Routine blood sampling

Daily Bloods

  • FBE; UEC; Mg; PO4; LFT; LDH, APTT, INR, Fibrinogen and D-dimers
  • APTT is measured 6 hourly while the patient is on ECMO if they are receiving systemic anticoagulation. In selected patients, Anti Xa levels are used for monitoring. For patients not on heparin, APTT is only measured in the am DAILY.
  • Plasma free Hb is measured 6 hourly (with the APTT). The sampling rate may be reduced in stable patients
  • ABG sampling 2-3 hourly

Plasma free haemoglobin

Performed 6 hourly whilst on ECMO (routinely with the APTT samples) according to clinical need/ECMO clinician direction. Samples are taken by passively filling a 10ml syringe carefully. Do not connect to a negative pressure “vacutainer” for sampling. The plasma-free Hb collection tube is filled from the syringe after removing the lid, gently injecting blood from the syringe and then replacing the lid. No needles are required. Avoid shaking samples, which will falsely raise the plasma free-haemoglobin. Normal operating plasma free-haemoglobin level is 0.05 g/L.

In the event of Plasma free-haemoglobin reading above 0.05 g/L

  • Patient should be assessed immediately for evidence of intravascular haemolysis: dark/red urine or CRRT effluent with high K+
  • Circuit should be assessed for signs of malfunction: “noisy” pump head (pump head thrombosis), visible access insufficiency, or high transmembrane pressure gradient (oxygenator thrombosis)
  • A high reading associated with clinical evidence of haemolysis or circuit malfunction demands a rapid response and must be communicated to the ICU Consultant immediately
  • If the circuit is functioning and there are no clinical signs of haemolysis then a repeat sample should be taken and meticulously handled
  • Repeat readings above 0.05g/L, less than 0.10 g/L often are insignificant and related to sampling technique, however, they can represent the start of an exponential rise with grave implications
  • Causes of low-level haemolysis include: access insufficiency without visible kicking (may require echocardiography to detect venous “suck-down” with a multistage cannulae); vessel-cannula impingement due to pericardial collection or retroperitoneal haematoma; or excessive speed settings with small cannulae (greater than 4000 RPM).
  • Blood cultures are taken only as clinically indicated. That can be a peripheral blood culture (by the senior registrar) or alternatively these samples could be taken from the circuit or through existing lines.

Leave a comment

Feedback and comments are appreciated, although we cannot respond to each comment. Your email address will not be published. Required fields are marked *