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Sunday June 23rd, 2002 |
From the Department of Anesthesiology, University of Colorado School of Medicine, Denver, Colorado, USA.
Address correspondence to: Dr. Joy Hawkins, Department of Anesthesiology, University of Colorado School of Medicine, 4200 East Ninth Avenue, B-113, Denver, Colorado, USA 80262. Phone: 303-372-6344; Fax: 303-372-6315; E-mail: joy.hawkins{at}uchsc.edu
Amaternal death in labour and delivery is devastating to all involved; after all, only in the obstetric patient can mortality be 200%! Although infant mortality has declined steadily due to increased survival of preterm infants and prevention of SIDS, maternal mortality has remained approximately 7.5 maternal deaths per 100,000 live births over the last 15 years.1 The reason for the lack of improvement is unclear. More than half of maternal deaths are preventable - hemorrhage, pregnancy-induced hypertension (PIH), infection, and ectopic pregnancy account for 59%.
Anesthetic causes have fallen to a "respectable" #6 on the list of causes for maternal mortality in the United States. The causes of pregnancy-related deaths are:2
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Since about 1991, the Centers for Disease Control (CDC) has defined maternal deaths as those which occur within one year of delivery and are related to the pregnancy. Thus the percentage of deaths due to cardiomyopathy has increased because those deaths often occur after a lengthy illness. Many maternal deaths (probably over 30%) are missed because the cause of death on the death certificate does not reflect the fact the patient was pregnant. For example, if a woman dies of a pulmonary embolism but the death certificate does not note she was pregnant, it would not be classified as a maternal death. The CDC has begun asking states to link maternal death certificates with live birth or fetal death certificates, thus increasing identification of maternal deaths.
So what do we know about anesthetic maternal mortality in the United States? In 1987 the Centers for Disease Control and Prevention (CDC) established an ongoing National Pregnancy Mortality Surveillance System to monitor maternal deaths at the national level and conduct epidemiologic studies of the deaths of pregnant women.3 Health departments in all 50 states, the District of Columbia, and New York City provide the CDC with copies of death certificates with patient and provider identification removed. When available, linked birth certificates and fetal death records are also included. These are available from 1979 through 1996. Anesthesia-related deaths are currently being reviewed for 1991–1996.
When these vital statistics data were reviewed,4 the information was very limited, but we attempted to determine the cause of death, the relation to the type of anesthetic, the type of obstetric procedure, and any associated maternal conditions. Many (most?) times the data was woefully inadequate, but CDC has no legal power to obtain medical records, autopsy reports, or other information that might have been helpful.
However, several conclusions could be made. Anesthesia-related maternal mortality rates (per million live births) could be calculated and compared to rates in the United Kingdom since these rates are commonly quoted. They proved to be very similar.
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It also became clear that something had changed during the period of time being reviewed. Although the number of deaths from general anesthesia remained stable, the number of deaths associated with regional anesthesia declined markedly. This occurred despite the fact that regional anesthesia was being used more often for Cesarean delivery in virtually every hospital.5 The decline in deaths associated with regional anesthesia occurred in the mid- 80's, coincident with the withdrawal of 0.75% bupivacaine and probably due to increasing awareness of local anesthetic toxicity and use of a test dose. Using the number of deaths in each six-year period and estimating the number of Cesarean deliveries done under regional or general anesthesia each year (note there are more and more calculations and assumptions!), case fatality rates and risk ratios could be calculated.
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Although the numbers calculated may not be entirely accurate because of all the missing data and assumptions involved, they do show that general anesthesia is riskier than regional in the obstetric patient. Why should that be?
It would appear that maternal mortality will decrease further only by continuing to increase use of regional anesthesia and providing organized airway management programs for our residents so they are prepared for obstetric airway emergencies.6 Even deaths during regional anesthesia may involve airway management. Several of the deaths during regional anesthesia occurred when the block became too high and the airway could not be secured leading to hypoxia and/or aspiration.
On the other hand, there are times when general anesthesia is the most appropriate choice for the patient and it should not be avoided. After all, the mortality rate was 17 per million general anesthetics most recently! That's a remarkable safety record. And we would expect that number to go down even further as additional tools for managing difficult airways [laryngeal mask airway (LMA), Combitube] become more widely available and as the ASA Difficult Airway Algorithm becomes familiar to all practitioners.
Above all, we need more information! We need access to all cases of maternal mortalities in an environment free of concerns about liability issues to understand why they occurred and how to prevent them in the future. And we need to know about "near misses" and how mortalities were avoided. In an area as important as this, we should learn from each other's mistakes so as not to repeat them.
Anesthetic causes of maternal mortality
Management of the difficult airway in obstetrics
The incidence of failed intubation in obstetric patients is 1:280 while the incidence of failed intubation in the general operating room is 1:2230.7,8 Therefore you have over seven times the chance of dealing with a failed intubation while you are providing general anesthesia on the labour and delivery ward (L&D). KNOW THE DIFFICULT AIRWAY ALGORITHM!
