less in B and smallest in C; ED95 (AFM) for groups A, B and C were 2.88 (2.55-3.36), 2.53 (2.31-2.86), and 2.20 (2.02-2.46) mg kg-1, respectively. This probably represented their effective induction dose. The incidence of apnoea was dose related, but not pain on injection.

Age Factors↗
PubMed1992

Effect of dobutamine on oxygen supply and uptake in healthy volunteers.

We have measured the changes in VO2 and the VO2:DO2 relationship during infusion of dobutamine in healthy volunteers. Nine healthy, adult, non-obese, male physicians were infused with an incremental infusion of dobutamine starting at 2.5 micrograms kg-1 min-1 increasing to 5.0 and then 7.5 micrograms kg-1 min-1 for 15 min each. VO2 and cardiac index were measured every five minutes. VO2I (VO2m-2) increased from a baseline of 128 (SEM 6.1) ml min-1 m-2 to 159 (8.0) ml min1 m-2 (P < 0.05) at the end of infusion with 7.5 micrograms kg-1 min-1. The corresponding changes for DO2I (DO2 m-2) were from 643 (35) ml min-1 m-2 to 1240 (142) ml min-1 m-2 (P < 0.05). The coefficient of correlation for pairs of VO2 and DO2 values, at baseline and each dobutamine infusion in individual subjects, ranged from 0.89 to 0.99 (mean 0.95, SD 0.03). Dobutamine has potent calorigenic effects; demonstration of a positive correlation between VO2 and DO2 after infusion of dobutamine does not necessarily imply an underlying tissue oxygen debt.

Adult↗
PubMed1992

A comparison of omeprazole and ranitidine for prophylaxis against aspiration pneumonitis in emergency caesarean section.

One hundred and sixty-two Chinese women undergoing emergency Caesarean section were allocated at random on admission to the labour ward to receive one of three regimens for orally administered chemoprophylaxis against acid aspiration: ranitidine 150 mg 6 hourly with sodium citrate at induction of anaesthesia, omeprazole 40 mg 12 hourly with sodium citrate, or omeprazole 40 mg 12 hourly alone. Intragastric pH and volume were measured immediately after induction of anaesthesia. Ten patients (17%) in the omeprazole-only group, three (6%) in the omeprazole and citrate group and one (2%) in the ranitidine group had an intragastric pH less than 2.5 and volume greater than 25 ml (p less than 0.05). The use of sodium citrate resulted in higher intragastric pH but larger intragastric volumes (p less than 0.05). The sodium citrate and ranitidine regimen was the most cost-effective among the three.

Cesarean Section↗
PubMed1992

Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes.

Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.

Airway Resistance↗
PubMed1992

Anaesthesia for bullectomy. Use of propofol, high frequency jet ventilation and extradural blockade.

A patient with a single large bulla occupying 50% of the right hemithorax was anaesthetised successfully with a combination of techniques not previously described. The technique consisted of extradural analgesia and intravenous infusion of propofol, while ventilation was maintained with high frequency jet ventilation through a single lumen tracheal tube. The advantages of this technique are a reduced risk of barotrauma, good operating conditions and good analgesia.

Anesthesia, Intravenous↗
PubMed1992

Vecuronium: an anthropometric comparison.

This study set out to determine if there was any resistance to vecuronium in Nepalese studied in Nepal compared with Nepalese, Chinese and European patients studied in Hong Kong. The four groups, each of 10 male and 10 female patients, were intubated 60 s after administration of 0.1 mg.kg-1 vecuronium. The Nepalese patients in Nepal had significantly less satisfactory intubating conditions (p = 0.002). Similarly, male patients had significantly less satisfactory conditions than female patients (p = 0.004). Some anthropometric measurements were significantly different between the patients in Nepal and those in Hong Kong. There were also sex-related anthropometric differences. It is suggested that differences in response to vecuronium could be explained by differences in distribution volume and muscle mass.

Adult↗
PubMed1992

Plasma catecholamine levels following topical application versus infiltration of adrenaline for nasal surgery.

Plasma catecholamine concentrations were measured after vasoconstrictor solutions were administered either by instillation (Moffett's method) or by submucosal infiltration in twenty patients undergoing elective nasal surgery. Following infiltration with 4.4 ml of 1:80,000 adrenaline and 2% lignocaine, plasma adrenaline concentrations increased by 44.3 times to a peak of 9.9 nmol.l-1 (1813 pg.ml-1) within one minute. In contrast the peak level of adrenaline in the patients receiving Moffett's solution containing 1 ml of 1:1,000 adrenaline was 1.27 nmol.l-1 (232 pg.ml-1) occurring 10 minutes after instillation of the solution. The difference in the adrenaline concentrations between the groups was statistically significant (P less than 0.01). The lack of sympathoneuronal response was confirmed by simultaneous measurements of plasma noradrenaline concentrations, which did not change significantly. The operative field was subjectively assessed to be better in the infiltrated patients and the mean operating time and measured blood loss were less in this same group of patients.

