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Biomedical subjects

W D Ngan Kee

Publications and source records attributed to W D Ngan Kee.

At least 19 recordsLinked to original sources
PubMed2003

Multivariate analysis of factors associated with umbilical arterial pH and standard base excess after Caesarean section under spinal anaesthesia.

We have investigated the factors predicting umbilical arterial pH (UA pH) and standard base excess (UA BE) in 337 consecutive elective Caesarean sections performed under spinal anaesthesia. Multiple linear regression analysis was performed with UA pH and UA BE as the dependent factors. We found that the significant factors predicting UA pH were: use of ephedrine, uterine incision-to-delivery time, maximum decrease in systolic arterial pressure and the interaction between ephedrine use and duration of hypotension (adjusted R2 = 0.39, F15,321 = 15.4, p < 0.0001). The significant factors predicting UA BE were: use of ephedrine and the interaction between ephedrine use and duration of hypotension (adjusted R2 = 0.52, F15,321 = 25.0, p < 0.0001). We conclude that, in order to minimise the risk of fetal acidosis, ephedrine should not be used before delivery, uterine incision-to-delivery time should be as short as possible, and alpha-agonists such as metaraminol or phenylephrine should be used to minimise both the magnitude and duration of hypotension.

Acidosis↗
PubMed2002

Effects of high inspired oxygen fraction during elective caesarean section under spinal anaesthesia on maternal and fetal oxygenation and lipid peroxidation.

BACKGROUND: Oxygen supplementation is given routinely to parturients undergoing Caesarean section under regional anaesthesia. While the aim is to improve fetal oxygenation, inspiring a high oxygen fraction (FIO2) can also increase free radical activity and lipid peroxidation in both the mother and baby. In this prospective, randomized, double-blind study, we investigated the effect of high inspired oxygen fraction (FIO2) on maternal and fetal oxygenation and oxygen free radical activity in parturients having Caesarean section under spinal anaesthesia. METHODS: Forty-four healthy parturients were randomized to breathe either 21% (air group) or 60% oxygen (oxygen group) intraoperatively via a ventimask. Maternal arterial blood was collected at 5-min intervals from baseline until delivery, and umbilical arterial and venous blood was collected at delivery. We measured blood gases and the products of lipid peroxidation (8-isoprostane, malondialdehyde (MDA), hydroperoxide (OHP)) and purine metabolites. RESULTS: At delivery, the oxygen group had greater maternal arterial PO2 [mean 30.0 (SD 6.3) vs 14.2 (1.9) kPa; mean difference 15.8 kPa, 95% confidence interval 12.9-18.7 kPa, P<0.001] and greater umbilical venous PO2 [4.8 (1.0) vs 4.0 (1.4) kPa; mean difference 0.8 kPa, 95% confidence interval 0.0-1.5 kPa, P=0.04] compared with the air group. Maternal and umbilical plasma concentrations of lipid peroxides (8-isoprostane, MDA, OHP) were greater in the oxygen group than in the air group (P<0.05). CONCLUSIONS: We conclude that breathing high FIO2 modestly increased fetal oxygenation but caused a concomitant increase in oxygen free radical activity in both mother and fetus.

Adult↗
PubMed2002

Addition of meperidine to bupivacaine for spinal anaesthesia for Caesarean section.

BACKGROUND: In a prospective, randomized, double-blind, placebo-controlled trial, we investigated the effect of adding meperidine 10 mg to intrathecal bupivacaine on the duration of early postoperative analgesia in 40 patients having elective Caesarean section under spinal anaesthesia. METHODS: Patients received intrathecal injection of 0.5% hyperbaric bupivacaine 2.0 ml plus either normal saline 0.2 ml (saline group) or 5% meperidine 0.2 ml (meperidine group). After operation, all patients were given i.v. patient-controlled analgesia using morphine. RESULTS: The duration of effective analgesia, defined as the time from intrathecal injection to first patient-controlled analgesia demand, was greater in the meperidine group (mean 234 min, 95% confidence interval 200-269 min) compared with the saline group (mean 125 min, 95% confidence interval 111-138 min; P<0.001). The 24 h morphine requirement was similar in the two groups. The meperidine group had a greater incidence of intraoperative nausea or vomiting compared with the saline group (11 vs 3; P=0.02). CONCLUSION: Addition of meperidine 10 mg to intrathecal bupivacaine for Caesarean section is associated with prolonged postoperative analgesia but with greater intraoperative nausea and vomiting.

