ED Guidelines & Protocols

The clinical guidelines and references provided on this website are developed by the department of emergency medicine at Maine Medical Center. The information is believed, but not guaranteed to be correct. It reflects our expert opinion and is not necessarily applicable to all institutions. It is intended to be a reference for clinicians caring for patients and is not intended to replace providers’ clinical judgment. For comments or suggestions please contact Jeff Holmes, M.D.

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Regional Anesthesia Clinical Resource

Regional Anesthesia - Local Anesthetics

The Regional Anesthesia Clinical Resource site was created by Doug Dillon, M.D., PGY-3, for the promotion of regional anesthesia in the emergency department to alleviate pain during laceration repair and fracture/dislocation reductions.

Regional Anesthesia - The Digital Block

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The digital nerve block is an excellent block to use when tending to lacerations on fingers or toes. Anatomy: The common digital nerves are derived from the median and ulnar nerves and divide in the distal palm into paired palmar branches. The nerves travel on either side of the flexor tendon sheath of each finger and innervate the lateral and palmar aspect of each finger. The smaller dorsal digital nerves, derived from the radial and ulnar nerves, run on the dorsal lateral aspect of each finger and supply sensation to the back of the finger. Distribution of anesthesia: The digital nerve block provides anesthesia to the entire digit. Technique: The surgical field should be prepared as close as possible to the metacarpophalangeal joint. While the procedure can be performed from either the volar or dorsal aspects of the digit; the later is less painful. Raise a wheal of anesthesia in the subcutaneous space and direct the needle palmar on both the medial and lateral aspect of the first phalange. To insure inadvertent vessel puncture, aspirate as you insert the needle. Apply one to two milliliters of anesthesia slowly as you are withdrawing the needle. Allow five to ten minutes for full anesthesia with lidocaine and fifteen to twenty minutes with bupivacaine. If this procedure does not provide complete anesthesia, more anesthetic may be needed by either reapplication of the digital nerve block or performing a transthecal digital nerve block.

Transthecal Approach

Watch the Video

The transthecal approach utilizes the flexor tendon sheath to apply anesthetic to the digital nerves. This procedure can be performed in addition to or as an alternative to a digital nerve block. Identify the flexor tendon sheath of the digit to be blocked at the palmar aspect of the hand. Have the patient flex the finger to be blocked if possible. At the level of the distal palmar crease, puncture the skin at a forty-five degree angle until the pop of the flexor tendon sheath is felt. If this "pop" is not felt, continue to insert the needle, aspirating as you inject, until the needle contacts bone. Withdraw the needle two to five millimeters and inject 2 to 3 ml of anesthesia. When the needle is in the flexor tendon sheath, the anesthesia should flow easily. As before, allow five to ten minutes for full anesthesia with lidocaine or fifteen to twenty minutes with bupivacaine.

Pitfalls: Not performing a transthecal block with a failed dorsal digital block. Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Hand

General: These blocks are excellent block for lacerations, puncture wounds or bony dislocations of the hand. They can be used in parts or in combination to provide anesthesia to the entire hand. When performing a complete hand block, the ulna, median and radial nerves should be blocked.

Ulnar Nerve

Watch the Video

Anatomy: Identify the flexor carpi ulnaris and ulnar artery by having the have the patient deviate their hand in an ulnar direction at the wrist (giving the thumbs up). The flexor carpi ulnaris is the most medial (ulnar) tendon. The ulnar artery can be palpated just medial and dorsal to the tendon. The nerve lies between the artery and the flexor carpi ulnaris tendon.
Innervation: The ulnar nerve innervates the flexor pollicis brevis, abductor pollicis, palmaris brevis, abductor digiti minimi, flexor digiti minimi opponens digiti minimi, the medial two lumbricals and all the interossei muscles. Distribution of anesthesia: This procedure provides anesthesia to the entire fifth digit, half of the fourth digit and the medial aspect of the hand and wrist. Technique: The surgical field should be prepared just proximal (1-2 cm) to the most distal wrist crease. Raise a wheal of anesthetic in the subcutaneous space and insert the needle under the flexor carpi ulnaris one centimeter just palmar to the ulnar styloid. If blood is aspirated, withdraw the needle a few millimeters and aspirate again, the nerve is more superficial from the injection point. Inject approximately 5 to 7 milliliters of anesthetic. To block the cutaneous branches of the ulnar nerve, inject 3 to 5 milliliters of anesthetic just above the tendon of the flexor carpi ulnaris.
Pitfalls: If bone is struck withdraw the needle and direct it more palmar. Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Median Nerve

