Advantages and disadvantages of using the hydrogen clearance technique to measure pancreatic blood flow

This study was undertaken to identify the advantages and disadvantages of using the hydrogen clearance technique (HCT) to measure pancreatic blood flow (PBF) in the opossum over short and long periods. An open study was performed on 8 opossums. A total of 72 platinum electrodes were implanted into the pancreas. On the fifth day 41 additional electrodes were implanted. All implantation sites were examined histologically after five days. Measurements of pancreatic blood flow were taken every other day for five days. Three measurements were taken from each electrode and the mean of the three was used for analysis. In the anaesthetized animal mean PBF (SD) was 63.5 (12.8) ml min^-1 100 g^-1 immediately after electrode implantation and 34.3 (11.4) ml min^-1 100 g^-1 on the 5th postoperative day. Of the implanted electrodes, 35% failed during the experimental course, mainly as the result of proliferation of scar tissue around the electrodes. Mild to moderate fibroproliferation had taken place around the platinum tips of the remaining 65%. Primary electrode implantation caused no or negligible trauma to the pancreas. We recommend the HCT only for short-term measurements of PBF. Implantation of electrodes for any length of time leads to inflammatory changes around the platinum tips that cause proliferation of scar tissue and lead to failure of the electrodes, misleadingly low PBF recordings, and fewer monoexponential clearance curves.