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Anesthesiology 398 and 466 > Lecture 12 Intra-operative Fluid therapy & Peri-Anesthetic Complications Part 2 > Flashcards

Lecture 12 Intra-operative Fluid therapy & Peri-Anesthetic Complications Part 2 Flashcards

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1
Q

What is the 2nd most frequent anesthetic complication?

A

Hypotension

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2
Q
  1. What MAP is hypotension?
  2. SAP?
A
  1. MAP < 60 mmHg
  2. —SAP < 90 mmHg
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3
Q

What is the driving force for blood flow through capillaries?

A

MAP

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4
Q

How do you calculate MAP?

A
  • —MAP = CO x SVR
    • CO = cardiac output
    • SVR = systemic vascular resistance
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5
Q

What are Hypotension Causes because of decreased HR during anesthesia

A
  1. —Drugs:
    • opioids
    • alpha-2 agonists**(not dexmedetomidine)
  2. —Hypothermia
  3. —Physiologic condition
    • —Cardiac/neurologic disease
    • brachycephalic
    • pediatric patients
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6
Q

How do you treat hypotension

A
  • —Anti-cholinergic
    • —Atropine, glycopyrrolate
  • —Underlying cause
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7
Q

What are Hypotension Causes because of decreased Stroke volume (SV) during anesthesia

A
  • —SV depends on preload, contractility, afterload (SVR)
  • —↓preload
    • —↓ blood volume
    • —Vasodilation
    • —IPPV
  • —↓contractility
    • —Anesthetic drugs
    • —Cardiac disease
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8
Q
  1. Decreased preload will do what to blood volume?
  2. How to treat?
A
  1. —↓ blood volume
  2. —Hypovolemia
    • —Goal directed intra-op IV fluid therapy
      • —Crystalloid fluid bolus => 5 – 10ml/kg
      • —Colloid => 2 – 5 ml/kg
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9
Q

Which anesthetic drugs vasodilate leading to decreased preload?

A
  1. —Acepromazine
  2. —Propofol induction
    • —Related to dose & rate of administration
    • —Usually short lived in healthy patients
  3. —Inhalants
    • use ‘inhalant sparing’ techniques
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10
Q

What are 3 ways to do ‘Inhalant sparing’ or ‘Balanced’ anesthesia

A
  1. —Use drugs with mild CV effects
  2. —Nitrous oxide
  3. —Local Anesthesia/Analgesia
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11
Q

What are —drugs with mild CV effects to try and prevent hypotension

A
  • —Mu-agonist Opioids + Benzodiazepines
    • —Hydromorphone, Morphine, Oxymorphone, Methadone, Fentanyl
    • —↓ MAC of inhalant in dose-dependent manner
    • —Minimal CV effects, do not cause vasodilation
      • —May cause bradycardia => treatable
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12
Q

Why use nitrous oxide

A
  • —↓ MAC Sevoflurane by 20-30%
  • —**must scavenge waste gas
  • —50% O2, 50% nitrous
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13
Q

What can —↓contractility

A
  1. —Anesthetic drugs
  2. —Cardiac disease
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14
Q

How do you manage —↓contractility

A
  1. —Drugs with mild CV effects (opioids, benzodiazepines)
  2. —‘Inhalant Sparing’ techniques
  3. —Goal directed IV fluid therapy* Caution with cardiac
  4. —Positive inotropes
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15
Q

What will cause hypotension due to decreased MAP?

A
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16
Q

What can —↓ SVR (vasodilation)

A
  • —↓Vascular tone
    • —Anesthetic drugs
      • —Inhalants, Acepromazin, Propofol
    • —Shock, sepsis
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17
Q

Hypotension Treatment (in order)

A
  1. —Assess/Reduce Anesthetic depth
  2. —Treat bradycardia if associated with hypotension
  3. —IV Fluids
  4. —+inotropes or vasopressors
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18
Q

How do you —Assess/Reduce Anesthetic depth to treat hypotension

A
  • Want to use least amount of inhalent
    • Inhalants cause DOSE DEPENDENT CV depression
      • •↓ contractility, vasodilation
      • •‘Inhalant Sparing’, ‘balanced anesthesia’ techniques
      • •opioids, benzodiazepines, nitrous oxide, local blocks
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19
Q

How do you Treat bradycardia if associated with hypotension

A
  • Anti-cholinergics
    • Make sure to check for underlying cause
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20
Q

Hypotension Treatment with fluids

A
  1. —Crystalloids
  2. —Colliods
    • —Hetastarch
  3. —Hypertonic Saline
  4. —Blood products
    • —Blood loss > 20-30%
    • —Packed RBC
    • —Whole blood
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21
Q

