Analgesia, Anaesthesia and Pregnancy. 4th Ed. Róisín Monteiro

Chapter 156. Modified early obstetric warning scores

Improving the care of the critically unwell obstetric patient is repeatedly mentioned in the Confidential Enquiries into Maternal Deaths (CEMD) reports, with early recognition of deterioration highlighted as a key aim; when clinical deterioration occurs it can be rapid in the parturient.

Use of an early warning score has been recommended since the 2003-2005 Enquiry; such a score can be used to identify patients with observations that are outside a predefined range, to trigger a graded response. It is thought that by using a scoring system, smaller changes in clinical condition will be detected earlier than by waiting for an obvious picture of deterioration to emerge. Their utility depends upon partial physiological decompensation that is recognised and acted upon during a window of opportunity before full decompensation.

A 2014 survey of practice indicated that use of an obstetric early warning score was universal across the UK hospitals surveyed, a dramatic improvement over the previous 10 years.

Problems and special considerations

The standardised National Early Warning Score (NEWS) chart cannot be applied to the obstetric population, given the altered physiology of pregnancy, so modified early obstetric warning scores (MEOWS) have been developed to identify women with observations outside the expected norm. A MEOWS chart would usually be used from 20 weeks’ gestation until 6 weeks postpartum.

Parameters looked at may include systolic and diastolic blood pressure, respiratory rate, heart rate, fractional inspired oxygen required to maintain an oxygen saturation of at least 96%, temperature, and level of consciousness (Figure 156.1). Of all the variables recorded, a change in respiratory rate is the most sensitive, but is often the parameter that is poorly measured or not recorded. The parameters recorded take into account the altered physiology of pregnancy, for example a higher heart rate and respiratory rate.

MEOWS charts are colour-coded as a visual cue to the severity of abnormal parameters. The National Institute for Health and Care Excellence (NICE) has recommended that early warning scores trigger three grades of response: a low-score group that results in increased frequency of observations and alerting of the nurse in charge; a medium-score group, resulting in an urgent call to the medical team caring for the patient; and a high-score group resulting in an emergency call to a team with critical care competencies. The actual response is subject to local policy and dependent on local skill mix and staff.

Figure 156.1 Example MEOWS chart. Many units have added additionallines, e.g. for recording neurological status, pain, nausea, state of liquor/lochia, etc. Each variable is scored according to the values present

Management options

A standardised MEOWS chart has been recommended in the CEMD reports, but a national evidence-based standard has not emerged. There are many variations in existence and some have not been validated; many scores have been designed through clinical consensus rather than through research or statistical analysis. Studies have suggested that MEOWS charts can over-detect severe sepsis, and that simpler tools are more sensitive. A scoring system based on an example MEOWS in the 2003-2005 CEMD report was validated for use at detecting maternal morbidity using data from a single centre. A scoring system has been developed through clinical and statistical analysis using the UK’s Intensive Care National Audit and Research Centre (ICNARC) Case Mix Programme database, which has demonstrated excellent discrimination between survivors and non-survivors; its applicability to morbidity on the labour ward, however, has not been validated.

More recently, multidisciplinary work suggests that only six parameters should contribute to the score: respiratory rate, oxygen saturation, heart rate, systolic blood pressure, diastolic blood pressure, and temperature. Any other observations that may be useful in obstetric patients, such as urine output or lochia, should be recorded separately, so as not to confuse documentation. It has also been pointed out that altered level of consciousness is not an early warning sign.

An important feature of MEOWS charts is that they need to be applied to all women in the unit, not just to those considered at high risk, since experience has shown that identifying the latter group is unreliable unless a systematic scoring system is used.

Key points

• Use of a modified early obstetric warning score (MEOWS) can help to identify the deteriorating parturient. However, once identified, appropriate action must be triggered by present scores.

• For a screening tool to be effective it must be safe, cost-effective and validated.

Further reading

Carle C, Alexander P, Columb M, Johal J. Design and internal validation of an obstetric early warning score: secondary analysis of the Intensive Care National Audit and Research Centre Case Mix Programme database. Anaesthesia 2013; 68: 354-67.

Isaacs RA, Wee MY, Bick DE, et al.; Modified Obstetric Early Warning Systems Research Group. A national survey of obstetric early warning systems in the United Kingdom: five years on. Anaesthesia 2014; 69: 687-92.

McGlennan AP, Sherratt K. Charting change on the labour ward. Anaesthesia 2013; 68: 338-42. Quinn AC, Meek T, Waldmann C. Obstetric early warning systems to prevent bad outcome.

Curr Opin Anaesthesiol 2016; 29: 268-72.

Singh S, McGlennan A, England A, Simons R. A validation study of the CEMACH recommended modified early obstetric warning system (MEOWS). Anaesthesia 2012; 67: 12-18.