• Category III: eGFR < 30 or serum creatinine > 2.0: If an alternative study is not possible, the increased risk of CIN versus the benefits of intravenous contrast for the individual patient should be discussed with the referring clinician and documented in the medical record.
Diabetic Patients Taking Metformin (Glucophage)
If renal insuciency develops after contrast administration, patients are at increased risk of lactic acidosis. Patients taking met-formin should not take it for 48 hours after intravenous contrast administration.
Chronic Hemodialysis Patients (Renal Failure)
• No need for urgent dialysis
• Limit amount of contrast to reduce osmotic load
Moderate Reaction
• Activate medical response team
• Supplemental oxygen
• Epinephrine 1:1,000 IM 0.3–0.5 ml every 5–15 minutes (begin as promptly as possible)
• Diphenhydramine 50 mg IV
• Metaproterenol or Albuterol inhaler for bronchospasm
Severe Reaction
• Activate medical response team
• Epinephrine 1:1000 IM 0.3-0.5 ml
every 5-15 minutes (begin as promptly as possible)
• If response to IM epinephrine is inadequate, give epinephrine IV infusion, 2-10 micrograms/min
• Supplemental oxygen
• Nebulized Metaproteranol or Albuteral for bronchospasm
• Consider endotracheal intubation for airway edema/respiratory failure
• Normal saline bolus 1-2 liters
Hypotension and Bradycardia
• Trendelenberg
• Normal saline bolus 1-2 liters
• Atropine IV 0.6-1 mg to total dose of
2 mg (adults)
Seizure
• Protect airway
Contrast-Induced Nephropathy (CIN)
Risk Factors
Patients with certain underlying conditions are more likely to suer contrast-induced renal injury and should have estimated glomerular filtration rate (eGFR) or serum creatinine levels prior to receiving intrave-nous contrast in order to better assess their risk. This group includes patients with:
• History of renal disease, prior kidney surgery, transplant, or single kidney
9
2
Br
ain
aneurysms, arteriovenous malformations (AVM), vascular injuries, and venous or cavernous sinus thrombosis. Conventional angiography is usually reserved for preop-erative aneurysm or AVM evaluation, and endovascular therapy. CT perfusion imag-ing can be useful in identifying the location and extent of vascular compromise in pa-tients with acute stroke symptoms.
On older scanners, brain CT is usually obtained nonhelically to avoid artifacts. Newer multislice CT systems permit ad-equate imaging of the brain in three planes as well as simultaneous acquisition of high-resolution images of the face and cer-vical spine in patients with acute head and neck trauma.
Checklist
• Scalp
• Skull
• Epidural space (potential)• Subdural space (potential)
• Dural sinuses and reflections
• Cortex
• Subcortical white matter
• Basal ganglia
• Ventricles
• Cisterns
• Cerebral vessels
• Pituitary and sella turcica
• Skull base
• Orbits
• Sinuses
• Facial bones
◆Approach
Noncontrast head CT is one of the most frequently ordered emergency studies. Common indications include headache, suspected cerebral infarct or intracerebral hemorrhage, altered mental status, and trauma.
Images should always be evaluated with windows and reconstruction algorithms optimized for brain, subdural hematoma, and bone. In trauma, multidetector CT from the skull base to the upper thoracic spine can be acquired to image the head, cervical spine, face, and skull base in a single scan. Thin-section reconstructions and reformations in multiple planes or three-dimensional surface renderings can then be extracted from the imaging data obtained.
Noncontrast CT is the initial study for detection of hemorrhage, infarct, intra-cranial masses, traumatic injuries, and assessment of overall brain volume and quality. A normal noncontrast CT excludes most emergent and surgical conditions. MRI with gadolinium is more sensitive for detection of infectious or neoplastic con-ditions including metastases, cerebritis, meningitis, and leptomeningeal neoplasm, but it is not typically necessary for acute management. Contrast CT is an alternative if MRI is not available or contraindicated in a particular patient.
Cerebral CT angiography, in which im-ages are obtained during the arterial or early venous phase of contrast enhance-ment, has largely replaced catheter angi-ography for primary detection of cerebral
10Emergency Imaging
Fig. 2.1a–f Cerebral anatomy. F: Frontal lobe. P: Parietal lobe. T: Temporal lobe: O: Occipital lobe. Cer: Cerebellum. CS: Centrum semiovale. CR: Corona radiata. CC: Corpus callosum. Th: Thalamus. Pu: Puta-men. C: Caudate head. Op: Frontal operculum.
a
b
c
d
e
f
11
2Brain
Anatomy
Eective description and analysis of cere-bral pathology requires knowledge of vis-ible cerebral structures (lobes, basal nuclei, ventricles), vascular territories, and arte-rial and venous anatomy. Cerebral anatomy is shown in Fig. 2.1. Cerebral vascular ter-ritories and anatomy are seen in Fig. 2.2.
◆ Clinical Presentations and Dierential Diagnosis
Clinical Presentations and Appropriate Initial Studies
Trauma
Noncontrast head CT is indicated. Head or neck CT angiography should be considered if injury mechanism or initial findings indi-cate a likely cervical vascular injury.
• Skull fracture
• Epidural hematoma
• Subdural hematoma
• Venous epidural hematoma
• Traumatic subarachnoid hemorrhage
• Contusion
• Diuse axonal injury
•