Heparin is an anticoagulant medication, used to inhibit the formation of thrombi that pose arteriolar and vein-occlusive risk. The choice between starting a heparin infusion with or without an initial bolus is case dependent based on whether a patient is already anticoagulated and if so, foregoing an initial bolus. In contrast, both anticoagulated and non-anticoagulated patients share the same goal when receiving Heparin for various thromboembolic syndromes, and that is to be within aPTT target range of 1.5-2.5 or 45 to 75 seconds. Falling below goal range leads to a 20-25% recurrence of VTE, and aPTT above goal range has been shown to increase the probability of major bleeding by roughly 7% for every 10 second increase in aPTT1,5. The bolus dose has been shown to achieve therapeutic range faster than without the bolus, however this is often accompanied by overshooting the therapeutic range and necessity of titrating down on the subsequent infusion
