RADIOLOGIC CONTROVERSIES AND NEW MEDICATIONS
| RADIOLOGIC CONTROVERSIES THAT WILL AFFECT YOUR PRACTICE —Timothy Jang, MD, Assistant Professor
of Medicine and Director of Emergency Ultrasound, the David Geffen School of Medicine at the University of California,
Los Angeles
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 | Ordering imaging: must balance risks of disease against risks of test; one noncontrast head computed tomography (CT) in child
<2 yr of age increases lifetime risk for neoplasm by 1 in 2000; child will most likely undergo ≥1 CT during preadolescence;
children who undergo repeated CT for trauma may experience radiation burns; standard abdominal renal stone CT protocol
equivalent to 1000 chest x-rays; pulmonary embolism (PE) protocol equivalent to 1100 chest x-rays
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| Disease risk: must estimate in every patient; if low, or if treatment dangerous, consider deferring treatment; treat aggressively
if disease risk high or treatment effective; if risk falsely assessed as low, patient may suffer because treatment not
given; if risk falsely assessed as high, patient may undergo unnecessary tests or dangerous treatment; likelihood ratio
(LR)—calculated by estimating patient’s risk of having disease before (based on history and physical examination)
and after test; thus, LR depends on sensitivity and specificity of test; positive LR most influenced by test specificity;
negative LR influenced most by test sensitivity
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How Test Choices Affect Outcomes
| Sample case 1: 30-yr-old woman with history of mild occasional headaches presented to emergency department (ED)
with sudden severe headache; no xanthochromia on lumbar puncture (LP); patient discharged with hydrocodone and acetaminophen;
returned 2 days later obtunded; diagnosed with severe vasospasm due to subarachnoid hemorrhage
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| Subarachnoid hemorrhage: occurs in 1 of 10,000 patients with cerebral aneurysms; 30-day mortality rate, 45%; another
30% of patients experience prolonged morbidity; average payment for missed subarachnoid hemorrhage >$1 million;
angiography traditional diagnostic gold standard, but expensive and time-consuming, with 10% risk for morbidity, including
1% risk for neurologic damage
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| Noncontrast head CT: sensitivity ≈99% if performed ≤12 hr after onset of headache, 95% if done within 24 hr; sensitivity
drops markedly (80%-85%) after that; advantages—quick, easy, noninvasive, and effective when performed
promptly; of patients with subarachnoid hemorrhage, only 1 in 1000 have negative head CT and positive LP
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| Cerebral multidetector CT angiography: accuracy greater than that of noncontrast head CT; sensitivity for aneurysms
>5 mm approaches 99% (sensitivity ≈85% for aneurysms <5 mm, but these seldom rupture); can repeat test 1 wk later
and avoid LP
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| Magnetic resonance angiography (MRA): specificity and sensitivity comparable to those of multidetector CT angiography;
advantage—can be performed up to 1 wk after headache onset; disadvantages—possible movement artifact; patient
must stay in MR machine; test takes 30 to 45 min to complete; low sensitivity for aneurysms <1 cm (but risk for rupture
<0.05%/yr)
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| Lumbar puncture: used less in last 5 yr due to relatively low sensitivity (95%); also requires red blood cell count and
spectrophotometric analysis; may yield false-negative results if performed <12 hr after headache onset (takes 12 hr for
xanthochromia to develop); current trend toward noninvasive tests that image vascular tree
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| Interpretation: low-risk patients—LP and angiography probably unnecessary after negative CT angiography (CTA) or
MRA; high-risk patients—standard of care in United States dictates further work-up (LP or angiography) after CTA or
MRA; LP may be obsolete within 3 to 4 yr
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| Sample case 2: 37-yr-old patient with traumatic neck pain after rollover automobile accident; attending surgeon and radiologist
read neck x-rays as negative; patient admitted for observation of splenic injury; however, patient developed C7
quadriparesis due to C6 on C7 subluxation; trauma surgeon settled out of court, but radiologist won at trial, saying he did
not order test and adequately interpreted test that was performed; surgeon should have ordered appropriate work-up
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| Cervical spine (C-spine) injuries: occur in 2% to 5% of patients with blunt trauma (10% of head-injured patients);
70% of missed injuries occur when level of consciousness (LOC) altered; missed C-spine injuries associated with 10-
fold increase in risk for permanent deficit; Canadian C-spine rule—defines high-risk patients as those >65 yr of age,
with dangerous mechanism of injury (eg, fall from >3 ft, high-speed motor vehicle collision), or neurologic symptoms
(not necessarily findings); average award for missed C-spine injury ≈$3 million; depending on protocol, C-spine CT
costs 3 to 5 times more than x-rays; cases settled in favor of plaintiffs—revolve around 1) incomplete C-spine visualization,
