Noradrenaline Aguettant

An infusion of Norepinephrine should be given into a large vein.

Restoration of Blood Pressure in Acute Hypotensive States

Blood volume depletion should always be corrected as fully as possible before any vasopressor is given. In an emergency, when intraaortic pressures must be maintained to prevent cerebral or coronary artery ischemia, Norepinephrine can be given before and together with blood volume replacement.

Diluent

Norepinephrine should be diluted in 5 percent dextrose injection or 5 percent dextrose and sodium chloride injections. These dextrose containing fluids protect against significant loss of potency due to oxidation. Saline solution alone is not recommended. If whole blood or plasma is needed to increase blood volume, give it separately (for example, with a Y-tube and individual containers if both are given at the same time).

Average Dosage

Add the content of the ampoule (4 mg/4 ml) of Norepinephrine to 1,000 mL of a 5 percent dextrose containing solution. Each ml of this dilution contains 4 mcg of the base of Norepinephrine, and it is given by intravenous infusion. Pass a plastic intravenous catheter through a suitable bore needle, well advanced centrally into the vein, and fix it securely with adhesive tape. If possible, avoid a catheter tie-in technique, as this promotes stasis. An IV drip chamber or other suitable metering device is essential, so that the rate of flow in drops per minute can be estimated accurately.

Start with 2 ml to 3 ml (from 8 mcg to 12 mcg of base) per minute and watch the response. Then adjust the rate of flow to establish and maintain a low normal blood pressure (usually 80 mm Hg to 100 mm Hg systolic), enough to maintain the circulation to vital organs. In patients who were hypertensive before, the blood pressure should be raised no higher than 40 mm Hg below the preexisting systolic pressure. The average maintenance dose ranges from 0.5 ml to 1 ml per minute (from 2 mcg to 4 mcg of base).

High Dosage

In all cases, the dose of Norepinephrine should be titrated according to the patient's response. Occasionally much larger or even enormous daily doses (as high as 68 mg base or 17 ampoules) may be necessary if the patient stays hypotensive. Even so, occult blood volume depletion should always be suspected and corrected when present. Central venous pressure monitoring is usually helpful in detecting and treating this situation.

Fluid Intake

How much the solution is diluted depends on the clinical fluid volume requirements. If large volumes of fluid (dextrose) are needed at a flow rate that would mean an excessive dose of the pressor agent per unit of time, use a solution more dilute than 4 mcg per ml. On the other hand, when large volumes of fluid are clinically undesirable, a concentration greater than 4 mcg per ml may be necessary.

Duration of Therapy

Continue the infusion until adequate blood pressure and tissue perfusion are maintained without therapy. Reduce the infusion gradually and avoid abrupt withdrawal. In some of the reported cases of vascular collapse due to acute myocardial infarction, treatment was required for up to six days.

Adjunctive Treatment in Cardiac Arrest

Norepinephrine infusions are usually given intravenously during cardiac resuscitation, to restore and maintain an adequate blood pressure after an effective heartbeat and ventilation have been established by other means. Its powerful beta-adrenergic stimulating action is also thought to increase the strength and effectiveness of systolic contractions once they occur.

Average Dosage

To maintain systemic blood pressure during the management of cardiac arrest, Norepinephrine is used in the same manner as described under Restoration of Blood Pressure in Acute Hypotensive States. Do not use the solution if its color is pinkish or darker than slightly yellow, or if it contains a precipitate. Avoid contact with iron salts, alkalis, or oxidizing agents.