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Anesthetic complications Flashcards

(46 cards)

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1
Q

What does a normal resp system look like in values

A

Normal PaO2: 80-110 mmHg (FiO2= 21%)
Saturation of hemoglobin (SpO2): 97-100%
Hypoxemia: PaO2: < 60mmHg, SpO2: <90%
PaO2= 5x FiO2

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2
Q

Causes of hypoxemia and low SpO2

A

Low inspired O2 (FiO2)
Hypoventilation
Diffusion problem (pulmonary disease)
Ventilation perfusion (V/Q) mismatch
Right to Left Shunt

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3
Q

What are the clinical effects of mild hypoxemia

A

SpO2 >80%
Activation of sympathetic nervous system
Increased heart rate, mild hypertension

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4
Q

What are the clinical effects of moderate hypoxemia

A

(SpO2: 60-80%)
Local vasodilatation → hypotension
Reflex increase in heart rate

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5
Q

What are the clinical effects of severe hypoxemia

A

SpO2 < 60%)
Local depressant effects predominate
Rapid decrease in blood pressure → severe hypotension
Bradycardia → ventricular fibrillation or cardiac arrest

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6
Q

What are the consequences of hypoxemia

A

Consequences: Tissue hypoxia, lactic acidosis, organ failure

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7
Q

What patients are at high risk for hypoxemia

A

Brachycephalics
Diaphragmatic hernia
Pneumothorax, pulmonary contusion
Upper airway obstruction
Pneumonia
Abdominal distension (GDV, C-section,…)

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8
Q

How do you reduce your chances of hypoxemia

A

PRE-OXYGENATION prior anesthesia induction
There is no contra -indication to oxygen!

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9
Q

What are the causes of hypoxemia

A

Low inspired O2
Hypoventilation
Ventilation perfusion mismatch and intrapulmonary shunting
- Improve perfusion and ventilation

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10
Q

How can you fix low inspired O2

A

Check O2 supply (O2 tank, flow meter..)
Endotracheal tube: check if tube is properly placed (esophageal, endobronchial)
Check that breathing system is tightly attached to ET-tube
Airway obstruction: Remove or bypass

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11
Q

How do you fix hypoventialtion

A

Check anesthetic depth
Administer O2
Intermittent positive pressure ventilation (IPPV)

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12
Q

What is the definition of hypotension

A

SAP less than 80mmHg
MAP less than 60mmHg
DAP less than 40mmHg

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13
Q

What causes hypotension

A

Mean arterial pressure is driving force for perfusion
MAP < 60mmHg compromised perfusion of visceral organs

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14
Q

Hypotension with SA

A

< 6months have a physiologically lower BP
Geriatric: sub-clinical organ impairment
Hypotension should be treated earlier and more aggressive

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15
Q

Hypotension wiht LA

A

Horse: minimum acceptable MAP 70mmHg (myopathy)
Severe hypotension (with sudden onset) MAP (35-45mmHg)
Requires more aggressive diagnosis and correction

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16
Q

What are the common causes of hypotension

A

Three basic pathophysiological mechanism that lead to hypotension are decreased vascular tone, decreased cardiac output and hypovolemia.

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17
Q

What are the common reasons hypotension happens with peripheral vascular resistance

A

Decrease (vasodilation)
- Inhalant anesthetics, ace
- Sepsis
Increase (vasoconstriction)
- Alpha 2 agonists
- Pain

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18
Q

What are the common reasons preload decreases

A

Hypovolemia
+ pressure ventilation

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19
Q

Why would contractility decrese and cause hypotension

Study These Flashcards
A

Resp/metablic acidosis
Hypoxemia

20
Q

Why would HR decrese and cause hypotension

Study These Flashcards
A

Baroreceptor reponse
Parasympathetic activity

21
Q

Why would HR increase and cause hypotension

Study These Flashcards
A

Baroreceptor response
Pain
Hypoxia
Hypercapnia

22
Q

Hypotension – basic management MAP <60mmHg

Study These Flashcards
A

Check depth of anethesia
Check HR
fluids
Ephedrine
Last resort add a vasopressor

23
Q

how does anesthetic drugs affect BP

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A

Vasodilation: vasomotor center excessively depressed
Decrease vaporizer setting
Administer anesthetic sparing drugs
- Hydromorphone (0.05-0.1mg/kg)
- Butorphanol (0.1-0.4mg/kg)
- Morphine (0.1-0.3mg/kg)
- CRI of fentanyl, ketamine, lidocaine

24
Q

How do you treat HR issues that are causing hypotension

Study These Flashcards
A

-Treat bradycardia (1/2 of resting heart rate)
- Bradycardia can decrease cardiac output
- Slow normal heart rates do not usually affect CO
- Anticholinergics: Atropine, glycopyrrolate

