RAPID ADMINISTRATION OF CRYSTALLOID PRELOAD DOES NOT DECREASE THE INCIDENCE OF HYPOTENSION AFTER SPINAL ANAESTHESIA FOR ELECTIVE CAESAREAN SECTION

Twenty parturients undergoing elective Caesarean section wereallocated randomly to receive crystalloid preload 20 ml kg^–1over either 20 min or 10 min before spinal anaesthesia. Significanthypotension (systolic arterial pressure <100mm Hg and <80% of baseline value) occurred in six of the 10 patients inthe 20-min preload group and seven of 10 patients in the 10-minpreload group (ns). Both groups had a significant (P < 0.05)increase in central venous pressure during the preload period.The mean central venous pressure in the 10-min group was 11.9mm Hg (range 6–19 mm Hg), which was significantly greater(P < 0.05) than that in the 20-min group (mean 7.3 mm Hg,range 2–13 mm Hg). Three patients in the 10-min grouphad clinically unacceptable increases in central venous pressure.This study has demonstrated that rapid administration of crystalloidpreload before spinal anaesthesia did not decrease the incidenceor severity of hypotension, and questions the role of crystalloidpreload.     

Hydroxyethylstarch compared with modified gelatin as volume preload before spinal anaesthesia for Caesarean section

We studied 90 patients undergoing elective Caesarean section under spinal anaesthesia who received lactated Ringer's solution 1000 ml with up to 1000 ml of modified gelatin, lactated Ringer's solution 1000 ml with up to 1000 ml of 6% hydroxyethylstarch or only up to 1000 ml of 6% hydroxyethylstarch. Lumbar puncture was performed as soon as 500 ml of the colloid were infused. The incidence of hypotension, number of patients requiring a vasopressor and doses of ephedrine required to restore arterial pressure were significantly lower in favour of those receiving the crystalloid-hydroxyethylstarch combination. In both groups receiving the 2000 ml preload, packed cell volume (PCV) values decreased by more than 20%, which may be of concern in patients already presenting with mild anaemia. In patients who received the colloid without the crystalloid, PCV values decreased by 14% but the risk of severe hypotension was comparable with the crystalloid-gelatin combination.      

Spinal anaesthesia with lidocaine 2% for Caesarean section

Spinal anaesthesia with 2, 2.5 or 3 ml of glucose-free lidocaine 2% was studied in 50 patients undergoing Caesarean section. Onset time, cephalad spread of analgesia, quality of analgesia, muscle relaxation, the cardiovascular effects and duration of analgesia and motor block were assessed. Reliable anaesthesia was provided with 2.5 and 3 ml while 2 ml of 2% lidocaine was insufficient. Onset time varied between 5.5 to 6 min and maximum cephalad spread was achieved in 10-15 min. The mean maximum extent of sensory analgesia was higher after 2.5 ml (T4.1) and 3 ml (T3.6) than after 2 ml (T7) (P < 0.001). Complete motor block was achieved in all the patients. The mean duration of sensory block was 123 +/- 6.23 min (2 ml) to 126 +/- 7.53 min (2.5 and 3 ml). The mean duration of motor block in 2.5 and 3 ml groups was higher (P < 0.001) than in the 2 ml group and was correlated with the dose of lidocaine (P < 0.05). Hypotension (SBP < 100 mmHg) was noted in 10% (n = 5) of patients in whom the cephalad spread of analgesia was also higher. All the neonates had an apgar score of 7 or more at 1 min. These results suggest that 2.5 to 3 ml of 2% lidocaine provides satisfactory anaesthesia for Caesarean section.     

