Anesthesia for cesarean section

Level of sensory block after spinal anesthesia as a predictor of hypotension in parturient

When the sensory block level (SBL) is ≥T5 or T4, a high incidence of hypotension occurs in parturients after spinal anesthesia. A rapidly ascending SBL is another risk factor for spinal anesthesia-induced hypotension. However, the relationship between the ascension rate of the SBL and spinal anesthesia-induced hypotension remains unclear.After placement in the left lateral position, combined epidural-spinal anesthesia was performed on 140 parturients undergoing caesarean section using the following procedure: no volume preloading, injection site of L3-4 or L4-5, injection rate of 0.1 mL/sec, and administration of 10 mg of 0.5% hyperbaric bupivacaine. A receiver-operating characteristic curve was built to estimate the accuracy of the SBL ascension rate in detecting spinal anesthesia-induced hypotension.The mean time interval from spinal injection to placement in the supine position was 136 ± 10 seconds in all anesthesia procedures. The earliest and most complete records of the SBL started from the 3rd minute after spinal injection. The threshold spread rate corresponding to the highest accuracy for occurrence of hypotension was an SBL of ≥T8 at the 3rd minute after spinal injection, with 82% and 88% sensitivity and specificity, respectively.The ascension rate of an SBL of ≥T8 at the 3rd minute after spinal injection is as a predictor of hypotension in parturients.

The development and historical context of the Datta short laryngoscope handle

The hormonal, physiologic, and anatomic changes of pregnancy have a number of significant anesthetic implications, including the potential for difficulties and failures in tracheal intubation. The American Society of Anesthesiology closed claims database in the 1970s observed that maternal deaths were involved in 30% of all obstetrics claims, most stemming from difficulty with intubation or ventilation. In the late 1970s, Dr. Sanjay Datta, MBBS, an obstetric anesthesiologist at Brigham and Women's Hospital (Boston, MA), observed a number of differences in the practice of obstetric anesthesia in the United States when compared with his prior experiences in the United Kingdom and Canada. Dr. Datta perceived that parturients within North America had a higher body mass index. In addition, he observed an increased rate of cesarean delivery and general anesthesia use. These differences led him to evaluate ways in which the laryngoscope itself could be altered to improve the ease of intubation of parturients; this led to the development of the short laryngoscope handle. The genesis of the Datta short laryngoscope handle, and the accompanying historical context, will be explored.

Pharmacologic advances in canine and feline reproduction

Substantial improvements in therapeutic options for companion animal reproduction and gynecologic emergencies have been made over the last decade. New, alternative drug treatments, with fewer side effects and improved efficacy, are available. This has widened the spectrum of therapeutic possibilities for diseases that were previously treated only by surgical intervention. New drugs are available for estrus induction and pregnancy termination, as well as for the treatment of pyometra. This review summarizes the pharmacology and toxicology of reproductive agents currently in use for contraception, pyometra, dystocia, eclampsia, premature labor, agalactia, mastitis, metritis, and prostatic disorders, and compares their efficacy and safety with newer agents. Drug use and exposure during pregnancy and lactation, and subsequent risks to the fetuses, are also explored, with emphasis on antimicrobials, antifungals, anthelminthics, anesthetics, and vaccinations.

Acute hemodynamic collapse after induction of general anesthesia for emergent pulmonary embolectomy

Patients undergoing pulmonary embolectomy often experience hemodynamic deterioration during induction of general anesthesia (GA). Therefore, we studied the incidence and possible risk factors for hemodynamic deterioration during GA induction. Fifty-two consecutive patients undergoing emergent pulmonary embolectomy at our institution were included. Hemodynamic collapse after GA induction was defined as hypotension refractory to vasopressor, inotrope, or fluid administration, requiring cardiopulmonary resuscitation followed by urgent institution of cardiopulmonary bypass (CPB). Demographic variables, comorbidities, specific location of thromboemboli, preoperative inotropic support, and anesthetic drugs used for GA induction were evaluated as possible risk factors. After GA induction, hemodynamic collapse occurred in 19% of patients (n = 10). However, the occurrence of hemodynamic instability was not predicted by any of the evaluated risk factors. In addition, the incidence of in-hospital mortality did not differ between hemodynamically stable or unstable patients (10%; 4 of 42 versus 10%; 1 of 10 patients, respectively). In conclusion, hemodynamic deterioration after GA induction develops frequently during emergent pulmonary embolectomy. On the basis of our experience from this study and the unpredictable nature of hemodynamic deterioration, we suggest that patients undergoing pulmonary embolectomy should be prepared and draped before GA induction, and a cardiac surgical team should immediately be available for emergent institution of cardiopulmonary bypass.

