Biology Reference
In-Depth Information
cannula. This access is used to monitor systemic blood pressure
and also to withdraw blood for arterial gases. A 5 mm incision
is made over the left groin and the femoral vein is dissected and
then cannulated using a 22 G angiocath. Venous access is used
to deliver fluids, drugs and to obtain blood for testing or with-
draw blood to create hypotension.
The vessel cannulation is usually done in the following
steps. The vessel is dissected from surrounding structures using
microinstruments (forceps, probes). The distal end of the ves-
sel is tied with a suture (5-0 or 2-0 silk) and a clip is applied to
the proximal part. A small opening is made in the vessel wall
and the tip of the angiocath is introduced into the vessel.
A suture is tied over the cannula to secure it. The proximal clip
is removed and the catheter is advanced into the artery. Another
suture is taken through the skin and the cannula is double
secured (see Note 4).
5. Temperature probe is inserted into the rectum and the tem-
perature is maintained at 36.5-37.5°C (see Note 5).
3.2 Surgery
(Procedure,
Monitoring,
and Models)
1. Craniectomy: The animal is fixed in a stereotactic frame (3 point
fixation: Bilateral ears and the upper incisors). Care should be
taken while shifting and fixing the animal on the frame so con-
nections of the ET tube to the ventilator tubings, arterial access
to the intrarterial BP transducer and the venous access to the
infusion pump remain intact (Fig.
3
). Artificial eye ointment is
applied to the eyes. The skin over the cranium is clipped.
A midline incision is made over the scalp to expose the bones.
The bregma (junction of fronto-parietal and interparietal sutures
in the anterior part) and lambda (junction of the midline inter-
parietal and parieto-occipital sutures) are identified (Fig.
3
).
The skin edges are retracted using a retractor or sutures. The
periosteal layer is scraped and the boundaries of craniotomy are
identified. A craniotomy is performed in the region of right
parietal bone. Usually a trough is made in the shape of a rect-
angle within the borders of the parietal bone till the dural ves-
sels are visible through the thinned bone. Then the entire piece
of bone is lifted with a small clamp (another technique is to drill
the entire surface of the parietal bone till it becomes thin enough
to visualize the dural vessels and then using a small, blunt curved
forceps the thinned out bone is elevated). This step should be
followed carefully done to avoid dural tears. The left parietal
bone is also drilled so that it is thin enough to allow cerebral
blood flow measurements if required. Brain temperature probe
(0.003 in. diameter type K thermocouple microprobe) is
inserted into right frontal lobe after making a small hole with
the drill. The ICP monitoring transducer (1.4 F ultra miniature
pressure transducer) is inserted into the left frontal lobe after
making a small hole with the drill (Fig.
3
) (see Note 6).
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