Do some advance planning:
If you can't ventilate:
If you can ventilate and need to proceed:
Aspiration of gastric contents
This is still the #1 cause of death in obstetric anesthesia;4 and almost always associated with a difficult or failed intubation, so much of the preceding discussion pertains here. How can we prevent this complication?
Local anesthetic toxicity
Local anesthetic toxicity is the leading cause of death when a regional anesthetic is used, however its occurrence has decreased markedly in the last decade. Prevention centres around incremental dosing and the "test dose". What is an appropriate test dose in obstetrics?
Should test dosing be different for the labouring patient vs the parturient for elective Cesarean delivery? Probably - for elective Cesarean delivery there is less heart rate variability to confuse interpretation of an epinephrine response, and more chance of toxicity with a higher, more concentrated dose of local anesthetic. Does injecting fluid through the needle help decrease the incidence of intravascular catheter placement? Probably - if you use at least a 10-mL volume.20
High spinal or epidural block
More test dose issues... Think about the number of milligrams and the volume you use in your subarachnoid test dose; 60 mg of isobaric lidocaine (3 mL of 2%) will give you a high block. Likewise, even though 10 mL of 0.125% bupivacaine is only 12.5 mg, its isobaricity and volume will cause extensive spread in the cerebrospinal fluid (CSF). Probably the best indicator of a subarachnoid injection is onset; if they are comfortable in one contraction, you're in the CSF until proven otherwise!
Is it safe to perform spinal anesthesia for Cesarean delivery or tubal ligation after a fully dosed but failed epidural anesthetic?21 There are a number of case reports of excessively high blocks requiring intubation in this setting; perhaps because the expanded epidural space volume compresses the CSF and forces the local anesthetic dose higher. After a failed epidural you are balancing the risk of airway management during general anesthesia with the risk of a high block that may also require intubation. If you choose to proceed with spinal anesthesia, anticipate there may be a problem and be prepared for rapid airway intervention.
Anesthetic causes of maternal morbidity
Treatment of postdural puncture headache (PDPH)
Remember that the natural history of a PDPH is to resolve spontaneously in about one week.22 Therefore it may be appropriate initially to handle the situation conservatively with reassurance, oral analgesics, and po caffeine-containing fluids as tolerated.23 However, if the patient is unable to leave the hospital or care for her newborn due to the severity and postural nature of her headache, more aggressive intervention may be indicated. Intravenous caffeine usually provides at least temporary relief, an epidural blood patch is almost always effective, and oral muscle relaxants and/or physical therapy may be helpful with any cervical musculoskeletal component.
"Headache" was the #3 cause of malpractice suits in obstetric patients in the Closed Claims analysis, accounting for 15% of claims. Don't underestimate the importance of this problem to the patient!
Postpartum neurologic deficits
A 1987 review of neurologic deficits after 23,827 deliveries revealed the following:24
A 1995 review of Closed Claims nerve injuries in obstetrics found the most common cause of block-related injury was direct trauma associated with severe paresthesia.25 They also found injuries were more common in Cesarean delivery vs labour, epidural vs spinal, and with a paresthesia vs without. No cases of epidural hematoma were identified in the entire database!
Prior to placing a regional anesthetic, ask the patient if she has had any changes in sensory or motor function of the lower extremities during this pregnancy, and perform a brief neurologic exam of the lower extremities to document motor function, sensation, and reflexes.
Postpartum back pain
Although tenderness at the site of epidural placement lasting a few days is common (as after any injection), back pain occurs with equal frequency with or without use of regional anesthesia. The incidence of back pain is 50% one or two months after delivery26 and 45% 12–18 months after delivery without relationship to the type of anesthesia received.
Side effects of spinal and epidural opiates
Pruritus is most common and can be treated with nalbuphine (2.5–10 mg), propofol (10–20 mg), naltrexone (6 mg), or naloxone (40 µg increments or an infusion). Since the itching is unrelated to histamine release, diphenhydramine is unlikely to be helpful except in providing sedation.
Nausea is most intense after meperidine and lasts longest after morphine. Treatments include nalbuphine, metoclopramide (probably best prophylactically), naloxone, droperidol, possibly propofol, and probably ondansetron.
Closed Claims analysis of obstetric (OB) anesthesia malpractice claims
Critical events involving the respiratory system were the most common precipitating events leading to adverse outcome in both the obstetric and nonobstetric closed-claim files.27 Failed intubation and pulmonary aspiration are more common during administration of general anesthesia in pregnant women than in nonpregnant women.
Maternal closed-claim files include a much higher proportion of relatively minor injuries (e.g., headache, pain during anesthesia, back pain, emotional distress) than do the nonobstetric files.28 In reviewing these records, many patients were unhappy with the intraoperative anesthetic or follow-up care provided and felt themselves ignored, mistreated, or assaulted. Caring and comprehensive discussion with the patient during the preoperative evaluation improves the image of the anesthesiologist and reduces the likelihood of dissatisfaction and possible litigation after unanticipated complications.
Although payments were made in a similar proportion of OB and non-OB claims (52% and 59% respectively), when payments were made, the median payment for OB claims was significantly greater than for non-OB claims ($200,000 vs $100,000 respectively). General anesthesia claims received a higher median payment than regional ($345,426 vs $77,500).
