See Figure 1.
Central venous lines are essential tools in the care of complicated patients, both on inpatient wards and in the emergency department and intensive care unit. They may provide access for blood draws, facilitate central administration of fluids and medications, and allow direct measurement of cardiac filling pressure.
Unfortunately, central lines are associated with serious complications, including nosocomial bloodstream infections. Recent data suggest that of the more than 200,000 such infections each year, 90% are due to central lines.1 One can minimize patient risk by practicing proper sterile technique during line insertion, maintaining adequate occlusive dressings, and removing all unnecessary lines as soon as possible.
The three main approaches used to place central lines are the internal jugular, subclavian, and femoral. This chapter reviews the subclavian approach; other sites are detailed in separate chapters. See Central Venous Catheterization: Internal Jugular Approach and Central Venous Catheterization: Femoral Approach for further details.
- Administration of agents into the central vasculature (see Figure 2)
- Central venous access is required to administer certain medications, including most vasoactive and/or inotropic agents (i.e., vasopressors such as dopamine and norepinephrine). In addition to expediting delivery of these drugs to the heart and arterial system, central administration decreases the risk of damaging peripheral tissue from the vasoconstrictive effects of the medications.
- Patients needing total parenteral nutrition also require central access because the osmolarity of the mixture exceeds what can safely be administered into the peripheral circulation.
- Other hyperosmolar agents that are optimally infused through a central line include concentrated potassium solutions, hypertonic saline solutions, certain chemotherapeutic agents, and calcium chloride.
- Central circulation and intracardiac access (see Figure 3)
- Measurement of central venous filling pressure within the right atrium can be helpful in determining the volume status of a patient and can readily be transduced via a central venous catheter in the internal jugular or subclavian position.
- Specialized pulmonary artery (i.e., Swan-Ganz) catheters can be used to measure pulmonary capillary wedge pressure, a means of approximating left-sided filling pressure.
- Blood drawn from a central catheter can allow the measurement of mixed venous (or central venous) oxygen saturation, often used to estimate cardiac output.
- Temporary transvenous pacemakers can be inserted through central venous catheters (more specifically, sheath introducer catheters) to provide a more reliable and comfortable means of pacing than the transcutaneous route. See Transvenous Pacing for further details.
- Maintenance of venous access
- In acutely unstable patients, peripheral venous access may be inadequate.
- Patients requiring multiple medications in drip formulation can quickly run out of access points.
- This problem is compounded in a chronically ill patient, who oftentimes has insufficient peripheral access because of frequent blood drawing and peripheral intravenous (IV) line placement.
- Central venous catheters provide reliable access for blood drawing and administration of medication, until either peripheral access can be obtained or less venous access is required.
- Hemodialysis and plasmapheresis
- Emergency or short-term dialysis and plasmapheresis can be performed via special central venous catheters (e.g. Quinton catheters).
Clinical Pearls: The subclavian vein approach is suitable for routine and emergency central venous access. Advantages and disadvantages of the subclavian approach include those listed in Table 1.
- Absolute contraindications
- Adequate peripheral IV access: Given the potential for serious morbidity and the high rate of infection associated with central lines, they should be used only when absolutely necessary. See Intravenous Cannulation for further details. See Figure 4.
- Operator inexperience (unless supervised by an experienced practitioner): Although placement of a central line is a relatively safe procedure in experienced hands, those unfamiliar with the technique should study the protocol beforehand to gain confidence and must be supervised at all times during placement of a line.
- Uncooperative patient:
- Placement of a central line requires that the patient remain still so that the operator can define the anatomy accurately, concentrate on steps of the procedure, and be vigilant for signs of complications.
- Needles, scalpels, and sutures are necessary tools in this task.
- Patients who are uncooperative have an unacceptably high risk of injury and also expose the operator to increased risk.
- Adequate steps must be taken to make the patient comfortable for the length of the procedure before proceeding.
