Part One Revision

Question 1

What is the alveolar gas equation?

Answer 1

PAO2 = alveolar partial pressure oxygen
PI02 = partial pressure of inspired oxygen
PACO2 = alveolar partial pressure of oxygen
R = respiratory quotient (R = 0.8 typically)

Question 2

Ratio of carbon dioxide transported in the blood by various mechanisms?

Answer 2

Dissolved = 5-10%
Bicarb buffer = 95%
Carbamino complex = 5%

Question 3

How does digoxin work?

Answer 3

Blocks Na/K ATPase to increase intracellular levels of sodium which causes more calcium to be transported into cells thereby increasing contractility. Slow heart rate -> increased filling

Question 4

What class of antiarrythmic is amiodarone?

Answer 4

Class 3 (but also has 1,2,4 properties)

Question 4

How does tPA work?

Answer 4

tPA activates plasminogen already bound to fibrin, to form plasmin. Plasmin degrades fibrin to fibrin split products. This theoretically confines fibrinolysis to formed thrombus. Short half life means heparin is an essential adjunct

Question 5

Which drugs does adenosine interact with

Answer 5

Theophylline (adenosine receptor blocker), Dipyrimadole (adenosine receptor blocker), other AVN blocking drugs

Question 6

How does clopiodgrel work?

Answer 6

ADP receptor blocker. Blocks ADP receptor which activates platelets and cross links fibrin

Question 7

Other than clopidogrel, what type of antiplatelet medications are there?

Answer 7

IIb/IIIa inhibitors (abciximab), dypyridamole (phosphodiesterase inhibitor)

Question 8

What features distinguish lignocaine from other Class 1 antiarrythmics?

Answer 8

Does not prolong the duration of the AP
Dissociates from the channel with rapid kinetics
Has no effect on normal cells

Question 9

How does heparin act?

Answer 9

Heparin binds endogenous antithrombin and enhances its activity. Antithrombin inhibits factors IIa, IXa and Xa by complexing with them and inducing a conformational change