Abstract
The roots of modern central venous access practice can be traced back to the 1950s and a Swedish radiologist called Sven Seldinger 1 (1921–1998). In 1953, Seldinger published his percutaneous technique in Acta Radiological. 2 Prior to Seldinger, central venous access was commonly obtained by surgical cut-down. Percutaneous central venous cannulation is now a common clinical procedure in critical care and anaesthesia with an estimated 200,000 central venous catheters (CVC) inserted each year in the UK. 3 In the last 15 years, the procedure has been further refined with the availability of high-quality bedside ultrasound imaging. The National Institute for Clinical Excellence (now National Institute for Health and Care Excellence) first published Guidance on the use of ultrasound locating devices for placing central venous catheters (TA49) in October 2002. 4 The document recommended that 2D ultrasound guidance should be the preferred method of inserting elective CVC into the internal jugular vein in adults and children. It also recommended ultrasound be considered in emergency situations. Ultrasound-guided insertion, with its benefit of accurate first pass needle tip placement, is now routine for elective and most urgent internal jugular, axillary and femoral vein cannulations.
The recently published AAGBI Safe vascular access guidelines 5 are the first national UK anaesthesia guidelines on the topic and provide a very comprehensive commentary on the insertion, positioning and removal of vascular access devices. This consensus document is full of useful hints and tips (!) for safe catheter placement and is essential reading for all those undertaking vascular access procedures. After a short introduction, the guideline briefly covers peripheral cannulation, intra-osseous access and arterial cannulation before moving into its core topic of central venous access. The authors provide a useful summary of the limitations of peripheral venous cannulation, describing how central venous access is frequently required for infusion of high osmolar, acid or alkaline substances or simply to provide medium- to long-term venous access. They also draw attention to the underutilised role of intra-osseous devices in rapidly securing vascular access in the emergency patient with difficult veins. They suggest that further training/familiarisation amongst acute care clinicians would help this route realise its full potential.
The lion’s share of the guideline is devoted to practical aspects of insertion/removal of CVC and the prevention, recognition and management of complications. Although CVC insertion is a frequently performed task and often a routine part of anaesthetic practice, the harm from potential procedural complications should not be underestimated. A seemingly simple mistake or moment’s inattention can result in a catastrophic outcome for the patient. As an operator, it is important to be aware of the potential complications and how to safely manage them. The authors’ impetus for the consensus document is the severe morbidity and mortality sadly still associated with vascular access procedures. Indeed, the harm caused by central venous catheter complications is the chosen topic of the first UK Intensive Care National Audit Project. The impact of a misplaced line depends partly on whether the complication is managed correctly. Although most practitioners have extensive experience of line insertion, most of us have limited experience of sorting out a catheterised carotid artery or a superior vena cava perforation bleeding into the pleural space. The real value of these latest vascular access guidelines is their assistance to clinicians faced with such complications. The advice is to seek surgical or interventional radiology assistance and resist the temptation to simply ‘pull it out, press and hope’. The guidelines cover all of the most serious sequelae of needle/catheter misplacement including myocardial perforation, cerebrovascular accident, air embolism and arterial injury. They also provide commentary on catheter occlusion/breakage, extravasation injuries, central venous stenosis, the risk of iatrogenic hypoglycaemia from erroneously using glucose flush solutions in arterial lines and inadvertent anticoagulation from the flushing in of concentrated heparin locks.
The guidelines cover some useful practical points around recommended minimum catheter lengths for different insertion sites, suggested thresholds for correcting coagulopathies and techniques to assist peripherally inserted central catheters (PICCs) to feed into the SVC. Optimal catheter tip positioning is covered in some detail. Although important for all lines, with anaesthetic practice expanding into the insertion of long-term tunneled lines, it is increasingly important that anaesthetic trainees develop an appreciation of the importance of optimal tip positioning.
