Anaesthetic deaths in the CMACE (Centre for Maternal and Child Enquiries) Saving Mothers’ Lives report 2006–08
Women less likely to die in childbirth in Albania than in UK 
‘There are lies, damned lies, and statistics’. The above comment derives from a statistic, but is it accurate? And if inaccurate, how did this 2010 headline from a respectable newspaper, quoting an original paper in The Lancet , come to be written?
National maternal mortality statistics have been collected in the UK for over 150 years, and the Maternal Death Enquiry (MDE) celebrated its 50th anniversary in 2002 . There is a well-deserved pride in the accuracy of the figures, and major efforts are made to count all cases. Thus, for instance, there was a 22% increase in deaths from the 1991–93 to the 1994–96 reports, owing to the application of computerised searches of death certificate data to identify cases that had not initially been linked to pregnancy .
However, the internationally used measure of Maternal Mortality Ratio (MMR) is defined differently. The MMR numerator uses death certificate data, and includes direct and indirect deaths, but not coincidental or late deaths. In the latest report, 155 out of 261 maternal deaths were identified on death certificates, but an additional 106 cases came to the attention of the Centre for Maternal and Child Enquiries (CMACE) via professionals and CMACE regional managers . Furthermore, the denominator used for the MMR is all live births, whereas for the MDE, the denominator is all maternities in the UK. Thus, this report quotes two UK maternal death rates, the maternal mortality rate of 11.4 per 100 000 maternities and the MMR of 6.7 per 100 000 live births – a striking difference.
This report shows statistically significant decreases in the overall UK maternal mortality rate and deaths directly related to pregnancy, and narrowing in the excess mortality related to area of residence and partner’s unemployment. The strength of the MDE lies in the active changes that the Government and professionals have made to improve the status quo: in the earliest years, haemorrhage, sepsis and anaesthesia; then thromboembolism and suicide; and more recently, a focus on those with social isolation or other underprivileged circumstances. The narrowing of this excess mortality may show that active measures to address health risks have been successful. However, when taking a wider overview of mortality over one or two decades, large percentage fluctuations in the numbers are seen, and it is possible that the decreases noted in the current report may not be sustained. This is not to denigrate the specific attempts that are being made in these areas, but to caution that the task of improving maternal safety is unrelenting, especially with the increasing prevalence of a number of risk factors in the population.
There is one area of bad news contained within the report, however. Last year, CMACE took the unprecedented step of releasing some results in advance, in the first ‘Emergent Theme Briefing’ . There has been a steady increase in deaths over the past 9 years (three triennia) from sepsis, with Group A streptococcal infections accounting for one third. Puerperal streptococcal infections can follow a rapidly escalating course, after beginnings that may involve atypical or non-specific symptoms. As with the symptoms and signs of pulmonary embolus, the key to reducing deaths is partly to increase the index of suspicion among primary care services, and partly to ensure rapid treatment. For sepsis, early ‘blind’ antibiotic treatment is promoted, as well as rapid referral to high dependency care.
The chapter on critical care is a useful accompaniment. It summarises treatment goals and strategies for critical care, particularly in sepsis. However, current sepsis care bundles call for liberal use of intravenous fluids, and some of the sepsis deaths were associated with fluid overload and pulmonary oedema. We have seen a steady decrease in deaths from pulmonary causes in our pre-eclamptic patients over the past 25 years, associated with fluid restriction management strategies . Pregnant women may be particularly susceptible to lung damage because of alterations in fluid dynamics . There is therefore a fine balance in management between maintaining the circulation and risking lung damage. We hope for further useful information on pregnant women admitted to critical care now that this factor is being coded by the Intensive Care National Audit & Research Centre (ICNARC) .
Direct deaths from anaesthesia – the airway
As with the figures for other causes of death, maternal deaths directly attributable to anaesthesia have shown large fluctuations, falling from eight in 1991–93 to one in 1994–96, but averaging five per triennium over the past 15 years . This report numbers seven direct anaesthetic deaths, from disparate causes. There were five at caesarean section. One event occurred at induction and one at reversal of general anaesthesia. One event occurred in the recovery ward and one on the postoperative ward, in women who had had general anaesthesia, although the mechanism was not linked to the mode of anaesthesia. There was a delayed death after spinal anaesthesia. The other two deaths occurred after airway problems: in a postpartum woman on the intensive care unit (ICU); and following a mid-trimester abortion.
