Trauma in pregnancy - Clinical Tree

Essentials

1
Trauma in pregnancy is the most common cause of non-obstetric maternal death, with most deaths due to head injury and haemorrhagic shock.
2
Fetal death occurs more often than maternal death and is dependent on the severity of the maternal injuries. Placental abruption and direct fetal trauma cause most fetal deaths.
3
Common causes of trauma are motor vehicle collisions, falls and assaults.
4
Important sequelae are bruising, fractures, premature labour, placental abruption, disseminated intravascular coagulopathy, feto-maternal haemorrhage, intra-abdominal injuries, uterine rupture and haemorrhagic shock.
5
The physiological changes that occur with pregnancy, such as the relative hypervolaemia and the gravid uterus, can make clinical assessment of the patient difficult.
6
Continuous cardio-tocographic monitoring for at least 4 hours is the best predictor of placental abruption and fetal distress.
7
Bedside ultrasound allows the early detection of intraperitoneal fluid and evaluation of the fetal heart.
8
Maternal resuscitation remains the best method of fetal resuscitation.

Introduction

Trauma during pregnancy presents a unique set of challenges for the emergency department (ED), as the anatomical and physiological changes that occur during pregnancy will influence the evaluation and management of the patient. An appreciation of these changes is important. Aggressive resuscitation of the mother remains the best treatment for the fetus. A multidisciplinary approach with early obstetric consultation will help to improve the outcomes of these patients.

Anatomical and physiological changes in pregnancy

Cardiovascular

Blood volume increases by about 50% by the end of the third trimester. With relative hypervolaemia, the patient may lose up to 35% of her blood volume before signs of haemorrhagic shock appear. Maternal cardiac output increases by 30% to 50% by the end of the second trimester. The resting heart rate increases by 15 to 20 beats/min by the end of the third trimester. Systolic and diastolic blood pressures fall by 10 to 15 mmHg during the second trimester but rise again towards the end of the pregnancy. Electrocardiographic (ECG) changes may occur with cephalic displacement of the heart, such as left axis deviation by 15 degrees, T-wave inversion or flattening in leads III, V1 and V2 and Q waves in III and AVF. After 20 weeks’ gestation, supine positioning may cause inferior vena cava (IVC) obstruction by the gravid uterus, leading to a fall in cardiac output.

Haematological

Blood volume expands by about 1500 mL during pregnancy, of which 1000 mL is plasma volume and 500 mL is erythrocytes. This results in a dilutional anaemia with a fall in haematocrit (31% to 35% by the end of pregnancy). Pregnancy induces a leucocytosis, with levels up to 18,000/mm ³ in the third trimester. Coagulation factors increase (fibrinogen, factors VII, VIII, IX, X), increasing the risk of venous thrombosis. The buffering capacity of the blood is reduced.

Respiratory

There is increased airway oedema. The diaphragm is elevated by about 4 cm. Increased levels of progesterone stimulate the medullary respiratory centre. Tidal volume and minute volume increase by 40%. A respiratory alkalosis results, with a fall in PCO ₂ to 30 mmHg. The anteroposterior diameter of the chest is increased and the mediastinum is widened on chest x-ray.

Gastrointestinal

Cephalic displacement of intra-abdominal structures reduces gastro-oesophageal sphincter tone; combined with delayed gastric motility, there is an increased the risk of aspiration. The intestines are displaced to the upper part of the abdomen and may be shielded by the uterus. The spleen becomes engorged and is more susceptible to injury. The peritoneum is stretched by the gravid uterus, which may make signs of peritonism less reliable. Alkaline phosphatase levels may triple because of placental production.

Urinary

Dilatation of the renal pelvis and ureters occurs from the 10th week of gestation. The bladder becomes hyperaemic and is displaced into the abdomen from the 12th week, making it more susceptible to trauma.

Uterine

There is a massive increase in uterine size. Blood flow to the uterus increases from 60 to 600 mL/min by the end of the pregnancy.

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