Troubleshooting Small Animal Anesthesia Flashcards
What are the normal systolic and diastolic blood pressures seen in anesthetized patients? What is indicative of hypotension and hypertension?
- SYSTOLIC = 100-130 mmHg
- DIASTOLIC = 60-100 mmHg
(mean = 80-120 mmHg) - HYPOTENSION = SAP <80 mmHg, MAP <60 mmHg
- HYPERTENSION = SAP >130 mmHg, MAP >120 mmHg
What is the most common consequence of hypotension? What is over 15 minutes of hypotension associated with?
poor perfusion of the brain, heart, kidneys, GIT, and liver
long-term damage to kidneys
What is arterial blood pressure a product of? Why is it so important?
CO and systemic vascular resistance
critical determinant of tissue/organ perfusion and oxygen delivery
If a patient is chronically hypertensive, how is hypotension determination changed?
> 20-40% reduction from awake baseline
In what ways can the surgeon cause hypotension while performing their surgery?
- hemorrhage
- vascular compression (vena cava)
What 5 patient factors should be checked when hypotension is present?
- HR and rhythym, pulse quality, CRT
- oxygenation, ventilation, anesthesia machine integrity
- anesthetic depth
- bradycardia, profound tachycardia
- cardiac arrest
What anesthetic machinery should be checked with hypotension? How is it adjusted?
oscillometric or Doppler
- check BP cuff placement, size, and tightness
- change position of cuff
- try another machine
What are the 2 most common ways to troubleshoot hypotension?
- decrease inhalant concentration and increase or add injectable drugs
- treat bradycardia
In what 2 ways is bradycardia treated in patients with hypotension?
- bolus fluids +/- hypertonic saline +/- blood products or colloids depending on comorbidities (DON’T keep bolusing if there is no improvement)
- administer inotropes or pressors - dopamine, dobutamine, vasopressin, norepinephrine, epinephrine (emergency)
What are the 2 phases of Dexmedetomidine affects? How does this alter ways of troubleshooting its effects?
- initial 45 mins - vasoconstriction causes hypertension with reflex bradycardia
- after 45 mins - central sympathetic nervous system depression leads to hypotension and continued bradycardia
treating bradycardia (atropine, glycopyrrolate) within phase 1 would cause increased HR in the face of high afterload = increased myocardial work
- wait until phase 2, where hypotension can be resolved by improving HR
What is the normal arterial CO2 and ETCO2 in normal patients?
35-45 mmHg
> 50 mmHg
In what 7 ways should a patient with hypoventilation be checked?
- HR and rhythm, pulse quality, CRT
- anesthetic dept - jaw tone, palpebral reflex, response to surgery)
- check oxygen supply, machine, flow meter rate, and machine integrity
- check ETT for kinks or obstruction
- check ETCO2 and waveform quality
- check quality of spontaneous ventilation
- ventilate by hand and assess compliance
What 4 actions should be considered in patients experiencing hypoventilation?
- assisted or mechanical ventilation
- decreasing anesthetic depth
- reducing respiratory depressant drugs
- reversal
What 5 things should be ruled out in patients experiencing hypoventilation?
- airway obstruction
- asthma or chronic airway disease
- excessive dead space (pulmonary or equipment)
- external compression of chest impending excursion (tight chest wrap)
- increased RR = high inspired CO2
What anesthetic depth is associated with hypoventilation?
too deep or paralyzed
What is ventilation defined by? Why is ETCO2 commonly lower than arterial CO2?
CO2 levels
physiological dead space
What is the primary motivator for breathing? How does anesthetics affect this?
arterial CO2
depress ventilatory response to CO2 at sub-anesthetic doses
What 3 things does the measurement of ETCO2 depend on?
- production of CO2 - metabolism
- delivery of CO2 to lungs - CO
- removal of CO2 - ventilation
What is indicative of hypoxemia and dangerous hypoxemia?
SpO2 < 95%
SpO2 < 90%; PaO2 < 60 mmHg
In what 6 ways should a patient be checked for hypoexmia?
- HR and rhythm, pulse quality, CRT
- anesthetic depth - jaw tone, palpebral reflex, response to surgery)
- check oxygen supply, machine, flow meter rate, and machine integrity
- check ETT for kinks or obstruction
- check ETCO2 and waveform quality
- ventilate by hand and assess compliance
What maneuver can be considered in patients experiencing hypoxemia? What diagnostics can be performed?
PEEP
- thoracic radiographs
- arterial blood gas
What are some rule outs for hypoxemia?
