The Pregnant Trauma Patient
Trauma in pregancy is a specialst area. Particularly important differences from normal ATLS practice include the need for early O&G involvement, the consideration of the uterus as a potential source of lifethreatening haemorrhage, and the need to give Rh immunoglobulin to Rh–negative mothers within 72 hours.
Pregnancy and trauma seem to be a favourite topic of CICM examiners. It has appeared several times in the SAQs. Typically, the question is waffly and non-specific, asking you to describe your general approach, or what the "management issues" are.
Existing examples include the following:
- Question 17 from the first paper of 2015 ("management issues")
- Question 16 from the second paper of 2012 ("management issues")
- Question 3 from the first paper of 2007 ("special considerations")
- Question 1a from the second paper of 2003 (initial management)
- Question 1b from the second paper of 2003 (timing and nature of investigations)
Unique aspects of trauma in pregnancy:
Basic principles of ATLS still apply
- Whats good for the fetus is whats good for the mother. Resuscitate the mother.
- Lifesaving xrays should not be delayed by thinking about fetal radiation injury.
- The airway is more difficult to control.
- There is an increased risk of aspiration due to decreased gastric emptying and weakened lower oesophageal sphincter.
Ventilation and respiratory assessment
- The respiratory function is impaired by decreased FRC;
- One needs to insert their chest drains higher, so as to avoid the pushed-up diaphragms
- When setting up the ventilator, one needs to keep in mind that the PaCO2 is supposed to be 30mmHg in late pregnancy.
Management of circulation and maternal haemorrhagic shock
- Pregnancy-associated volume expansion causes the signs of shock to develop late, after massive blood loss
- Vena cava compression means the patient needs to be positioned at a 30° tilt
- Placental abruption may result in massive haemorrhage and needs to be excluded early in the primary survey
- Retroperitoneal haemorrhage from dilated pelvic veins needs to be excluded.
- Pelvic injuries (particularly pelvic rim fractures) may threaten the head of the foetus.
- For obvious reasons, a pelvic binder is not a good idea.
- Most common cause of fetal death is maternal shock. A shocked maternal circulation is really quite useless. This will be picked up during the routine ABCs.
- Foetal monitoring needs to be considered at 24 weeks or older; prior to that there is no point (as the foetus is pre-viable).
- Cardiotocography (CTG) is the appropriate monitoring modality
Concerns regarding foetal radiation exposure
- The primary sources of human data for this are studies of the 1945 atomic bomb survivors from Hiroshima and Nagasaki, a group that included approximately 2800 pregnant women (McCollough et al, 2007)
- Of these women, 500 received a foetal dose of more than 10 mGy (0.01Gy)
- Their problems included intrauterine growth restriction, small head size, reduced intelligence, organ malformation, and childhood cancer.
- This, clearly, is not a good representative group when generalising data to the modern pregnant trauma patient.
- The closest in terms of Hiroshima-level exposure is a multi-slice trauma series CT, which might approach a foetal dose of around 32mGy (Felmlee et al, 1990). That's using old scanners, mind you, taking multiple slices directly through the foetus.
- Unless you're imaging the uterus directly, the foetus is exposed only to scatter radiation, and the dose is negligible. In scans which stop more than 30cm from the foetus, the scatter radiation dose is very low (0.001 mGy) and the risk to the foetus is minimal.
Unique anatomic issues in pregnant trauma
Specific patterns of injury in the pregnant patient
- More common:
- liver injury
- spleen injury
- retroperitoneal hemorrhage
- uterine injury
- Less common
- bowel injury
Abdominal injury in pregnancy
- Blunt injury may cause fetal injury (1%) and premature labour
- Lap belts cause more uterine injury than shoulder belts if the lap belt is incorrectly placed across the uterus rather than the thighs.
- Penetrating trauma to the uterus is usually fatal to the foetus, and benign to the mother because the uterus protects the other organs
- The uterus is intrapelvic until week 12, then it rises into the abdomen.
- by week 20, its reached the umbilicus
- at week 34, it reaches the costal margins
- The bowel gets pushed into the upper abdomen – thus, more protected
- The pituitary gland swells up - this may lead to pituitary infarction with head injuries
Foetal cushioning and uterine integrity
- FIRST TRIMESTER: uterus is thick walled and small
- SECOND TRIMESTER: uterus is larger, but the fetus is cushioned with lots of amniotic fluid
- THIRD TRIMESTER: uterus is huge and thin-walled, there is less amniotic fluid
- Fetal head is usually protected by the pelvic rim
- Of curse, if the rim fractures, the foetal head is at risk
Potential for uterine haemorrhage and rupture
- Placenta receives 20% of maternal blood flow in late pregnancy
- The placenta is not elastic – shear forces can cause abruptio placentae
- The placental vessels are exquisitely sensitive to vasoconstrictors. The catecholamine excess of haemorrhagic shock tends to rob the foetal circulation.-
- 80% of pregnant women who survive hemorrhagic shock will lose the baby.
- Occasionally, the uterus will rupture with trauma.
- It then becomes impossible to palpate the fundus.
- One can occasionally palpate exposed fetal bodyparts through the abdominal wall.
- The second most common cause of fetal death is abruptio placentae. Late in pregnancy this can happen with relatively minor trauma.
- How do you know it is happening?
- Vaginal bleeding occurs in 70% of cases. A vaginal examination is mandatory.
- Uterine tenderness may be present
- Frequent uterine contractions are complained about
- "Uterine tetany" may occur
- Uterine irritability (contracts when touched)
Emergency and perimortem caesarian section in trauma
- Perimortem caesarian in cardiac arrest is explored more extensively elsewhere. Particularly, it was the topic of Question 9 from the first paper of 2016. The topic of perimortem caesarian in trauma is somewhat different.
- The rationale for traumatic perimortem caesarian is to improve the adequacy of venous return, thereby improving the chances of maternal recovery. In haemorrhagic shock, insufficiency of venous return is the main physiological reason underlying PEA arrest.
- The practice is recommended for pregnancies later than the 23rd week (fundal height more than 2 finger breadths above the umbilicus), because:
- A foetus beyond the 23rd week has a chance of extrauterine survival
- A gravid uterus beyond the 23rd week is large enough to cause aortocaval compression
- The foetus is unlikely to survive if the mother has arrested due to exsanguination. The uterus is very sensitive to vasoconstricting catecholamines, which pour liberally into the circulation of the haemorrhaging mother. By the time the mother has died of haemorrhagic shock, the foetus is long been in a state of desperate hypoxia; nobody will be satisfied with this outcome. There were at one stage calls to abandon this practice.
- However, even an old study (Morris, 1996) reports satisfactory outcomes for both mothers and infants in non-arrest trauma setting. Of the 32 patients retrospectively studied, 75% of the infants survived. Of the infants who died, 60% died as a result of delayed recognition of their distress, i.e. of preventable causes.
- Are there any society guidelines? Jain et al (2015) present us with a recommendation in favour of perimortem caesarian, provided it happens within 4 minutes of arrest. This is a Grade III-b recommendation, based on "opinions of respected authorities".
Unique features of secondary survey in pregnancy
- If you do a DPL, make the incision ABOVE the umbilicus.
- of course, who does DPLs these days?...
- Look for amniotic fluid in the vagina – test it, the pH will be 7 to 7.5
- Look for the characteristic DIC of amniotic fluid embolism
- Give Rh immunoglobulin to Rh–negative mothers within 48-72 hrs