approach to POCUS

pocus

Point of care ultrasound (POCUS) is revolutionizing emergency medicine, providing faster and more accurate diagnosis and safer procedures. It’s a skill in both image generation and interpretation, with each scan involving 5 steps that I’ve summarized as POCUS

  • Probe position: chose probe type and starting position on patient
  • Orientation: generate image, using accoustic windows and landmarks
  • Confirm structures: identifying key structures in the area
  • Ultrasound sweep/scan: tilting or sliding the probe generating complete image of the structure
  • Significant findings: interpret normal findings, abnormal findings, false positive and false negatives

 

Below is a brief summary of the basic approach to each scan

LUNG

1) pneumothorax

  • Probe: high-frequency linear array probe, longitudinal position at highest point of anterior hemithorax
    • ptxus
  • Orientation: rib/shadow with echogenic pleural line between
  • Confirm structures: lung sliding (“ants on a log”), +/- comet tail; “seashore” sign in M mode
    • lungslide
  • Ultrasound sweep/scan: up and down one intercostal space
  • Significant findings: loss lung slide (DDx fibrosis, adhesion, bullae, right-mainsteam intubation) +/- lung point (false+ cardiac lung point
    • lungpoint

2) fluid

  • Probe: curved or phased array, longitudinal position
    • zones
  • Orientation: echogenic pleural line (antero-posterior), diaphragm (lateral)
  • Confirm structures: A lines (artifacts from normal lung field artifacts), homogenous grey superior to diaphragm laterally
    • alines
  • Ultrasound sweep/scan: examine bilateral lungs fields, and sweep diaphragm
  • Significant findings:
    • pulmonary edema: diffuse B lines: from pleura through whole lung field + move with respiration (vs Z lines: short artifact no motion)
      • blines
    • pulmonary effusion: black fluid above cephalad to diaphragm. False + pleural thickening; false – loculated effusion
      • effusion
    • consolidation: “hepatization” of lung +/- focal B line +/- effusion
      • pleural-effusion-and-pneumonia

 

 

CARDIAC

1) parasternal long

  • Probe: phased array left parasternal, probe marker to right shoulder
    • plaxview
  • Orientation: LV in greatest diameter
  • Confirm structures: near to far field RVOT –> LV –> MV –> pericardium –> descending aorta
    • plax
  • Ultrasound sweep/scan: none
  • Significant findings:
    • LV dilation > 5cm; LV contraction 1/3 (vs hyperdynamic or reduced), MV septal slap (vs minimal opening from LV dilation)
    • LVdilation
    • pericardial effusion anterior to descending aorta (vs pleural effusion posterior)
    • pce

 

2) parasternal short

  • Probe: rotate parasternal so probe marker points at left shoulder
    • psview
  • Orientation: septum
  • Confirm structures: near to far field pericardium –> RV crescent –> septum –> LV
    • sax
  • Ultrasound sweep/scan: none
  • Significant findings: pericardial effusion, RV dilation (circular shape + septal flattening), LV global function
    • rvdilation

3) apical 4 chamber

  • Probe: patient lateral decubitus, probe inferolateral to nipple/inframammary fold, pointed to right shoulder with indicator to right flank
    • apical4
  • Orientation: septum vertical and centered
  • Confirm structures: left to right screen RV (diamond shaped, < 2/3 LV, TAPSE ) –> septum –> LV
    • a4c
  • Ultrasound sweep/scan: none
  • Significant findings: RV dilation (equal LV size, reduced TAPSE)
    • a4crv

4) subxiphoid

  • Probe: curved array probe flat above umbilicus
    • subxi
  • Orientation: acoustic window through liver, looking for pericardium
  • Confirm structures: pericardium –> RV –> septum –> LV
    • subcostal
  • Ultrasound sweep/scan: sweep anterior to posterior
  • Significant findings: pericardial effusion (vs anterior fat pad disappears posterior), RV dilation (and thick wall 1cm if chronic
    • subxieffusion

 

 