Following brief sections on infection control, training and medicolegal aspects, the guidelines conclude with recommendations for vascular access service provision. Parallels may be drawn with the introduction of a resident duty anaesthetist on labour ward. 6 Prior to having a dedicated labour ward anaesthetist, epidurals were slotted in between urgent surgical cases and women ended up waiting many hours for – or delivering without – the analgesia they requested. The provision of a dedicated obstetric anaesthetic service led to timely, safe, patient-centred care. Over the last five years, there has been a similar realisation that asking the acute anaesthetic team to squeeze in the odd line insertion between surgical cases leads to a substandard service. Patients requiring vascular access for parenteral nutrition, prolonged antibiotics, renal replacement therapy or chemotherapy benefit from a dedicated elective vascular access service. This is arguably best provided as a joint venture between anaesthesia and interventional radiology, and a successful vascular access service can be provided from a radiology suite or operating theatre with the appropriate imaging facilities. Standalone elective line lists provided by trained and competent operators, with clear patient referral pathways can provide an efficient, responsive and low-complication rate service. Such a service need not solely be delivered by medical staff and Advanced Nurse Practitioners trained in these procedures are at the centre of service delivery in many centres. Vascular access – whilst on one level remaining a core competency of all anaesthetists and intensivists – should also been seen as a worthy subspecialty interest in itself. In a similar fashion to the difficult airway or bariatric anaesthesia, departments benefit from having one or two interested individuals who are able to advise colleagues or directly manage difficult cases.
So what challenges remain and how might central venous cannulation be made safer/developed further? It is clear from the AAGBI guidelines that most of the procedural-based harm caused by CVC insertion are caused directly or are at least preceded by, needle tip misplacement. Constant needle tip visualisation – and the dynamic ultrasound imaging that it requires – remains significant challenges for those learning central venous cannulation. Even the moderately experienced can mistake the needle shaft in cross section for the needle tip, leading to an underestimation of tip depth and the risk of inadvertent pleural or arterial puncture. In the first instance, it is important that operators are appropriately trained and competent in performing the procedure. This includes the correct use of ultrasound; knowledge of achieving an optimal image and the skills required in ultrasound guided needle placement. There are currently simulators and courses run in hospitals to achieve training in these competences.
Adjuncts such as echogenic needle tips, electromagnetic sensors and needle guides exist and could help in accurate needle placement but aren’t part of the standard central line kit in most UK centers. There is some evidence 7 that these technologies can reduce complication rates but as the authors suggest, the cost effectiveness of such adaptations is still to be assessed.
A simple change worth considering would be to make standard venous access needles shorter. Current standard needles are 7 cm in length, whilst the most frequently accessed internal jugular vein usually lies only 1–2 cm below the skin. Using such a long needle makes needle stabilisation harder and increases the number of non-target structures within range of the sharp tip. Acknowledging that accessing the veins of obese patients might require a 7+cm long needle, we would suggest that almost all internal jugular and most femoral vein cannulation could be undertaken more safely with a 5 cm needle. Similarly, the needle supplied with many PICC kits is unnecessarily long for a target vein only a centimeter or two beneath the skin. A shorter access needle would be more maneuverable and provides a quicker flashback of blood once the tip penetrates the vein, helping to avoid puncturing the posterior wall.
Knowledge of patient anatomy is crucial prior to performing central venous cannulation. Clinical history, examination and review of previous imaging (when available) are required to ascertain if there is any evidence of central venous stenosis or occlusion. These do not preclude line placement, however, they can make the procedure very challenging and these patients with altered anatomy may require further imaging or specialist expertise/equipment to achieve line placement.
Finally, with guidewire retention being added to the list 8 of NHS ‘never events’, practitioners should consider adopting a more formal pre- and post-procedure count of sharps, wires and other components when performing central venous access, chest drain and tracheostomy insertion. Traditional surgical accountable items checklists focus on counting surgical instruments and swabs, which for obvious reasons are less relevant to percutaneous techniques. But the risk of foreign body retention is not completely mitigated by a procedure being percutaneous. Many kits contain a myriad of small plastic parts that may inadvertently end up being pushed down into an airway or accidentally retained intravascularly. A difficult procedure, requiring more than one kit to be opened probably increases the risk. 9 A pre- and post-procedure count against a kit-specific contents list, perhaps provided by the manufacturer, would help to prevent the morbidity (and occasional mortality9,10) associated with retained guidewires and other foreign bodies. Practitioners from every specialty should adopt a best practice safety culture, ensuring a consistency of approach wherever and whoever is undertaking these procedures.