tPA Calculator – Stroke Dosing

tPA stands for the tissue plasminogen activator - a kind of enzyme present in our blood vessels, responsible for dissolving blood clots and maintaining a liquidity of our blood.

Alteplase is a recombinant, man-made version of this protein (rtPA). To reverse its toxicity effects in case of an emergency, we usually use the alteplase antidote: aminocaproic acid.

How does alteplase and tPA work?

tPA works by triggering the conversion of inactive plasminogen to active plasmin. Plasmin works by dissolving the fibrin clots in our bloodstream - this process is called fibrinolysis.

We usually use the tissue plasminogen activators to treat:

• Stroke (remember - tPA doses for stroke and other diseases are entirely different);
• Heart attack (see: HEART score calculator) 💔;
• Pulmonary embolism (see: Geneva Score calculator);
• Thrombosis of an artificial valve /peripheral artery (see: CHA₂DS₂ VASc calculator);
• Frostbites; and
• Pleural effusion cased by pneumonia.

💡 An enzymeis a kind of active protein that's capable of triggering different chemical reactions in organisms. You may find out more using our enzyme kinetics tool - the Michaelis-Menten equation Calculator.

We can perform tPA administration in a variety of ways:

• Intravenously (IV) - into the vein;
• Intracatheter - into the catheter;
• Intra-hemodialysis catheter - into the hemodialysis catheter;
• Intra-arterial (off-label) - might be used in a case of a frostbite or arterial occlusion; and
• Intrapleural - between the pleurae, membranes that surround lungs and the chest cavity.

We usually administer tPA intravenously - that's the foundation our alteplase calculator is based on.

💡 Recommended dosage: 0.9 mg/kg

Maximum dosage: 90 mg

1. If our patient weights <100 kg: ⬇️

   • During the first 1 minute:
     • IV bolus
     • 10% of recommended dose (0.09 mg/kg)
   • During the next 60 min
     • IV continuous infusion
     • 90% of recommended dose (0.81 mg/kg)

2. If our patient weights ≥100 kg: ⬆️

   • During the first 1 minute:
     • IV bolus
     • 9 mg
   • During the next 60 min
     • IV continuous infusion
     • 81 mg

tPA dosage for stroke should be calculated using the patient's weight. That's why we shouldn't use the tPA dosing charts since they might be not as accurate as we want them to be.

Our alteplase calculator uses the following equation, based on the recommended IV (intravenous) dose:

💡 Maximum dosage allowed: 90 mg

Dosage IV (mg) = 0.9 × Weight (kg),

where:

• Dosage IV is given in milligrams (mg); and
• Weight should be given in kilograms (kg).

tPA calculation example:

Our patient is a male with acute stroke symptoms. He weighs 70 kg.

Dosage IV = 0.9 × 70 kg

Dosage IV = 63 mg

We should administer 63 mg of tPA intravenously. 👍