References
1 MMWR. 1998; 47: 705–7.[Medline]
2 Bert CJ, Atrash HK, Koonin KM, Tucker M. Pregnancy-related mortality in the United States, 1987-1990. Obstet Gynecol 1996; 88: 161–7.[Abstract]
3 Ellerbrock TV, Atrash HK, Hogue CJR, Smith JC. Pregnancy mortality surveillance: a new initiative. Contemp Obstet Gynecol 1988; 31: 23–4.
4 Hawkins JL, Koonin LM, Palmer SK, Gibbs CP. Anesthesia-related deaths during obstetric delivery in the United States, 1979-1990. Anesthesiology 1997; 86: 277–84.[Medline]
5 Hawkins JL, Gibbs CP, Orleans M, Martin-Salvaij G, Beaty B. Obstetric anesthesia work force survey, 1981 versus 1992. Anesthesiology 1997; 87: 135–43.[Medline]
6 Tsen LC, Pitner R, Caman WR. General anesthesia for cesarean section at a tertiary care hospital 1990-1995: indications and implications. IJOA 1998; 7: 147–52.
7 Lyons G. Failed intubation. Anaesthesia 1985; 40: 759–62.[Medline]
8 Samsoon GLT, Young JRB. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42: 487–90.[Medline]
9 Rasmussen GE, Malinow AM. Toward reducing maternal mortality: the problem airway in obstetrics. Int Anesthesiol Clin 1994; 32: 83–101.[Medline]
10 Morgan BM, Magni V, Goroszenuik T. Anaesthesia for emergency caesarean section. Br J Obstet Gynaecol 1990; 97: 420–4.[Medline]
11 McClune S, Regan M, Moore J. Laryngeal mask airway for caesarean section. Anaesthesia 1990; 45: 227–8.[Medline]
12 Ferson DZ, Rosenblatt WH, Johansen MJ, Osborn I, Ovassapian A. Use of the intubating LMA-Fastrach in 254 patients with difficult-to-manage airways. Anesthesiology 2001; 95: 1175–81.[Medline]
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Colonna-Romano P, Lingaraju N, Godfrey SD, Braitman LE. Epidural test dose and intravascular injection in obstetrics: sensitivity, specificity, and lowest effective dose. Anesth Analg 1992; 75: 372–6.
14 Colonna-Romano P, Norris MC. Controversies in anesthesia. Anesthesiology Review 1993; 20: 19–24.
15 Grice SC, Eisenach JC, Dewan DM, Mandell G. Evaluation of 2-chloroprocaine as an effective intravenous test done for epidural analgesia. Anesthesiology 1987; 67: A627.
16 Leighton BL, Gross JB. Air: an effective indicator of intravenously located epidural catheters. Anesthesiology 1989; 71: 848–51.[Medline]
17 Yoshii WY, Kotelko DM, Rasmus KT, et al. Fentanyl for epidural intravascular test done in obstetrics. Reg Anesth 193; 18: 296–9.
18 Norris MC, Fogel ST, DalmanH, et al. Labor epidural analgesia without an intravascular test dose. Anesthesiology 1998; 88: 495–501.[Medline]
19 Leighton BL, DeSimone CA, Norris MC, Chayen B. Isoproterenol is an effective marker of intravenous injection in laboring women. Anesthesiology 1989; 71: 206–9.[Medline]
20 Mannion D, Walker R, Clayton K. Extradural vein puncture - an avoidable complication. Anaesthesia 1991; 46: 585–7.[Medline]
21 Gupta A, Enlund G, Bengtsson M, Sjoberg F. Spinal anaesthesia for caesarean section following epidural analgesia in labour: a relative contrainduction. Int J Obstet Anesth 1994; 3: 153–6.
22
Berger CW, Crosby ET, Grodecki W. North American survey of the management of dural puncture occurring during labour epidural analgesia. Can J Anaesth 1995; 45: 110–4.
23
Camann WR, Murray RS, Mushlin PS, et al. Effects of oral caffeine on postdural puncture headache. Anesth Analg 1990; 70: 181.
24
Ong BY, Cohen MM, Esmail A, et al. Paresthesias and motor dysfunction after labor and delivery. Anesth Analg 1987; 66: 18.
25 Chadwick HS, Gunn HC, Ross BK, Glosten B, Posner K. Nerve injury and regional aneshesia in obstetrics - a review of the ASA closed claims project database. Anesthesiology 1995; 83: A951.
26 Breen TW, Ransil BJ, Groves PA, Orial NE. Factors associated with back pain after childbirth. Anesthesiology 1994; 81: 29–34.[Medline]
27 Chadwick HS, Posner K, Caplan RA, et al. A comparison of obstetric and nonobstetric anesthesia malpractice claims. Anesthesiology 1991; 74: 242–9.[Medline]
28 Chadwick HS. An analysis of obstetric anesthesia cases from the American Society of Anesthesiologists closed claims project database. IJOA 1996; 5: 258–63.
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