Saving Mothers' Lives: - Public Health Agency for Northern Ireland

Modifi ed early warning scoring systems
The well recognised problems of recognising life threatening illness has led to the introduction of a number
of early warning scoring systems (EWS), also known as patient at risk scores (PARS) or modifi ed early
warning scores (MEWS) 6 . An EWS is calculated for a patient using fi ve simple physiological variables:
Mental response, pulse rate, systolic blood pressure, respiratory rate and temperature. For patients who
are postoperative or unwell enough to be catheterised a sixth variable, urine output can also be added. The
principle is that small changes in these fi ve variables combined will be seen earlier using EWS than waiting
for obvious changes in individual variables such as a marked drop in systolic blood pressure which is often
a pre-terminal event. Of all the variables, respiratory rate is the most important for assessing the clinical
state of a patient but is the one that is least recorded. Respiratory rate is thought to be the most sensitive
indicatory of a patient’s physiological well-being. The changes in physiology seen in normal pregnancy
mean that any scoring system may need to be modifi ed for this group of patients as pregnancy progresses.
The poor calibration of scoring systems for obstetric admissions supports this theory 2 but does mean that
the error will be on the safe side, i.e. mothers will be referred earlier than may be necessary.
Modifi ed early obstetric warning scoring system (MEOWS)
Some units have produced their own scoring systems modifi ed for obstetric patients and the one
reproduced in the Annex to this Chapter has been developed by Aberdeen Maternity Hospital and is
reproduced with their kind consent.
Box 19.2
Critical Care learning points: early warning scores
Modifi ed early warning scoring systems improve the detection of life threatening illness.
Some modifi cation of the physiological limits set may be required later in pregnancy.
However, the detection of life threatening illness alone is of little value. It is the subsequent management
that will alter the outcome.
On their own, though, MEOWS can only be part of the solution, as it is the response to the abnormal score
that will determine any real change in outcome:
A woman was admitted with a diagnosis of ovarian hyper-stimulation syndrome (OHHS), and was
pyrexial and tachycardic on admission. A couple of days later she was short of breath at rest with
pulse oximeter saturations of 89%, a blood pressure recorded as 146/34 mm/Hg and a reduced
urine output. She was found to have bilateral effusions and ascites. The nursing staff placed
her under increased observations and used a MEWS chart. Critical care referral and blood gas
analysis were suggested to the junior medical staff who decided to do neither. Shortly afterwards,
with her decline carefully charted but no action taken, she had a pulse rate of 176 bpm and an
un-recordable blood pressure. She died of her pneumonia on the Critical Care Unit.
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