(NSTEMI) AND UNSTABLE ANGINA (UA)

DESCRIPTION

Non-ST elevation MI: Chest pain that is increasing in frequency and/or severity, or occurring at rest. The chest pain is associated with elevated cardiac enzymes and ST segment depression or T wave inversion on ECG.

 

Unstable angina pectoris: Chest pain that is increasing in frequency and or severity, or occurring at rest. It also encompasses post-infarct angina. The chest pain may be associated with ST segment depression or T wave inversion on ECG. There is no rise in cardiac enzymes.

 

MEDICINE TREATMENT

If clinically hypoxic:

• Aspirin, oral, 300 mg immediately as a single dose (chewed or dissolved).
  • Followed with 75–150 mg daily.

PLUS

Anticoagulation:

For acute myocardial infarction with no ST elevation:

• Unfractionated heparin, IV bolus, 5 000 units.
  • Follow with 1 000–1 200 units hourly monitored by aPTT. o Continue infusion for 3–5 days.

 

OR

Low molecular weight heparin, e.g.:

• Enoxaparin, SC, 1 mg/kg 12 hourly for two days.

Note:

Thrombolysis is not indicated except if new left bundle branch block (LBBB).  See section 3.2.1: ST elevation myocardial infarction (STEMI).

 

To relieve spasm and pain and to reduce preload:

• Isosorbide dinitrate SL, 5 mg immediately as a single dose.
  • May be repeated at 5-minute intervals for 3 or 4 doses.

 

For persistent pain and if oral therapy is insufficient:

• Glyceryl trinitrate, IV, 5–200 mcg/minute, titrated to response.
  • Start with 5 mcg/minute and increase by 5 mcg/minute every 5 minutes until response or until the rate is 20 mcg/minute. o If no response after 20 mcg/minute increase by 20 mcg/minute every 5 minutes until pain response or drug no longer tolerated.
  • Flush the PVC tube before administering to patient.
  • Monitor blood pressure carefully.

 

Volume of diluent	Glyceryl trinitrate 5mg/mL	Concentration of dilution
250 mL	5 mL (25 mg)	100 mcg/mL
	10 mL (50 mg)	200 mcg/mL
	20 mL (100 mg)	400 mcg/mL
500 mL	10 mL (50 mg)	100 mcg/mL
	20 mL (100 mg)	200 mcg/mL
	40 mL (200 mg)	400 mcg/mL

 

Solution Concentration (mcg/mL)	100 mcg/mL solution	200 mcg/mL solution	400 mcg/mL solution
Dose (mcg/min)	Flow rate (microdrops/min = mL/hour)
5	3	—	—
10	6	3	—
15	9	—	—
20	12	6	3
30	18	9	—
40	24	12	6
60	36	18	9
80	48	24	12
100	60	30	15
120	72	36	18
160	96	48	24
200	–	60	30

 

To relieve pain:

• Morphine, IV, 1–2 mg/minute. o Dilute 10 mg up to 10 mL with sodium chloride 0.9%. o Total maximum dose: 10 mg. o Repeat after 4 hours if necessary. o Pain not responsive to this dose may suggest ongoing unresolved ischaemia.

 

If there is cardiac failure or LV dysfunction:

ACE inhibitor, e.g.:

• Enalapril, oral, 10 mg 12 hourly.