Predicting Delayed cerebral ischemia using Micro- and Macrovascular parameters in Subarachnoid hemorrhage patients (PDMMS-study)

An aneurysmal subarachnoid hemorrhage (aSAH) is a severe type of stroke
affecting approximately 7.2-10.5 per 100.000 persons per year in Western
countries, with a mortality ranging from 10 to 50%. Following ictus, aSAH
patients are prone to severe complications like hydrocephalus, cardiopulmonary
dysfunction, rebleeds and delayed cerebral ischemia (DCI). DCI is the leading
cause of morbidity, mortality, prolonged hospitalization and neuropsychological
disturbances in aSAH patients and affects 30% of all aSAH-patients. DCI is
defined as the occurrence of new focal deficits (like hemiparesis, apraxia,
aphasia or neglect) and/or a decrease in GCS score of two or more points
lasting for at least one hour and is suggested after exclusion of other causes
like electrolyte disturbances, infection or hydrocephalus. Immediate damage to
the brain following ictus defined as early brain injury is suggested to set the
stage for DCI. However, the exact underlying mechanisms causing DCI are not
fully understood and are thought to be multifactorial. It has become clear that
vasospasms eg. narrowing of the cerebral arteries, are the not the sole cause
of DCI. Recent studies on DCI following aSAH also suggest a multifactorial
etiology of DCI involving many microvascular abnormalities including
microthrombosis, neuroinflammation and neurovascular uncoupling. The
glycocalyx, a gel-like carbohydrate-rich layer lining the luminal side of the
endothelium could be involved in the pathophysiology of DCI. It is involved in
regulation of inflammation, in regulation of thrombogenesis and in vasomotor
responses through nitric oxide release. This makes the glycocalyx a likely
actor contributing to DCI.

Primary Objective (PHASE 1: feasibility study):
- Determine whether measurements of glycocalyx and other microvascular
parameters using SDF imaging (on the conjunctiva and sublingually) are feasible
in aSAH patients during a period of 2 weeks post-ictus
- Determine whether there are specific patterns in the Doppler signal waveform
in cerebral arteries of aSAH patients during a period of 2 weeks post-ictus

Secondary Objective (PHASE 2: correlation study):
- Determine microvascular parameters including glycocalyx variability, vessel
density, flow velocity, capillary recruitment following aSAH during a two-week
follow-up period and assess possible association with DCI.
- Determine the relationship between inflammatory cytokines measured in
plasma and tear fluid and glycocalyx damage
- Determine the relationship between changes of the sublingual glycocalyx and
changes of the conjunctival glycocalyx using SDF imaging.
- Determine whether changes of the Doppler waveform as obtained with TCD are
related to glycocalyx changes.
- Determine whether changes of Doppler waveform as obtained with TCD are
associated with DCI
- Determine whether glycocalyx variability as seen on SDF imaging coincides
with measured plasma markers of glycocalyx damage

- Determine whether microvascular/macrovascular parameters are related to:
o Findings on initial CT-cerebrum classified using the modified Fisher score
o Treatment modality (endovascular or microsurgical clipping)
o Type, size and location of the aneurysm

- Determine possible relationships between microvascular/macrovascular
parameters and clinical outcomes:
o assess a potential relation between microvascular/macrovascular parameters
and functional outcome expressed with the modified Rankin skore (mRs) score at
six weeks and six months after ictus?
o assess a potential relation between microvascular/macrovascular parameters
and quality of life expressed with the EuroQuol-5D-5 Level (EQ-5D-5L) at six
weeks and six months after ictus?
o assess a potential relation between microvascular/macrovascular parameters
and mortality at six weeks and six months after ictus?

This study is a single-center prospective observational feasibility (PHASE 1)
and correlation (PHASE 2) study, expected to last 24 months.

Setting:
Adult patients admitted to the MUMC+ hospital with a CTA or DSA confirmed
aneurysmal SAH will be assessed for eligibility for participation in this
study. All aSAH patients in the Limburg region are referred to the MUMC+
hospital, as it is the only regional tertiary health care center providing
specialized treatment for intracranial aneurysms. Therefore, no additional
promotion of the research is needed to recruit patients.

