R/O acute cholecystitis - HIDA (DISIDA) scan.
Middle of the night?
Only if surgery is going to operate.
R/O pulmonary embolus.
This is done if the patient cannot have a CT scan after
hours.
Reasons:
 Creatinine too high (> 1.5);
o Consider dehydration and look for
trends of lab values. Hydration can
be given before and after contrast
administration. (500 ml before and
after is a reasonable regimen).
 Allergy to iodinated contrast;
 Pregnant (relative contraindication, as
there is less radiation dose, but the ACR has
designated that no single diagnostic
procedure is absolutely contraindicated in
pregnancy);
 The patient cannot be treated with
anticoagulant coverage until 7:30 the next
day or until the above parameters can be
corrected (e.g., hydration, unknown
allergy to contrast).
Confirm Brain Death.
Usually for organ donation reasons.
GI Bleeding.
UGIB and LGIB are often very concerning for the housestaff caring
for the patient, as these entities can be life threatening disorders,
especially in the elderly patient with cardiac and possibly other
coexisting diseases. Treat this phone call as a consult, not an order
for a study. This is a complicated, multi-step process.
1st step: Calm the house officer and take the patient’s past medical
and past surgical and medication history. Make sure to get this
information in full, as this will be important to give to the attending
when you call him or her, and when considering the patient for an
angiographic procedure. Write this information down.
When obtaining the history and physical information, make
sure to inquire about the coagulation parameters and CBC
(with trends). Frequently, these will be super-therapeutic and
the cause of the patient’s bleeding. When these are corrected,
the bleeding will often stop. Super-therapeutic parameters also
limit angiography therapy options and effectiveness.
Inquire about any known contrast allergies or renal failure or
other contraindications to angiography.
Can the patient give consent for angiography? If not, is
there someone else available to give consent? (If there is no
family to consent, 2 physicians outside of the department can
consent.)
If the patient has been passing blood per rectum, but not at alarming
rates continuously, you can relay to the house staff that the blood
which was passed (causing all this franticness) could have been in the
large intestine since the last bowel movement. That said, the nuclear
medicine – angiography pathway is designed to detect active bleeding,
happening at the time of the examination.
At night, the study we perform is a Tc-99m sulfur colloid scan per
department policy. This does not require drawing the patient’s blood
for the examination and is slightly quicker to do. It also does not
interfere with a planned tagged RBC study the next day.
The advantages of Tc-SC imaging is that the agent is rapidly cleared from the
intravascular space by the reticuloendothelial system. The circulating half-life in patients
with normal liver function is between 2-3 minutes, and by 15-20 minutes there is
effectively none left in the blood. This permits clear visualization of extravasated isotope
at bleeding site. The technique is very sensitive and can detect bleeding rates as low as
0.05 to 0.1 cc/min. (Angiography realistically requires a bleeding rate of about 1.5 to 3
ml/min. to be detected. Angiography will detect GI bleeding in 65% of patients when the
bleeding rate exceeds 1 ml/min.)
Disadvantages Tc-SC: Prominent liver and spleen activity may obscure the bleeding site.
The imaging time is markedly limited (probably no more than 10 minutes). Given the
characteristic intermittent nature of GI bleeding, unless the patient is actively bleeding at
time of study, the site of hemorrhage will not be detected. Reports have indicated that the
sensitivity Tc-SC imaging for GI bleeding is about 30% of the labeled RBC technique.
Because of this, to improve sensitivity, some centers will administer the agent in 2 mCi
doses, every 10 minutes for an hour.
Alternative: Technetium labeled RBC's: (Dose 20 mCi)
The main advantage of using labeled RBC's is that the agent remains in the intravascular
space for 24 (up to 48) hours, thus it is excellent for imaging intermittent or slow bleeds.
Liver, spleen, kidneys and bladder (due to excretion of non-erythrocyte bound tech and
labeled hemoglobin fragments) are also visualized, but to a lesser degree and thus will
probably not obscure the bleeding focus.
The labeled RBC exam cannot detect bleeding rates as low at the Tc-SC exam, however,
bleeding rates as low as 0.1 to 0.5 cc/min. and sensitivities of over 90% have been
reported for this procedure (the tagged RBC exam has a sensitivity of 91% and a
specificity of 95% of GI bleeding [Datz, p. 349]). Continuous imaging is recommended
because it is often difficult to localize the bleeding site with intermittent imaging. In vivo
labeling of the RBC's is also not recommended as free tech will be excreted by the gastric
mucosa and pass into the small bowel and colon. Continuous gastric suction may be
required if the in vivo labeling technique is used. In vitro tagging results in significantly
less amounts of free technetium. Presently, many centers employ the use of the ultratag
kit for labeling the RBC's prior to GI bleed imaging.
The purpose of the nuclear medicine examination is to find patients
likely to have active bleeding during angiography. There is no need
to do angiography on a patient who is not bleeding by the bleeding
scan as demonstrated by their relative sensitivities.
This last point brings up the need for surgical and
cardiology/internal medicine consultation. Surgery needs to
direct the care toward angiography if the patient is not in need
of emergent surgery. GI bleeding may require emergent
surgery, and it would be bad to have such a patient under a
gamma camera for an hour if that is the case. If the patient is
unstable and still needs a GI bleeding study, a nurse should
accompany the patient to the nuclear medicine department.
Surgery also needs to know about the patient for any
angiographic complications that might arise during diagnosis or
treatment in angio.
Cardiology and internal medicine input is helpful to clear the
patient for vasopressin therapy. Vasopressin could potentially
have cardiac side effects, and the patient may have known
ischemic CAD. In this setting, one might choose to use
embolization to arrest active bleeding in angio.
Finally, there is literature to support emergent endoscopy in actively
bleeding patients. Below are given two examples. Medicine may
want to consult gastroenterology for a case.
Paper on GI Bleeding from University of Washington: Margaret Shuhart,
M.D. , Kris Kowdley, M.D., and Bill Neighbor, M.D.
http://www.uwgi.org/cme/cmeCourseCD/ch_07/ch07txt.htm see section
2.2.2
Urgent colonoscopy for the diagnosis and treatment of severe diverticular
hemorrhage. From Jensen, M.D., Machicado, M.D., Jutabha, M.D.,
Kovacs, M.D. at the Digestive Disease Research Center, UCLA
http://content.nejm.org/cgi/content/abstract/342/2/78