Adjuvants, Anesthesia↗
PubMed2002

Randomized, double-blind comparison of different inspired oxygen fractions during general anaesthesia for Caesarean section.

BACKGROUND: The optimal inspired oxygen fraction FI(O(2)) for fetal oxygenation during general anaesthesia for Caesarean section is not known. METHODS: We randomized patients having elective Caesarean section to receive one of the following: FI(O(2)) 0.3, FI(N(2))(O) 0.7 and end-tidal sevoflurane 0.6% (Group 30, n=20); FI(O(2)) 0.5, FI(N(2))(O) 0.5 and end-tidal sevoflurane 1.0% (Group 50, n=20), or FI(O(2)) 1.0 and end-tidal sevoflurane 2.0% (Group 100, n=20) until delivery. Neonatal outcome was compared biochemically and clinically. RESULTS: At delivery, for umbilical venous blood, mean PO(2) was greater in Group 100 (7.6 (SD 3.7) kPa) compared with both Group 30 (4.0 (1.1) kPa, P<0.0001) and Group 50 (4.7 (0.9) kPa, P=0.002) and oxygen content was greater in Group 100 (17.2 (1.6) ml dl(-1)) compared with both Group 30 (12.8 (3.6) ml dl(-1), P=0.0001) and Group 50 (13.8 (2.6) ml dl(-1), P=0.0001). For umbilical arterial blood, PO(2) was greater in Group 100 (3.2 (0.4) kPa) compared with Group 30 (2.4 (0.7) kPa, P=0.003), and in Group 50 (2.9 (0.8) kPa) compared with Group 30 (2.4 (0.7) kPa, P=0.04); oxygen content was greater in Group 100 (10.8 (3.5) ml dl(-1)) than in Group 30 (7.0 (3.0) ml dl(-1), P<0.01). Apgar scores, neonatal neurologic and adaptive capacity scores, and maternal arterial plasma concentrations of epinephrine and norepinephrine before induction and at delivery were similar among groups. No patient reported intraoperative awareness. CONCLUSIONS: Use of FI(O(2)) 1.0 during general anaesthesia for elective Caesarean section increased fetal oxygenation.

Adult↗
PubMed2001

Structured preoperative patient education for patient-controlled analgesia.

STUDY OBJECTIVE: To investigate the effectiveness of a structured preoperative education program in patients receiving patient-controlled analgesia (PCA). DESIGN: Randomized controlled trial. SETTING: University-affiliated hospital. PATIENTS: 60 ASA physical status I and II women undergoing major gynecologic surgery. INTERVENTIONS: Patients were randomly allocated to receive either standard information given during routine preanesthetic assessment (n = 30) or additional structured preoperative education on the use of PCA (n = 30). MEASUREMENTS: All patients received standard anesthesia and PCA was provided for postoperative analgesia. Patients were reviewed bid by an independent team of pain specialists and nurses. Patient satisfaction, severity of postoperative pain, nausea, dizziness, and morphine consumption were measured at discharge from recovery room, 24, and 48 hours after operation. Recovery characteristics of patients were also measured. MAIN RESULTS: Pain scores and morphine consumption decreased over time (p < 0.01), but there was no significant difference between groups. The overall analgesic efficacy, side effects, and recovery times was not affected by the education program. Patient satisfaction in the education group was better than control during early recovery (p= 0.03), but there was no additional benefit in the remaining postoperative period. CONCLUSIONS: Structured preoperative PCA education did not affect patient outcome. The early improvement in patient satisfaction was minimized by continued education and pain team supervision during the rest of the postoperative period.

Adult↗
PubMed2001

Anesthetic management of renal cell carcinoma with inferior vena caval extension.

We present a case of a patient with renal cell carcinoma extending into the inferior vena cava. Preoperative diagnosis was facilitated by transthoracic and transesophageal echocardiography (TEE), and inferior venacavography. Intraoperatively, monitoring with continuous TEE was used. Preparation was made for cardiopulmonary bypass but surgery was successfully completed using extracorporeal venous shunting. We discuss the important aspects of preoperative diagnosis and the intraoperative anesthetic management of this case.

Anesthesia↗
PubMed2001

Patient-controlled pethidine after major upper abdominal surgery: comparison of the epidural and intravenous routes.

