My dear BK docs:
The Mobile Stroke Treatment Unit (MSTU) is operational in Brooklyn now.
So it is highly likely that eventually you will receive a patient who has received thrombolysis in the field for a presumed ischemic stroke. They are operational 9a-5pm and are dispatched by FDNY.
They have been active since June, and respond to 2-3 calls a day along a BLS unit. They are dispatched to the scene if the story is concerning for a critical CVA (CVA-C).
They will push t-Pa and start the infusion if after neurologist assessment they meet t-Pa criteria.
The Brooklyn NYU MSTU crew report pushing t-Pa in the field 15 times since beginning operation.
The crew consist of 2 paramedics, a ct technologist, a nurse, and a neurologists who performs a remote assessment using multiple cameras in the back of the unit.
Please understand that the data supporting use of this technology for the benefit of a patient in an urban setting is controversial and not well studied. The data supporting this approach to stroke management in a rural setting is also controversial. But the primary theory is that it will increase the probability that a patient with a significant stroke will initially be transported to a hospital capable of mechanical thrombectomy or other endovascular approaches. Anything deeper is beyond the scope of this pearl of the day.
Now for a quick review of t-Pa, based on a synthesis of NINDS and ECASS:
Indications for t-Pa:
-acute ischemic stroke with onset less than 4.5 hr
-must have NIH stroke scale <25, but with significant deficit, eg aphasia, RUE paralysis, etc. A caveat here is that a patient with a basilar artery occlusion may have a very high stroke score, but they should get t-Pa (and likely mechanical thrombectomy; again too deep of a topic for a pearl of the day).
-No ICH on head CT
Contraindications to t-Pa:
-stroke or ICH in past 3 months
-Severe stroke NIHSS>25; the thought here is a stroke that is greater than 1/3 MCA territory will have high post-ischemic bleeding potential
-surgery within past 14 days (this has to be “major”)
-Systolic BP > 185 (you can control this prior to t-Pa administration)
-history of ICH
-rapidly improving symptoms
-Combination of previous ischemic stroke WITH diabetes
-minimal symptoms (eg paresthesias in the hand)
-GI/GU bleed in past 21 days
-platelet less than 100k
-arterial puncture at non-compressible site last 7 days (eg, subclavian a-line, extremely rare)
-seizure with onset of stroke
-on anticoagulation
Relative contraindications
-age greater than 80 (I moved this from ECASS III absolute contraindications, mostly because of our patient population)
-recent LP
-Recent MI
-glucose less than 40 or greater than 400 because this suggests metabolic; caveat here, if hypoglycemia is corrected need to more strongly consider stroke.
-post MI pericarditis
-Recent MI less than 3 months ago
-if a patient has a history of veno-hepato/renal occlusive disease or TTP and is defibrotide for treatment of any condition, you should consider witholding t-Pa. This drug is though to enhance plasmin activity, thereby helping to prevent clot propagation and promote reabsorption. FYI: you may never see a patient on this drug.
DOSING:
-t-Pa is dosed at 0.9 mg/kg (max 90), give a 10% bolus with the remainder to be infused over 1 hr.
TOXICOLOGY/PHARMACOLOGY
If and when a thrombolysed patient comes from the field into the ED, you need to be prepared from the complications of administration of these agents.
The mechanism of action of alteplase is to “enhance the conversion of plasminogen to plasmin by binding to fibrin, initiating fibrinolysis with limited systemic proteolysis”. This essentially is the “clot-buster"
Hypersensitivity reaction is also possible. So be prepared to give epi IM if signs of anaphylaxis develop.
However, the most significant and common side effect you must monitor for is HEMORRHAGE, give FFP or cryoprecipitate. Give crossmatched blood if bleeding has stabilized and is indicated. Start MTP if is massive. Rate of GI bleed is as high as 5%.
Other clinically significant hemorrhages include ICH (0.4-1.3%). This may result in herniation (very rare).
Another rare complication is cardiac tamponade. If a patient has an ischemic stroke and has a history of cardiac ablation AND is no longer anticoagulated, you should suspect pericardial effusion/tamponade if there are ANY changes in their hemodynamic status.
FINAL CAVEAT: ask the stroke EMS crew for labs if they drew them. They should be drawing them because coagulation studies may become deranged after t-Pa administration.