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Equine medicine > ANESTHESIA OF EQUINE RISK PATIENTS > Flashcards

ANESTHESIA OF EQUINE RISK PATIENTS Flashcards

1
Q

MOST COMMON TYPES OF RISK PATIENTS:

A
  1. Foals
  2. Geriatric horse
  3. Donkeys and mules
  4. Horses with intestinal emergencies (colic)
  5. Pregnant mare
  6. Anesthesia and hyperkalemic periodic paralysis
  7. Anesthesia and equine malignant hyperthermia
  8. Horse with RAO
  9. Horse with laryngeal hemiplegia
  10. Horse with cardiovascular problem
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2
Q

Why are anesthesia in foals difficult?

A
  • Pulmonary changes within the first few hours

- Circulatory changes by49 – 72 hours

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3
Q

what are the partial pressure for the aterial blood in foals?

A

PaO2 at birth - 40 mmhg
1h - 60 mmhg
4h - 75mmhg
7 days - adult - 90mmhg

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4
Q

What are the preoperative evalutions of a foal?

A
  • Auscultation on heart
  • Congenital cardiac defect
  • Heart murmur: foramen ovale / ductus arteriosus can reopen (hypoxemia or acidosis)
  • Colostrum intake!!! IgG < 800 mg/dl, give plasma transfusion/colloids
  • Blood glucose! (Hypo)
  • Substitute glucose
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5
Q

Fasting of foals before anesthesia:

A
  • Neonatal foal (4 – 6 weeks old) allowed to suck
  • If tube fed - withhold milk for a period (sick foals have delayed gastric emptying – negative during anesthesia.
  • Older foals (< 3 month): max. 4 – 6 fasting
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6
Q

How is the newborns thermoregulation?

A
  • CO HR dependent! – CAVE bradycardia
  • Small body mass, low body fat content, high surface –> significant heat loss
  • increased metabolic rate (6 – 8 ml/kg/min O2 consumption) –> hypoxemia, hypoglycemia earlier than in adult.
  • Pay attention to heat loss! Keep warm during anesthesia.
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7
Q

Effects of hypothermia (foals)

A
  • MAC decrease
  • Bradycardia – decreased CO
  • Tissue perfusion decrease, metabolism decrease, bleeding time increase
  • Delayed recovery, increased O2 consumption (shivering)
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8
Q

Which drugs are used for sedation of foals?

A

Diazepam, midazolam

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9
Q

What do we have to prevent when sedating a foal?

A

hypothermia, hypoglycemia!!

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10
Q

What is very important to provide during sedation of a foal?

A

Provide extra O2!!!

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11
Q

What is a good sedative in sick foals?

A

-Butorphanol: 0.05 – 0.2 mg/kg IV –> good sedation in sick foals (average dose)

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12
Q

What is the safest combo of drugs for neonates?

A

Benzodiazepines: diazepam/diazolam

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13
Q

When can we use alpga2 agonists in foals?

A

over 4 weeks, not so sick

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14
Q

Which alpha 2 agonists can we use in foals?

A
  • xylazine 0.3 mg/kg IV
  • detomidine 0.005 mg/kg IV
  • medetomidine 0.003 mg/kg IV
  • romifidine 0.03 mg/kg IV
  • Low doses to effect!
  • Avoid in the sick neonatal foal – cardiovascular SE
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15
Q

Why do we give lower doses of injectable drugs to foals?

A
  • Greater proportion of CO to the heart, brain
  • Immature CNS
  • increased sensitivity of receptors
  • Permeable BBB
  • decreased plasma protein binding (low lbumin)
  • higher total body water, EC fluid
  • Drug metabolism, long lasting drug effect!
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16
Q

Drug doses for older foals:

A
  • Higher doses of inhal an. than of neonates
  • Excitable nature
  • EC fluid volume > in adults
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17
Q

Induction with inhalational anesthetics : (foals)

A

-Not recommended!
-Easy to overdose, Isoflurane and sevoflurane.
-For neonates after minimal sedation
-Facemask/nasotracheal tube
-Rapid uptake of volatile anesthetics!!
-Lower therapeutic index than injectable agents
Mortality! Stress!! (rapid uptake + systemic disease)

18
Q

Induction with an.iv drugs: (foals)

A

Light plane anesthesia/short (eg. joint lavage):
-Ketamine 1 – 2 mg/kg, IV + diazepam 0.005 mg/kg IV
Deep plane an./long
-Ketamine 2 – 3 mg/kg IV + diazepam +/- alpha2 agonist
-Propofol 2 mg/kg IV (apnea, minimal analgesia)

19
Q

Maintenance of anesthesia (foals)

A
  • Inhalational anesthesia / TIVA / PIVA
  • PIVA (isoflurane, ketamine, lidocaine): good recovery
  • Less personal experience of the anesthesiologist, + very sick foal - mortality rate increase
20
Q

How do we monitore young foals?