Relationship between Oxidative Stress in Cord Blood and Route of Delivery

OBJECTIVE

To investigate the effect of route of delivery on the antioxidant system of newborns.

METHODS

We used the cord blood taken during labor of 56 vaginal deliveries and 50 elective cesarean sections. The specimens were analyzed for the plasma malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glucose 6-phosphate dehydrogenase (G6PD) activity and leukocyte count.

RESULTS

SOD and CAT activities were significantly higher in the elective cesarean group than the vaginal delivery group (p < 0.01 and p < 0.005, respectively), but G6PD activity was similar between the groups. Plasma MDA level was lower in the cesarean group compared to the vaginal delivery group (p < 0.001). Leukocyte count was higher in the vaginal delivery group (p < 0.005).

CONCLUSION

Our findings suggest that the route of delivery has an effect on oxidative stress in newborns exposed to oxidative stress during delivery. It can be suggested that the antioxidant system works more efficiently to overcome oxidative stress in newborns delivered via cesarean section.

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.

A survey of anaesthesia for caesarean section

In 1993 a postal survey of maternity hospitals within the UK was carried out to obtain data on the types of anaesthesia used for caesarean section. The poor response rate (79/226, 35%) reflects the paucity of data available in many centres. The data returned indicated a wide range of anaesthetic practice: from units with a general anaesthesia rate less than 10% to those with a general anaesthesia rate approaching 90%. Overall, during the 11-year period covered by the survey there was a significant reduction in the percentage use of general anaesthesia (77% in 1982 declining to 44% in 1992), but because of a 51% increase in the caesarean section rate the real reduction in the actual number of general anaesthetics used was modest (13%). If this holds true nationally, then factors other than a simple change from general anaesthesia to regional anaesthesia must contribute to the reduced maternal mortality from anaesthetic causes.

Levels of anaesthesia and intraoperative pain at caesarean section under regional block

This prospective study recorded levels of analgesia (loss of sharp pin prick sensation) and anaesthesia (loss of touch sensation) in 220 women during caesarean section under regional anaesthesia (70 epidurals, 150 spinals). At delivery the difference between analgesia and anaesthesia varied from 0-7 segments for epidurals and 0-9 segments for spinals. During surgery the level of anaesthesia at the time pain was experienced varied between T5 and T10. No patient with a level of anaesthesia which remained above T5 experienced pain. These results indicate that assessing the adequacy of block by sharp pin prick may be misleading and that in the absence of spinal or epidural narcotics a level of anaesthesia up to and including T5 is required to prevent pain during caesarean section.

Spinal or epidural anaesthesia for elective caesarean section?

Ninety seven women undergoing elective lower segment caesarean section were randomly divided into two groups, group 1 received spinal anaesthesia with hyperbaric bupivacaine and group 2 received mepivacaine 20 mg/ml with adrenaline 5 microg/ml via an epidural catheter. All patients were given a preload of Ringer acetate and Macrodex prior to onset of anaesthesia. Ephedrine 5 mg was given if the systolic blood pressure fell below 100 mmHg. There was a small (<30%) but significant (P<0.01) fall in blood pressure in both groups of women. Six women in the epidural group required supplemental analgesics during the operation compared to only 1 patient in the spinal group (P<0.01). Muscle relaxation was judged to be inadequate in 3 patients in the spinal group and in 5 patients in the epidural group. One patient in the spinal group had a characteristic post-spinal headache lasting 3 days. The injection-delivery time was shorter (P<0.01) in the spinal group compared to the epidural group. The Apgar scores at 1 and 5 min were similar in both groups. The results from our study suggest that spinal anaesthesia is a good alternative to epidural anaesthesia for elective caesarean section. A fall in blood pressure, which is equally possible in both groups of patients, should be prevented by adequate fluid preload and treated immediately by intravenous ephedrine.

