Changes

==Introduction==

==Introduction==

Blood pressure is an useful measurement to help assess cardiovascular status of a patient during an anaesthetic. As many agents used for anaesthesia have an affect on the cardiovascular system, and blood pressure in particular it is important to detect this early so that it can be corrected if necessary. It is also essential for some surgical procedures as the surgery itself may have a direct effect on the blood pressure of that animal and so requires to be closely monitored, for example portosystemic shunt surgery. There are various methods of measuring blood pressure both invasive and non invasive.  

Blood pressure (BP) is a useful measurement to help assess the cardiovascular status of a patient during an anaesthetic, or as a diagnostic test for an underlying cause of ocular changes in cats as a result of systemic high blood pressure. Bear in mind that in a conscious animal, a stress free environment is useful in preventing a rise in blood pressure which is induced by anxiety, particularly in cats. Many agents used during anaesthesia have an affect on the cardiovascular system, and blood pressure in particular so it is important to monitor sequential readings and correct BP changes if necessary. Some surgical procedures such as portosystemic shunt surgery, for example may have a direct effect on blood pressure and BP must be closely monitored throughout the procedure.

==Normal Arterial Blood Pressures==

==Normal Arterial Blood Pressures==

==Non Invasive Methods==

==Non Invasive Methods==

===Doppler Flow Detection===

===Doppler Flow Detection===

*Usually measured using the metacarpal and metatarsal artery, although the tail can also be used.

#Usually measured using the metacarpal and metatarsal artery, although the base of the tail can also be used.

#Once a pulse has been detected, the doppler probe is placed over to check that it is audible and the probe is taped to the limb.

#Once a pulse has been detected, the doppler probe is placed in that position on the limb to check that it is audible and the probe can then be taped to the limb.

#A cuff is selected and placed proximal to the doppler probe and attached to a manometer.

#A cuff is selected and placed proximal to the doppler probe and attached to a manometer.

#The cuff is inflated until the pulse is no longer audible on the doppler.

#The cuff is inflated until the pulse is no longer audible on the doppler.

#The cuff is the gently released and a reading is taken when the pulse becomes audible again.

#The cuff is gently released and a reading is taken when the pulse becomes audible again.

*The measurement is systolic pressure.

*This measures systolic pressure only.

*Cuff width should measure as 40% of the circumference of the limb being used.

*Cuff width should ideally be 40% of the circumference of the limb chosen for this method to be accurate. The cuff should be applied so that only a small finger can be inserted between the cuff and the leg, to ensure that it is neither too tight nor too loose.

*'''Advantages'''

'''Advantages'''

**Cheap and available in most practices.

*Cheap and available in most practices.

**Useful in hypotensive patients.

*Useful in hypotensive patients.

*'''Disadvantages'''

'''Disadvantages'''

**Not very reliable in horses.

*Not a reliable method in horses.

===Oscillometric Method===

===Oscillometric Method===

*Method

Method:

#The cuff is placed on a distal limb or tail.  

#The specialised oscillometric cuff is placed on a distal limb or tail.  

#The cuff automatically inflates.

#The cuff automatically inflates.

#As it deflates, oscillation in the cuff is detected.

#As it deflates, oscillation in the cuff is detected electronically.

*Measures systolic, diastolic and mean arterial blood pressure as well as pulse rate.  

*Measures systolic, diastolic and mean arterial blood pressure as well as pulse rate. The first oscillation of blood flow detected is the systolic pressure, the largest oscillation is equal to the mean pressure, and the oscillations subside at diastolic pressure.

*'''Advantages'''

'''Advantages'''

**Good in dogs.

*Good in dogs.

**Automatic.

*Automatic.

*'''Disadvantages'''

'''Disadvantages'''

**Less reliable in cats and hypotensive patients.

*Less reliable in cats and hypotensive patients.

**Expensive.

*Expensive.

==Invasive Methods==

==Invasive Methods==

===Arterial Catheterisation===

===Arterial Catheterisation===

*Catheter is placed in a peripheral artery and attached to either a anaeroid manometer or electronic transducer.

*An anaeroid manometer only gives a mean arterial blood pressure reading.

#A catheter is placed in a peripheral artery and attached to either an anaeroid manometer or electronic transducer.

*An electronic transducer gives systolic, mean and diastolic arterial blood pressure readings.

#An anaeroid manometer gives a mean arterial blood pressure reading; an electronic transducer gives systolic, mean and diastolic arterial blood pressure readings.

*In dogs, the dorsal pedal artery is commonly used.

#In dogs, the dorsal pedal artery is commonly used.

*In horses, the facial, transverse facial or metatarsal arteries used.

#In horses, the facial, transverse facial or metatarsal arteries are usually used.

*'''Advantages'''

'''Advantages'''

**Continuous measurement.

*Continuous measurement.

**Catheterisation allows for blood gas analysis sampling.

*Catheterisation allows for additional sampling for blood gas analysis.

*'''Disadvantages'''

'''Disadvantages'''

**Invasive

*Invasive

**Requires the correct equipment, which can be expensive.

*Requires the correct equipment, which can be expensive.

==Central Venous Pressure==

==Central Venous Pressure==

Central venous pressure (CVP) is an indicator of blood return to the heart. It indicates adequacy of fluid therapy, heart performance and volume loading of the heart. It is measured by the placement of a central line, usually via the jugular vein. The same method is then used for invasive arterial blood pressure measurement.

Central venous pressure (CVP) is an indicator of blood return to the heart. It indicates adequacy of fluid therapy, heart performance and volume loading of the heart. It is measured by the placement of a central line, usually via the jugular vein. The method then used is that described above for invasive arterial blood pressure measurements.

*Low or falling CVP suggests hypovolemia.

*Low or falling CVP suggests hypovolemia.

*High or rising CVP suggests volume overload or a failing heart.

*High or rising CVP suggests volume overload or a failing heart.

[[Category:Blood Pressure|A]]

[[Category:Blood Pressure|A]]