2) failure to get Flex-Ex films or CT after plain x-rays, 3) misreading CT, and 4) not obtaining Flex-Ex films
after negative CT in patients with persistent pain
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| Eastern Association for Surgery of Trauma (EAST) guidelines (2000): recommend C-spine x-rays and CT of C1 and C2 for
patients with neck pain if head injury present; CT also recommended for areas not easily visualized on plain films; obtain
Flex-Ex films if previous images normal but neck pain persists; perform CT of C1 and C2 whenever LOC altered; patients
with altered LOC also deserve MRI; if altered LOC prolonged, obtain Flex-Ex fluoroscopy; following EAST guidelines
keeps cost of CT down, so could be cost-effective to perform full CT on high-risk patients (sensitivity for ligamentous injury
comparable to that of Flex-Ex films); Flex-Ex films—done in 25% to 30% of trauma centers; time-consuming; require
more personnel; positive in ≈0.1% of cases and not cost-effective; however, CT does not provide functional
information (Flex-Ex films do), so Flex-Ex films recommended when CT negative but pain persists; ligamentous injury or
cognitive deficits indicate magnetic resonance imaging (MRI), although CT better for fractures; however, fractures missed
by MRI (1%) do not require surgery
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| Interpretation: plain films sufficient for young healthy patient; start with CT if patient elderly, has history of spinal injuries
or abnormalities, or has head trauma or high-risk mechanism; Flex-Ex film indicated if pain persists; MRI or Flex-Ex
film for all patients with cognitive deficits or whose pain persists despite negative findings on other imaging studies; alternatively,
discharge patients in hard collar and repeat film in 2 wk
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| Sample case 3: 40-yr-old pregnant woman with history of asthma presents with cough, shortness of breath, and pleuritic tussive
chest pain; examination reveals wheezing and sinus tachycardia; symptoms improve with nebulizer treatment, but heart
rate on discharge 110 bpm; patient returns in ventricular fibrillation and dies of massive PE; family receives settlement of $1.5
million
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| Pulmonary embolism: occurs in ≈40% of patients with high-risk characteristics; missed PE associated with high morbidity
and mortality; litigation usually involves improper risk stratification and diagnostic work-up; of patients with normal
ventilation-perfusion (V/Q) scan, 2% to 4% develop PE, compared to 87% of patients with high-risk V/Q scan; given level-
A recommendation by American College of Emergency Physicians (ACEP); however, 50% of V/Q scans nondiagnostic;
multidetector spiral CT—actual results may differ from those published, depending on timing of contrast bolus; newer
technology available by time studies appear; however, may provide alternative diagnosis; sensitivity for segmental or larger
PEs 90% to 100%, and 75% to 80% for subsegmental PE; however, long-term risk for negative spiral CT 1%, and fewer
data support its use, leading to level-B recommendation by ACEP; Prospective Investigation Of Pulmonary Embolism
Diagnosis (PIOPED) II — CTA plus CT venography (CTV) of leg better than CTA alone, but cannot be used to rule out
PE in high-risk patients or to rule in PE in low-risk patients; shows CTA good test for people at moderate risk of having PE
(high-risk patients with negative CTA should undergo further testing; low-risk patients with positive CTA should undergo
one more test for confirmation); MRI/MRA—involves no radiation or contrast; sensitivity for segmental or larger PE 90%
to 100%; MRA V/Q scans being developed; pulmonary angiography—still gold standard for diagnosing PE; however,
technically difficult, time-consuming, and invasive; use by interventionalists declining; standard of care evolving
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| Interpretation: V/Q scan indicated for young healthy patients, those who have undergone previous diagnostic V/Q scan,
or anyone with iodine allergy or renal failure; CTA with CTV recommended for patients with known pulmonary disease
or previous indeterminate V/Q scan; consider MRI/MRA or CTA/CTV for pregnant patients (V/Q scan delivers more radiation
to fetus); discharge moderate-to-high-risk patients with normal imaging (repeat tests in 1-2 wk)
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| Sample case 4: 55-yr-old man presented with 3 days of worsening right lower quadrant pain; had tenderness at McBurney
point; underwent CT to rule out appendicitis; radiologist did not see images for several hours, but ultimately diagnosed
perforated appendicitis; patient hospitalized for 16 days; patient sued emergency physician, radiologist, and
surgeon for delayed diagnosis and poor outcome; case settled for $300,000; ordering unnecessary CT when diagnosis
clear clinically now becoming liability (may delay treatment)
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| CT for appendicitis: sensitivity 90% to 95%; multidetector spiral CT has similar sensitivity, takes less time, and does
not require contrast, but requires right equipment and experienced radiologist; best for older or obese patients; could miss
pathologies detected with contrast; clinical follow-up recommended for adult patients with negative noncontrast CT