Delivery temperature of heated intravenous solutions during rapid infusion

Warming of intravenous fluids may help to prevent shivering and hypothermia in the surgical patient. Increasing the fluid temperatures to as high as 60 degrees C has been suggested. An in vitro study was performed in which temperature changes following the rapid infusion of heated lactated Ringer's solution within a vein were measured. When 1 L of solution was warmed to 55 degrees C and then was infused over 4 min, local model vein temperatures rose from 37 degrees C to 44 degrees C. This effect of possible regional tissue heating may well occur in vivo. It is known that the rate of human blood cell hemolysis and membrane enzymatic function is affected by temperature. Further efforts need to be directed toward appreciating the effects of warmed intravenous fluids upon intact physiologic preparations and red blood cells.

Epidural anaesthesia for caesarean section: a comparison of 0.5% bupivacaine and 2% lignocaine both with adrenaline

Thirty-eight women having caesarean section under epidural anaesthesia received either lignocaine 2% or bupivacaine 0.5% both with adrenaline 1:200,000 in a double-blind, randomised study. The time to establish satisfactory surgical anaesthesia, the volume required and the quality of analgesia as assessed by the anaesthetist, patient pain and discomfort scales and patient approval, were not significantly different. Motor block assessed by the Bromage and RAM-test was greater in the lignocaine group but surgical opinion of abdominal wall relaxation was not significantly different between groups. The bupivacaine group had significantly longer durations of sensory and motor block while the lignocaine group had a higher incidence of maternal shivering, other complication rates being similar. Neonatal outcomes were uniformly good. Both local anaesthetics provided satisfactory epidural anaesthesia and neither proved to have a distinct advantage in the clinical setting of this study.

Epidural versus combined spinal epidural block for cesarean section

In a controlled study a single segment combined spinal epidural (CSE) block was compared with epidural block for cesarean section. Thirty healthy parturients were randomly divided into two groups. In both groups a T4 block was aimed at. Bupivacaine was used to provide analgesia in both groups. All patients receiving CSE block had good to excellent analgesia, while 11 patients (74%) receiving epidural block had similar pain relief. This was reflected in the requirement for additional analgesics, sedatives or N2O anesthesia. The muscular relaxation was also better following CSE block. The total dose of bupivacaine for a T4 block was three times larger in patients receiving only epidural block. The maternal and fetal blood bupivacaine levels were correspondingly about three times higher in the epidural group. Additionally, the incidence of maternal hypotension was higher in patients receiving epidural block. Apgar scores, blood gases and neurobehavioural evaluation did not show any differences between the two groups of neonates. No postspinal headache was noted. CSE block appears to combine the reliability of spinal block and the flexibility of epidural block while minimizing their drawbacks.

Neonatal advantage of epidural anesthesia in elective and emergency cesarean sections: a report of 531 cases

In 147 elective and 384 non-elective cesarean sections, the need for neonatal respiratory assistance at birth was significantly greater for babies born under general anesthesia compared to epidural anesthesia, and the differences could not be explained by differences in pre-operative risk factors. For 114 babies on whom blood gas data were gathered prospectively, a greater proportion born under general anesthesia were acidemic and hypercarbic. Our results complement a growing body of retrospective and clinical data suggesting that epidural anesthesia is preferable to general in all but a few cesarean sections. Ideally, this suggestion should be tested in a randomized clinical trial.

Anesthetic management of ruminants and swine with selected pathophysiologic alterations

Surgical diseases induce pathophysiologic alterations in ruminants and swine that are often of critical importance in the perioperative period. Circulation and ventilation may be severely compromised. Alterations in acid-base balance, fluids, and electrolytes should be anticipated, identified, and corrected. Also discussed is the selection of appropriate anesthetic techniques and supportive therapy based upon the patient's physiologic status and surgical requirements.

