Shock is a medical emergency associated with a high mortality. The underlying causes of shock such as haemorrhage, sepsis or myocardial insufficient should be corrected. The profound hypotension of shock must be treated promptly to prevent tissue hypoxia and organ failure. Volume replacement is essential to correct the hypovolaemia associated with haemorrhage and sepsis but may be detrimental in cardiogenic shock. Successful correction of hypovolaemia may alleviate hypotension in some cases. However, blood pressure in shock can be extremely low (sometimes a systolic pressure of less than 70 mmHg) and such profound hypotension (despite fluid replacement) and/or the presence of a law cardiac out put will often necessitate additional measures. Sympathomimetic agents are usually employed. They act as presser agents by producing vasoconstriction and also possess positive inotropic activity thus increasing cardiac out put. If hypotension is profound (for example systolic pressure less than 70 mmHg) noradrenaline is usually used; adrenaline or dopamine may be alternatives. If moderate hypotension exists (systolic pressure of about 70 to 100 mmHg) with hypoperfusion, dopamine is usually preferred.
The use of sympathomimetic inotropes and vasoconstrictors should therefore preferably be confined to the intensive care setting and under taken with invasive haemodynamic monitoring.
Adrenaline (Epinephrine)
Injection, 0.1 % in 1 ml ampoule
Indications: correction of hypotension, unresponsive to adequate fluid volume replacement, as part of shock syndrome caused by myocardial infarction, trauma, bacteremia, open-heart surgery, renal failure, chronic cardiac decompensation, drug overdose, or other major systemic illness; also severe anaphylactic shock, severe angioedema, cardiac arrest.
Cautions: - hyperthyroidism, hypertension, diabetes mellitus, ischaemic heart disease, arrhythmias, cerebrovascular disease, and elderly.
Drug interactions: - amitriptyline, atenolol, clomipramine, ether (Anesthetic), halothane, propranolol, timolol.
Contraindications: - asymmetric septal hypertrophy, pheochromacytoma, tachyarrhytmias.
Side effects: - tachycardia and arrhythmia, hypertension, tremor, anxiety, sweating, nausea, vomiting, weakness, dizziness, pulmonary oedema, headache.
Dose and Administration
Note: Different dilutions of epinephrine injection are used for different routes of administration.
Intramuscular or Subcutaneous injection, use 1:1000 epinephrine injection.
Slow intravenous injection; use 1:10000 epinephrine injection.
This route should be reserved for severely ill patient when there is doubt about the adequacy of circulation and absorption from the intramuscular site.
Storage: - at room temperature. Protect from light and freezing.
Dopamine Hydrochloride
Injection, 40 mg/ml in 5 ml ampoule
Indications: - cardiogenic shock in infarction or cardiac surgery.
Cautions: - correct hypovolaemia; low dose in shock due to acute myocardial infarction, correct hypoxia, hypercapnia, and metabolic acidosis before or at some time as starting treatment, history of peripheral vascular disease, elderly; see also interactions.
Contraindications: - tachyarrhythmias, ventricular fibrillation, ischaemic heart disease, Pheochromocytoma; hyperthyroidism.
Drug interactions: - halogenated anaesthetics (such as cyclopropane, halothane); monoamine oxidase inhibitors (the dose of dopamine should be reduced substantially, a suggested starting dose is one tenth of the usual dose).
Side effects: - nausea & vomiting, peripheral vasoconstriction, hypotension with dizziness, fainting, flushing, tachycardia, ectopic beats, palpitations, anginal pain; headache dyspnoea, hypertension, particularly in over dosage.
Dose and Administration
Cardiogenic shock, by intravenous infusion into large vein, Adult initially 2 - 5 micrograms/ Kg/ minutes; gradually increased by 5 - 10 micrograms/Kg/minutes according to blood pressure, cardiac output and urine output; seriously ill patients up to 20 - 50 micrograms/Kg minutes.
Storage - at room temperature protect from freezing.
Phenylephrine Hydrochloride
Injection - 10 mg/ml in 1 ml ampoule
Indications:- treatment of vascular failure, unresponsive to adequate fluid volume replacement, in shock, shock like states, drug induced hypotension, or hypersensitivity.
Cautions: - caution should be taken during late pregnancy and during labour.
Drug interactions: - alpha adrenergic blocking agents such as labetalol; phenoxy benzamine; phentolamine; prazosin, anaesthetics, tricyclic antidepressant, digitalis glycosides, ergotamine, doxapram, methyldopa.
Contraindications: - hypertension, hyperthyroidism or myocardial disease or tachycardia.
Side effects: - chest discomfort, pain, dizziness, nervousness, restlessness, trembling, troubled breathing, unusual paleness, and unusual weakness.
Dose and Administration: - for severe hypotension and shock IV infusion - 10mg in 500ml of 5% Dextrose injection USP or 0.9% sodium chloride injection USP, administered initially at a 0.1 to 0.18mg per minute until blood pressure is stabilized, then at a rate of 0.04 to 0.06mg per minute. If necessary, additional doses in increments of 10mg or more may be added to the infusion solution and the rate of flow adjusted until the desired blood pressure level is obtained.
Storage: - At room temperature and protect from light and freezing.
