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Anesthesia > Anesthetic Complications > Flashcards

Anesthetic Complications Flashcards

1
Q

What are your primary goals for a GA event?

A

Unconsciousness, Analgesia, Immobility/muscle relaxation

We also want to minimize complications and provide client satisfaction

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2
Q

What are common complications of GA?

A

Hypoxia
- Hypotension and hypoxemia

Hypothermia
Hypoventilation
Hemorrhage
Pain
Myopathy
Neuropathy

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3
Q

What are the “4 H’s” that we must be aware of in every animal, every anesthetic episode?

A

Hypoxia
- Hypotension

Hypothermia
Hypoventilation

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4
Q

Why do we care about hypoxia?

A

Well we must balance oxygen supply with oxygen demand if not hypoxia can occur.

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5
Q

What is DO2?

A

this is oxygen delivery to tissues and DO2 determines O2 supply

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6
Q

Hypoxia occurs when?

A

DO2<VO2 <– this is O2 consumption
Oxygen delivery (supply) is less than the demand

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7
Q

How is DO2 determined ie what two components make up DO2?

A

DO2= CaO2 * CO
SO hypoxia occurs when there is a decrease in CO or CaO2

CaO2=Arterial oxygen content

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8
Q

How is CO clinically measured?

A
  • Not common in vet med
  • You can use Mean Arterial Pressure (MAP) as a surrogate
    a. Make sure you consider SVR when evaluating and also consider what drug you have given to animal because you can have vasodilation while having low CO depending on drug given
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9
Q

Why is else is MAP important?

A

Its important for blood flow to tissues and the tissues/organs can autoregulate pressure and bloodflow in a certain range (50-150 mmHG)

Can sub any blood flow on y axis except for myocardial BF because that perfuses during diastole.

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10
Q

Horses and Large ruminants need to Blood pressure monitored carefully after GA. Why?

A

Well MAP is important in muscle blood flow
Horses have to stand up and they’re not used to laying down for hours on end without having some ability to shift their limbs and shift weight around. Horses also have to stand up after GA

LA place alot of external weight when in recumbency which decreases blood flow to those muscles
so were really worried about hypotension.

Also if they already have a low BP this can decrease perfusion to the muscles.

SO this MAP is so important in our LA species.
- you want a minimum of 70 MAP to maintain adequate blood flow in horses.

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11
Q

What arterial pressure is considered hypotensive?

A

MAP<60-65 mmHg
- >70-80 mmHg in horses and large ruminants

SAP<85-90 mmHg
Treatmet depends on underlying mechanisms

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12
Q

How is CO determined?

A

CO=HR*SV

SV –> mL/beat

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13
Q

What must you manage first in a hypotensive episode?

A

Decreased CO

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14
Q

How is MAP and CO related?

A

MAP=CO*SVR so if MAP decreases= decrease in CO * SVR

CO=HR* SV so if CO decreases= decrease in HR * SV

Therefore decreased HR causes decreased CO and can cause a decreased MAP

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15
Q

When do you treat hypotension due to CO and HR? and with what?

“when to treat bradycardia”

A

Concurrent hypotension and bradycardia
Absolute bradycardia
- For example, we have a cat whose heart rate is 30 and its main arterial blood pressure is 65. Then we would treat this
- BUT if we have an animal with a HR of 40 and MAP is 120 (hypertensive) then DONT treat with anticholinergic because even though the HR increases the MAP will too and if its too high that could really be detrimental to the dog

IF dogs good then all of a sudden HR starts dropping rapidly then we treat typically with atropine

Also remember Alpha-2 agonists may cause decreased HR so if theyre bradycardic but hypertensive and you gave an alpha-2 then you can reverse it.

TX: anticholinergics –> atropine and glycopyrollate

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16
Q

What is preload?

A

Stretching of the cardiac myocytes prior to contraction
- Ventricular end diastolic volume or end diastolic pressure
Stretching from increased venous return to the heart
- Venous return
- Decreased venous compliance

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17
Q

If we increase preload how does that affect CO?

A

AN increase in preload aka blood volume leads to increased CO bc the heart stretches more

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18
Q

What are the clinical signs of hypotension caused by preload?

A

Concurrent hypotension and tachycardia (HR increases to try to maintain CO)
Clinical suspicion
- If you give drugs that decrease HR but still hypotensive
- Also foriegn body –> puking and dehydrated, most likely hypotensive and hypovolemic

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19
Q

How do you treat a decrease in preload?

A

Fluid therapy
Decrease intra-thoracic pressure
- Positive pressure ventilation puts positive pressure on thorax
- IN a hypovolemic animal theres not alot of pressure within the vena cava so every time you put a positive pressure in, it collapses the vena cava and there’s decreased venous return.
- So if we have a hypotensive hypovolemic animal, we may not ventilate them as aggressively and that’s decreasing intra-thoracic pressure.

