Victorian neurologists identify strategy to shorten time to antithrombotics in stroke

By Sunalie Silva

1 Jul 2021

Neurologists in Melbourne have identified a strategy to shorten time to antithrombotic administration in ischaemic stroke – a target that they say is a neglected aspect of acute stroke care in Australia.

While national audits show that 64% of patients in Australia receive antithrombotics within the recommended 48 hours, that figure falls well below international guideline minimum thresholds of 85% and the 97% frequency achieved in other countries.

“The components of stroke unit care which have received most attention include swallowing assessment, fever and sugar management. Surprisingly, there has been less attention on timely administration of antiplatelet therapy,” according to clinicians from the Department of Neurology at Monash Health, who say Australian data on target rates are not of the ‘high standard’ set by North American hospitals.

Auditing data from their own hospital, the team looked at factors related to time to antithrombotic therapy in 525 patients admitted to the stroke unit at Monash Health over a 12-month period in 2015. Some 42 patients had TIA while 483 had ischaemic stroke.

A review of admission diagnoses, time to triage, imaging, information on dysphagia screen and nil by mouth (NBM) status, revealed that TIA patients received antithrombotics earlier than those with stroke – a finding that could be linked to the presence of dysphagia in patients with ischaemic stroke.

Noting a 38% lower dysphagia frequency screen among patients with TIA, investigators suggested the observation might be a factor contributing to the shorter time to antithrombotics in that group.

The hospital, like most others across Victoria, uses the Acute Screening of Swallow in Stroke or TIA (ASSIST) tool for dysphagia screening of patients. It’s a highly sensitive tool and the presence of facial weakness would result in a patient being deemed to have failed the dysphagia screen – an outcome that would affect when – and how – patients are administered anti clotting agents.

“In our institution, patients who have failed this screening test are required to be assessed by a qualified speech therapist. Due to this potential for delayed therapy, 16% of patients were given aspirin by rectal method; five of these patients were classified as having a minor stroke.”

Alternative routes

While various guidelines including NICE, have recommended the use of rectal administration of aspirin or via nasogastric tube in patients with dysphagia, lead investigator Dr Thanh Phan and colleagues say an alternative route not yet explored is the use of intravenous or chewable aspirin.

Perhaps offering a more comfortable approach than rectal administration, chewable aspirin can disperse in the mouth without water and and is more cost effective with the chewable medication costing just $0.15 per tablet compared to rectal aspirin at $5.30 and intravenous aspirin at $20.00 per dose.

Other antiplatelet agents (clopidogrel, combined aspirin and clopidogrel, or aspirin and dipyridamole), which can’t be given by rectal or intravenous route, may require administration via a nasogastric tube if appropriate, or else experience delay in therapy until dysphagia improves, they add.

But perhaps the most significant strategy shortening time to antithrombotics is the the use of stat dosing, rather than charting these therapies at routine times.

The strategy refers to one-off immediate dosing of medication and was used in 49.3% of study patients and given as charted in 86.1% of cases, which meant that patients admitted at 9am, for instance, had to wait nearly 23 hours to receive the medications, which are usually administered for charting at 8am, say investigators.

Based on significant difference (p < 0.01) in the proportion of patients receiving aspirin (89.1%) vs. other antithrombotics (60.5%), investigators recommend charting of “stat” dose of aspirin in addition to routine charting.

Meanwhile, the delay between alteplase administration and the post-alteplase scan was also flagged as a factor exacerbating delays to antithrombotics.

While very early administration of intravenous aspirin has a >3-fold increase risk of intracranial haemorrhage  Dr Thanh said recent audits suggest that the 24-h CT scan can be omitted in stable patients or those with low stroke severity.

He suggests one approach is to perform the post-alteplase CT scan to during office hours for these patients and then give aspirin at the 24-h mark.

“Only a small fraction (11.4%) of our patients had this important scan performed during office hours (7 a.m. to 5 p.m.). The 7.5-h delay between the post-alteplase scan and antithrombotic administration might reflect the delay in assessing the scan and issuing the order for giving antithrombotics. Less commonly, the finding of intracranial haemorrhage, either as a complication of thrombolysis or as hemorrhagic transformation into the ischaemic lesion, may result in consideration of further delay in commencement of secondary prevention,” he noted.

By drawing attention to this ‘neglected’ area of acute stroke care the investigators say they hope it will improve  the time to antithrombotic therapy, and ultimately, clinical outcomes.

The study is published in Frontiers in Neurology.

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