This study is the first to review obstetric ICU admissions in a regional Australian context. The rate of obstetric admission to the ICU of 0.6% is consistent with other international and Australia studies indicating only a small number of obstetric admission ultimately require critical care intervention8-11, 17. Similarly, despite the relatively higher level of medical co-morbidities and socioeconomic deprivation, the obstetric burden on ICU admissions in Far North Queensland is modest with only 2 percent of admissions attributed to obstetric causes.
The small number of patients in our study limited statistical analysis of risk factors for ICU admission or maternal ‘near miss’. However our data revealed a disproportionate inclusion of Indigenous women with 55% of ICU admission and 60% of maternal ‘near miss’ cases despite comprising roughly one-third of parturients. Although this relationship needs further assessment in a larger study population, the increased Indigenous proportion within our study is in keeping with the greater prevalence of medical comorbidities and socioeconomic deprivation in this sub-group. Our study did not show a trend towards increased morbidity with advancing maternal age or parity seen in other studies6, 11 but obesity remains a prominent factor with morbid obesity (BMI>35) present in 20% of the ICU admissions and 23% of the ‘near miss’ sub-group. Unsurprisingly and consistent with most ICU studies, most admission to ICU occurred in the postpartum period reflecting complications and the need for monitoring in the two most common aetiologies identified: post-partum haemorrhage (PPH) and pre-eclampsia. Delivery by caesarean section occurred in 60% of our cohort – significantly higher than the current unit rate of 32%. Although studies have indicated that caesarean sections, including previous caesarean delivery is associated with significant maternal morbidity18, 19, review of our cases indicated that the higher rate was more reflective of the severity of the underlying conditions and the need for timely delivery. Among our cohort, only eight women had previous caesarean sections with no uterine ruptures or complications at surgery; however two of the ‘near miss’ PPHs resulted from tears at the time of caesarean section.
The most common primary obstetric related diagnosis for ICU admissions were hypertensive disease of pregnancy and obstetric haemorrhage consistent with Australian and international literature.7-11, 17 Of the 18 cases of obstetric hemorrhage, 75% met the WHO near miss criteria predominantly through the need for more than >5U blood transfusion, the need for peri-partum hysterectomy (2) or the need for vasopressors. Indirect Obstetric causes contributed to approximately 40% of ICU admissions with admission for urosepsis and respiratory infections being the most common aetiologies.
Although admission to ICU may appear to be an epidemiologically useful marker of maternal morbidity, our data illustrates that over half of the patients admitted to the ICU were not near misses as classified by the WHO. Many of these cases required closer monitoring post-partum because they were deemed to be ‘high’ risk, rather than requiring any specific critical care intervention. This is particularly noted by the high percentage of women with pregnancy-associated hypertensive disease who had no specific ICU-related intervention apart from invasive arterial pressure monitoring and/or magnesium sulphate infusion. Additionally, one-third of ICU admission were less than 24 hours and along with the relatively low APACHE II scores, indicate the general trend towards admission for monitoring seen in the majority of the cohort. Our study indicated that most significant interventions were confined to ‘near miss’ cases which required comparatively higher rates of critical care support such as inotropic support, mechanical ventilation and blood transfusion. This lower threshold for admission to ICU for monitoring is seen in many well-resourced settings10, 20 and reassuringly reflects the capacity to provide care not available in lower income settings21, 22 but also the lack of development of obstetric high dependency units (HDUs). Studies in larger centres, particularly in the United States have suggested the possible benefits of obstetric HDUs23 including minimising ICU resources, although the value and cost effectiveness of this approach, especially in geographically isolated population regions such as Far North Queensland remains to be validated.
