Lesson 20 - Anesthesia in different life stages

What age is a neonate?

birth to weaning (4 weeks)

What age is a pediatric patient?

until 12 weeks

What is the metabolic rate of a pediatric patient like?

high metabolic rate with high oxygen consumption

Why do pediatric patients require more consideration when using anesthetic drugs?

1. limited organ reserve

2. decreased ability to respond to a physiologic challenge or change

What is increased in a pediatric patients body content?

water

What blood changes do pediatric patients have?

lower PCV and hypoalbuminemia

What nervous system dominates in pediatric patients?

parasympathetic nervous system

Why do pediatric patients have poor thermoregulatory ability?

1. immature system

2. low percentage of body fat

3. poor ability to shiver

4. poor vasoconstriction

What happens to a pediatric patients SAP and HR in the first four weeks of life?

1. HR decreases from 200 to 130 bpm

2. SAP increase from 66 to 120 mmHg

What is stroke volume dependent on in pediatric patients?

heart rate because of low stroke volume

What is a result of pediatric patients having a higher oxygen demand?

high minute volume meaning high respiratory rate

Why are pediatric patients at higher risk of atelectasis?

higher compliance of the chest wall

Why are pediatric patients at increased risk of airway obstruction?

1. large tongue

2. narrow upper airways

What are characteristics of pediatric hepatic systems?

1. immature for first 3-4 weeks

2. low enzymatic activity

3. low glycogen storage

4. limited glucogenogenic ability

What are characteristics of pediatric renal systems?

1. immature reduced GFR first 2-3 weeks

2. slower tubular secretion for first 4-8 weeks

3. low efficiency eliminating fluid load and regulating electrolytes

What makes a patient geriatric?

reached 75% of their breed-specific expected life span

What is geriatric age for dogs generally?

>8 years old

What is geriatric age for cats?

>12 years

What are general characteristics of geriatric patients?

1. neuronal degeneration

2. decrease in skeletal muscle

3. hypoalbuminemia

4. increase in body fat

5. impaired thermoregulatory system

What cardiac changes do geriatric patients have?

1. myocardial atrophy causing decreased contractility and cardiac output

2. fibrosis causing decreased compliance

3. valvular fibrocalcification

4. heart rate decreases

What is a cardiac consequence of geriatric patients having loss of vascular elasticity?

increased resistance to left ventricular output causing hypertrophy of the ventricle

What is the consequence of geriatric patients having less elasticity in the lungs?

1. decreases residual volume

2. increases functional residual capacity

3. increases closing volume

What are some characteristics of respiratory system in geriatric patients?

1. loss of strength of muscles of ventilation

2. decrease maximum breathing capacity

3. reduction in efficiency of gas exchange

What are the changes to geriatric renal system?

decreased RBF, GFR, tubular funcion, excretory capacity

What are the changes to geriatric hepatic system?

decreased hepatic mass and hepatic blood flow

Why are there decreased anesthetic requirements for pregnant patients?

progesterone and endorphin levels in the CNS

What changes to cardiac parameters during pregnancy?

1. increase heart rate

2. increase cardiac output

3. increase blood volume

4. increase plasma volume

5. increase arterial blood pressure

What is the packed cell volume and hemoglobin of pregnant patients?

decreased

What can happen to the posterior vena cava during pregnancy?

compressed during dorsal recumbency

Why is there increase BP with pregnancy?

1. increase cardiac output

2. decreased vascular resistance from estrogen

How does progesterone during pregnancy change the respiratory system?

increase sensitivity of respiratory center to CO2 which increases minute volume and increases PaCO2

How does the GI system change with pregnancy?

1. increase gastric emptying time and intragastric pressure

2. decrease gastric motility

3. decrease lower esophageal sphincter tone

4. increase gastric chloride ion and decrease pH

What occurs with the renal system in pregnancy?

1. increase renal plasma flow and GFR

2. decrease BUN and creatinine

What is uterine blood flow proportional to?

systemic perfusion pressure and inversely proportional to vascular resistance

What is the protocol for fasting neonatal/pediatric patients?

1. no fasting patients

What are the main blood analysis parameters for pediatric patients?

PCV, TP, glucose

What is the best access for pediatric patients for administering fluids?

IV then intraosseous then subcutaneous

What dose do we choose when dealing with pediatric patients?

lower dose range

What step of drugs is not usually needed for pediatric patients?

premedication

What premeds do we want to avoid in pediatric patients?

1. alpha 2 agonists

2. acepromazine

What premeds are indicated for pediatric patients?

benzodiazepines

What is important about opioids for premed in pediatric patients?

provides adequate sedation when used alone

What opioid is commonly used for pediatric patients?

fentanyl

What are the ways that we can induce anesthesia in pediatric patients?