Watch the Video

Anatomy: Identify the flexor carpi radialis and the palmaris longus tendons at the palmar aspect of the wrist. The palmaris longus, if present, is usually the more prominent of the two tendons and can be identified by having the patient flex at the wrist. To help identify the flexor carpi radialis, have the patient flex and abduct the wrist. The median nerve is lateral (radial) to the palmaris longus tendon and between the palmaris longus and the flexor carpi radialis.
Innervation: The median nerve provides motor innervation to the thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) and the first and second lumbricals.
Distribution of anesthesia: The median nerve provides sensory to the lateral three and a half digits except the dorsal aspect of the thumb, and the corresponding area of the palm.
Technique: The surgical field should be prepared across the entire volar surface of the wrist at the proximal palmar crease. Raise a wheal of anesthetic in a subcutaneous space and insert the needle until it pierces the deep fascia. If the "pop" of the deep fascia can not be felt, continue to insert the needle until it contacts the bone. Withdraw the needle 2 to 5 millimeters and inject 5 to 7 milliliters of anesthetic. A fan like technique is recommended to ensure complete anesthesia of the median nerve. This can be accomplished by reinserting the needle in the same position approximately 30 degrees medial and 30 degrees lateral and injecting 2 to 5 additional milliliters of anesthetic. The palmar branch of the medial nerve is quite superficial and can be blocked by withdrawing the needle to the subcutaneous space and injecting 3 to 5 milliliters of anesthesia.
Pitfalls: Avoid injecting too distal within the carpal tunnel which may exacerbate any carpal tunnel syndrome. Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Radial Nerve

Watch the Video

Anatomy: Locate the radial styloid at the proximal portion of the anatomic snuff box. The anatomic snuff box is just distal to the radial styloid and formed by the extensor tendon of the palmaris brevis and longus. The superficial branch of the radial nerve runs just above the styloid process of the radius. It gives off digital branches to the dorsum of the thumb, index finger and lateral half of the middle finger. Several branches run over the anatomic snuff box. The nerve divides into two major branches about two finger breadths proximal to the distal wrist crease (or anatomical snuff box).
Distribution of anesthesia: The radial nerve provides sensory innervation to the dorsal lateral half of the hand and the dorsal aspect of the thumb. The radial nerve provides no motor innervation to the intrinsic muscles of the hand however; it does provide innervation for all of the extensor muscles in the posterior forearm.
Technique: The surgical field should be prepared across the entire dorsal surface of the wrist, including the radial styloid and the anatomic snuff box. Raise a wheal of anesthesia in the subcutaneous space and inject 5 to 7 milliliters of anesthetic just above the radial styloid, aiming the needle first medially and then laterally.
Alternative method: Using the non-injecting hand, straddle the anatomic snuffbox with the index and middle fingers and press them firmly against the radius.Slowly inject the anesthetic which will spread across the path of the nerve.
Pitfalls: The distribution of the radial nerve is less predictable; therefore, a generous amount of anesthesia should be injected. Intraneural injection will cause significant, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

   = Radial Nerve
   = Median Nerve
   = Ulnar Nerve

Reg_Anesthesia_Hand_Top_sm 

Reg_Anesthesia_Hand_Top_sm

Foot

Ankle Block General: An ankle block is essentially a block of four branches of the sciatic nerve (deep and superficial peroneal, tibial and sural nerves) and one cutaneous branch of the femoral nerve (saphenous nerve). This is an excellent block to use as in combination or in part for lacerations, fracture reductions, and exploring wounds. Although there is some overlap, sensory innervation in the foot can be broken down into posterior and anterior nerves. Sole of the foot - The tibial and sural nerves provide sensory innervation to sole of the foot. Dorsum of the foot - The superficial peroneal, the deep peroneal and the saphenous nerves provide sensory innervation to the dorsum of the foot.

