Formal consent / assent may be appropriate for some procedures, such as tracheostomy, while consent / assent may be implied for minor or life-saving procedures. In any event, always explain to patients, even if apparently ‘unconscious’, what you intend to do and keep relatives informed. Document your intentions, and what has been said / agreed. (See Consent to treatment, p. 29.)

Paralysed and sedated patients in ICU may still feel pain from invasive procedures. Use local anaesthetic for all potentially painful procedures.

Contamination with blood or other body fluids imposes significant risk to staff from blood-borne infection, particularly hepatitis and HIV infection. Universal precautions should be adopted for all invasive procedures. These are intended to prevent the spread of infection, to protect you, your patients and colleagues. It is not always possible to know who has an infection; universal infection control precautions apply to everybody, all of the time:

Wash your hands thoroughly.

Cuts or grazes on the hands or forearms should be covered with a waterproof dressing while at work. Seek medical advice about any septic or weeping areas.

Single-use gloves should be worn for direct contact with blood or body fluid, broken skin or mucous membranes.

Full face visors should be worn to protect against blood or body fluids that may potentially splash the face / eyes.

Gowns or plastic aprons protect clothing from contamination.

Place all sharps directly into a sharps bin; do not manually resheath or break needles. Do not overfill sharps bins, and ensure that the bin is securely fastened before disposal.

Clinical waste should be discarded into colour-coded bags for incineration.

Blood or body fluid spills should be disinfected immediately according to local policies.

Always follow guidelines and safety information that apply to your department. If you need further information, talk in the first place to a senior member of nursing staff. Where necessary, further advice can be obtained from specialists in microbiology, infection control, occupational health, COSHH (Control of Substances Hazardous to Health), health & safety, etc.

ICU patients are generally severely debilitated and at increased risk of infection; therefore, when performing procedures, no matter how minor, good infection control procedures are important. For all invasive procedures strict aseptic technique is required:

Collect all necessary equipment before starting.

Ensure assistance is available to open packs, etc.

Wash hands with disinfectant (generally chlorhexidine or iodine).

Dry hands on towel provided in gown pack.

Put on gown.

Put on gloves using closed technique.

Prepare the equipment on the trolley.

Prepare the patient by washing with 2% chlorhexidine solution (see Epic 2: National Evidence-Based Guidelines for Preventing Healthcare-Associated Infections in NHS Hospitals in England. http://www.neli.org.uk/IntegratedCRD.nsf).

Place sterile towels around the proposed site to make a sterile field.

Remember to keep hands up to avoid contamination.

These are relative. Exercise caution in arteriopaths and do not recannulate an artery where previous vascular compromise has occurred. Where possible avoid areas of local sepsis and trauma, limbs with dialysis fistulae and end arteries such as the brachial artery.

Decide which artery to cannulate. The radial artery of the non-dominant hand is usually preferred in the first instance. Alternatives include the ulnar, dorsalis pedis and posterior tibial arteries. It is pointless, however, to persist with attempts at peripheral arterial cannulation in patients who are hypotensive and ‘shut down’. The femoral and brachial arteries are useful during resuscitation of profoundly shocked patients. Ultrasound guidance is potentially useful at all sites to aid arterial cannulation, particularly in hypotensive patients and those whose landmarks are obscured by oedema or obesity.

Arterial cannulation often results in blood spillage. Universal precautions should be used.

Clean the puncture site and establish a sterile field.

Gently palpate the artery and inject local anaesthetic to raise a small intradermal bleb at the puncture site 1 cm distal to the proposed cannulation site.

A Seldinger technique or a direct cannulation technique may be used.

Seldinger technique

Advance needle through the puncture site towards the artery at a shallow angle. As the vessel is punctured, a flashback of arterial blood is seen in the hub. Pass the guide wire through the needle into the artery. Withdraw the needle and pass the cannula over the guide wire. The guide wire is then discarded.

Direct cannulation

Either: advance the cannula and needle through the puncture site towards the artery at a shallow angle. As the vessel is punctured a flashback of arterial blood is seen in the hub. Holding the needle still, advance the cannula over the needle into the artery. This should be a single smooth movement without resistance.

Or: advance the cannula at a steeper angle and, after observing the flashback, continue through the artery to transfix it. Withdraw the needle slightly from the cannula and then pull the cannula back gently until the tip is in the artery and flashback is again observed. Advance the cannula into the artery.

Following cannulation

Attach extension tubing and three-way tap.

Aspirate blood from the line to confirm placement and to remove any air bubbles, then flush line with saline.

