Emergency Anesthesia Flashcards
What are the 3 classes of sedatives most commonly used in the emergency setting?
Benzos, alpha 2s, and phenothiazines (+ opioids)
What are some pros of using a phenothiazine (such as ace) for sedation?
- Reliable sedation
- may increase threshold for arryhthmias
- antiemetic (centrally antidopaminergic)
- prevents histamine release
What are some cons to using a phenothiazine (such as ace) for sedation?
- Not reversible
- Hypotension (alpha blockade, vasodilation)
- Platelet aggregation inhibitor
- long acting, esp. with liver dz
- mild resp depressant
- no analgesia
- Minimal sedation in cats
What are some pros of using an alpha 2 agonist (such as dexmed or xylazine) for sedation?
- Excellent sedation
- Excellent muscle relaxant
- Mild analgesia
- Reversible with atipamezole or yohimbine
What are some cons to using an alpha 2 agonist (such as dexmed or xylazine) for sedation?
- Hypertension (alpha 1/2 stim, vasoconstriction), followed by hypotension (central symp blockade resulting in decr in CO)
- Severe bradycardia (reflex bradycardia and central symp blockade)
- May cause emesis
- 1st/2nd/3rd degree AV block
- Depresses resp center
- Promotes diuresis
- Inhibitis insulin, may produce hyperglycemia
What are some pros to using a benzo for sedation?
- Minimal CV effects
- Amnestic
- Midaz = water soluble, can be given IM/SQ
- MAC sparing
- Reversible w/ Flumazenil
- Anticonvulsant
- Good muscle relaxant
What are some cons of using a benzo for sedation?
- May cause excitement in cats/some dogs
- Prolonged effects w/ liver insufficiency
- Diazepam not water soluble - ONLY IV
- No analgesia
- Controlled substances
Combining what two types of agents creates neuroleptanalgesia?
Opioids and a tranquilizer or sedative (typically a benzo)
What are the pros to using a full mu agonist as an emergency sedative?
- Excellent analgesia
- Reversible w/ naloxone, naltrexone
- Mild cardiopulm effects (bradycardia, decr RR, dose dependent)
- Synergistic w/ tranqs/sedatives
What are the cons of using a full mu agonist as an emergency sedative?
- Dysphoria/excessive sedation
- panting/hyperthermia in cats
- decr GI motility
- Controlled drugs
- Vomiting
- Excitement/aggression in some cats
- Resp depression
What are the pros to using a partial mu agonist as an emergency sedative?
- Less dysphoria than full mus
- Less resp/GI effects than full mus
- Butorphanol can be used as partial reversal agent
- Buprenorphine is long lasting and can be given transmucosally in cats
- Good analgesic effect w/o significant dysphoria in cats
What are the cons of using a partial mu agonist as an emergency sedative?
- Less analgesia provided than with full mu
- butorphanol is short acting
- controlled drugs
T or F: Etomidate is a great choice as an induction agent in all emergency patients
False; etomidate is actually contraindicated in many emergency patients because it can suppress adrenal function for up to 6 hours following a single dose and the stress response is often necessary for survival in emergent patients
What induction agent can cause direct myocardial depression in patients with catecholamine depletion?
Ketamine
What are the cons of using an opioid and a benzo as induction agents (neuroleptanalgesia)?
- Swallowing reflex maintained
- Noise-sensitive during induction
- Use of controlled drug
- Only effective in dogs and cats w/ severe CB or neuro depression
- Resp depression
When using the Doppler method to measure blood pressure, what does the value most closely represent in dogs vs. cats?
- Dogs - systolic arterial pressure
- Cats - MAP
A sudden decline in end-tidal CO2 in the face of normal ventilation could indicate what?
A drop in CO, a loss of perfusion to the lungs (PTE), or cardiac arrest
What types of patients should you strongly consider administering blood products to prior to anesthesia?
- Patients with acute blood loss
- Patients showing clinical signs of decr O2 delivery (tachycardia, tachypnea, lethargy, weakness)
- Elevated plasma lactate levels
- PCV <20%
If administering whole blood, approximately 2 ml/kg of whole blood can be expected to raise the PCV by what percentage?
1%
What is the formula for calculating the amount of pRBCs to give a patient suffering from acute blood loss?
pRBCs (ml) = [(PCVdesired – PCVpatient)/PCVdonor] x 80 x weight(kg).
What two cardiac arrhythmias are most commonly seen with splenic disease?
VPCs and Vtach
What two induction agents should be often be avoided in a patient presenting with a hemoabdomen?
- Ketamine - may exacerbate ventricular arrhythmias
- Propofol - causes splenic engorgement, avoid if spleen is source of hemorrhage
What is meant by ‘permissive hypotension?’
- One aims to perfume the organs with some sort of minimum BP (70-80 mmHg systolic or 50 mmHg for MAP) to limit volume of resuscitation fluid required and hemodilution occurrence
- aimed in pursuit of hemostasis rather than BP
What are the recommendations for induction to place a pacemaker?
- Temporary pacemaker: opioid + benzo
- Permanent pacemaker: etomidate + midazolam (+/- ketamine)
Why might you not want to use PEEP and recruitment maneuvers in a patient already experiencing hypovolemic shock?
