James Blackburn1, Benjamin Walton2
1ST5 Anaesthesia & Pre-hospital Emergency Medicine, North Bristol NHS Trust
2 Consultant in Anaesthesia and Intensive Care, North Bristol NHS Trust
Introduction
Arterial lines are routinely used for hemodynamic monitoring and blood sampling for physiological monitoring in patients at risk of deterioration in the operating theatre, critical care and emergency department settings. While widely recognised to be a safe device, knowledge of anatomy, procedural skills and awareness of safety issues are vital to reduce the risk of harm to both patient and operator.
High profile episodes of harm in recent years[i] have increased awareness of the patient and operator safety, yet despite this no national guideline exists that covers all areas of arterial line safety. Surveys of practice have identified a wide variation in knowledge, practice and guideline usage across services routinely using arterial lines[ii].
This article considers the types of line in use and describes the accepted operator and patient associated risks. There is a wide spread of evidence across different guidelines that applies to arterial line safety – this article attempts to pull some of these together into a single source for reference.
Common indications and examples for arterial line insertion are shown in Table 1.
Site selection: Advantages & disadvantages
Radial artery placement is the usual first choice in the majority of patients and has the advantage of reliable anatomy, superficial location, easy palpation and visibility under ultrasound (if used) as well as suitable caliber in the majority of patients, excluding small infants. It is however, more prone to occlusion and haematoma formation compared with other sites.
Femoral insertion is frequently used, if radial or brachial catheterisation has failed, or is unavailable. This has the advantage of larger caliber and reliable anatomical landmarks in all age groups. Further advantages include the potential to exchange lines at this site for other access devices e.g. for interventional radiology or peripherally invasive continuous cardiac output monitoring. Femoral artery catheters are also thought to be less easy to accidentally displace compared to other routes[iii]. Significant disadvantages include deeper course compared to the radial and brachial arteries and possibly higher risk of local and systemic sepsis (see below). In obese patients excess abdominal tissue may obscure landmarks and lead to additional tissue overlying the point of insertion increasing the difficulty of insertion. Furthermore, in the operating theater setting, access to the line site following surgical preparation and draping of the patient can become challenging.
The brachial artery lacks the benefit of collateral circulation and therefore is commonly felt to have the risk of significant distal limb ischaemia if the artery becomes occluded. Although case reports of this can be found in the literature, ischaemia is often associated with larger caliber lines (e.g. transbrachial hepatic sampling) or high medical complexity of patients. A large recent study of 858 perioperative brachial artery complications showed only 3 complications and no statistical difference in complications between radial and brachial arterial catheterisation[iv]. The brachial artery lies in close proximity to the median nerve. One small case series looking at brachial catheterisation reported a median nerve damage rate of between 0.2 and 1.4%, although this was with wide bore catheter use[v].
Dorsalis pedis insertion is occasionally used due to easy superficial location and simple access. However, this pulse if often challenging to palpate or ultrasound in the haemodynamically compromised patient, and measured pressures may not accurately reflect cardiac output due to distance from the central circulation and possibility of the limb resting significantly below the level of the vital organs.
Ulnar arterial catheterisation is rarely undertaken in anaesthetic practice. While there is published evidence of ulnar artery catheterisation for percutaneous coronary intervention[vi], due to a higher complication rate of ulnar artery access many patients were treated with antiplatelet therapies, anticoagulants and or vasodilators following puncture which would not normally be possible in most critically ill patients. Routine anaesthetic and critical care doctrine would be to avoid the use of the ulnar artery for catheterisation unless no other safer alternatives exist.
In selecting an insertion site, the role of ultrasound