Plasma concentrations of bupivacaine during extradural anaesthesia for Caesarean section

The clinical effects and plasma levels associated with the use of 0.5% bupivacaine with and without the addition of 1:200,000 adrenaline (5 micrograms/ml) were studied in 30 patients who underwent extradural anaesthesia for elective Caesarean section. The addition of adrenaline to bupivacaine prolongs analgesia, reduces the degree of hypotension and delays its onset. Plasma bupivacaine levels were consistently lower when adrenaline was added, but this difference was significant only at 10 minutes after the initial dose. Prolonging the interval between increments seems to be a more reliable way to reduce plasma concentration than the addition of the catecholamine.     

Effect of intravenous cimetidine on lignocaine disposition during extradural Caesarean section

We studied whether an intravenous bolus of cimetidine altered the disposition of extradurally administered lignocaine in the parturient. Mothers who requested extradural analgesia for elective Caesarean section were randomly pretreated with either cimetidine 200 mg intravenously (n = 5) or no H2-receptor antagonist (n = 5). No difference was found between peak plasma lignocaine levels or area under the plasma concentration/time curve between the two groups after administration of 6 mg/kg lignocaine 2% with adrenaline 1:200,000. There was no evidence for an effect of a single intravenous dose of cimetidine on lignocaine disposition in the obstetric patient. In addition, the extradural administration of 6 mg/kg lignocaine produces plasma levels well below toxic levels.     

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.     

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.     

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.     

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.     

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.     

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.     

An evaluation of a 30-gauge needle for spinal anaesthesia for Caesarean section

A 30-gauge spinal needle was evaluated for Caesarean section, using a combined epidural/spinal technique, in 50 mothers. Spinal anaesthesia failed in six mothers and was inadequate in another six. General anaesthesia was required on one occasion. A 25% overall failure rate suggests that a 30-gauge needle is not a practical proposition for routine clinical practice.     

Failed extradural anaesthesia for Caesarean section. Complication of subsequent spinal block

Two cases of unexpected high spinal anaesthesia following failed extradural anaesthesia for Caesarean section are described. In both cases rapid and unexpected advance of blockade, after the subarachnoid injection of moderate doses of local anaesthetic, required tracheal intubation. In one of the cases 15 ml of 0.9% saline, but no local anaesthetic, had been injected into the extradural space, suggesting that the mechanism involved is the cephalad displacement of the cerebrospinal fluid by extradural fluid, and not leakage of extradural anaesthetic solution into the subarachnoid space.     

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.     

Crystalloid versus colloid for circulatory preload for epidural Caesarean section

Sixty mothers were randomly allocated to receive either 2 litres of crystalloid or 1 litre of colloid solution (hydroxyethyl starch) in order to preload the circulation prior to elective Caesarean section under epidural anaesthesia. There were no differences in the incidence of hypotension, degree of haemodilution, umbilical cord blood gas tensions or umbilical blood osmolalities between the two groups.     

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.     

A rare complication of extradural analgesia

A case is reported of probable subdural injection of bupivacaine during attempted extradural analgesia for an operative obstetric procedure.     

Regional anaesthesia for repeat Caesarean section in a patient with phantom limb pain

The triggering of phantom limb pain by subarachnoid or epidural anaesthesia has been well described leading to the suggestion that neuraxial regional anaesthesia is relatively contraindicated in lower limb amputees. We report our experience of the provision of anaesthesia for repeat Caesarean section on two occasions in such a patient. Intrathecal fentanyl and morphine supplementation of bupivacaine successfully abolished peri-operative phantom limb pain, whereas epidural anaesthesia was associated with recurrence of phantom limb pain upon regression of the block     

Comparison of the effects of intrathecal ropivacaine, levobupivacaine, and bupivacaine for Caesarean section

Background. This study aimed to detect if intrathecal (i.t.)ropivacaine and levobupivacaine provided anaesthesia (satisfactoryanalgesia and muscular relaxation) and postoperative analgesiaof similar quality to bupivacaine in patients undergoing Caesareansection. Methods. Ninety parturients were enrolled. A combined spinal-epiduraltechnique was used. Patients were randomly assigned to receiveone of the following isobaric i.t. solutions: bupivacaine 8mg (n=30), levobupivacaine 8 mg (n=30), or ropivacaine 12 mg(n=30), all combined with sufentanil 2.5 µg. An i.t. solutionwas considered effective if an upper sensory level to pinprickof T4 or above was achieved and if intraoperative epidural supplementationwas not required. Sensory changes and motor changes were recorded. Results. Anaesthesia was effective in 97, 80, and 87% of patientsin the bupivacaine 8 mg, levobupivacaine 8 mg, and ropivacaine12 mg groups, respectively. Bupivacaine 8 mg was associatedwith a significantly superior success rate to that observedin the levobupivacaine group (P<0.05). It also provided alonger duration of analgesia and motor block (P<0.05 vs levobupivacaineand ropivacaine). Conclusions. The racemic mixture of bupivacaine combined withsufentanil remains an appropriate choice when performing Caesareansections under spinal anaesthesia. Br J Anaesth 2003; 91: 684–9