Secure in place and cover with occlusive dressing.

(If using stitches, do not place stitches too deeply. It is possible inadvertently to damage peripheral arteries.)

Attach the arterial catheter to a pressure transducer and flushing device.

Ensure catheter clearly labelled as ‘arterial’ to prevent inadvertent injection of drugs.

Complications of arterial cannulation are shown in Box 15.1.

Vascular compromise may occur at any stage. Inadvertent injection of drugs into an arterial catheter is an important avoidable cause of morbidity and all cannulae and lines should be clearly labelled. Risk of infection increases with time. Any manifestly infected catheter should be removed. After removal press firmly for at least 5 min.Occasionally, persistent bleeding may require a suture (5/0 nylon) to close the skin wound and then further pressure.

If the blood pressure displayed by the invasive arterial monitoring differs from that obtained by non-invasive methods this is usually the result of either damping or resonance in the invasive monitoring. In most cases the mean arterial pressures are usually in close agreement.

Check the arterial line is correctly sited and flush the lumen with heparinized saline.

Check that there are no air bubbles in the connecting tubing or transducer chamber.

Check zero on invasive monitoring.

Check that the transducer is at the level of the left atrium.

In some cases, peripheral vasospasm may be a cause of this error. If in doubt, resite the arterial line, or use the non-invasive measurements of blood pressure. In this case, the line can still be retained for arterial blood gas sampling.

Central venous access is almost universal in intensive care patients. Indications include:

monitoring of CVP

drug administration

total parenteral nutrition

fluid resuscitation

insertion of temporary pacing wires

insertion of pulmonary artery catheters

dialysis

lack of peripheral venous access.

These are relative, but include inability to identify landmarks, limited sites for access, previous difficulties or complications, severe coagulopathy, thrombocytopenia and local sepsis. In addition, if an awake patient is unable to lie flat, central venous cannulation may be impractical.

The use of ultrasound to guide central venous access procedures is recommended in all cases (NICE Guidance. Central venous catheters, ultrasound locating devices, Sept. 2002. www.nice.org.uk/guidance/TA49).

Ultrasound allows for:

direct visualization of the vessels (artery and vein) and their associated structures

identification of thrombosis, valve or anatomical abnormalities

identification of target vessel

first-pass cannulation in the midline of a vessel directly avoiding other vital structures

visualization of guide wire and cannula entering vein

reduction of puncture-related complications.

Use of ultrasound clearly requires understanding of the ultrasound appearances of the anatomy at the various sites of interest. Arteries can be distinguished from veins by their round cross-section, non-compressibility and their pulsatility. Veins, by contrast, show respiratory fluctuation and are easily compressible. When using ultrasound for vascular access you should:

Ensure you are familiar with the device available.

Ensure depth settings, gain and other settings are appropriate.

Place the monitor opposite you at eye level.

Ensure correct orientation of the probe (vessels should be in the anatomical orientation as it would appear from where you are standing.

Identify patent target vessel. (To exclude thrombus in a vein ensure it empties completely with pressure.)

Identify collateral structures to avoid artery, nerves, chest wall and pleura.

Use sterile ultrasound gel and a sterile sheath to maintain sterility.

Puncture the vessel of choice using real time guidance to direct the needle into the vein using longitudinal or transverse approaches.

Verify intravenous placement of the needle, guide wire and catheter with ultrasound.

Traditional approaches to the central veins are described below.

Right sided internal jugular vein cannulation is associated with a lower incidence of complications and higher incidence of correct line placement than other approaches. It is especially appropriate for patients with coagulopathy or those patients with lung disease in whom pneumothorax may be disastrous. It may be best avoided in those patients with carotid artery disease or those with raised intracranial pressure because of the risks of carotid puncture and of impaired cerebral venous drainage. Internal jugular cannulation is associated with a higher incidence of catheter infection than subclavian cannulation but both have a much lower infection rate than the femoral approach.

The internal jugular vein runs from the jugular foramen at the base of the skull (immediately behind the ear) to its termination behind the posterior border of the sternoclavicular joint, where it combines with the subclavian vein to become the brachiocephalic vein. Throughout its length it lies lateral, first to the internal and then common carotid arteries, within the carotid sheath, behind the sternomastoid muscle (Fig. 15.1A). Ultrasound demonstrates the close proximity of the vein to the carotid artery (Fig. 15.1B). Many approaches to the internal jugular vein have been described. A typical landmark approach is from the apex of the triangle formed by the two heads of the sternomastoid (Fig. 15.1).

Slightly extend the neck.