1. mask induction

2. injectable

What is the preferred anesthetic gas for pediatric patients?

sevoflurane

What induction protocol is better for patients with respiratory disorders or dyspnea?

injectable

What is important about propofol in pediatric patients?

metabolized rapidly due to extrahepatic metabolic pathways

What is the side effect of propofol in peds?

CV/respiratory depression

What do know about alfaxalone for peds?

1. can be administered IM

2. CV/respiratory depression like propofol

What drugs can we use to induce peds patients?

1. propofol

2. alfaxalone

3. ketamine

What is important about ketamine with peds induction?

1. relative lack of cardiopulmonary effects

2. needs a sedative or muscle relaxant

3. longer duration

Why are the consequences of intubating ped patients?

laryngeal edema and spasm are easily produced

What type of ET tube is used in peds?

uncuffed

What tyep of breathing system is used for peds?

non-rebreathing

How do we maintain anesthesia in peds?

mostly inhalant anesthesia

When monitoring a peds patient, what other levels do we want to monitor?

glucose

What do we add to our fluids for peds?

2.5% glucose in LRS

What opioids are preferred for peds?

buprenorphine or butorphanol unless full mu agonist is needed

What drugs do we avoid in patients until 12 weeks of age?

NSAIDs

What is a way that we can reduce the general anesthetic requirements?

local anesthetics

What is important postop with peds patients?

1. temperature control

2. glycemic control

3. provide analgesia

4. restore normal feeding and behavior ASAP

What are geriatric patients at high risk of during anesthesia?

cardiorespiratory decompensation related to reduced compensatory capacity

What do we want to avoid with geriatric anesthesia?

1. fluid overload

2. reduce anesthetic time

What type of anesthetics agents are preferred in geriatric patients?

titratable agents with rapid recovery

What premedications do we avoid with geriatric patients?

1. alpha 2 agonists

2. acepromazine

What premedication is used for geriatric patients?

benzodiazepines cause profound sedation but less CVS effects

What do you want to do before inducing?

pre-oxygenation

What induction drugs are used in geriatric patients?

1. propofol

2. alfaxalone

3. etomidate

4. ketamine

When is etomidate used for geriatric patients?

severely compromised heart patients

What are the concerns with ketamine and geriatric patients?

increases myocardial oxygen demand

What type of induction do we want to avoid in geriatric patients?

mask induction

What protocol is used for maintenance in geriatric patients?

inhalant or CRI better than bolus

What do we need to keep in mind with inhalant anesthetics and geriatric patients?

MAC is reduced

What MAP do we want to try to keep geriatric patients at?

>70 mmHg

What drugs do we use for postop geriatric care?

1. opioids

2. NSAIDs

What do we want to avoid postop with geriatric patients?

post-anesthetic shivering which would increase oxygen demand

What do we want to avoid in pregnant patients?

anxiety, excessive cardiac depression, hypotension

Why do we want to avoid hypotension in pregnant patients?

1. uteroplacental perfusion is MAP dependent

2. sudden decompression of aorta and cava can cause decompression

What is the cardiac reserve like for pregnant patients?

reduced cardiac reserve

What position do we want to use for pregnant patients?

trendelburg position

What are pregnant patients at a high risk of with anesthesia?

regurgitation

What ASA status do we give to pregnant patients?

II

What is the fetal risk during early gestation?

teratogenesis and spontaneous abortion

What is the fetal risk during mid-gestation?

generally considered the safest period

What is the fetal risk during late gestation?

preterm labor or fetal death

What are considerations for anesthetic agents with pregnant patients?

increased CNS sensibility so reduced MAC and induction is faster

How does the placenta affect anesthetics?

1. highly permeable

2. ion trapping with opioids and local anesthetics

3. not permeable to NMBAs

Does maternal or fetal exposure last longer?

fetal because of immature metabolism and renal clearance

What sedatives are not indicated for C-section?

benzodiazepines

What are the effects of benzodiazepines with pregnancy?

1. minimal cardiovascular effects

2. transient neonatal depression

Which benzodiazepine is preffered in pregnancy?

midazolam

Why is alpha 2 agonist not great choice for pregnancy?

1. can reduce uterine blood flow

2. can cause fetal bradycardia

Why is acepromazine not recommended for pregnancy dogs?

prolonged maternal hypotension, compromising uteroplacental perfusion

What induction agents are used for pregnant patients?

1. alfaxalone

2. propofol

What injectable anesthetic is not indicated for C-section?

ketamine

Why is ketamine used with caution for pregnancy patients?

1. fetal stimulation or depression

2. increase uterine tone and sympathetic activity which can compromise blood flow

When are NSAIDs contraindicated for pregnant patients?

late gestation

What are the negative effects of NSAIDs?

1. reduce uterine blood flow

2. cause premature closure of ductus arteriosus

3. impair fetal renal function