VASCULAR ACCESS PROCEDURES

Vascular access procedures are most common parenteral interventions in pediatric wards for therapeutic fluid/ drug infusions or diagnostic blood sample collections.

For the sake of description, these procedures may be broadly divided into: (a) peripheral venous cannula­tions, (b) umbilical vein catheterization, (c) intraosseous cannulations, (d) central venous catheterizations, (e) arterial punctures, and (f) collection of blood samples.

A. Peripheral venous cannulation (PVC): Peripheral veins are preferred choice for venous access due to easy

TABLE 32.1: Best infection control practices for intradermal, subcutaneous and intramuscular injections

I. Use sterile injection equipments

• Use sterile syringe and needle for each injection and to reconstitute each unit of medication

• Ideally, use a new, single-use disposable syringe and needle

• Inspect packages for barrier integrity and discard in damaged

II. Prevent contamination of injection equipments and medication

• Prepare each injection in clean designated area, unlikely to be contaminated with blood/body fluids

• Use single-dose vials rather than multi-dose vials

• If multi-dose vial is unavoidable, pierce the septum with sterile needle. Don't leave the needle in stopper for re-use

• Select pop-up ampoules rather than those, which require cutting with a metal file.Protect fingers with a clean barrier, e.g. cotton gauze while cutting the ampoule, if necessary

• Inspect for and discard visibly contaminated medications or those with breached integrity

• Follow product-specific recommendations for use, storage and handling

• Discard a needle, if it has touched any non-sterile surface

III. Prevent needle-stick injuries to the provider

• Anticipate and prevent patient's movements during injection

• Avoid recapping, if necessary, use single-handed scoop technique

• Collect used needles/syringes at the point of use in a puncture-proof sharp's container and seal before it is full

IV.

• Seal sharps' container before transport to designated area for disposal. Don't open, empty, reuse, sell them

• Manage sharps waste in an efficient, safe and environment-friendly way to protect people from voluntary/accidental exposure

V. Other practical issues

• Whenever possible use auto-disable syringes or other devices to prevent needle-stick injury

• Wash/disinfect hands before preparing injection and administering them. Avoid giving injections if hands have local infection/ dermatitis. Cover small cuts

• Routine use of gloves are unnecessary. Use single-use gloves if excess bleeding is anticipated

• Routine Swabbing of vial/ampoule tops with antiseptic is unnecessary. If necessary, use a clean single use antiseptic swab with adequate contact time as per product specifications. Don't use stored wet cotton balls

• Routine swabbing of skin before injection is unncecessary but wash visibly dirty/soiled skin. If necessary, use a clean single use antiseptic swab with adequate contact time as per product. Don't use stored wet cotton balls

procedure and less risk of infections/ complications than central venous catheterization.

PVC devices: Two most commonly used PVC devices in children are: (a) over-the-needle catheters (venflon), and

(b) butterfly or scalp-vein needles.

• Over the needle catheters (venflon) is the preferred choice for peripheral venous cannulations due to less chances of dislodgement on patient's movements and local thrombophlebitis. These catheters, available as pre-sterilized disposable items in variable sizes (fG 18-24), have two parts: (a) outer teflon or polyurethane sheath (catheter) with connecting port, and (b) inner metallic needle, which acts as stylet during insertion. Apart from PVC, these catheters can also be used for arterial cannulation or as venesection catheter for thin veins (Fig. 32.4). Different sizes of cannula are often color-coded for easy identification, e.g.

• Scalp vein (Butterfly) needle has three parts: (a) a short, fine-bevel metallic needle, (b) a 15-20 cm long polyethylene tube connected to needle with a stopper at other end, and (c) a butterfly-shaped plastic grip at the junction of needle and tube to assist fixation

Fig. 32.4: Over the needle catheter.

(Fig. 32.5). These needles are available in different sizes (No. 18-24), in pre-sterilized gamma-irradiated pack and should not be re-used.

Scalp vein needles are generally used for: (a) short­term venous cannulation, or (b) blood sample collections in newborns and young children. These needles tend to dislodge easily and should be avoided for prolonged cannulations. Although the name suggests their use for cannulation of scalp veins, these needles may also be used at other sites.

Fig. 32.5: Scalp vein (butterfly) needle.

Other sites of peripheral venous access, e.g. Femoral or external jugular venipuncture are rarely used in children due to the risk of concealed hemorrhage/extravasation or spasm of neighboring artery.

B. Umbilical vein catheterization is a useful method to obtain venous access in newborns for: (a) IV drug administrations during resuscitation, (b) exchange transfusions, (c) collection of blood samples, and (d) central venous pressure (CVP) monitoring.