Failure to achieve intubation and oesophageal misplacement of the tracheal tube featured in the 2000–02 maternal mortality report and training for this situation was emphasised . There are a number of reasons why a carbon dioxide trace may not appear on a capnograph , but the presence of a normal trace gives unequivocal confirmation of the airway–breathing–circulation triad. In the current report, the first airway-related death involved persistence at intubation attempts after an intubating laryngeal mask airway had been placed. The report references the national Difficult Airway Society ‘rapid sequence induction’ guidelines, written for the non-pregnant adult . These, as well as most obstetric failed intubation guidelines, place a low emphasis on further attempts at intubation after the switch to alternative airway strategies [10, 11]. A fixation by the anaesthetist on the paramount necessity for tracheal intubation may result from fear of regurgitation and pulmonary aspiration in the unconscious woman with an unprotected airway. Guidelines on difficult and failed intubation during rapid sequence intubation suggest consideration of reduced or released cricoid force at multiple stages during laryngoscopy, facemask ventilation and laryngeal mask airway insertion [10, 11]. The logic is that severe hypoxaemia will inevitably be fatal, whereas aspiration is neither inevitable nor necessarily fatal. Upon release of cricoid pressure after intubation at caesarean section, regurgitation is infrequent even though food is often present in the stomach of labouring women .
Prevention of aspiration at induction of anaesthesia is not the whole story, however. One death followed suspected inhalation of gastric contents at extubation. The woman had eaten a meal in hospital before the decision for a category-1 caesarean section. Many anaesthetists in this situation extubate the trachea in the lateral position, after ensuring that functioning protective reflexes have returned. It is unwise to rely on antacid premedication. Prokinetic drugs speed stomach emptying, but do not empty the stomach, and acid neutralisers and secretion blockers will not affect food that is present. Even the use of an orogastric tube does not ensure complete gastric emptying .
The second death from airway problems and failed ventilation occurred in a woman on a critical care ward who had misplacement of her tracheostomy tube. She had had previous problems with the tracheostomy, explained at autopsy by distortion of the trachea with inflammatory tissue. With a combination of reduced deaths from general anaesthesia at caesarean section, and a greater number of very sick women who are cared for on ICU, deaths in the ICU have become a more prominent part of direct anaesthetic deaths over the past decades . One quarter of cases reported to the Fourth National Audit Project (NAP4) of the Royal College of Anaesthetists, which is studying major complications of airway management, have been from the ICU . Difficult airway management facilities, including trolleys with specialised equipment, capnography and access to head and neck surgeons, are worse in critical care units than in the operating suite . Furthermore, the staffing of critical care units has changed, with a greater chance that a non-anaesthetist may be the resident doctor. Attention to management of the difficult airway must be an important priority for all ICU patients, including obstetric cases.
Direct deaths from anaesthesia – other
A woman died unexpectedly on the postoperative ward after caesarean section under general anaesthesia, which had been followed by patient-controlled analgesia for pain relief. Autopsy found high blood levels of morphine. It was noted on the ward that she was sleepy, but other observations were normal including respiratory rate. The report comments that she had been having hourly observations, but was not receiving oxygen or being monitored by pulse oximetry.
It is difficult to be sure whether this death could have been prevented within normal care resources on postnatal wards. The use of obstetric early warning charts was recommended in the 2003–05 report . However, amongst charts in current use, few have ‘sedated but responsive to verbal stimulation’ as an alert variable, and none would trigger a referral to a medical staff member if this was present [7, 17, 18]. We cannot expect ward staff to understand the relationship between hypoventilation and arterial oxygen saturation, or the masking effect of oxygen therapy on the use of pulse oximetry to detect hypoventilation. On the other hand, patients who have particular risk factors, including obesity and markers of sleep apnoea or airway obstruction, should be treated more cautiously.
