The aPTT is not very quantitative but can determine the presence or absence of drug effect. A normal value indicates absence of effect; a value greater than 2.5 x control 8-12 hours post dose indicates excess. The TT is also discussed in the article but is not in everyday clinical use.
Pradaxa need not be stopped for dental work, skin biopsy or cataract extraction but such procedures should ideally take place greater than 10 hours post dose.
For more invasive procedures it's a little more complicated:
For procedures associated with a moderate risk of bleeding, dabigatran should be held for 2 to 3 half-lives, whereas it should be held for 4 to 5 half-lives before procedures associated with a high risk of bleeding. Examples of procedures with a moderate risk of bleeding include pacemaker or implantable cardioverter-defibrillator implantation and colonoscopic resection of polyps, particularly those that are sessile and have a broad base. Procedures associated with a high risk of bleeding include urologic procedures, such as transurethral prostate resection, major abdominal or pelvic surgery for cancer, joint replacement surgery, cardiac surgery, and neurosurgery.
Here is an algorithm.
If urgent surgery or intervention is required, the risk of bleeding must be weighed against the clinical need for the procedure. Ideally, surgery should be delayed for at least 1 half-life after the last dose of dabigatran or until the aPTT is normal or near normal. If the procedure is performed 2 to 4 hours after the last dose of dabigatran, the risk of bleeding is increased and strategies to reduce bleeding may be required.
Post procedure it can be restarted as soon as hemostasis is secured and bleeding risk is believed to be low, keeping in mind that unlike the case with warfarin the resumption of anticoagulant effect will be almost immediate.
The bleeding patient:
There is NO antidote although a neutralizing antibody is being developed (analogous to digibind?).
So you stop the drug, calculate the patient's creatinine clearance and, knowing that it has first order elimination kinetics you can do the math. For more severe, life threatening bleeding (e.g. head bleeds) that is not enough. It is removed pretty well by hemodialysis. Although there is no specific antidote currently available there has been talk of using 4 factor PCC (not available in the US), 3 factor PCC supplemented with a little recombinant activated factor VII or factor VIII inhibitor bypassing activity. Those remedies are mentioned in the review. The evidence to support their use is slim but an algorithm is presented.
The full text of the review is available at the link above.