Susan K. Palmer

Anesthesia-related Deaths during Obstetric Delivery in the United States, 1979–1990

Background Anesthesia‐related complications are the sixth leading cause of pregnancy‐related death in the United States. This study reports characteristics of anesthesia‐related deaths during obstetric delivery in the United States from 1979–1990. Methods Each state reports deaths that occur within 1 yr of delivery to the Centers for Disease Control and Prevention as part of the ongoing Pregnancy Mortality Surveillance. Maternal death certificates (with identifiers removed) matched with live birth or fetal death certificates when available from 1979–1990 were reviewed to identify deaths due to anesthesia, the cause of death, the procedure for delivery, and the type of anesthesia provided. Maternal mortality rates per million live births were calculated. Case fatality rates and risk ratios were computed to compare general to regional anesthesia for cesarean section deliveries. Results The anesthesia‐related maternal mortality rate decreased from 4.3 per million live births in the first triennium (1979–1981) to 1.7 per million in the last (1988–1990). The number of deaths involving general anesthesia have remained stable, but the number of regional anesthesia‐related deaths have decreased since 1984. The case‐fatality risk ratio for general anesthesia was 2.3 (95% confidence interval [CI], 1.9–2.9) times that for regional anesthesia before 1985, increasing to 16.7 (95% CI, 12.9–21.8) times that after 1985. Coclusions Most maternal deaths due to complications of anesthesia occurred during general anesthesia for cesarean section. Regional anesthesia is not without risk, primarily because of the toxicity of local anesthetics and excessively high regional blocks. The incidence of these deaths is decreasing, however, and deaths due to general anesthesia remain stable in number and hence account for an increased proportion of total deaths. Heightened awareness of the toxicity of local anesthetics and related improvements in technique may have contributed to a reduction in complications of regional anesthesia.

Anesthesia-Related Maternal Mortality in the United States : 1979-2002

OBJECTIVE: To examine 12 years of anesthesia-related maternal deaths from 1991 to 2002 and compare them with data from 1979 to 1990, to estimate trends in anesthesia-related maternal mortality over time, and to compare the risks of general and regional anesthesia during cesarean delivery. METHODS: The authors reviewed anesthesia-related maternal deaths that occurred from 1991 to 2002. Type of anesthesia involved, mode of delivery, and cause of death were determined. Pregnancy-related mortality ratios, defined as pregnancy-related deaths due to anesthesia per million live births were calculated. Case fatality rates were estimated by applying a national estimate of the proportion of regional and general anesthetics to the national cesarean delivery rate. RESULTS: Eighty-six pregnancy-related deaths were associated with complications of anesthesia, or 1.6% of total pregnancy-related deaths. Pregnancy-related mortality ratios for deaths related to anesthesia is 1.2 per million live births for 1991–2002, a decrease of 59% from 1979–1990. Deaths mostly occurred among younger women, but the percentage of deaths among women aged 35–39 years increased substantially. Delivery method could not be determined in 14%, but the remaining 86% were undergoing cesarean delivery. Case-fatality rates for general anesthesia were 16.8 per million in 1991–1996 and 6.5 per million in 1997–2002, and for regional anesthesia were 2.5 and 3.8 per million, respectively. The resulting risk ratio between the two techniques for 1997–2002 was 1.7 (confidence interval 0.6–4.6, P=.2). CONCLUSION: Anesthetic-related maternal mortality decreased nearly 60% when data from 1979–1990 were compared with data from 1991–2002. Although case-fatality rates for general anesthesia are falling, rates for regional anesthesia are rising. LEVEL OF EVIDENCE: II

Lidocaine and bupivacaine differential blockade of isolated canine nerves.

