Protocol of Suzman et al:
(1) 1 mg of stannous chloride is injected intravenously. This helps the technetium stick to the erythrocytes.
(2) Insert a butterfly catheter with 2-way stopcock into a peripheral vein.
(3) Prepare a 10 mL syringe with an anticoagulant and 20 mCi of technetium 99m and attach to the stopcock.
(4) 20 minutes after injecting the stannous chloride withdraw 5 mL of blood through the butterfly into the syringe.
(5) With the butterfly in place, gently mix the blood and solution in the syringe.
(6) Let the mixture equilibrate for 10 minutes.
(7) Reinject the mixture and remove the butterfly.
(8) Scintigraphy is performed over the abdomen with pictures taken every 5 minutes for the first hour (12 images) and every 15 minutes from 1 to 4 hours (12 images).
(9) In most cases the study is then stopped. Additional images can be taken for up to 24 hours after the injection.
Factors affecting performance:
(1) The method is better for active/continuous rather than intermittent bleeding.
(2) A certain rate of bleeding may be necessary for it to be seen by scintigraphy.
(3) Bleeding triggered by an activity may be missed if the patient is on bed rest.
(4) The large volume of luminal contents may dilute the tagged red blood cells.
(5) Rapid movement of luminal contents may reduce the ability to localize a source.
(6) Failure to tag the erythrocytes with the radionuclide can reduce performance.
Geneal rules:
(1) A scan performed soon after the injection may give the best image if bleeding is active.
(2) False positive results may occur. A positive result should be verified by another method such as angiography or endocscopy prior to surgery.
(3) False negative scans may occur. An alternative method such as capsule endoscopy may be helpful.