- airway obstruction
- endobronchial intubation
- extubation
- anaphylaxis
- aspiration
- asthma
- diaphragmatic hernia
- pneumothorax, pulmonary edema
- congenital heart disease/shunt
- embolus
- low cardiac output
- abnormal hemoglobin
- heart failure
What is a normal PaO2 reading? What are 5 causes of hypoxemia?
5x FiO2
- room air is 20% O2 - PaO2 = 100 mmHg
- under anesthesia is 100% O2 - PaO2 = 500 mmHg
- low FiO2
- hypoventilation
- V/Q mismatch
- R to L shunt
- barrier to diffusion
What determines oxygen delivery throughout the body?
CO and oxygen content in the blood
What is considered bradycardia in large dogs and small dogs/cats? With hypotension?
LARGE DOGS - <60 bpm; <50 bpm
SM DOGS/CATS - <90 bpm; <70 bpm
What 5 things should be checked on in patients with bradycardia?
- pulse quality, CRT
- ECG
- verify oxygenation and ventilation
- hemodynamics
- temp check for hypothermia
What aspect of the anesthesia machine should be altered in patients with bradycardia? What 2 medications can be used?
decrease or discontinue inhalant
- anticholinergics - glycopyrrolate, atropine
- reduce or reverse opioids or alpha-2 agonists
What electrolyte abnormality can cause bradycardia?
hyperkalemia can lead to cardiac disease/arrest
What breeds naturally have high vagal tones that can cause bradycardia? What surgical manipulation can lead to it?
brachycephalic dogs
increased ocular pressure and GI manipulation
What is considered tachycardic in large dogs and small dogs/cats?
LARGE DOG - >140 bpm
SM DOG/CAT - >180 bpm
What 5 things should be checked in patients with tachycardia?
- pulse quality, CRT
- ECG
- oxygenation and ventilation
- BP
- surgical manipulation - blood loss, hypovolemia
What 2 aspects of surgery are commonly associated with tachycardia?
- hypotension and hemorrhage
- hypoventilation and hypoxemia
What anesthetic depth is associated with tachycardia? How can it be treated?
too light and painful
increase analgesia and/or inhalant depending on BP
What are some causes of tachycardia?
- tachyarrhythmia
- adrenal tumor
- hyperthermia
- anaphylaxis
- iatrogenic - anticholinergics, inotrope overdose, catecholamine
What are common signs seen in patients that will not stay asleep?
- panting
- moving
- waking up
- twitching
- hypertensive
- tachycardia
What aspects of the patient should be checked if they are not staying asleep?
- HR rhythm, pulse quality, CRT
- respiratory rate and character
- anesthetic depth - jaw tone, palpebral, response to surgery
- confirm intubation
- inhalant - filled vaporizer, connected
- oxygenation, ventilation
What 4 things are commonly done in patients that won’t stay asleep?
- increase oxygen flow rate to speed up inhalant delivery
- assisting or controlling ventilation
- additional analgesia (increase or add CRIs)
- reconfirm depth sign
What are the 2 most common causes of patients remaining awake?
- anesthesia machine constant - machine does not buildup adequate inhalant level to maintain anesthesia before patient wakes up following induction
- induction drug causes hypoventilation - patients does not take up inhalant, wakes up, give more propofol, continues to not ventilate properly (vicious cycle!)
What is considered a prolonged recovery? How can the patient be stimulated?
lasting more than 45 mins
- discontinue all inhalant and injectable anesthetics
- rubbing
- tickling ears
- changing recumbency
What monitoring is especially important in patients undergoing a prolonged recovery? What else is checked for?
- hypothermia
- hypotension
- hypoxemia
- hypercarbia
hypoglycemia, anemia, electrolyte or acid-base disorders
How are analgesics altered in patients undergoing a prolonged recovery?
decrease, discontinue, or reversal
- typically do not discontinue, or reverse, since pain relief is still needed post-surgery
What is reflux/regurgitation? What aspect of the patient should be checked?
stomach contents move passively into esophagus +/- pharynx
check ETT cuff/seal - should have no leak when lungs are inflated 20-25 cm H2O
What should be done if reflux/regurgitation is observed?
- suction esophagus with red rubber
- flush water or saline until clear
- keep cuff inflated and patient sternal until there is strong swallowing and chewing
What is avoided when a patient has regurgitated? What medications are commonly recommended?
pushing a catheter into the stomach, unless there is significant fluid present
- local bicarbonate instillation
- Famotidine
- Sucralfate
What should be monitored post-anesthesia if a patient regurgitates?
- cough
- increased RR
- further regurgitation
