Epidural blood patch: why the rapid response?
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Biomedical subjects
Publications and source records attributed to L E Carrie.
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Spinal anesthesia has the advantages of speed of onset, reliability and lack of toxicity over lumbar epidural block. Against this must be offset several disadvantages, but these can be largely eliminated by careful choice of equipment and meticulous attention to details of technique. Only experienced obstetric anesthetists should perform spinal anesthesia, especially for Caesarean section. Given these conditions, spinal block has a most important part to play in obstetric anesthesia.
An epigastric impedance technique was used to measure gastric emptying in nonpregnant women, women in the third trimester of pregnancy, and women within 60 min of delivery. The basis of the technique is the increase in epigastric impedance after the ingestion of a nonionic fluid. The subsequent decline in impedance is used as a measure of gastric emptying. The impedance epigastrograph used consisted of a four-electrode array (two source, two detector) that was applied over the epigastrium. The method was sufficiently sensitive to measure the effects of pregnancy, labor, and narcotics on gastric emptying. There was no difference in the rate of gastric emptying between pregnant and nonpregnant females. Labor appeared to cause a significant delay in gastric emptying; the mean +/- SEM time taken for the gastric volume to decrease to 50% (T0.5) was 7.2 +/- 0.6 min during pregnancy and 13.0 +/- 1.9 min in the immediate postpartum period. However, the principal factor associated with the delay in gastric emptying in the group studied within 60 min of delivery was probably the use of meperidine and promethazine, because there was a significant difference (P less than 0.05) between subjects who received meperidine and promethazine during labor and those in another group who had received either no analgesia or extradural analgesia, the T0.5 values for the two groups being 18.2 +/- 4.0 and 10.3 +/- 1.4 min, respectively.
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Eighty women (40 for elective Caesarean section and 40 for elective gynaecological surgery) were randomly assigned to one of five treatment groups and received pre-operatively either no medication; magnesium trisilicate mixture (BP) 30 ml; metoclopramide 10 mg intramuscularly; ranitidine 150 mg orally on the night prior to, and the morning of, surgery; or metoclopramide 10 mg intramuscularly in combination with oral ranitidine 150 mg (the latter again given on the night prior, and the morning, of surgery). The effect of these medications on intragastric pH, volume and serum gastrin-17 was measured. No patient receiving ranitidine had a pH of less than 4. Magnesium trisilicate mixture resulted in the largest intragastric pH change although one woman in this group had a pH of 1.7. The largest intragastric volumes were seen in the patients who had received magnesium trisilicate mixture, whilst the patients who had received metoclopramide in combination with ranitidine had the smallest intragastric volumes. Magnesium trisilicate mixture and metoclopramide resulted in no change in serum gastrin levels. However, in the subjects who had received ranitidine on the night prior to surgery, the fasting serum gastrin was significantly higher (p less than 0.01) than the values in the remaining subjects, the mean (SEM) values being 60.3 (6.3) pg/ml in those not receiving ranitidine and 111.3 (19.5) pg/ml in those who had been given ranitidine.
A series of 52 patients in whom 0.5% bupivacaine was used to produce spinal analgesia for awake Caesarean section is described. Analgesia tended to be asymmetrical and of limited extent until the patients were turned from the left lateral to the right lateral position immediately after injecting the spinal solution. This movement produced a more symmetrical block with better cephalic spread. Initially 26-gauge spinal needles were passed through a Sise introducer, but this was modified to a needle through needle technique whereby a long-shafted 26-gauge needle was passed through a Tuohy needle which was subsequently used to insert an extradural catheter. The optimal volume of bupivacaine was 2.25-2.75 ml. The mean +/- SEM time to achieve maximal spread of analgesia was 17.5 +/- 0.6 min. The mean- +/- SEM time to the administration of the first postoperative analgesic was 163.5 +/- 7.0 min. The disadvantages of the technique were hypotension and the unpredictable spread of analgesia.
An inflatable 'wedge' for use in obstetric or other operations is described. As well as being inexpensive, the apparatus is remarkedly robust and has the advantage that the degree of inflation or deflation can be easily adjusted from the head of the operating table.
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Thirty patients were given a constant epidural infusion in labour by gravity feed drip of approximately 10 ml of 0.25% bupivacaine per hr. The infusion proved a simple and reliable method of ensuring adequate analgesia throughout labour. There were no problems of drug toxicity and the incidence of complications and side effects was comparable to a previous series using intermittent 0.5% bupivacaine.
Two hundred and six patients were studied to discover if previous regional analgesia influenced the incidence of unblocked segments and unilateral analgesia during lumbar epidural block in labour. Previous lumbar epidural or subarachnoid or sacral epidural blocks alone did not appear to influence the incidence of unilateral block or of unblocked segments. The practice of using epidural analgesia to facilitate the insertion of cervical circumsuture during pregnancy did not appear to be contra-indicated.
The incidence of instrumental delivery and malposition immediately before delivery was compared in patients who were given lumbar epidural analgesia and those who were not. Instrumental delivery was five times more common and a malposition of the fetal head was more than three times as common in the epidural group as in women who did not receive regional analgesia. Similar incidences were found even when the epidural was electively chosen before labour in the absence of medical indications. The instrumental delivery rate was affected by parity, the length of the second stage of labour, and the return of sensation by the second stage but not by other factors studied. The high incidence (20%) of malposition associated with epidural analgesia was not affected by any of the factors studied. The psychological and physical disadvantages of malposition and instrumental delivery have yet to be assessed. In the meantime, when there are no medical indications for epidural analgesia, the advantages of pain relief should be weighed against those of a normal spontaneous delivery.
Maternal plasma levels of cortisol were measured serially by radioimmunoassay in two groups of 12 patients during induced labour and in the puerperium. One group was given continuous extradural analgesia throughout labour, the other group received pethidine and promazine in response to pain. Pre-induction cortisol levels were significantly higher in patients who were to have extradural analgesia but the percentage increase in plasma cortisol during labour was considerably less than in patients with parenteral analgesia; in second stage labour, mean cortisol levels were the same in the two groups. This study suggests that patients who had chosen to have extradural analgesia may have been more anxious before labour than the other patients but continuous, extradural analgesia suppressed to some extent the percentage increase in mean cortisol levels found during labour in patients given parenteral analgesia. In the puerperium, there was no difference in mean cortisol levels in the two groups.