Cardiovascular function and fluid compartments in newborn canine hemorrhagic shock

Area of Science:

• Neonatal Physiology
• Hemorrhagic Shock Research
• Cardiovascular Medicine

Background:

• Adult hemorrhage effects are known, but neonatal responses are understudied.
• Neonates exhibit distinct fluid and electrolyte distributions compared to adults.

Purpose of the Study:

• To investigate the impact of hemorrhage on cardiovascular function, blood volume, and fluid balance in newborn dogs.
• To compare the effects of hemorrhage between very young (neonatal) and slightly older (post-neonatal) puppies.

Main Methods:

• Studied two groups of dogs: 1-20 days old (Group 1) and 3-6 weeks old (Group 2).
• Induced a 40% hemorrhage and measured extracellular fluid (ECF) volume, plasma volume (PV), and red blood cell mass (RBCM).
• Assessed cardiovascular parameters like cardiac output and coronary blood flow in older puppies.

Main Results:

• Younger puppies had significantly higher ECF volume and experienced less ECF reduction during hemorrhage.
• Plasma volume and RBCM decreased similarly in both groups; they recovered after reinfusion, but a functional ECF deficit persisted.
• Both groups showed similar bradycardia, myocardial depression, and acidosis. Cardiac output and coronary blood flow significantly decreased in older puppies during shock and remained low post-reinfusion.

Conclusions:

• Neonatal hemorrhage leads to a persistent deficit in functional extracellular fluid volume.
• Inadequate myocardial perfusion and ongoing acidosis impair cardiac function in neonatal shock, even after fluid resuscitation.