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Open sheaths will bleed back and risk air embolism so need
obstructing by pinching, use of a valve and rapid insertion
of the catheter tip. Sheaths easily kink and may need to be
pulled back to allow catheter passage.
Long, thin, coated guidewires (70
+
cm) can be passed via a
sheath or catheter to aid central placement. Venography
can be used via needles, sheaths, or catheters if difficulties
ensue. For fixed-length catheters (e.g. dialysis type) plan
the length of tunnel tract and exit site to provide right
length to insert into vein.
Ports can be inserted under LA +/- sedation, or GA. The
incision and pocket size can be reduced by placing anchor
stiches in the pocket first, then sliding the port in. Subcu-
ticular sutures provide a good scar.
Aftercare
External anchoring devices should retained for 3-4 weeks
to allow tissue ingrowth into cuff (slowed with chemo-
therapy or general debility). PICCs have no internal anchor
and need an external suture, adhesive device, or hooked
anchor device.
If the patient is considered at high risk of thromboembo-
lism, therapeutic dose anticoagulation may be indicated.
Some units lock dialysis type cannullae with heparin 1000
units/ml, this needs aspirating before use. Thrombosed/
blocked catheters or fibrin sleeves may be unblocked, or
prevented with low doses of thrombolytic agents (33).
DEVICES
Medium term
Mid-lines (10–20cm) are inserted in the upper arm, with
the tip in the upper third of the basilic/cephalic vein or
axillary vein, short of the central great veins, and are suit-
able for up to 3 weeks of non-irritant solutions.
Long term
PICCs are advanced centrally from the antecubital fossa/
upper arm vein. Cuffed catheters are tunnelled from the
insertion site to chest/abdominal wall. A woven cuff allows
tissue ingrowth for anchorage. These may be soft narrow
bore or larger dialysis type devices. Subcutaneous totally
implanted ports are inserted surgically on the chest,
abdomen, or upper arm. Devices are made with single and
multiple lumens, some are CT compatible, rated as suitable
for high pressure (325 psi) injection of X-ray contrast.
Arterial access
Relevant indications include the following:
•Cardiovascular monitoring
•Repeated arterial sampling
•Pulse contour analysis
•Aortic balloon pumps
•Extracorporeal circuits
Common access sites include the radial, ulnar, brachial,
dorsalis pedis, and femoral arteries.
The presence of an arteriovenous fistulae requires consid-
eration.
Applied anatomy
Peripheral arterial access is usually
performed via the radial artery in the non-dominant
forearm. A patent ulnar artery provides alternative flow to
the forearm and hand so that if the artery is thrombosed,
tissue loss does not usually occur (34). The brachial artery
can be used, but as it is an end artery, distal ischaemia is a
risk with occlusion.
Detailed anatomy and variants may be under-recognized
(35).
Superficial radial and ulnar arteries may be cannullated
during attempted venous access (36). Variation in the
upper arm and forearm may not be obvious on palpation
at the elbow (e.g. high bifurcation of the brachial artery)).
Patients with blocked brachial, radial, or ulnar arteries rely
on collateral supply. This should beidentifiable clinically,
and with ultrasound. Careful assessment of perfusion is
needed. Allen’s test; compression of the radial/ulnar artery
and assessing hand blood flow is useful conceptually, but
is not proven clinically (37).
The femoral artery is widely used for diagnostic and inter-
ventional procedures. In the context of more prolonged
catheterization, it carries increased risks of infection and
thrombosis. Higher damage can lead to hidden bleeding
into the abdomen. There is increasing evidence for use of
ultrasound to cannulate the common femoral artery (38).
Practical insertion tips
Multiple needle passes at poor distal vessels may represent
a higher risk than cannulating a larger end artery more
proximally. The femoral and brachial arteries are useful in
shocked patients. In deep arteries (femoral and brachial)
a short catheters can be dislodged with movement.
Seldinger techniques have a higher success than catheter
over needle devices in routine and challenging cases.
Vessels may be calcified, making cannulation difficult and
it may be impossible to close the vessels with pressure
after removal. Other vessels may have aneurysmal changes
or dissection. If difficulties ensue, consider a surgical cut
down to lessen the risk of vessel injury. Large sheaths
in
situ
need systemic heparinization to avoid clot formation.
[VASCULAR ACCESS - DR. ANDREW BODENHAM]