Smith.16.17Manifestations And Management Of Neonantal Foals Flashcards
Fluid bolus rate and over what amount of time
20 ml/kg over 15 to 20 minutes
Max of number of fluid boluses to repeat within a short period of time?
80 ml/kg
**4L for a 50 kg foal
Essential laboratory data that can be collected during fluid resuscitation
Packed cell volume
Total plasma protein
Blood glucose
Blood gas (electrolyte & lactate)
Benefits of plasma
Improvement in osmotic pressure
Coaguation factors
Provides buffer base
Immunotherapy
Rate of plasma administration
10 ml/kg per hour
Dose of hetastarch for rapid fluid resuscitation in foals
3 ml/kg at rate of 10 ml/kg/hour
Foal that is moderately to severely sunken eyes is estimated to what percent dehdyration?
8 to 10%
When is inopressor therapy indicated?
If hypotension persists in the face of fluid resuscitation
**aim of therapy to raise MAP above 60 mmhg
Examples of inopressor drugs
Dobutamine
Dopamine
Norepinephrine
Vasopressin
Dobutamine
Positive inotrope that improves cardiac output by improving stroke volume
Dose: CRI at 3-20 microg/kg/min
** not common to admin a vasopressor with dobutamin to improve tissue perfusion
Norepinephrine mechanism of action
Alpha 1 & 2 receptors to mediate vasoconstriction
Beta1 adrenergic receptors causing pos inotropic & cardiotorpic effects
Norepinephrine dosing
CRI 0.05 to 5.0 microg/kg/min
Dopamine mechanism of action
Alpha & beta adrenergic effects
— moderate to strong affinity for dopamine receptors (DA-1 & DA-2) and
— activity at dopaminergic recetors mediate vasodilation (renal, cerebral & splanchnic vasculr beds)
Dopamine dose
Lower rate improve renal/spanchnic perfusion: 0.5- 5 microg/kg/min
Higher infusion rate with severe septic shock: 10 - 25 microg/kg/min
Vasopressin mechanism of action
V1a receptors: in peripheral circulation causes vasoconstriction
V2 receptors: in kidney to facilitate water reposition
Vasopressin dose
0.25 to 1.0 mU/kg/min
Combination of vasporessin (low dose) and norepinephrine beneficial effects
Increase in MAP
Reduction in heart rate
Increased urine output
Why should boluses of glucose solutions be avoided?
Result in urinary losses of fluid, electrolytes & glucose
Can produce rebound hypoglycemia
Equation for replacement potassium supplementation
Replacement K (mEq)= 0.4 x body weight (kg) X K deficit (mEq)
Potassium can safely be added to fluids at what rate?
10 to 40 mEq/L
Potassium supplementation should not exceed what rate?
0.5 mEq/kg/hour
When is potassium supplementation in IV fluids usually indicated?
Critically sick neonates
Anorexic foals
Foals with diarrhea
Those receiving diuretic therapy
What is a situation when supplementation for sodium bicarbonate for an acidotic foal is not rewarding?
When acidosis is due to poor perfusion
Equation for bicarbonate deficit
Bicarb deficit (mEq)= 0.6 x body weight (kg) x base deficit (mEq)
How to make isotonic bicarbonate solution?
150 ml 8.4% bicarb solution to 850 ml sterile water
Plasma transfusion dose for failure of passive transfer
20 ml/kg
1 liter of plasma (with IgG>1200 mg/dL) raises serum IgG by
200 to 250 mg/dL (2 to 2.5 g/L)
Will the 20 ml/kg dose in septic foals attain a serum IgG concentration over 800 mg/dL?
Sometimes
Ill foals require more plasma b/c serum half-life of IgG is less and IgG may be sequestered in intravascular spaces or at sites of inflammation or be catabolized more readily
Recumbency in foal increases the risk for:
Pneumonia
Predisposes to ileus & constipation
INc risk of milk aspiration
Exacerbates musculoskeletal weakness
Risk of decubital ulcers
Foals are more vulnerable to water loss than adults because
Inc basal metabolic rate
Greater surface area
Reduced urine concentrating ability
Normal caloric intake in foals
125 to 150 kcal/kg/day
20-30% of bwt in milk daily
Resting energy requirement (RER) in ill foals
50 kcal/kg/day
Benefits of enteral feeding a foal?