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20
Q

Beta-1 receptors are located in the? and cause?

A

Heart
increased rate & Contractility

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21
Q

Beta-2 receptors are located in the? and cause?

A

systemic vessels
Vasodilation

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22
Q

What is dobutamine and what is it used for? What receptors does it act on?

A
  • Acts on Beta 1&2
  • Positive inotrope –> increased contractility
  • Inodilator–> vasodilation
  • 5-10mcg/kg/min CRI

Indications
- Systolic dysfunction
- Horses–> first line of TX because it increases muscle blood flow and colonic BF, BP, and CO

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23
Q

I have a horse with decreased contractility. What drug should I use?

A

DOBUTAMINE

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24
Q

I have a dog with DCM and decreased contractility. What drug should I use?

A

DOBUTAMINE

EX: Doberman

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25
Q

What is dopamine and what is it used for? What receptors does it act on?

A
  • Alpha 1&2, Beta 1&2, D1&2
  • Dose dependent effects and animal dependent

Positive inotrope
Vasoconstriction

Indications?
- Inotropy and vasoconstriction

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26
Q

Dopamine and D1&2 receptors?

A

mainly for RBF

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27
Q

I dont have dobutamine but i need to increase contractility what can I use?

A

Dopamine

28
Q

What is Ephedrine? Receptors? and What is it used for?

A
  • Alpha 1&2, Beta 1&2
  • Direct effects
  • Indirect effects
    a. Tachyphylaxis –> stimulates the adrenal medulla to release norepi and if you give multiple doses of this then you can diminish all nor-epi stores and get tachyphylaxis
  • Positive inotrope
  • +/- Vasoconstriction
  • Increase uterine blood flow
    a. good for C-sections
  • Crosses BBB
    a. can cause excitation or make plane of anesthesia lighter
  • Single bolus (0.06mg/kg)
  • CRI
29
Q

What is Epinephrine? Receptors? and What is it used for?

A
  • Alpha 1&2, Beta 1&2
  • Positive inotrope
  • Vasoconstriction
  • Increase HR
  • Can give as CRI if about to die and you have no other option

Indications:
- Final line of defense in refractory hypotension
- CPR
- Epinephrine reversal

30
Q

Patient is dying and nothing is working. You have tried dobutamine, ephedrine, and dopamine. What should you use now?

A

EPI STAT

31
Q

How does acepromazine work and how does that affect epinephrine?

A

EPI will bind to alpha and beta receptors

When you have acepromazine in the mix this drug binds so tight to the alpha receptor that it blocks it from other drugs. So if you give epi now you will activate only the beta receptors resulting in tachycardia and vasodilation which only worsens the hypotension.

32
Q

Should you use epi with ace?

A

probably not it can worsen hypotension

33
Q

Do we treat afterload?

A

No

34
Q

How does afterload contribute to hypotension?

A

increased vasoconstriction which increases afterload –> decreases SV and CO

35
Q

What is afterload?

A
  • “Load” that heart has to push against
    a. Increases in systemic vascular resistance
    b. Sub aortic stenosis
  • Increased Afterload = decreases CO
  • Therapy often not aimed at changing afterload

You only treat if theres a pathologic lesion like SAS

36
Q

Describe Systemic vascular resistance.

A

MAP=COSVR
decreased MAP=CO decreased SVR

Vasodilation occurs in this case. Due to which anesthetic agents?
- inhalants esp., also anesthetic agents may be the primary reason we have vasodilation leading to hypotension

37
Q

How do you treat decreased systemic vascular resistance?

A
  • Treatment = vasoconstriction
  • Receptors?
    a. a1&2 agonism
    b. Pure a agonist: Phenylephrine
    c. Mixed receptor aka “dirty” drugs: Dopamine, Norepinephrine, Epinephrine
    d. Other: vasopressin
38
Q

What is our primary alpha agonist?

A

phenylephrine

39
Q

What is phenylephrine? Receptors? and What is it used for?

A
  • Alpha 1&2
  • Vasoconstriction !!VERY strong!!
  • +/- reflex bradycardia –> becasue drug is so potent
  • Small decrease in SV (and potentially CO) due to increase in afterload

Indications:
- Vasodilatory shock
a. like septic patient
- Refractory acepromazine hypotension

We use this ONLY when we want to cause vasoconstriction and only that

40
Q

Do we use phenylephrine in horses?

A

Sometimes but not often bc it decreases muscle blood flow

41
Q

Dopamine increases contractility and?

A

causes vasoconstriction which helps with decreased systemic vascular resistance

42
Q

What is norepinephrine? Receptors? and What is it used for?

