Sun10October1036AM 8

A 54-year-old man presents to the Emergency department with a two-hour history of chest pain. The pain is described as "tightness" and is principally located in the centre of his chest and radiates into his neck and left arm.

He is normally fit and well.

Immediately following admission he suffers a VF cardiac arrest and is promptly defibrillated with return of spontaneous circulation (ROSC).

On examination he is anxious, cold and "clammy". His blood pressure is 82/45 mmHg, heart rate 120 beats per minute. Oxygen saturation on air is 95%. The heart sounds are normal and there is no evidence of pulmonary oedema.

A 12 lead ECG shows a sinus rhythm of 120 with ST segment depression and T wave inversion in leads II, III, and aVF.

Which one of the following options is the most appropriate initial treatment in this patient?

(Please select 1 option)

Oral aspirin Correct

Intravenous glyceryl trinitrate

Intravenous metoprolol

Intravenous morphine

Inhaled high flow oxygen

Explanation

As soon as the diagnosis of unstable angina or NSTEMI is made, and aspirin and antithrombin therapy have been offered, formally assess individual risk of future adverse cardiovascular events using an established risk scoring system that predicts six month mortality (for example, Global Registry of Acute Cardiac Events [GRACE]).

Consider intravenous eptifibatide or tirofiban as part of the early management for patients who have an intermediate or higher risk of adverse cardiovascular events (predicted six month mortality above 3.0%), and who are scheduled to undergo angiography within 96 hours of hospital admission.

Beta-blockers are known to reduce mortality from acute myocardial infarction by reducing oxygen demand. Evidence of their use in unstable angina suggests a 13% reduction in the risk of developing myocardial infarction. Beta-blockers should be given early in the absence of contraindications (heart block, bradycardia, hypotension, severe left ventricular dysfunction and asthma). This patient has hypotension and therefore metoprolol would be contraindicated.

If the symptoms are not relieved by three doses of nitroglycerine tablets or nitrolingual sprays plus intravenous beta blockers, intravenous GTN should be considered but only if there is no hypotension. This patient is hypotensive and it is contraindicated.

Morphine sulphate is indicated for patients whose symptoms are not relieved after three serial doses of nitroglycerine or whose symptoms recur despite adequate anti-anginal treatment.

The potential harm caused by hyperoxaemia after ROSC is achieved is now recognised: once ROSC has been established and the oxygen saturation of arterial blood (SaO2) can be monitored reliably (by pulse oximetry and/or arterial blood gas analysis), inspired oxygen is titrated to achieve a SaO2 of 94-98%. Supplementary oxygen is routinely administered to patients, even those with adequate oxygen saturations, in the belief that it increases oxygen delivery. But oxygen delivery depends not just on arterial oxygen content but also on perfusion. It is now widely recognised that hyperoxia causes vasoconstriction, either directly or through hyperoxia-induced hypocapnia.

If perfusion decreases more than arterial oxygen content increases during hyperoxia, then regional oxygen delivery decreases. This mechanism, and not (just) that attributed to reactive oxygen species, is likely to contribute to the worse outcomes in patients given high-concentration oxygen in the treatment of myocardial infarction and postcardiac arrest.

Reference:

NICE. Unstable angina and NSTEMI (CG94).

Answer Statistics

1

69%

2

5%

3

5%

4

16%

5

7%

Times answered: 276