Biomedical subjects

T L Lee

Publications and source records attributed to T L Lee.

At least 73 records · Page 4Linked to original sources

PubMed1994

Repeat epidural caesarean section in a patient with cerebral arteriovenous malformation.

Following a previous uneventful pregnancy and caesarean section, a 27-year-old woman with an untreated cerebral arteriovenous malformation presented again with a second pregnancy. While the cerebral haemodynamics during labour and delivery remain unclear, it is best to avoid Valsalva manoeuvres in women with cerebrovascular disease, and therefore caesarean section is usually the preferred method of delivery. The aim of anaesthetic management for caesarean section in women with cerebrovascular disease is the prevention of hypertension and increase in intracranial pressure. In the absence of decreased intracranial compliance, epidural anaesthesia is recommended because it avoids the haemodynamic stresses of laryngoscopy and rapid sequence intubation. The anaesthetic management of cerebral arteriovenous malformation in pregnancy is summarised.

Adult↗

PubMed1994

Antinociceptive effects of ketamine-opioid combinations in the mouse tail flick test.

The antinociceptive activities of intraperitoneal (i.p.) ketamine in combination with subcutaneous (s.c.) morphine or fentanyl were studied using the mouse tail flick test, an acute pain model. Morphine and fentanyl exhibited dose-dependent effects, with respective ED50s (95% confidence limits) of 1.3 (1.2-1.4) mg/kg and 6.8 (6.2-7.4) mcg/kg. Ketamine (1, 5, 10 and 20 mg/kg) showed relatively weak antinociceptive effects with no apparent dose-response relationship. In mice pretreated with i.p. ketamine 0.1 mg/kg (no effect on the tail flick reaction time) and 1 mg/kg (antinociceptive), the effects of s.c. morphine (1.5 mg/kg) were enhanced but this was significant only at the higher ketamine dose, whereas fentanyl (6 mcg/kg, s.c.) antinociception was significantly enhanced in both pretreatment groups. The antinociceptive effects of i.p. ketamine (10 and 20 mg/kg) were also studied in mice pretreated with s.c. morphine 0.1 and 0.5 mg/kg or fentanyl 0.5 and 2.5 mcg/kg. Morphine dose-dependently enhanced ketamine antinociception, being significant only at the higher pretreatment dose level. Fentanyl (0.5 mcg/kg) pretreatment significantly enhanced ketamine (20 mg/kg) activity, with no apparent effect on ketamine 10 mg/kg. At 2.5 mcg/kg, fentanyl pretreatment significantly enhanced ketamine antinociception. These results suggest that ketamine may not be as effective in acute pain as opioids are, and that after systemic administration, the net effect of ketamine-opioid combination is a simple additive one.

Analgesics↗

PubMed1993

Metabolic profile of patients after elective open heart surgery.

To evaluate the surgical stress of open heart surgery with moderate hypothermic cardiopulmonary bypass (CPB), oxygen consumption (VO2), carbon dioxide production (VCO2), resting energy expenditure (REE), respiratory quotient (RQ), 24 hour-urinary urea nitrogen excretion (UUN), and glucose, fat and protein utilization were determined in 20 patients before and after open heart surgery. Proteins (albumin, prealbumin and transferin) and body weight were measured preoperatively and on 6th postoperative day (POD). Preoperative predicted EE as determined by the Harris-Benedict equation was correlated with measured REE. No significant alteration in VO2, VCO2, REE, 24 hour UUN and protein utilization was observed on the first 6 PODs. RQ decreased significantly on the 1st, 3rd and 4th POD. This was attributed to greater fat utilization due to reduced calorie intake during the early postoperative period. Transport proteins reduced slightly but insignificantly. There was a significant reduction in body weight at the end of the study period due probably to loss of body water. We conclude that patients in the early postoperative period after uneventful open heart surgery are neither hypermetabolic nor hypercatabolic when compared with their stable state before operation.