Deep Peroneal Nerve

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Anatomy: The deep peroneal nerve lies in the groove between the extensor hallucis longus and the tibialis anterior tendon. The hallucis longus can be located by having the patient flex and extend the big toe. The tibialis interior can be located by having the patient dorsi flex the foot and invert the ankle. The injection site should be at the level of the superior malleolus and between the two tendons.
Distribution of anesthesia: The deep peroneal nerve provides sensation to the web space between the first and second toe and a small area just proximal to the first and second toe on the plantar aspect of the foot.
Technique: The surgical field should be prepared across the anterior surface of the ankle between the superior aspect of the medial and lateral malleoli. Raise a wheal of anesthesia in the subcutaneous space and direct the needle between the tendons of the hallucis longus and the tibialis anterior at the level of the superior malleoli. Insert the needle until it is deep to the tendons or bone is struck. Inject approximately 5 milliliters of anesthetic. Withdraw the needle and redirect thirty degrees laterally and then thirty degrees medially and provide an additional 3 to 5 ml of anesthetic. If anesthesia in the saphenous distribution is also desired, bring the needle back to the level of the subcutaneous tissue and redirect it medially towards the medial malleolus. Inject an additional 5 ml in the subcutaneous space. This will block the saphenous nerve.
Pitfalls: Avoid inadvertent saphenous vein puncture. Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Posterior Tibial Nerve

Watch the Video

Anatomy: The posterior tibial nerve runs just behind the medial malleolus, and just posterior to the posterior tibial artery. Like the deep peroneal, the posterior tibial nerve is deep to the fascia. The posterior tibial nerve can be located just posterior to the medial malleolus just superficial to the artery.
Distribution of anesthesia: The posterior tibial nerve provides the majority of the sensation to the plantar aspect of the foot with minor contributions from the deep peroneal and sural nerve. The posterior tibial nerve also provides sensation to the heel of the foot.
Technique: The surgical field should be prepared posterior to the medial malleolus. Identify the posterior tibial artery by palpating the artery posterior to the medial malleolus. Insert the needle just posterior to the artery until it penetrates the deep fascia. If the pop of the deep fascia cannot be felt, continue inserting the needle until it contacts bone. Withdraw the needle 2 to 5 millimeters and inject 3-5 5 milliliters of anesthesia. To increase the odds of a successful block, place an additional 3 to 5 milliliters lateral and medial to the original injection site.
Pitfalls: Intraneural injection will cause excruciating pain with injection, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.
General: The superficial peroneal, sural, and saphenous nerves are located in the subcutaneous tissue encircling the ankle. These nerves branch out and anastomose extensively; therefore they do not have a single point that can be consistently anesthetized. A field block in the subcutaneous tissue is used to anesthetize these nerves.

Superficial Peroneal Nerve

Watch the Video

Anatomy:
The superficial peroneal nerve is superficial and runs along the anterior lateral portion of the ankle. It can be blocked by subcutaneous injection between the lateral malleolus and the tibialis anterior tendon.
Distribution of anesthesia: This nerve provides sensation to the dorsal lateral aspect of the foot.
Technique: Identify the tibialis anterior tendon by having the patient dorsiflex the foot and inverts the ankle. The most prominent tendon should be the tibialis anterior. The surgical field should be prepared between the tibialis anterior tendon and the lateral malleolus at the level of the superior malleoli. Inject anesthesia in the subcutaneous space from the tibialis anterior tendon to the superior portion of the lateral malleolus. 