Administration, Topical↗
PubMed1992

A clinical evaluation of the Hemocue haemoglobinometer using capillary, venous and arterial samples.

The 'Hemocue' device for rapid estimation of haemoglobin concentration was evaluated in a clinical setting. Repeatable accuracy of capillary, venous and arterial samples was examined and then compared with standard laboratory venous haemoglobin estimates using a 'Coulter JT' analyser in 42 patients. The mean values for haemoglobin (g/l) and coefficient of variation were capillary 108.2 (8.0); venous 104.9 (2.2); arterial 105.9 (2.0); and laboratory venous 104.6 (1.3). Although the mean haemoglobin values were similar, capillary samples were significantly less repeatable than venous or arterial samples (Pitman test, P < 0.001). Comparison of variance between the laboratory sample and each sampling technique demonstrated that capillary samples were significantly more variable than venous or arterial samples. Peripheral skin temperature did not influence the accuracy of capillary samples. Hemocue estimations of venous samples were found to be as accurate as laboratory estimations. The lack of repeatable accuracy of capillary estimations was sufficiently large that their use cannot be recommended in clinical practice.

Adolescent↗
PubMed1991

Plasma catecholamines and oxygen consumption during weaning from mechanical ventilation.

Previous studies on oxygen consumption (VO2) during weaning from mechanical ventilation assumed that an increase in VO2 (delta VO2) reflected oxygen consumption by respiratory muscles (VO2RESP), and proposed delta VO2 as a weaning predictor. We measured VO2 CO2 production (VCO2) and plasma catecholamines in 20 short-term ventilated patients during weaning by SIMV and CPAP. delta VO2 as a percentage of VO2 during spontaneous ventilation (delta VO2%) ranged from 4.8% to 41.5%. VCO2 also increased and correlated with VO2. Plasma adrenaline and noradrenaline increased significantly to levels known to produce considerable increases in metabolic rate. Mean arterial pressure and heart rate concomitantly increased, but spontaneous minute ventilation decreased. Thus, since the increased plasma catecholamines are calorigenic, the assumption that delta VO2 represents VO2RESP is incorrect. Although mean delta VO2% of successfully weaned patients was significantly less than that of failure-to-wean patients, the wide scatter of individual values in the latter group excludes delta VO2% as an accurate weaning predictor.

Adult↗
PubMed1991

Disposition of propofol infusions for caesarean section.

The disposition of propofol was studied in women undergoing elective Caesarean section. Indices of maternal recovery and neonatal assessment were correlated with venous concentrations of propofol. After induction of anaesthesia with propofol 2.0 mg.kg-1, ten patients received propofol 6 mg.kg-1.hr-1 with nitrous oxide 50 per cent in oxygen (low group) and nine were given propofol 9 mg.kg-1.hr-1 with oxygen 100 per cent (high group). Pharmacokinetic variables were similar between the groups. The mean +/- SD Vss = 2.38 +/- 1.16 L.kg-1, Cl = 39.2 +/- 9.75 ml.min-1.kg-1 and t1/2 beta = 126 +/- 68.7 min. At the time of delivery (8-16 min), the concentration of propofol ranged from 1.91-3.82 micrograms.ml-1 in the maternal vein (MV), 1.00-2.00 micrograms.ml-1 in the umbilical vein (UV) and 0.53-1.66 micrograms.ml-1 in the umbilical artery (UA). Neonates with high UV concentrations of propofol at delivery had lower neurologic and adaptive capacity scores 15 minutes later. The concentrations of propofol were similar between groups during the infusion but they declined at a faster rate in the low group postoperatively. Maternal recovery times did not depend on the total dose of propofol but the concentration of propofol at the time of eye opening was greater in the high group than the low group (1.74 +/- 0.51 vs 1.24 +/- 0.32 micrograms.ml-1, P less than 0.01). The rapid placental transfer of propofol during Caesarean section requires propofol infusions to be given cautiously, especially when induction to delivery times are long.

Adult↗
PubMed1991

Resistance of humidifiers, and inspiratory work imposed by a ventilator-humidifier circuit.