Turn the head slightly to the opposite side.

Palpate the carotid artery at the level of the cricoid cartilage.

Look for the internal jugular vein pulsation. If compressed, the internal jugular can usually be seen to empty and refill.

Introduce the needle from the apex of the triangle at an angle of 30° and aim towards the ipsilateral nipple.

Often when attempting to puncture the vein it collapses under the pressure of the needle and puncture is not recognized. The vessel may then be located by aspirating as the needle is slowly withdrawn. Blood is aspirated as the needle tip passes back into the vein, which refills once the pressure has been removed.

Typical catheter length required is 15 cm from the right and 20 cm from the left. The right side is preferred because left-sided catheters have to traverse two ‘corners’ to get to the SVC and are associated with a higher complication rate.

Fig. 15.1 (A) Approach to the internal jugular vein. (B) Ultrasound appearance of internal jugular vein. Right side viewed from the head of the patient. IJ internal jugular vein, C, carotid artery.

The external jugular vein lies superficially in the neck, running down from the region of the angle of the jaw, across the sternomastoid before passing deep to drain into the subclavian vein. It can be used to provide central venous access, particularly in emergency situations when a simple large-bore cannula can be used for the administration of drugs and resuscitation fluids. Longer central venous catheters can be sited via the external jugular but the angle of entry to the subclavian vein often leads to inability to pass guide wires centrally and results in a high failure rate.

Subclavian vein cannulation is associated with a higher incidence of complications, particularly pneumothorax, and a higher incidence of incorrect line placement than right internal jugular cannulation. It is, however, more comfortable for the patient long-term and is associated with a lower incidence of line infection than other sites of central venous cannulation.

The subclavian vein is a continuation of the axillary vein. It runs from the apex of the axilla behind the posterior border of the clavicle and across the first rib to join the internal jugular vein, forming the brachiocephalic vein behind the sternoclavicular joint. See Fig. 15.2.

Position the patient supine (some people advocate placing a sandbag between the patient’s shoulder blades, which allows the shoulders to drop back out of the way).

Identify the junction of medial third and outer two-thirds of the clavicle.

Introduce the needle just beneath the clavicle at this point, and aim towards the clavicle until contact with bone is made.

To locate the vein, redirect the needle closely behind the clavicle and towards the suprasternal notch.

Fig. 15.2 Approach to the subclavian vein.

Ultrasound can be used to guide cannulation of the subclavian vein using a more lateral approach. The axillary vein can be identified in the apex of the axilla at a depth of 3–4 cm in the average patient. Cannulation of the axillary vein is relatively straightforward under ultrasound control and minimizes the risk of pneumothorax owing to its position lateral to the pleura and chest wall. Longer catheters (20 cm left and 25 cm right) are required by this approach.

The femoral vein lies medial to the femoral artery immediately beneath the inguinal ligament. It is particularly useful for obtaining central access in small children and in patients with severe coagulopathy.

Palpate the femoral artery.

To locate the vein, introduce the needle 1 cm medial to the femoral artery close to the inguinal ligament. It is a common mistake to go too low where the superficial femoral artery overlies the vein. Long catheters, 24 cm plus, are required to get the tip of the catheter into the IVC, which may be required for good flows (e.g. for dialysis).

Ultrasound can be used to identify the vessels and ensure that the vein is punctured near the inguinal ligament where the artery and vein lie side by side. See Fig. 15.3.

Fig. 15.3 Ultrasound appearances of right femoral vein (FV) and femoral artery (FA), viewed from below, at the level of the inguinal ligament. Below this level the superficial femoral artery partially overlaps the vein and the long saphenous vein and other superficial veins join making access more difficult.

The catheter should lie along the long axis of the vessel and the distal segment and tip should be in the superior vena cava (SVC) or at the junction of the SVC and right atrium but ideally outside the pericardial reflection. Catheters below this level may perforate the heart and cause cardiac tamponade. The pericardial reflection lies below the level of the carina and this can therefore be used as a radiological marker. Catheters placed via subclavian veins of left internal jugular vein must not be allowed to lie with the tip abutting the wall of the superior vena cava. This may cause pain, perforation and accelerated thrombus formation. Either advance the catheter to lie in the long axis of the SVC or pull it back to lie in the brachiocephalic vein. See Fig. 15.4.

Fig. 15.4 Optimal position for tip of central catheters on chest X-ray.

Check position (ultrasound and / or landmarks) and try again. If unsuccessful do not persist with repeated passages of the needle in the hope of striking oil! You may have misinterpreted the landmarks, or the vein may be absent or occluded (e.g. with thrombus). Seek help.

