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Questions and Answers
What is the primary function of the renin-angiotensin mechanism?
What is the primary function of the renin-angiotensin mechanism?
What defines systemic arterial hypertension?
What defines systemic arterial hypertension?
Which measurement technique is considered the gold standard for measuring blood pressure?
Which measurement technique is considered the gold standard for measuring blood pressure?
Which condition is NOT classified as a secondary cause of hypertension?
Which condition is NOT classified as a secondary cause of hypertension?
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What process serves as an intermediate-term pressure buffer in blood vessels?
What process serves as an intermediate-term pressure buffer in blood vessels?
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What is the result of a mean arterial pressure (MAP) less than 80 mmHg?
What is the result of a mean arterial pressure (MAP) less than 80 mmHg?
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Which of the following is a common trigger for situational hypertension?
Which of the following is a common trigger for situational hypertension?
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Which hormone plays a key role in the long-term regulation of arterial pressure by controlling blood volume?
Which hormone plays a key role in the long-term regulation of arterial pressure by controlling blood volume?
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What is one possible consequence of hypertension affecting the kidneys?
What is one possible consequence of hypertension affecting the kidneys?
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During the neurological examination, which sign would be indicative of potential hypertensive encephalopathy?
During the neurological examination, which sign would be indicative of potential hypertensive encephalopathy?
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What immediate action should be prioritized if there is obvious evidence of target organ damage (TOD)?
What immediate action should be prioritized if there is obvious evidence of target organ damage (TOD)?
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Which diagnostic test is crucial for evaluating potential retinal issues in hypertensive patients?
Which diagnostic test is crucial for evaluating potential retinal issues in hypertensive patients?
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In a case where blood pressure is measured at 220 mmHg, what is a suitable first step?
In a case where blood pressure is measured at 220 mmHg, what is a suitable first step?
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Which of these might be a differential diagnosis when faced with left central vestibular disease in a cat?
Which of these might be a differential diagnosis when faced with left central vestibular disease in a cat?
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What is a potential cardiovascular consequence of chronic hypertension?
What is a potential cardiovascular consequence of chronic hypertension?
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Upon observation of neurological deficits, which condition should be ruled out as part of the diagnostics?
Upon observation of neurological deficits, which condition should be ruled out as part of the diagnostics?
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What is the normal mean arterial pressure (MAP) in mmHg?
What is the normal mean arterial pressure (MAP) in mmHg?
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Which hormone primarily mediates renal retention of salt and water?
Which hormone primarily mediates renal retention of salt and water?
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What effect does norepinephrine have on blood vessels?
What effect does norepinephrine have on blood vessels?
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Which mechanism does the sympathetic nervous system use to control blood pressure rapidly?
Which mechanism does the sympathetic nervous system use to control blood pressure rapidly?
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What is the typical response of the kidneys when blood volume decreases?
What is the typical response of the kidneys when blood volume decreases?
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Which of the following factors does NOT contribute to the systemic regulation of blood pressure?
Which of the following factors does NOT contribute to the systemic regulation of blood pressure?
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What effect does stimulation of the vagus nerve have on heart rate?
What effect does stimulation of the vagus nerve have on heart rate?
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Which condition is most likely to cause hypertension in veterinary patients?
Which condition is most likely to cause hypertension in veterinary patients?
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What defines a hypertensive emergency?
What defines a hypertensive emergency?
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What is the initial goal for reducing systolic blood pressure in a hypertensive emergency?
What is the initial goal for reducing systolic blood pressure in a hypertensive emergency?
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Which medication is considered a potent arterial vasodilator but is less dangerous regarding hypotension?
Which medication is considered a potent arterial vasodilator but is less dangerous regarding hypotension?
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Which condition is most likely to lead to hypotension due to reduced preload?
Which condition is most likely to lead to hypotension due to reduced preload?
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What mechanism initiates shock as a consequence of hypotension?
What mechanism initiates shock as a consequence of hypotension?
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What type of medication increases cardiac contractility?
