Radiological Risks Refeeding syndrome

1. Radiological Risks& Refeeding syndrome Kathy Lee March 17, 2006

2. Is the imaging worth the risks?

3. Outline XR CT Pediatric patients

4. Introduction Xrays discovered by Roentgen in 1895 Widespread use (including shoe fitting) Until reports of side effects Radiation dose expressed as millisievert (mSv) Background radiation ~3mSv/yr Coast-to-coast round trip flight in a commercial airplane ~0.03 mSv

5. Commonly ordered XR

6. Radiation doses have been decreasing better equipment better training in its use Shielding further helps to lower exposure Distance cheap and effective I / D2 = I / d2 3m for portable XR trauma room is 3m

7. Pregnant patients Dr Martel�s presentation Consider US/MRI Shield uterus when possible Scan if necessary

8. CT Dose burden concern to radiologists and to regulatory authorities �high dose procedure� Small individual risk of carcinogenesis from CT Atomic bomb survivors 600% increase in all Ct exams mid-80s to mid-90s UK National Radiological Protection Board (NRPB) �increased lifetime risk of death from a malignancy induced by CT � abdomen on the order of 1 in 2000� Image quality improves with increasing dose Plain film will be overexposed if radiation dose increased

9. Plain film and CT doses

10. Spiral CTs higher dose than regular CT Data set of higher and lower slice needed to recontruct highest/lowest slice Larger volume of body is scanned than that selected Image acquisition speed increased Larger body volumes in little time Responsibility of ordering MD, radiologist, manufacturer to lower radiation exposure to patients Necessary study Target suitable organs Modify parameters for patient size Avoid multiphase scans Preset low dose protocols for children

11. Pediatric patients In USA, 2000, 11% of CT performed in children (2.7 million) 1 fatal cancer per 1000 pediatric CT exams Evidence that CT techniques not often suitably modified Smaller body volume Smaller organs Increase sensitivity to radiation � 10x Girls more than boys Longer lifetime for radiation effects to manifest Increased radiosensitivity of certain tissues Thyroid gland, breast, gonads

12. Is the anxiety justified? Small amount of radiation may actually be beneficial Established in animal/plant models, but not in man Epidemiological studies: lower level of cancer after low-level exposure Below threshold of some 200 - 500mSv (66.7 � 166.7 yrs of background radiation), evidence of beneficial effects Hormetic effect Decreased chormosomal aberration Immune response increased Some truth of �therapeutic CT� Hormesis, then, is the term for generally-favorable biological responses to low exposures to toxins and other stressors. Hormesis, then, is the term for generally-favorable biological responses to low exposures to toxins and other stressors.

13. ALARA conference 2001 As Low As Reasonably Achieavable radiation dose strategies to reduce CT radiation dose in children Judicious use of CT Consider alternate modalities such as US or MRI Adjust CT technique Minimize use of multiple scans Limit coverage to answer clinical questions avoid routine scanning of pelvis as part of abdomen to reduce exposure to gonads May seem obviousMay seem obvious

14. Consider breast shielding Adjust individual settings based on indication detection of large vs small abnormality follow-up examination Adjust individual settings based on body region scanned lower tube current for chest and skeletal CT less radiation needed than abdo/head Adjust individual settings based on the size Use new scanner technology that makes automatic regional adjustments in radiation dose during scanning

15. References http://www.radiologyinfo.org. Accessed March 12, 2006 Archer BR. 2005. Recent history of the shielding of medical X-ray imaging facilities. Health Phys. 88(6):579-596 Dawson P. 2004. Patient dose in multislice CT: why is it increasing and does it matter? Brit J Rad 77:S10-13. Frush DP, Donnelly LF, Rosen NS. 2003. Computed tomography and radiation risks: What pediatric health care providers should know. Ped 112:951-957. Slovis TL. 2002. CT and computed radiography: The pictures are great, but is the radiation dose greater than required? AJR 179:39-41.

