Epidural analgesia in labour using intermittent doses determined by midwives.

Since 1985 midwives have been responsible for choice of drug and timing of epidural top-up doses for women in labour at Flinders Medical Centre. The midwife may choose from one of three different prescribed preparations, namely: bupivacaine 12.5 mg plus pethidine 25 mg, bupivacaine 25 mg, and bupivacaine 50 mg - each made up in a volume of 10 ml. This prospective study examined the incidence of adverse effects and level of patient satisfaction with midwife-managed epidural analgesia. Between 1987 and 1992, 6935 women received midwife-managed epidural analgesia. The pethidine/bupivacaine mixture was generally used for the first dose (75% of women) with a shift towards bupivacaine 25 mg or 50 mg for subsequent top-ups. Sixty-one per cent of women had normal vaginal deliveries, 25% instrumental and 14% caesarean deliveries. The most common side-effects were shivering, hypotension and itch. Shivering occurred following 11% of bupivacaine, and 2% of bupivacaine/pethidine top-ups. Itching was more common after bupivacaine/pethidine (3%) than after bupivacaine (1%). Women reported a high level of satisfaction with the overall experience of childbirth, though this was lower for instrumental and caesarean deliveries than for vaginal deliveries. On the other hand, satisfaction with pain relief provided by the epidural was greater in women who had caesarean or instrumental deliveries. The most commonly cited benefits of epidurals were good pain relief (83%), ability to cope (74%), feeling relaxed (67%), and being aware (60%), while feeling numb (23%) and experiencing severe pain at delivery (17%) were the most common causes of dissatisfaction.

Sudden onset of subarachnoid block after subdural catheterization: a case of arachnoid rupture?

We describe a patient who received an apparently uneventful extradural block in labour but developed rapid extension of neural block within minutes of receiving her first incremental dose 2 h later. Computed contrast tomography revealed radio-opaque dye within both the subdural and subarachnoid spaces, but none within the extradural space. This case report demonstrates that subdural spread of low-dose local anaesthetics is not always clinically distinguishable from extradural analgesia and that the arachnoid membrane may subsequently perforate with potentially serious consequences.

The nature and consequences of childbirth pain.

For most women, childbirth is associated with very severe pain often exceeding all expectations. Some childbirth education groups and popular texts on the subject, however, seem disposed to encourage unrealistic expectations: claiming that labour is other than painful and that pharmacological analgesia is both unnecessary and harmful. All too often, those who promote such views witness women in labour only occasionally and are rarely responsible for patient care. Pain associated with uterine contractions should be distinguished from that associated with delivery: for there are important differences in the clinical characteristics, neural pathways and physiological responses. In the first stage of labour pain is largely visceral in origin, whereas during the transitional and second stages somatic pain becomes more pronounced. As described in this review, it is now well established that uterine contraction pain evokes a generalised neuroendocrinal stress response producing widespread physiological effects during the first stage of labour. They include increased oxygen consumption, hyperventilation and respiratory alkalosis; increased cardiac output, systemic peripheral resistance and blood pressure; delayed gastric emptying; impaired uterine contractility and diminished uterine perfusion; and metabolic acidaemia. While other factors (such as anxiety, starvation and physical exertion) are also partly responsible for inducing some of these effects, pain appears to be the most potent source because they are all obtunded by effective epidural analgesia.

A force meter to assess lower limb motor function after epidural analgesia.

BACKGROUND AND OBJECTIVES: Current methods of assessing lower limb motor function using low-dose epidural analgesia are either too insensitive (Bromage scale) or too cumbersome for use during labor. Accordingly, we have designed a force meter that quantitatively measures isometric muscle power of the lower limbs during peak voluntary exertion. METHODS: The force meter was tested for linearity using calibrated reference weights. Measurements were made on two occasions (separated by an interval of approximately 5 years), and differences in response were assessed by regression analysis. Departure from linearity was examined by a lack of fit test. RESULTS: There was no significant nonlinearity in response over the range 0-15 kg, nor was there any significant difference in slope between the two functional modes of this device. The device overread slightly at the higher weights. CONCLUSIONS: The force meter described was found to be sufficiently accurate and suitable for the quantitative assessment of lower limb motor function after epidural analgesia during labor.

Accidental subdural catheterization: radiological evidence of a possible mechanism for spinal cord damage.

We describe the inadvertent subdural insertion of a lumbar extradural catheter in a primiparous woman in labour. A small quantity of local anaesthetic resulted in extensive motor and sensory block. Computed tomography performed after contrast injection demonstrated unequivocally that the catheter was in the subdural space. The catheter and injected fluid produced considerable displacement of the arachnoid within the thecal sac. We postulate that this could result in arterial compression or direct damage to the spinal nerve roots. Such a mechanism might explain some of the cases of permanent neurological damage associated with extradural analgesia.

An evaluation of epidural bupivacaine with and without meperidine in labor.