Face

Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Sural Nerve

Watch the Video

Anatomy:
The sural nerve is quite superficial and can be blocked by anesthetizing the subcutaneous tissue from the superior portion of the lateral malleolus to the Achilles tendon.
Distribution of anesthesia: The sural nerve provides sensation to the lateral aspect of the ankle and a small area on the plantar lateral aspect of the foot.
Technique: The surgical field should be prepared between the Achilles tendon and the lateral malleolus at the level of the superior malleoli. Inject anesthesia in the subcutaneous space from the superior portion of the lateral malleolus to the Achilles tendon.
Pitfalls: Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Saphenous Nerve

Watch the Video

Anatomy: The saphenous nerve is a subcutaneous nerve that can be blocked by injecting anesthesia from the superior medial malleolus to the tibialis anterior tendon. Use caution around the saphenous vein.
Distribution of anesthesia: This nerve provides sensation to the medial aspect of the ankle.
Technique: Identify the tibialis anterior tendon and the superior portion of the medial malleolus. The surgical field should be prepared between the tibialis anterior tendon and the medial malleolus at the level of the superior malleoli. Inject anesthesia in the subcutaneous space from the tibialis anterior tendon to the superior portion of the medial malleolus.
Pitfalls: Puncture of the saphenous vein. Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

   = Deep Peroneal Nerve
   = Posterior Tibial Nerve
   = Superficial Peroneal Nerve
   = Sural Nerve
   = Saphenous Nerve

Reg_Anesthesia_Hand_Top_sm

Reg_Anesthesia_Hand_Top_sm 

Reg_Anesthesia_Hand_Top_sm

Facial Blocks

General: Facial blocks provide anesthesia with little to no distortion of the anatomy, thus are ideal for repairing lacerations on the face; where precise alignment of tissue structures is desirable. Facial blocks also provide excellent anesthesia for abrasions on the face/forehead.

Watch an Introduction Video


This video is identifying nerve locations on the face.Remember that the supraorbital, infraorbital and mental nerves all line along an imaginary vertical line drawn through the pupil. When injecting in the mouth, provide topical anesthetic, retract mucosa to enhance vision & minimize needle insertion trauma, dry the injection site, and penetrate mucosa using distracting pain to minimize the pain of injection.

Supraorbital and Supratrochlear Nerves

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Anatomy: The supraorbital nerve exits the superior surface of the optical rim from the supraorbital foramen. The Supratrochlear nerve exits out of the medial portion of the orbital rim just superior and medial to the lateral canthus.
Distribution of anesthesia: Blocking both of these nerves will provide anesthesia to the entire forehead up to the vertex of the scalp.
Technique: Prep and drape the area just superior to the eyebrow(s). Inject topical anesthetic into the subcutaneous space in a plane just superior to the eyebrow from the midline to the lateral edge of the orbit.
Pitfalls: Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Infraorbital Nerve

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Anatomy: The infraorbital nerve exits the infraorbital foramen just inferior to the anterior portion of the optic rim, and just cranial / superior to the first maxillary pre molar (just posterior to canines). The maxillary premolars can be identified by remembering that the Central incisors are your front two teeth, Lateral incisors are just that, followed by the Canines, two Premolars, and finally three Molars.
Distribution of anesthesia: Infraorbital nerve provides sensation to the lower lid, medial cheek, the side of the nose, and the upper lip.
Technique: Use topical anesthesia to first anesthetize the mucosa. This is best performed using two cotton swaps dipped in topical anesthesia and placed just superior to the first maxillary pre-molar. With the non-injecting hand retract the mucosa by placing the index and middle fingers on the inferior optic rim and retracting the upper lip with the thumb. Dry the mucosa to enhance vision and minimize needle insertion trauma. Penetrate the mucosa just superior to the first maxillary pre-molar. Insert the needle cranially between the cheek and gingival until half the distance to the optic cup. Inject approximately 3 to 5 ml of anesthesia.
Pitfalls: Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Mental Block Nerve