- Relative contraindications
- Significant bleeding disorder: Coagulopathies and thrombocytopenia increase a patient's risk for bleeding, but the hemorrhages are generally mild and do not require transfusions.2
Clinical Pearls: Although traditional teachings recommend replacement products (such as fresh frozen plasma or platelet concentrates) before central catheterization, evidence from the literature suggests that this is not necessary.2 The decision to use such products should be made on a case-by-case basis.
If there is concern about the possibility of a bleeding complication, the line should be placed in a location that allows straightforward compression (e.g., internal jugular or femoral vein). The subclavian approach should be avoided because hemorrhage in this location may require surgical intervention.
- Injury or thrombosis in the target vessel or superior vena cava (SVC):
- Depending on the extent of injury or thrombosis, alternative locations may be required for line placement.
- In particular, obstruction of the SVC (e.g., SVC syndrome) from either external compression or internal thrombosis should prompt the operator to use the femoral approach.
- Inability to tolerate pneumothorax: (see Figure 5)
- Patients who have undergone pneumonectomy or who would otherwise not be able to tolerate pneumothorax may not be appropriate candidates for a subclavian or internal jugular venous line.
- If the line is absolutely necessary, consider using the femoral vein.
- Although the risk for infection is increased by using the femoral location, there is no risk of entering the pleural space and potentially causing a fatal pneumothorax.
Clinical Pearls: In the case of a patient who has undergone pneumonectomy or has severe unilateral lung disease, an ipsilateral subclavian line may actually be the site of choice.
- Assisted ventilation with high end-expiratory pressure: In the event of pneumothorax occurring in a ventilated patient, high end-expiratory pressure puts the patient at risk for a persistent air leak or alveolar-pleural fistula.
- Contraindications unique to the subclavian approach3,4
- Bleeding disorders: Because the subclavian site is noncompressible, either the femoral (preferred) or the internal jugular site should be chosen for patients with substantial bleeding disorders.
- Surgery or trauma to the clavicle, first rib, or subclavian vessels: Anatomy may be distorted in these situations and make successful catheterization difficult.
- Administration of thrombolytic medication: If fibrinolytic agents are being used, central venous catheterization should be avoided if at all possible because of the risk of hemorrhage. If a central line must be placed, the femoral approach should be used.
Clinical Pearls: A variety of prepackaged central venous catheterization kits are commercially available. Although the contents of various kits are for the most part quite similar, you should be familiar with the devices available at your institution.
See Figure 6.
- Central venous catheterization kit. Typical kits contain the following equipment, all of which is sterile:
- Clear fenestrated plastic drape
- Paper drape
- Chlorhexidine antiseptic with applicators
- 1% lidocaine
- Small anesthetizing needle (25 gauge × 1 inch)
- Large anesthetizing/finder needle (22 gauge × 1.5 inch)
- Introducer needle (18 gauge × 2.5 inch)
- Several syringes, 5 mL each
- J-tipped guidewire with housing and a straightener sleeve
- Scalpel with a No. 11 blade
- Skin dilator
- Catheter (e.g., triple lumen or sheath introducer)
- Gauze pads
- Suture with curved needle
- Disposable needle holder
- Sterile gloves, sterile gown, cap, and mask with a fluid shield for each member of the insertion team **STERILE TECHNIQUE** **UNIVERSAL PRECAUTIONS**
- Large sterile drape (half-sheet)
- Lidocaine 1% (often provided in the kit, although extra may be required) See Local Anesthesia for further details.
- Sterile saline suitable for injection
- Sterile dressing (e.g., Tegaderm, 3M Corporation, Huntingdon Valley, PA)
- Catheter selection
- A variety of catheters can be used for central venous catheterization; the triple-lumen catheter and the sheath introducer are the most commonly used and are detailed in this chapter.
- Triple-lumen catheters are used when central venous monitoring and/or the administration of fluids or medications is clinically indicated.
- Sheath introducers are used when transvenous pacemakers or pulmonary artery catheters must be “introduced” into the patient. They may also be used when massive amounts of volume must be infused rapidly.
