Page 755 - ACCCN's Critical Care Nursing

732 S P E C I A LT Y P R A C T I C E I N C R I T I C A L C A R E

have also proven useful. 182,183 Critical illness and its treat-
Practice tip ment induce circumstances that make it difficult to inter-
pret these tests of fetal wellbeing with any certainty, for
Remember that pregnancy is associated with a poor tolerance example, morphine decreases the biophysical profile of
of short-term apnoea, for example during induction of anaes- the fetus. 184 With fetal mortality in pregnant women
6
thesia and/or intubation, and pre-oxygenation is important. admitted to ICU as high as 20%, the assessment of fetal
wellbeing during maternal critical illness is of prime
importance, in part to optimise timing of delivery.
The principles of mechanical ventilation in pregnancy are
the same as those for the non-obstetric population with Cardiotocograph
additional considerations including: Cardiotocographs (CTGs) consist of two pieces of infor-
mation: a Doppler recording fetal heart rate pattern and
l ensure target endpoints reflect the normal ABGs for a pressure transducer detecting uterine muscle contrac-
pregnancy tion. Both elements are recorded on a timed graph so that
l remember that a small reduction in maternal oxygen- one may consider the fetal response to uterine contrac-
ation can severely impact on fetal oxygenation because tion (Figure 26.4). Thus, CTGs provide information about
of the left shift in the oxyhaemoglobin dissociation the fetal heart rate and whether there is any uterine con-
curve associated with fetal haemoglobin 177 traction. A normal fetal heart rate is 120–160 beats/min
l permissive hypercapnia has not been evaluated in with variability in the rate. Details of the patient’s condi-
pregnancy (remember that the fetal carbon dioxide is tion and treatment, and the date and time the recording
higher than the maternal level, given the gradient was taken should be documented on the trace. Many
across the placental membrane) tertiary obstetric hospitals offer a fax CTG interpretation
l Normal tidal volumes in pregnancy are increased by service for general hospitals without maternity staff to
up to 40–50% of non-pregnant values, although the assist with interpretation of CTGs. A CTG provides supe-
mechanical provision of these larger tidal volumes rior information to an intermittent fetal heart rate (by
with respect to volutrauma has not been examined; in stethoscope or Doppler) and should be used when pos-
practice often respiratory rate is increased first and sible. The required frequency and duration of a CTG
then increases in tidal volume are only used when recording will vary according to clinical condition. For
necessary 100 example, suspected placental abruption following blunt
l a nurse caring for a ventilated pregnant patient should trauma may require four hours of continuous moni-
be alert to any patient restlessness or increasing seda- toring. A CTG is recommended during and following
tion requirements and ask for midwifery assistance to elective cardioversion and any other major procedure.
assess for the presence of labour contractions.
CTGs are usually only indicated if the fetus is >22–24
weeks’ gestation and there is the potential to act on
adverse findings, such as emergency delivery. The CTG is
Practice tip an indi cation of fetal wellbeing at the time the trace is
recorded and the fetal condition can change rapidly
Medical staff with experience in the management of a pregnant according to changes in maternal condition.
or difficult airway should be present when a pregnant woman
is intubated. Ultrasound
An ultrasound is able to measure core components of
fetal anatomy, such as head circumference and femur
Other, less common, methods to support gas exchange length, to determine fetal size as well as quantify ade-
have been reported in the literature in the form of case quacy of amniotic fluid volume. Thus ultrasound is used
studies. Of note, nitrous oxide, hyperbaric oxygen treat- to consider adequacy of fetal growth in relation to the
ment and extracorporeal membrane oxygenators have all gestation and is a component of the biophysical profile
been used successfully to treat acute conditions, such as regarding fetal movement and swallowing patterns. Serial
pulmonary embolus, in pregnant women. 178-180 ultrasounds, e.g. weekly, are used to monitor adequate
FETAL ASSESSMENT fetal growth and would be a helpful adjunct to the care
of a pregnant woman in ICU with a long term problem,
Assessment of fetal wellbeing in ICU presents a number such as Guillain–Barré syndrome.
of challenges. Most notable is that many pregnant women
in ICU receive sedative medication which has the effect
of sedating the fetus. The standard methods for Practice tip
moni toring and assessing fetal wellbeing include presence
of fetal movements, continuous cardiotocograph (CTG) There is a legal requirement in both Australia and New Zealand
monitoring, intermittent auscultation of the fetal heart for all births to be registered with the Registry of Births, Deaths
rate, ultrasounds and fetal biophysical profiles. These and Marriages. A birth in both countries is defined as the deliv-
assessments are based on the pattern and rate of the fetal ery of a baby of at least 20 weeks’ gestation or, if gestation is
heart beat, the breathing and swallowing action of the unknown, weighing at least 400 g, who is either live born or
fetus in utero, the volume of amniotic fluid and on fetal stillborn. 185,186
181
movements. Uterine artery Doppler flow measurements