1)     RECOMMENDATIONS

a)      General Approach

i)        Avoid any increase in intracranial pressure

b)      Pre-anesthetic Medications

i)        Benzodiazepines are generally well tolerated

ii)       Opioids are generally well tolerated

(1)   Can cause respiratory depression so watch ETCO₂

(2)   Vomiting can increase ICP

(a)    If this is a concern, consider butorphanol or oxymorphone as a premed then add mu agonist after induction

iii)     Acepromazine

(1)   If not in shock

(2)   If not anemic

(3)   If not seizuring (controversial/tenuous association)

iv)     Diuretics if not in hypovolemic shock

v)      Mannitol IV may be a consideration to decrease intracranial pressure

vi)     Prednisolone sodium succinate or dexamethasone IV may be considered if you have a known steroid responsive disorder

c)      Induction

i)        Thiopental

(1)   If not in shock and not anemic

ii)       Opioid and benzodiazepine

(1)   Watch for hypoventilation – keep ETCO₂ under 30

iii)     Propofol

(1)   Watch for apnea – keep ETCO₂ under 30

d)      Maintenance

i)         Isoflurane or sevoflurane

(1)   Watch respiratory depression and elevated CO₂

(2)   Isoflurane and sevoflurane may both increase ICP at higher concentrations even if normocapnic

(a)    Avoid concentrations above 1.5 MAC

ii)       Propofol

(1)   Appears capable of maintaining anesthesia with lower ICP compared to isoflurane or sevoflurane

e)      Support

i)        Ventilate as needed to maintain an ETCO2 of 25 to 30 mmHg

(1)   ETCO₂ of 20 decreases cerebral blood flow

(2)   As ETCO₂ increases above 30 mmHg vasodilation follows causing increased intracranial pressure

2)     PRECAUTIONS

a)      General

i)        Avoid:

(1)   Occluding jugular veins

(2)   Coughing

(a)    Lidocaine 1mg/lb can help suppress cough reflex

(3)   Hypercapnea

(a)    Keep ETCO₂ between 20 and 30

(i)      As ETCO₂ increases, vasodilation follows causing increased intracranial pressure

(4)   Vomiting

(5)   Avoid hypertension

(a)    Systolic blood pressure should not exceed 150 mm Hg

b)      Pre-anesthetic Medications

i)        Avoid acepromazine if hypotensive

ii)       If vomiting is considered a significant concern avoid morphine and hydromorphone

(1)   May also consider avoiding oxymorphone as it too can cause vomiting

(2)   Xylazine also often causes vomiting

c)      Induction

i)        Avoid:

(1)   Ketamine

(2)   Telazol

d)      Maintenance

i)         Avoid halothane (causes undesirable vasodilation)

e)      Support

i)         Avoid hypoventilation

(1)   Maintain ETCO₂ monitoring

(2)   Ventilate as needed to keep ETCO₂ between 25 and 30

(a)    As ETCO₂ increases, vasodilation follows causing increased intracranial pressure

ii)       Avoid hypertension

(1)   Systolic blood pressure should not exceed 150 mm Hg.