In vitro studies of pharmacologic actions of local anesthetics are usually performed at room temperature using amphibian nerves exposed to local anesthetics for substantial periods of time. We performed in vitro studies of pharmacologic responses of motor A fibers and sensory C fibers to lidocaine and bupivacaine in clinically effective concentrations using a canine nerve preparation at body temperature with short exposure times to evaluate responses under clinically relevant conditions. Differential blockade of isolated, desheathed phrenic and vagus nerves was achieved with bupivacaine (0.58 mM), C fibers being blocked before A fibers (P < 0.05). Lidocaine (2.8 mM) did not block A and C fibers differentially.

Continuous epidural analgesia for cesarean section in a patient with morbid obesity.

A 20-year-old white woman, gravida 3 para 1, 177 cm tall and weighing more than 182 kg (scale not readable over 400 pounds), was admitted for an elective repeat cesarean section. Past medical history included chronic hypertension with blood pressure in the range of 160/110 torr. During her pregnancy she was treated with phenobarbital, 15 mg, 4 times a day. Past history included two general anesthetics, one for her primary cesarean section and one for uterine dilation and curettage. She denied shortness of breath or periodic somnolence. Laboratory data were within normal limits. Preoperative medication consisted of oral antacid 45 minutes prior to induction. With an 18-cm thigh cuff applied to her arm, pre-anesthetic blood pressures in the range of 115

Mainstem bronchial rupture during general anesthesia.

this laboratory; the level of 3.0 in this patient is clearly abnormal (Personal communication. Perna VP: Director, Smith Kline Clinical Laboratories Inc.). Two weeks later a second plasma cholinesterase level was still elevated, 2.74 delta pH units/hr, more than 4 SD above the mean. The second serum cholinesterase level verifies the original abnormal level and suggests that repeated succinylcholine administration had no significant effect on enzyme levels or activity. In summary, a 52-year-old man undergoing thiopental-succinylcholine anesthesia for administration of electric shock treatments did not demonstrate clinical fasciculations and muscular relaxation from succinylcholine given in the doses we are accustomed to administering. He showed unusually strong somatic reaction to applied electric shock. Venous blood samples showed elevated serum cholinesterase levels of a normal type. Based upon this elevated serum cholinesterase level and observed clinical changes in patient response to electric shock treatment with increased amounts of succinylcholine, it is hypothesized that the elevated concentration of normal serum cholinesterase produced unusually rapid hydrolysis of the succinylcholine resulting in apparent resistance.

Routine pregnancy testing before elective anesthesia is not an American society of anesthesiologists standard

cell salvage throughout the operative period and over the first 6 h in critical care. This does not necessarily mean that a substantial mass of red cells was actually lost, but may be as a result of gross hemodilution during the procedure, which would explain why the hemoglobin concentration in both the treatment and the control group were similar. As we stated in the discussion, the study was not powered for hemoglobin concentration, so any conclusions in this area may not be valid.

Anesthesia-related Maternal Mortality in the United States: 1979–2002

(Obstet Gynecol. 2011;117(1):69–74)

