accelerate clot lysis to reduce acute pulmonary hypertension & RVF and hopefully prevent death in the acute period
the massive PE death spiral
“PE is notorious for causing patients to go from looking fine to PEA arrest within minutes”1)
massive PE causes increased pulmonary vascular resistance resulting in diastolic RV dilation which causes a rapid decompensation (often with 1-2hrs of onset) as a viscious cycle of impaired cardiac output and hypotension via2):
ventriculum septum to bow into LV resulting in decreased LV filling
RV hypoperfusion and ischaemia
increased RV wall stress and ineffective contraction
iatrogenic iv fluid resuscitation further distending the RV
potential indications for thrombolysis:
PEA cardiac arrest in patient with possible massive PE
probable massive PE defined as:
shock or hypotension (blood pressure <90mmHg, or a systolic blood pressure drop by ≥40mmHg, for ≥15 minutes if not caused by new-onset arrhythmia, hypovolemia or sepsis)
submassive PE and refractory hypoxia
submassive PE in patient with low cardiopulmonary reserve or RV dysfunction (after PE diagnosed and echo done)
patients with acute submassive PE who deteriorate despite anticoagulation
contraindications:
as for usual C/Is to thrombolytics (eg. in thrombolysis in AMI) EXCEPT age is not a factor, and most are relative C/I given the life threatening nature of the indications, although perhaps PH intracranial haemorrhage or active neoplasm, or recent (within 2 months) intracranial surgery or trauma are absolute C/I
pregnancy itself is not a C/I, alteplase does not cross the placenta and risks appear to be similar as for non-pregnant patients
<80kg: give 1.5mg/kg with initial 0.6mg/kg IV bolus over 2 minutes followed by remainder 0.9mg/kg IV infusion over 2 hrs
>80kg: give 50mg IV bolus over 2 minutes followed by 50mg IV infusion over 2hrs
continue CPR until sustained ROSC to a maximum of 60-90min post-thrombolysis
if not in arrest:
<65kg: 1.5mg/kg with 1st 10mg as a bolus and remainder over 2hrs
>65kg: 10mg bolus then 90mg as an infusion over 2 hours
given the cost, if <80mg, use 50mg ampoule and remainder from 10mg ampoules, otherwise use 2 x 50mg ampoules
anticoagulant is also given, preferably at 3hrs AFTER thrombolysis and not before - usually iv heparin
general Mx of massive PE
high flow i/nasal oxygen
avoid iv fluid loading unless US shows CVP lower than expected (eg. small and collapsible IVC), in which case 500mL boluses may be considered, otherwise if no hypovolaemia, consider iv frusemide to reduce RV dilation
inhaled nitric oxide is a potential Rx but not widely available
avoid intubation if possible as patient is likely to crash - preferably delay it until patient's haemodynamics are stabilised, such as after thrombolysis, and in the interim use an LMA if need be as this will be less haemodynamically invasive