VISCOUS FACTS❗️

⌛️Dynamic or absolute viscosity is a measure of the resistance of a fluid or gas to flow. It is measured using a viscometer or rheometer.

⌛️The SI unit of dynamic (or absolute) viscosity is the pascal-second (Pa·s), equivalent to N·s/ m2.

⌛️Viscosity is independent of flow rate

⌛️Viscosity is independent of pressure

⌛️️For a gas, viscosity decreases as its temperature increases 

⌛The relationship between viscosity and temperature and pressure only holds true for those fluids and gases that exhibit ‘Newtonian’ properties, i.e. substances that will always flow irrespective of forces acting upon them (e.g. crystalloid solutions and water). 

⌛️ Blood is a non-Newtonian fluid and its viscosity depends largely on haematocrit (and varies with flow rate).

⌛️Blood viscosity is increased by volatile anaesthetic agents, smoking and aging❗️

⌛️A thixotropic substance is one that becomes less viscous over time when agitated. If it becomes more viscous with agitation, this is known as a rheopectic material.

⌛️Kinematic velocity is defined as the dynamic velocity of a substance divided by its density.

ERRORS THAT CAN HAPPEN WITH THE SAMPLING FOR ARTERIAL BLOOD GAS ANALYSIS AND POSSIBLE CONSEQUENCES

❎AIR BUBBLES IN SYRINGE: may wrongly increase the Pao2 , Sao2 and pH

❎DILUTION OF THE SAMPLE WITH SALINE FLUSH OR HEPARIN: may wrongly increase Pao2 , while it decrease Paco2 , glucose, lactate , potassium and hemoglobin 

❎VENEPUNCURE DURING SAMLE COLLECTION: may wrongly decrease Po2 and So2 while it increases Pco2

❎ CLOTTING OF THE SAMPLE: may wrongly increase the potassium concentration 

#ABGerrors , #abg , #AbgSampling

ERRORS IN ABG SAMPLING: CAUSES & CONSEQUENCES

🔹Reduced pH (anaerobic metabolism)

🔹Reduced PaO2 (utilization of dissolved oxygen)

🔹Raised PaCO2 ( production of CO2 from continued metabolism)

🔹Reduced glucose ( utilization if glucose stores)

🔹Increased lactate( anaerobic metabolism)

#abg , #AbgErrors

CALCULATION OF THE VOLUME OF OXYGEN CYLINDER REQUIRED FOR A TRANSFER

▫️For this, we should know:

     1. Oxygen delivered = FiO2 x Minute Volume 

     2. Duration of the transfer

▫️For e.g. If we are expecting a duration of 2 hours (120 minutes) and we are having Size E cylinders and also need to deliver an FiO2 of 1 @ 6L / min

1. O2 delivered = 1 x 6 = 6L/ min

2. Size E has 660 L of O2, which will suffice for 660/6= 110 minutes ; so for 120 minutes, we need 2 cylinders 

#AnesthesiaGas , #OxygenCylinder

DIPPING IN DOPPLER

🎯The Doppler effect can be explained by considering a series of water-waves travelling out from the centre of a pond, in a circular form

🎯The frequency of the waves is related to the medium and the speed at which they are travelling. 

🎯The frequency of the waves reaching the periphery is less than the frequency nearer the centre. 

🎯If a detector was in the periphery it would detect the frequency of the waves whose frequency will be less

🎯But if the detector then started moving towards the source, the frequency would increase as the detector would be picking the waves nearer to the centre, whose frequency will be more.

🎯The Doppler effect describes the change in frequency of sound waves if the source of sound is moving in relation to the detector. The frequency is increased if the source is moving towards the detector and reduced if it is moving away.

🎯APPLICATIONS OF DOPPLER EFFECT

✔️It allows the confirmation of flow within peripheral arteries as well as in the brain, where the circle of Willis can be scanned.

✔️In echocardiography

✔️in obstetric practice when a fetal heart rate monitor is used

#doppler ,#anesthesia , #usg