Watch the Video

Anatomy:
The inferior alveolar nerve gives rise to the mental nerve which exits the mental foramen.
Distribution of anesthesia: The mental nerve block provides anesthesia to the labial mucosa, gingiva and the lower lip adjacent to the incisors and canines.
Technique: Identify the first and second pre-molars on the lower jaw. Retract the lip, apply topical anesthetic, and dry. Advance the needle inferiorly into the mucosal fold adjacent to the first and second pre-molar. At approximately one centimeter, inject 3 to 5 ml of anesthesia.
Pitfalls: Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Inferior Alveolar Nerve

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Anatomy: The inferior alveolar nerve arises from the mandibular division of trigeminal (V3). Identify the mandibular sulcus the cornoid notch and the pterygomandibular raphe. The failure rate for injection is 15% to 20% in the most experienced hands, and the rate of positive blood aspiration is 10% to 15%.
Distribution of anesthesia: The inferior alveolar nerve provides anesthesia to all the lower teeth and gums from the retromolar region to the midline as well as the anterior labial and lingual areas. The lingual nerve is usually affected by the inferior alveolar block; therefore patients may experience difficulty speaking after this procedure.
Technique: Retract the lip, apply topical anesthetic and dry the mucosa. With the non-injecting hand, place the thumb inside the mouth in the coronoid notch of the ramus. The needle should be directed from the contralateral lower incisor to the medial aspect of the ramus. Insert the needle 1 to 2 centimeters posterior and medial to the thumb in the raphe. Advance the needle until you gently tap bone and withdraw approximately two to three millimeters. Inject approximately 2 to 3 ml of anesthesia slowly.
Pitfalls: Intraneural injection will cause significant pain, therefore withdraw the needle a few millimeters and continue injecting the anesthetic.

Combat Application Tourniquets

C-A-T® Tourniquet Buddy-Aid Arm Application Tutorial





C-A-T® Tourniquet Buddy-Aid Leg Application Tutorial


Ultrasound Guided Nerve Blocks

Fascia Iliaca Compartment Block

Fascia Iliaca Compartment Block Quick Refresher

Ulnar Nerve Block

Median Nerve Block

Radial Nerve Block

Limited Bed Transvaginal Ultrasound

The purpose of this content is to provide Emergency Medicine clinicians with an online instructional resource for limited bedside transvaginal ultrasound. This procedure is indicated for any woman in early pregnancy who presents to the ED with abdominal pain and/or vaginal bleeding. The teaching module will take users through the setup, technique, and findings in early pregnancy.

For more information, please contact Liz Andrada.

Gestation 

4-5 weeks gestation

The gestational sac appears; this is the first sonographic finding of an IUP.

  • It is an echogenic ring, with a tiny central hypoechoic area, only a few millimeters in size.
  • It grows about 1 mm per day.
  • The menstrual age in days can be estimated by adding 30 days to the sac size in mm.
  • True gestational sacs implant into the endomterial lining and are eccentric to the endometrial canal; it does not deform the midline stripe
  • Can be confused with a pseudogestational sac (click to view image), therefore it is not an accurate indicator of an IUP.

5 week gestation

  • The gestational sac can be identified in the uterine fundus as an oval or circular anechoic structure. An echogenic ring will develop around it, known as the double decidual sign or “double ring sign”.
  • Pseudosacs do not show a double decidual sign, however this stage is still inadequate to be called a definitive IUP.
  • Click to view image
  • Watch the Video

5-6 weeks gestation

  • The yolk sac becomes visible. It is the first structure to be seen inside the gestational sac.
  • It is a symmetric circular thin walled echogenic structure at the edge of the gestational sac.
  • The yolk sac is a critical landmark identifying a true gestation sac, and is the first definitive evidence of IUP.
  • Click to view image
  • Watch the Video

6 week gestation

  • The embryo or “fetal pole” is first seen as a thickening on the margin of the yolk sac. It is a distinct structure from the yolk sac.
  • Cardiac activity may be detected as a regular flutter in the embryo.
  • Any embryo >5mm should have cardiac activity.
  • Watch the Video

