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Page 4 of 12 Zhao et al. Vessel Plus 2021;5:10 I http://dx.doi.org/10.20517/2574-1209.2020.77

Benefits for thrombolysis
The most prominent feature of MSUs is the ability to provide faster pre-hospital thrombolysis. After the
first 365 days of operation, a total of 100 patients had received pre-hospital thrombolysis. Time from
dispatch of first ambulance to commencement of reperfusion therapy was compared between MSU and
a similar cohort of patients in metropolitan Melbourne presenting via regular ambulance to hospital
[2]
during MSU operating hours . Overall results show time to treatment was substantially cut by 42.5 min
(95%CI: 36.0-49.0). Not surprisingly, the major contributor was avoidance of need to transport to hospital
prior to thrombolysis (median dispatch time to scene arrival and hospital arrival was 22.5 min and 49
min, respectively), but the efficient workflows of the MSU upon arrival was also faster than transport to a
thrombolysis center (median time from scene arrival and hospital arrival to treatment was 41.5 min and
57.0 min, respectively). Therefore, in almost all scenarios, the Melbourne MSU would likely provide faster
treatment so long as the service could physically reach the patient prior to hospital arrival and there were
no clear difficulties in performing CT scanning or provision of thrombolysis.

Compared to international services, the Melbourne MSU has a somewhat longer time than other busy
[2]
metropolitan units for some metrics, such as dispatch and scene arrival to thrombolysis . Part of this may
be due to the higher complexity of cases, as around one-third of patients receiving thrombolysis on the
Melbourne service also have large vessel occlusion, therefore making extrication slower. The Melbourne
MSU also has a more difficult stretcher loading and positioning process to minimize manual lifting, which
takes more time than similar international services. Furthermore, comparison may also be confounded if
different services have varying thresholds as to selection of attended patients for MSU management (e.g.,
if only straight-forward patients are selected for scanning). Despite this, the overall time savings for both
onset and dispatch to thrombolysis (compared to local controls) were greater for the Melbourne MSU
than for other international services. This suggests that significant on-scene difficulties are faced by regular
ambulance transport pathways and the extra staffing of the MSU may ultimately assist with extrication
processes.

Another key metric of interest was the ability of the Melbourne MSU to provide very early thrombolysis.
Experiences from international MSUs have shown substantial increases in the proportion of patients able
to receive thrombolysis within the first hour of known onset, or the “golden hour”, compared to usual
hospital pathways [9,10] . The Melbourne MSU was able to provide golden hour thrombolysis for around 15%
[2]
of all treated patients, compared to just 1.5% in the local control group, indicating a ten-fold increase . The
largest reported cohort from the Berlin MSU initially reported increase in golden hour thrombolysis from
[11]
5% to 31% , but more recent updates show the figure at 13% and much closer to the Melbourne service.
[9]
Three US-based MSUs also reported golden hour thrombolysis between 27%-33% [12-14] but all with very
small patient numbers (< 20). The proportion of non-MSU patients receiving golden hour thrombolysis
[15]
in-hospital was reported as 1.3% in a very large US treatment cohort (n = 65,384 patients) , which is also
very close to that of metropolitan Melbourne.

Finally, the Melbourne MSU is also able to administer supportive medications more efficiently. This
includes anti-hypertensive agents pre- and post-thrombolysis, or intravenous idarucizumab to reverse
[16]
dabigatran prior to thrombolysis . This is because the medications are always kept in a known location on
the vehicle, compared to sourcing the drug in a large emergency department or pharmacy department (and
may require pre-approval from another specialty). MSU personnel are also especially trained to administer
these medications efficiently, whereas in-hospital such drugs may need to be given by a general emergency
nurse with less experience.