A
  • Lower blood pressure (40 – 60 mmHg)
  • Bradycardia < 50 beats – neonates
  • RR increase, fast acting inhalational agents
  • Endotracheal intubation is more difficult-nasotracheal tube
  • PaCO2 < 50 – 60 mmHg, small volume rebreathing circle
  • Active heating
  • Check blood glucose (sick!!)
  • -> 2.5% dextrose inf. 3 – 5 ml/kg/h
  • At recovery to sternal recumbency ASAP
21
Q

Why is it difficult to do anesthesia on a geriatric horse?

A

> 20 years of age

  • Gradual loss of functional reserve:
  • Lower ABP
  • low ventricular filling and total body water
  • low metabolic, excretory capacity of liver, renal, heart function
22
Q

Which sedative do you use on a geriatric horse?

A

ACP 0.03 mg/kg, IM, Xylazine, butorphanol IV

23
Q

Which anesthesia do you use on a geriatric horse?

A

TIVA/PIVA/Inhalational an. – IPPV

24
Q

What are some age associated diseases?

A

RAO
Cushing syndrome
Aortic valve insufficiency
Hypothyroidism

25
Q

Why is anesthesia diffucult in donkeys and mules?

A
  • Difficult to handle them
  • Narrower, ‘deeper’ larynx, trachea
  • More difficult jugular catheterization
  • Eliminate drugs faster, more frequent dosing
  • Drug should be 30% higher than for a horse
  • Plasma GGT 3x > equine
26
Q

How would you do sedation on a donkey or mules?

A

first IM if necessary then IV alpha2 agonist in higher dose!

27
Q

Tiva in mules:

A
  • Triple drip most common: alpha2 agonist + ketamine + GGE- (in small donkeys can be easily overdosed
  • GGE sensitivity reported! – hemolysis , don’t use!
28
Q

PIVA in mules:

A
  • Inhalational an.
  • NSAIDs: shorter elimination half-life than in the horse
  • Opioids: ileus is a risk!
  • Prone to hypoxemia
29
Q

why is anesthesia difficult in horses with intestinal emergencies?

A
  • Risk is 10x that of elective cases!
  • increased risk is multifactorial:
  • cardiovascular compromise + endotoxemia
30
Q

Sedation in a horse with intestinal emergency:

A

-alpha2 agonist: xylazine 0.3 – 1 mg/kg
-NSAIDs (antiendotox-flunixin, analgesic)
-Opioids: with alpha2 agonist combo
-Phenotiazines contraindicated!! Don’t for shock patients!
Anti-endotoxin: polymixin B, anti-endotoxin serum, flunixin, DMSO
AB: beta-lactam (penicillin) + aminoglycoside (gentamicin) before induction

31
Q

What is important when we do anesthesia in a pregnant horse?

A

Maintain blood pressure + O2

Min. sx time (fetal exposure)

32
Q

Sedation in a pregant horse:

A

alpha2 agonist
Opioids: cross placental barrier and reach the foal
Flunixin: blocks PGF2alpha release, protects against fetal loss after uterine manipulation, because it blocks the prostaglandins.

33
Q

Tiva in preganantt horse:

A

can cause fetal bradycardia

34
Q

Piva in pregart horse:

A

lidocaine can be toxic

35
Q

what are the signs during anesthesia with indicated hyperkalemic periodic paralysis?

A 
Hyperkaema
Tachy/bradycardia
ECG changes
Hypotension
Muscle tremor
Hypercapnia
Normothermia
Tx: Ca-gluconate inf., Dextrose inf., insulin (K+) decreased IV
36
Q

Which horse breeds are more prone to malignant hyperthermia?

A

-QH, thoroughbred, appaloosa, Arabian, pony

37
Q

First sign of malignant hyperthermia:

A
  • First sign : ETCO2 increase, PaCO2 increase, muscle rigidity, tachypnea, body temp increase
  • Metabolic ac., arrhythmia, CK and (K+) increase
  • Lethal if left untreated!
38
Q

What is important prior to anesthesia of a horse with RAO?

A

secretolytic, bronchodilatator

39
Q

Inhalational anesthesia in horse with RAO:

A
  • IPPV + O2 supplement (High oxigenisation)
  • Longer inspiratory – expiratory phase (defective elastic recoil, airway closure)
  • Albuterol (2 microg/kg aerosol = bronchodilator) into ET Ventolin spray
40
Q

Anesthesia of the horse with cardiovascular problem:

A
  • Rare: conducting system / congenital defect / myocardial disease
  • Commonly 2. cardiovascular compromise
  • Hypovolemic shock (severe hemorrhage)
  • Endotoxemia, sepsis (colic)
  • Profound electrolyte imbalance (uroperitoneum)
  • Stabilize prior to an.!
  • Low doses of sedatives, pre-emptive analgesic drugs
41
Q

INDUCTION of the horse with cardiovascular problem:

A

GGE/benzodiazepins + ketamine

Equine medicine (17 decks)

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