Time Variable Models of Severe Hemorrhagic Shock in Rats.

Area of Science:

• Trauma Resuscitation
• Hemorrhagic Shock Management
• Pre-hospital Interventions

Background:

• Classical teaching emphasizes the 'golden hour' for damage control resuscitation after trauma.
• Trauma heterogeneity necessitates varied models for guiding research and treatment.
• The impact of hemorrhage timing and oxygen therapy on survival requires further investigation.

Purpose of the Study:

• To investigate the effects of varying hemorrhage and "down-times" on survival in a rodent model.
• To assess the influence of oxygen therapy (FiO2 21% vs. 40%) during simulated trauma.
• To challenge the rigid adherence to the "golden hour" concept in trauma care.

Main Methods:

• Rats underwent 40% blood volume hemorrhage over 30 or 60 minutes, followed by 30-60 minute "down-times".
• Fraction of inspired oxygen (FiO2) was administered at 21% or 40% to mimic nasal cannula oxygen.
• Outcomes including end-organ insult (lactate), cardiac function, blood pressure, and survival were analyzed using multiple linear regression.

Main Results:

• No statistically significant differences were observed in end-organ insult (lactate) across groups.
• Cardiac functioning (cardiac output, left ventricle fractional area of change) showed no significant variation.
• Mean arterial pressure, survival rates, and survival times did not differ significantly among experimental groups.

Conclusions:

• The study provides evidence against a strict, all-encompassing "golden hour" for trauma resuscitation.
• Rapid hemorrhage with extended "down-time" did not negatively impact survival in this rodent model.
• Cardiac markers of injury were examined using transthoracic echocardiography, adding to the existing literature.