Nitroglycerin - SBP drop by one third. Is this a 1/3 drop directly after a dose of nitroglycerin or a cumulative drop after multiple doses/sprays? 

My understanding was that this 1/3 drop in SBP was being used to determine the pts sensitivity to nitroglycerin. If the pt had mild/moderate SBP drops after each dose it indicated that the pt tolerated nitro well and it was safe to give higher amounts and more doses. However, a large 1/3 drop immediately after a dose of nitro meant that the pt had a high sensitivity to nitro and further tx should be discontinued for pt safety and impending hypotension. 

Scenario: Ischemic chest pain (Non-STEMI) with an initial SBP of 180mmHg. 1/3 dictates a drop of 60mmHg. After 4 sprays of nitro (with mild SBP drops between each dose) the pts SBP is now 115mmHg. 

Is this pt exempt from further nitroglycerin because cumulatively their SBP dropped by more than 1/3 OR can I continue to treat because a large 1/3 drop was not seen following an isolated spray of nitro. 

This is an astute question. SWORBHP Medical Council would accept administering nitroglycerine, should the patient still be having discomfort in the setting of suspected cardiac ischemia, as long as the SBP does not drop more than 1/3 of the last SBP prior to that dose of nitroglycerine given. Despite this, note that the Condition of SBP Normotension still applies. 

Cardiac Ischemia,Cardiac/Circulation

Cardiac Ischemia, Condition, Contraindication, Dosing, Nitro, Nitroglycerine, SBP

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