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Biomedical subjects

K S Poon

Publications and source records attributed to K S Poon.

13 recordsLinked to original sources
PubMed2001

Inflammatory pseudotumor of the urinary bladder: a report of five cases and review of the literature.

We describe five patients who recently presented with gross hematuria secondary to inflammatory pseudotumors of the bladder along with a review of the literature. At presentation, four of the five patients were clinically misdiagnosed as malignancies of which two were further believed to be leiomyosarcomas on initial histological examination because of their spindle-cell appearance. Conservative excision either by transurethral resection or partial cystectomy was curative in all cases. The main importance of these rare, benign lesions is to differentiate them from malignant tumors for which they may be mistaken, thus avoiding radical surgery and its attendant complications.

Adolescent↗
PubMed1997

Truncal rigidity as a result of epidural sufentanil--a case report.

It is well known that intravenous opioids may cause truncal rigidity. To the best of our knowledge truncal rigidity induced by epidural opioid has never been reported. Recently, we came across an accident of truncal rigidity following epidural sufentanil. The victim was a 65-year-old female who received cholecystectomy, choledochotomy, and cholangiography. For post-operative pain control, an epidural catheter was inserted cephalad [corrected] at L1-2 interspace with a length of 4 cm of the catheter retained in the epidural space. The epidural catheter was secured and tested for correct placement with 3 ml of 2% lidocaine with 1:200,000 epinephrine prior to induction of general anesthesia. No opioid was ever given in the operative course. When the patient was fully awake and complained of wound pain in the recovery room 50 mg of sufentanil in 10 ml normal saline was given via the epidural catheter after a negative evacuation test. About one minute after the epidural shot, she was found to lose consciousness without any slightest warning sign. Truncal rigidity and locked jaw that followed entailed respiratory arrest and rapid deterioration of oxygenation which evidenced a life-threatening airway emergency. It spite of our efforts we could not manage to ventilate her with ordinary means. It was not until the administration of 80 mg of succinylcholine and oral endotracheal intubation could an adequate ventilation be reestablished. She regained spontaneous breathing 15 min after the episode but for safety's sake she remained intubated for 6 h until the dissipation of analgesia. Another test dose was attempted, which reconfirmed that the epidural catheter was in proper position. She stayed in the recovery room for 24 h and returned to ward in satisfactory condition. The incidence disclosed that epidural sufentanil even with a dose as small as 50 micrograms could cause truncal rigidity. Thus when epidural sufentanil is applied for post-operative pain control constant vigilance is necessary in order to avoid accident.

Abdomen↗
PubMed1995

Evaluation of stress response to surgery under general anesthesia combined with spinal analgesia.

BACKGROUND: Each type of anesthesia has varying influence on the amount of catecholamine secretion during surgery. Epidural or spinal anesthesia can markedly suppress the increase of many of the stress hormones. Our purpose of this study is to evaluate metabolism change during surgery under anesthesia and to see whether general anesthesia combined with intraspinal anesthetic and narcotic is a better way to suppress such stress response. METHODS: Seventeen patients in fit physical condition (ASA class I) with normal biochemical screening scheduled for radical gastrectomy were studied. All patients were premedicated with diazepam and glycopyrrolate and an indwelling catheter was inserted into a radial artery under local anesthesia for monitoring blood pressure and obtaining blood samples for glucose and hormonal assays. A CVP line was set up via the right internal jugular vein for the administration of fluid (free of sugar). In the study group, a 32-G intraspinal catheter was placed via lumbar interspaces. Spinal blockade up to T4 by titrating 0.25% marcaine. Then anesthesia in both groups was induced with thiopental 5 mg/kg, followed by succinylcholine 1.5 mg/kg for intubation. Anesthesia was maintained with isoflurane, N2O, O2 and pancuronium. Blood samples for measurement cortisol, catecholamine and sugar were taken after induction and 30 min after surgical incision. Thirty min after skin incision all patients were subjected to glucose tolerance test, accomplished by giving 50% dextrose at 0.33 g/kg in 3 min. Arterial blood samples were then obtained at 1, 3, 5, 7, 10, 20, 30, 45 and 60 min intervals for plasma glucose determination. RESULTS: No difference was evident in cortisol values, baseline, before and after surgical incision (p > 0.05) either intragroup or inter-group. Catecholamine and glucose were significantly higher in control group after surgical incision (p < 0.05, intra-gr and inter-gr). Following a glucose load the decay of plasma glucose was similar in both groups but glycemic level was higher in the control group. CONCLUSIONS: Better control of stress response by general anesthesia combined with subarachnoid block was disclosed in this study.

Aged↗
PubMed1994

Complete heart block induced by general anesthesia in a patient with suspected conduction system defect: a case report.

We report a rare incident of complete heart block occurring after induction of general anesthesia in an apparently fit patient. An external temporary pacemarker was first applied, which was then replaced by isoproterenol infusion, but permanent pacing was required postoperatively. The role of anesthesia as a precipitating factor was discussed. It is suggested that surgical patients suspicious of conduction system defect should be under continuous hemodynamic monitoring with temporary pacing at hand during perioperative period.

Anesthesia, General↗
PubMed1993

Endothelium-derived nitric oxide partially mediates salbutamol-induced vasodilatations.

