Laboratory investigations and arterial blood gas sampling in the Emergency Department (ED)

Objectives

The following information is to aid emergency department staff in the use of laboratory services and arterial blood gas sampling. This guideline relates to the use of investigations by doctors working in the ED.

The use of investigations in the ED

Is an investigation necessary?

Discuss any potential blood test with the ED senior. Only very rarely will the result of a blood test truly influence whether or not you need to admit a patient.
Blood should only be sent from the ED if the patient is sick and an early result will alter patient management.
If you have performed an investigation please record this clearly in the ED.

Remember, the core question to be asked before doing any investigation is ‘what difference will this test make to my management of this patient at this moment in time within ED?

Integrated Clinical Environment (ICE)

Blood requests should be completed using the ICE system, and sent by pod system to the laboratory (code 777 for combined biochemistry/haematology, 671 for Blood Transfusion Service, and 666 for microbiology).

In the event of ICE failure, samples should be labelled clearly with black ballpoint pen, and sample bags with attached paper request forms are available in all clinical areas.

In the event of pod failure, the ED porters can be asked to take samples to the laboratory for analysis.

Microbiology samples in the ED

If starting IV antibiotics before admitting a patient, effort should be made to get a blood culture sample prior to administering the antibiotic. This can help the admitting team make appropriate antibiotic changes during the patient’s admission, as samples taken after antimicrobial administration may yield inaccurate or inadequate results.

Blood culture indications visual pathway

Blood culture indications Q & A algorithm

Blood culture sampling checklist guideline

Arterial blood gas analysis in the ED

Arterial blood gas analysis can be an extremely helpful investigation in the management of a number of potentially serious conditions presenting to the ED. A blood gas analyser is available within the Ninewells ED. New members of staff will be shown how to use the analyser during the induction course. Please try to use a patient ID number for all samples. Staff at PRI require to send the sample to the biochemistry lab or ask a member of nursing staff to take the sample to the Intensive Care Unit (ICU) analyser. Junior doctors should discuss their patient with the senior doctor prior to ABG sampling.

ABG usernames and passwords should not be shared between users. If you do not have a username or password and require one, please contact the biochemistry department. All new doctors in the ED should be given access at the same time as their ABG analyser training.

If an unknown patient requires an ABG, their name should be recorded as "unknown" and their ID number should be the unique “A&E no.” printed at the top of their ED front sheet.

The ABG analyser also gives serum sodium, potassium, and chloride ion concentrations, as well as haemoglobin. These results give a rough indication only, and should not be relied upon to guide patient treatment. Formal samples must be sent if the result is required to guide ongoing patient care.

Emergency (accelerated) potassium request (Ninewells Hospital)

1. Decision to request emergency potassium taken by senior doctor

2. Light green top tube (heparinised)

3. Request “emergency potassium” on test requesting (ICE)

4. Contact lab – 36666 (9am-9pm) or bleep 4027 at other times

5. Place sample in bag with ICE sticker on sample and on the bag

6. Transport to lab

Use the pod system

If the pod is system busy, ask a porter to take the sample to the lab and hand it over to the on call biomedical scientist or the person in the specimen reception area, do not leave it for someone to pick up.

If you require other tests e.g. U&E, Mg, Ca these will need to be requested on a separate sample and another request created on ICE.

Last reviewed: 02/12/2020

Next review date: 02/12/2022

Author(s): Shobhan Thakore,, Connor Bowbeer.