- Because both may severely depresss venous return and cardiac output
What is the recommended pre-med protocol for a lar par patient?
- Butrophanol + ace or low-dose dexmed
What are a few analgesic agents that can be used in the post-op period following a laryngeal tie back surgery to avoid opioids?
Ketamine, lidocaine, and NSAIDs
What are some principles to keep in mind when coming up with an anesthetic plan for a TBI patient?
- Patients are very sensitive to anesthetics and a lower dose of sedatives is required (if at all)
- benzos = preferred sedative d/t anti-seizure properities
- opioids are contraindicated (cause vomiting, resp depression, elevated ICP)
- ketamine should be avoided - causes elevated cerebral oxygen consumption
- Inhalants can cause dose dependent intracranial vasodilation, hypoventilation, and ICP elevations
- should be ventilated - end tidal CO2 between 30-35 mmHg
- should be kept mildly hypothermic (96-98F)
What is the anesthetic agent of choice for TBIs?
Propofol, typically TIVA
What is the Cushing’s reflex?
A sudden elevation in BP followed by a reduction in heart rate than may indicate elevated ICP
If you note a Cushing’s reflex in a patient, what should you administer?
2-4 ml/kg of hypertonic saline to reduce cerebral edema and decrease ICP
What drugs should be used for analgesic management and anesthesia for animals with spinal injuries?
Opioids with systemic lidocaine or low-dose ketamine, as well as antiemetics (IVDD dogs at risk for aspiration pneumonia)
What is the most common arrhythmia seen in a GDV dog?
Vtach, but can also see Afib and SVT
What are the physical parameters of early sepsis?
- Tachypnea
- Bounding pulses
- CRT <1 s
- Red MM
- Mental depression
- Hyperthermia
What are the physical parameters of late sepsis?
- Tachypnea
- Thready pulses
- CRT >2 s
- Pale MM
- Stupor, coma
- Hypothermia
- Organ failure
Fluid resuscitation in a septic patient should aim for what parameters?
- MAP of >65 mmHg
- adequate urine output
- maintain normal pH
What are the goals of anesthetizing patients with sepsis?
Maximizing oxygen delivery to multiple organs (kidneys, liver, heart, brain) and optimizing renal function
The anesthetic protocol for septic patients can include and avoid which drugs?
Can include:
- drugs that maintain CV stability (opioids, benzos)
- inhalants to lower MAC
- systemic lidocaine (be careful)
- low-dose ketamine
- PPV
Avoid:
- Etomidate (b/c it depresses the HPA axis)
Sedation, if absolutely necessary, for a parturient animal prior to a C-section should include what?
- Opioids +/- a benzo
- Morphine has lowest lipid solubility so cross placenta slowest, but can cause resp depression in fetuses
- AVOID ace (widespread dilation in shock patients) and xylazine (high fetal mortality rate)
What considerations should you have when performing an epidural on a pregnant animal?
- Typically performed under GA
- take 15-20 minutes to reach peak effect
- Total volume should be reduced by 20-30%
What is the best method of induction of pregnant animals?
Propofol (or Alfaxalone)
- masking down and ketamine are contraindicated
What ECG changes might you see in the case of a uroabdomen/uroperitoneum?
- Narrowing and ‘tenting’ of T waves
- Shortening of QT interval
- Prolonged PR interval
- Widening QRS complex
- Arrhythmias: Vfib or V asystole
What type of fluids should be used for fluid resuscitation in uroabdomen patients?
Isotonic crystalloids - LRS (small amount of K) or 0.9% NaCl (although lacks a buffer)
What are some treatments of hyperkalemia?
- Dextrose +/- insulin
- Sodium bicarbonate (refractory hyperK, good for treating metabolic acidosis)
- Calcium gluconate (cardioprotective- modifies threshold potential)
Why is positive pressure ventilation recommended in uroabdomen patient anesthesia?
- To prevent hypercapnia and consequent respiratory acidosis, as acidemia favors extracellular movement of K and can worsen preexisting hyperK
What should be avoided to prevent sudden increases in IOP, particularly in ocular anesthetic patients?
- Vomiting/regurg
- Stress/struggling
- Gagging/coughing
- Occluding jugulars or placing substantial pressure on neck
- Traumatic or forceful intubation
- Lowering the head below the rest of the body
- Putting pressure on eyelids (ie. Face mask)
- hypoxemia and hypercapnia
What are the preferred analgesics for ocular procedures?
- Opioids + antiemetics
- Ace or dexmed (remember alpha 2s can also cause vomiting)
What are some considerations for induction agents used in ocular procedures?
- Ketamine ONLY if given with a benzo
- Propofol ONLY if given with a benzo
- Etomidate can cause myoclonus, resulting in increased IOP
- Alfaxolone can also cause IOP increase
What is the oculo-cardiac reflex?
Caused by pressure or traction on eyeball, resulting in the development of bradycardia and bradyarrhythmias due to stimulation of the trigeminal and vagus nerves
- can treat persistent bradycardia with anticholinergic (atropine)
