Fluid preload before spinal anaesthesia in Caesarean section: the effect on neonatal acid-base status

BACKGROUND AND OBJECTIVE: We evaluated the effect of two different preload solutions: (i) Ringer's lactate (compound sodium lactate intravenous infusion BP) and (ii) 0.9% sodium chloride solution on the neonatal acid-base status of the newborn infants. The two standard regimens were compared to detect a possible difference. METHODS: A 2 L crystalloid fluid bolus was administered immediately before spinal anaesthesia for elective Caesarean section in two groups of 20 healthy parturients, while rigorously maintaining maternal normotension. RESULTS: No significant differences in the Apgar scores at 1 and 5 min, or infant well-being were demonstrated in either of the two groups. The data show that umbilical artery PCO2 is lower in the Ringer's lactate group and that pH is insignificantly higher by 0.03. CONCLUSIONS: The choice of Ringer's lactate or saline for fluid preload does not have any effect on neonatal well-being.     

Assessment of volume preload on uteroplacental blood flow during epidural anaesthesia for Caesarean section

BACKGROUND AND OBJECTIVE: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed. METHODS: After Institutional Review Board approval and written informed consent, 14 consecutiVe women with epidural anaesthesia for Caesarean section received either hydroxyethyl starch 500 mL or gelatine 500 mL. Haemodynamic variables monitored were maternal arterial pressure, maximal blood flow velocity and pulsatility indices of the uterine artery derived from Doppler measurements. CONCLUSIONS: Maternal arterial pressure and pulsatility indices in both groups did not change from baseline after intravenous colloid infusion. However, uterine blood flow increased significantly in both groups. The effectiveness of volume preloading may therefore be better described by changes in maximum uterine blood flow velocity than by pulsatility indices or maternal arterial pressure.     

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

We randomized women having elective Caesarean section to receiveeither 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 wastitrated at 0.25–0.75 mg min^–1 to maintainsystolic arterial pressure (SAP) in the target range 90–100%of baseline after the spinal injection. The control group requiredmore 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 infusionrate [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) vs101 (75–127) mm Hg, P=0.006] than the colloid group. Nauseawas less frequent in the colloid group (6 vs 24%) but neonataloutcome was similar in the two groups. Colloid preload improvedhaemodynamic stability but did not affect neonatal outcome whenarterial pressure was maintained with an infusion of metaraminolduring spinal anaesthesia for Caesarean section. Br J Anaesth 2001; 87: 772–4     

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.     

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.     

Re-evaluation ofim ephedrine as prophylaxis against hypotension associated with spinal anaesthesia for Caesarean section

Purpose

To assess the safety and efficacy of 37.5 mg ephedrineim in preventing hypotension associated with spinal anaesthesia for Caesarean section.

Methods

In a double-blind randomised controlled study, 40 patients (20 in each group) were given either 37.5 mg ephedrine or placeboim. The following parameters were recorded: (i) blood pressure; (ii) heart rate; (iii) ephedrineiv supplementation; (iv) umbilical venous blood gases and neonatal Apgar scores.

Results

The incidence of hypertension in the study group was 30% compared with 20% for the control group (P:NS). There was no difference in mean highest blood pressure or mean highest heart rate between the groups. The incidence of hypotension was lower but not significantly lower in the study group (50%) than in the control group (80%) (P:NS). However, the incidence of delayed hypotension was only 10% in the study group patients compared with 50% in the control group patients (P < 0.05).

Conclusion

Giving 37.5 mg ephedrineim prior to spinal anaesthesia was not associated with reactive hypertension or tachycardia. Intramuscular ephedrine provided more sustained cardiovascular support than intravenous ephedrine.     

Fatal pulmonary embolism following spinal anaesthesia for Caesarean section

Pulmonary embolism remains one of the commonest causes of maternal death. Regional blockade is reported to decrease the incidence of postoperative thrombo-embolic disease. We describe a case in which a fatal pulmonary embolism followed an emergency Caesarean section for which the patient was given a spinal anaesthetic. We believe it to be the first time this has been reported.     

Epidural and spinal (subarachnoid) anaesthesia for Caesarean section

Regional anaesthesia for Caesarean section is increasing in popularity — a trend encouraged by obstetric anaesthetists because of its greater safety and the emotional benefits tomother and baby. Such anaesthesia is easier to provide for elective cases, but even in the case of many emergency or semi-emergency Caesarean sections there may be time to extend an epidural already in use, or to use spinal anaesthesia.The reason for the difficulty in providing effective epidural anaesthesia in some cases has been clarified with the identification of variable bands and septa in the epidural space. Spinal block gives more reliable anaesthesia but carries a higher risk of hypotension so that monitoring to detect, and measures to prevent it must be particularly rigorous.Two new developments which are likely to play a part in improving regional anaesthesia for Caesarean section and post-operative pain relief are continuous spinal and combined spinal-epidural techniques. In the case of the former, particular interest is being focused on very fine microcatheters, but the incidence of post-spinal headache with larger catheters is also being reassessed. The combined technique gives the speed of onset and reliability of the spinal block with the flexibility of analgesia provided by the epidural catheter, as well as the advantage of the Tuohy needle acting as guide for the very fine spinal needles.