Thirty-one among the 66 cases of ICU admission fulfilled WHO near miss criteria, most of them on the basis of interventional criteria such as transfusion of more than 5U of blood, peri partum hysterectomy, need for mechanical ventilation and the need for ionotropic support. A smaller number were identified through biochemical based criteria such as high creatinine and platelet count < 50 and clinical based criteria such as respiratory rate (RR) >40, shock or cardiac arrest. On their own, some of these latter criteria such as decreased platelets and increased RR per se may not necessarily indicate severe maternal morbidity as most of these cases are managed conservatively without specific intervention. Additionally some cases such as those requiring vasoactive support (adrenaline and metaraminol) may be more reflective of practitioner preference or threshold and incorporation of other interventional criteria would provide more substantiation for fulfilling ‘near miss’ classification. In one instance, a woman received four units of blood and required urgent ligation of the inferior epigastric artery inadvertently damaged at time of drain insertion. Technically this was not a ‘near miss’ as the transfusion requirements were less than the 5 Units required but the requirement for urgent surgery should be an indicator that requires incorporation into any ‘near miss’ criterion. This study along with others undertaken in other centres in Australia3, 24, 25, indicate the WHO near miss classification requires refinement within an Australian setting with the most useful criteria to be based around operative obstetric procedures, the need for blood transfusion and severe organ dysfunction requiring invasive haemodynamic and respiratory support. These interventional criteria are also more easily coded using International statistical classification of Disease (ICD) 10 and Australian Classification of Health Interventions (ACHI) codes and are more amenable to retrospective review. Aspects of the WHO near miss criteria such as biochemical parameters have utility particularly within an ICU setting and can be used to identify cases on a prospective basis but do not have appropriate ICD 10 codes which allow retrospective review. Clinical criteria are not as relevant in this setting as compared to resource-restricted settings where laboratory investigations are hard to attain or interventional criteria difficult to meet21, 22. Further study is required validating the WHO near miss criteria in well-resourced settings such as Australia in particular correlating the criteria to current ICD 10 and ACHI codes to allow easier attainment of ‘near miss’ cases.
In reviewing the 31 cases of near miss, ten were viewed to have some aspect of provider/system related factor contributing the severe morbidity. This is in keeping with previous studies utilising Geller’s preventability model which have shown that about one-third of cases have some level of provider or system related preventability7, 13, 14. Most cases of provider related preventability relate to lack of diagnosis/recognition of decompensation, followed by the lack of ability to undertake the appropriate procedures in a timely fashion. Of note, six of the ten cases of preventability highlighted were from rural or regional centres. It must be emphasised that many of these smaller peripheral units are run by competent Family Medicine or General Practicioner (GP) obstetricians who have a variable skill mix. Despite the small size of these units, many of them have blood products available and operating suite capacity for procedures when required. However, the lack of certain skills such as insertion of Bakri balloon, or identification of bleeding vaginal or cervical tears were limitations noted when cases were reviewed. Also the lack of recognition of decompensation or possibility of complications following childbirth is a major issue with the lack of experience of staff (midwives and doctors) in managing complex obstetric patients. Air transfer support is provided by the Royal Flying Doctors Service (RFDS) and Lifeflight services but often only with one plane/helicopter operational at any one time – sometimes leading to delays in the transfer of patients. Road transport is possible from closer sites within 1.5 hours away but may be severely hampered by flooding in the ‘wet’ or Monsoon season.
This study was a retrospective study and may not have included all ‘near miss’ cases due to exclusion of non-ICU admissions which may contribute to severe maternal morbidity26. However, among the most severe cases, the authors believe that ICU admission remains a very sensitive indicator of severe maternal morbidity. The small number of cases in our study limited statistical significance of different epidemiological factors and ICU admission - larger studies incorporating various hospitals in Northern Queensland over a longer period may help in determining the significance of these associations.
Preventability in the utilised Geller’s model was mainly focused on provider and system related preventability and not on patient factors. Smoking was present as a co-morbidity in nearly half of all ICU admissions and limited antenatal care attendance was a significant contributing factor in at least two of the ‘near miss’ cases. Assessment using a modified Geller’s tool incorporating patient ‘delays’ in future studies may help in identifying patient- associated factors for improvement. Additionally, our preventability review was an internal review subject to bias - external review using trained multidisciplinary cohort of staff may provide a more objective assessment of preventability – this has been successfully undertaken in various local and national settings in New Zealand (NZ) but requires further validation in the Australian setting7, 13, 14