The Pregnant Patient And Trauma

Although trauma in some form occurs in 6-7% (Hoff et al. 1991) of all pregnancies, severe trauma occurs   in about 1/200 pregnant women, the common causes being MVA (see Fig. 33.1) and physical abuse. In such severe cases, maternal mortality is 10% and fetal loss can be as high as 15% (Kissinger et al. 1991). Lesser degrees of trauma pose a smaller risk to the mother. However, fetal loss, even from the most minor of physical blows can be significant. It is, therefore, important that the carer of first contact who may not have advanced training in Obstetrics understands maternal indicators especially in the first 24 hours after the trauma which may predict preventable fetal demise. The fact that maternal mortality from trauma has not altered over 20 years and that trauma is a major cause of mortality in the first four decades of life shows that the pregnant woman is vulnerable. The gravid uterus is mobile and vascular and a potential source of haemorrhage after trauma. Physiological changes in other organs increase the vulnerability and may also mask or mimic abnormality in vital signs. In Australia, as in other countries of the developed world, trauma is a significant cause of maternal mortality. The fetus has special risks because blood loss may not be immediately obvious. Careful and specialized assessment over a 72 hour period following injury is, therefore, essential.

Key points •

Severe trauma occurs in about 1/200 pregnant women

•

In such severe cases, maternal mortality is 10% and fetal loss can be as high as 15%

Mechanism of injury and physiological changes in pregnancy Anatomical and physiological changes in pregnancy are enormous. Those relevant to trauma are: Blood Vessel wall changes Changes in the collagen of vessel walls in pregnancy leaves them softer, distenable and more susceptible to damage. Placentation The formation of the placenta from the earliest weeks of pregnancy is a complicated process enabling fetal and maternal circulations to be separated by cellular membranes, thus allowing an exchange of gases, nutrients and waste products. As a result of this, fetal haemorrhage into the maternal circulation is common and may be augmented by

even minor trauma.

Rapid enlargement of the uterus The enlargement of the uterus makes it susceptible to direct trauma as it becomes an abdominal rather than a pelvic organ protected by the bony pelvis. Cardiovascular changes

There is a 30% increase in blood volume by 28 weeks gestation. This allows women to tolerate up to 1.5L of blood loss before a change in routine vital signs occurs (Dilts et al. 1969). Pulse rate is increased by 1015 beats per minute in pregnancy and this may mimic haemodynamic instability. Presentation and triage The triage of the injured pregnant woman and her immediate management is dependant on damage to organs other than those related to the pregnancy. Severe neurological, limb and vascular damage will clearly take priority. These will interact with her pregnant state especially in later pregnancy when the fetus is viable (after 23 weeks gestation) and may create a dilemma between saving the fetal life by Caesarean section and compromising maternal stability when the mother is badly or fatally injured. It is important that non obstetric surgery is not withheld for the sake of the fetus. If surgery is undertaken such procedures will enhance the thrombophilic changes of pregnancy and will induce the output of endogenous prostaglandins. Prophylactic methods to decrease the risk of venous thrombosis should be adhered to and considered the use of an antiprostaglandin such as Indomethacin should be used. Intraoperatively, fetal hypoxaemia should be diagnosed early by the use of cardiotocograph if that is logistically possible. Key points •

It is important that non obstetric surgery is not withheld for the sake of the fetus.

The decision for Caesarean section in the living but severely injured woman or post mortem Caesarean section is always difficult. Time may not permit the ideal of consultation with Anaesthetists, Intensive Care Physicians, Neonatologists and skilled Obstetricians. Fetal compromise is often rapid when the mother is haemodynamically unstable which raises the following questions in the management of a severely injured mother with a viable fetus: i)

When to deliver the baby.

ii)

Where to deliver the baby.

iii)

How to deliver the baby.

