Ultrasound Guided Interventional Techniques (Ch. 18)

why use US for procedures?

• high resolution, imaging frame rate, diagnostic accuracy

• enhances transducer design (small footprint)

• new technology: compound imaging and fusion technology (CT on US)

• versatile needle guide attachments that offer multiple angle accessibility and accurate needle placement (shorter distance and least angle desired)

• less costly and minimally invasive

• continual real-time visualization of needle

• various patient positions and procedural approaches can be used

• physical presence of procedure team during entire procedure

• portable

• no use of radiation

• shorter procedure time

informed consent

• necessary for any procedure that is considered experimental, invasive, or involves substantial risk

• patients’ agreement to allow something to happens after full disclosure of the facts needed to make the decision

• by signing Informed Consent, the patient/patient’s representative indicates that:

  • patient has been informed about the procedure and its sequence

  • patient has been informed of all the risks and benefits of te procedure

  • potential complications

  • responsible alternatives to the procedure and their risks and benefits

  • patient consents to the procedure of treatment

for consent to be valid…

• patient must be legal age and mentally competent

• patient must offer consent voluntarily

• patient must be adequately informed about the medical care being recommended

• patient must not be persuaded

sterile set-up

• usually established using a sterile drape that is free of germs

• only sterile items are used in the sterile field

• must be continually monitored

• a sterile person can only touch what is sterile

• unsterile persons cannot reach over or above a sterile field

• confirm that it is sterile:

  • is the packaging expired?

  • is it dirty or wet?

  • has it been opened?

• gowns are considered sterile on the sleeves and the front from the waist up

  • sterile gloves must be kept in sight and above waist level

  • persons in sterile gown/gloves must pass each other back to back

• sterile materials must be kept dry

  • sterile field becomes wet it must be re-sterilized or discarded

• things that are considered unsterile:

  • below the level of the table/waist, as well as the undersurface of the drape; any item that falls below this level is considered contaminated

  • the back of the gown and area below waist

  • 1 inch border around the sterile field is not considered sterile

how to gown another person

1. sterile person picks up the gown by the neckband, holds it at arm’s length, and allows it to unfold

2. gown is held by the shoulder seams with the outside facing the sterile person

3. sterile gloves are protected by placing both hands under the back panel of the gown’s shoulder

4. arms are slipped into the sleeves in a downward motion, sliding the gown up to the mid-upper arms

5. nonsterile circulator pulls the gown up and fastens the back and waistband of the gown

6. gently pull the cuff back over the person’s hands, being careful that your gloved hands do not touch the bare hands

what procedures can be done with US guidance?

• biopsies of various masses in the neck, chest, abdomen, retroperitoneum, pelvis, and MSK system

• aspirations/drainage of abscess or fluid collections (percutaneous)

• paracentesis and thoracentesis

• peripheral, subclavian, or jugular line placement

• IVs, joint injections

• ablations

• elastography

how to find the needle

• visualization of needle is most important part of procedure

• if needle is not visualized, transducer should be moved, not the needle

• needle must be in the center of the transducer

• TIP: the more perpendicular the sound beam is to the needle, the more sound will return → better reflection from the needle

• providers have 2 techniques to introduce needles and devices into patients

  • free-hand

  • mechanically guided technique

free-hand technique

• MC used

• advantage

  • good when accessing superficial structures

• disadvantages

  • difficult to use during renal biopsy

  • potentially longer procedure time

  • challenging to access deep lesions

needle guides

• mechanically guided and attaches to transducer

• depicts a path on the US machine as a single line or two parallel lines

• may offer choices of angles

• keeps the needle aligned with the beam for continuous needle visualization

what technique is being used?

mechanically guided technique

ablations

• radiofrequency, cryoablation, laser, microwave, and high intensity focused ultrasound (HIFU)

• destroys cancerous cells tissue via cold or hot temperatures while maintaining the surrounding normal tissue

• non-surgical patients

• unresectable masses

• during the procedure: as cells are destroyed, gas/microbubbles (nitrogen) is released

• SONO:

