Mon25October0757PM 14

A 65-year-old man is admitted to the coronary care unit following a myocardial infarction. His blood pressure is 72/35 mmHg and pulse rate 82 beats per minute. A 12-lead ECG shows sinus rhythm and changes consistent with an anterior ST-elevation myocardial infarction.

A pulmonary artery catheter is inserted to guide further management. The patient's systemic vascular resistance is 2200 dynes·s·cm-5 and the stroke volume 30 mL.

Which of the following is the single most appropriate initial pharmacological therapy for this patient?

(Please select 1 option)

Adrenaline

Noradrenaline

Enoximone

Digoxin

Dobutamine Correct

Explanation

The patient has developed the haemodynamic derangements associated with cardiogenic shock - systemic hypotension with low cardiac index and high systemic vascular resistance.

The ideal inotrope in these circumstances is most likely to be dobutamine. Dobutamine is a synthetic beta1 and beta2 adrenoreceptor agonist with a lack of alpha effects. It should theoretically lead to direct improvement of stroke volume with further benefit of reduced left and right ventricular afterload.

The phosphodiesterase III inhibitor, enoximone, is an 'inodilator'. Improvements in stroke volume are associated with significant reductions in systemic vascular resistance. A further significant fall in coronary perfusion pressure may exacerbate myocardial oxygen supply. The inodilators are indicated for patients in refractory cardiogenic shock responding poorly to beta-adrenoreceptor agonists.

Digoxin is not very effective as a monotherapy in restoring blood flow in acute cardiogenic shock. Early peripheral vasoconstrictor effect following intravenous administration may be deleterious in some patients leading to acute pulmonary oedema.

Adrenaline and noradrenaline have beta1, beta2 and alpha1 adrenoreceptor agonist activity. Both agents may further raise the systemic vascular resistance, increase myocardial oxygen demand (tachycardia/increased LVEDP) and decreased myocardial oxygen supply (reduced diastolic filling time).

Answer Statistics

1

10%

2

7%

3

19%

4

1%

5

66%

Times answered: 265