BACKGROUND: One aim of epidural analgesia during childbirth is to provide satisfactory pain relief with minimal side effects. We hypothesized that a combination of opioid and local anesthetic would better achieve this aim than either drug alone. This study compared the efficacy and side effects of epidural meperidine and bupivacaine combined to those of meperidine and bupivacaine alone. METHODS: One hundred consenting nulliparas requesting epidural analgesia in labor were randomly assigned to receive, in a double-blind fashion, one of five treatments. These were 25 mg meperidine, 12.5 mg bupivacaine, 25 mg meperidine plus 12.5 mg bupivacaine, 25 mg bupivacaine, and 37.5 mg bupivacaine. Efficacy of analgesia and side effects were assessed before and after each dose. Leg strength was measured with a force meter and blood flow to each foot with a blood perfusion monitor. The neurobehavioral state of the newborn was assessed by a pediatrician who was blind to treatment using a neurologic and adaptive capacity scoring system. RESULTS: Thirty-seven women did not achieve satisfactory analgesia after the first dose of test medication; these predominantly were those who received 25 mg meperidine (n = 12) or 12.5 mg bupivacaine (n = 11). Nausea decreased after the initial dose with all treatments (p less than 0.01), whereas shivering increased in patients receiving bupivacaine (p less than 0.01). There was a reduction in leg strength and an increase in blood flow associated with the two higher bupivacaine treatments (p less than 0.01), and with both parameters the dependent limb was most affected. Overall patient satisfaction was greatest in the group receiving meperidine plus bupivacaine. Neonatal neurologic and adaptive capacity scores did not differ significantly among the treatment groups. CONCLUSION: The low-dose combination of meperidine and bupivacaine used in this trial proved a satisfactory preparation for epidural administration during the early stages of labor.

Treatment options for the relief of pain during childbirth.

Despite its severity, the disposition of women towards pain during childbirth is influenced by many complex personal and cultural factors. Such influences may inspire a degree of stoicism towards labour pain which would be extraordinary in other painful circumstances. Nevertheless, the majority of women who deliver in a modern obstetric unit request some form of pharmacological pain relief. An important component of proper antenatal education, therefore, is to provide impartial information about the various analgesic alternatives which are available within each centre. Regimens of analgesia which depend on the systemic absorption of drugs (e.g., parenterally administered opioids; inhalational analgesia) are simple to administer but they have limited efficacy and are commonly associated with unpleasant central side effects. While some innovations in actual drug administration have been introduced, it is unlikely that any further major improvements will be feasible using the systemic approach to analgesia. Epidural analgesia has become established as the most effective and consistently reliable method of providing pain relief in labour. Recent advances have demonstrated that many of the adverse effects traditionally associated with epidural analgesia can be substantially reduced by administering local anaesthetics in smaller doses. It is becoming apparent that additional patient benefits are possible when epidural opioids are also used in combination with local anaesthetics. Techniques which allow the mother to exercise personal control over her epidural analgesia requirements are received more favourably and may help reduce the need for obstetric intervention.

Epidural medication after the initial dose: reflections on current methods of administration during labour.

Most women who receive epidural pain relief during labour require additional epidural analgesia following the initial dose. This review examines the relative merits associated with current methods of epidural drug delivery when further analgesia is required. Apart from considerations of patient safety and convenience the review compares the relative flexibility in pain management which can be provided by these different regimens. It is postulated that patient satisfaction is enhanced when the mother has some personal control over the density of neural blockade provided by epidural analgesia.

Epidural bupivacaine-pethidine mixture clinical experience using a low-dose combination in labour.

In an attempt to overcome some of the undesirable side-effects and sequelae traditionally associated with epidural analgesia, various mixtures containing bupivacaine and pethidine have been examined during labour. Preliminary investigations suggested that a mixture containing bupivacaine 0.125% was the most promising combination, and accordingly a prospective survey was conducted in order to assess this mixture further; 100 mothers were included in the survey and clinical assessment included analgesic efficacy, side-effects, degree of mobility, obstetric outcome and patient satisfaction. Ninety per cent of mothers described their pain relief as satisfactory following the initial dose and 67% chose to receive this mixture alone throughout labour. Among those who delivered vaginally, delivery occurred spontaneously in 63% of primiparas and 90% of multiparas. Urinary catheterization was required in only 10% of spontaneous deliveries. Mean umbilical vein blood concentrations at birth among 48 neonates were 0.12 mg/L and 0.05 mg/L respectively for pethidine and bupivacaine. Despite, in some cases, recall of severe pain at delivery patient satisfaction was extremely high. Reasons given for this high approval rating included the quality of analgesia, mood elevation, mobility, and feeling aware or in control during labour.

Shivering related to epidural blockade with bupivacaine in labour, and the influence of epidural pethidine.

