Between the Lines #3 – Caring for Arterial Lines

Good news, my writers block is cured! Bad news, it took a patient incident to unblock it; let me tell you a little story about my recent night shift…

Startled from my note writing by loud shouts for help from my colleague who was stuck in a lonely side room, my usually cucumber cool colleague sounded very uncool indeed and on entering the room I could see why. Picture the scene, its late at night but the side room lights have been turned to full brightness, all the monitor alarms are screaming and there is a literal bath of blood on the sheets, blanket and bed. My colleague, who is up to his elbows in the claret, is gripping the slippery arm of the patient and raising it as high in the air as he can get it. In her deep sleep, the patient has gotten her arterial line caught on something and, perhaps dreaming that she is trying to drag a reluctant dog out for a walk in the rain, she has yanked her arm free, ripping out her radial arterial line.

It takes seconds for what looks like half her circulating volume to pump out of her radial artery and onto the sheets, it takes milliseconds for my colleague to react and stem the flow.

Now I exaggerate of course, the blood loss in this scenario was not as bad as it looked. The patients blood pressure did not budge and her Hb remained the same but its terrifying how quickly something so benign can spiral out of control.

In 2008 the National Patient Safety Agency (NPSA) released its Rapid Response Report into the care of arterial lines [1]. The report makes sobering reading when you consider that insertion and care of arterial lines is a daily task in most critical care settings and although it’s now 10 years old, the findings remain highly relevant. Despite recommendations from the NPSA I continue to see unlabelled arterial lines, near misses related to incorrect selection of infusion fluid, confused and picky patients left unsupervised with lines and vascular compromise from poor site selection. (BTW the NPSA are now the National Patient Safety Team under NHS Improvement).

Many Emergency Departments will choose to perform intermittent arterial ‘stabs’ to check on a patient’s acid base balance rather than inserting an indwelling line. Considering the importance of close monitoring, I can understand why. In a busy ED, patients with indwelling arterial lines should probably be placed in the resus bays where staffing ratios are higher and the lines can be closely monitored. The risk benefit of hourly arterial punctures vs an indwelling line and all the complications that come with it should be considered by the responsible nurse and discussed with the inserting practitioner.

Gerald is 58 and he has been admitted from home with infective exacerbation of COPD. On admission to the ED he is short of breath and cyanosed, Gerald’s wife admits that she does not think he has urinated all day, has not opened his bowels for a week and she called the ambulance because he had seemed confused and was unable to walk. The admitting nurse gets Gerald comfortable in a resus bay and plugs him in to all the monitors; on discovering that his non invasive blood pressure is only 88/40 and his pulse rate is 110 with a temperature of 38.6, the nurse asks the medical staff to urgently review. Gerald has a number of presenting factors that would indicate an arterial blood gas measurement including shock, sepsis, respiratory and renal failure. The reviewing practitioner asks the nurse to set up for an arterial line as regular blood gases will be needed to titrate treatment.

Setting up for an arterial line and running through a transducer is quite straight forward and beautifully illustrated on our Instagram by @Vicky_ED_EDU. Check your local policy for what fluid should be selected and whether your transducer set has a manufacturer recommended run through procedure. This blog post will be concentrating on the care of the line and some hints and tips to maintain line patency and enhance patient safety.

When inserted and used correctly, arterial lines can provide a convenient way of monitoring blood pressure, blood gases and taking blood for other laboratory tests. The line doesn’t completely replace the need for non invasive blood pressure monitoring and I would always recommend checking both to see whether they correlate. The readings will not be exactly the same, the non invasive technique tends to look at the larger brachial vessel while the arterial line (when inserted in the wrist) looks at the smaller radial vessel so there will be a difference.

Problem comes when there is a large difference and that is where it is important to make sure that the arterial trace on the monitor is an accurate one. Arterial traces should mirror the pressure changes between systole and diastole with a rapid pressure increase to a peak during systole and quick drop in pressure followed by a slower run off of blood once the aortic valve has closed (dicrotic notch) [2]. The image below (reproduced from shows a great example of an arterial waveform but it rarely looks this neat.

