Neonatal therapeutics

Question 1

How is pharmacology different in the neonate to that in the adult horse?

Answer 1

• Dynamic dosage
  
  • Neonates typically gain 1kg/day
• Increased oral bioavailability
• Volume of distribution
  
  • ↑ % body water
• Decreased plasma proteins
  
  • Less bound drug and more free
    
    • ↑ free (active) fraction of some drugs e.g. NSAIDs
• ↓ Metabolic and excretory capacity
  
  • Additional maturation of hepatic and renal function in 1-2 weeks postpartum

Question 2

What is the leading cause of detah in foals in the first week of life?

Answer 2

Sepsis

Question 3

How is sepsis treated in neonates?

Answer 3

• Antimicrobial therapy
  
  • Blood Culture
• Hemodynamic support (IVFT)
• Supportive care
• Early identification and treatment can be life saving!

Question 4

What type of antimicrobials should you use to treat sepsis in foals?

Answer 4

Bactericidal
* Septic foals are often neutropenic
* Immune system less robust compared to adults

Intravenous
* May have reduced gastrointestinal and muscle perfusion

Broad-Spectrum
* Both G+ve and G-ve are commonly found in foal sepsis
* Mixed infections are also common

Question 5

What are the recommended initial antibiotics when the risk of sepsis is low, moderate, high and septic?

Answer 5

Low & moderate
- Oral Trimethoprim sulphadiazine (TMPS) 30mg/kg PO q12h

High and septic
- Normal renal function:
- IV Sodium penicillin 22mg/kg q 6h + IV Gentamicin 12mg/kg q 36h (Or Amikacin 25mg/kg IV q24h)

• Abnormal renal function:
  
  • IV ceftiofur 5mg/kg q 12h

Await culture results
* Continue based on sensitivity patterns
* If negative, reasonable to continue with TMPS

Question 6

What are the first line antibiotics in adult horses? Why are they inadequate for foals?

Answer 6

IM procaine penicillin + IV Gentamicin
Foals
* Small muscle mass
* Perfusion?
* Procaine reaction

IV Oxytetracycline or PO doxycycline in some cases
Foals
* Higher doses -> kidneys
* Tendon laxity!
* Bacteriostatic

Question 7

What drugs can you use to sedate the neonate <4 weeks?

Answer 7

• Avoid Alpha2 agonists
  
  • Bradycardic effects
• Benzodiazepines
  
  • Diazepam 0.1-0.4mg/kg IV
  • • butorphanol 0.01-0.05mg/kg IV for added sedation and analgesia
• Butorphanol alone 0.01-0.05mg/kg IV
• Foal squeeze

Question 8

Why should you think twice before using NSAIDs in the neonate <4weeks? Which ones could be used?

Answer 8

• Side effects increased in comparison to adults
  
  • GI – Gastric and/or duodenal ulceration
  • Renal
• Short term analgesia?
  
  • Consider butorphanol IV or IM
• Use with care

What to use:
* Flunixin Meglumine 1.1mg-kg q12-24h
* Meloxicam 0.6mg/kg q12-24h
* Phenylbutazone? 2.2mg/kg q12-24h

Question 9

What mucosal protectant is safe to use in foals?

Answer 9

Sucralfate (10-20mg/kg q 6-8h)

Question 10

What is the only acceptable reason to give omeprazole in foals?

Answer 10

high risk of gastroduodenal ulceration or confirmed

Question 11

How would you manage dehydration/hypovolaemia/hypoperfusion in the field?

Answer 11

• 20mL/kg crystalloid IV (hartmanns) Average 50kg foal ->1L
• Reassess
• Repeat up to 3 times if needed based on reassessments

Question 12

How would you manage failure of passive transfer in the foal?

Answer 12

• Plasma 20mL/kg (Average 50kg foal -> 1L)
• +/- further 20-40mL/kg depending on IgG post transfusion
• Start very slow, monitor for transfusion reactions
• Use a blood product infusion set

Question 13

What should you give a 50 kg foal that needs a helping hand?

Answer 13

• Colostrum 250-500mL via NGT
• 1L Hartmanns IV
• 1L Plasma IV
• Enema