What type of medication increases cardiac contractility?
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What is the main cause of inappropriate vasodilation leading to maldistributive shock?
What is the main cause of inappropriate vasodilation leading to maldistributive shock?
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Which medication is the drug of choice in cases of anaphylaxis?
Which medication is the drug of choice in cases of anaphylaxis?
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In the case of hypotensive states, what reaction primarily increases systemic vascular resistance?
In the case of hypotensive states, what reaction primarily increases systemic vascular resistance?
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Which patient condition is most sensitive to hypoperfusion-related injury?
Which patient condition is most sensitive to hypoperfusion-related injury?
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What is the recommended initial treatment for hypovolemia?
What is the recommended initial treatment for hypovolemia?
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Which of the following is a common cause of severe hypotension due to cardiac function reduction?
Which of the following is a common cause of severe hypotension due to cardiac function reduction?
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What role does vasopressin play in the treatment of hypotension?
What role does vasopressin play in the treatment of hypotension?
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What defines preload in the context of cardiac physiology?
What defines preload in the context of cardiac physiology?
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Study Notes
Hypotension/Hypertension
-
Objectives:
- Explain physiological mechanisms of blood pressure regulation
- Identify common causes of hypotension and hypertension in veterinary patients
- Recognize clinical consequences of abnormal blood pressure
- Develop a basic treatment approach for managing hypotension and hypertension
Definitions - Arterial Blood Pressure
- Normal systolic pressure: 120 mmHg
- Normal diastolic pressure: 80 mmHg
- Normal mean arterial pressure (MAP): 90 mmHg
- MAP = DBP + 1/3 (SBP - DBP)
Determinants of Blood Pressure
- MAP = CO × SVR (CO = Cardiac Output, SVR = Systemic Vascular Resistance)
- Local factors (e.g., prostaglandins, histamine, nitric oxide)
- Systemic factors (e.g., vasopressin, angiotensin II, sympathetic tone)
- Heart rate (HR): Sympathetic vs parasympathetic tone
- Stroke volume (SV): Preload, afterload, contractility
- Kidneys: Regulate fluid in the system
Nervous Regulation of Circulation
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Sympathetic nervous system:
- Basal tone can increase or decrease
- Norepinephrine is the main neurotransmitter
- Binds to α1 receptors on vessels → vasoconstriction
- Binds to β1 receptors on heart → tachycardia, inotropy (increased contractility)
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Parasympathetic:
- Minimal effect on blood pressure
- Stimulation of vagus nerve → bradycardia
Kidneys and RAAS
- Pressure diuresis: Increased blood volume → kidneys excrete more water. / Decreased blood volume → kidneys excrete less water (ADH/vasopressin mediated)
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Renin-Angiotensin-Aldosterone System (RAAS): Activated when blood flow to the kidneys decreases
- Renin release
- Angiotensin II production
- Renal retention of salt and water
- Vasoconstriction
- Stimulation of aldosterone production → increased sodium reabsorption
Control of Blood Pressure
-
Short-term mechanisms (seconds to minutes):
- Baroreceptor feedback mechanism
- Central nervous system ischemic mechanism
- Chemoreceptor mechanism
-
Intermediate-term mechanisms (minutes to hours):
- Renin-angiotensin vasoconstrictor mechanism
- Stress relaxation of the vasculature
- Fluid shift through tissue capillary walls
-
Long-term mechanisms (hours to days):
- Kidney control of blood volume
- Aldosterone
- Renin-angiotensin system
Systemic Arterial Hypertension
- Sustained, pathological increase in systemic arterial blood pressure
- Systolic BP > 160 mmHg
- MAP > 130 mmHg
Hypotension
- Decreased arterial blood pressure
- Systolic BP < 90 mmHg
- MAP < 80 mmHg → impaired tissue perfusion
Hypertension - Diagnosis
- Systolic BP > 160 mmHg
- Repeated measurements needed for confirmation
- Exception: evidence of target organ damage (TOD)
- Table 6: Classification based on risk of target-organ damage
Causes of Hypertension
-
Situational:
- Artificial elevation due to stress of being in a hospital setting.