Maternal and uteroplacental haemodynamic state in pre-eclamptic patients during spinal anaesthesia for Caesarean section

We have studied the effects of crystalloid (Ringer's acetate 1 litre) preloading and subsequent spinal anaesthesia in 12 pre-eclamptic parturient patients undergoing elective Caesarean section. Maternal placental uterine artery circulation was measured using a pulsed colour Doppler technique with simultaneous measurement of maternal haemodynamic state. Despite preloading, mean maternal systolic arterial pressure (SAP) decreased significantly and marked maternal hypotension (SAP < 80% of baseline value) was recorded in two patients after induction of spinal anaesthesia. Mean central venous pressure increased significantly after preload, but decreased to baseline shortly after induction of spinal anaesthesia. Mean pulsatility index (PI) in the uterine artery did not change during preload or spinal block. In one patient, uterine artery PI increased significantly when SAP decreased to 71% of the baseline value, 14 min after induction of spinal anaesthesia. These results suggest that preload with crystalloid solution does not prevent maternal hypotension in pre-eclamptic patients, and that changes in uterine artery velocity waveforms were minor when SAP was 80% or more of baseline during spinal anaesthesia. These changes did not appear to have any major effect on the clinical condition of the neonate, as assessed by Apgar score and umbilical artery pH values.      

Flow requirements for the Bain breathing circuit during anaesthesia for caesarean section

We studied the relationship between arterial carbon dioxide tension (PaCO2) and fresh gas flow (FGF) during use of the Bain breathing circuit for Caesarean section anaesthesia. Thirty-one patients undergoing Caesarean section were anaesthetised using the Bain circuit with intermittent positive pressure ventilation. The PaCO2 were measured at FGF of 70 ml X kg-1 X min-1, 80 ml X kg-1 X min-1, and 100 ml X kg-1 X min-1. The FGF requirement to maintain a given PaCO2 during Caesarean section anaesthesia is the same as the requirements for nonpregnant subjects, despite the increase in carbon dioxide production associated with pregnancy. This is probably because the total FGF determined by body weight and given during Caesarean section anaesthesia is 15-20 per cent higher than nonpregnant levels, due to the weight gain associated with pregnancy. A FGF of 100 ml X kg-1 of pregnant weight/min maintains PaCO2 of 4.44 kPa predelivery, which is in the desirable range of PaCO2 during Caesarean section.     

Epidural sufentanil does not attenuate the central haemodynamic effects of Caesarean section performed under epidural anaesthesia

The effect of sufentanil 30 μg added to the epidural local anaesthetic solutions used for anaesthesia during elective Caesarean section on central haemodynamic variables was studied. Haemodynamic measurements made by thoracic electrical bioimpedance (TEB) monitoring were compared in 21 healthy parturients undergoing Caesarean section under epidural anaesthesia with and without the addition of epidural sufentanil. The patients were randomized to control (Group C) and study (Group S) groups. Following iv prehydration, an epidural catheter was placed at the L_2?3 or L_3?4 interspace. After a negative test dose, in a double-blinded protocol, patients in Group S received sufentanil 30 μg (0.6 ml) in 4.4 ml lidocaine carbonate 2% with 5 μg · ml^?1 epinephrine and those in Group C received 5 ml lidocaine carbonate 2% with epinephrine. Lidocaine carbonate 2% with 5 μg · ml^?1 epinephrine was then titrated to establish an anaesthetic level of T₄. Haemodynamic variables (heart rate, mean arterial blood pressure, cardiac index, ejection fraction and end-diastolic index) were measured non-invasively, continuously throughout the perioperative period. There were no differences noted in haemodynamic measurements between the groups at any time perioperatively. However, differences occurred within the groups when compared with baseline values. Heart rate was increased in both groups intraoperatively. Cardiac index was increased throughout the intraoperative period in Group S but was less frequently elevated in Group C. Ejection fraction was increased throughout the perioperative period in Group S but not in Group C. End-diastolic index increased following iv preloading in both groups and returned to baseline with induction of epidural block. Maternal haemodynamic measurements as assessed by TEB monitoring, during Caesarean section, were not altered by the addition of 30 μg sufentanil to carbonated lidocaine for lumbar epidural anaesthesia.     

Antacid therapy for emergency Caesarean section

One hundred patients undergoing emergency Caesarean section were treated with cimetidine 200 mg intramuscularly when the decision was made to deliver the patient by Caesarean section and, preceding general anaesthesia, 30 ml of 0.3 M sodium citrate was administered orally. No routine antacid therapy was employed during labour. No patient had a gastric aspirate pH of less than 2.7, and only one of less than 3. The regimen is simple and effective, and treats only those patients at risk of acid aspiration.     