What are the 3 drugs you can use to treat hypotension with positive inotropes and vasopressors

A
  1. Ephedrine
  2. —Dopamine
  3. Dobutamine
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22
Q

How does —Ephedrine work

A
  • —Direct & indirect sympathomimetic
  • —β1>β2 => positive inotropy, ↑contractility
  • —α vasoconstriction
  • —Also causes release of norepinephrine
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23
Q

Is —Ephedrine a long or short term treatment of hypotension

A

—Short-term treatment

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24
Q

what are the different Dopamine dosages and what are the effects (mostly remember effects)

A
  1. —<2.5 ug/kg/min
    • —DA1 & DA2
    • —Vasodilation esp. kidney
  2. —2.5-5 ug/kg/min
    • —β1 agonist, + inotropy
  3. —>5-10 ug/kg/min
    • —α1 & α2
    • —Vasoconstriction, ↑afterload
    • —BP ↑ but ↑ myocaridal work
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25
How does dobutamine work to treat hypotension
* —β1 agonist, ↑contractility, no effect on SVR * —Some β2 & α
26
What lead is used for —dysrhythmia detection
Lead II
27
What is the —Simple systematic approach to detect cardiac dysrhythmias
1. —Identify P, QRS, T waves 2. —Is there a P for every QRS? 3. —Is there a QRST for every P? 4. —Is the R-R interval constant or vary? * —Is there a pattern to variation? 5. —Do complexes come earlier than expected?
28
1. What will sinus bradycardia lead to 2. What are the normal HR for dogs and cats
1. —Low HR, ↓ CO =\> ↓MAP 2. —Normal range * —Dogs 60-120 bpm * —Cats 90-160 bpm
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Sinus Bradycardia Causes
1. —↑ vagal tone =\> Opioids 2. —Hypothermia 3. —Profound hypoxemia 4. —Systemic disease * —Hypothyroid, hypoglycemia, hyperkalemia, cardiac disease 5. —α-2 agonists
30
Sinus Bradycardia treatment
* —Treatment\*if affecting BP: * —Underlying cause * —Anti-cholinergic * —Atropine, glycopyrrolate * —Reversal =\> α2-agonist * —dexmedetomidine
31
1. When do —Alpha-2 agonists (—Dexmedetomine) cause bradycardia 2. Do you treat with anti-cholinergics?
1. —Reflex bradycardia due to vasoconstriction and high - normal BP 2. —\*Do NOT treat with anti-cholinergics
32
What are the consequences of Sinus Tachycardia
1. —↓SV =\> ↓CO, ↓MAP 2. —↑myocardial work/O2 consumption, ↓cardiac perfusion
33
Sinus Tachycardia Causes
1. —Drugs: * —Ketamine - usually short-lived after induction * Anti-cholinergics - esp. if given IV, caution in heart disease, geriatric patients 2. —Pain 3. —Hypovolemia/Anemia 4. —Hypoxia/hypercarbia 5. —Hyperthyroid
34
Sinus Tachycardia Treatment
1. —Underlying cause: * —Drugs: * —Ketamine - usually short-lived after induction * —Anti-cholinergics – wait, usually self-limiting * —Pain =\> * opioids, adjunct analgesics, local blocks * —Hypovolemia/Anemia =\> * fluids, colloids, blood products * —Hypoxia/hypercarbia =\> * intubation, ventilation, IPPV (manual or mechanical) 2. —Beta-blocker =\> * Hyperthyroid + Ketamine =\> sustained tachycardia
35
What is 2 Degree A-V Block (check notes
PR interval is the same, dropped QRS
36
1. 2 Degree A-V Block causes 2. Treatment
1. —Causes: * —↑ vagal tone * —Opioids, brachycephalic breeds * —Other causes of bradycardia 2. —Treatment: * —Anti-cholinergics
37
What is a Ventricular Premature Contractions
* —No P wave with QRS * —R-R interval varies * —R wave wide and bizarre * —Compensatory pause after QRS * —Complex comes BEFORE expected\*\*
38
Ventricular Premature Contractions Causes
1. —Pain 2. —Shock 3. —Traumatic myocarditis – 3 – 5 days post trauma 4. —Hypoxemia, ischemia =\> myocardial, global 5. —Electrolyte, acid/base abnormalities 6. —GDV, pancreatitis, osteosarcoma, splenic hemangiosarcoma 7. —Cardiac disease 8. —Drugs * —Thiopental, digitalis
39
Ventricular Premature Contractions indications to treat
