Cardiac

Question 1

Resting membrane potential

Answer 1

-90

Primarily regulated by K+

Hypokalemia decreases RMP

Hyperkalemia raises RMP

Question 2

Threshold potential

Answer 2

-70 mV

primarly regulated by calcium

Hypocalcemia decreases TP

Hypercalcemia increases TP

Question 3

Cardiac myocytes contain _____ _______ than skeletal muscle cells

Answer 3

More mitochondria

Question 4

What serves as low resistance pathways in cardiac myocyte?

Answer 4

Tight junctions (also called gap junctions or nexi)

Question 5

RMP established by what mechanisms?

Answer 5

• Chemical force
• Electrostatic counterforce
• Na/K ATPase

Question 6

Na/K pump is an ______ ______ ______ that requires energy in the form of ATP

Answer 6

Active transport mechanism

Question 7

Note Absolute refractory vs Relative refractory period

Answer 7

Absolute:

• From 1 to halfway through 3
• Longest in phase 2
• about 0 mV in phase 2

Question 8

Current that is primary determinant of pacemakers intrinsic rate?

Answer 8

• I-f (funny current)
• Sets rate of spont. phase 4 depolarization in SA node

Question 9

Rates of cardiac nodes

Answer 9

• SA 70-80
• AV 40-60
• Purkinjes Fibers 15-40

Question 10

Nornal mL/min values for 70kg adult:

CaO2

DO2

VO2

CvO2

Answer 10

• CaO2 - 20
• DO2 - 1000
• VO2 - 250
• CvO2 - 15

Question 11

Frank starling mechanism relates?

Examples?

Answer 11

ventricular volume to ventricular output

Question 12

Functional unit of contractile tissue in heart?

Answer 12

Sarcomere

Question 13

Decreases contractility

Answer 13

• ischemia
• hypoxia
• acidosis
• hypercapnia
• hyperkalemia
• hypocalcemia
• volatile anesthetics
• propofol
• B.blockers
• CCB

Question 14

Initiates myocardial contraction?

initiates relaxation?

Answer 14

• Calcium binds to troponin C
• Unbinds

Question 15

Role of calsequestrin?

Answer 15

• Binds to calcium inside Sarcoplasmic reticulum for storage
• think “sequesters calcium”

Question 16

What areas of heart are supplied by what coronary arteries?

(Picture)

Answer 16

Question 17

Identify valvular disorders

Answer 17

Question 18

Best > Worst leads for intraoperative ST changes?

With CAD?

Answer 18

V3 > V4 > V5 > III > aVF

CAD: V3 > aVF > MCL5 or III

Note: Lead II is good for dysrhythmias with narrow QRS where P analysis is critical - junctional, a-flutter, a-fib

Question 19

CCBs that impair contractility from highest to lowest

Answer 19

V-Nif-D-Nic

Verapamil > Nifedipine > diltiazem > Nicardipine

Question 20

CCB thats useful coronary antispasmotic?

Answer 20

Nicardipine

Question 21

Only CCB proven to reduce M&M from cerebral vasospasm?

Answer 21

Nimodipine

Question 22

Period of highest awareness during CPB?

Answer 22

Sternotomy

(second is rewarming)

Question 23

protamine dosing

Answer 23

1 mg per 100 units of heparin

Question 24

Clamping distal tissue results in:

Answer 24

• ^ lactic acid –> metabolic acidosis
• ^ prostaglandins
• ^ activated compliment
• ^ myocardial depressant factors
• v Tempurature

Question 25

After clamp removal:

Answer 25

Decreased: * Preload * SVR * DBP * CO * Sv02 Increased: * PAOP * PAP * PVR

Question 26

Thoracic cross clamp times greater than ____ pose significant risk for cord ischemia

Answer 26

30 minutes

Question 27

Spinal cord protection strategies?

Answer 27

* Moderate hypothermia * CSF drainage * Proximal HTN during Xclamp * Avoid Hyperglycemia * SSEP/MEP monitor (SSEP only posterior cord - sensory) * Partial CPB * Drugs - corticosteroids, CCBs, Mannitol