This study examined the ability of salbutamol (selective beta 2-adrenoceptor agonist) to cause endothelium-dependent relaxation in rat aortic rings and depressor response in conscious rats. Salbutamol (0.01-100 microM) concentration dependently relaxed preconstricted aortic rings. The relaxant response was partially attenuated by either mechanical removal of the endothelium or treatment with NG-nitro-L-arginine methyl ester (L-NAME, 100 microM). In conscious rats, either i.v. infused phenylephrine (5 micrograms/kg per min) or i.v. bolus injected L-NAME (12.8 mg/kg), but not the vehicle, caused similar sustained increases in mean arterial pressure (MAP). I.v. infused salbutamol (2-128 micrograms/kg per min, each dose for 5 min) dose dependently decreased MAP in vehicle-treated rats; the depressor responses were potentiated by hypertension induced by phenylephrine. In contrast, the magnitudes of the depressor response to salbutamol in L-NAME-treated rats were less than those in rats pretreated with phenylephrine or the vehicle. I.v. bolus injections of salbutamol (0.25-16 micrograms/kg) also caused dose-dependent and transient decreases in MAP in vehicle-treated rats. The magnitude but not the duration of the depressor response to salbutamol was less in rats treated with L-NAME, compared to those in rats given phenylephrine or the vehicle. These results suggest that endothelium-derived nitric oxide is partially involved in beta 2-adrenoceptor-mediated vasodilatation.

Albuterol↗
PubMed1993

Fatal gas embolism as a complication of Nd-YAG laser surgery during treatment of bilateral choanal stenosis.

A 40-day-old infant boy underwent Nd-YAG laser surgery because of congenital bilateral choanal stenosis. Cyanosis and cardiovascular collapse occurred during the operation. Resuscitation was initiated, but in vain; the patient died. The evolution of clinical events was consistent with a diagnosis of gas embolism. In the investigation of causes, the use of a sapphire tip with the Nd-YAG laser and the cooling of the tip with N2 gas were thought to have contributed to the fatal outcome. The authors warn of the potential risk of gas embolism with the Nd-YAG laser and a coaxial gas cooling system, and they emphasize the importance of monitoring for gas embolism in high-risk patients.

Choanal Atresia↗
PubMed1993

Inhibitory actions of diphenyleneiodonium on endothelium-dependent vasodilatations in vitro and in vivo.

1. This study examined the in vitro and in vivo inhibitory effects of diphenyleneiodonium (DPI), a novel inhibitor of nitric oxide (NO) synthase, on endothelium-dependent vasodilatations. 2. DPI (3 x 10(-8)-3 x 10(-6) M) concentration-dependently inhibited acetylcholine (ACh)-induced relaxation in preconstricted rat thoracic aortic rings, with an IC50 of 1.8 x 10(-7) M and a maximal inhibition of nearly 100%. DPI (3 x 10(-6) M) also completely inhibited the relaxation induced by the calcium ionophore, A23187 but not by sodium nitroprusside (SNP). The inhibitory effect of DPI (3 x 10(-7) M) on ACh-induced relaxation was prevented by pretreatment with NADPH (5 x 10(-3) M) and FAD (5 x 10(-4) M) but not L-arginine (L-Arg, 2 x 10(-3) M). Pretreatment with NADPH did not alter the inhibitory effect of NG-nitro-L-arginine on ACh-induced relaxation. 3. The inhibitory effect of DPI on ACh-induced relaxation in the aortae lasted > 4 h after washout. In contrast to pretreatment, post-treatment (1 h later) with NADPH (5 x 10(-3) M) reversed only slightly the inhibitory effect of DPI. 4. In conscious rats, DPI (10(-5) mol kg-1) inhibited the depressor response to i.v. infused ACh, but not SNP. However, it caused only a transient pressor response which was previously shown to be due completely to sympathetic activation. 5. Thus, DPI is an efficacious and 'irreversible' inhibitor of endothelium-dependent vasodilatation in vivo and in vitro. The mechanism of the inhibition may involve antagonism of the effects of FAD and NADPH, co-factors of NO synthase. However, unlike the N0-substituted arginine analogues (another class of NO synthase inhibitors), DPI-induced suppression of endothelium-dependent vasodilatation in vivo does not lead to a sustained rise in blood pressure.

Acetylcholine↗
PubMed1989

[Continuous thoracic epidural fentanyl in postoperative pain control--a comparison of two different dosages].

We evaluate the postoperative pain relief using continuous epidural fentanyl infusion in two different dosages for thoracic and upper abdominal surgeries. A total of 21 ASA class III patients were studied. A thoracic epidural catheter was placed before surgery but pain control was begun when the patients became fully awake and complained of pain in the recovery room. Patients were divided into group A (n = 9) and group B (n = 12). Those in group A were given fentanyl 1.5 micrograms/kg in saline solution as initial dose followed by continuous infusion at a rate of 1 microgram/kg/h for 23 hours. In group B the initial dose and the maintenance dose were respectively 1.0 microgram/kg and 0.5 micrograms/kg/h. Following the initial dose, the intensity of pain was assessed hourly for a total of 24 hours using a visual analogue pain scale with scores from 0 to 10. In group A, the pain scale fell from the baseline level of 7.7 +/- 2.6 to 2.3 +/- 2.0 at the first hour while in group B it fell from 8.9 +/- 1.4 to 4.3 +/- 2.1. The pain scores following continuous infusion in groups A and B were respectively 1.3 +/- 1.5 and 2.9 +/- 1.7. Although the analgesic effect appeared to be better in group A, pain relief was satisfactory in both groups (p less than 0.01). Regarding respiratory depression, there was a greater degree of rise in PaCO2 in group A and some of the patients even had a PaCO2 value above 50 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