We compared epidural (n = 17) and intravenous (n = 20) patient-controlled analgesia (PCA) using pethidine (bolus 10 mg, lockout interval 10 min, 4-h maximum dose 3 mg.kg(-1)) after total gastrectomy. We found that mean (SD) pethidine consumption in the first 24 h was 33% less in the epidural group [255 (85) mg] than in the intravenous group [379 (129) mg, p = 0.002], although most of this difference occurred in the first 8 h. Plasma concentrations of pethidine were lower at 8 h (p < 0.01) in the epidural group, but were similar at 24 h. Pain scores, side-effects, patient satisfaction and patient outcome were similar between groups. Epidural and intravenous pethidine PCA provided similar efficacy after major abdominal surgery, although the epidural route can reduce the amount of pethidine used initially.

Adolescent↗
PubMed2001

Extension of epidural blockade in labour for emergency Caesarean section using 2% lidocaine with epinephrine and fentanyl, with or without alkalinisation.

In a randomised, double-blind study, we investigated rapid extension of epidural analgesia to surgical anaesthesia for emergency Caesarean section. Parturients receiving epidural analgesia in labour who subsequently required Caesarean section were given a test dose of 3 ml lidocaine 2% with epinephrine 1 : 200 000, followed 3 min later by 12 ml lidocaine 2% with epinephrine 1 : 200 000 and fentanyl 75 microg, to which was added 1.2 ml sodium bicarbonate 8.4% (bicarbonate group; n = 20) or saline (saline group; n = 20). Mean (SD [range]) time to surgical anaesthesia was less in the bicarbonate group (5.2 (1.5) [2-8] min) than the saline group (9.7 (1.6) [6-12] min; mean difference 4.5 min (95% CI 3.5-5.5) min; p < 0.001). Maternal side-effects and neonatal outcome were similar between groups. We conclude that pH-adjusted lidocaine 2% with epinephrine and fentanyl is effective for rapidly establishing surgical anaesthesia in patients with a functioning epidural catheter for labour who require emergency Caesarean section.

Adult↗
PubMed2001

Randomized controlled study of colloid preload before spinal anaesthesia for caesarean section.

We randomized women having elective Caesarean section to receive either no preload (control group, n=33) or 4% gelatin solution (Gelofusine) 15 ml kg(-1) (colloid group, n=35) i.v. before spinal anaesthesia. Intravenous metaraminol was titrated at 0.25-0.75 mg min(-1) to maintain systolic arterial pressure (SAP) in the target range 90-100% of baseline after the spinal injection. The control group required more vasopressor in the first 10 min [median 1.7 (range 0-2.9) mg vs 1.4 (0-2.8), P=0.02] at a greater maximum infusion rate [0.5 (0-0.75) vs 0.25 (0-0.5) mg min(-1), P=0.0005] and had a lower minimum SAP [90 (51-109) vs 101 (75-127) mm Hg, P=0.006] than the colloid group. Nausea was less frequent in the colloid group (6 vs 24%) but neonatal outcome was similar in the two groups. Colloid preload improved haemodynamic stability but did not affect neonatal outcome when arterial pressure was maintained with an infusion of metaraminol during spinal anaesthesia for Caesarean section.

Adult↗
PubMed2001

Metaraminol infusion for maintenance of arterial blood pressure during spinal anesthesia for cesarean delivery: the effect of a crystalloid bolus.

We randomly allocated women having elective cesarean delivery to receive either no bolus (Control Group, n = 31) or 20 mL/kg lactated Ringer's solution (Bolus Group, n = 35) IV before spinal anesthesia. An infusion of metaraminol started at 0.25 mg/min was titrated to maintain systolic arterial blood pressure in the target range 90%-100% of baseline. The total dose of metaraminol required up to the time of uterine incision was similar between the Control Group and the Bolus Group (3.62 +/- 1.20 vs 3.27 +/- 1.39 mg, P = 0.3). However, the Control Group required more metaraminol in the first 5 min (1.29 +/- 0.60 vs 0.96 +/- 0.58 mg, P = 0.025) and a faster maximum infusion rate (0.45 +/- 0.20 vs 0.32 +/- 0.13 mg/min, P = 0.002) compared with the Bolus Group. There was no difference between groups in regards to changes in systolic arterial blood pressure or heart rate over time, or maternal or neonatal outcome. We conclude that when metaraminol is used to maintain arterial pressure during spinal anesthesia for cesarean delivery, crystalloid bolus is not essential provided that sufficient vasopressor is given in the immediate postspinal period.