Volume preloading is not essential to prevent spinal-induced hypotension at Caesarean section

We have compared the protective effect of 1000 ml preload with 200 ml preload of crystalloid solution, administered during the 10 min before spinal anaesthesia was induced, in 60 healthy women with no fetal compromise undergoing elective Caesarean section. The spinal anaesthetic was managed identically in both groups by an anaesthetist who was unaware of the volume of fluid administered. A prophylactic infusion of ephedrine 60 mg in Hartmann's solution 500 ml was given according to maternal arterial pressure. Hypotension was defined as > or = 30% reduction from baseline or < 90 mm Hg, and was treated by i.v. ephedrine bolus doses. There was no significant difference in ephedrine requirements between the two groups or in the incidence, severity or duration of hypotension: 10 women in the 1000-ml group, five episodes lasting > or = 3 min compared with nine women in the 200-ml group, four lasting > or = 3 min. There was no difference between neonates in each group. We have now abandoned the routine of preloading before regional anaesthesia.      

Cimetidine — antacid combination as premedication for elective Caesarean section

The effect of premedication with an oral antacid (magnesium trisilicate), oral cimetidine or a combination of both was studied in 80 patients undergoing elective Caesarean section. Twenty patients served as untreated controls. Seventy per cent of the patients were in the high risk range for acid aspiration Pneumonitis (pH < 2.5 plus gastric coment volume > 25 ml). Antacid therapy was effective in raising pH but the gastric volume remained high in 50 per cent of the patients. Cimetidine was effective in decreasing gastric volume and raising pH but the pH was still <2.5 in two patients. None of the patients given the cimetidine-antacid combination were in the high risk range for acid aspiration Pneumonitis. The combination of an oral dose of Cimetidine 400 mg, three to four hours before the operation followed by 20 ml of magnesium trisilicate one hour preoperatively proved to be the most efficacious regimen for prophylaxsis against Mendelson’s syndrome in elective Caesarean section. Recent reports have suggested that non-particulate antacids (e.g., sodium citrate) may be preferable to particulate antacids such as magnesium trisilicate.     

Gastric pressure during emergency caesarean section under general anaesthesia

Gastric pressure and volume were measured in 20 pregnant women during emergency Caesarean section under general anaesthesia with neuromuscular block. Mean gastric pressure was 11 (range 4-19) mm Hg and we can predict that 99% of women undergoing emergency Caesarean section with neuromuscular block are likely to have gastric pressures of less than 25 mm Hg (mean + 3 SD). This has implications for the amount of cricoid pressure required during induction of anaesthesia. Gastric pressure increased during delivery to 19 mm Hg and fundal pressure caused a gastric pressure of 65 mm Hg in one woman. Gastric pressure decreased significantly after delivery (P < 0.001) to 8 mm Hg. Although we measured large gastric volumes (mean 112 (range 20-350) ml), there was no correlation between gastric volume and gastric pressure.      

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.     

Combination treatment with ranitidine and sodium bicarbonate prior to obstetric anaesthesia

The gastric pH and volume were measured in 175 patients undergoing elective, and 313 undergoing emergency, obstetric procedures. Ranitidine 150 mg was administered orally every 6 hours in labour and at least 2 hours before elective Caesarean section. Patients received 20 ml of 8.4% sodium bicarbonate orally immediately prior to induction of anaesthesia. The combination of ranitidine and sodium bicarbonate produced marked alkalinisation of gastric contents (mean pH 8.9). The administration of sodium bicarbonate pre-operatively in patients who received ranitidine less than 2 hours before operation led to satisfactory elevation of gastric pH. Only four patients had a gastric pH less than 2.5, one patient refused any medication, two received only ranitidine and one patient had a long interval from administration of bicarbonate to aspiration of gastric contents. Gastric volumes were high in labouring patients (mean 84 ml) despite administration of ranitidine. The effectiveness of sodium bicarbonate as a single dose antacid therapy prior to obstetric anaesthesia requires further study.     