The pressures and resistances of a bubble humidifier (Bennett Cascade) and a blow-by humidifier (Fisher and Paykel) were measured and computed at gas flow rates from 4.5 to 100 litre min-1. Pressures increased with flows, with the Bennett pressures being greater at all flows. The resistance of the Fisher-Paykel increased with flows, but remained less than that of the Bennett. An inverse resistance-flow relationship was seen with the Bennett up to a flow of 35 litre min-1. The work of breathing through a Servo 900C ventilator-humidifier circuit was computed, using a lung model. Work was performed by the Servo 900C on the lung, especially with the Fisher-Paykel circuit. The Bennett circuit required considerably greater (3.7 times more) inspiratory work. Thus the Bennett Cascade humidifier may present an unacceptable inspiratory load during spontaneous breathing.

Anesthesiology↗
PubMed1991

Systems analysis applied to intracranial pressure waveforms and correlation with clinical status in head injured patients.

Intracranial pressure waveforms (ICPWF) in head injured patients vary with the nature and severity of injury. Clinical interpretation of ICPWF shape is not defined. Spectral analysis provides an objective method of measuring changes in waveform shape, but the indices most suitable for clinical use remain unknown. Spectral analysis has been applied to ICPWF recorded from 30 patients with head injury, classified on clinical grounds into good, poor and intermediate groups. Normalized indices derived from ratios of certain characteristics of the ICP waveform to those of the arterial pressure (AP) waveform, were different (P less than 0.05) in all groups. A simple index examined was the harmonic count ratio (Nc:Na) which decreased with increasing severity of injury. ICP/AP harmonic transfer functions were derived, and demonstrated a peaked response in the range 10-12 Hz. Increasing attenuation of this peaked response occurred with increasing severity of injury. These results suggest that transfer functions may be a clinically useful index of intracranial conditions.

Blood Pressure↗
PubMed1991

Propofol for induction and maintenance of anaesthesia at caesarean section. A comparison with thiopentone/enflurane.

A propofol infusion regimen and a standard general anaesthetic were compared in 40 Chinese women undergoing elective Caesarean section. Twenty patients received propofol 2 mg/kg for induction of anaesthesia followed by propofol 6 mg/kg/hour, while 20 patients received thiopentone 4 mg/kg with enflurane 1% for maintenance of anaesthesia. All patients were given atracurium and their lungs ventilated with nitrous oxide 50% in oxygen until delivery of the neonate. The hypertensive response after intubation was of shorter duration in the propofol group compared with the thiopentone group. Induction to delivery times ranged from 5 to 14 minutes and neonates from both groups had similar and satisfactory Apgar scores. Neurologic and Adaptive Capacity Scores and umbilical cord blood gas analysis. However, a prolonged propofol infusion time before delivery may cause lower Neurologic and Adaptive Capacity Scores. There were no differences in maternal recovery times or psychomotor performance.

Adult↗
PubMed1991

Inspiratory work imposed by demand valve ventilator circuits.

The inspiratory work (WI) imposed by three commonly used demand valve ventilator circuits was studied using a lung model to simulate spontaneous ventilation. The CPU-1 and Engstrom Erica circuits recorded WI of 379 mJ/l and 190 mJ/l respectively. A negative WI of -32 mJ/l was recorded for the Servo 900C, denoting that the circuit performed work on the lung. The demand valves recorded a time delay between inspiratory effort and onset of gas flow, of 300 ms (CPU-1), 190 ms (Servo 900c) and 160 ms (Engstrom Erica). Both the Servo 900C and Engstrom Erica demand valves were able to generate a high inspiratory gas flow response, but the CPU-1 lacked such a flow compensation. Expiratory work was also greatest with the CPU-1 (156 mJ/l) with 141 mJ/l and 90 mJ/l recorded for the Servo 900C and Engstrom Erica. Of the three ventilators studied, the Servo 900C appears to be the ventilator circuit of choice for spontaneous ventilation.

Humans↗
PubMed1991

Gastric emptying in the postpartum period.

We measured gastric emptying, using the technique of paracetamol absorption, in eight women on their first and third postpartum day. Gastric emptying was rapid and there was no difference between the first and third day in the time to peak plasma concentration of paracetamol. Six women returned after six weeks for a further study. Gastric emptying was still rapid but the metabolism of paracetamol appeared to be slower than that found during the immediate postpartum period. These findings suggest that fluid fasting guidelines in patients more than one day postpartum need not be different from those in non-pregnant patients.

Absorption↗