To get the best trace you can, position the limb in a normal anatomical position. For the radial artery, keep the wrist as straight as possible, for the femoral, avoid kinking the line by sitting the patient bolt upright. After making sure the transducer set is free from air bubbles, connect to the arterial line and zero the transducer to atmospheric pressure at the level of the patient’s right atrium. The Phlebostatic Axis, as we call it in the trade (lol, no we don’t), can be located around the patients 4th intercostal space in the mid axilla line and is used as the calibration point regardless of whether the arterial line has been inserted femorally or radially [3]. Regular flushing via the transducer before and after taking samples will aid in maintaining patency but if the fluid bag has been pressurised to 300mmHg, dependant on the manufacturer it should run through 0.5-3mls/hr of fluid. Care should be taken when selecting heparinised solutions, whilst evidence suggests heparin is more effective than normal saline at maintaining line patency [4], a 100IU/ml infusion fluid will be infusing up to 300IU/hr into the patient and that does not include the flush boluses that the nurses administer.

Most practitioners will avoid the brachial artery or going too high towards the ante cubital fosse and should assess the radial and ulnar artery sufficiency before inserting a line.

Looking at the arterial circulation of the arm it becomes clear that if you restrict flow of blood with a cannula into either the radial or ulnar then the unobstructed vessel will need to take up the slack to perfuse the hand. Restricting flow at the brachial could be a one-way ticket to obstructing flow to the whole arm.

The inserting practitioner should perform an examination called an Allen test. This simple test will help to prevent any complications from the cannula but is not a replacement for assessing capillary refill in the hand periodically. Check out this video from Physiotutors on YouTube to understand the test.

Please make sure you clearly label an arterial line. In my trust we place a big sticker near the 3 way tap which says ‘NO DRUGS’. There are purpose made labels out there but a plain label with red writing scrawled on it seems to do the trick just as well. I also see a lot of departments using a blue CVC transducer or a plain set and although these do the same job, red lines are available and from a human factors perspective, anything red screams danger and will make someone think twice before they act. In my humble opinion, red arterial transducers should become commonplace in the same way as yellow is standard for epidural and purple is standard for enteral, it’s a no brainer!

Our patient Gerald will need to be monitored closely once his line is in place. Regular perfusion checks to his hand, close attention to the insertion site and careful labelling should prevent any complications but sometimes even the closest monitoring can miss something. Like my night shift example, patients are unpredictable and dislodged or inadvertent removal of lines can result in a scary situation that looks a lot worse than it is. Arterial lines should be sutured in and carefully dressed in place with your trusts chosen IV dressing leaving the site visible for your VIP scores.

The inimitable @ashleighlowther pointed out that departments worry that patients may be sent to the ward with arterial lines in by accident. Whilst I see her point and this would need to be a risk mitigated by the responsible nurse; after I suggested I squeezed a blood pressure cuff super tight on her arm every 10 minutes and stabbed her in the wrist with a green needle every 30 minutes, she soon saw it my way! Sounds to me like Gerald has bought himself a critical care bed anyway.

So that’s it. Simple! Another line for you to unnecessarily tangle up in ED just so your critical care friends can have an exciting 5 minutes untangling! Rest assured I have not used the word exciting sarcastically here either, we love a good untangle, its like those unboxing videos you see on YouTube only we claim throughout the process to be really annoyed about how untidy [insert your dept. name here] always are.

I hope you enjoyed the read and don’t forget, every day is a school day and some of what you have read here relates to the RCN National Curriculum and Competency Framework Level 1 CD2.7.

Patients #betweenthelines don’t mind if those lines are tidy or tangled, they just want safe and effective care and a bit of hand holding and listening along the way. Keep up the good work for 2019 and catch you all soon.

Holly x.

  1. Rapid Response Report. Problems with Infusions and Sampling from Arterial Lines (2008). National Patient Safety Agency.
  2. Normal Arterial Line Waveforms (2018). Alex Yartsev.
  3. Arterial Line and Pressure Transducer (2017). Chris Nickson, Life in the Fast Lane.
  4. Finding a Solution: Heparinised Saline vs Normal Saline in the Maintenance of Invasive Arterial Lines in Intensive Care (2016). Everson, M. Webber, L. Penfold, C. Shah, S. Freshwater-Turner, D. Journal of the Intensive Care Society.


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