A simple and versatile method for frequent 24 h blood sample collection in healthy older adults

Repeated 24 h blood sampling, which is required for time series analyses of metabolites and/or hormones that show strong fluctuations in blood concentration over time, has a higher failure rate in older adults. We tailored existing venipuncture protocols toward use for 24 h blood sampling (sampling frequency of 10 min) in older adults. The following modifications were made:
• Pre-sampling: evidence based risk assessment of older adults.
• During sampling:
• Ultrasound-guided identification and characterisation of veins.
• Use of 20-gauge arterial catheter with guide wire for venous access.
• Measures to prevent and/or reduce unidirectional blood flow (fluid flow into but not out of the vein) included:
• Use of hot water bottles to dilate veins.
• Use of small gauge syringes, shortening of the extension line, and slowing of the blood withdrawal rate to reduce pressure on veins.
• Stimulation of movement of the arm or retraction of the IV cannula to relieve mechanical flow obstruction.
• Post-sampling: prevention of bruising and prolonged bleeding.

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