Antifactor Xa levels vs. activated partial thromboplastin time for monitoring unfractionated heparin. A pilot study.

WHAT IS KNOWN AND OBJECTIVES: The two most common methods for monitoring unfractionated heparin (UFH) infusion are the activated partial thromboplastin time (aPTT) and the antifactor Xa heparin assay (anti-Xa). The purpose of this study is to compare the performance of an aPTT protocol vs. an anti-Xa protocol in adult patients as defined by the time to reach therapeutic range, the percentage of time the values were within the goal range and the number of times laboratory monitoring was conducted. We then analysed the discordance between paired values of anti-Xa and aPTT. METHODS: This was a single-centre prospective cohort pilot study conducted from 1 September 2013 to 31 May 2014. RESULTS: Eighty-five patients were treated with UFH infusion, aPTT monitoring (n = 48), anti-Xa monitoring (n = 37). The number of times aPTT and anti-Xa values were ordered was (median, IQR) 14 (2-34) vs 7 (2-76); P = 0·23. The time to reach therapeutic range in hours was (mean, SD) 22 (20) aPTT vs 15 (13) anti-Xa; P = 0·08. Therapeutic range (>50-100% of the time) was achieved in only 5 (10%) patients in the aPTT group vs. 21 (57%) in the anti-Xa group; P < 0·01. Supratherapeutic values (>50-100%) were observed in 38 (78%) patients in the aPTT group vs. 14 (38%) in the anti-Xa group; P < 0·01. The discordance between aPTT and anti-Xa was evaluated using 234 paired values from 37 patients. There was discordance between anti-Xa and aPTT values 57% of the time. Two patients had bleeding complications requiring blood transfusion or discontinuation of post-pilot protocol. WHAT IS NEW AND CONCLUSION: Utilizing an anti-Xa protocol to monitor heparin infusion showed favourable results compared with utilizing an aPTT protocol by maintaining values within the therapeutic goal range. The most common discordant pattern in our study was a disproportionate prolongation of aPTT to anti-Xa values. Patients with discordant values presenting with high aPTT to normal anti-Xa values may have an increased risk of bleeding complications.

Postanaesthetic shivering--a comparison of thiopentone and propofol.

One hundred and sixty patients undergoing minor surgical procedures were randomly allocated to receive either thiopentone or propofol for induction of anaesthesia. All patients were assessed in the recovery period for the development of postanaesthetic shivering. Twenty patients (25%) in the thiopentone group and 8 patients (10%) in the propofol group developed postanaesthetic shivering (p < 0.05). There was no statistically significant difference in tympanic temperature between shivering and nonshivering patients. Propofol as an induction agent is associated with a lower incidence of postanaesthetic shivering as compared to thiopentone.

Acid aspiration prophylaxis for emergency Caesarean section.

Over a 3.5 year period, 384 patients requiring emergency Caesarean section under general anaesthesia received at random one of six acid aspiration prophylaxis regimens as soon as the decision was made for surgery. In the first phase of the study, sodium citrate administered orally 0.3 M, 30 ml (group C, n = 120) was compared with metoclopramide 10 mg administered intravenously and sodium citrate (group MC, n = 65). In the second phase, all patients received sodium citrate, and either intravenous administration of ranitidine 50 mg (group RC, n = 50), omeprazole 40 mg (group OC, n = 50), ranitidine 50 mg with metoclopramide 10 mg (group RMC, n = 50) or omeprazole 40 mg with metoclopramide 10 mg (group OMC, n = 49). Gastric contents were aspirated using a 16 FG Salem sump tube and acidity measured with a pH meter. Non-parametric tests were used for comparisons. There was no difference in gastric volume or pH between groups C and MC, or among OC, RC, OMC and RMC. After pooling the data, median (range) gastric volume in groups C and MC (55 (0-360) ml) was greater than in groups OMC and RMC (40 (3-270) ml, p < 0.05). Median (range) pH was lower in groups C and MC (4.97 (0.76-6.99)) than in groups OC, RC, OMC and RMC (5.76 (1.11-7.5), p < 0.001). The proportion of patients with pH < 3.5 and volume > 25 ml in the C and MC groups (43/185) was greater than that in the OC, RC, OMC and RMC groups (18/199, p < 0.001). Ranitidine and omeprazole administered intravenously were equally effective adjuncts to sodium citrate in reducing gastric acidity for emergency Caesarean section. Compared with sodium citrate alone, the addition of either ranitidine, omeprazole or metoclopramide alone did not reduce gastric volume while small reductions in gastric volume were seen with the addition of metoclopramide and either ranitidine or omeprazole.