Journal Article↗

PubMed1993

Tidal volume, lung hyperinflation and arterial oxygenation during general anaesthesia.

Impaired pulmonary oxygen (O2) exchange is common during general anaesthesia but there is no clinical unanimity as to methods of prevention or treatment. We studied 14 patients at risk for pulmonary dysfunction because of increased age, obesity, cigarette smoking, or chronic lung disease. Pulmonary O2 exchange was measured during four conditions of ventilation: awake spontaneous, conventional tidal volume (CVT, 7 ml.kg-1) or high tidal volume (HVT, 12 ml.kg-1) controlled ventilation, and five min after manual hyperinflation (HI) of the lungs. The FIO2 was controlled at 0.5, and FETCO2 was kept constant by adding dead space during HVT. Eight patients were ventilated with N2O/O2 and six with air/O2. Arterial blood gases were used to calculate the (A-a)DO2. In seven patients (A-a)DO2 worsened after induction of anaesthesia, while in seven there was no change or an improvement. Manual HI significantly reduced (A-a)DO2, but changing tidal volume (VT) had no effect. Using a multivariate model to predict O2 exchange, obesity and type of surgery were significantly associated with worsening, while level of VT and inspiratory gas (N2O or N2) were not significant predictors. Thus patient and surgical factors were more important determinants of pulmonary gas exchange during anaesthesia than were tidal volume or inspiratory gas. Manual HI is a simple and effective manoeuvre to improve gas exchange.

Adult↗

PubMed1993

Stress-relaxation of fibroblasts in collagen matrices triggers ectocytosis of plasma membrane vesicles containing actin, annexins II and VI, and beta 1 integrin receptors.

To learn about the effects of tension on fibroblast function, we have been studying initial cellular responses to stress-relaxation. Human foreskin fibroblasts were cultured in anchored collagen matrices for 2 days, during which time mechanical stress developed. Subsequently, the matrices were dislodged; thereby allowing stress to dissipate. Within 5 min after initiating stress-relaxation, fibroblasts retracted their pseudopodia. At this time, we observed the disappearance of cellular stress fibers and the formation of actin clusters along the cell margins. The actin was found to be located inside 200 nm diameter vesicles that were budding from the cell surface. Vesicles isolated from the matrix after stress-relaxation contained prominent 24 kDa, 36 kDa (doublet), 45 kDa, and 135 kDa polypeptides. The 45 kDa polypeptide was the major component in the Triton-insoluble vesicle fraction and appeared to be actin. The 36 kDa (doublet) polypeptide, which was found predominantly in the Triton-soluble vesicle fraction, was identified as annexin II. Vesicles also contained annexin VI and beta 1 integrin receptors but not tubulin, vimentin, vinculin or annexin I. The results suggest that stress-relaxation of fibroblasts induces a novel ectocytotic process involving transient budding of intact, plasma membrane vesicles from the cell cortex. On the basis of their morphological and biochemical features, these vesicles may be analogous to the 'matrix vesicles' released by chondrocytes and could play a role in extracellular matrix remodeling after wound contraction.

Actins↗

PubMed1992

Carbon dioxide absorption and gas exchange during pelvic laparoscopy.

Twelve ASA physical status I-II patients undergoing pelvic laparoscopy for infertility were enrolled in a study to quantify the effects of CO2 insufflation and the Trendelenburg position on CO2 elimination and pulmonary gas exchange, and to determine the minute ventilation required to maintain normocapnia during CO2 insufflation. Measurements of O2 uptake (VO2), CO2 elimination (VCO2), minute ventilation (VE), FIO2, and respiratory exchange ratio (RQ) were made during three steady states: control (C) taken after 15 min of normoventilation but before CO2 insufflation, after 15 min (L1) and 30 min (L2) of hyperventilation during CO2 insufflation. The FIO2 was controlled at 0.5 and arterial blood gases were used to calculate the oxygen tension-based indices of pulmonary gas exchange. After 15 min and 30 min of CO2 insufflation, the volume of CO2 absorbed from the peritoneal cavity was estimated at 42.1 +/- 5.1 and 38.6 +/- 6.6 (SEM) ml.min-1 respectively, increasing CO2 elimination through the lungs by about 30%. Hyperventilation of the lungs by a 20-30% increase in minute ventilation maintained normocapnia. Despite the CO2 pneumoperitoneum and Trendelenburg position, there was no impairment of pulmonary oxygen exchange as estimated by (A-alpha)DO2. This study demonstrated that a 30% increase in minute ventilation, achieved by increasing tidal volume to more than 10 ml.kg-1, is sufficient to eliminate the increased CO2 load and maintain normal pulmonary O2 exchange during pelvic laparoscopy.

