Neonatal and Geriatric Anesthesia Flashcards
Why is neonatal respiratory rate 2-3 times higher than in adults? What effect will this have on induction with inhalant anesthetics?
Vt is the same as an adult (10-15 ml/kg) so the respiratory rate must be 2-3 times greater for minute volume to meet oxygen demand
High alveolar vent increases gas exchange
What happens to cardiac output if bradycardia occurs in a neonate?
Cardiac output decreases
Is an 8 week old puppy or kitten a neonate?
No, it is considered pediatric
Neonatal: birth to 2 weeks
Pediatric: 8-2 weeks
Beyond 8 weeks, they are considered miniature adults for anesthesia
An 8 week-old puppy has a mean arterial blood pressure of 55 mmHg during anesthesia. Is this puppy hypotensive?
No. This is normal for a puppy that is 8 weeks old. Puppies tend to have a lower MAP than adults.
Why are alpha-2 agonists such as xylazine or medetomidine not a particularly good agents in neonatal and pediatric patients?
Because these cause vasoconstriction, there will be an increased afterload and inability to deal with it at this age
Under what conditions should glucose-containing fluids be administered to young animals during anesthesia? Which glucose-containing solution would be least likely to result in water overload, diuresis, and dehydration?
They will only get glucose-containing fluids if they truly need glucose
½ strength LRS with 2.5% dextrose
Can injectable anesthetics be used in 6-8 week-old puppies and kittens? Why or why not?
Yes. They are now pediatrics rather than neonates and their neurological system is more developed
Do older animals generally require more or less anesthetic agent?
Less
Is the anesthesia duration for older animals generally longer or shorter for a specific anesthetic dose?
Longer
Does age by itself increase anesthetic risk? Why or why not?
No, biological and physiological age are more important than chronological age
Why might recovery from lipophilic anesthetics be prolonged in the older patient?
There is an increase in adipose tissue and an increase in total distribution volume for lipophilic drugs
Older animals are often borderline hypoxic (PaO2 60-80 mmHg) when awake. Why?
They have an increase in alveolar deadspace
Describe an easy, inexpensive physical method that you can use in a practice setting to determine whether an older animal has adequate cardiac reserve to undergo anesthesia.
Exercise challenge: take them out and run them around. If you get tired before the dog gets tired, they’re probably fine. If they have a hard time, then they have cardiac problems and should not undergo anesthesia
Why would drugs that cause the heart to beat faster (i.e. antimuscarinics, ketamine) not be good drugs for the older patient?
This will make them tachycardic and increase myocardial consumption causing arrhythmias
What is the O2 rate for neonates and pediatrics?
2-3 times greater than adults
What is respiratory control like at birth?
Immature
What are respiratory considerations for neonates and peds?
Increase risk of pulmonary shunting
Greater risk of airway obstruction
What are circulatory considerations for neonates and peds?
Neonatal circulatory system is low pressure, low volume, low peripheral resistance Reduced myocardial contractility Immature ANS Resting CO near maximal Reduced ventricular compliance
By how much do iso and sevo reduce BP?
20-30%
How much do Hgb levels decrease by 2 weeks of age?
40%
What does hematopoesis begin?
> 4 weeks
What are metabolic considerations for neonates and peds?
Lower plasma albumin, larger % total body water, lower body fat, greater distribution CO to vessel-rich organs, reduced hepatic and renal function
What are renal considerations for neonates and peds?
Neonatal dog kidney is immature at birth
Glomerular filtration matures between 2-3 week; tubular secretion between 4-8 weeks
How do neonates thermoregulate?
Poikilothermic
What likely happens to thermoregulation with anesthesia?
Hypothermia
What does hypothermia result in?
Bradycardia
Decreased CO and BP
Promonged recovery due to reduced drug clearance
What are anesthetic recommendations for neonates and peds?
Accurate body weight
Preoperative fasting is unnecessary
Administer an antimuscarinic
Most sedative/tranquilizers can be used cautiously
Opioid are well tolerated
Avoid injectable induction agents < 4 weeks of age
ISo and Sevo are preferred inhalants
LRS
Keep wasm and dry
Non-rebreathing circuits for patients < 5 kgs
Consider local anesthetics for awake procedures
What happens to MAC as animals age?
It decreases
What happens to the liver with age?
Hepatic processes are unchanged, but heptaic mass and blood flow are decreased
What happens to the kidney with age?
Reduced renal mass, function, and reserve
What happens to CO with age?
Progressively decreases
What happens to contractility with age?
Relatively unchanged
What is increase CO met though in geriatric patients?
Moderate increase in HR, SV, and LVEDV
What happens to the autonomic reflexes with age?
Slower in onset
Less magnitude
Less effective in maintaining homeostasis
What causes decreased response in geriatric patients?
Beta-adrenergic agents
What causes unchanged responses in geriatric patients?
Muscarinic agents
Alpha-adrenergic receptor responses
What is stage A of canine heart disease?
At risk of heart disease (CKCS without a murmur, so Sven)
What is stage B1 of canine heart disease?
Signs of heart disease, but the dog is asymptomatic (a murmur with no structural changes)
What is stage B2 of canine heart disease?
Signs of heart disease. the dog is asymptomatic (a murmur with structural changes, left atrial enlargement)
What is stage C of canine heart disease?
Congestive heart failure is present or has been present and the dog is receiving treatment
What is stage D of canine heart disease?
Congestive heart failure is present and refractory to standard therapies
Patient requires hospitalization
What happens to lung elasticity and chest compliance as animals age?
They decrease
What are the anesthetic recommendations for geriatric patients?
Pharmacologically, simple is best
Choose drugs that do not require extensive metabolism for termination of action or for which specific antagonists exist
Fix underlying issues before elective anesthesia
What should be used as premeds in geriatric patients?
Opioids +/- low dose acepromazine or benzodiazepine
Alpha-2 agonists
Low dose ketamine in cats
Avoid antimuscarinics unless heart block or significant bradycardia is present
What is used for induction of geriatric patients?
Suitable IV hypnotics include alfaxalone, etomidate, or propofol
Provide O2
Consider local anesthesia +/- sedation for minor procedures
What is used for maintenance and recovery in geriatric patients?
Provide O2
Inhalant agents are preferred for long procedures
Propofol or alfaxalone CRI +/- opioid
Avoid hypotension
Avoid hypothermia, so work fast
Observe closely in recovery and provide heat if needed
