Læknablaðið : fylgirit - 01.05.2002, Page 35

ABSTRACTS / 33RD SNC & 2ND SCNN
extended pedigrees. Linkage to chromosome 5ql2 was detected,
and the lod score at this locus meets the criteria for genome-wide
significance (multipoint allele sharing lodscore of 4.40, p-value of
3.9 X 10*). By extensive fine-mapping we narrowed down the most
promising region for harbouring a stroke susceptibility gene to a
segment less than 6 cM. We have sequenced this segment and
identified genes in the region. A candidate gene for stroke has been
identified based on association analysis using a dense set of micro-
satellite markers and SNPs, typed for 800 patients and 500 controls.
L 59 - Electrophysiological monitoring
Rosén I
Division of Clinical Neurophysiology, Department of Clinical Neuroscience, Lund
University Hospital.
Continuous EEG monitoring is a relatively new modality in inten-
sive care. Whereas a number of physiological parameters such as
ECG, heart rate, oxygen saturation, blood pressure and tempera-
ture since long have been integrated into ICU monitoring systems,
monitoring of EEG, directly reflecting the functional state of the
brain, has been used more rarely. There are probably a number of
reasons for this.The EEG signal is of low amplitude and often
contaminated by artefacts of biological and non-biological origin.
Interpretation of the EEG requires a long and extensive experience
with due consideration taken to a number of factors such as level of
wakefulness and medication given. It is alrnost impossible for the
attending clinician or nurse to extract useful trends in the develop-
ment of the functional state of the brain during intensive care by
inspecting the ongoing EEG activity only. Even for the professional
EEG interpreter it is very difficult to discern trends of EEG
development during hours and days of intensive care by repeated
inspection of the ongoing raw EEG signal displayed on a time scale,
which is usually in the order of 10-20 sec per page. Furthermore, the
intensive care situation does not permit maintenance of impedance
and position of multiple EEG recording electrodes on the scalp for
any length of time exceeding a few hours.
These considerations have inspired a number of developments
of monitoring devices, which provide simplified time compressed
displays of EEG during intensive care. The two main physical
features of the EEG signal, which are targeted, are, variations in the
amplitude (amplitude integrated EEG, aEEG) and frequency
content (compressed spectral arrays CSA, spectral edge SE).
Recently, digital EEG monitoring systems have been developed
which allow raw EEG to be displayed and stored continuously with
on line trend analysis of aEEG as well as the spectral content of the
EEG signal. This is of special value for identification and moni-
toring of continuously ongoing epileptiform discharges in non-con-
vulsive status epilepticus, which is a common reason for performing
long term monitoring in neurological intensive care.
L60 - Bedside monitoring of cerebral energy metabolism
Stáhl N, Nordström C-H, Ungerstedt U
Department of Neurosurgery Lund University and Department of Physiology and
Pharmacology, Karolinska Institute, Stockholm
technique in neuroscience with well over 7.000 publications. The
first studies of the human brain were published about 10 years ago
and subsequent studies have shown that microdialysis might be a
valuable tool for the supervision of patients during neuro intensive
care.
In 1995, CMA Microdialysis (Stockholm, Sweden) introduced
microdialysis instruments for clinical use (catheters for peripheral
and brain tissue, a microdialysis pump, and a bedside chemical
analyzer). We have used the technique since 1995 as routine in all
patients with severe traumatic brain lesions in the Department of
Neurosurgery, Lund University Hospital. The technique has also
been used in patients with spontaneous subarachnoid or intracere-
bral hematoma, bacterial meningitis, brain tumor, and malignant
infarcts of the middle cerebral artery. Since microdialysis is a
regional technique the positioning of the catheter is essential. The
intracerebral microdialysis catheters now have a radiopaque tip
and they are visible on routine CT scans.
According to our routines an intracerebral microdialysis probe
is inserted into cortical tissue via a separate burr hole when an
intraventricular catheter is introduced for ICP monitoring (“better
position”). During open brain surgery (i.e. evacuation of a focal
brain contusion, hemicraniectomy etc.) one or two microdialysis
probes are introduced into brain tissue close to the injured area
(“worse position”; “biochemical penumbra zone”). In addition one
subcutaneous microdialysis catheter is place in subcutaneous fat
tissue.
The microdialysis probes are perfused (0,3 _l/min) and samples
are collected in microvials every 30 or 60 min for bedside analyses
of glucose, pyruvate, lactate, glutamate and glycerol. The analytes
have been chosen to give information regarding cerebral energy
metabolism and glycolysis (glucose, pyruvate, lactate), excito-
toxicity (glutamate), and degradation of cell membranes (glycerol).
The results of the analyses are shown on a monitor bedside.
Information regarding physiological parameters, ventilation, drug
infusion, blood biochemistry are also included and a new computer
program (ICU-pilot, CMA Microdialysis) allows bedside compa-
rison and evaluation of all modalities. After routine analyses the
microvials are kept frozen for later scientific studies utilizing HPLC
(amino acids, ions, transmitters, drugs).
Table I gives steady state levels of metabolites monitored
bedside in normal human brain and in human brain with manifest
ischemia (cerebral perfusion pressure close to 0). These data are
used as reference values during routine biochemical monitoring in
neuro intensive care (1,2) and microdialysis is presently used to
guide our treatment. The biochemical data have also been used to
evaluate the effect of treatment in a series of 50 patients with severe
brain trauma (3).
In an ongoing study we are comparing physiological and
cerebral biochemical variables in two groups of patients treated for
malignant middle cerebral artery infarcts. From this study we will
present preliminary data comparing the group treated with a
combination of hemicraniectomy, hypothermia and inotropic sup-
port to the second group treated only with hemicraniectomy.
The technique of microdialysis was introduced more than 25 years
ago for monitoring the animal brain and has become a standard
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