  • hyperechoic echoes=confirmation of tx

elastography

• liver and breast

• eval. for fibrosis

• evaluation of tissue stiffness

• reduces the need for core biopsies

fusion imaging

• involves important a CT or MRI scan directly onto the US machine

  • side by side images

  • superimposed/overlapping images

• as the US machine moves, so does the other imported modality images

indications for a biopsy

• confirm malignancy (MC)

• need to differentiate metastatic vs second primary mass

• determine the cause of mets in a patient with known primary malignancy

• to differentiate recurrent tumor from therapy scarring

• differentiate malignancy from inflammatory or infectious dz

• determined lymphadenopathy from lymphoma

• to characterize a benign mass

• to obtain a sample of parenchyma in an organ to determine the progression of dz

• abnormal lab values may warrant a biopsy

contraindications for a biopsy

• lack of safe needle path

• uncooperative patient

• patients with a bleeding disorder/uncorrectable coagulopathy

  • ex. warfarin/Coumadin, heparin, aspirin therapy (increase risk of excessive bleeding during or after invasive procedure)

3 pathways in the blood clotting process

• 3 pathways: intrinsic, extrinsic, and common

• two blood tests used to evaluate these pathways:

  • partial thromboplastin time (PTT)

    • measures how long it takes blood to clot and evaluates the intrinsic and common pathways

    • normal values are 25-35 seconds

  • prothrombin time (PT)

    • measures clotting in extrinsic pathway and helps determine bleeding or clotting risk during or after surgery

    • normal values are 11-13 seconds

• because PT results can vary between laboratories, a standardized measurement called international normalized ratio (INR) was developed

  • 0.8-1.1 (unitless)

if clotting values do not return to normal, patients may be given… (2)

fresh frozen plasma (FFP) or vitamin K to help improve blood clotting.

gauge (G) and length

• the higher the number, the smaller the diameter

• “20, 15,” or “20 × 15” = 20G needle and 15cm in length

type of procedure: fine needle aspiration (FNA)

• uses a 20-25G needle with cutting tip, such as Fransen, Chiba, or spinal needle

• uses a thin needle to collect cells from a mass for cytology evaluation

• if sample is too small, suction technique may be used:

  • a syringe and tubing are attached to the needle

  • this suction helps draw cells into the needle during sampling

• reduces potential trauma to cells and decrease the amount of blood retrieves as well

• FNA helps:

  • reduce trauma to cells

  • decrease the amount of blood retrieved

  • decrease background blood contamination

  • improve specimen quality for cytology

type of procedure: core biopsy

• uses a 14-20G needle (larger than FNA)

• uses a spring-loaded biopsy gun to obtain a core (small cylinder) of tissue for histologic analysis

• when the biopsy gun is fired:

  • the cutting needle rapidly advances (“throws” forward),

  • cuts a tissue sample,

  • and stores the specimen in the “deposit slot” on the inner needle

• “throw length” refers to the…

  • distance the needle advances when fired, and

  • length of the tissue specimen obtained

• pay attention to how many “throws” (count them)

type of procedure: fluid or abscess collections

• needle guide used, especially when…

  • the collection is small

  • difficult to access

  • multiloculated

  • near important structures

• 20-22G needle (for small fluid samples)

• thicker fluid may require a lower G needle (small samples)

type of procedure: percutaneous drain placements

• large abscesses or persistent fluid collections may require a percutaneous drainage catheter to remain in place for continuous drainage

• pigtail catheter is MC type

• the catheter is…

  • connected to a collection bulb or drainage canister

  • sutured to the skin (to keep it secure)

type of procedure: paracentesis and thoracentesis

• paracentesis=drainage from peritoneal cavity (ascites)

  • ascites MC in RUQ and pelvis

• thoracentesis=drainage from pleural space (pleural effusion)

• lab orders

  • coagulation studies (PT/PTT/INR), platelet counts, and medication history (anticoagulants such as heparin or Coumadin) are reviewed to help reduce risk of bleeding complications during drainage procedures

• 20-22G needles used

• thicker fluid may require a lower G needle (small samples)

• large-volume paracentesis or thoracentesis require a centesis catheter (a 1-liter vacuum bottles connected to the catheter tubing)