Procedure: Umbilical cannulation is possible only in first 5-7 days of life. Although special thin and long umbilical catheters are available, a small diameter infant feeding tube may also be used for this purpose. Important steps in umbilical cannulation are as follows:

PVC sites: Although the choice of venepuncture site depends on personal preference and experience, a thumb rule is to begin with a vein, which is most prominent, not attempted before and will not interfere with resuscitation efforts or other diagnostic/therapeutic interventions.

Commonly used PVC sites in children are: (a) dorsal veins of hand/foot, (b) great saphenous veins over medial malleolus, (c) cephalic, basilic or median cubital vein over antecubital region, and (d) superficial veins of scalp. Femoral or external jugular venipuncture is rarely used in pediatric practice.

PVC procedure (Venflon): While PVC cannot be learned without actual practice, important steps for over the needle catheter insertion are as follows: Select a suitable site gt; restrain the baby gt; wash and glove the hands gt; tie a tourniquet proximal to the site or ask the assistant to compress proximal venous flow gt; clean the venipuncture site with an antiseptic and allow it to dry for 1-2 minutes-the time required for it bactericidal action gt; flush the selected catheter/needle with saline to check patency and avoid air-locking gt; fix the selected vein by stretching overlying skin between two fingers

gt; puncture the skin slightly distal or lateral to intended venipuncture site gt; advance the needle till blood flows freely gt; advance the remaining catheter over the needle

gt; withdraw the needle gt; flush with saline to ensure free forward flow of fluid gt; fix the catheter with adhesive tape and connect it with infusion set.

Similar steps are used for butterfly needle insertion except that it has no overlying catheter and needle itself is left in situ.

Complications: (a) local extravasation of fluids due to displaced catheter/needle, (b) local thrombophlebitis, cellulitis or gangrene, (c) distal vasospasm with gangrene, (d) catheter-related bacteremia/septicemia, and (e) air or catheter-fragment embolism. As the risk of catheter - infections rises rapidly after 48-72 hours, even well-placed PVC devices should be changed every 72 hours.

Clean the umbilical area with antiseptic and drape it with sterile towels gt; wash and glove the hands gt; cut the stump with a sharp scalpel close to its base to visualize three collapsed vessels-single thin-walled umbilical vein and paired thick-walled umbilical arteries gt; clean the umbilical vein opening with a forceps, if necessary

gt; guide the special umbilical catheter or feeding tube gently into umbilical vein with rotating movements for ~5-15 cm gt; check the free blood flow into catheter

gt; connect it with infusion set gt; fix the catheter with purse-string sutures gt; place a dry gauze over cord area, to prevent contamination.

Complications: (a) local trauma, (b) thromboembolic complications, (c) bacteremia/septicemia, (d) portal vein thrombosis with development of extrahepatic portal hypertension in later life.

C. Intraosseous cannulation: Intraosseous cannulation is a safe, simple and reliable method to administer drugs, fluids or blood products into non-collapsible venous plexus during resuscitation, when IV access is difficult and cannot be achieved within three attempts or 90 seconds. This access is easier to obtain in children lt; 6 years, though may be attempted even in older cases.

Any IV fluid or drug may be infused via intraosseous route with comparable dose, onset of action and efficacy. However, rapid volume infusions or viscous drugs may need to be administered under pressure to overcome resistance of emissary veins.

Site: The flat anteromedial surface of tibia, ~1-3 cm below the tibial tuberosity is preferred site of intra­osseous cannulation in children lt;6 years due to large marrow cavity at this site and least risk of injury to adjacent tissues (Fig. 32.6).

Devices: While specific intraosseous needles are available, a regular bone marrow aspiration needle (Jamshidi type) is commonly used. Simple wide-bore IV needles or LP needles are not recommended due to chances of blockage and bending.

Fig. 32.6: Intraosseous cannulation.

Procedure: Important steps in intraosseous cannulation, after proper restraining the child, are as follows:

• Locate and mark the cannulation site by palpation, roughly one finger-width below and medial side of the tibial tuberosity.

• Wash the hands properly and wear gloves.

• Clean the site with an antiseptic and allow it to dry for 1-2 minutes for bactericidal action.

• Check the needle to ensure proper alignment between bevels of outer needle and internal stylet.

• Insert the needle at selected site at 90° to the long axis of bone and advance with a gentle but firm twisting motion till sudden decrease in resistance is felt and needle remains upright without support.

• Unscrew and remove the stylet and check the location by aspiration of bone marrow, if required.

• Flush the needle with 10 ml normal saline to ensure patency and check for any sign of resistance in fluid flow or soft tissue swelling.