[Pharmacokinetics of thiopental in women and newborn infants]

Plasma thiopentone concentrations after a single intravenous dose were determined by high pressure liquid chromatography in female surgical patients (n = 13), in pregnant women at term (n = 13) and in neonates (n = 13). In pregnant women, the apparent volume of distribution (Vd = 10.02 +/- 3.26 l X kg-1), plasma clearance (Cl = 22.03 +/- 7.55 l X h-1) and elimination half-life (t 1/2 (3) = 21.71 +/- 11.12 h) were significantly greater than in the surgical patients (Vd = 4.22 +/- 1.16 l X kg-1; Cl = 12.49 +/- 3.50 l X h-1; t 1/2 (3) = 13.79 +/- 3.09 h). Elimination half-life in neonates (t 1/2(e) = 17.9 +/- 9.7 h) was not different from half-life in mothers or in the surgical group. At delivery, the simultaneous concentrations were 5.3 +/- 1.3 mg X l-1 in venous blood and 3.8 +/- 1.6 mg X l-1 in cord venous blood. Apgar score was 10 in eleven neonates. For two babies, an Apgar score at 6 was explained by a uterine incision-to-delivery time interval greater than 2 min.

[Anesthesia for emergency cesarean section after uterine rupture associated with recent fracture of the cervical spine]

General anaesthesia with intubation is preferable for emergency Caesarean section, whilst epidural anaesthesia should be reserved for elective Caesarean section. The case of a patient who required emergency Caesarean section following uterine rupture is discussed. The management was complicated by a cervical spine injury which had occurred four months previously. Because an epidural catheter had already been inserted at an early stage of labour, this was the anaesthetic technique chosen for the emergency section. This avoided tracheal intubation and the possibility of worsening the cervical fracture. The end result was satisfactory, both for the mother and the child.

Three per cent 2-chloroprocaine for caesarean section: appraisal of a standardized dose technique

We evaluated 2-chloroprocaine, three per cent, in 44 women having epidural anaesthesia for Caesarean section. All subjects received a minimum dose of 25 ml (750 mg) in increments designed to allow early recognition of accidental subarachnoid or intravascular injection. Further increments were given as needed to achieve a T5 sensory level or higher. We recorded pulse and blood pressure at two-minute intervals and used a simple pain scale to assess analgesia. Ninety-three per cent of subjects had acceptable analgesia. Seventeen mothers required more than 25 ml to attain a T5 level; subjects having a BMI (body mass index) equal to or greater than 35, or over 35 years of age, demonstrated more cephalad spread. Hypotension (MAP 80 per cent of control or less) occurred in 24, mothers (54 per cent), often transiently, but an infused fluid volume exceeding 30 ml X kg-1 at delivery significantly reduced post-delivery hypotension. Nausea and vomiting accompanied the hypotension in 12 mothers. No neonatal depression occurred. We conclude the incremental administration of chloroprocaine, as described, permits safe administration of the drug, with excellent analgesia in most parturients.

A comparison of T4 and T7 dermatomal levels of analgesia for caesarean section using the lumbar epidural technique

We compared analgesia to the T4 dermatomal level with analgesia to the T7 level with and without prophylactic intramuscular administration of ephedrine 25 mg to determine the adequacy and side effects of such analgesia for caesarean section. Unmedicated patients were prehydrated (727 +/- 303 ml of saline solution) and kept in a left lateral tilt position. Sufficient three per cent chloroprocaine was given to obtain analgesia to the T7 (T6-T8) dermatomal level (455 +/- 128 mg) or to the T4 (T3-T5) dermatomal level (758 +/- 168 mg). Patients who received analgesia to the higher level required less narcotic than those who received analgesia to the lower level (21 per cent versus 48 per cent) (p less than 0.05). The incidence of hypotension in patients with analgesia at the T4 level was 21 per cent for those receiving ephedrine and 64 per cent for those who did not receive ephedrine (p less than 0.05). Intramuscular administration of ephedrine 25 mg was not associated with increased plasma levels of norepinephrine, epinephrine or dopamine. There was no difference in Apgar score, behavioural test scores, neonatal acid-base status or oxygenation in children of mothers in the different groups. We conclude that a T4 dermatomal level of analgesia combined with intramuscular administration of ephedrine 25 mg, provides more maternal comfort than a T7 level of analgesia does, with or without ephedrine, and is without significant maternal or foetal side effects.

