Ultrasound-Guided Peripheral IV Catheter Placement Technique

The upper limb receives blood supply from the subclavian arteries, which become the axillary artery after passing the first rib and then the brachial artery, branching into radial and ulnar arteries; the venous system parallels this with subclavian, axillary, and brachial veins plus cephalic, basilic, and median cubital veins. The brachial plexus, a netlike nerve structure originating from C5-T1 spinal nerves, is organized into roots, trunks, divisions, and cords, giving rise to major nerves including the radial, ulnar, median, axillary, and musculocutaneous nerves that innervate the upper limb.

Arterial supply: Left ventricle → aorta → aortic arch branches (brachiocephalic, left common carotid, left subclavian) → subclavian → axillary → brachial → radial and ulnar. Venous return: Basilic (medial), cephalic (lateral), median cubital vein connecting them. The median cubital vein is dangerous as injection drug users may accidentally enter the brachial artery. Lymphatic drainage: Approximately 10% of blood returns via lymphatics. Upper extremities and breast drain mainly to axillary lymph nodes. Thoracic duct drains left side; right lymphatic duct drains right side. Carotid sinus contains baroreceptors; carotid body contains chemoreceptors.

This lecture covers the arterial and venous systems of the upper limb using a vascular arm model. The arteries originate from the axillary artery, branch into the anterior and posterior humeral circumflex arteries, continue as the brachial artery, and bifurcate at the antecubital region into the radial and ulnar arteries. The ulnar artery gives off the common interosseous artery, which divides into anterior and posterior interosseous arteries. These arteries form the superficial and deep palmar arches, which give rise to digital arteries supplying the hand. The venous system includes the palmar digital veins forming a palmar venous arch, with the cephalic vein (lateral), basilic vein (medial), and median antebrachial vein connecting via the median antecubital vein. The radial and ulnar veins join to form the brachial vein, which drains into the axillary vein.

The arterial distribution in the upper limb follows a systematic pattern originating from the axilla. The axillary artery enters through the axillary vertex and subdivides to distribute blood throughout the limb. The brachial artery continues from the axillary artery, traversing the anterior compartment of the arm parallel to the humerus. At the elbow level, it divides into the radial artery (lateral) and ulnar artery (medial). These arteries form anastomoses at the hand level, creating the palmar and dorsal arterial arches. Unlike nerves, arteries change names based on regional transitions: subclavian becomes axillary, then brachial. The plexus brachial terminates at the base of the axilla with five terminal branches that continue through the upper limb. Unlike arteries, nerves maintain their names throughout their course regardless of the anatomical region they traverse. The cefalic vein originates at the elbow crease and runs superficially. The forearm has three main superficial venous systems: the cefalic vein (lateral), the basílica vein (medial), and the mediana cubital vein (connecting the two). The basílica vein becomes deep at the mid-arm level, crossing the fascia to join the deep brachial vein. Superficial nerves accompany these veins in the same subcutaneous plane. The axilla contains several important spaces: the lateral axillary space contains the axillary nerve and posterior circumflex humeral artery; the medial axillary space contains the subscapular artery and vein; and the inferior axillary space contains the radial nerve and brachial profunda artery.

The upper limb venous system consists of superficial and deep veins. Superficial veins lack direct arterial relationships and are visible on the surface, while deep veins accompany arteries (except the axillary artery, which has only one venous trunk). Superficial veins originate from the dorsal venous network of the fingers, forming lateral digital veins that create the dorsal digital arch. This arch produces metacarpal veins: the thumb's form the cephalic vein, the index finger's form the basilic vein, and the middle finger's form the median vein. At the elbow, the median vein bifurcates into median cephalic and median basilic veins. The cephalic vein of the arm forms from the union of the forearm's cephalic vein with the median cephalic vein, while the basilic vein forms from the union of the forearm's basilic vein with the median basilic vein. The basilic vein runs along the medial border of the biceps brachii, while the cephalic vein runs along the lateral border. In the middle third of the arm, the cephalic vein perforates through the biceps fascia and runs toward the axilla, forming the cephalic arch before emptying into the axillary vein.

Ultrasound is a mechanical longitudinal wave with frequencies above 20,000 Hz that propagates through tissue, where frequency determines penetration depth (low frequency penetrates deeper but with less resolution, while high frequency provides better resolution but shallower imaging), and image quality depends on proper probe selection (curved/array for deep structures, linear for superficial structures), depth adjustment, gain control, and understanding transducer orientation where the probe marker indicates the patient's head/right side and the near field appears at the top of the screen.