IVC

  • Probe: curved or phased array, subxiphoid perpendicular pointed to patient’s back
    • ivcus
  • Orientation: through hepatic window to RA-IVC junction near hepatic vein
  • Confirm structures: IVC thin-walled compressible with respiratory variation (vs aorta), in its maximal diameter
    • ivcede
  • Ultrasound sweep/scan: into transverse plan
  • Significant findings:
    • 1 cm or >50% inspiratory decrease: hypovolemia/distributive (vs compression from ascites): CARDIOVASCULAR
    • 2cm and <50% variation: normal or increased right-side pressure (obstructive/cardiogenic): CARDIOVASCULAR

 

 

AORTA

  • Probe: curved or phased array probe, subxiphoid in transverse plan
    • abdous
  • Orientation: vertebra landmark, centre aorta, push away intestinal air
  • Confirm structures: thick-walled non-compressible aorta without respiratory variation (vs IVC)
    • aortaus
  • Ultrasound sweep/scan: slide until aortic bifurcates into iliac arteries; then longitudinal view
  • Significant findings:
    • AAA: 3cm; false + if probe not perpendicular, false – if measuring inside hematoma instead of wall to wall
    • aaa
    • dissection: intimal flap

 

 

ABDOMINAL

  • Probe: curved array probe, longitudinal plane in posterior axilllary line, transverse plan suprapubic
    • flank
  • Orientation: locate kidney
  • Confirm structures: RUQ hepatorenal space, LUQ diaphragm-splenic space, suprapubic rectovesicular/rectouterine space
    • hepatorenal
  • Ultrasound sweep/scan: sweep spaces
  • Significant findings: free fluid
    • freefluid
    • false + acites/bladder rupture, perinephric fat/fluid
    • false – slow bleed, encapsulated or retroperitoneal bleed, adhesions

 

 

PELVIC

  • Probe: curved array probe suprapubic longitudinal
    • pelvis
  • Orientation: through full bladder acoustic window into uterus in its largest view
  • Confirm structures: endometrial stripe (vs vagina)
    • uterus
  • Ultrasound sweep/scan: sweep through uterus, then rotate into transverse plane and sweep again
  • Significant findings:
    • IUP: 1) echogenic decidual reaction containing 2) anechoic gestational sac containing 3) echogenic yolk sac +/- 4) FHR
      • iup
    • miscarriage: CRL 5mm without FHR; gestational sac 20mm without embryo (blighted ovum, DDx pseudogestional sac in ectopic)
    • ectopic: interstial pregnancy, tubal pregnancy, pseudo-gestational sac, empty uterus, +/- free fluid
    • molar pregnancy: “cluster of grapes”

 

 

RENAL

  • Probe: curved array probe longitudinally in posterior axillary line
    • renalus
  • Orientation: liver/spleen acoustic window and landmark
  • Confirm structures: capsule, cortex, collective system
  • Ultrasound sweep/scan: sweep in both axes, compare both sides
  • Significant findings:
    • stone: echogenic stone + shadow
    • complications: capsule gas (pyonephrosis) or perinecphric fluid at risk of abscess formation
      • perinephric
    • hydro: dilate calyces –> blunt pyramid –> obliterate cortex
      • hydro
      • DDx: stone, external compression (mass, AAA), distal bladder obstruction (bilateral hydro)

 

 

GALLBLADDER

  • Probe: curved array probe longitudinally in epigastrium
    • OLYMPUS DIGITAL CAMERA
  • Orientation: slide laterally until cystic structure comes into view, through acoustic window of liver
  • Confirm structures: gallbladder cystic structure, pear shaped (vs IVC, portal vein, duodenum, cysts), connected by MLF to portal vein (“exclamation point”)
    • gbexclamation
  • Ultrasound sweep/scan: sweep through both axes
  • Significant findings:
    • stone: echogenic + shadow + mobile (unless stuck in neck); wall-echo-shadow if filled with stones
    • DDx: polyp (no shadow, non mobile), sludge (no shadow), gas (dirty shadow), edge artifact
    • cholecystitis: sonographic Murphy, pericholecystic fluid, wall thickness >3mm (DDx ascites, CHF, hypoalbumin, hepatitis, pancreatitis)
    • chole

 

In summary:

POCUS

 

 

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