高渗氯化钠-羟乙基淀粉用于子痫前期腰麻下剖宫产术的可行性

目的 研究子痫前期产妇在腰麻下行剖宫产术时输入高渗氯化钠-羟乙基淀粉液(HSH)对产妇及新生儿的安全性.方法 临床确诊子痫前期产妇30例随机分为观察组(n=20)和对照组(n=10).观察组先输注5 ml/kg HSH,再输注复方氯化钠;对照组仅输注复方氯化钠.抽取静脉血检测手术前后RBC、Hb、红细胞比容(Hct)、血小板计数(Plt)及电解质;记录术中MAP、HR、输液量、失血量、尿量和术后24 h内产妇进液量与出液量;记录麻黄碱的应用例数以及新生儿1 minApgar评分.结果 两组RBC、Hct、Plt和血清电解质手术前后及组间差异均无统计学意义;术中HR组内、组间比较差异亦无统计学意义;两组MAP在麻醉后5、8、10 min及术毕四个时点较麻醉前均明显降低(P＜0.05),且观察组MAP在麻醉后四个时点均高于对照组(P＜0.05);观察组术中输液量明显少于对照组,尿量多于对照组(P＜0.05);而术中失血量、术后24 h内输液量、尿量及新生儿.Apgar评分比较差异无统计学意义.结论 子痫前期产妇腰麻下行剖宫产术时输入5 ml/kg HSH是安全可行的.     

BLOOD LOSS DURING CAESAREAN SECTION UNDER GENERAL ANAESTHESIA

Blood loss during Caesarean section has been measured in 121patients using a haemoglobin dilution method. The results havebeen analysed in an attempt to determine the importance on bloodloss of age, parity, previous Caesarean section, placental site,size of baby, length of operation, and surgical experience.The only statistically significant factors increasing bloodloss were (a) multipara undergoing their first Caesarean section(particularly emergency section) and (b) a low anterior placenta.Heavy blood loss, especially in patients with a low haemoglobin,was associated with an increased incidence of postoperativepyrexia.     

Subarachnoid anaesthesia for elective Caesarean section

Forty patients who underwent elective lower segment Caesarean section under subarachnoid anaesthesia received either 2.0 ml 0.5% cinchocaine in 6% dextrose or 2.5 ml 0.5% bupivacaine in 8% dextrose via a 26-gauge needle with the patient in the left lateral position. Onset time was rapid in both groups and the distribution of maximum ascent of sensory analgesia was T1-T6. Efficacy of analgesia was greater in the bupivacaine group, although the duration of both sensory and motor blockade was shorter than following cinchocaine. There were no significant differences between the two groups either in the incidence and severity of complications or in the condition of the neonates. The high incidence (50-65%) and often profound extent of hypotension seen throughout the trial, confirm the ineffectiveness of crystalloid preload of 1500 ml as a single prophylaxis against hypotension.     

Plasma bupivacaine levels associated with extradural anaesthesia for Caesarean section

Plasma bupivacaine levels were measured in 47 women undergoing extradural Caesarean delivery. They were divided into four groups according to the following dose regimens using 0.5% bupivacaine. Group A were given a bolus of 20 ml with increment after 20 minutes. Groups B and C were given 10 ml initially with further increments if required at 10 minutes (group B) and 20 minutes (group C); Group D consisted of patients who had an extradural block extended for emergency Caesarean delivery. In the elective groups the highest and most rapidly achieved values were associated with group A and the lowest levels found in group C. The highest levels of all were found in the emergency group. The investigation indicates that slow controlled induction of extradural anaesthesia for Caesarean section greatly reduces the risk of local anaesthetic toxicity.     

Circulatory collapse following epidural bolus for Caesarean section a profound vasovagal reaction? A case report