The 90/10 rule states that sonographers use only 10% of machine buttons 90% of the time. Essential knobs/buttons include: Preset button (chooses exam-specific optimized settings for power, gain, frequency, and focus); Transducer select (chooses appropriate transducer for exam type); Gain (controls image brightness by making whole image darker or brighter); Depth (controls imaging depth, set about 1-2 cm beyond area of interest); Focus (moves focus zone up/down, placed just at or below area of interest for maximum detail); TGC sliders (fine-tune brightness at specific depths); Freeze button (stops live imaging on last frame); Store button (saves still image); Caliper button (measures distance, circumference, or area); Annotation tools (label images with orientation, laterality, and organ names).

This video teaches the fundamental physics principles and machine controls essential for clinical ultrasound imaging, including how ultrasound waves interact with tissues based on density (echogenicity), the trade-off between transducer frequency and penetration depth, proper orientation using standard indicators, and how to optimize image quality by adjusting depth, gain, and frequency settings while understanding common artifacts like acoustic shadowing, enhancement, and reverberation.

This video teaches the fundamental controls and physics principles of ultrasound machines, covering transducer selection (where probe frequency determines penetration depth and resolution), exam preset optimization for different applications (muscle/skeletal, cardiac, abdominal, lung), depth adjustment for focusing on specific structures, gain control for image brightness, focus positioning for resolution enhancement, color flow Doppler interpretation (red = blood toward probe, blue = blood away), M-mode for motion analysis, and image freezing/acquiring for documentation.

This video explains that physicians can achieve competency in bedside ultrasound with minimal training (as shown by studies demonstrating 95-98% accuracy after 8.5 hours of instruction), covering essential physics principles including B-mode for grayscale imaging, M-mode for motion analysis, color Doppler for flow direction (blue=away, red=toward), and power Doppler for low-velocity flow detection; key probe selection involves balancing frequency trade-offs between resolution and penetration (higher frequencies provide better detail but less depth), with different probes suited for specific applications (P21 for heart/abdomen, linear probes for superficial structures); image optimization requires proper gain adjustment, depth control, and understanding common artifacts such as acoustic shadows from high-attenuating tissues, posterior enhancement from fluid, air-induced dirty shadows, refraction artifacts, reverberation, and mirror images from reflective surfaces like the diaphragm.

Arteries and veins can be distinguished using Doppler ultrasound through multiple criteria: on grayscale, arteries pulsate with thick, non-compressible walls while veins are non-pulsatile with thin, easily compressible walls; on color Doppler, arteries typically show positive (toward transducer) flow above the baseline while veins show negative (away from transducer) flow below the baseline, though exceptions exist like the portal vein; and on spectral Doppler, arteries display pulsatile waveforms with triphasic, biphasic, or monophasic patterns depending on resistance level, whereas normal veins show spontaneous, non-pulsatile, phasic flow with augmentation and compressibility, with five key features including spontaneous flow, non-pulsatility, phasicity, augmentability, and compressibility.

Nerves appear tubular with a 'honeycomb' appearance in transverse view, with hyperechoic perineurium and hypoechoic fascicles. Ligaments connect two bone surfaces and appear similar to tendons. Articular cartilage appears hypoechoic adjacent to hyperechoic bone. Blood vessels appear hypoechoic (black) because they are fluid-filled. To differentiate arteries from veins, compression testing can be used: veins collapse with pressure while arteries remain patent. Doppler ultrasound detects blood flow direction and velocity based on frequency shift. Power Doppler removes directional information and only shows presence of flow, useful for detecting vascularization in pathological tissues like tendons or inflammatory conditions.

Ultrasound differentiates tissues based on echogenicity: subcutaneous tissue appears gray, blood and water appear black, vascular walls appear whitish, fascial sheaths appear whitish, and nerves appear gray-white with a honeycomb pattern. Dense structures appear whiter. Critical differentiation: veins are round, black, and compressible; arteries are round, black, and pulsatile; nerves do not compress and pulsate. Non-compressible vessels should never be cannulated as they are likely nerves.

Veins can be distinguished from arteries by their compressibility - veins easily collapse when pressure is applied, while arteries maintain their shape. When identifying a vessel, briefly compressing it reveals whether it is a vein (collapses) or an artery (remains round). This distinction is critical because accidentally puncturing an artery can cause significant complications.

Two ultrasound modes are essential: B-mode for structural identification (anechoic/black for non-reflecting structures, hyperechoic/white for reflecting structures) and Doppler for flow characterization. Red indicates flow toward the transducer, blue indicates flow away. High-frequency transducers (5-15 MHz) provide superior resolution for superficial structures. Vessel differentiation relies on: compressibility (veins collapse, arteries maintain shape), pulsatility (arteries show pulsatile flow on Doppler), wall thickness (arteries have thicker walls), and posterior acoustic enhancement. Arteries are non-round and non-compressible, while veins are round and compressible.