Practical Points in Emergency CT for Emergency Physicians
-
Upload
rathachai-kaewlai -
Category
Healthcare
-
view
1.129 -
download
0
Transcript of Practical Points in Emergency CT for Emergency Physicians
Practical Points in Emergency CT for EP
Rathachai Kaewlai, MDRamathibodi Hospital, Mahidol University, Bangkok
Annual Conference of Thai Emergency Physicians (ACTEP)
Greenery Resort Khao Yai, Nakhon Ratchasima | 28 Nov 2014
Emergency Physician Tasks
• Perform a thorough history and physical
• Formulate a reasonable DDx
• Order imaging tests based on suspected diagnosis
• Correctly perform the imaging test
• Correctly interpret the imaging test
• Correctly apply the test result to patient care
David T. Schwartz, MD. NYU
Outline
• Imaging utilization in ED
• Radiation dose from emergency CT
• IV contrast issues
• PO contrast issue
• What CT can diagnose and what it cannot
CT Imaging Share Increases Significantly in a Decade
U.S. Medicare Data
CT18%
XR78%
US3%
MRI0%
NM1%
2002
CT30%
XR65%
US4%
MRI1%
NM0%
2012
Levin DC, et al. J Am Coll Radiol 2014;11:1044-1047.
CT per 1,000 ED visits Also Increases from 6% to 15%
U.S. Medicare DataLevin DC, et al. J Am Coll Radiol 2014;11:1044-1047.
Bundling of upper/lower abdomen
codes
2012: 150 CTs per 1000 ED visits
% of Visits with CT PerformedUSA (15%) vs. Canada (8%)
Berdahl CT, et al. Ann Emerg Med 2013;62:486-494.
20142012
Fear of Lawsuits Does Not Drives Unnecessary ED High-cost Imaging
Waxman DA, et al. N Eng J Med 2014;371:1518-1525.
Minimal Variations Found Amount Emergency Physicians on Imaging
UtilizationWong HJ, et al. Radiology 2013;268:779-789.
More ED Imaging Utilization in Certain Patients’ and Visit Characteristics
Wong HJ, et al. Radiology 2013;268:779-789.
Advanced ageArrived by ambulance
Higher acuity areaMore secondary
diagnoses
MoreHigh-cost imaging when
ED most busyMore
Low-cost imaging when ED least busy
Lesson #1
• CT continues to be the main imaging workhorse in ED, following x-ray
• CT utilization increases even in the midst of cost-cutting reform and in States where malpractice has been reformed
• What drives CT use in ED is likely multifactorialand physicians’ characteristics might not be a culprit
There is no safe dose of radiation.- Edward P Radford, MD
Scholar of the Risks from Radiation
Mechanism of X-ray InjuryMedscape © Nat Rev Cancer 2009
Tissue Sensitivity
Most sensitive
Least sensitive
Bone marrow (red), colon, lung, stomach, breast
Gonads
Bladder, esophagus, liver, thyroid
Bone surface, brain, salivary glands, skin
Ref: ICRP 2007
Tissue Sensitivity ~ rate of cell proliferation Inversely ~ to age Inversely ~ to degree of cell
differentiation Higher dose = more damage Young = more damage
Diagnostic x-ray Risk
Procedures Effective Dose (mSv)
Risks
CXR (PA), extremity XR <0.1 Negligible
Abdomen XR, LS spine XR 0.1-1 Extremely low “death from flying 7200 km”
Brain CT, single-phaseabdomen CT, single-phase chest CT
1-10 Very low “death from driving 3200 km)
Multiphase CT 10-100 Low
Interventions, repeated CT >100 Moderate
Avoid Unnecessary CT
Avoid Unnecessary CT:
Import Outside Studies into PACS
In an age in which we can download movies and music from the cloud, it is
inexcusable to subject patients to avoidable cost and radiation exposure when the technology exists to ensure
that images are readily accessible.Zane RD. JWatch Emergency Medicine
Moore HB, et al. J Trauma 2013;74:813-817.
Lesson #2
• CT radiation dose is a real concern especially in children and young adults who have longer life expectancy
• High-radiation risk procedures: multiphase CT and repeated CT
• Beside technical changes on Radiology side, EP can help by selecting an appropriate imaging for clinical question and avoid duplicated exams whenever possible
IV Contrast
High osmolarity (1500+)Ionic
Low osmolarity (300-900)Non-ionic
OLD, IONIC, HYPEROSMOLAR AGENTS
NEW, NON-IONIC, LOW OSMOLAR AGENTS
Benefits of IV contrastVisualization of structures and pathologies, focal pathology in solid organs and necessary for CT angio
Disadvantages of IV ContrastAnaphylactoid reaction (mostly mild: skin rash)
http://aic-server4.aic.cuhk.edu.hk/web8/Hi%20res/anaphylaxis.jpg
No True Iodine Allergy
Iodine is a part of our body and important source of metabolism (thyroid hormone).Seafood allergy is because of muscular proteins
Rate of Contrast ReactionLasser EC, et al. Radiology 1997;203:605-610.