Asystole following laryngoscopy and endotracheal intubation: a case report.

Severe bradycardia and asystole are very rare complications following laryngoscopy and endotracheal intubation. In this report, we describe a case in which these life-threatening complications occurred in a healthy male during induction of general anaesthesia. Activation of vagal reflexes during manipulation of the airway and the use of vagotonic drugs at induction are the mechanisms postulated to be responsible for these phenomena. Analysis of heart rate variability measurements may be useful in identifying patients at risk for development of these haemodynamic alterations during the induction of anaesthesia so that appropriate drugs and monitoring can be administered.

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.

Plasma catecholamines and neonatal condition after induction of anaesthesia with propofol or thiopentone at caesarean section.

Increased maternal sympathetic nervous system activity may decrease placental perfusion and cause adverse neonatal effects. We have studied the catecholamine response and neonatal outcome in Chinese patients with uncomplicated, singleton pregnancies undergoing Caesarean section. Anaesthesia was induced with thiopentone 4 mg kg-1 (n = 32) or propofol 2 mg kg-1 (n = 30) followed by suxamethonium. Laryngoscopy was performed after 1 min and tracheal intubation completed by 2 min. Anaesthesia was continued with atracurium, nitrous oxide and isoflurane. Maternal venous blood samples were taken at 0, 1, 2, 3, 4 min and at delivery for assay of catecholamines. The increase from baseline values in mean arterial pressure after tracheal intubation was greater in the thiopentone group (29 (SD 15) mm Hg) compared with the propofol group (18 (14) mm Hg) (P < 0.01). The concentrations of noradrenaline and adrenaline increased in both groups after tracheal intubation. Maximum noradrenaline concentrations were greater in the thiopentone group (413 (177) pg ml-1) compared with the propofol group (333 (108) pg ml-1) (P < 0.05), but there were no differences between groups in adrenaline concentrations. Neonatal Apgar scores, neurobehavioural testing and umbilical catecholamine, blood-gas tension and oxygen content analysis were similar between groups. Propofol attenuated the hypertensive and catecholamine response associated with laryngoscopy and tracheal intubation but there was no improvement in neonatal outcome.

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.

Disposition of propofol at caesarean section and in the postpartum period.

We have compared the pharmacokinetics of a bolus dose of propofol 2 mg kg-1 in eight patients undergoing Caesarean section with those in eight postpartum patients undergoing sterilization by mini-laparotomy. The Caesarean section group had a total body clearance of (median) 31.5 (range 24.4-53.3) ml min-1 kg-1, apparent volume of distribution at steady state 5.10 (2.46-6.61) litre kg-1 and mean residence time 161 (52.3-251) min; values for the post-partum group were 33.8 (21.5-47.2) ml min-1 kg-1, 5.17 (3.47-8.09) litre kg-1 and 163 (92.3-238) min, respectively. The 95% confidence interval for the umbilical venous to maternal venous ratio of propofol at delivery was 0.62-0.86. Plasma protein binding studies showed there was less unbound propofol in maternal plasma (1.28-2.29%) compared with umbilical plasma (2.08-3.88%) (P less than 0.01). Neonatal concentrations of propofol were greater than maternal concentrations at 2 h and were in the range 0.05-0.11 micrograms ml-1 at 4 h.

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.

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.

Obstetric epidural analgesia with mixtures of bupivacaine, adrenaline and fentanyl.

We performed a double-blind comparison of six solutions for epidural analgesia in 90 healthy Chinese women with uncomplicated pregnancies. Patients were randomly allocated to receive 10 ml bupivacaine 0.125% or 0.25% plain, bupivacaine 0.125% with adrenaline 1.25 micrograms/ml, bupivacaine 0.25% with adrenaline 2.5 micrograms/ml or the latter two solutions with added fentanyl 50 micrograms. Analgesia was unsatisfactory in 30% of the bupivacaine 0.125% groups without fentanyl. The addition of adrenaline, compared with bupivacaine 0.25% plain, gave faster onset and longer duration of analgesia (p less than 0.05) which was similar to that found in both fentanyl groups. There were no differences in method of delivery or neonatal Apgar scores among groups. The least concentrated mixture that gave the best analgesia was the combination of bupivacaine 0.125% with adrenaline 1.25 micrograms/ml and fentanyl 50 micrograms.