Absorption↗

PubMed1992

Malignant rhabdoid tumor arising from soft parts of the right thigh with unusual neurologic manifestation: report of a case.

A case of malignant rhabdoid tumor (MRT) arising from the soft tissue of the right thigh in a 49-year-old Chinese female with peripheral neuropathy is reported. The tumor, exhibiting the salient features of MRT, was composed of sheets and nests of polygonal cells with prominent nucleoli and characteristic paranuclear inclusion-like hyaline globules under light microscopy which corresponded to aggregates of intermediate filaments under electron microscopy. The results of immunohistochemical studies of the tumor cells were also characteristic: cytokeratin (+), vimentin (+), epithelial membrane antigen (EMA) (+), desmin (-), myoglobin (-), leukocyte common antigen (LCA) (-), kappa (-), lambda (-), IgG (-) and IgA (-). Serologic study revealed an M-component of IgA. The clinical evolution of the patient was highly aggressive and inevitably lethal. An adult malignant rhabdoid tumor is unusual, and its association with peripheral neuropathy and the coexistence of an M-component of IgA in this case appears to be unique. In this report, the differential diagnosis of histopathologic features, the association of peripheral neuropathy and the coexistence of an M-component of IgA are discussed.

Female↗

PubMed1992

Oxygen consumption and carbon dioxide elimination after release of unilateral lower limb pneumatic tourniquets.

Oxygen consumption (VO2), carbon dioxide elimination (VCO2), and respiratory exchange ratio (RQ) were continuously measured in 15 male and 15 female adults during knee surgery, with the leg exsanguinated by an inflatable tourniquet around the thigh. Arterial blood was also intermittently sampled for blood gas analysis, electrolytes, and lactate content before and after tourniquet deflation. There was a significant increase in VO2 and VCO2 after tourniquet deflation, which was more pronounced in the male (aged 29.5 +/- 14.8 yr, mean +/- SD) than the female (aged 56.9 +/- 15.6 yr) patients, both in terms of maximal increase (P less than 0.001) and percent of increase from values before deflation (P less than 0.001 and P = 0.01). The body weights and tourniquet inflation times were not significantly different between the male and female patients. Excess VO2 (O2 debt) and excess VCO2 over 12 min after deflation of the tourniquet were also significantly higher for male (593.5 +/- 222.9 mL and 714.9 +/- 463.8 mL, respectively) than for female patients (302 +/- 73.3 mL and 196 +/- 162.22 mL, respectively; P less than 0.01). There was no correlation between the duration of tourniquet inflation time and peak increase in VO2, peak increase in VCO2, and O2 debt over 12 min after deflation of the tourniquet; however, tourniquet time was weakly correlated with excess VCO2 over 12 min after tourniquet deflation (r = 0.55, P = 0.002). There was a significant decrease in pHa (P less than 0.001) from release of PaCO2 and lactate after tourniquet deflation. Plasma potassium levels also increased significantly after tourniquet release (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Time-cycled inverse ratio ventilation does not improve gas exchange during anaesthesia.

