Similarities and differences between maternal and major traumatic haemorrhage – what can we learn?

We read the correspondence from Margiotta and Plaat with interest [1]. There could be much gained by comparing major obstetric and traumatic haemorrhage. Three areas that we believe are particularly relevant are identification of hypovolaemia and coagulopathy, and the impact of human factors.

The 7th National Audit Project (NAP7) authors identified that hypovolaemia was under-recognised and inadequately treated in obstetric patients who had a cardiac arrest [2]. Trauma research suggests multimodal assessments of volume status are important, as individual parameters and scoring systems lack sensitivity and specificity. In addition to heart rate and blood pressure, capillary refill, pulse pressure, base deficit and lactate, coagulopathy and estimated blood loss may be most useful and should be used in combination. Shock index can be a predictor of the severity of shock in trauma, but not in the obstetric population.

The NAP7 authors recommended the use of fluid resuscitation and vasopressor use in obstetric haemorrhage [2]. In the major trauma setting, acidaemia, hypothermia, hyperkalaemia, hypocalcaemia and coagulopathy are associated with worse outcomes. Consequently, early transfusion of blood products and management of metabolic disturbance are of the upmost importance. Viscoelastic haemostatic assay-driven therapy represents the ‘gold standard’ in trauma care and is recommended by international guidelines [3]. The importance of targeted therapy was emphasised by CRYOSTAT-2, showing no advantage to empirical cryoprecipitate use in major trauma and worse outcomes if given before depletion of fibrinogen [4]. Pregnancy is accompanied by significant changes in the coagulation and fibrinolytic systems including increased fibrinogen concentrations (3.5–6.5 g.l^-1) [5]. Hypofibrinogenaemia is associated with poor outcomes and, as a result, a higher fibrinogen target of 2 g.l^-1 is recommended.

We must also consider fetal wellbeing. To preserve uterine blood flow, maternal systemic blood pressure should be maintained near normal before delivery. As such, hypotensive resuscitation, which can be an advantageous approach in damage control resuscitation in trauma [3], is not the mainstay in obstetrics.

Multidisciplinary teamwork, effective communication and human factors are key in managing both obstetric and traumatic major haemorrhage, with failure of these recognised as a contributor to maternal morbidity and mortality by MBRRACE-UK [6]. Non-technical skills including situational awareness, appropriate role allocation and performance under pressure in stressful situations are important.

Comparing obstetric and traumatic haemorrhage highlights that not all bleeding is the same, as they differ significantly in physiological response and risk of coagulopathy. These differences are influenced by a patient's underlying physiological state and the specific cause of the bleeding. By understanding these similarities and distinctions between the two types of haemorrhage, we can potentially enhance patient outcomes.