5-15% 0.2-0.7%Fatality ~ 2.1 per 1 million (US FDA)
OLD, IONIC, HYPEROSMOLAR AGENTS
NEW, NON-IONIC, LOW OSMOLAR AGENTS
Lesson #3
• Newer, non-ionic, low-osmolar contrast is much safer than older ones
• Most reactions are mild, cutaneous
• There is no true iodine allergy
• What we should ask patients: prior history of reaction to IV contrast (most substantial), atopy and asthma
Contrast-induced NephropathyControversies
Definition of CIN | No control group on studies of CINNo risk threshold of renal function test | Problem with sCr vs. eGFR
Acute Kidney Injury: AKIN Definition
• Any one of these within 48 hours of contrast– Absolute increase of sCr >0.3 mg/dL
– % increase of sCr >50% (1.5 fold above baseline)
– Urine output decrease to <0.5 mL/kg/hfor at least 6 hrs
• Serum creatinine limited by – Influence of gender, muscle mass, nutritional status, age
– Can be “normal” until GFR decreases by 50%
• Estimated GFR with Cockcroft-Gault or Modification of Diet in Renal Disease (MDRD)
Acute Kidney Injury from IV Contrast
Data from cardiac cath overestimates risk of intravenous contrastNewhouse JH, et al. AJR Am J Roentgenol 2008;191:376-382.
Cardiac cath data (arterial injection)
IV (venous) injection
Acute Kidney Injury from IV Contrast
Newhouse JH, et al. AJR Am J Roentgenol 2008;191:376-382.
Studies with a control group of patients NOT receiving IV contrast>50% of 30,000 patients showed change in sCr
>40% showed change of at least 0.4 mg/dL
https://c2.staticflickr.com/6/5049/5241695367_aa1610e8e1_z.jpg
Risk Threshold
• No universal agreement on threshold
• No agreement on how long from baseline to use sCr before IV contrast
• Ramathibodi protocol
Lesson #4
• Controversies on IV contrast and renal toxicity persist. Now it is best to follow local standardized protocol
• Best method to reduce risk of CIN is adequate hydration prior and after exposure
Oral Contrast Controversy
Jakebouma.com
V.S.
BARIUM
ThickerLower risk of aspiration
Not used if suspect perforation
WATER SOLUBLE
Higher aspiration riskBetter choice if suspect perforation
Oral Contrast: Benefitsbetter delineation of bowel, movement to rectum suggests incomplete obstruction or ileus
Oral Contrast
• New with MDCT, less need for PO contrast
• Dramatic decrease in ED time intervals in patients receiving NCCT in evaluation of flank pain (312 min for renal stone NCCT vs. 599 min for abd CT with PO contrast
Hunyh LN, et al. Emerg Radiol 2004;10:310-313.
Even without oral contrast, cancer of the colon and terminal ileum can be appreciated
Lesson #5
• Avoiding oral contrast can help speed up the process of getting a CT
• This can be helpful in certain group of patients: trauma, acute abdomen (not suspected of perforation or fistula)
Select the Right Imaging Exam
• Selecting correct imaging modality can
affect patient outcome, prevent delay and
influence type and onset of Rx
• Acute abdominal imaging options: X-ray,
ultrasound, CT
When CT is Helpful
Perforated appendicitis
When CT is Helpful
Acute cecal diverticulitis
When CT is Helpful
C.difficile colitis
When CT is Helpful
Adhesive small bowel obstruction
When CT is Helpful
Closed loop small bowel obstruction
Closed loop small bowel obstruction
When CT is Helpful
Mesenteric arterial occlusion with bowel ischemia
When CT is Helpful
Perforated acute cholecystitis
When CT is Helpful
Obstructing right UVJ stone
Lesson #6: Disorders that can be missed by CT -- Abdomen
• Low-grade SBO
• Colonic volvulus
• Mesenteric ischemia (early)
• Ischemic bowel obstruction
• Ovarian torsion
• Mild pancreatitis
• Traumatic bowel perforation
• Diaphragmatic tear
• Mild appendicitis (occasionally)
Lesson #6: Disorders that can be missed by CT -- Others
• Small SAH
• DAI
• Early cerebral contusion
• Early ischemic stroke
• Small lesions (tumors, aneurysms)
• Posterior fossa
• Subsegmental PE
• PE in poorly performed study
• Coronary cause (in non-coronary CTA)
Conclusion
• CT is the main imaging workhorse in ED, following x-ray. What drives CT use in ED is likely multifactorial
• CT radiation dose concern in people with longer life expectancy
• Newer, non-ionic, low-osmolar contrast is much safer than older ones
• Controversies on IV contrast and renal toxicity persist. Now it is best to follow local standardized protocol
• Oral contrast can be avoided in certain scenarios
• Know things that can be diagnosed or missed on CT