Inverse ratio ventilation (IRV) has been reported to improve oxygenation at lower peak airway pressures in patients with respiratory failure. Therefore we hypothesised that IRV might also improve oxygen exchange during anaesthesia. Conventional ratio ventilation (CRV) and IRV were compared in 24 low-risk surgical patients who were paralysed and whose lungs were ventilated with air/O2 by a non-rebreathing circuit and a Siemens 900-C servo ventilator. Two levels of time-cycled IRV (I:E ratios of 60/40 and 77/23) were bracketed by control periods with CRV (I:E ratio of 35/65). Inspired O2 fraction, O2 uptake and CO2 elimination, arterial blood gases, pulmonary ventilation and mechanics, heart rate and blood pressure were measured. From these data alveolar and dead space ventilation and four oxygen tension-based indices of gas exchange were calculated. During IRV, mean airway pressure (mean AWP) was increased but there were no changes in oxygen exchange indices, pulmonary mechanics, HR or BP. A sub-set of the sample with moderately impaired oxygen exchange, defined as the upper quartile for (A-a)DO2, was examined separately with identical results. Multivariate models were tested to identify variables which predicted O2 exchange during CRV. Patient age was the only predictor consistently significant in all models. We conclude that age is an important determinant of impaired pulmonary oxygen exchange during anaesthesia, and that increasing mean AWP by TC-IRV has no beneficial effects on pulmonary mechanics or gas exchange.

Adolescent↗

PubMed1991

Tussive effect of a fentanyl bolus.

The aim of this study was to investigate the incidence of pre-induction coughing, after an iv bolus of fentanyl. The study sample was 250 ASA physical status I-II patients, scheduled for various elective surgical procedures. The first 100 were randomly allocated to receive 1.5 micrograms.kg-1 fentanyl via a peripheral venous cannula (Group 1), or an equivalent volume of saline (Group 2). Twenty-eight per cent of patients who received fentanyl, but none given saline, coughed within one minute (P less than 0.0001). The second 150 patients were then randomly assigned to three equal pretreatment groups. Group 3 received 0.01 mg.kg-1 atropine iv one minute before fentanyl. Groups 4 and 5 received 0.2 mg.kg-1 morphine im, and 7.5 mg midazolam po, respectively, one hour before fentanyl. Thirty per cent of patients in Group 3, 6% in Group 4, and 40% in Group 5, had a cough response to fentanyl. Fentanyl, when given through a peripheral cannula, provoked cough in a considerable proportion of patients. This was not altered by premedication with atropine or midazolam, but was reduced after morphine (P less than 0.01). Coughing upon induction of anaesthesia is undesirable in some patients, and stimulation of cough by fentanyl in unpremedicated patients may be of clinical importance.

Adult↗

PubMed1991

Large tidal volume ventilation improves pulmonary gas exchange during lower abdominal surgery in Trendelenburg's position.

Impaired pulmonary gas exchange is a common complication of general anaesthesia. Periodic hyperinflation of the lungs and large tidal volume ventilation were the first preventive measures to be widely embraced, but their effectiveness in clinical practice has never been clearly established by controlled clinical studies. To assess their effects in high-risk patients we studied 24 adults having lower abdominal gynaecological surgery in the Trendelenburg (head down) position. Pulmonary oxygen exchange was determined during four steady-states: awake control (AC), after 30 min of conventional tidal volume (CVT, 7.5 ml.kg-1) or high tidal volume (HVT, 12.7 ml.kg-1) ventilation, introduced in random order, and five minutes after manual hyperinflations (HI) of the lungs. The patients' lungs were ventilated with air/O2 by an Ohmeda volume-controlled ventilator via a circle system. The FIO2 was controlled at 0.5, and FETCO2 was controlled by adding dead space during HVT. Arterial blood gas analysis was used to calculate the oxygen tension-based indices of gas exchange. There was significant deterioration of (A-a)DO2 at 30 min in Group A, whose lungs were first ventilated with CVT (81.6 +/- 7.2 to 166.8 +/- 13.7 mmHg, P less than 0.001); but not in Group B, whose lungs were first ventilated with HVT (77.0 +/- 9.9 to 104.4 +/- 16.8 mmHg). When Group A and B data were pooled there was no difference between randomized CVT and HVT, but improvement occurred after HI. In this model of compromised O2 exchange large inflation volumes (HVT and HI) were of considerable clinical benefit, HVT prevented and HI reversed the gas exchange disorder.