7 week gestation

  • Embryo will be about 12 mm long; the head will be clearly distinguished.
  • Soon after limb buds will start to appear.
  • Watch the Video

Atlas of Abnormal Findings

Intrauterine fetal demise

  • This clip shows a large embryo without cardiac activity.
  • Cardiac activity should be seen in any embryo >5 mm and any gestational sac >16.
  • Notice also the irregular shape of the gestational sac.
  • Watch the Video

Pseudogestational sac

  • This clip shows both an ectopic pregnancy in the adnexa as well as a pseudogestational sac in the uterus.
  • These sacs are found in approximately 20% of ectopic pregnancies.
  • They are located directly in the endometrial cavity, not eccentrically implanted like a normal gestational sac.
  • They do not exhibit the double decidual sign, and do not contain a yolk sac or embryo.
  • Watch the Video

Subchorionic hemorrhage

  • Common cause of vaginal bleeding in the first trimester without miscarriage.
  • Common sonographic abnormality.
  • Crescent shaped fluid collection adjacent to the gestational sac.
  • The size of the hemorrhage is the most important predictor of pregnancy failure.
  • Click to view image
  • Watch the Video

Pelvic free fluid

  • In the sagittal plane, always scan down to the cervix to visualize the posterior cul-de-sac.This is where free fluid will be seen.
  • Small to moderate amounts of fluid may be found in the healthy female pelvis depending on the point in the menstrual cycle.
  • When an ectopic pregnancy is of concern, a significant amount of free fluid raises the concern for rupture.
  • Free fluid is graded in thirds along the posterior wall of uterus: <1/3 mild, up to 2/3 moderate, >2/3 significant
  • Watch the Video 1
  • Watch the Video 2

Anembryonic pregnancy

  • Otherwise known as a “blighted ovum”.
  • May appear as a normally shaped gestational sac, greater than 20mm, without an embryo.Also can present with irregularly shaped borders.
  • When small, the sac cannot be distinguished from the early normal pregnancy.
  • Click to view image
  • Watch the Video

Adnexal mass

  • Limited bedside ultrasound cannot be used to rule out an ectopic pregnancy; it can only be used to rule in an IUP.
  • Although ectopic pregnancies occur everywhere from the cervix to the upper abdomen, 97 percent occur in the fallopian tube.
  • Watch the Video 1
  • Watch the Video 2

Multiple gestation Adnexal mass

What limited ultrasound WILL do:

  • Identify intrauterine implantation
  • Confirm ongoing pregnancy in the setting of vaginal bleeding and pain (“threatened abortion”).
  • Establish gestation age when the menstrual history is inadequate

What limited ultrasound will NOT do:

  • Evaluate pelvic organs outside of the uterus
  • Identify uterine pathology
  • Definitively identify an ectopic gestational sac
  • Evaluate fetal health outside of fetal heart rate determination

 transvaginal ultrasound clinical pathway

 

*Patients with history of fertility treatment not enrolled in this pathway.**IUP defined as minimum of Gestational Sac + Yolk Sac and/or fetal pole (CRL) with cardiac activity.

  • Patient should empty her bladder before the transvaginal scan is performed.
  • Patient should be supine, positioned in lithotomy stirrups if possible; otherwise pelvis should be elevated with blankets while patient’s legs are flexed. This will allow adequate room for transducer manipulation.
  • Transvaginal probe should be correctly attached to ultrasound machine. Marker dot should correlate to left side of monitor screen.
  • Place sterile conducting gel on end of the probe. Cover probe with sheath. Eliminate air bubbles in the conducting gel.
  • Use water based lubricant on the outside of the sheath to lubricate before insertion into the vagina.
  • Watch video

ED Transvaginal Ultrasound Scanning: Sagittal and Transverse Views

Sagitta

Technique: Start watching the screen as soon as the probe is past the introitus; the probe does not have to be inserted all the way to the cervix in order to visualize the uterus. The marker dot is pointed towards ceiling. This produces a longitudinal image of the uterus. The entire endometrial midline stripe should be seen, which is hyperechoic in comparison to the surrounding myometrium. Uterus must be scanned from fundus to cervix by slowly moving the probe in and out. Scan from side to side to visualize entire uterus Watch the Video

