CEMACH

Chapter 19: Critical Care

Tom Clutton-Brock

Introduction

A chapter on Intensive Care is now a well established feature of this Report and for this triennium the name has been changed to Critical Care in order to bring it into line with internationally accepted definitions. A common criticism levelled at this type of publication is that similar messages are repeated from one report to another and Critical Care will be no exception. The very fact that similar conclusions appear is in itself a salutary message; we are of course dealing with rare events and will never achieve a rate of zero. Every death remains a tragedy and any lessons that can be learnt deserve repetition and reinforcement.

A further criticism is that denominator data are missing for many of the causes of death investigated. Until recently the largest Critical Care obstetric dataset from the UK was that reported by Hazelgrove et al1, who collected data on admissions to 14 general Critical Care Units in the South West Thames region. They identified 1.8% of all admissions (210 out of 11,385 cases) to be related to pregnancy. More recently, in 2005, the Intensive Care National Audit and Research Centre (ICNARC) published a study looking at the case mix, outcome and activity for obstetric admissions to adult, general Critical Care Units2.

Of 219,468 admissions in the ICNARC Case Mix Programme Database (CMPD), 1452 (0.7%) were identified as Direct obstetric admissions. A further 278 admissions were identified as Indirect or Coincidental obstetric admissions by the presence of an obstetric code in the 'Other conditions relevant to the admission' or a partially completed obstetric code in any field. Additionally, 175 admissions matched one or more of the terms used in the text field search. Of these, 164 clearly met the condition of 'being pregnant or having recently been pregnant' and the remaining 11 were excluded. This left a total of 450 Indirect or Coincidental obstetric admissions (0.2% of all CMPD admissions). The comparison group of all non-obstetric female admissions aged 16–50 years consisted of 22,938 admissions (10.5% of all CMPD admissions). In total, the 1902 obstetric admissions represented 0.9% of all CMPD admissions and 7.7% of all female admissions aged 16–50 years. After adjusting for the changing units participating in the CMP, there was no significant trend over time. On average only 7 per 1000 intensive care admissions will be obstetric patients and even a large unit will only see five to six women each year. It is hardly surprising then that very few intensivists will have had much exposure to the critically ill obstetric patient.

Similarly only a very small proportion of obstetric patients will end up in an Intensive Care Unit (ICU). A study of 435 obstetric patients admitted to ICUs in France3  estimated that the frequency was 36 per 100,000 live births. The mortality was lower with scheduled cases. In a Canadian study in 19994 over 14 years, between 1980 and 1993, 0.7 per thousand women required transfer for critical care. The main reasons for transfer were hypertensive disease (25%), haemorrhage (22%) and sepsis (15%). Wheatley et al5 .reviewed the predictability of admissions to their ICU; they found that 67% of women had no previous medical or obstetric history. As in other series, the major reasons for admission were hypertensive disorders of pregnancy (66%) and haemorrhage (19%); 79% followed caesarean section and 40% required ventilatory support. Using these figures as an estimate a busy obstetric unit with say 6,500 deliveries per year will on average only send five women to intensive care each year. This number will include both survivors and non-survivors.

Another important finding from the ICNARC review of obstetric patients on intensive care was the low mortality observed in obstetric patients. The South West Thames study had reported a mortality of 3.3%. The ICNARC study found only 2.2% of patients with Direct obstetric admissions dying before ultimate discharge from hospital, versus 6.0% among Indirect or Coincidental obstetric admissions and 19.6% among female non-obstetric admissions aged 16–50 years (χ2 test, P < 0.001). In summary then 96% of obstetric admissions to intensive care survive. Combining this with the figures above we can roughly estimate that a busy obstetric unit will have a death in a Critical Care Unit approximately once in every five years.

Obstetric patients may well be a fitter and younger group than the aged matched control group. The ICNARC study showed that the widely used Acute Physiology and Chronic Health Evaluation (APACHE) II severity scoring and mortality prediction model was poorly calibrated for the obstetric patients and significantly overestimated their risk of death. This would support the view that this group of patients do better than predicted by any existing model.

These data also support the view that, overall, the care of the critically ill obstetric patient both before and during their stay in Critical Care must be of a high standard and that reports dealing only with mothers who have died must be set in this context.