Abdomen↗

PubMed1991

Prevention of succinylcholine-induced myalgia with lidocaine pretreatment.

We studied the effects of 3 mg.kg(-1) lidocaine iv on the succinylcholine (SCh)-induced myalgia in 94 unpremedicated ambulant patients undergoing dilatation and curettage of the uterus. The post-SCh myalgia was confirmed through interview by telephone. The data were correlated with the degree of fasciculation and changes in the serum electrolytes and creatine kinase (CK) levels following SCh administration. Pretreatment with lidocaine, 3 mg.kg(-1) iv, significantly reduced the incidence of myalgia from 40.4% of control group to 12.8% lidocaine-treated group, but not the CK levels. The severity of myalgia was not related to the intensity of fasciculation assessed by visual observation. The pretreatment with lidocaine had no untoward effect on the circulation, although the peak arterial and peak venous lidocaine levels achieved were 29.6 +/- 23 micro g.ml(-1) and 10.1 +/- 3.3 micro g.ml(-1) respectively. These finding indicated that the pretreatment with lidocaine, 3 mg.kg(-1) iv, was effective in prevention of SCh-induced myalgia.

Journal Article↗

PubMed1991

Haemodynamic effects of ketanserin following coronary artery bypass grafting.

The haemodynamic effects of ketanserin were studied consecutively in seventeen patients in the intensive care unit following coronary artery bypass grafting. Hypertensive patients (Group 1, systolic blood pressure (SBP) greater than or equal to 150 mmHg following discontinuation of nitroprusside, n = 10) received intravenous ketanserin 10 mg and infusion of 0.1 mg.kg-1.hr-1 with additional boluses as required to maintain SBP less than or equal to 130 mmHg for one hour. Non-hypertensive patients (Group 2, SBP less than 150 mmHg, n = 7) received a 5 mg bolus and the same infusion. Ketanserin significantly decreased arterial blood pressure (P less than 0.001) in all patients in Group 1. Heart rate was decreased but not significantly. Cardiac index, systemic and pulmonary vascular resistance and pulmonary shunt fraction were not significantly altered from pre-ketanserin values when blood pressure was controlled with nitroprusside. Normotensive patients in Group 2 did not show any undesirable hypotension or significant haemodynamic changes. Mean nitroprusside dose requirements following ketanserin therapy were significantly reduced by 91.6% in Group 1 and 78.4% in Group 2 (P less than 0.05). Ketanserin is effective in treating hypertension following coronary artery bypass grafting with an advantage of lack of reflex tachycardia.

Adult↗

PubMed1991

Intraoperative anaesthetic management of the liver transplant patient.

Orthotopic liver transplantation has become an established method of treating end-stage liver disease. Anaesthesia for patients undergoing this procedure can be complicated because end-stage liver disease is often associated with dysfunction of other physiological systems. Rapid haemodynamic, metabolic and coagulation changes can occur intraoperatively requiring aggressive haemodynamic monitoring backed by on-line laboratory facilities. The increased understanding of the pathophysiology of the procedure and the use of dedicated rapid infusion systems and intraoperative blood salvage have helped to improve the intraoperative management of the liver transplant patient. Co-operation and communication between the blood bank, haematology, biochemistry, surgical and anaesthesia services are vital.

Acid-Base Equilibrium↗

PubMed1991

Extraoperative management of the liver transplant patient.