Check needle position by drawing back on the syringe; good flow is essential. Adjust the angle of incidence of the needle to the vein to improve flow. Tip the patient further head down to further distend the vein. Try rotating the needle through 180° and draw back again. Remember, the wire must pass easily without force. If this doesn’t work, re-puncture the vein at a slightly different angle.

Occasionally, particularly if using a technique where the wire passes through the barrel of the syringe, it is difficult to know whether you have hit the artery or the vein. In this case it is important to avoid passing a large central venous catheter into the vessel which if arterial could result in vessel damage, stroke or TIA. Consider the following:

Remove the syringe from the needle and observe for pulsatile flow.

Connect a transducer directly to the needle in the vessel and look at the waveform.

Pass the wire into the vessel and remove the needle. Pass an 18-gauge i.v. cannula over the wire into the vessel and remove the wire. Attach a transducer or manometer set directly to the cannula. When venous placement is confirmed, pass the wire back through the i.v. cannula and continue as before.

Complications of central venous cannulation depend in part on the route used but include those in Box 15.2.

The management of pneumothorax depends upon the size of the pneumothorax and the patient’s condition, particularly whether they are ventilated or not. A small pneumothorax in an unventilated patient with good gas exchange may be observed, or aspirated using a small-bore cannula and syringe with three-way tap. Larger pneumothoraces, those that fail to resolve or those that cause any impairment of gas exchange and / or haemodynamics require a formal chest drain. Any significant haemothorax should be formally drained as soon as possible. Once blood has clotted in the chest, drainage is difficult. (See Chest drainage, p. 418.) Seek cardiothoracic / surgical opinion.

Bleeding around the puncture site can occasionally be a persistent problem. If this does not resolve with pressure, use a suture (5/0 nylon) to tie a purse string around the puncture site. This usually stops the bleeding.

Thrombus formation around central venous cannula is common and may lead to deep venous thrombosis and / or pulmonary embolus. Avoid insertion at sites where there is evidence of thrombus on ultrasound scanning. If thrombi are identified around an existing cannula, these should be removed and therapeutic anticoagulation commenced unless contraindicated.

If new central venous catheters are required these should usually be placed at a clean site. Occasionally it may be necessary to change a catheter over a guide wire using an existing site. The technique is similar to that described above for placing any central venous catheter. The main problem is avoiding contamination of the new catheter.

Cut sutures and remove the dressing from the old line before scrubbing.

Use universal precautions, aseptic technique, gown and gloves.

Clean and prepare area (including old catheter).

Pass the wire down the central lumen of the old central venous catheter. (Make sure that the new wire is longer than the old CVP line.)

Remove the old catheter, leaving the wire in place, and send the tip of the old catheter for culture.

Clean the puncture site with antiseptic solution.

Use the wire to site the new line as required.

Removal of central venous catheters can precipitate air embolism, pneumothorax, haemothorax, embolization of thrombus and bacteraemia / sepsis.

Before removing central lines ensure that all drugs and infusions have been stopped or relocated to other lines. Lay the patient down to reduce the risk of air embolism and remove the line smoothly, applying pressure to the puncture site. Apply an occlusive dressing, then sit the patient up. If infection is suspected, send the tip of the line in a dry specimen pot for culture. (See Catheter-related sepsis, p. 340.)

Introducer sheaths are available in a number of sizes for different applications, including insertion of pulmonary artery catheters and temporary pacing wires. In adults, 7.5 or 8.5 Fr are generally used. They may be used as large-bore access for volume resuscitation. Smaller sheaths may be used for introducing specialized monitoring such as jugular bulb oximetery. Large-bore double lumen dialysis catheters are used for haemodialysis, haemofiltration, plasma exchange and rapid transfusion.

See Central venous cannulation above.

All these devices are inserted using a Seldinger technique and a large stiff dilator is used to dilate the initial needle track sufficiently to allow the large-bore catheter to be passed easily into the vessel. These dilators do not pass around tight bends easily and can readily damage or perforate vessels. The left internal jugular vein is best avoided. Introducer sheaths can usually be sited safely at all other sites. Dialysis catheters may be best placed by the right internal jugular or femoral routes. The femoral route may be particularly appropriate in patients with chronic renal failure, to preserve the venous drainage of the arm for subsequent AV fistula formation.

Universal precautions.

Aseptic technique, sterile gown and gloves.

Enter vein with needle, as for central venous line, and pass Seldinger wire.

Make small nick in the skin with a blade.

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