Renal, Hepatic, & Neurologic Cases Flashcards
What is used to categorize renal insufficiency?
renal function testing: BUN, creatinine, SDMA, UPC, BP, USG
- IRIS staging guides anesthesia planning with increased risk at stage 2 and beyond
How do patients with renal insufficiency present?
- appear unkempt and lethargic
- PU/PD
- poor appetite
- poor appetite with weight loss
- hypertensive
- anemic
What balance is important to maintain in patients with renal disease?
- fluids: balance in and out to maintain a fixed urine output
- BP: hypertension does NOT protect from hypotension
What comorbidities are common in patients with renal disease?
- heart disease
- diabetes
- hyperthyroidism in cats
How are cats with renal disease sedated before procedures?
half dose Gabapentin - high renal excretion!
- can empirically increase if sedation is not achieved
How are prior anti-hypertensive medications given before an anesthetic event?
withhold within 12-24 hr of procedure
What sedation is commonly used for IVC placement (if necessary) in cats and dogs with renal disease?
DOGS - Butorphanol or pure mu agonist, cautiously use Dexmedetomidine at micro-doses, Alfaxalone
CATS - Butorphanol, Midazolam, Alfaxaone
What additional consideration is needed prior to anesthetic events in patients with renal disease?
HYDRATION - 1-2 hours of IV fluids at presentation
- recommended to do these patients early to give adequate time for recovery
What are the 3 most common induction agents used in patients with renal disease? Which one needs to be used carefully?
- Ketamine - high renal excretion, good with multimodal therapy at low doses
- Propofol
- Alfaxalone
Other than various induction agents, how is inhalant usage minimized in renal patients?
- Fentanyl or Ketamine CRIs
- pure mu opioids
- local blocks when possible
What monitoring equipment is ideal in patients with renal disease?
- BP*
- pulse oximeter
- capnograph
- temperature
- ECG
have a dedicated anesthetist!
How is hypotension, bradycardia, hypoventilation, and hypothermia avoided/troubleshot in patients with renal disease?
treat aggressively with Dopamine CRI, cautiously with fluid boluses
treat if BP is low with anticholinergics (Atropine)
maintain at 40-50 mmHg
prewarm - hypothermia decreases MAC
What especially contributes to worse outcomes following anesthesia in patients with renal disease?
hypoxemia
What is especially important in the recovery period in patients with renal disease?
get them back to drinking and eating normally ASAP
What normal functions are altered by hepatic disease?
- nutrient storage and supply
- lipid, protein, and carb metabolism
- albumin and coagulation factors
- biotransformation and biliary excretion (barbiturates last longer!)
- removal of ammonia and urea production
What is the aim to anesthesia for hepatic disease? What is generally avoided?
maintain hepatic perfusion and oxygenation
- Acepromazine: irreversible, long-lasting
- Dexmedetomidine: decreased hepatic perfusion
What 3 things are done in anesthesia planning for patients with portosystemic shunts?
- avoid benzodiazepines that would worsen hepatic encephalopathy
- monitor blood glucose
- evaluate albumin levels pre and post
What does the high energy demands of the brain result in?
no reserves of substrate or oxygen is present
What is cerebral blood flow closely coupled with? Why is this significant with anesthesia?
cerebral metabolic rate of oxygen consumption
- anesthesia can uncouple these and decrease glucose consumption
- inhalant anesthetics alter autoregulation, where CBF becomes passively dependent on CPP
What results from hypotension and hypertension to the brain?
MAP < 60 mmHg = cerebral ischemic
MAP > 150 mmHg = cerebral edema or hemorrhage
What is cerebral perfusion pressure? What happens when it increases/decreases?
CPP = MAP - mean ICP
(proportional to CBF)
- INCREASED = arteriolar vasoconstriction
- DECREASED = arteriolar vasodilation
What is indicative of intracranial disease?
- abnormal mentation
- dullness
- obtunded
- aimless wandering
- circling
What are 3 symptoms of increased intracranial pressure? How is this treated before anesthetic events?
- vomiting
- papilloedema (ocular disc swelling)
- pupillary dilation
reduce ICP with mannitol or hypertonic saline
What is indicative of intracranial herniation? Is this treated?
Cushing’s reflex - increased BP, bradycardia, irregular ventilation
bradycardia is NOT treated
What 2 consequences of anesthesia need to be avoided in patients with neurological disease? How are patients positioned
- hyperthermia - maintain normothermia to slight hypothermia
- hypercapnia - hyperventilate to ETCO2 of 33-35 mmHg (never below 30)
head elevated with no jugular compression
What part of anesthesia should be minimized in patients with neurological disease? Why?
inhalants
cause increased CBF in the face of reduced demand of oxygen, resulting in a worsened ICP
What 3 drugs are avoided/reduced in patients with neurological disease?
- Acepromazine - irreversible
- high induction doses of Ketamine
- inhalants
What 5 drugs are used in patients with neurological disease?
- Propofol or Alfaxalone induction/TIVA
- pure mu agonists - reversible!
- analgesic Ketamine CRI
- Benzodiazepines
- low/minimal inhalants after hyperventilation commenced
Hypertension and autoregulation of BF:
What are the 3 levels of hypertension?
NORMOTENSIVE = SBP < 140 mmHg
- prehypertensive = 140-159 mmHg
- hypertensive = 160-179 mmHg
- severely hypertensive = > 180 mmHg
What are the 4 most common treatment options for hypertension?
- Amlodipine
- Telmisartan
- Benazepril/Enalapril
- Atenolol
How is hypotension determined in chronically hypertensive patients?
these patients have adapted to having high BP, so hypotension is considered at a higher value