16. Refeeding Syndrome

17. Outline Pathogenesis Clinical manifestation Prevention and management

18. Introduction Potentially lethal condition Severe lyte and fluid shifts Associated with metabolic abN in malnourished patients undergoing refeeding orally, enterally or parenterally

19. Patients at risk incl: >10% weight loss over mos - hunger strikers not fed for 7-10d - chronic EtOH prolonged IVF repletion - anorexia nervosa malnourished elderly Pt - post-op Pt oncology Pt undergoing chemoTx More common in those fed enterally, elderly

20. Pathogenesis During starvation: Overall catabolism of adipose tissue and muscle, loss of lean body mass Insulin decr, glucagon incr Glc synthesis via lipidand protein breakdown products Adipose tissue release FA, glycerol Muscle release aa KB and FFA replace glc as major energy source

21. During refeeding: Shift from fat to CHO metabolism Incr protein synthesis glc load incr insulin release Incr cellular uptake of glc, PO4, K, Mg, water

22. Clinical manifestation Disturbance of body-fluid distribution CHO / high protein� decr water/Na excretion Protein � incr Na excretion Resulting hyper/hypo-natremia, dehydration/fluid overload AbN glc and lipid metabolism Hyperglycemia can lead to ketoacidosis/metabolic acidosis ? hyperosmolar nonketotic coma Glc converted to fat ? hypertriglyceridemia, fatty liver, abN LFT, higher respiratory quotient ? incr CO2 production / incr PaCO2 Level of hyperTG further decr in critically ill Pt

23. Thiamine deficiency Cofactor for enzymatic activity CHO refeeding incr cellular thiamine utlization Wernicke�s encephalopathy (ocular disturbance, confusion, ataxia, coma) Korsakov�s syndrome (short-term memory loss, confabulation)

24. Hypophosphatemia Predominant feature, major intracell anion 80% in bony skeleton, 20% in soft tissues Rich source in protein-rich food, cereals, nuts Absorb 70%, Excrete renal (90%) Kidney recycle, homeostasis Buffer, part of PL, nucleic acid, enzymatic phosphorylation, ATP, chemotaxis Clinical manifestations: Neurologic (fits, weakness, parethesia, acute encephalopathy) Muscular (weakness, myalgia, rhabdomyolysis, decreased cardiac contractility, cardiomyopathy) Hematologic (dysfunction of platelets and leukocytes, thrombocytopenia, hemolysis) Respiratory (impaired respiratory muscle function sometimes resulting in respiratory failure or ventilator dependency) Bone (osteomalacia) Renal (acute tubular necrosis)

25. Hypokalemia Intracell, maintaines cell-membrane action potential Homeostasis regulated by kidney Clinical manifestations: Neurologic (paralysis, paresthesia) Musculoskeletal (rhabdomyolysis, respiratory depression, weakness) Cardiac (arrhythmias, hypotension, digoxin toxicity, cardiac arrest) GI (constipation, paralytic ileus) Renal (Decreased urinary concentrating ability) Metabolic (metabolic alkalosis, glc intolerance)

26. Hypomagesemia Intracell, found in bone and muscle Largely absorbed in upper sm intestine Absorb 30%, Excrete kidneys Clinical manifestations: lyte (hypo -K, hypo- Ca) Neurologic (tetany, paresthesiae, seizures, ataxia, tremor, weakness) Cardiac (arrhythmias, e.g., torsade de pointes, hypertension) Gastrointestinal (anorexia, abdominal pain)

27. Prevention and Management Monitor lytes (Na, K, PO4, Mg Correct electrolyte disorders before refeeding Restore circulatory volume Correct vitamins (thiamine) / trace elements Cal repletion slowly at 20kcal/kg, 1.5g/kg protein

28. Repletion of PO4 not necessary unless <0.30mmol/L or Sx PO PO4 ? diarrhea IV Na or K PO4 15-30mmol Stop refeeding Monitor urine output Repletion of Mg not necessary unless <0.5mmol/l or Sx PO Mg ? GI upset, poorly absorbed IV MgSO4 4g Can treat refractory hypo-K

29. References Crook MA, Hally V, Panteli JV. 2001. The importance of the refeeding syndrome. Nutrition 17:632-637. Marinella MA. 2005. Refeeding syndrom eand hypophosphatemia. J Intensive Care Med 20:155-159.