Clinical and laboratory predictors of blood loss in young swine: a model for pediatric hemorrhage

Background: The pediatric patient’s response to hemorrhage as a function of young age is not well understood. As a result, there is no consensus on optimal resuscitation strategies for hemorrhagic shock in pediatric patients, or on the identification of clinical triggers to prompt implementation. The study objective was to develop a model of pediatric hemorrhage using young pigs to simulate school-aged children, and determine clinical and laboratory indicators for significant hemorrhage. Materials and methods: 29 non-splenectomized female pigs, aged 3 months, weighing 30–40 kg, were randomized into groups with varying degrees of hemorrhage. Bleeding occurred intermittently over 5 h while the animals were anesthetized but spontaneously breathing. Various physiologic and biochemical markers were used to monitor the piglets during hemorrhage. Results: Swine experiencing up to 50% hemorrhage survived without exception throughout the course of hemorrhage. 80% (4/5) of the animals in the 60% hemorrhage group survived. Need for respiratory support was universal when blood loss reached 50% of estimated blood volume. Blood pressure was not useful in classifying the degree of shock. Heart rate was helpful in differentiating between the extremes of blood loss examined. Arterial pCO_2, pH, lactate, HCO₃ and creatinine levels, as well as urine output, changed significantly with increasing blood loss. Conclusions: Young swine are resilient against hemorrhage, although hemorrhage of 50% or greater universally require respiratory support. In this animal model, with the exception of heart rate, vital signs were minimally helpful in identification of shock. However, change in select laboratory values from baseline was significant with increasing blood loss. Level of evidence: This was a level II prospective comparative study.