assessment of blood pressure Flashcards
(24 cards)
what are the normal BP values in dogs and cats
listed as the same in both
Systolic: 90 - 140mmHg
Mean: 70 - 100mmHg
Diastolic: 50 - 80mmHg
How is MAP calculated
MAP = Diastolic + ((systolic - diasolic)/3)
how is doppler BP measured
- cuff applied then a doppler transduced placed distally over peripheral artery (coupling gel)
- cuff inflated until no blood flow then slowly inflated until audible signal = systolic BP
Advantages of doppler
Non invasive
- more accurate than other non invasive in dysrrhymias and small patients
how is oscillometric BP measured?
- Cuff attached to machine which detects oscillations from arterial flow
- these are greatest at the mean
- the systolic and diastolic are then calculated from the mean.
what are the advantages and limitations of oscillometric
- non invasive
- less prone to human error than doppler from speed of cuff deflation.
- less accurate in very small patients or those with dysrhymias, check that the machine is counting the HR correctly.
How can you help to reduce the limitations of indirect BP measurement
- standardise process
- appropriate cuff number 30-40% of limb circumference
- select largery if between two
- limit vertical distance from heart to cuff (sternal or lateral recumbancy)
- want the level of the right atrium - below overestimates and above underestimates
- can correct by 0.8mmhg/cm if more than 10com below/above
- discrad 1st reading and average from 5 -7
What are the general limitations of indirect BP measurement
rely of peripheral flow so effected by hypovolaemia, hypothermia, vasoconstriction, vasopressors and hear failure
- tend to overestimate
how is direct arterial BP measured
arterial catheter in the dorsal pedal artery is attached to a monitor via a fluid line and a pressure transducer
- gives MAP, systolic, diastolic and generates a waveform.
- most accurate
What are some problems associated with arterial BP monitoring
- need regularly line flushing as prone to occlusion by clots and bubbles (dampens waveform)
- complications; medication given in error, accidendental removal + bleeding, thrombosis of the limb and technical ability to place.
- can be hard to place in small patients or if have very poor perfusion
hypertension is a BP>150/95 (115). What are the risk categories for organ damage
i. <150mmHg, minimal
ii. 150 - 159mmHg mild
iii. 160 - 179mmHg moderate
iv. >180mmHg severe
What ocular changes may be seen with systemic hypertension
acute onset blindness, intraocular haemorrhage, retinal detachment
- on exam you may note torturous retinal vessels oedema or degeneration
What neurological changes can be seen with systemic hypertension?
altered mentation, disorientation, seizures, imbalance, head tilt and nystagmus.
should respond to BP reduction
- make sure TBI and cushing response ruled out
What renal changes can be seen with systemic hypertension?
- usually more insidious onset
- azoatemia, increased SDMA, proteinuria.
- note hypertension can be both cause and effect of Renal issues
Hypertension is inappropriately high SVR either along or with changes in blood volume
discuss the pathophysiology
- sympathetic stimulation increases catecholamies, angiotensin2, endothelian 1 and vasopressin. local vasodilators (NO and prostacyclin) are reduced.
volume expansion due to inadequate renal excretion or sodium and water retension. - inflammation with oxadative stress leads to endothelial dysfuntion and reducing NO bioavailibility
- causes vascular remodelling resulting in cytokine production, endothelial adhesion and WBC upreg
-leads to target organ damage or SIRS
what may cause hypertension
- situational
- primary (rare) diagnosis of exculsion, usually proteinuria with low USG, other tests normal.
- secondary (common), lost of disesaes eg renal, endocrine, hepatic, anaemia, polycytheamia, neoplasic.
- each disease has variable mechanism but most cause inappropriate hormone secretion:
RASS activation, adrenal cortex tumours acuse aldoserone production and adrenal medulla catecholamines.
What are the treatment goals for hyperstension
- want to reduce to 160mmHG as a minimum
- aim for 10% reduction first hour the further 15% subsequent hrs.
- if concurrent kidney disesae looking for UOP drop by 50%.
What/how are arterial vasodilators used to treat hypertension
- SNP or Hydralazine
- Both increase NO concentrations leading to arterial dilation.
- given as a CRI
- ideally art line BP monitoring
What/how are ACE inhibitors used to treat systemic hypertension
- Enalapril and benazepril
- Reduces production of angiotension 2 leading to reduced vasoconstriction and sodium and water retension at the kidney
- used for more chronic hypertension associated with cardiac and renal disease. unlikely to lower BP enough in emergencies.
What/how are calcium channel blockers used to treat hypertension
- Amlodipine
- reduce smooth muscle constriction by inhibiting calcium channels in vasculature
- rapid onset oral amodip should help in an hour and the dose can be repeated.
when are alpha adrenergic ANTAGONISTS useful
- Prazosin and ACP
- cause smooth muscle relaxation via effects on the alpha receptors
- most useful in hypertension resulting from pheochromocytomas and aldosterone secreting tumours.
Beta adrenergic antagonists - examples of and when could they treat hypertension
-atenolol and propanolol
- cause a reduction in renin secretion and therefore the effects of the RAAS ( vasoconstriction via angiotensisn 2, water rentention from ADH and NA and water retenstion from aldosterone.
- most useful in pheochromocytomat and aldo sterone secreting tumours
What ARB are used in hypertension
- angiotensin 2 receptor blockers
- eg telimasartan
