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Biomedical subjects

T L Lee

Publications and source records attributed to T L Lee.

At least 19 recordsLinked to original sources
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

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

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↗
PubMed1990

Mycobacterium chelonei keratopathy with visual rehabilitation by a triple procedure.

We report a chronic keratouveitis following an eye injury, the etiology of which remained obscure despite repeated corneal scrapings and cultures. Eventually, the diagnosis was established by culturing Mycobacterium chelonei from a corneal biopsy specimen. Topical amikacin resolved active inflammation, but dense corneal scarring and a cataract remained. Visual rehabilitation was achieved through a combined penetrating keratoplasty, extracapsular cataract extraction, and intraocular lens implantation. This case illustrates that there should be a high index of suspicion of atypical mycobacteria when faced with any unusual keratitis, particularly following penetrating injuries and corneal grafts.

Cataract Extraction↗
PubMed1990

Malignant hyperthermia.

Two cases of malignant hyperthermia (MH) are presented. The first patient presented initially with tachyarrhythmia intraoperatively and rapid onset of MH crisis. Nasopharyngeal temperature of 43 degrees C was attained after 15-20 minutes of anaesthesia. The patient eventually died of myocardial failure despite external cardiac massage, inotropic support and ventricular pacing. The second patient presented with increasing endogenous hypercarbia following the administration of suxamethonium and isoflurane. The use of the end tidal carbon dioxide monitor led to an early diagnosis of MH. The early use of dantrolene may have contributed to the favourable outcome.

Adult↗
PubMed1988

Interaction of B16 malignant melanoma tumor cells with the murine mesentery in vitro.

We have used organs cultures of murine mesentery as a model system to investigate the mechanisms by which B16-F10 melanoma cells invade normal tissues. The mesentery has the advantage of being a real tissue, consisting of a loose connective tissue, containing a normal complement of stromal cells and extracellular matrix, covered by a continuous epithelium of squamous mesothelial cells which are separated from the connective tissue by a laminin-containing basement membrane. B16-F10 cells seeded onto the mesentery in vitro cause a local retraction of the mesothelial cells exposing the underlying basement membrane onto which the tumor cells spread. Direct contact between the tumor cells and the margins of the mesothelial cells is required to induce retraction. Most of the B16 cells remain on the surface of the mesentery where they spread on the basement membrane without disrupting it. A few B16 cells penetrate the basement membrane and invade the connective tissue interior of the mesentery where they flatten out and assume a fibroblastic morphology. Tumor cells within the connective tissue may continue to translocate and they adhere to and move along the fibers of the connective tissue extracellular matrix without appearing to destroy or disrupt them.

Animals↗
PubMed1986

Determination of piquindone in canine plasma and urine by high-performance liquid chromatography.

This report describes a rapid, sensitive and selective method for the determination of piquindone in canine plasma and piquindone and the N-demethyl metabolite of piquindone in canine urine, utilizing normal-phase high-performance liquid chromatography (HPLC) with isocratic elution at ambient temperature and monitoring the ultraviolet absorbance of the eluent at 254 nm. The trimethyl analogue of piquindone is used as the internal standard in the HPLC assay of plasma. The assay was applied to the measurement of concentrations of piquindone in the plasma and urine of a dog following single intravenous and oral administration of 5 mg/kg doses of piquindone hydrochloride dihydrate.

Administration, Oral↗
PubMed1985

Determination of 4-amino-5-ethyl-3-thiophenecarboxylic acid methyl ester and its acid metabolite in plasma and urine by high-performance liquid chromatography.

Two separate, rapid, sensitive and selective high-performance liquid chromatographic (HPLC) assays were developed for the determination of 4-amino-5-ethyl-3-thiophene-carboxylic acid methyl ester (I) and its acid metabolite, 4-amino-5-ethyl-3-thiophene-carboxylic acid (II), in plasma and urine. The analysis of I is performed directly on a hexane extract of plasma or urine (buffered to pH 11) by normal-phase HPLC analysis using a 10-micron silica gel column with an eluting solvent of hexane-ethanol (95:5) and UV detection of the effluent at 254 nm. A methyl analogue, 4-amino-5-methyl-3-thiophenecarboxylic acid methyl ester, was used as the internal standard. The analysis of II is performed on the residue of either a diethyl-ether-washed protein-free filtrate of plasma or a methylene chloride-isopropanol (95:5) extract of urine (buffered to pH 5.3) using a 10-micron alkyl phenyl (reversed-phase) column with an eluting solvent of water-methanol-1 M phosphoric acid, pH 2.5 (70:30:0.05) with UV detection of the effluent at 254 nm. An isopropyl analogue, 4-amino-5-isopropylthiophene-3-carboxylic acid (IV), was used as the internal standard. The assay of compounds I and II were applied to the determination of plasma and urine concentrations of I and II in the dog and in man following oral administration of I X HCl. The data obtained demonstrated the extremely rapid and virtually complete deesterification of I (ester) to II (acid) in both species.

Animals↗