Supplementary oxygen administration for elective Caesarean section under spinal anaesthesia

We investigated the necessity for administration of supplementary oxygen to mothers undergoing elective Caesarean section under spinal anaesthesia. Sixty-nine women undergoing elective Caesarean section were randomly allocated to one of three groups to be given either oxygen (40%) by facemask, air by facemask or oxygen at 2 l x min(-1) by nasal cannulae. Umbilical arterial and venous blood samples were taken and analysed immediately after delivery. The results showed that there were no significant differences in the umbilical arterial or venous pH, partial pressure of oxygen and partial pressure of carbon dioxide between any of the three groups. We also assessed the patient acceptability of oxygen administered by facemask vs. nasal cannulae should the need for supplementary oxygen arise. It was found that use of the facemask impeded communication.     

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.     

Spinal anaesthesia with hyperbaric lignocaine for elective Caesarean section

This study was carried out in 30 patients undergoing elective Caesarean section to assess the predictability and reliability of spinal anaesthesia with 5% hyperbaric lignocaine, with a view to incorporating the technique in our failed intubation drill. The spinal was performed with a 25-gauge needle in either the sitting (15 patients) or left lateral position (15 patients). The speed of onset of anaesthesia to T6 was significantly faster (p less than 0.01) in the lateral group, but the duration of action was similar in both groups. Twelve patients had hypotension and four developed severe postspinal headaches. The block progressed to the C2 dermatome in four patients and was associated with dysphagia. This was totally unpredictable and may be due to altered cerebrospinal fluid dynamics in late pregnancy. Therefore, the use of spinal anaesthesia with heavy lignocaine may be inadvisable in obstetric patients, especially following failed intubation.     

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.     

Regional anaesthesia with a subarachnoid microcatheter for Caesarean section in a parturient with aortic stenosis

We present a woman in her first pregnancy, with known aortic stenosis prior to conception, who successfully underwent regional anaesthesia for an elective Caesarean section using a subarachnoid microcatheter. The anaesthetic management of patients with aortic stenosis requiring noncardiac surgery is a complex and contentious matter, particularly when the situation is compounded by the physiological changes accompanying pregnancy and delivery. This is the first reported use of a subarachnoid microcatheter in such a patient. The choice of technique is discussed and compared with other options for providing anaesthesia.     

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.     

Spinal anaesthesia for Caesarean section in a patient with systemic sclerosis

We describe the management of a diabetic primigravid woman with systemic sclerosis and thrombocytopaenia who required Caesarean section for pre-eclampsia. This was performed successfully under spinal anaesthesia.     

Arterial to end tidal carbon dioxide tension difference during Caesarean section anaesthesia

The relationship between arterial carbon dioxide tension and end tidal carbon dioxide tension was studied in 19 patients during general anaesthesia for Caesarean section. Thirteen patients scheduled for elective abdominal hysterectomy formed a nonpregnant group. There was significant correlation between arterial and end tidal CO2 tensions in both groups. During Caesarean section, this difference was significantly less than in the nonpregnant group.     

Respiratory effects of spinal anaesthesia for Caesarean section

We report the changes observed in a number of pulmonary function tests performed on 36 patients undergoing Caesarean section under spinal anaesthesia. The tests comprised peak expiratory flow, forced expiratory volume in one second, forced vital capacity, forced expiratory volume in one second to forced vital capacity ratio and the maximal mid-expiratory flow. Significant changes occurred that are consistent with a restrictive ventilatory defect. These changes persisted for four hours after the induction of spinal anaesthesia. Administration of 35% oxygen by facemask failed to change significantly fetal umbilical vein pH or partial pressure of oxygen.     

Hypotension following combined spinal-epidural anaesthesia for Caesarean section. Left lateral position vs. tilted supine position

Eighty-seven pregnant mothers undergoing elective Caesarean section were randomly allocated either to the full left lateral position (n = 45) or to the supine position with 12 degrees left lateral tilt (n = 42) after a combined spinal-epidural (CSE) in the sitting position and an initial 2 min in the full right lateral position. Fewer mothers were hypotensive while in the study position [29 (64%) in lateral group vs. 38 (90%) in the tilted supine group; p = 0.03]. Mothers in the lateral group tended to become hypotensive after turning them back to the tilted supine position immediately before surgery; hence the number of mothers who were hypotensive from the insertion of the CSE until delivery were similar [36 (80%) vs. 38 (90%)]. Mothers in the lateral group needed a lower dose of ephedrine to treat their hypotension while in their study position (median (interquartile range [range]) 6 (0-12 [0-36]) mg vs. 12 (6-18 [0-36]) mg, respectively; p = 0.04) but ephedrine requirements were similar overall (12 (6-12 [0-36]) mg vs. 12 (6-18 [0-36]) mg), respectively. The full left lateral position reduces the incidence of early hypotension compared with the tilted supine position with tilt, and makes it easier to treat.     