All three questions may be immediately obvious, e.g. when the mother is dead or about to die, the fetal heart is audible, but signs of fetal hypoxia are present and the gestational age of the fetus is beyond 23 weeks. In this situation, the fetus must be delivered immediately and the courageous decision in a medical world of criticism and litigation must be dealt with wherever the situation arises. All that is required is a scalpel, a midline incision and a classical Caesarean section. A pfannensteil incision and lower segment Caesarean section is quick in the hands of a trained Registrar in a hospital. This is the usual person called upon to make such decisions. Transfer from an Accident & Emergency ward to an Operating Theatre may be a death sentence for the fetus, and occasionally, the correct decision is to carry out a post mortem Caesarean section in the Accident & Emergency ward. Much more judgement than courage is necessary in the second category of injured pregnant women, that is, when the injuries are life threatening but not immediately a problem. The principles in these situations

are: i)

Adequate maternal fluid replacement and oxygenation.

ii)

Monitoring by cardiotocography.

iii)

Exclusion of fetal haemorrhage.

iv)

Nursing with a 15 degree lateral tilt.

v)

Constant review by the perinatal team.

vi)

Monitor the maternal serum bicarbonate level.

Apart from death, the most common indicator of a poor fetal outcome is the degree of trauma (Dilts et al. 1969). Notwithstanding this fact, even the most severely traumatized women may have a live fetus. Maternal tissue hypoperfusion leading to fetal hypoxia is the commonest mechanism of fetal death. It has been shown that the variable most commonly associated with fetal loss is maternal serum bicarbonate on admission (Dilts et al. 1969). Keeping the mother in optimum fluid and blood gas equilibrium is not only best for her but crucial to fetal survival. Meticulous care of these factors in the injured pregnant women is critical because the mother may compensate by vaso-constriction at the expense of the fetus. Vasoconstriction can also occur as a result of a release of thromboxane and prostaglandins leading to cerebral ischaemia. The third category of injured pregnant women is where the injury has been slight. These women are often sent home or relegated to a ward where there is no obstetrical expertise. All injured pregnant women must be carefully monitored for 72 hours by as expert a team as the hospital has available. Slight injuries to the abdomen, especially seat belt injuries may result in delayed or undiagnosed fetal haemorrhage. Steroids to hasten lung maturation should be considered even if delivery can be predicted 6 hours prior to the event. Intravenous steroids may be of use at an appropriate gestational age. This decision must be discussed with the Obstetrician and Neonatologist. A single intravenous injection of 12mg of Dexamethasone 6 hours prior to surgery may be useful in avoiding the later pulmonary complications in the Neonatal Intensive Care Unit. Key points •

Steroids to hasten lung maturation should be considered even if delivery can be predicted 6 hours prior to the event

In women in early pregnancy, the avoidance of unnecessary radiographic examination is important. Drost et al. (Drost et al. 1990) in the examination of a series of pregnant women suffering major trauma noted that 92% underwent at least one diagnostic radiographic examination. Most underwent multiple studies. There is a teratogenic potential with radiation doses in excess of 10 rads (Mossman and Hill 1982) and also an increase in the incidence of childhood cancers. For these reasons and especially in women in early pregnancy, selecting imaging methods such as ultrasound which do not involve radiation, positioning patients optimally, questioning critically the usefulness of the anticipated procedure and careful shielding of

the abdomen with lead aprons should be carried out. In most trauma cases it is possible, using these means, to keep the total radiation dose to the gravid uterus below 10 rads. Table 33.2 gives a guide to radiation doses from common radiological studies in injured patients. Key points •

In women in early pregnancy, the avoidance of unnecessary radiographic examination is important

Women in early pregnancy (up to 12 weeks gestation) rarely have direct trauma to the uterus because it is protected by the pelvis. The large mobile organ can, however, undergo “whiplash” injuries with consequent rupture of the relatively softer vessels in the broad ligament. This should be considered when unexplained blood loss is encountered. Key points •