Stimulates normal gut maturation
Growth of intestinal villi
Production of crypt cells
Hepatic & biliary secretions
Brush border disaccharidase enzyme activity
Alternative species milk used for supplementing foals?
Goats milk— higher in fat, total solids & gross energy than mare smilk
Cows milk— 2% skim with 20 g of dextrose per liter of milk
Ideal foal milk replacer
22% crude protein
15% fat
Less than 0.5% fiber on a dry matter basis
Can calf milk replacer be used to feed a foal?
If mixed with mares milk
Commonly used parenteral nutrition solution mixtures in foals
50% dextrose
8.5% or 10% amino acids
20% lipid emulsion
Simplified formula for 50 kg foal for parenteral nutrition
2.5 L of 8.5% amino acids
1 L of 20% lipid
1.5 L of 50% dextrose
**mixed into empty 5 liter fluid bag
Foals should not receive over what percentage of calories from lipid?
Not over 50% of nonprotein calories from lipid
Disorders in foals that cause weakness/somnolence since birth
In utero acquired bacterial/viral infections
Birth asphyxia & trauma
Chronic placental problems
Congenital anomalies
Disorders of foals that display weakness/somnolence that have physical immaturity (ie tendon laxity)
Fatigue
Hypothermia
Hypoxia
Hypoglycemia
Disorders of weakness in foals (w/o somnolence)
Trauma
Pierpheral nerve or mucsle damage
Neuromuscular diseases that cause weakness without somnolence include:
Botulism
Nutritional myodegeneration (NMD, white muscle disease)
Congenital myotpahties
Botulism in foals is acquired via
GI tract
Wounds
Umbilicus
NMD associated with with selenium and/or vit E deficiency: 2 forms
- First year of life in rapidly growing large animals
- In utero form
Clinical signs associated with NMD include:
Localized signs (dysphagia)
Generalized paresis
Rhabdomyolysis precipitated by stress or periparturient hypoxia
Phenylbutazone given to a mare prior to foaling, is present in the foal in what form?
Oxyphenbutazone (active metabolite of phenylbutazone)
Severe electrolyte and metabolic derangements in foals that manifest as weakness
Hypoglycemia
Acidosis
Hyponatremia
Hypernatremia
Hyperkalemia
Compression of the spinal cord leading to paraplegia or tetraplegia can be due to
Vertebral body malformation
Osteomyelitis
Fractures
Vertebral body malformation occur sporadically in foals and are usually due to
Genetic
Nutrition
Environment
Normal gestation length: horses
~340 days (335 to 342 days)
Foals premature
<320 days
Foals dysmature
> 330 days with signs of prematurity
Prolonged gestation
> 360 days
**post-mature if large, thin foals
Stages of parturition
- Development of coordinated uterine contractions
- Expulsion of foal
- Passing of fetal membranes
Stage 1 parturition characteristics
Fetus plays active role in positions from dorsopubic to dorsosacral
Increased uterine pressure causes cervical dilation
Signs of restlessness, mild colic and patchy sweating
Stage 2 parturition characteristics
Rupture of the chorioallantois
Strong abdominal contractions force expulsion of foal
Appearance of one hoof at vulva expected w/in 5 minutes of rupture of chorioallantois
**delivery w/in 20-30 minutes
Stage 3 parturition characteristics
Passing of fetal membranes (w/in 3 hoours)
Normal respiratory-cardiac rhythm should be established in foals, how long after birth?
1 minute of birth
Righting and suckle reflexs are apparent within
5 minutes of birth
Foals should be starting to stand within:
30 minutes
Normal foal consumption of milk
20-25% bodyweight
When should foals pass meconium
1 to 4 hours after birth
When should foals urinate by?