Anesthesia-Related Maternal Mortality in the United States: 1979–2002

The death rate from the complications of pregnancy has decreased by 99% since 1900, but no further decreases have been reported in the past 20 years. Among women who die after a live birth, the leading causes of death are embolism and hypertensive disorders of pregnancy. Anesthetic causes of maternal mortality have declined even more than obstetric causes and now account for <2% of pregnancy-related maternal mortality in the United States. This study examined 12 years of anesthesia-related maternal deaths from 1991 to 2002 and compared them with data from 1979 to 1990 in an effort to find trends in anesthesiarelated maternal mortality over time and to compare the risks of general and regional anesthesia during cesarean delivery. The Pregnancy Mortality Surveillance System of the Centers for Disease Control and Prevention maintains a database of all reported deaths that are causally related to pregnancy. A woman’s death is classified as pregnancy-related if it occurred during pregnancy or within 1 year of pregnancy and resulted from complications of the pregnancy, a chain of events initiated by the pregnancy, or an aggravation of an unrelated condition by the physiologic effects of pregnancy or its management. Of the 5946 pregnancy-related deaths in the database for 1991 to 2002, 86 were determined to be caused by anesthesia-related complications which 3 obstetric anesthesiologists independently confirmed. The type of anesthesia involved, mode of delivery, and cause of death were extrapolated from the database. Pregnancy-related mortality ratios, defined as pregnancy-related deaths due to anesthesia per million live births were calculated. Case-fatality rates were determined by dividing number of deaths due to regional and general anesthetics by the estimated number of instances of that type of anesthesia during cesarean delivery in the same period. To compare the data from the United States with that from the United Kingdom, pregnancy mortality rates were calculated by triennium. The 86 pregnancy-related deaths associated with complications of anesthesia accounted for 1.6% of the total pregnancy-related deaths in the United States. The overall pregnancy-related mortality ratios for deaths related to anesthesia complications were 1.2 and 2.9 per million live births for 1991 to 2002 and 1979 to 1990, a decrease of 59%. Of the 86 deaths, 27 early losses were excluded (24 abortion and 3 ectopic deaths) and 3 deaths were excluded because of unknown pregnancy outcome. The 56 remaining cases resulted in a live birth or stillbirth. Pregnancy-related deaths connected with anesthesia mostly occurred among younger women, aged 20 to 24 years, 27% for 1991 to 2002, and 43% for 1979 to 1990. However, deaths among women aged 45 to 49 years increased from 5% for 1979 to 1990 to 18% for 1991 to 2002. The delivery method was determined in 86% of women who died during 1991 to 2002 and of these 86% underwent a cesarean delivery. No known death was associated with a vaginal delivery for 1991 to 2002. The estimated case fatality rate of general anesthesia during cesarean delivery decreased from 16.8 deaths per million general anesthetics to 6.5 deaths per million general anesthetics between 1991 to 1996 and 1997 to 2002. The estimated case fatality rate of regional anesthesia during cesarean delivery increased from 2.5 to 3.8 deaths per million. The leading causes of anesthesia-related pregnancy deaths for 1991 to 2002 were intubation failure or induction problems (23%), respiratory failure (20%), and high spinal or epidural block (16%). For women whose deaths were associated with regional anesthesia during cesarean delivery, 26% were caused by high spinal or epidural block, 19% by respiratory failure, and 19% were due to drug reaction. The present Pregnancy Mortality Surveillance System is the most comprehensive national database available for the analysis of maternal death in the United States, but maternal mortality data are difficult to collect, particularly for individual cases with a bad outcome or “near miss.” Reporting of deaths and the sequence of events, including provision of anesthesia records, should be mandatory if concerns about liability can be overcome. Anesthetic-related mortality from 1991 to 2002 declined greatly when compared with data from 1979 to 2000. Although death rates from general anesthesia are falling, fatality rates from regional anesthesia are rising.

Comparison of 0.5% and 0.75% Bupivacaine for Epidural Anesthesia in Cesarean Section

&NA; Twenty‐eight patients given 18 to 22 ml of 0.5% bupivacaine epidurally for elective cesarean section were studied for the level of blockade and need for anesthetic supplementation. The results were compared to a retrospectively studied group of 78 women who had had epidurals with 14 to 20 ml 0.75% bupivacaine. There was no significant difference between the two groups in the need for anesthetic supplementation (32.1% for the 0.5% bupivacaine group, 33.3% for the 0.75% group) or in mean height of block (approximately T‐4 for both groups).

Distance from the Skin to the Lumbar Epidural Space in an Obstetric Population

Lumbar epidural blocks are frequently requested for analgesia during labor and delivery. Training anesthesia personnel to safely perform these blocks can be difficult because the epidural space must be identified by how the needle placement feels. The depth of the epidural space beneath the skin surface varies at different levels of the spinal column in the same patient. It also varies from patient to patient at the same vertebral level. We studied the distance from the skin to the mid-lumbar epidural space in an obstetric population to determine whether there is any systematic relationship between patient height and weight and the distance from the skin to the epidural space.