iv therapy 2008
DESCRIPTION
iv cannulation useful tipsTRANSCRIPT
IV TherapyAnatomy & Physiology
Dr Manjit George Anaesthetics
Anatomy
Upper limb veins
• Basilic vein• Cephalic vein • Median cubital vein
Lower limb veins• Femoral vein• Saphenous vein
Anatomy
ARTERY ARTERIOLES CAPILLARY THE HEART VEIN VENULE
Structure of vessels
• Arteries- smooth muscles
Clinical application- cold, nerve blocks
• Arterioles- tiny branches of arteries that lead to capillaries
Controlled by Sympathetic Nervous System
constrict & dilate to regulate blood flow
Structure of vessels
• Veins- Walls consist of 3 layers of tissues thinner and less elastic than the corresponding layers of arteries
• Valves aid return of blood to the heart by preventing blood flowing in the reverse direction
Structure of vessels
• Capillaries- tiny blood vessels(approx 5-20 microns in diameter)
Walls are only one cell thick
permits exchanges of material between them & the surrounding tissue
• Venules- minute vessels that drain blood from capillaries into veins
Many venules unite to form a vein
Artery v/s Vein
• Away from heart
• Oxgenated blood
• Narrow lumen
• More muscle/elastic
tissue
• High pressure
• Towards the heart
• Deoxygenated blood
• Wide lumen
• Less muscle /elastic
tissue
• Low pressure
Physiology
• Superficial veins are not paired with an artery unlike deep veins
• Superficial veins are important physiologically for cooling of the body
• Not as important as deep veins as they carry less blood
Physiology
Poiseuille’s Law
Flow rate F = P1 – P2 __ _____ = R
(pressure difference) (radius)4
_______________________8(viscosity) (length)
Determinants of flow rate
• Viscosity of infusing fluid• Length of the plastic cannula tube• The diameter of the tube (gauge size)• size 24 - 19mm long, 0.7 diam,flow rate -22ml/min
size 14 - 50mm long, 2.2 diam, flow rate 343ml/min• Pressure of infusion (pressure bags)• Blood pressure of the patient
Clinical patho physiology
• Varicose veins
• Venous ulcers
• Arterialisation of veins – AV fistula
A “good” vein
• One that is not kinked
• One that is clearly visible
• One that is easily palpable
• “Forked” veins where 2 tributaries come together
Unsuitable veins
• Tortuous veins• Flexor aspect of the wrist (risk of radial.n damage)• Veins above the elbow joint- median cubital vein• Veins over bony prominences• Dorsum of hand in the elderly except when they are
prominent & well filled• Avoid patients dominant arm, if possible• Areas over mobile joints/ areas of flexion• Limbs with fractures/ a-v shunts
Difficult venous access
• Obese
• Extremes of age
• Grossly oedematous states- hypoalbuminemia
• Burns
• IV Drug Abusers
• Malignancy- Oncology patients
• Sickle cell anaemia
Practical issues
• Indication ?• Site ?• Rate of infusion ?• Choice of cannula size ?• Duration ?• Protocols ?
Venflons- infusion rates
• 14 G- 343ml/min• 16 G- 220 ml/ min• 18 G- 120 ml/min• 20 G- 80ml/min• 22 G- 40 ml/min• 24 G- 22ml/min
Complications
• Pain/ fear
• Bruising/ Haematoma
• Thrombophlebitis
• Injury to nerve/artery
• Subcutaneous infiltration
• Cellulitis
Practical tips
• Visual / tactile senses, good lighting • Start distally• Dependant position (below heart level)• Tourniquet/ BP cuff inflated to 70-80 mm Hg• Tapping/ opening and closing of fist• Local application of warmth/ warm towel• Correct size of venflon• Hair/ sweat• EMLA cream(1 hour), Ametop (20 mins), Lignocaine 1%