Embolism during Caesarean section

We investigated the occurrence of gas embolism during Caesarean section using a Doppler ultrasound probe and found that it occurs between uterine incision and delivery. Embolism is less common during general anaesthesia than has been reported during regional anaesthesia. Both ruptured membranes and a protracted uterine incision to delivery interval predispose to embolism.     

Glycopyrronium and hypotension following combined spinal-epidural anaesthesia for elective Caesarean section in women with relative bradycardia

The ability of glycopyrronium to reduce the severity of hypotension following subarachnoid block in parturients with a relative bradycardia was evaluated in a double-blind randomised controlled study. Women with a resting heart rate of < or = 80 beat x min(-1) presenting for elective Caesarean section were randomly allocated to receive either glycopyrronium 2 microg x kg(-1) or normal saline intravenously once positioned for combined spinal-epidural anaesthesia. Following spinal injection of 2.6 ml hyperbaric bupivacaine 0.5% and fentanyl 15 microg, women randomly allocated to the saline group were given 6 mg ephedrine so that all parturients received some prophylaxis against hypotension other than the fluid preload. Further ephedrine and fluid boluses were administered if mean arterial pressure fell 20% or more from resting values. Using a sequential analysis technique, analysis after the first 20 subjects indicated the study should be stopped, with no difference in ephedrine requirements or hypotension between the groups. We conclude that pretreatment with glycopyrronium 2 microg x kg(-1) is no more effective than 6 mg ephedrine in preventing hypotension following subarachnoid block in parturients with relatively low resting heart rates.     

Epidural versus general anaesthesia for elective Caesarean section Effect on Apgar score and acid-base status of the newborn

Elective Caesarean section deliveries over a 5-year period were studied to compare the effect of epidural block with general anaesthesia on the condition of the infant at birth. The Apgar score and umbilical arterial acid-base status were used as determinants of the latter. Epidural block was used in 139 (22.8%) mothers while 471 (77.2%) were performed under general anaesthesia. No babies in the epidural group were severely depressed (Apgar less than 4), compared with 6.2% in the general anaesthesia group. Only 4.3% of the epidural sections were moderately depressed (Apgar 4-6), compared with 15.4% of the others. These differences remained highly significant when infants of less than 2500 g were excluded, and when matched groups were compared. Mean umbilical arterial pH was similar within the two groups (pH 7.28), and was not consistent with asphyxia in almost 90% of the depressed infants. The findings suggest that general anaesthesia, rather than asphyxia or aortocaval compression, is responsible for most of the depressed infants born by elective Caesarean section. This may involve over 20% of babies delivered in this manner, so greater use of epidural block for elective Caesarean section is recommended. Further investigations are required to improve results with general anaesthesia.     

Combined epidural/spinal anaesthesia for Caesarean section

An evaluation of a 30 gauge spinal needle in a combined epidural/spinal anaesthetic technique for Caesarean section revealed a 25% failure rate of the spinal element. In this unit, no more than 4% of spinal anaesthetics might be expected to fail. One of the reasons for the higher failure rate was that, when using the Tuohy needle as an introducer, the dura was not identified. This prompted us to compare the 'through-the-Tuohy' or needle within needle approach for combined epidural/spinal anaesthesia, with a technique that involved siting the epidural and spinal sequentially in separate spaces. One hundred women requiring elective Caesarean section under spinal anaesthesia were randomised into single or double space groups. The technique failed in 16% of through-the-needle cases, and in 4% of sequential sitings. Combined spinal/epidural anaesthesia for Caesarean section is more successful if each procedure is performed using separate spaces.     

Efficacy of augmentation of epidural analgesia for Caesarean section

Background. Extension of a labour epidural for Caesarean deliveryis thought to be successful in most cases and avoids the useof general anaesthesia. However, most previous studies thathave estimated the failure rate of pre-existing epidural catheterswere performed in small numbers of patients. Methods. Therefore, we undertook to retrospectively measurethe failure rate of indwelling epidural catheters in a largenumber of patients. Results. The anaesthetic team was available at all times andwas permanently led by a senior anaesthetist specialized inobstetrics. Extension was performed using lidocaine 2% withepinephrine (mean 18 (SD 6) ml), combined in most patients withsufentanil (9 (2.2) µg) and/or clonidine (75 µg).Among 194 consecutive extensions performed in a 1-yr period,general anaesthesia was required in five patients (2.6%) whilesedation and/or i.v. analgesia were used in 27 patients (13.9%).In three cases where general anaesthesia was required, the intervalbetween decision to incision was <10 min. No factorassociated with failure could be identified. Addition of a lipophilicopioid or of clonidine did not modify the efficacy of the block(i.e. general anaesthesia or supplementation were required ina similar proportion). Conclusions. The augmentation of labour epidurals for Caesareansection using lidocaine 2% plus epinephrine is a reliable andeffective technique. No factor associated with failure couldbe identified. Br J Anaesth 2003; 91: 532–5