A prospective survey of two hundred patients who received an epidural block in labour was performed in order to determine the incidence and severity of shivering, and the influence of likely associated factors. Twenty-two of the patients who shivered took part in a double-blind trial to see if epidural pethidine 25 mg, versus saline, had any effect upon shivering. Fifty per cent of patients shivered soon after the initial dose of bupivacaine. Shivering was more common among patients who had experienced shivering before epidural block, and in those who had received nitrous oxide (P less than 0.005). Prior intramuscular injection of pethidine did not significantly affect the incidence of shivering, and it was not influenced by the concentration of epidural bupivacaine used (0.5 or 0.25%). Shiverers were more likely to feel cold than non-shiverers (P less than 0.001) but shivering was generally regarded by patients as a trivial symptom, only 13% describing it as very irritating. Shivering was abolished or considerably diminished within ten minutes in all patients who received epidural pethidine 25 mg, whereas there was no change in eight out of eleven patients who received epidural saline. These results are significant (P less than 0.01), and demonstrate that shivering following epidural blockade can be effectively treated with small epidural doses of pethidine.

Antimicrobial activity of bupivacaine and pethidine.

The antimicrobial activity of bupivacaine and pethidine in concentrations commonly used in epidural practice was studied by an agar dilution method against ten common micro-organisms. Both drugs showed increasing microbe inhibition with increasing drug concentrations. Bupivacaine at common epidural concentrations inhibited eight of the ten organisms and pethidine inhibited six. These findings confirm previous reports of microbe inhibition by bupivacaine, and in addition demonstrate a similar but slightly lesser activity by pethidine. Although antimicrobial activity of epidural drugs can be regarded as a desirable property, clinical implications of such findings remain unclear.

A comparative study of techniques of postoperative analgesia following caesarean section and lower abdominal surgery.

A double-blind, within-patient trial was carried out to compare intramuscular pethidine 100 mg, epidural pethidine 50 mg and epidural bupivacaine 25 mg for pain relief on the day after caesarean section or lower abdominal gynaecological surgery. Analgesia was assessed on a visual analogue pain scale. Forced expiratory volume in one second (FEV 1.0) and venous plasma catecholamine levels were measured immediately before and approximately thirty minutes after each treatment. At the completion of the study the treatments were ranked in order of patient preference. Nineteen patients completed the trial. Analgesia provided by epidural pethidine 50 mg was superior to intramuscular pethidine 100 mg (p less than 0.05) but not statistically better than epidural bupivacaine. There was no significant difference in the duration of analgesia between the active treatments. A mean increase in FEV 1.0 of 18% occurred after both of the epidural treatments, but this did not achieve statistical significance. There was no significant change in catecholamine levels after any of the treatments. Epidural pethidine was preferred by patients over and above intramuscular pethidine and epidural bupivacaine (p less than 0.05).

Spinal anaesthesia revisited: an evaluation of subarachnoid block in obstetrics.

A series of 442 women receiving subarachnoid block for various obstetrical procedures is described. These included caesarean section, instrumental delivery, manual removal of placenta, insertion of cervical suture and miscellaneous procedures. General anaesthesia was required in ten patients because subarachnoid block proved to be unsatisfactory. There were no serious complications. The overall headache rate, ascertained by daily direct questioning during hospital admission, was 26.2%. Clinical features of dural puncture headache (DPH) were present in 8.6% and equivocally so in a further 3.4%. A significantly higher incidence of DPH was recorded among patients receiving a cervical suture. Among the thirty-eight patients who developed DPH, a 25 or 26 SWG spinal needle had invariably been used and in most instances the procedure was described as being uneventful. There were no consistent technical features among the patients who developed DPH, although operator experience may have been a factor. DPH was graded as 'severe' in ten patients (2.3%) and an epidural blood patch was rapidly curative in each of these cases. One patient required a repeat patch. Subarachnoid block proved to be a satisfactory technique for the procedures outlined in the survey. It proved to be particularly valuable when anaesthesia was required urgently in the delivery suite and may even be regarded as the anaesthetic of choice in these circumstances.

The management of headache following accidental dural puncture in obstetric patients.

The progress and management of fifty-eight obstetric patients who received an accidental dural puncture is described. Headache attributable to dural puncture occurred in 85% of patients managed conservatively. Epidural infusion or repeat epidural bolus injections of saline after delivery reduced the incidence to 65%. A therapeutic autologous blood patch using 8-10 ml of blood was performed in 28 patients at least 24 hours after the accidental puncture. Dramatic and permanent relief occurred in 75% following this procedure. A repeat blood patch was effective in four patients and ineffective in the remaining two. Mild and temporary back stiffness and one case of moderately severe radicular pain for three days were the only complications noted after the procedure. The pathophysiology and treatment of dural puncture headache is reviewed. Reduction of pressure differential across the dural puncture site is most useful in the first 24-48 hours. Persistent and severe headache occurring after this should be treated with blood patch.