A woman who had a spinal anaesthetic for caesarean section died 8 days later from acute haemorrhagic leukoencephalitis, an immunological reaction triggered by infection. This was assumed to be precipitated by an extensive spinal canal empyema found at postmortem examination. Infection following obstetric anaesthesia is rare. Obstetric patients accounted for one in three cases of meningitis and one in 15 cases of vertebral canal abscess notified to the NAP3 national audit of complications following neuraxial block, but 45% of the total number of regional anaesthetics performed .
This case reinforces the advisability to use full aseptic technique during regional block. A recent survey of Obstetric Anaesthetists’ Association (OAA) members found that 73% wore hat, gown, gloves and mask for establishing spinal anaesthesia, and 67% do the same for epidural anaesthesia . Chlorhexidine in alcohol is used by 76% of consultant anaesthetists who are OAA members for spinals at caesarean section . Aseptic technique is not amenable to evidence-based proof, although wearing a mask does have powerful indirect support [22, 23]. Meticulous personal practice may bring reassurance in the event of a serious untoward incident inquiry or worse .
A learning point with reference to the case of failed tracheal intubation, in whom there was effective epidural analgesia during labour, is that an epidural catheter used during labour should be topped up without delay when the decision for operative delivery is made. There is continuing debate over whether the top-up should be started in the delivery room before transfer . Maternal deaths from regional anaesthesia in the UK have nearly all been related to high block. If the top-up is started or even completed in the delivery room, the anaesthetist must pay close attention to the patient and prepare for the consequences of spinal or intravenous misplacement of local anaesthetic [26–28].
A death occurred following cardiac arrest in recovery after a mid-trimester abortion. Autopsy showed myocardial scarring which was probably secondary to substance abuse. The report criticises the intravenous administration of Syntometrine® (Alliance Pharmaceuticals, Chippenham, UK) during the operation. Uterotonic drugs all have significant side effects, usually cardiorespiratory . We have learnt the lessons from previous MDE reports that administration of these drugs must be extremely cautious in women who have known cardiac disease or cardiovascular compromise [14, 30]. However, there is a growing number of women with occult cardiac disease and it is therefore wise to develop the habit of slow administration in all cases . An extremely slow or titrated intravenous administration of a vasoactive drug can minimise peak blood levels and also ensure that unlike intramuscular administration, administration can be stopped at any time before the whole dose is given.
Standard of care
Six out of the seven direct deaths due to anaesthesia were judged to have had substandard care. This is consistent with previous reports. There is a presumption that anaesthesia, which is ‘done to’ a patient, should end successfully and that there may be fault if this does not happen. These judgements may occasionally seem to be harsh, a known result of retrospective review when a significant adverse outcome has occurred . However, the purpose of these assessments of quality of care is not to apportion blame, but to ensure that lessons can be learnt from individual cases. The 2000–02 report highlighted the support that individual professionals may require when they are involved in a maternal death, as self-criticism may occur whether the care was deficient or exemplary . In the current report, there were 18 further direct or indirect maternal deaths where peri-operative anaesthetic management contributed or from which lessons could be learnt. As before, failure to recognise serious illness is an important problem. One hopes that the 12 cases where there was a failure of timely anaesthetic or critical care referral will be brought to the attention of other professionals in our maternity teams.
In summary, critical care remains a key area in management of women who die from pregnancy-related causes, as women are ‘saved’ more frequently from an initial catastrophic event or severe illness. Over half of the women who died received critical care. We need to do what we can to ensure that women are referred early for anaesthetic or intensivist consultations, especially in conditions where presentation may be atypical but rapidly progressive, as noted by the Emergent Theme Briefing on sepsis . Airway management in intensive care remains problematic because of patient factors, equipment limitations and the skill mix of medical staff. The decline in opportunities for obstetric general anaesthesia is also a problem, requiring solutions that are, on the whole, outside the obstetric operating theatre. In addition, a national convergence in our guidelines for obstetric failed intubation would be a significant step.
Finally, is the headline that starts this editorial accurate? We can rely on the UK tally for deaths in childbirth, but would have to class the figure from Albania as a Rumsfeld ‘known unknown’ .
SMK is a Regional Anaesthetic Assessor for the CMACE Maternal Death Enquiry.