IntroductionReduced blood pressure is commonly seen associated to spinal anaesthesia for Caesarean section and efforts to reduce its occurrence and its magnitude is common practice. Cardiovascular collapse requiring cardio-pulmonary resuscitation after putting the spinal/epidural block for Caesarean section is however a rare but most dramatic event.Presentation of caseWe describe a case with sudden short loss of circulation, circulatory collapse, short after start of emergency Caesarean section in top up epidural anaesthesia (3 + 12 ml ropivaciane 7.5 mg/ml), requiring CPR. The neonate was delivered during CPR with Apgar 1, 10, 10 at 1, 5 and 10 min. Circulation was restored following 60–90 s of CPR and administration of 0.5 mg adrenaline. No cardioversion was administered sinus rhythm was regained spontaneously. The mother and child had a further uncomplicated course. No signs of cardiac damage/anomaly, emboli, septicaemia, pereclampisa or local anaesthetic toxicity was found. The patient had prior to the decision about Caesarean section had fever and was subsequently relatively dehydrated.DiscussionThe patient had a fast return of sinus rhythm following birth of the child, without cardioversion. None of common causes for cardiac arrest was found and the patient an uncomplicated post Caesarean section course. The combination of epidural induced sympathetic block and reduced preload possibly triggered a Bezold-Jarisch reflex with a profound vasovagal reaction.ConcluiosnA structured plan for the handling of cardiovascular crisis must be available wherever Caesarean section are performed. Adequate volume loading, left tilt and vigilant control of circulation following regional block performance is of outmost importance.     

Manual displacement of the uterus during Caesarean section

Ninety ASA 1 and 2 pregnant women with term singleton pregnancies and no maternal and fetal complications, scheduled for elective or emergency Caesarean section, were randomly allocated to group LT (15 degrees left lateral table tilt, n = 45) and group MD (leftward manual displacement, n = 45). Subarachnoid block was established with a 25-gauge spinal needle at the L3-L4 interspace using 1.5 ml of 0.5% hyperbaric bupivacaine. A median sensory level of T6 was observed in both groups but the incidence of hypotension was markedly lower in group MD when compared to group LT (4.4% vs 40%; p < 0.001) with a significant reduction in mean (SD) ephedrine requirement (6 (0) vs 11.3 (4.9) mg; p < 0.001). The mean (SD) fall in systolic blood pressure was 28.8 (7.3) mmHg in group LT and 20 (12.7) mmHg in group MD. The time to maximum fall in systolic blood pressure was similar in both groups (4.5 min). We conclude that manual displacement of the uterus effectively reduces the incidence of hypotension and ephedrine requirements when compared to 15 degrees left lateral table tilt in parturients undergoing Caesarean section.     

Cimetidine - antacid combination as premedication for elective Caesarean section

The effect of premedication with an oral antacid (magnesium trisilicate), oral cimetidine or a combination of both was studied in 80 patients undergoing elective Caesarean section. Twenty patients served as untreated controls. Seventy per cent of the patients were in the high risk range for acid aspiration pneumonitis (pH less than 2.5 plus gastric content volume greater than 25 ml). Antacid therapy was effective in raising pH but the gastric volume remained high in 50 per cent of the patients. Cimetidine was effective in decreasing gastric volume and raising pH but the pH was still less than 2.5 in two patients. None of the patients given the cimetidine-antacid combination were in the high risk range for acid aspiration pneumonitis. The combination of an oral dose of cimetidine 400 mg, three to four hours before the operation followed by 20 ml of magnesium trisilicate one hour preoperatively proved to be the most efficacious regimen for prophylaxsis against Mendelson's syndrome in elective Caesarean section. Recent reports have suggested that non-particulate antacids (e.g., sodium citrate) may be preferable to particulate antacids such as magnesium trisilicate.     

The effect of subhypnotic doses of propofol on the incidence of pruritus after intrathecal morphine for Caesarean section

The effect of subhypnotic doses of propofol on intrathecal morphine-induced pruritus was studied in a prospective, randomly allocated, double-blind controlled trial. Fifty-eight women undergoing elective lower segment Caesarean section for a singleton fetus received spinal anaesthesia with 2.5 ml hyperbaric 0.5% bupivacaine and 0.2 mg of preservative-free morphine. They then received propofol 1 ml (10 mg) or Intralipid 1 ml (control group) intravenously after delivery. Pruritus was assessed using a five-point verbal rating scale at hourly intervals for 8 h. A second dose of their allocated treatment drug was administered at the first recording of significant pruritus. The pruritus score was reassessed after 5 min and the treatment was repeated if pruritus remained. There were no differences between the groups in the onset of pruritus or its successful treatment. No adverse side-effects were associated with this dose of propofol. There were no differences in the incidence of post-operative nausea and vomiting between the two groups. Subhypnotic propofol is not an effective treatment for intrathecal morphine-induced pruritus in women following Caesarean section.