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Pre‐procedural considerations

It is preferable to use the distal lumen of a multilumen catheter when obtaining a sample as it is normally the largest; where these catheters have different‐sized lumens, the largest should be reserved for blood sampling (Gorski et al. [74]).
Table 13.7  Prevention and resolution (Procedure guidelines 13.2 and 13.3)
ProblemCausePreventionAction
Difficulty may be encountered when taking blood samples.Difficulty is common when the central venous catheter is made of silicone and has been in place for a long time. One of the causes is that the tip of the soft catheter lies against the wall of the vessel and the suction required to draw blood brings this into close contact, leading to temporary occlusion. There could also be a collapse of the catheter walls when using the vacuum system, which may necessitate the use of syringes to obtain the blood.Position the tip in the lower superior vena cava or right atrium.Measures to use to try to dislodge the tip include asking the patient to:
  • cough and breathe deeply
  • roll from side to side
  • raise their arms
  • perform the Valsalva manoeuvre, if possible
  • increase their general activity, for example walk up and down stairs ( Gorski et al. [74]).
The tip of the catheter may be covered in a fibrin sheath, which may result in partial withdrawal occlusion (PWO). This may be resolved with rapid flushing of the catheter with 0.9% sodium chloride or a dilute solution of heparin. If it is due to PWO then a fibrinolytic agent may be necessary to remove the fibrin ( Goossens [71], Goossens et al. [72], Kumar et al. [119]).
Pinch‐off syndrome occurs when a CVAD inserted via the percutaneous subclavian site is compressed by the clavicle and first rib and aspirating blood becomes difficult ( Mirza et al. [148]). Ask the patient to lift their arm to the side. If blood aspiration improves and there is little resistance on flushing, suspect pinch‐off and request a chest X‐ray and cathetergram to check for catheter damage or embolism.
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