Common Intraop Problems

Question 1

Hypoxemia

Answer 1

PaO2

Question 2

V/Q mismatch - hypoxemia

Answer 2

most common pathophysiologic cause of hypoxemia
results from decreased alveolar ventilation in respect to perfusion
ex) shunts, pneumonia, PE, pulmonary edema

Question 3

Improper placement of tube - hypoxemia

Answer 3

endobronchial, esophageal, oropharyngeal

Question 4

oxygen supply - hypoxemia

Answer 4

equipment failure or high altitude

Question 5

alveolar hypoventilation - hypoxemia

Answer 5

COPD, asthma, bronchitis
drug overdose
neuromuscular abnormality (MG, Guillan Barre)

Question 6

Intrapulmonary shunting - hypoxemia

Answer 6

• decreased ventilation in perfused lung regions -> shunting of venous blood without being oxygenated
• O2 therapy unable to improve PaO2

Question 7

Diffusion Abnormality - hypoxemia

Answer 7

impaired transfer of O2
- sarcoidosis, ILD
decreased O2 carrying capacity

Question 8

Bronchospasm

Answer 8

Causes:

• preexisting reactive airway disease
• manipulation of airway
• ETT with inadequate anesthesia
• ETT with bronchial stimulation
• histamine release, anaphylaxis, pulmonary edema

Question 9

Investigations of bronchospasm

Answer 9

examine ETT, check positioning
- look for wheezing
- capnograph
- high peak pressure
RULE OUT: PTX, PE, pulmonary edema

Question 10

Management of Bronchospasm

Answer 10

increase FiO2
increase anesthetic depth
increase expiratory time and decrease RR
give albuterol, epi for anaphylaxis
hydrocortisonefor long term

Question 11

Hypotension

Answer 11

MAP

Question 12

Decreased preload - hypotension

Answer 12

low blood volume (hemorrhage, fluid loss)
decreased venous return -> position
Tamponade, PTX, compression by surgeon, excessive PEEP

Question 13

Decreased afterload - hypotension

Answer 13

sepsis, vasodilating drugs (anesthetics)

anaphylaxis reaction, neuro injury

Question 14

Decreased contractility - hypotension

Answer 14

MI, arrhythmias, CHF, anesthetic effect, electrolyte abnormalities

Question 15

Hypertension

Answer 15

BP > 140/90 or MAP >20-25% from baseline
- examine BP cuff, artline, IV
- review events thus far
- check for hypoxia and hypercarbia
- check anesthetic level
Tx: anti-hypertensives (beta-blockers, vasodilators)

Question 16

Primary HTN

Answer 16

No known cause (70-95%)

Question 17

Secondary HTN

Answer 17

• pain/surgical stimuli (inadequate anesthesia), ETT stimulation
• hypercarbia, hypoxia, hypervolemia, hyperthermia
• intracranial pathology
• endocrine problems
• alcohol withdrawal
• malignant hyperthermia

Question 18

Timing of HTN

Answer 18

prior to induction -> withdrawal from medications
post-induction -> laryngoscopy, ETT stim, improper placement, pain
during case -> pain control, hypercarbia, pneumoperitoneum, fluid overload, bladder distention, drugs

Question 19

Hypercarbia

Answer 19

increased CO2 levels (blood gas or ETCO2)

• examine pulse ox
• vent settings and CO2 absorber
• consider ABG
• assist breathing or increase minute ventilation

Question 20

Increased CO2 production - hypercarbia

Answer 20

malignant hyperthermia
sepsis
fever/shivering
thyrotoxicosis

Question 21

Decreased CO2 elimination - hypercarbia

Answer 21

reduced minute ventilation
increased dead space
drug effects

Question 22

Timing of hypercarbia

Answer 22

Start of case -> ETT placement, vent settings, oversedation
Post-induction -> malignant hyperthermia, vent settings, thyrotoxicosis, CO2 absorber
During Emergence -> inadequate reversal, residual narcotics, hypoglycemia, electrolyte disturbances

Question 23

Hypocarbia

Answer 23

decreased CO2 levels (ABG, ETCO2)
check circuit, check BP, HR, SpO2
check vent settings
Tx underlying cause

Question 24

Causes - hypocarbia

Answer 24

Hyperventilation - decreased metabolic rate

PE, Air embolus, cardiac arrest, ETT problems

Question 25

High peak airway pressures

Answer 25

circuit probelms, ETT problem, drug induced, decreased pulmonary compliance Tx: check tubes, hand ventilate, FiO2 of 100%, auscultate, suction, consider paralysis

Question 26

Oliguria

Answer 26

urine production

Question 27

DDx for oliguria

Answer 27

Prerenal - intravascular fluid depletion Renal - lack of perfusion, renal damage Postrenal - obstruction

Question 28

MI

Answer 28

damage to heart muscle from imbalance of myocardial O2 supply and demand - atherosclerosis, aneurysm, artery spasm, aortic stenosis, blood viscosity, embolus

Question 29

Investigations for MI

Answer 29

``` Lead II - most sensitive for arrhythmia Lead V5 - most sensitive for ischemia detection - together, detect 90% of events ST-depression -> subendocardial ST-elevation -> transmural T-wave inversion and Q-waves check TEE and cardiac enzymes ```

Question 30

Tx for MI intraop

Answer 30

Goal: maintain acceptable balance of O2 supply and demand - maintain BP and 100% FiO2 - confirm placement of leads - notify surgeon - consider reducing anesthetic, beta-blockers - consider fluid therapy, anticoagulation, inotropic agents to support contractility

Question 31

Bradycardia

Answer 31

heart rate anticholinergics unstable -> FiO2 of 100%, abort anesthetic, CPR or pacing Tx: underlying cause

Question 32

DDx of Bradycardia

Answer 32

``` altered pulse formation (vagal tone) drugs (beta-blockers, Ca-blockers, cholinergics, narcotics) pathology (thyroid, sick sinus syndrome) MI surgical/anesthesia stimuli reflex bradycardia ```

Question 33

Tachycardia

Answer 33

``` heart rate > 100 bpm ensure adequate oxygenation and ventilation verify ECG placements assess BP or artline volume status, depth of anesthesia Tx: underlying cause ```

Question 34

Tachycardia and hypertension

Answer 34

``` pain/light anesthesia hypovolemia, hypercapnia, hypoxia Drugs Electrolyte abnormalities MI Endorcrine abnormalities Bladder distention ```

Question 35

Tachycardia and hypotension

Answer 35

anemia, CHF, valvular heart disease PTX, immune stuff MI, sepsis, PE

Question 36

Delayed Emergence

Answer 36

``` check for residual neuromuscular blockade check for hypoxia or hypercarbia check glucose/electrolytes consider narcotic reversal (naloxone) consider benzo reversal (flumazenil) check body temp and neuro status ```

Question 37

DDx for delayed emergence

Answer 37

``` residual drug effects Neuro complications metabolic complications Respiratory failure CV collapse hypothermia sepsis ```