Adult↗
PubMed2001

Dose-response study of epidural ropivacaine for labor analgesia.

BACKGROUND: Ropivacaine has been introduced for use in epidural analgesia in labor. However, there have been few formal dose-response studies of ropivacaine in this setting. METHODS: The authors performed a prospective, randomized, double-blind study examining the effectiveness of five different doses of ropivacaine (10, 20, 30, 40, and 50 mg) administered epidurally in a volume of 10 ml to establish analgesia in 66 parturients who were in active labor with cervical dilatation less than 4 cm. A dose was considered effective when the visual analog scale pain score decreased by 50% or more from baseline. RESULTS: A sigmoid dose-response curve and a probit log dose-response plot (linear regression coefficient, r = 0.84; coefficient of determination, r2 = 0.71) were obtained. The ED50 (median effective dose) obtained based on the maximum likelihood estimation was 18.4 mg (95% confidence interval, 13.4-25.4 mg). Time to onset of analgesia, duration of analgesia, time to two-segment regression of sensory block level, and incidence of motor block were not affected by the dosage of ropivacaine administered (P = 0.93, 0.12, 0.55, and 0.39, respectively). However, the upper level of sensory block was dose-related (P < 0.01). CONCLUSION: In a traditional dose-response study, the ED50 of ropivacaine required to initiate epidural analgesia in early labor was found to be 18.4 mg (95% confidence interval, 13.4-25.4 mg).

Adult↗
PubMed2001

Comparison of metaraminol and ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section.

BACKGROUND: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans. METHODS: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery puLsatility index, and Apgar scores were compared. RESULTS: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial pH was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29; P < 0.0001), and umbilical venous pH was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34; P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial pH less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups. CONCLUSIONS: When used by infusion to maintain arterial pressure during spinal anesthesia for cesarean section, metaraminol was associated with less neonatal acidosis and more closely controlled titration of arterial pressure compared with ephedrine.

Adult↗
PubMed2001

Spinal ropivacaine for cesarean section: a dose-finding study.

BACKGROUND: The dose-response relation for spinal ropivacaine is undetermined, and there are few data available for obstetric patients. METHODS: In a prospective, randomized, double-blind investigation, the authors studied 72 patients undergoing elective cesarean delivery. An epidural catheter was placed at the L2-L3 vertebral interspace. Lumbar puncture was then performed at the L3-L4 vertebral interspace, and patients were randomized to receive a dose of spinal ropivacaine diluted to 3 ml with normal saline: 10 mg (n = 12), 15 mg (n = 20), 20 mg (n = 20), or 25 mg (n = 20). Sensory changes assessed by ice and pin prick and motor changes assessed by modified Bromage score were recorded at timed intervals. A dose was considered effective if an upper sensory level to pin prick of T7 or above was achieved and epidural supplementation was not required intraoperatively. RESULTS: Anesthesia was successful in 8.3, 45, 70, and 90% of the 10-, 15-, 20-, and 25-mg groups, respectively. A sigmoid dose-response curve and a probit log dose-response plot were obtained, and the authors determined the ED50 (95% confidence interval) to be 16.7 (14.1-18.8) mg and the ED95 (95% confidence interval) to be 26.8 (23.6-34.1) mg. Duration of sensory and motor block and degree of motor block, but not onset of anesthesia, were positively related to dose. CONCLUSIONS: The ED50 and estimated ED95 for spinal ropivacaine were 16.7 and 26.8 mg, respectively. Ropivacaine is a suitable agent for spinal anesthesia for cesarean delivery.

Adult↗
PubMed2000

Epidural meperidine does not cause hemodynamic changes in the term parturient.