Clinical phase:
Following informed consent and assessment of eligibility within 72 hours
following ictus, a patient can be included in this study. Immediately following
inclusion, baseline TCD measurements of the large intracerebral arteries will
be performed. Moreover baseline measurement of the sublingual and conjunctival
microvasculature including its glycocalyx will be performed using SDF imaging.
Tear fluid will be collected and blood samples will be taken to measure markers
of glycocalyx disruption and inflammatory cytokines/enzymes. Moreover, in
patient with an external ventricular drain (EVD), cerebrospinal fluid (CSF)
will be sampled from the reservoir. All these measurements will take place at
the patient*s bedside. In the same week of inclusion, two additional TCD
measurements, conjunctival and sublingual measurements, tear fluid collection,
CSF samples and plasma marker/cytokine samples will take place with one or two
days in between. Likewise, in the second week, TCD measurement and SDF imaging
will be performed, CSF, tear fluid and blood will be taken for inflammatory
markers three times per week. DCI usually presents around three to four days
after ictus, with a peak at seven to ten days; therefore a fourteen day
follow-up allow us to capture most of DCI events. During a DCI period (new
focal deficits, decrease in GCS score > 2 after exclusion of other causes), SDF
imaging, TCD measurements, tear fluid collection, CSF samples and blood samples
for plasma markers/cytokines will be performed daily until DCI resolves. The
measurements are performed as soon as possible and within 24 hours of the first
symptoms, while symptoms are still present. Thereafter, all measurements will
be performed three times per week.
Measurement of the glycocalyx using SDF imaging will take around five minutes
per location maximum. In our experience, these measurements are easily
tolerated by patients; this has also been confirmed by several studies using
this technique for both the sublingual and conjunctival microcirculation.
Patient experience with the measurements using SDF imaging sublingually and
conjunctivally will be reported using a five-point Likert scale (if the patient
is conscious) at the end of each week. Measurements will be performed in the
early morning before breakfast after a period of at least six hours of fasting
to reduce the effects of glucose on the glycocalyx.
Tear fluid collection is performed via Schirmer's paper strips, inserted at the
junction of the middle and lateral thirds of the lower eyelid.
TCD measurements last up to 15 minutes per measurements and do not have any
side effects. Measurements are painless and performed at the patient*s bedside.
Finally, blood samples are routine procedures in aSAH patients and take about
1-3 minutes.

Outpatient follow-up phase:
In order to assess the relationship between microvascular parameters and
clinical outcome, we will include two assessment tools at the usual outpatient
follow-up moments, i.e. at six weeks and six months post-ictus. Firstly, the
functional outcome will be measured using mRS based on a structured interview.
The mRS explores patient mobility, autonomy, activities and symptoms resulting
from the aSAH. It is expressed using an ordinal seven-point scale, with 0
representing no residual symptoms, 5 severe disability and 6 death. The mRS is
part of the national quality registry of aSAH patients (QRNS), and is therefore
part of standard patient care. Secondly, quality of life will be measured using
the EQ-5D-5L questionnaire, which explores mobility, self-care, usual
activities, pain/discomfort and anxiety/depression. Completion of the interview
and questionnaire will take around 10 - 15 minutes. In case a patient cannot
complete this interview and questionnaire him/herself, a proxy will be asked
for help. In this case, the intent is that the answers given represent the
opinion or experience of the patient.

Participation in this study means patients will be subject to a few different
kinds of measurements to better understand the nature of the micro- and
macrovascular changes following an aSAH.

The glycocalyx measurements using SDF-camera are safe, quick, bed-side and
minimally invasive measurements lasting no more than 5 minutes per measurement.
The LED light emitted by the camera is not harmful for the tissues that are
being investigated (sublingual and conjunctival tissues). Patients might
experience slight discomfort with conjunctival measurements due to the
placement of the probe on the conjunctiva, however this should not cause damage
to the cornea if performed well. Patients will have a minimum of 6 measurements
per area of interest, more if they develop DCI.

Tear fluid collection is a safe, minimally invasive and painless procedure that
is well tolerated by patients. The procedure lasts no longer than 5 minutes.

TCD's are routine bedside diagnostic measurements in aSAH patients and
therefore do not represent an additional burden for the patient. These
measurements are safe, painless, and last up to 25 minutes per measurement.
Likewise these measurements will be done at least 6 times, more in the presence
of DCI.

Blood samples are easy to obtain in aSAH patients considering the treatment
they already get (all patients with an aSAH are hospitalized for three weeks
and get intravenous therapy). We consider 5mL blood per sample to be marginal.
Patients will not need to be punctured for each blood sample, rather blood will
be withdrawn from their venous line, limiting harm and discomfort.

CSF sampling is safe, easy and quick. The patient does not feel the sampling as
it happens distally in the reservoir of the external ventricular drain.

Finally, filling in a form on quality of life at six weeks and six months after
ictus (EQ-5D-5L questionnaire) will be done at the routine outpatient clinic
visits. This questionnaire is easy to fill in and takes no longer than 10
minutes. Questions are clear and to the point, therefore do not require a
particular level of acuity/intellect.

These measurements will provide us with valuable information on a disease that
is until today not well understood and that causes increased mortality in
middle-aged people. We believe that the benefit of the obtained data outweighs
the burden for the patient, as the results of these measurements could provide
us with new tools to better predict DCI and therefore limit the DCI-induced
damage to the patient.