A
  • Alpha 1&2, Beta 1&2
  • Vasoconstriction
  • Less tachyarrhythmias than dopamine –> bc not as potent at beta receptors
  • Splanchnic blood flow?
  • It decreases blood flow to ears and fingertips

Indications
- Refractory hypotension
- Vasodilatory shock
a. Sepsis / SIRS

43
Q

What is vasopressin? Receptors? and What is it used for?

A
  • Vasoconstriction
  • Works in acidic environment
  • Beneficial when adrenergic receptors are down regulated
  • Splanchnic blood flow?

Indications
- Refractory hypotension
- Vasodilatory shock
a. Sepsis / SIRS
- CPA

Decompensating shock? give vasopressin because the adrenergic receptors are downregulated

44
Q

What is the clinical approach to hypotension?

A

TX underlying cause
HR? if low increase, if high decrease

Anesthesia induced
- Inhalant vs injectable?
- Duration of procedure?
- Ephedrine
- Dopamine
- Dobutamine

45
Q

Your patient has HCM and is hypotensive what drugs should you use to correct this?

A

Phenylephrine vs dopamine

46
Q

What drugs should you use in vasodilatory shock?

A

Dopamine and norepinephrine

47
Q

What is the most common source of heat loss during anesthesia?

A

radiation

48
Q

You are monitoring an English bulldog during anesthesia recovery and upon extubation, it suddenly goes into cardiac arrest. Which drug would be your first drug of choice?

A

Epinephrine

49
Q

TRUE/FALSE: Hypothermia can result in delayed recovery from anesthesia.

A

True
SO does hypotension, hypoglycemia, drugs, electrolytes, myopathy/neuropathy

50
Q

What is the first step in the management of hypotension in patients under general anesthesia?

A

Check the depth of anesthesia

51
Q

You anesthetize Luna, a 5 year old cat for CT. Your protocol is acepromazine and butorphanol for premedication and induction with ketamine and midazolam and maintained on Sevoflurane. She develops hypoventilation. Which agent is more likely responsible for this complication?

A

Sevoflurane
Volatile inhalants decrease tidal volume first then at higher concentrations respiratory rate

52
Q

In a patient that is in hypoventilation under anesthesia and is becoming hypercarbic, which of the following possible actions you might take to improve breathing is the least likely to help?

A

Increase IV fluid rate

53
Q

A drug that is said to be a positive inotrope will have which of the following effects?

A

Increase cardiac contractility

54
Q

What do the following blood gas results indicate and what corrective action should be taken?

pH= 7.28

PaO2= 380 mmHg

PaCO2= 65 mmHg

HCO3= 24 mEq/dL

A

Respiratory acidosis. Increase ventilator rate and/or tidal volume and monitor blood gas results

55
Q
A
55
Q

You have a horse under injectable anesthesia (ketamine/xylazine) to flush out a tendon sheath. You place a pulse oximeter on the tongue of the horse and obtain a reading of 89%. Which one of the following statements is true?

A

This is an unacceptable reading, since it indicates the PaO2 is < 60 mmHg as this means that the patient is hypoxemic

56
Q

You have anesthetized a young, healthy Labrador for a TPLO procedure. The dog is doing well under anesthesia, although he has been on dopamine to keep his mean blood pressure above 70mmHg. Suddenly, your end-tidal CO2 value drops to 2mmHg. What should you do first?

A

Check for a pulse to assure that patient has not gone into cardiopulmonary arrest

57
Q

What is the best technique for delivering chest compressions in giant breed dogs?

A

Use both hands over the widest portion of the chest in the animal in lateral recumbency

58
Q

TRUE/FALSE: Cardiopulmonary Arrest (CPA) is primarily of cardiac origin in small animal patients.

A

false

59
Q

Hyperventilation during anesthesia could be caused by all of the following except _________.

A

hypothermia

60
Q

Which of the following is a vagally mediated cause of bradycardia during anesthesia?

A

occulocardiac reflex

61
Q

Which combination of parameters should be performed for effective CPR technique?

A

2 minute cycles of chest compressions at 100-120 compressions/minute, ventilation rate of 10 breaths/minute

62
Q

TRUE/FALSE: Chest compressions in CPR should be performed in lateral recumbency in most dogs and cats.

A

True

63
Q

Which of the following is the correct drug of choice to treat premature ventricular contractions (PVCs or VPCs) in dog?

A

Lidocaine

64
Q

What is the recommended external shock dose (in Joules/kg) of a biphasic defibrillator in CPR?

A

2-4 J/kg

65
Q

What is the best technique for delivering chest compressions in giant breed dogs?

A

Use both hands over the widest portion of the chest in the animal in lateral recumbency

Anesthesia (7 decks)

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