-
Secondary:
- Underlying disease process
- Chronic kidney disease
- Acute kidney disease
- Diabetes mellitus
- Hyperadrenocorticism (dogs)
- Hyperthyroidism (cats)
- Pheochromocytoma (dogs)
- Hyperaldosteronism (cats)
-
Idiopathic:
- No identifiable underlying cause
Consequences of Hypertension - Target Organ Damage (TOD)
- Can affect the kidney, eye, brain, heart and blood vessels
- Kidney: progression of CKD, increase in creatinine, SDMA BUN, proteinuria
- Eye: acute blindness, retinal detachment, retinal hemorrhage
- Brain: encephalopathy, stroke
- Heart and blood vessels: left ventricular hypertrophy
Case Studies
- Dolly (12 yo FS DSH): Vomiting, anorexia, tachycardia, weak pulses, 60 mmHg blood pressure (Doppler). Initial stabilisation was performed to treat the hypotension. An ultrasound revealed a foreign body in the jejunum that had perforated through the intestinal wall, necessitating surgical treatment..
Types of Hypertension
- Hypertensive emergency: Marked hypertension (SBP > 180 mmHg) with ongoing acute TOD. Requires rapid treatment.
IV Antihypertensives
- More potent, often more dangerous
- Easier to titrate to effect
- 24 hour facility required.
- Examples: fenoldopam, nitroglycerin, hydralazine
Oral Antihypertensives
- Less potent, less dangerous
- Preferred for long-term management especially in Chronic Kidney Disease (CKD)
- Examples: calcium channel blockers (amlodipine), ACE inhibitors, angiotensin receptor blockers
Causes of Hypotension
- Local factors: CO2, prostaglandins, NO, histamine
- Systemic factors: Vasopressin, Angiotensin II, sympathetic nervous system (SNS) vs parasympathetic nervous system (PNS) Reduction in preload, reduction in cardiac function, reduction in systemic vascular resistance
Consequences of Hypotension
- Decreased perfusion → decreased oxygen delivery→shock
- Sympathetic tone↑→ tachycardia, inotropy↑→vasoconstriction
- Renin-Angiotensin system stimulated→vasoconstriction
- Aldosterone: decreased Na excretion and increased water reabsorption in kidneys.
- Kidneys → acute kidney injury
- Brain → altered mentation
- Heart → arrhythmias
Reduction in Preload
- Reduced venous return → reduced preload →reduced CO → hypotension
- Hemorrhage, Gl/kidney fluid loss, dehydration, cavitary effusions, GDV, pericardial effusions.
Treatment of Decreased Preload
- Hypovolemia: IV fluids (10-20 ml/kg balanced isotonic fluids). Hemorrhage may require transfusions.
- Obstruction of blood flow: IV fluids to increase preload
- Remove the obstruction (GDV, pericardial effusion)
Reduction in Cardiac Function
- Primary heart disease: Dilated cardiomyopathy
- Secondary: Severe acidosis/alkalosis, toxin/drug exposure, systemic inflammatory response syndrome (SIRS)/sepsis.
Treatment for cardiac dysfunction reduction
Positively inotropic agents such as dobutamine can improve heart contractility and increase cardiac output
Reduction in Systemic Vascular Resistance
- Maldistribution of blood flow due to vasodilation
- Sepsis (excessive NO production)
- Anaphylaxis
Treatments for Reduction in SVR
- Norepinephrine (α receptor agonist → vasoconstriction), dopamine (β and α agonist), and epinephrine (potent β,α receptor agonist) and vasopressin (V1 receptor agonist). These are usually given as IV medications
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Description
This quiz covers the physiological mechanisms of blood pressure regulation in veterinary patients, focusing on both hypotension and hypertension. You will explore common causes, clinical consequences, and treatment approaches for managing abnormal blood pressure. Test your understanding of key definitions and determinants of arterial blood pressure.