Effect of oral omeprazole on intragastric pH and volume in women undergoing elective caesarean section.

We have studied in obstetric patients the efficacy of omeprazole in increasing intragastric pH to more than 2.5 and reducing volume to less than 25 ml. Omeprazole 40 mg was given orally the night before and again on the morning of surgery to 30 Asian women scheduled to undergo elective Caesarean section. After induction of anaesthesia, a gastric tube was inserted and intragastric contents aspirated. Volume and pH were recorded and measurements were repeated on completion of surgery. The median (range) volume was 2 (1-13) ml before surgery and 4 (0-14) ml at the end of surgery. There was insufficient volume to measure pH in all patients. The median (range) pH was 6.7 (4.6-7.4) before surgery in 20 patients and 6.6 (4.6-7.8) at the end of surgery in 28 patients. No adverse drug reactions were noted in mothers or neonates. Omeprazole 40 mg orally twice before elective Caesarean section appeared to be effective in reducing intragastric volume and acidity to acceptable values.

The addition of fentanyl to epidural bupivacaine in first stage labour.

Epidural analgesia was studied in 100 healthy Chinese women with uncomplicated pregnancies in first stage labour. Patients were randomly allocated to receive 8 ml of one of the following five solutions: bupivacaine 0.125% with fentanyl 50 micrograms or fentanyl 100 micrograms, bupivacaine 0.25% plain, bupivacaine 0.25% with fentanyl 50 micrograms or fentanyl 100 micrograms. There was no difference in quality of analgesia among groups as measured by the reduction of visual analogue pain scores 20 minutes after the epidural dose. The duration of analgesia was similar among groups with the overall median duration being 105 minutes. There was no difference in method of delivery or neonatal Apgar scores. The least concentrated mixture providing good quality analgesia for the first stage of labour was the combination of bupivacaine 0.125% with fentanyl 50 micrograms.

A comparison of the effects of omeprazole and ranitidine on gastric secretion in women undergoing elective caesarean section.

This study compares the efficacy of omeprazole and ranitidine at reducing gastric secretion in obstetric patients. Sixty-five women scheduled to undergo elective Caesarean section under general anaesthesia were randomly allocated to receive either omeprazole 40 mg or ranitidine 150 mg orally at 2200 hours the night before and at 0600 hours on the morning of surgery. Intragastric pH and volume were measured immediately after induction of anaesthesia and on completion of surgery. All patients had gastric aspirates less than 25 ml. None of the omeprazole group had an aspirate of pH less than 3.5. Six patients (19%) in the ranitidine group had aspirates of pH less than 3.5, a significant difference from the omeprazole group (p less than 0.05). Of these six, two (6%) had aspirates of pH less than 2.5. Hence this study showed that omeprazole was more effective and consistent than ranitidine at maintaining gastric pH greater than 3.5.

Propofol infusion anaesthesia for caesarean section.

Two propofol infusion regimens and a standard general anaesthetic were compared in thirty Chinese women undergoing elective Caesarean section. After induction of anaesthesia with propofol 2 mg.kg-1, ten patients received propofol 6 mg.kg-1.hr-1 and nitrous oxide 50 per cent in oxygen while ten were given propofol 9 mg.kg-1.hr-1 with 100 per cent oxygen. The other ten patients received thiopentone 4 mg.kg-1 and nitrous oxide 50 per cent in oxygen with enflurane one per cent. Maternal recovery times and psychomotor performance were recorded. Neonates were assessed by Apgar scores, neurologic and adapative capacity scores (NACS) and umbilical cord blood gas analysis. Haemodynamic changes were similar immediately following induction but the low propofol infusion group had the best haemodynamic stability subsequently. Recovery times were fastest in the low-infusion group but there were no differences in later postbox testing. Neonatal Apgar scores and umbilical blood gas analysis were similar but NACS at two hours were poorer in the high infusion group. A propofol infusion coupled with nitrous oxide appears to be a satisfactory technique for Caesarean section.