• prepared sterile tray is set up before procedure

• transducer should be placed parallel to pt.’s skin (do not rock the probe)

cytopathology

• some US departments work with cytopathologist during biopsy

• on the spot evaluation/confirmation of diagnosable specimen

• during the procedure:

  • usually 1-3 passes are performed

  • specimen is transferred onto sterile slides, then the slides are quickly stained in the US room

  • slide evaluation takes 3-5 minutes per pass or group of passes

• benefits:

  • provide immediate confirmation that a specimen is diagnostic

  • increase the % of successful biopsies

  • helps minimize unnecessary passes

  • reduce overall procedure time

intraoperative ultrasound (IOUS)

• real-time

• used to facilitate surgery; aid in decision making; surgical planning

• mobile US unit with specialized transducers that will fit through a surgical incision

• uses a sterile cover

• natural moisture used to couple transducer to organ of interest or warm saline us used

• to sterilize the transducer:

  • soak in alcohol (30 minutes)

  • hydrogen peroxide gas (2 hours)

  • ethylene oxide gas (24 hours)

what is intraoperative US used for?

• localization of lesions

• determining lesion resectability

• confirmation of blood flow

• tumor thrombi and vascular invasion

• relationship of lesions to vascular anatomy

• surgical procedures of the brain, spinal cord, liver, GB, kidney, or pancreas

  • liver: the falciform ligament is resected and pulled down by the surgeon so the radiologist can scan the liver

  • kidney: sometimes removed from the renal fossa

role as sonographer: pre-procedure documentation

• evaluate medical record for appropriate history, lab values, and other imaging studies

• located and take images of the pathology of interest and best path approach

  • measure distance from skin to area of interest (to know length of cath. needed)

• knowledge of how breathing affects movement of the mass

• obtain informed consent

• comfort/coach the patient and create the sterile field

• set-up procedure workspace (trays, Dr. gloves, lab requisitions, proper lab tubes, patient labels, etc.)

• have prior images on computer in procedure suite

• radiology nurse monitors vital signs by ECG and pulse oximetry

role as sonographer: just before and during procedure documentation

• “time out” (a pause before the procedure) to confirm the procedure, CORRECT patient, and patient understands what is going on (images can be taken as confirmation)

  • document by taking an image of the time the time-out took place

• operate the US machine especially with free hand technique

  • focus on needle tip (SONO: echogenic dot)

  • document the number of samples (throws/passes) taken - FNA, progressive appearance of the location being drained, and any other images requests

• be available for placement of prove cover, additional supplies that are needed, labeling of specimen, and gathering specimen

• radiology nurse monitors vital signs by ECG and pulse oximetry

role as sonographer: post-procedure documentation

• take after-procedure images (mass, fluid area, etc.) showing any change in shape or size of the location

• evaluation of specimen (cloudy, bloody fluid, stinky, etc.)

• accurate count of specimen (ex. 2 advances)

• cleaning the US suite (sharps, trash)

• sending specimens to labels with properly documented lab orders/requisitions

  • your initials, location specimen came from, date, and time

• radiology nurse monitors vital signs by ECG and pulse oximetry

post-procedure care, discharge, and complications

• ice packs may be provided

• post procedural recovery time

• vital signs obtained before discharging patient

• minor complications:

  • post-procedural pain

  • hematoma

  • vasovagal reaction

• severe complications (rare):

  • hemorrhage

  • pneumothorax

  • pancreatitis

  • infection

  • death

emergent procedures

• assessing for blunt trauma via FAST (focused assessment with sonography for trauma) exam

  • perihepatic and hepatorenal space (RUQ)

  • perisplenic (LUQ)

  • pelvis: cul-de-sac (RLQ and LLQ)

  • pericardium

• ectopic pregnancy

• incarcerated or strangulated hernia

• testicular torsion

• intussusception

• pyloric stenosis

• appendicitis

• avascular transplant

• aortic dissection

• pericardial tamponade (fluid fills pericardium → compression of rt ventricular wall)

• ruptures AAA

• pericardial effusion