Editing Trauma - circulation (section)

==== '''Pregnancy''' ====

** Normal hypervolaemia in pregnancy - blood volume peaks at 34 weeks - 30-50% higher than normal. There is physiological anaemia of pregnancy (normally haematocrit 31-35%). Healthy patients will lose 1.2-1.5L of blood before showing signs of hypovolaemia.
** WBC higher in pregnancy
** Levels of serum fibrinogen and other clotting factors mildly elevated, but bleeding and clotting times are unchanged
** Cardiac output is 30-40% higher normally, but significantly decreased in supine position due to reduced preload from IVC compression
** Higher baseline HR - 10-15bpm higher
** Lower baseline BP by 10-15mmHg in second trimester
** Tidal volume increases and hypocapnia is common - PaCO2 is normally 27-32, and PaCO2 of 35-40mmHg may indicate impending respiratory failure
** Elevated diaphragm
** Takes greater blood loss to manifest abnormalities. Can = poor perfusion to fetus
** Placental vasculature is very sensitive to catecholamine stimulation - reduced fetal oxygenation despite normal maternal vital signs
** Placental abruption - can occur in the absence of any significant maternal injury
** Changes to primary survey
*** Manually displace uterus to the left side, or log roll to the left
*** Aim to maintain physiological hypervolaemia of pregnancy with early infusion/transfusion
*** Avoid vasopressors - fetal hypoxia
*** Continuous fetal monitoring after 20 weeks
** Secondary survey
*** Speculum exam to exclude spontaneous ROM, PV bleeding
*** Fetal assessment - fundal height, contractions/irritability, US/CTG
** Adjuncts
*** CT has the same indications - CT A/P is about 25mGy, and fetal radiation doses less than 50mGy are not associated with any known fetal anomalies or higher risk for fetal loss. However, exposure to 50mGy ionising radiation increases childhood cancer risk - risk of NOT having cancer goes from 99.8% to 99.5%.
*** All Rh-negative trauma patients should receive Rh immunoglobulin unless the injury is remote from the uterus, within 72 hours