• Stabilize the needle with adhesive tape and connect it with infusion set.

Insertion is successful if: (a) the needle remains upright without support, (b) marrow can be aspirated, and (c) fluid flows freely without subcutaneous infiltration.

Complications are rare (lt;1%) but tends to be more severe than PVC. Hence, this procedure should be reserved only for critically sick children as a temporary measure till other secure venous access is obtained.

Reported complications include: (a) tibial fracture, (b) local skin necrosis or compartment syndrome, (c) osteomyelitis and very rarely, (d) fat embolism. Local effects of intraosseous infusions on long term bone growth are negligible.

D. Central venous cannulation (CVC) that reaches up to Superior vena cava or right atrium is used in intensive care for: (a) hemodynamic central venous pressure (CVP) monitoring, (b) frequent blood collections, and

(c) prolonged infusion of irritating solutions, e.g. total parenteral nutrition.

A special long silastic or polyethylene catheter is used for CVC, introduced through a large peripheral vein, e.g. subclavian, external jugular or femoral vein by Seldinger technique. While details of this procedure are beyond the scope of this book, important steps are as follows: Puncture the vein with a needle gt; insert a guide wire through the needle into vessel gt; withdraw the needle, leaving guide wire behind gt; sheath the catheter over guide wire till superior vena cava under fluoroscopic guidance.

Complications: Although CVC catheters can be kept in situ for longer periods than PVCs, risk of complications, e.g. infections, thromboembolism, traumatic bleeding and arrhythmia as well as procedural difficulties are more than PVCs and preclude frequent use in pediatric practice

E. Arterial cannulations Arterial access is required for continuous BP monitoring and collection of arterial blood gas samples or other blood samples in critically sick children. Arterial lines should never be used for fluid or drug infusions.

Sites: Radial artery is the preferred site for arterial cannulation, although other peripheral arteries, e.g. brachial, femoral, axillary, dorsalis pedis or posterior tibial arteries may also be used for this purpose. Temporal artery cannulation, though easier, is not advisable due to risk of cerebral thrombo-embolic complications.

Procedure: A heparinized butterfly needle or venflon may be used for temporary arterial puncture for blood sample collections, while special arterial catheters are used for monitoring purpose. The procedure for arterial cannulation is similar to that for venous access, except following considerations:

• Ensure adequacy of collateral flow at selected site, which is vital for local perfusion in the event of arterial spasm during/after the procedure. In case of radial artery cannulation, modified Allen's test may be used for this purpose.

Allens's test: clench the child's hand tightly and raise it above the heart level gt; occlude both radial and ulnar arteries gt; lower the arm gt; open the hand and release pressure on ulnar artery gt; record the time required for return of color over palm; A reperfusion time of gt; 6 seconds indicate poor ulnar collaterals and radial puncture on that side should not be attempted.

• Adequate pressure should be maintained for at least 5 minutes over the puncture site after withdrawal of arterial cannula/needle, to prevent oozing from high pressure vessel.

Fig. 32.7: Heel puncture.

• A continuous infusion of heparin solution (1 IU#8725;ml saline, 3-5 ml/hour) should be maintained in long-use arterial lines to prevent block and thromboembolic complications.

Complications: Excessive local bleeding and temporary vasospasm with compromised distal perfusion are most important complications of arterial punctures in children, though most cases resolve spontaneously. More serious complications of arterial cannulations, usually seen with indwelling arterial lines include: (a) thrombotic vasoocclusion with distal gangrene, (b) air-/particulate matter-embolism, and (c) systemic infections.

F. Collections of blood samples: Various methods used for collection of blood samples in young children include: (a) peripheral venipuncture with a heparinized scalp vein set, (b) arterial puncture, and (c) heel-puncture in newborns and young infants. Radial artery puncture is commonly used to collect arterial blood samples for Blood gas analysis.

Samples may also be collected from existing PVC or arterial lines, though some values, e.g. blood glucose or cultures are unreliable from such samples. Femoral venipunctures, once commonly used, are rarely used at present due to risk of femoral arterial spasm or concealed hemorrhages in femoral space.

Heel puncture is a useful method to collect capillary blood sample in newborns for hematologic, biochemical or blood gas investigations, as follows:

Cover the heel with warm wet towel for 5 minutes to increased local vascularity gt; clean it with antiseptic

gt; puncture the lateral or medial 1/3rd of heel skin with an stillette, pricked perpendicularly for ~2-2.5 mm depth

gt; wipe off the first drop of blood gt; collect subsequent flow in capillary tubes (Fig. 32.7).