Fetal and maternal plasma catecholamine levels at elective cesarean section under general or epidural anesthesia versus vaginal delivery

Fetal and maternal plasma levels of catecholamines were measured at birth in 40 women with normal term pregnancies who underwent elective cesarean section. Twenty women were operated on under general anesthesia, and 20 under epidural anesthesia. For comparison, the same measurements were also made in 10 women who underwent vaginal delivery without signs of intrapartum fetal distress. Maternal venous levels of catecholamines were elevated in all three groups as compared to values in the resting adult. The highest levels were found in the vaginal delivery group (norepinephrine and epinephrine, 3.9 +/- 2.1 and 1.1 +/- 1.0 nmoles/L, respectively), and the lowest in the epidural cesarean section group. Fetal outcomes were similar in all three groups, as judged by Apgar scores and by measurements of umbilical arterial blood gases. In spite of that, neonates delivered vaginally showed a markedly higher sympathoadrenal activation (norepinephrine and epinephrine, 31.8 +/- 24.1 and 5.1 +/- 7.6 nmoles/L, respectively) than those born by elective cesarean section. In the latter group, however, it was found that the type of maternal anesthesia influenced fetal sympathoadrenal activation, since neonatal levels of catecholamines were higher in the epidural section group (norepinephrine and epinephrine, 9.5 +/- 6.4 and 4.0 +/- 4.5 nmoles/L, respectively) than in the general anesthesia group (norepinephrine and epinephrine, 3.2 +/- 2.7 and 1.0 +/- 1.4 nmoles/L, respectively). These results may have a certain clinical relevance since fetal sympathoadrenal activation is thought to promote extrauterine adaptation.

[Use of a ternary mixture of local anaesthetics for peridural anaesthesia during urgent caesarean operation. Report on 125 cases]

125 caesarean operations are conducted under peridural anaesthesia with a mixture of local anaesthetics containing per milliliter: 2.5 mg of bupivacaine, 2.5 mg of etidocaine, 12.5 mg of lidocaine, and 5.10(-6) epinephrine. The dose injected is 23.37 +/- 1.98 ml, the volume necessary for blocking a metamer being 1.18 +/- 0.10 ml/segment. Satisfactory analgesia is obtained in 119 cases (95.2 p. cent), with adequate muscle relaxation in all cases. Block anaesthesia occurs after 5.81 +/- 0.67 min, last 197 +/- 62 min, and enable incision after 8.80 +/- 2.55 min with extraction of the infant after 13.72 +/- 2.85 min in 25 "extremely urgent" cases. Apgar is 8.98 +/- 1.62 after one minute and 9.68 +/- 1.31 after five minutes. These results prove that under perfect circumstances it is possible to get out the baby in about ten minutes.

Comparison of thiopentone and diazepam as induction agents of anaesthesia for Caesarean section

Clinical effects of thiopentone (3 mg/kg body weight) and diazepam (0.3 mg/kg) were compared for elective caesarean sections in two groups of 43 and 39 women, respectively. They were given general anaesthesia in left lateral tilt. The systolic, diastolic and mean arterial pressures were moderately elevated at onset of surgery in both groups, probably indicating light anaesthesia. Later, a gradual decrease to the preinduction levels was observed. The mean injection-delivery (I-D) interval was 344 s in the thiopentone group and 339 s in the diazepam group. The I-D intervals were shorter than 10 min in 39 of the cases in the thiopentone group and 38 cases in the diazepam group. Low Apgar scores at 1 min (6 or less) occurred in five of the neonates in each group, while all had normal Apgar scores at 5 min ( 7 or mor) As judged by the Apgar scores and the acid-base status of umbilical cord blood, the effects of the induction agents on the neonatal condition were indistinguishable in the two groups. In the thiopentone group, unpleasant recollections were reported in 5 out of 40 patients (12.5%) compared to none in the diazepam group. Diazepam-nitrous oxide anaesthesia is well accepted by the mothers and is alternative to supplementing thiopentone induction with a volatile gas for patients who have previous experienced wakefulness or express fear of awareness. The main drawback with diazepam induction, however, is the slow induction of sleep. Harmful drug effects on the neonates must be expected if the dose has to be increased in order to ensure sleep.