Abstract
Introduction: Microdialysis can detect ischemia in soft tissue. In a previous study we have shown the development of ischemia in the femoral head removed from patients undergoing total hip replacement.
This study also raised some methodological questions that this study tries to answer.
What is happening in the dead space around the catheter in the drill canal? And is there an equilibrium period after the insertion of the catheter.
Methods and materials:
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Ex vivo study: in 5 syringes with 5 ml human blood a microdialysis catheter was inserted and microdialysis performed over 3 hours.
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In vivo study: in the proximal part of the femur in 6 mature Göttingen mini pigs a drill hole was made and microdialysis was performed over 3 hours. The pigs were kept normoventilated during the experiment.
Results:
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Ex vivo: the microdialysis results showed that lactate kept a steady level and glucose and glycerol all fell, pyruvate fell but leveled out. The lactate/pyruvate ratio increased from 13(4) to 32(6) (p< 0.001).
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In vivo: relative recovery was 57(11)%. Lactate increased, pyruvate stayed constant, glucose and glycerol fell. The lactate/pyruvate ratio increased from initial 30(8) to 37(8) after 1 hour (p=0.007) but no significant change from 1 to 2 hours was observed.
Conclusion: The ex vivo study showed a clear washout pattern, and is different from what we see in bone.
The in vivo study indicates that an equilibrium period is necessary or that a reference measurement in healthy bone must be used when performing short measurements in bone.
Correspondence should be addressed to: EFORT Central Office, Technoparkstrasse 1, CH – 8005 Zürich, Switzerland. Email: office@efort.org