Tips: The marker dot is pointed towards ceiling. To visualize the cervix, posterior uterus, and cul de sac, pull probe back a few centimeters and aim probe tip towards the floor. If uterus is not immediately seen, it might be anteverted. Aim probe tip upward toward the abdominal wall to visualize. If the uterus is retroverted, point the probe tip toward the floor. The fundus will be projected to the right side of the screen instead of the left. Sweep probe right to left to complete views of the entire uterus.

Transverse view

Technique: Keeping probe inserted in the vagina, rotate the probe 90 degrees to patient’s right. This will give a transverse image of the uterus. Scan up and down to explore entire uterus. Watch the Video

Tips: The marker dot is pointed towards the patient’s right side. To help with visualization, may use free hand to palpate abdominal wall and bring structures closer to the field of view. This is the best view to visualize the adnexa, located anterior and medial to the internal iliac vessels. Try sweeping the transducer from left to right at the level of the uterine fundus. They are spongy, ovoid in appearance, with scattered anechoic follicles.

Limited Bedside Transvaginal Ultrasound

  • Crown rump length is a simple way to date a pregnancy, and can be used as soon as an identifiable embryo is seen.
  • The yolk sac is not included in the measurement.
  • Technique:
  • Make sure the machine is in “OB” mode in the patient information screen.
  • Scan the uterus in either the sagittal or transverse plane. Freeze an image of the maximal embryo length.
  • Push “calcs” and select CRL.
  • Push “select” and use touch pad to place one caliper at one end of the embryo.
  • Push “select” again to place another caliper at the other end of the embryo.
  • The machine will calculate a date that is accurate to within 5 to 7 days.
  • Watch the Video

Calculate FHR

  • In early pregnancy the naked eye is best at detecting cardiac activity. It is usually seen by 6 weeks, and any embryo >5mm in length should have cardiac activity.
  • To calculate the fetal heart rate, M mode is used.
  • Technique:
    • Make sure the machine is in “Ob” mode on the patient information screen.
    • Push “M mode”. A vertical line will appear on the screen.
    • Use the touch pad to place the line over the flicker of the beating heart.
    • Push “M mode” again.
    • Along the lower screen a series of wavy lines will appear. Freeze a frame of these lines.
    • Push “calcs” and select FHR
    • Push “select” and place one caliper at the peak of one wave.
    • Push “select” again to place another caliper at the peak of the next wave.
    • The machine will calculate the FHR at the bottom of the screen.
    • Watch the Video

Correlation of Gestational Age, b-HCG level, and TVUS findings

Gestational age B-HCG (mIU/ml) TVUS findings
4.5-5 weeks <1,000 Gestational sac
5 weeks 1,000-2,000 Gestational sac + DDS*
5-6 weeks >2,000 Yolk sac** (+/- fetal pole)
6 weeks 10,000-20,000 Embryo with cardiac activity
7 weeks >20,000 Embryonic torso/head

**DDS = double *DDS = double decidual sign
**First definitive evidence of IUP

Tips:

  • B-HCG of 1,500 is considered the discriminatory zone, i.e. minimum quantitative level of HCG at which intrauterine pregnancy should be seen by ultrasound.
  • Abnormal gestation or embryonic demise if:
    • Gestational sac > 10 mm without a yolk sac
    • Gestational sac > 18 mm without a fetal pole
    • Fetal pole > 5 mm without cardiac activity
  • If the B-HCG is > 1500 and no GS is seen
    • Ectopic pregnancy
    • Completed abortion
  • If the B-HCG is < 1500 and the uterus is empty
    • Early normal pregnancy
    • Ectopic pregnancy
    • Completed abortion
  • Serial B-HCG value in 48 hours
    • Live IUP: doubles
    • Completed abortion: decreases
    • Ectopic pregnancy: stable or small rise

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