Lecture 23 Flashcards
What are the determinants of blood pressure?
Cardiac output (determined by stroke volume, heart rate and heart contractility) and Peripheral vascular resistance determined at the level of the arterioles by neural and humoral factors
What is the definition of hypertension?
Abnormally high blood pressure in a vascular bed
Why does blood pressure need to be measured several times over the course of several weeks to gain an adequate diagnosis of hypertension?
As blood pressure varies greatly with things such as posture, exercise and stress more than one reading is required to gain a true value of what the patients blood pressure is
What pressures are officially considered to be hypertension?
Diastolic pressures of >90mmHg
Systolic pressures of >140 mmHg
(Using these criteria 800 million people world round are affected)
What two categories can hypertension be divided into?
Secondary/malignant hypertension and Primary/essential/benign hypertension
What are the genetic predispositions towards hypertension?
Candidate genes for angiotensin converting enzyme, renin and nitric oxide synthase
What is interesting about the gene coding for angiotensinogen?
Polymorhpisms are linked to increased circulating levels of angiotensinogen and increased blood pressure levels
What environmental factors contribute to hypertension?
High sodium levels, stress, smoking and inactivity
What conditions have an increased of occuring if hypertension is present?
Atehrosclerosis and related complications Left ventricular hypertrophy Cardiac Failure Cerebral haemorrhage Aortic dissection Small blood vessel disease Renal insufficiency and renal failure
What is aortic dissection?
When blood enters the aorta and dissects along its different tunics which can potentially occlude major vessel branches and aortic rupture
What is heart failure?
Failure of the heart to maintain an output of blood that is adequate for the demands of the body
What is low output heart failure?
Failure to maintain normal cardiac output because of conditions which affect the heart
What is high output heart failure?
The heart is unable to meet the increased demand for blood by the body
What is the naming system for heart failure?
Acute/Chronic, Left/right/both, high/low
What are the adaptive mechanisms which are initially used in heart failure to maintain cardiac output?
Hypertrophy
Dilatation
Increased Circulating volume (via Renin-Angiotensin-Aldosterone axis)
Increased Catecholamine release from adrenal glands and Sympathetic nervous system
What is cardiac decompenstion?
If the heart failure is progressive or prolonged, the adaptions will not be effective and infact may cause harm as the hypertrophied cardiac myocytes will result in an increased metabolic demand not able to be met by the coronary blood supply and increased dilation results in mechanical disadvantage while pumping
What are the end results of heart failure?
Reduced cardiac output with hypoxic effects on other organs
Damming back of blood in veins with congestive effects on multiple organs
What causes tissue oedema?
The tightly controlled homeostatic mechanisms which regulate vessel wall integrity and osmolarity of the blood are changed, resulting in there being a large osmotic gradient for fluid flow into the tissue, if fluid flow exceeds the draining capacity of the lymphatic system then fluid build up occurs
What causes inflammatory oedema?
Increased blood flow and vascular permeability with oedema fluid being the protein rich exidate with >1.02 gravity
This process is actively controlled
What occurs in non-inflammatory oedema?
The fluid is protein poor transudate with <1.02 gravity
What are the causes of non-inflammatory oedema?
Increased intravascular hydrostatic pressure
Reduced plasma osmotic pressure
Lymphatic obstruction
Sodium rentention
What is hyperaemia?
Active process in which arteriolar dilatation increases inflow to a capillary bed
What is congestion?
Passive process where there is decreased outflow from a capillary bed resultin in a build up of fluid in the capillaries this can be a systemic process from heart failure or a local process from loacised venous obstruction/oedema
What is haemorrhage?
Loss of blood due to vessel rupture, occurs from vessel injury caused by trauma,atherosclerosis or erosion
What are haemorrhagic diatheses?
Disease that increase the risk of haemorrhage including low platelet counts, clotting factor defects and vessel fragility
What is thrombocytopaenia?
Low platelet count
What is amyloidosis?
Increased vessel fragility
What is haematoma?
Haemorrhages enclosed in tissue
What factors influence the clinical relevance of haemorrhages?
The volume of blood lost and the location in which it occurs as even small haemorrhages in places like the brain can have significant effects
What is shock?
When there is a systemic hypofusion caused by a reduction in cardiac output and/or reduction in effective circulating volume
