Emergency Ultrasound Director Virginia M Stewart discusses intravenous access for patients presenting in the Emergency Department.
Patients presenting to the Emergency Department (ED) may have characteristics that impede intravenous (IV) access. Such characteristics may include hypotension, dialysis dependence, morbid obesity, or a history of diabetes, sickle cell disease, or IV drug use. One prospective observational study identified nearly one in every 9 to 10 adults presenting to an urban ED had difficult venous access requiring 3 or more IV attempts.[1] If peripheral IVs are not established, patients may need a central venous catheter placed for life saving medications to be administered. In addition to requiring physician skill, central venous catheter insertion carries a risk of complications including infection, arterial puncture or aneurysm, and pneumothorax. Ultrasound-guidance for peripheral IV placement (UGPIV) has prevented the need for central venous catheter placement in 85% of patients with difficult IV access.[2] UGPIV has been performed by Emergency Medical Technicians (EMTs) in prehospital settings, as well as nurses and physicians. Patients who have been identified as having difficult access, have higher patient satisfaction scores when ultrasound is used in peripheral IV access attempts.[3]
Frequently, the large veins of the antecubital fossa are sufficient to place large bore peripheral IVs needed for resuscitation. The brachial and basilic veins are easy to locate. The brachial artery is typically flanked by 2 smaller veins and the median nerve. Anatomically, these structures are medial to the insertion of the medial biceps tendon. This tendon is palpable in the antecubital fossa as the patient flexes then extends the elbow. The basilic vein is located medial to the brachial vessels. Generally, it is more superficial, larger, and does not have an accompanying artery or nerve at the level of the antecubital fossa. As you move proximally up the arm (towards the head) the basilic vein dives deeper toward the humerus bone, and longer angio-catheters may be required for cannulation.
When considering vascular access, there are 2 views, a short and long axis view. A short axis approach “looks” at a cross section of the vessel. Long axis uses an “in plane” approach with the needle entering from the probe marker end, and “looks” along the length of the vessel. Figure 1 identifies a vessel using color Doppler in the short axis view. Figure 2 demonstrates a long axis view with the needle and tip seen in the vessel. While both short and long approaches may be used for UGPIV placement, the benefit for the short axis is the ability to identify target veins as well as accompanying non-target (arteries and nerve) structures.
Identify the Vein: Remember the C’s
The two C’s to remember for UGPIV access or for central venous cannulation are Compression and Color (or Power) Doppler. Veins are thinner-walled and more easily compressed than arteries. This author advocates for finding a vessel first in the short plane, and compressing the vessel to ensure it is indeed a vein, rather than a less compressible artery. Color or Power Doppler may be utilised to determine if pulsatile flow is consistent with an artery or vein. Color Doppler uses red and blue to determine flow towards or away from the probe respectively. Power Doppler detects flow without concern for direction. Color should not be relied on alone to determine arterial or venous flow due to the color scale setting that can be flipped or reversed, or aliasing can occur. Arterial flow is more pulsatile than venous. Venous flow may require distal augmentation (by squeezing the forearm distal to the probe) to appreciate the blush of color.
Once the target vein is identified, the depth from the skin surface should be noted. A common mistake is to use an angio-catheter that is too long or too short. A general rule of thumb is to use a catheter length that is more than twice the depth of the vessel to ensure at least half the catheter lies within the vein. Sterile ultrasound gel should be used, with a covered probe to prevent infection. To prevent the risk of multiple punctures, it is recommended to first bounce the needle on the skin over the point of entry. The tissue should deform at the top of the screen, and confirm the needle is over the target vessel. Once the skin is punctured, the needle tip is kept in view by angling the ultrasound probe until the target vessel is punctured.
To confirm placement, either a “bubble study” with agitated saline may be performed or Color (or Power) Doppler utilised to visualise saline flow through the cannulated vessel. A vessel that is not properly cannulated will demonstrate extravasation of saline around the vessel into the tissue before the tissue swells to a degree which is palpable on the surface of the skin. Figure 3 demonstrates confirmation of intraosseous (IO) lines utilise Power Doppler. A 10cc saline flush is rapidly pushed through the line, and flow is demonstrated beneath the bony cortex in this adult tibia. If the line is improperly placed, the blush of color using Doppler would appear in the soft tissues.
For further information about UGPIV placement, visit: http://rmgultrasound.com/piv-access/
References:
1) Fields, J.M., Piela, N.E., Au, A.K., Ku, B.S., Risk factors associated with difficult venous access in adult ED patients. Am J Emerg Med. 2014 Oct; 32(10):1179-82.
2) Au, A.K., Rotte, M.J., Grzybowski, R.J., Ku, B.S., Fields, J.M., Decrease in central venous catheter placement due to use of ultrasound guidance for peripheral intravenous catheters. Am J Emerg Med. 2012 Nov;30(9):1950-4.
3) Schoenfield, E., Shokoohi, H., Boniface, K. Ultrasound-guided peripheral intravenous access in the emergency department: patient-centered survey. West J Emerg Med. 2011 Nov;12(4):475-7.
Figure 1:
Short axis view of a peripheral vessel visualized with Color Doppler (blue). The scale on the right of the screen demonstrates a total depth of 2.6 cm. A guide (white dots) in the center of the screen marks each 0.5cm of depth. Therefore the depth of the vessel is between 1-1.5cm deep to the skin surface.
Figure 2:
Long axis view of a peripheral vessel. The hyperechoic needle is visualize approaching from the top left of the screen into the vessel lumen.
Virginia M Stewart MD RDMS RDCS RDMSK
Emergency Ultrasound Director, Emergency Ultrasound Fellowship Director
Department of Emergency Medicine
+1 757 594 2000
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