Advances in liver transplantation have made the procedure an accepted therapeutic measure for patients with end-stage liver disease. This report is based on the authors experience on the first adult liver transplant in Singapore. The anaesthetic management is a challenge as patients are in long-standing hepatic failure with derangements of cardiovascular, renal, pulmonary, central nervous, and haematological systems. Therefore, individual preoperative assessment must incorporate a thorough understanding of these pathophysiologic phenomena and their interactions with anaesthetic drugs. Similarly, the postoperative care of the recipient will require intensive critical monitoring of all vital organ, systems and aggressive intervention to support failing organ systems. The important early concerns in the immediate postoperative period (less than 72 hours) include bleeding and graft function. After the first 72 hours, if the liver is functioning and the patient is not bleeding, it is a period of repair for the organ systems which were damaged prior to or during the transplant procedure. Intravenous nutrition is begun, and the immunosuppression maintenance dose is established. During the first three weeks, most of the technical causes of graft dysfunction, sepsis, and acute rejection become apparent. The distinction between rejection and infection continues to be an enigma, and requires rapid differentiation as the modes of therapy are totally different. The role of anaesthesiologists in the extraoperative care of the liver transplant recipient involves awareness and interdisplinary communication.

Humans↗

PubMed1991

Pharmacology of propofol.

Propofol is a new intravenous anaesthetic agent chemically unrelated to barbiturate, steroid, imidazole, or eugenol agents. It is available as 1% solution in an aqueous solution of 10% soya bean oil, 2.25% glycerol and 1.2% purified egg phosphatide. The desirable features of the drug are rapid, clear emergence from anaesthesia, lack of cumulation, lack of effect on adrenal steroidogenesis, and has no adverse effect on liver and renal function. In emulsion form, it does not release histamine, nor has it been associated with anaphylactoid reactions. Although, it causes pain on injection, it infrequently results in phlebitis or thrombosis. It causes hypotension and respiratory depression during induction. The induction dose in healthy adults is 2-2.5 mg/kg. Older or debilitated individuals require less propofol for induction.

Animals↗

PubMed1990

Analgesia and respiratory function following intrapleural bupivacaine after cholecystectomy.

Analgesia and pulmonary function following intrapleural bupivacaine were compared with those following intramuscular pethidine in thirty-four patients after cholecystectomy. The patients were randomly allocated to two groups of seventeen patients each to receive either intrapleural bupivacaine or intramuscular pethidine. The positions of seventeen intrapleural catheters inserted were confirmed by chest radiography. Two out of seventeen catheters were found to be located in the extrapleural space. It was also recognized by fluoroscopy that phrenic nerve palsy did not develop on patients given intrapleural bupivacaine. The subjective quality of analgesia following intrapleural bupivacaine was significantly better than that following intramuscular pethidine. The mean duration of analgesia obtained after each injection of bupivacaine was 4.68 hr (range 3.5-6.1 hr). Forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV 1), which decreased markedly in the postoperative period improved significantly after being given bupivacaine or pethidine. But there was no significant difference in the improvement of FVC and FEV 1, between both groups in spite of the higher percentage of pain relief in the intrapleural bupivacaine group. All respiratory function tests studied thirty days after surgery were not significantly different when compared with those before surgery.

Clinical Trial↗

PubMed1990

Intraventricular morphine for intractable craniofacial pain.

This case management report on a patient with advanced craniofacial neoplasm discusses the successful treatment of chronic pain by the cortical intraventricular narcotic administration. A previously treated patient with surgery and radiotherapy for carcinoma of the palate developed severe intractable pain despite high dose oral morphine therapy. Investigations revealed that neoplasm had reoccurred with extensive infiltration. Intraventricular morphine therapy was discussed and accepted by the patient and family. A ventricular shunt with an Ommaya reservoir was inserted under local anaesthesia. Preservative-free morphine sulphate in increasing doses of 0.25 to 1 mg was administered, once daily, which kept the patient in a pain-free state. The treatment was initiated in the hospital and continued at home till the demise of the patient on the 9th week. The home care was provided by the nurses of Home Nursing Foundation and Singapore Cancer Society under physician supervision. There were no complications which had been reported in the literature, observed in the management of this patient.

Drug Administration Schedule↗