Anesthesia for cesarean delivery. Part II: epidural anesthesia intrathecal and epidural opioids venous air embolism

The combined spinal-epidural technique

Epidural and spinal blocks are well-accepted regional techniques, but they have several disadvantages. The CSE technique can reduce or eliminate the risks of these disadvantages. CSE block combines the rapidity, density, and reliability of the subarachnoid block with the flexibility of continuous epidural block to extend duration of analgesia. The CSE technique is used routinely at many institutions, particularly for major orthopedic surgery and in obstetrics. It has been used in tens of thousands of patients without any reports of major problems. Although at first sight the CSE technique appears to be more complicated than epidural or spinal block alone, intrathecal drug administration and siting of the epidural catheter are both enhanced by the combined, single-space, needle-through-needle method. Concerns about the epidural catheter entering the theca via the small puncture hole are now considered to be unfounded, but as with all epidural catheter techniques, vigilant monitoring of the patient during and after any injection is paramount. CSE is an effective way to reduce the total drug dosage required for anesthesia or analgesia. The intrathecal injection achieves rapid onset with minimal doses of local anesthetics and opioids, and the block can be prolonged with low-dose epidural maintenance administration. In addition, the sequential CSE method can be used to extend the dermatomal block with minimal additional drugs or even saline. Reduction in total drug dosage has made truly selective blockade possible. Many studies have confirmed that low-dose CSE with local anesthetic and opioid, or low-dose epidural block alone, will provide effective analgesia with minimal motor and proprioceptive block. Such neurologic selective blockade has made it possible for most patients to walk and bear down normally in labor or postoperatively. There remains concern about the risk of infection being increased when the CSE technique is used in place of epidural block alone. Despite a recent flurry of reports of meningitis with CSE procedures, there is no evidence the CSE block is more hazardous than epidural or subarachnoid block alone. Arguably, the single-space, needle-through-needle CSE technique will continue to improve with new needle designs and other advances to improve further the success rate and reduce complications, such as neurotrauma, PDPH, and infection. Over the past decade it has become clear that the CSE technique is a significant advance in regional blockade.

The anaesthetic management of a labouring woman with pulmonary arterio-venous malformations

Epidural analgesia is recommended for many medical conditions in labouring women. We describe a case where it was used successfully in a parturient with multiple pulmonary arterio-venous (a-v) malformations. It has been noted that pregnancy can cause marked deterioration in the condition of such patients. We support the suggestion that pulmonary a-v malformations can be added to the list of conditions for which epidural analgesia should be considered.

Alkalinization of lidocaine 2% does not influence the quality of epidural anaesthesia for elective caesarean section

This double-blind randomized study compared the effects of an epidural injection of lidocaine hydrochloride 2% (HCl) (Group 1), alkalinized lidocaine 2% (1 ml NaHCO3 per 10 ml of solution) injected either immediately (Group 2) or one hour after preparation (Group 3) in 45 parturients (n = 15 per group) scheduled for elective Caesarean section. Each patient received 16 ml of one of the three solutions. The mean pH values measured just before administration with a pH-meter PHM 64 Metrohm AG were 6.77 for the HCl lidocaine 2% solution, 7.34 for the freshly alkalinized solution and 7.35 for the solution prepared one hour before injection. The median maximal sensory level (range) observed was T3 (T8-C7), T4 (T5-C8) and T4 (T6-C6), obtained after 19 +/- 6 min, 18 +/- 8 min and 16 +/- 6 min respectively for each group. A motor block of grade 2 or 3 on the Bromage scale was obtained in 11, 10 and 14 patients respectively. No failure was observed although 3, 5, and 2 patients in Groups 1, 2, and 3 respectively required a supplementary bolus 20 min after the initial injection because of inadequate sensory level or pain at the operative site. In conclusion, this study shows that neither fresh alkalinization of 2% lidocaine nor the delay of one hour between preparation and injection of the alkalinized solution influences the onset or quality of epidural anaesthesia for elective Caesarean section.

Anaesthesia for caesarean section in a patient with myotonic dystrophy receiving warfarin therapy

A 31-yr-old parturient with myotonic dystrophy and asthma presented for elective Caesarean section. The patient was receiving warfarin having had two previous episodes of thromboembolism. Anticoagulation was subsequently provided by heparin in the weeks prior to delivery. The combination of the patient's medical conditions and the continuing need for anticoagulation presented a considerable anaesthetic problem in planning anaesthesia and analgesia for both elective and emergency delivery. Heparin was discontinued on the day prior to surgery and restarted immediately after surgery. During surgery flowtron anti-embolitic boots were used. Warfarin therapy was recommenced on the seventh postoperative day. Anaesthesia for Caesarean section was provided using a combined spinal epidural technique using a separate needle, separate interspace method. Postoperative pain was relieved by using a continuous epidural infusion, transcutaneous nerve stimulation and diclofenac. No new neurological problems arose despite the use of epidural analgesia in the presence of heparin anticoagulation. This method of providing anaesthesia and postoperative analgesia without the use of opioids in an anticoagulated, asthmatic, myotonic parturient has not been described elsewhere.

Alkalinization improves the quality of lidocaine-fentanyl epidural anaesthesia for caesarean section

This double-blind randomized study of 116 healthy women was undertaken to evaluate whether alkalinization potentiated the analgesic effects of epidural fentanyl-lidocaine for elective Caesarean section. After a test-dose of 3 ml, lidocaine 2% with adrenaline 1:200,000, all patients received 100 micrograms, fentanyl in 5 ml saline and they were then divided into two groups, to receive incremental doses of 5 ml lidocaine 2% with adrenaline 1:200,000 with or without 0.1 mEq.ml-1 sodium bicarbonate, to obtain anaesthesia to T4. The addition of bicarbonate to lidocaine resulted in a mean (SD) pH increase from 6.58 (0.01) to 7.14 (0.02) and in a mean PCO2 increase from 3.8 (0.8) to 345.1 (5.9) mmHg. Onset of sensory analgesia to the S1 segment as well as the interval between the block and the delivery of the baby were shorter in the bicarbonate group (respectively 15.4 (6.9) vs 18.9 (4.8) min and 28.9 (9.5) versus 33.9 (11.8) min; P < 0.01 and 0.05). No differences were noted in the onset to T4 or in the degree of motor block. The percentage of patients experiencing pain during surgery and requiring intravenous analgesics was higher in the group which did not receive bicarbonate (3% vs 16%; P < 0.05). There were no differences in intraoperative maternal side-effects, neonatal outcome or in maternal venous and umbilical venous and arterial lidocaine concentrations between the groups. The concentrations of fentanyl in maternal plasma, umbilical artery, and the umbilical artery to maternal vein ratio were greater in the alkalinized group (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)