1. —\> 20-30/min 2. —Rate \> 150-180bpm 3. —Hypotension 4. —‘runs’ 5. —Multi-focal 6. —R on T 7. —Bigeminy, trigeminy 8. —Ventricular tachycardia 9. (\> 3 in a row) 10. —Likelihood of progressing to Ventricular fibrillation
40
Ventricular Premature Contractions treatments
* —Lidocaine 2mg/kg, repeat then CRI— * Underlying cause
41
What are the 4 Cardiac Arrest Rhythms
1. —Asystole 2. —Pulseless Electrical Activity 3. —Pulseless Ventricular tachycardia, HR\>180 - 200 4. —Ventricular fibrillation
42
Asystole
43
—Pulseless Electrical Activity
44
—Pulseless Ventricular tachycardia, HR\>180 - 200
45
—Ventricular fibrillation
46
What is the equation for minute ventilation
* MV = TV x f * TV = tidal volume * f = frequency
47
1. As minute ventilation decreases what happens to PaCO2 & EtCO2 2. What is the normal PaCO2 3. At what point is there hypoventilation
1. —PaCO2 & EtCO2 ↑ 2. —Normal PaCO2 35-40 mmHg 3. —\> 45 = hypoventilation 4.
48
Causes of Hypoventilation & Hypoxemia
1. —Anesthetic drugs 2. —Patient factors * —Obesity, Cushings, CNS disease
49
1. —Normal PaO2 2. At 100% O2?
1. —95-100 mmHg room air 2. —Up to 500 on 100% O2
50
Causes of decreased PaO2
1. —Hypoventilation\*\* 2. —low inspired O2 3. —V/Q mismatch 4. —shunt 5. —diffusion abnormality
51
1. Hypoventilation & Hypoxemia is common with all induction agents? 2. Duration/ severity related to what?
1. —Common with all agents 2. —Duration/severity related to dose/rate of administration
52
How do you prevent Hypoventilation & Hypoxemia during Induction
1. —Pre-oxygenation delays onset of hypoxemia * —O2 @ 100ml/kg/min delays onset of hypoxemia to ~5min vs 1 min on room air 2. —Low frequency manual IPPV (hand-bagging)
53
Why do Inhalants cause hypoventilation
* —Dose dependent respiratory depression * —↓ chemoreceptor response to CO2 * —↓ respiratory rate & tidal volume * —↑ PaCO2 =\> ↑ EtCO2
54
How do you manage hypoventilation during anesthesia
1. —Monitor EtCO2 2. —“permissive” hypercarbia * —EtCO2 up to ~60mmHg 3. —Titrate level of anesthetic 4. —IPPV
55
Hypoventilation & Hypoxemia during recovery causes
1. —Too deep =\> turn down gas as nearing end of procedure * —Hypoventilation will cause hypoxemia as patient transitions from 100% O2 to room air 2. —Ventilation/perfusion mismatch, atelectasis 3. —Upper airway obstruction
56
Hypoventilation & Hypoxemia during recovery management
1. —5-10 minutes supplemental O2 2. —Monitor SpO2 @ transition to room air\*\* * —100% to 21% O2 3. —SpO2 \< 93% * —Supplement O2 * —Flow by * —Nasal O2 * —Partial reversal 4. Brachycephalic breeds try and keep endotracheal tube for as long as possible
57
Should you monitor Monitor SpO2 @ transition from 100% O2 to room air?
YES!
58
How can you do a reversal if prolonged oxygen dependence
—Partial reversal if prolonged O2 dependence * —.1ml (1mg) Butorphanol + .9ml NaCl * —Give in .2ml (.2mg) increments
59
Do flashcards for consequences of hypothermia
60
1. What temp is Hypothermia 2. What temp do you see clinical consequences of Hypothermia
1. —Defined as \< 100°F 2. —Clinical consequences @ \< 95°F
61
Hypothermia – Clinical Consequences
1. —Central Nervous System depression * — ↓ MAC * —Confusion ~95⁰F, unconscious ~86⁰F 2. —↓ immune function * —↑post-op infections, metastasis 3. —↓ Metabolic rate * —Prolonged recovery 4. —↑ blood viscosity, hypercoagulability 5. —Conduction velocity slows
62
1. Because —Conduction velocity slows during hypothermia, can you treat with anticholinergics? 2. What are consequences?
1. —Bradycardia non-responsive to anti-cholinergics 2. Consequences: * —Myocardium irritable = ventricular arrhythmias * —hypotension * —Fibrillation ~ 68°F
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Hyperthermia treatment
1. —Remove external heat 2. —Supplement O2 3. —IV fluids 4. —Tranquilizers 5. —Active cooling * —Alcohol, ice, steel table
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Anesthesiology 398 and 466 (22 decks)

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