Blast polytrauma with hemodynamic shock, hypothermia, hypoventilation and systemic inflammatory response: description of a new porcine model

Abstract

Purpose: In the past decade blast injuries have become more prevalent. Blast trauma may cause extensive injuries requiring improved early resuscitation and prevention of haemorrhage. Randomized prospective trials are logistically and ethically challenging, and large animal models are important for further research efforts. Few severe blast trauma models have been described, which is why we aimed to establish a comprehensive polytrauma model in accordance with the criteria of the Berlin definition of polytrauma and with a survival time of > 2 h. Multiple blast injuries to the groin and abdomen were combined with hypoperfusion, respiratory and metabolic acidosis, hypoventilation, hypothermia and inflammatory response. The model was compared to lung contusion and haemorrhage.

Methods: 16 landrace swine (mean weight 60.5 kg) were randomized to "control" (n = 5), "chest trauma/hem" by lung contusion and class II haemorrhage (n = 5), and "blast polytrauma" caused by multiple blast injuries to the groin and abdomen, class II haemorrhage, lipopolysaccharide (LPS) infusion and hypothermia 32 °C (n = 6).

Results: The blast polytrauma group had an Injury Severity Score of 57 which resulted in haemodynamic shock, hypothermia, respiratory and metabolic acidosis and inflammatory response. The chest trauma/hem group had an Injury Severity Score of 9 and less profound physiologic effects. Physiologic parameters presented a dose-response relationship corresponding to the trauma levels.

Conclusion: A comprehensive blast polytrauma model fulfilling the Berlin polytrauma criteria, with a high trauma load and a survival time of > 2 h was established. A severe, but consistent, injury profile was accomplished enabling the addition of experimental interventions in future studies, particularly of immediate resuscitation efforts including whole blood administration, trauma packing and haemostasis.

Keywords: Blast injury; Haemorrhage; Polytrauma; Porcine model.

Fig. 1

Chart of experimental setup and groups

Fig. 2

Photos of a ultrasound image of the lung with subcutaneous tissue (#), pleura (¤) and unaffected lung (§). b Ultrasound image of the lung with pleura (¤) and b-lines (*) disclosing intrapulmonary fluids. c Macro-histopathology specimens of the lung showing lung contusion. d Picture of thoracic skin lesion caused by impact of the projectile e detonator with 1 g of penthyl plastic explosive attached by tape. f Detonated explosive charge. g Placement of explosive charge above the femur, marked with a green cross. h Placement of explosive charge on the right abdomen above the liver, marked with a green cross. Size markers equal 5 cm

Fig. 3

Circulatory and systemic effects. The polytrauma resulted in circulatory instability and hypothermia. a Mean artery pressure, MAP, b cardiac output, CO, c haemoglobin, d pulmonary artery wedge pressure, PAWP, e mean pulmonary artery pressure, MPAP, f temperature, g haemorrhage. h Troponin T, i myoglobin. *p < 0.05, **p < 0.01, ***p < 0.005

Fig. 4

Respiratory effects. The polytrauma caused a severe hypercapnia and a transient hypoxia. a PaO₂, b PaCO₂, c SvO₂, d tidal volume, e respiratory rate, f alveolar minute ventilation. *p < 0.05, **p < 0.01, ****p < 0.001

Fig. 5

Metabolic effects. The polytrauma caused a combined severe respiratory and metabolic acidosis, hyponatremia and hyperglycaemia. a pH, b base excess, c lactate, d Na⁺, e K⁺, f glucose. *p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.001