PURPOSE: Meperidine has local anesthetic properties and, therefore, when given epidurally it has the potential to cause hemodynamic changes. Our objective was to study the hemodynamic effects of an analgesic dose of epidural meperidine (50 mg) in 34 ASA 1-2 term parturients scheduled for elective Cesarean section under epidural anesthesia. METHODS: A lumbar epidural catheter was inserted and patients lay in the supine left wedge position. Intravenous fluid preload was withheld, and hemodynamic measurements comprising of mean arterial pressure, cardiac output and heart rate were made using automatic oscillotonometry (Dinamap 1486SX) and transthoracic electrical bioimpedance (Bomed NCCOM3). Following baseline measurements, the hemodynamic effects of sequential epidural injection of first, 10 ml saline, and 20 min thereafter, 50 mg meperidine diluted to 10 ml with saline, were recorded. Sensory blockade was assessed following each injection using loss of temperature discrimination to ice. Paired Student t tests were used to compare changes in hemodynamic variables. RESULTS: Epidural meperidine produced a small increase from the saline values in the mean (SD) cardiac output of 5.81 +/-1.44 to 6.04+/-1.54 L x min(-1) (P<0.05), and mean arterial pressure of 77.1+/-8.8 to 79.3+/-9.9 mm Hg (P<0.05). Sensory changes, the upper level of which ranged from L1 to T1, were detected in 94% of patients given epidural meperidine. Epidural saline injection had no such hemodynamic effects, but produced a detectable sensory level in two patients. CONCLUSION: Epidural meperidine, 50 mg, caused minimal hemodynamic changes in term parturients.

Analgesics, Opioid↗
PubMed2000

Peribulbar anaesthesia with 1% ropivacaine and hyaluronidase 300 IU ml-1: comparison with 0.5% bupivacaine/2% lidocaine and hyaluronidase 50 IU ml-1.

The low toxicity of ropivacaine makes it attractive for peribulbar anaesthesia. However, its motor-sparing properties are undesirable when akinesia is important. Hyaluronidase (300 IU ml-1) promotes the onset and quality of peribulbar blockade when used with other agents. We investigated the onset and quality of ocular akinesia in 80 patients randomized to receive 1% ropivacaine plus hyaluronidase 300 IU ml-1 (group 1), or bupivacaine 0.5%/Lidocaine 2% plus 50 IU ml-1 hyaluronidase (group 2). Ocular akinesia was scored from 0 (no movement) to 8 (full movement) every 2 min for 20 min. The groups showed no difference in the rate of onset or degree of akinesia achieved (analysis of variance with repeated measures; P = 0.34). Sixty per cent of patients in group 1 and 55% in group 2 achieved akinesia scores of < or = 4 by 6 min (chi 2 test; P = 0.5). We conclude that both peribulbar solutions produce equivalent onset and quality of ocular akinesia.

Aged↗
PubMed2000

A dose-response study of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery.

UNLABELLED: We performed a randomized, double-blinded dose-finding study of IV ephedrine for prophylaxis for hypotension in 80 women who received an IV crystalloid preload and spinal anesthesia for elective cesarean delivery. One minute after the intrathecal injection, patients were given saline control or ephedrine 10, 20, or 30 mg IV for 30 s. Systolic arterial pressure (SAP) in the first 12 min after the spinal injection was greater in the 30-mg group compared with other groups (P < 0.05). Hypotension occurred in 7 patients (35%) in the 30-mg group compared with 19 (95%), 17 (85%), and 16 (80%) patients in the control and 10- and 20-mg groups, respectively (P < 0.0001). Maximum decrease in SAP was smaller in the 30-mg group (mean lowest SAP 87% of baseline, range 58%-105%) compared with other groups (P < 0.01). Reactive hypertension occurred in 9 patients (45%) in the 30-mg group (mean highest SAP 120% of baseline, range 104%-143%) compared with 2 (10%), 1 (5%), and 5 (25%) patients in the other groups (P = 0.009). Heart rate changes, total ephedrine requirement, incidence of nausea and vomiting, and neonatal outcome were similar among groups. The proportion of patients with umbilical arterial pH < 7.2 was 10.5%, 25%, 42%, and 22% in the control, 10-, 20-, and 30-mg groups, respectively (P = 0. 12). We conclude that the smallest effective dose of ephedrine to reduce the incidence of hypotension was 30 mg. However, this dose did not completely eliminate hypotension, nausea and vomiting, and fetal acidosis, and it caused reactive hypertension in some patients. IMPLICATIONS: We investigated different doses of IV ephedrine as prophylaxis for hypotension during spinal anesthesia for cesarean delivery and found that the smallest effective dose was 30 mg. However, this dose did not completely eliminate hypotension, caused reactive hypertension in some patients, and did not improve neonatal outcome.

Acidosis↗