25
What fluids do you give for hypotension
Crystalloid fluids (isotonic balanced) - Fluid bolus: 3 (cats)-5 (dogs) mL/kg over 15min (2-10min if MAP< 40mmHg) - Increases intravascular volume and improves venous return - Repeat once if needed Colloid bolus - Dogs: 2-5mL/kg, cats: 1-5mL/kg over 15 min - If response to crystalloids is inadequate - Maximum dose 20mL/kg/day (dilution of clotting factors, avoid in sepsis) - Pentaspan 6% (60% eliminated in 24 hours) Hypertonic Saline (7.5%) - 4mL/kg over 10 min, duration 30-120 min - Indication: blood loss, need of rapid volume expansion
26
Why would you give ephedrine for hypotension
Synthetic noncatecholamine, stimulates 𝛼1 and 𝛽1 receptors Indirect acting: release of endogenous norepinephrine Vasoconstrictor/venoconstrictor Dose: 0.02-0.05mg/kg IV 50 mg/ml vials (dilute for week) Effects last up to 15 minutes
27
How do you respond to persistent MAP <60 mmHg
Add Positive Inotrope-Dobutamine - Βets 1 agonist (increases myocardial contractility) - Useful for low cardiac output stages in patients with adequate intravascular volume - Used as an infusion (short half life) - 2-15μg/kg/min - Less risk of cardiac arrhythmias - Add 100 mg dobutamine to 500mL 5% dextrose (200mg/mL) - Infuse 0.01–0.07 mL/kg/min
28
What should you do as a last resort when hypotension persists
- Non-catecholamine vasopressor (V1 receptors) - Used for refractory hypotension - Very sick patients or post cardiac arrest
29
What causes Bradycardia
Drugs: alpha 2 agonists, opioids Deep plane anaesthesia Hypothermia Vagal reflexes (oculo-cardiac reflex) Electrolyte imbalance
30
What are common heart arrythmias during ansthesia
Sinus bradycardia Atrioventricular block Sinus arrest Ventricular escape beats Asystole
31
How do you treat cardiac arrhythmias
anticholinergics Atropine: 0.02-0.04mg/kg Glycopyrrolate: 0.01mg/kg Low normal HR – measure arterial BP before initiating treatment Do not confuse ventricular escape rhythms with VPCs
32
How do you treat Ventricular premature complexes
lidocaine bolus 1-2,g/kg +/- CRI is recommended when complexes are multiform, causing hypotension, or occurring in significant runs
33
How do you treat sinus bradycardia with escape beats
atropine or glycopyrrolate. The goal is to increase the HR as the escape beat is due to the slow sinus rate
34
When is a HR considered tachycardic
Heart rate >180 bpm (dog) HR >200 bpm (cat)
35
What causes tachycardia
Sympathetic response to Pain Awareness Hypotension Hypoxemia Hypercapnia Hypovolemia Drug induced? Correct underlying problem!
36
Regurgitation / gastro esophageal reflux (GER) is
Esophagitis, esophageal strictures in dogs/cats if ignored Ruminants (no esophagitis) Regurgitation/GER → aspiration of stomach contents Aspiration of salvia, blood, mucus, GER Bronchoconstriction Hypoxia and cardiac arrest Pneumonia Can be silent (not observed)
37
What are the predisposing factor to GER
Brachycephalic breeds Drugs relaxing lower esophageal sphincter: Volatiles, opioids, anticholinergics, propofol Increased intra-abdominal pressure: Pregnancy, obesity, surgery, head-down position Prolonged anesthesia
38
How do you prevent GER
Appropriate pre-anesthetic fasting Pretreatment with omeprazole, maropitant, metoclopramide Use of cuffed ET-tube
39
How do you treat GER
Secure airway in unconscious patient Check cuff Place suction catheter in esophagus Suction refluxate and lavage with tap water Instillation of 5-30mL Na-Citrate solution Check and suction again prior to extubation Pantoprazole, famotidine
40
What is/clinical signs of hypercapnia
Mild hypercapnia (45-60mmHg) - SNS stimulation: tachycardia, mild hypertension Clinical signs usually seen when PaCO2 > 60 mmHg - Bounding pulses (high systolic, low diastolic) - Vasodilation: brick red color, capillary oozing Severe hypercapnia PaCO2 > 90 mmHg - Severe CNS depression (narcosis) - Respiratory arrest (depression of brainstem)
41
What are the causes of hypercapnia
Hypoventilation Respiratory depressant drugs Positioning (dorsal) Abdominal distension Obesity Equipment failure Uni-directional (one-way) valves (circle systems) CO2 absorber exhausted Inadequate fresh gas flow (non-rebreathing systems) Endobronchial intubation (dogs, cats) V/Q mismatch Apparatus dead-space (overlong ET-tube) Increased CO2 production (hyperthermia
42
How do you prevent hypothermia
Preventing heat loss is easier than treating Insulation Towels, bubble packing Warming mats Circulating warm water Electrical, ‘Hot Dog’ Microwave bags of fluids, bean bags, snuggle safe Warm air blankets ‘Bair Hugger’ Radiant Heat lamps Warm IV fluids/irrigation fluids
43
Potential problems with warming devices
Patient cannot move away from source Radiant heat source Blood flow may not conduct heat away Body pushed into heat source Always observe and monitor temperature Avoid direct contact to patient to avoid burns Use towel for insulation
44
When is hyperthermia common in anesthesia cases
Heavy-coated dogs on circle rebreathing system Post op hyperthermia cats: μ-opioids, ketamine, intraop hypothermia Malignant hyperthermia
45
How do you treat hyperthermia
Turn off supplemental heat, remove blankets, ice packs Water, alcohol to inguinal and axillary regions Fans–careful corneal ulcers Acepromazine?
46

Anesthesia 2 (16 decks)

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