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| Ultrasonography (US) for appendicitis: primary modality for children and pregnant women; sensitivity 85% to 90%;
less expensive than CT; however, operator-dependent, with indeterminate results in 30% of cases; if suspicions persist despite
negative results, order CT; MRI sensitivity 100% for appendicitis in pregnant women with indeterminate US; used
increasingly when cost and time not at issue
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| Interpretation: for children and pregnant women, start with US; consider MRI if US equivocal; perform CT if MRI not possible;
consider noncontrast CT for moderate-sized adults; start with contrast CT on young healthy men
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| NEW MEDICATIONS IN THE ED—Scott A. Braunstein, MD, Attending Physician, Department of Emergency Medicine,
Cedars-Sinai Medical Center, Los Angeles, CA
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| Propofol (Diprivan): now approved for procedural sedation in ED; properties—sedative hypnotic available only in intravenous
(IV) form; produces moderate or deep sedation in adults and children >3 yr of age; thought to potentiate γ-aminobutyric
acid (GABA) A receptors in central nervous system; not analgesic (administer pain relievers before use); onset
of action ≈30 sec; duration of action ≈6 min; metabolized by liver, excreted by kidney, and redistributes rapidly from
plasma to muscle and fat; dosing—recommended starting dose 1 mg/kg by slow IV push over 15 sec to minimize involuntary
movements; treat with 0.5 mg/kg every 3 min to titrate sedation; maximum dose 4.5 mg/kg; dosages same for children
and adults; side effects—oxygen desaturation to <92% in 5% to 7% of cases; expect systolic blood pressure (BP) to
drop 10 to 20 mm Hg, and in 3% of cases, systolic BP decreases by >20% (optimize volume; treat with IV fluids before
use); involuntary movements (15% of cases); pain at injection site (mix with 2 mL lidocaine to minimize); comparison
with etomidate (study)—propofol associated with higher rate of procedural success, due possibly to less myoclonus;
practice implications—propofol may increase success rate of procedures; many studies support safe use in ED; could
become ideal choice for procedural sedation
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| Sugammadex: Food and Drug Administration (FDA) approval expected; selective relaxant-binding agent; designed specifically
to trap rocuronium (nondepolarizing neuromuscular blocking agent [NMBA]) within its core; succinylcholine,
only depolarizing NMBA available, has advantages of rapid onset of action (1 min) and short time of paralysis (5-6 min),
but associated with serious side effects, eg, hyperkalemia, increases in intraocular and intracranial pressure, dysrhythmia;
sugammadex also effective against other nondepolarizing NMBAs, eg, vecuronium, pancuronium; main drawback of
these agents long paralysis time (15-30 min); in studies, suggamadex—dramatically reduced mean recovery time to <2
min in dose-dependent manner; also enhances renal excretion of rocuronium; no known drug interactions; side effects—
occur in 4% to 5% of cases; mild hypotension, cough, involuntary movements, nausea, vomiting, and sensation of
changed temperature; practice implications—could help nondepolarizing NMBAs become drugs of choice for rapid sequence
intubation
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| Cyanide poisoning: thought to contribute to deaths from smoke inhalation; hydrogen cyanide colorless gas produced from
burning of wood, plastic, and rubber; produced in residential and industrial fires; used in suicide attempts; uncouples oxidative
phosphorylation; symptoms include headaches, seizures, and coma; O2 saturation often normal; tipoffs lactic acid >10
mg/dL, or minimal difference between arterial and venous O2 saturation; current treatment—kit containing amyl nitrite,
sodium nitrite, and sodium thiosulfate; downsides include unpredictable hypotension from nitrites and inducement of methemoglobinemia;
new Cyanokit—contains hydroxocobalamin (form of vitamin B12 ); binds cyanide for urinary excretion;
does not cause hypotension or methemoglobinemia; side effects—transient discoloration of urine and skin, and minor increases
in BP; practice implications—new treatment for cyanide poisoning without side effects of older kit; may be extended
to prehospital care; could be administered empirically in ED to smoke inhalation victims
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| Zingo: lidocaine topical powder housed in needleless system that provides epidermal-type injection; used for local analgesia
before IV needlesticks and blood draws on pediatric patients; used on intact skin only; effects occur within 1 to 2 min; can be
repeated once at new location; produced barely significant pain reduction in 2 manufacturer-sponsored studies; side effects—
local erythema and petechiae; common; practice implications—needlesticks among most painful and traumatic events for
pediatric patients; rapid onset of action could permit more seamless care and decrease ED waiting times; head-to-head comparisons
with currently used agents needed
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| Binax NOW malaria test: point-of-care test with rapid antigen assay for detecting Plasmodium falciparum (most lethal