Clinical Pearls: Triple-lumen catheters should not be used if rapid volume resuscitation is required. Peripheral IV lines with 14-gauge catheters can infuse volume twice as fast as a triple-lumen catheter can.4 If peripheral access is not available and volume infusion is urgent, consider placing a sheath introducer.
- Triple-lumen catheter components: (see Figure 7)
- Flexible catheter of various sizes (7 French, 16 cm is typical). The catheter is typically inscribed with depth markers along its shaft.
- Distal, middle, and proximal infusion channels:
- The openings of these channels are visible at the distal (internal) tip of the catheter, and each has a labeled port at the proximal (external) end.
- In most situations, the middle external port corresponds to the distal channel.
- Each channel is usually 16 to 18 gauge in diameter.
- Each external port is supplied with a removable end cap.
- The middle cap should be removed before insertion of the line to allow passage of the guidewire.
Clinical Pearls: If necessary, replace the supplied end caps with the specific needleless adapters that are used at your institution.
- Sheath introducer components: (see Figure 8)
- Single, large sheath catheter (8.5 French, 10 cm is typical). The sheath is designed to accept transvenous pacemakers and pulmonary artery catheters.
- A one-way valve assembly on the proximal (external) end of the catheter through which the pacing or pulmonary artery catheter is inserted. On some sheath introducers, this valve can be rotated clockwise to tighten it around the inserted catheter so that it does not move once properly positioned.
- Many sheath introducers have a side-arm port that allows infusion of fluids through the introducer, even if a catheter is inserted through the main port. This side-arm may have several ports and an integrated stopcock.
- A sterile sleeve is often included in sheath introducer kits. The sterile sleeve device connects to the valve assembly and is designed to encase the inserted device (pacing or pulmonary artery catheter) in a sterile environment.
- The guidewire (see Figure 9)
- The guidewire is used to perform the Seldinger technique, which is described in detail in the Procedure section. Briefly, the main steps of the Seldinger technique include
- Insertion of an introducer needle into the vessel
- Insertion of the guidewire through the introducer needle and into the vessel
- Removal of the needle, with the guidewire left in the vessel
- Insertion of a dilator over the guidewire to create a clear passageway for the catheter
- Removal of the dilator
- Advancement of the catheter over the guidewire and into the vessel
- Removal of the guidewire
- Guidewires are often demarcated with lines every 10 cm to allow estimation of the depth of insertion.
- Many guidewires have a spring-loaded mechanism on one end that produces a 180-degree bend at the tip of the wire; they are referred to as “J-wires.”
- The rounded leading edge of the J-wire allows it to “bounce” off vessel walls, thereby reducing the risk for vessel perforation.4
- A straightener sleeve is included with J-wires. The sleeve facilitates insertion of the wire into the needle hub.
||Clinical Pearls: Some wires may have a “soft-tipped” straight end on the opposite end of the wire. They are engineered to be flexible (to avoid vessel injury) and may be used if there is difficulty passing the J end.4 This type of wire should be used only if you are intimately familiar with your equipment and the procedure.
See Figure 10.
- Subclavian vein
- As the subclavian vein crosses the first rib, it lies posterior to the junction between the medial third and lateral two thirds of the clavicle.
- The vein has a diameter of 1 to 2 cm.
- Connective tissue fixes the subclavian to the first rib and clavicle, and thus the vein does not collapse in cases of hypovolemia or cardiac arrest.3
- The subclavian arteries are located posterior to the veins and are separated from them by the scalene muscles.
- The domes of the pleurae of the lungs may extend above the first rib on the left but rarely extend this far on the right, and thus the right side is often preferred for line insertion.
- Insertion on the right also avoids the risk of damage to the thoracic duct, which is located near the junction of the left subclavian and left internal jugular.
Clinical Pearls: If you are anticipating the use of a transvenous pacemaker or pulmonary artery catheter, you should use either the left subclavian vein or the right internal jugular vein. These approaches align the catheter trajectory with the SVC and right atrium. See Transvenous Pacing for further details.
- Two approaches can be used for the subclavian vein, as shown in Table 2 (see Figure 11).