The large mobile uterus can undergo “whiplash” injuries

Diagnosis of fetoplacental trauma Trauma during pregnancy is associated with a high rate of fetal death (Kettel et al. 1988). This is mostly associated with occult fetal haemorrhage and may occur with even minimal maternal injury. Early diagnoses and constant effective surveillance in the 72 hours after trauma to the pregnant woman are the important issues for maximizing fetal well being. Clinical Examination The Medical Officer in Accident & Emergency ward may have only rudimentary training in Obstetrics. This medical officer is most often the first to see the patient. It is important that the following are noted and recorded: i)

Bruises on the abdomen especially from seat belts.

ii)

The presence and severity of uterine tenderness.

iii)

The presence of uterine contractions.

iv)

The vaginal passage of blood, liquor and liquor containing meconium.

v)

The presence of a fetal heart beat and its rate.

Cardiotocography In the second half of pregnancy, this is the most rapid way of accurately assessing fetal well being. With rapidly changing haemodynamic events in severely injured women, the question of how long should monitoring occur or how often it should be repeated must be carefully assessed. In the 72 hours after trauma, the acceptable minimum is monitoring for one hour every 8 hours. The use of cardiotocography in observing uterine activity is useful.

Diagnostic Ultrasound A simple ultrasound examination with a small portable machine will be able to confirm fetal cardiac activity when there is clinical doubt about the presence of a fetal heart beat. It can also be used to assess liquor volume. More detailed examinations requiring movement of the patient may be useful in diagnosing subplacental or broad ligament haematoma and fluid in the pouch of Douglas. More sophisticated studies which are usually only available in specialized perinatal units may be of great use in monitoring patients whose trauma has caused occult placental haemorrhage. Flow studies in the umbilical artery and peak systolic velocity in the fetal middle cerebral artery flow may give accurate knowledge of fetal anaemia s a result of haemorrhage. Key points •

A simple ultrasound examination with a small portable machine will be able to confirm fetal cardiac activity when there is clinical doubt

Kleihauer-Betke Count Alkaline elution of haemoglobin F and the ratio of stained (fetal) red cells to unstained (maternal) red cells in a peripheral maternal blood smear is the basis of this simple test. This test of fetal haemorrhage into the maternal circulation and an estimate of its extent is a good alert mechanism. Once it has been established by this test that significant fetal haemorrhage has occurred, it is pointless repeating it. The test has significant problems of sensitivity. Close observation of fetal welfare by other mechanisms is preferable to repeating the test. If the test is negative, the fetus must still be carefully observed. Haemorrhage of the fetus into the mother’s circulation is common. Rhesus negative women with a positive Kleihauer count have a special significance and require anti D gamma globulin administration. Maternal serum bicarbonate The data of Scorpio et al. (1992) have shown that maternal serum bicarbonate level correlates well with fetal loss and is more accurate than blood pH or pCO2 as an indicator of poor maternal tissue perfusion. A 30% reduction in fetal blood flow can occur before changes in pulse or blood pressure are present (Griess 1966). Serum bicarbonate levels will then give the earliest indicator of poor tissue perfusion. It should be performed on all pregnant accident victims as soon as possible and repeated especially in category 1 & 2 patients (Table 33.1). Key points •

Maternal serum bicarbonate level correlates well with fetal loss and is more accurate than blood pH or pCO2 as an indicator of poor maternal tissue perfusion

The treatment of uterine contractions Tocolysis in traumatized pregnant women is controversial. Pearlman et al. (Pearlman et al. 1990) found

uterine activity common in these situations but contractions ceased in 90% of women with “frequent uterine contractions”. Two factors must be kept in mind. Firstly, premature birth and abortion can occur following trauma. Secondly, the uterine activity may result from occult placental abruption, which may be augmented by tocolysis. Summary The injured pregnant woman presents diagnostic challenges because of the physiological changes of pregnancy which may both mask and mimic signs of shock. Meticulous care of the mother prevents fetal death and prolonged fetal observation is necessary to diagnose and accurately manage fetal hypoxia. One injured patient can be difficult; managing the mother and fetus can be extremely challenging.