species) and Plasmodium vivax (most common cause of malaria); analyzes whole blood from venipuncture or fingerstick;
sensitivity >95% (P falciparum), ≈87% (P vivax); specificity for both ≈99%; positive predictive value ≈90%; negative
predictive value 94% to 98%; practice implications—potentially rapid and reliable point-of-care test for malaria;
may be useful in EDs without 24-hr or weekend microbiology laboratories; may be too expensive for use in developing
nations
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| Vernakalant: FDA approval expected; developed to treat atrial fibrillation (AF); currently available agents may cause serious
ventricular arrhythmias; vernakalant avoids ventricular dysrhythmias by working only on atrial potassium channels;
in one study, 51% of patients on vernakalant converted to sinus rhythm within 90 min, compared to 3.8% in placebo
group; median time to conversion ≈ 10 min; 97% still in sinus rhythm after 1 day, 92% at 1 wk; side effects—change in
taste sensation, sneezing, and paresthesias; no episodes of torsades de pointes; ineffective at converting atrial flutter (1 of
39 patients; practice implications—prevalence of AF increasing; vernakalant avoids risk for torsades de pointes and
ventricular dysrhythmias; may decrease admissions by converting some patients to sinus rhythm in ED
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Suggested Reading
Freeman LM: Don’t bury the V/Q scan: it’s as good as multidetector CT angiograms with a lot less radiation exposure. J
Nucl Med 49:5, 2008; Gallagher MJ, Raff GL: Use of multislice CT for the evaluation of emergency room patients with
chest pain: the so-called “triple rule-out.” Catheter Cardiovasc Interv 71:92, 2008; Ghanta MK et al: An analysis for
Eastern Association for the Surgery of Trauma practice guidelines for cervical spine evaluation in a series of patients with multiple
imaging techniques. Am Surg 68:563, 2002; Green SM, Krauss B: Barriers to propofol use in emergency medicine.
Ann Emerg Med February 21, 2008 [Epub ahead of print]; Kerns W 2nd et al: Hydroxocobalamin versus thiosulfate for
cyanide poisoning. Ann Emerg Med 51:338, 2008; Kline JA et al: Impact of a rapid rule-out protocol for pulmonary embolism
on the rate of screening, missed cases, and pulmonary vascular imaging in an urban US emergency department. Ann
Emerg Med 44:490, 2004; Naccarelli GV et al: New antiarrhythmic treatment of atrial fibrillation. 5:707, 2007; Nael K
et al: 3-T contrast-enhanced MR angiography in evaluation of suspected intracranial aneurysm: comparison with MDCT angiography.
AJR Am J Roentgenol 190:389, 2008; Nicholson WT et al: Sugammadex: a novel agent for the reversal of
neuromuscular blockade. Pharmacotherapy 27:1181, 2007; Perry JJ et al: Is the combination of negative computed tomography
result and negative lumbar puncture result sufficient to rule out subarachnoid hemorrhage? Ann Emerg Med. Jan. 10
2008 [Epub ahead of print]; Stiell Ian G et al: The Canadian C-Spine Rule for radiography in alert and stable trauma patients.
JAMA 286:1841, 2001; Wiese L et al: Bedside diagnosis of imported malaria using the Binax Now malaria antigen
detection test. Scand J Infect Dis 38:1063, 2006.
Educational Objectives
| The goal of this program is to improve outcomes in the emergency department by helping physicians choose the most appropriate
radiologic tests for patients with stroke, cervical spine injuries, and pulmonary embolism and use the latest drugs
and reagents for conscious sedation, cyanide poisoning, and malaria therapy. After hearing and assimilating this program,
the clinician will be better able to:
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| 1. Assess the importance of an imaging study based on the likelihood ratio of the patient’s injury or disease.
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| 2. List the advantages of multidetector computed tomography (CT) over lumbar puncture (LP) when imaging for cerebral
aneurysm.
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| 3. Explain why pulmonary angiography is falling out of favor as an imaging test for pulmonary embolism.
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| 4. Describe the role of propofol in an emergency medicine practice.
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| 5. Discuss the advantages of hydroxocobalamin as an antidote to cyanide toxicity due to smoke inhalation.
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Faculty Disclosure
In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning
committee to disclose relevant financial relationships within the past 12 months that might create any personal conflicts of interest.
Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a
proprietary business or commercial interest. For this program, the faculty and planning committee reported nothing to disclose.
Acknowledgements
Dr. Jang spoke at Advances in Emergency Medicine and Primary Care, held April 18-20, 2007, in Las Vegas, NV, and
sponsored by the Olive View-UCLA Department of Emergency Medicine, and the American College of Emergency Physicians,
State Chapter of California, Inc. Dr. Braunstein was recorded at the Annual Emergency Medicine Symposium, held
December 7, 2007, in Los Angeles, CA, and sponsored by the Cedars-Sinai Medical Center, Los Angeles. The Audio-Digest
Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.
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