8-12 hours
Differentials for lesion localization: cerebral
Neonatal maladjustment syndrome
Meningitis
Trauma
Sepsis
Metabolic derangements: hypoglycemia/electrolyte abnorm
Atlantoaxialoccipital malformation
Adequate passive transfer of immunity in foals
> 800 mg/dL
Partial failure of transfer of immunity in foals
400-800
Complete failure of passive transfer in foals
<400 mg/dL
Sepsis definition
Systemic inflammatory response (SIRS) caused by any circulating microorganisms and/or their products
Most common etiologic agents of sepsis in foals
Gram neg most common:
E. Coli
Salmonella
Acitnobacillus equuli
Klebsiella spp
Enterobacter spp
Pseudomonas spp
Gram pos: enterococcus, Streptococcus, Stpahylococus spp
Fungal organisms: candida albicans
Pre-hepatic differentials for icterus in foals
Neonatal isoerythrolysis
Hemolytic anemia (sepsis)
Anorexia
Hepatic differentials for icterus in foal
Sepsis
Ascending umbilical vein infection
Tyzzers
Actinobacillus equuli
Leptospira interrogans
Equine herpesvirus-1
NI cases receiving multiple blood transfusions (>4L)
Post-hepatic differentials for icterus in foals
Cholestasis/biliary obstruction
Causes of anemia
Hemorrahge
Hemolysis
Decreased production
Immune-mediated destruction
Oxidative destruction
Tests to determine immune mediated anemia
Auto-agglutination
Spherocytes
Coombs test
RBC surface antibody
What are the most common offending antigens in NI foals?
Aa
Qa
Donkey factor (mules)
Prevalence of NI
TB: 1%
STB: 2%
Mules (donkey sire, horse dam): 10%
Preventative tests for neonatal isoerythrolysis
Screen mares blood type and presence of anti-RBC antibody
Compare to stallions blood type prior to parturition
Jaundice foal agglutination test
In foals with neonatal encephalopathy, CNS as well as organs with high oxygen deman and metabolic activity may be affected, which organs are these:
GIT
Kidney
Liver
Heart
What are key functions of astrocytes?
Glutamate and GABA uptake
Glutamine synthesis
Energy generation (lactate production via aerobic glycolysis)
Water balance
Which receptors are involved in excitotoxicity associated with neonatal encephalopathy?
**all members of glutamate receptor family
—> specifically NMDA receptors
Which energy pathways are important to astrocyte energy generation?
Aerobic glycolysis
Lactate production (Warburg effect)
What energy pathways are important for neurons?
Mitochondiral oxidative phsopohyrlation (tricarboxylic cycle)
Pentose cycle
**important to produce energy & maintain antioxidant (NADPH) capacity
How do astrocytes provide a steady source of energy for neurons?
Neurons use pyruvate and lactate released by astrocytes to feed tricarboxylic cycle and oxidative phosphorylation to generate ATP
Glutamate effect on astrocytes
Glutamate accumulation stimulates glucose uptake and lactate production by astrocytes
Which cells have enzymatic machinery to produce neurosteroids from cholesterol?
Nuerons
Glial cells (astrocytes & oligodendrocytes)
What is the main receptor/target for neuroactive steroids?
GABA receptor
Activation of Gaba receptor facilitates:
Chloride entry
Hyperpolarizes the cell membrane
Decreases neuronal cell excitability
Modifies flial cell function
What neurosteroids are responsible for the sedated response of fetus in utero?
Allopregnanolone
Pregnanolone
What is the main source of pregnenolone throughout gestation?
Equine fetal gonads
What are the chief contributors to progesterone in fetal circulation?
Fetal adrenal glands
The fetal gonads produce pregnenolone, what other hormone do they produce?
Androgens (DHEA) that are converted to estrogens by the fetoplacental unit
What hormone changes are associated with fetal maturation of HPAA maturation?
5-7 days prior to foaling enzymatic shift from progestogen to glucocorticoid synthesis
—> drop in progestogens with parallel increase in fetal corticotropin and cortisol concentrations
Fetal risk factors for development of NE
Congenital anomalies
Twins
Prematurity/dysmaturity
Sepsis
Umbilical cord compression
Dystocia
what are physical characteristics of immaturity
low birth weight
small body size
short and shiny hair coat
doming of the head
periarticular laxity
droopy ears
Define prematurity in a foal
foals with shortened gestational period and signs of physical immaturity
Define dysmaturity in a foal
foals that are physically immature int eh face of an appropriate gestational length