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Radiological Risks & Refeeding syndrome

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Radiological Risks & Refeeding syndrome Kathy Lee March 17, 2006 Is the imaging worth the risks? Outline XR CT Pediatric patients Introduction Xrays discovered by ... – PowerPoint PPT presentation

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Title: 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 Martels 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

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

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 77S10-13.
  • Frush DP, Donnelly LF, Rosen NS. 2003. Computed
    tomography and radiation risks What pediatric
    health care providers should know. Ped
    112951-957.
  • Slovis TL. 2002. CT and computed radiography The
    pictures are great, but is the radiation dose
    greater than required? AJR 17939-41.

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
  • gt10 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
  • Wernickes encephalopathy (ocular disturbance,
    confusion, ataxia, coma)
  • Korsakovs 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 lt0.30mmol/L
    or Sx
  • PO PO4 ? diarrhea
  • IV Na or K PO4 15-30mmol
  • Stop refeeding
  • Monitor urine output
  • Repletion of Mg not necessary unless lt0.5mmol/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
    17632-637.
  • Marinella MA. 2005. Refeeding syndrom eand
    hypophosphatemia. J Intensive Care Med 20155-159.
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