Respiratory & Cardiac Disease Flashcards
What 3 pulmonary mechanics are altered with anesthesia?
- chest wall tone is lost
- functional residual capacity is reduced
- atelectasis is common/inevitable
How does anesthesia alter pulmonary function?
- blunts hypoxic pulmonary vasoconstriction, which is in charge of matching V/Q
- depressed hypothalamic reflexes, resulting in hypoventilation and hypoxemia (if there is no oxygen supplementation)
What is functional residual capacity? What happens when it is reduced?
volume of air present at completion of passive expiration = air reserve within the lungs
shunts, low V/Q, atelectasis
What primary and secondary problems are associated with brachycephalics?
PRIMARY = stenotic nares, hypoplastic trachea, aberrant nasal turbinates, elongated soft palate
SECONDARY = excessive oropharyngeal soft tissue, everted laryngeal saccules, laryngeal collapse, lower airway dysfunction
How does the anatomy of brachycephalics affect their anesthetic plan?
small upper airway results in dramatic resistance to flow
- hypoxemia, hypercapnia, relative hypertension, and higher vagal tone results with suppressed compensatory mechanisms
What 4 comorbidities are commonly seen in brachycephalic patients?
- GI disease
- obesity = decreased FRC and lung capacity
- ocular disease (corneal)
- skin disease
What history is important to get from owners of brachycephalics when planning anesthesia?
- snoring when asleep or awake
- exercise intolerance
- GI issues: vomiting, regurgitation, licking, swallowing
- anxiety or stress
- wotse symptoms
Why can physical examinations be particularly difficult in brachycephalic breeds? What additional diagnostics should be done before anesthesia?
upper airway noise makes auscultation difficult —> murmurs can be missed
- usual BW: PCV/TS, chem
- thoracic radiographs: regurgitation common in these breeds
Why is it important to lower anxiety in brachycephalics before they’re in the hospital?
increased RR and panting makes airway obstruction worse and there is a hihg likelihood of regurgitation and aspiration
- oral Trazodone and/or Gabapentin at home
- minimize time in hospital
How can regurgitation be prevented/minimized in brachycephalics?
- Omeprazole at home 2-4 days prior
- Pantoprazole or Famotidine pre-anesthesia
- Maropitant and Metoclopramide pre-anesthesia
What ASA status are brachycephalics considered?
ASA 2
What are 3 important parts of a pre-medication plan in brachycephalics? What can be used very carefully?
- oral sedation and GI meds at home
- Acepromazine
- Butorphanol: anti-emetic effect
- pure mu agonists: less likely to cause vomiting when administered IV
- Dexmedetomidine: low dose in fractious dog, MUST monitor respiratory function carefully
Why is pre-oxygenating brachycephalics especially important?
if pre-oxygenated, it takes on average 300 seconds to desaturate compared to 70 seconds if not pre-oxygenated
How does the source of oxygen affect PaO2?
- mask = 380 mmHg
- flowby = 180 mmHg
- room air = 82 mmHg
How is hypoxemia avoided in brachycephalics?
- pre-oxygenate
- slow administration of induction drugs (titrate!)
How care brachycephalics properly intubated? How are ET cuffs checked?
- use appropriately sized larygnoscope
- keep in sternal position with extended neck and raised head
- proper size - tend to have smaller ET tubes than expected due to their hypoplastic tracheas
careful inflation to hold at 20 cm H2O pressure
What anti-inflammatory is preferred for intra-op use in brachycephalics?
steroids —> want the option to still use NSAIDs for airway infalmmation
What should be done while brachycephalics are recovering?
- ETT and induction drugs available for reintubation
- clean oropharynx, suction, and monitor for airway edema
- supplemental oxygen
- leave ETT in as long as possible
How does the cause of cough differ in dogs and cats?
- DOGS: lower airway vs. tracheal vs. cardiac
- CATS: inflammatory airway disease vs. chronic bronchitis vs. lung/heartworm
What is indicative of cats with asthma on physical exam? What needs to be ruled out first?
increased bronchovesicular sounds on all fields (sometimes louder on one side) and expiratory wheezing
HW disease, other parasites, infection
What are the 2 major anesthetic concerns in asthmatic cats?
- hypoventilation - worsened by obesity, which is common in these cats
- hypoxemia - bronchoconstriction, reduced FRC, atelectasis
How are asthmatic cats recovered following anesthesia?
on oxygen until extubation and may even need it after
- monitor until “normal”
What 2 things need to be controlled in asthmatic cats before anesthesia?
- cough and wheezing - steroids, Doxycycline, Fenbendazole, bronchodilators
- stress - oral anxiolytics (Gaba at home) night before and morning of
What is especially important to monitor in asthmatic cats?
- ETCO2
- SpO2
What is the characteristic capnograph seen with airway obstruction?
shark fin sign
- also seen with mucus plugs in ETT
What are the main functions of alpha-1 and beta-1 receptors on the cardiovascular system?
ALPHA-1 = vasoconstriction
BETA-1 = increased force and rate of contraction, bronchodilation and skeletal muscle vasodilation
Is a heart murmur always associated with heart disease? What helps with anesthesia planning?
NO
knowing the cause helps assess risk —> signalment, history, auscultation, pulse quality and rhythm, lung sounds
What diagnostic is especially important in patients with heart mumurs? What else is done?
echocardiogram - give information on heart function and structure
- thoracic radiograph - cardiac size and shape, LA size (CHF), pulmonary edema (dog), pleural effusion (cats)
- ECG
- blood biomarkers - pro-BNP
What are the 3 major causes of heart murmurs in small animals?
- valvular insufficiency - low CO and HR, congestion
- valvular stenosis - ventricular arrhythmias
- cardiomyopathy (DCM, HCM) - low CO, arrhythmia
What increases regurgitant flow in the heart?
vasoconstriction —> avoid alpha-2 agonists in animals with valvular insufficiency
What are the 4 major anesthetic concerns in patients with heart mumurs? What are the anesthetic goals?
- hypotension
- bradycardia
- arrhythmias
- congestion - CHF
reduce stress, support normal CV and respiratory function, manage pain
How should established heart medications be giving before an anesthetic event?
continue them —> if patient has not taken them or is in risk for CHF, delay anesthesia
What needs to be avoided in patients with valvular stenosis? What causes this?
tachycardia
- stress and anxiety
- oxygenation
What needs to be avoided in patients with valvular insufficiency? What causes this?
increases in peripheral vascular resistance and bradyacrdia
- hypotension and hypoxemia
- CHF
- alpha-2 agonists
- stress and anxiety
What needs to be maintained in patients with dilated cardiomyopathy? How?
myocardial contractility
etomidate use
What is hypertrophic cardiomyopathy?
asymmetric thickening of the myocardium, causing diastolic dysfunction and LV outflow obstruction
What are the 3 hemodynamic goals for patients with hypertrophic cardiomyopathy? What drugs are especially helpful? What should be avoided?
- maintain preload, afterload, and slower HR
- manage arrhythmias
- careful with fluid load
antiarrhythmics and alpha agonists for BP support
stress, anxiety, pain = sympathetic stimulation = increased HR
