Week 9 One Lung Vent MH

Question 1

The lower lung is known as __________

The upper lung is known as __________

Answer 1

Dependent lung = lower lung

Nondependent lung = upper lung

Question 2

Axillary roll placed on upper chest wall, _____ in the axilla

Answer 2

NOT

Question 3

In the _________ position, the dependent lung is better perfused (gravity) & ventilated

Answer 3

awake & lateral position

Question 4

Upper lung is not ventilated but is still perfusing (although less than dependent lung), this causes a large ________________

Answer 4

right to left intrapulmonary shunt (20-30%)

Question 5

Factors that inhibit hypoxic pulmonary vasoconstriction

Answer 5

Hypocapnia
Vasodilators: nitroglycerin (NTG), nitroprusside (SNP), b-adrenegic agonists (dobutamine), calcium channel blockers
Inhalation agents

Question 6

During apnea: PCO2 increases _____for the first minute and then ______ for each additional minute of apnea

Answer 6

5mmHg

3mmHg

Question 7

Hypoxia during one lung ventilation

Answer 7

FIO2 of 0.8 to 1.0
Check tidal volumes – want 10cc/Kg, suction ETT
Fiberoptic scope to ensure proper ETT placement
Adjust RR to keep PaCO2 at 40mmHg
Add 5cm H2O CPAP to nondependent lung – warn surgeon
Add 5cm H2O PEEP to dependent lung – tx’s atelectasis but may increase vascular resistance
Increase both CPAP and PEEP slowly
Ask surgeon to clamp or ligate nondependent PA
Return to two lung ventilation always an option

Question 8

Double lumen tubes come in

Answer 8

left and right types (most common left)

Question 9

Complications of double lumen tubes include

Answer 9

traumatic laryngitis, hypoxemia due to malpositioned tube, bronchial trauma from over inflation of cuff, inadvertent suturing of tube

Question 10

Left/Right double lumen tube are the most commonly used by far, is easier to place due to anatomic differences in the bronchi

Answer 10

Left

Question 11

MH is a rare inherited myopathy triggered by ___________, leading to an acute hypermetabolic state with a variable presentation

Answer 11

inhaled agents (not N2O) and/or succinylcholine

Question 12

In MH, The __________ (Ca release channel) fails in the sarcoplasmic reticulum leading to decreased Ca reuptake from within the cell (myocyte) causing a 500-fold increase in intracellular Ca, leading to sustained muscle contraction, glycolysis, and heat production. Abnormal excitation-contraction coupling results in prolonged and irreversible muscle contracture.

Answer 12

ryanodine receptor

Question 13

MH triggers are

Answer 13

Succinylcholine (Anectine)
Inhalational agents: halothane, isoflurane, sevoflurane, desflurane, enflurane
Other possible triggers: stress, muscle trauma, exercise, heat stroke

Question 14

MH has an ___________ diagnosis

Answer 14

intraoperative

Question 15

The first sign of MH is

Answer 15

First sign = most sensitive = unexplained tachycardia

Question 16

The most specific sign of MH is

Other signs include

Answer 16

Most specific sign = increasing EtCO2 = hypercapnia, 2-3X

decrease in SaO2 & SpO2, rigidity despite muscle relaxant onboard, dysrhythmias, tachypnea, cyanosis, sweating, unstable BP, mottling of skin, trismus (masseter spasm) after succinylcholine, darkening of blood in surgical field, decreased mixed venous saturation, cola-colored urine, heating and exhaustion of CO2 absorber, hyperthermia (up to 2 degrees C per hour)

Question 17

Labs of MH indicate

Answer 17

Labs: initial metabolic acidosis then a combined metabolic & respiratory acidosis, hyperkalemia, hypercalcemia, hyperphosphatemia, creatinine kinase (CK) > 1000 IU, myoglobinuria, hypoxemia

Question 18

1st step for tx of MH includes

Answer 18

Call for help!

Question 19

Tx of MH is

Answer 19

Dantrolene 2.5 mg/Kg IV as soon as possible then Q5min. until symptoms controlled or up to 10 mg/Kg total, dantrolene must be mixed in sterile water, this is the mainstay of therapy

Continue dantrolene 1 mg/Kg IV Q6hrs for 72 hrs to prevent a recurrence
Calcium channel blockers should not be given while on dantrolene due to life-threatening hyperkalemia and myocardial depression that may occur

Question 20

Dantrolene works by

Answer 20

inhibiting Ca release from the sarcoplasmic reticulum
and
Intracellular dissociation of excitation-contraction coupling

Question 21

Safe drugs in MH patients include

Answer 21

propofol

Question 22

Gold standard pre-op test for MH diagnosis is the

Answer 22

Gold standard preop test = muscle biopsy with halothane-caffeine contracture test

Question 23

Some characteristics of patients with MH include

Answer 23

myopathy, short stature, cryptorchidism (undescended testicles), pectus carinatum (a chest wall deformity), lumbar lordosis and thoracic kyphosis (deformity of the spine), and unusual facial characteristics. Later reports have termed this combinations the King-Denborough syndrome, after the authors of the report.

Question 24

T/F Prior uneventful general anesthetic does not rule out the possibility of MH

Answer 24

True

Question 25

Boys < 9 yrs old who experience sudden cardiac arrest after succinylcholine in the absence of hypoxia should be treated for

Answer 25

acute hyperkalemia first: CaCl2 IV, Bicarbonate IV, they most likely have a subclinical muscular dystrophy

Question 26

The symptoms of MH usually develop within

Answer 26

one hour after exposure to trigger substances, but may even occur several hours later in rare instances.

Question 27

MH does not occur with every exposure to triggering agents, and susceptible patients may undergo

Answer 27

multiple uneventful episodes of anesthesia before developing an episode of MH