Cardio deck Flashcards
What is systole?
The contraction of the right and left ventricles, which creates the maximum arterial pressure
What is diastole?
The relaxation of the heart while the ventricles fill with blood, which produces the minimum arterial pressure
At what rate do the ventricles pump blood into the arteries?
Between 60-80 times/minute
What is a pulse?
The force of ventricular contraction starts a wave of increased pressure that begins at the heart and travels along the arteries, which is known as the pulse
Where can you find pulses along the surface of the body?
Carotid pulse
Radial pulse
Femoral pulse - felt in the groin in the anterior crease between the leg and abdomen at a point approximately at the middle of the crease
dorsal pedis pulse - felt on the top of the foot
Posterior tibialis pulse - felt on the inside of the foot, behind the ankle
What is blood pressure?
It is the force exerted by the blood against the walls of the arteries as it passes through them. The repeated ejection of blood from the left ventricle of the heart into the aorta is transmitted through the arteries as a series of pressure waves
How is blood pressure measured?
Two measurements are taken:
1. Systolic pressure: the maximum pressure occurring at the peak of the left ventricular contraction
2. Diastolic pressure: the minimum pressure during relaxation of the left ventricle.
What factors control arterial blood pressure?
The blood volume, the state of the arteries and arterioles (dilated or constricted), and the capacity of the heart muscle to contract normally
Is venous blood pressure greater or weaker than arterial blood pressure? And what factors control venous blood pressure?
Venous blood pressure is weaker than arterial blood pressure.
Venous blood pressure is affected by blood volume and the capacity of the veins.
How much blood volume does the average adult body have?
6L (10 pints) of blood. However, the capacity of all the body’s blood vessels is much larger than 6L.
What does loss of normal blood pressure indicate?
It can indicate that the blood cannot circulate efficiently to the body’s organs, resulting in inadequate perfusion of the body’s organs. The state of inadequate perfusion is called shock.
What is the primary objective in the treatment of shock?
To increase tissue perfusion
What transport category is someone with shock in?
RTC
What is the main cause of shock in injured patients?
Shock is almost always caused by blood loss (hypovolemic shock) in injured patients
What are the 3 main causes of inadequate perfusion?
- The volume of blood in circulation becomes inadequate, resulting in hypovolemic shock:
- Blood loss
- Fluid loss i.e. burns, vomiting, diarrhoea - The heart is damaged and fails to function properly:
- cardiogenic shock (MI) - The blood vessels dilate excessively. In this situation, the normal blood volume is insuccient to fill the dilated blood vessels to capacity. This leads to inadequate tissue perfusion:
- Anaphylactic shock
- Septic shock
- Neurogenic shock (spinal)
Which 2 factors control blood pressure? What regulates these factors?
- The resistance to flow of the circulating blood by the arterioles (arteriolar or peripheral resistance)
- The volume of blood pumped by the heart into the systemic circulation (cardiac output)
The autonomic nervous system matches CO to peripheral resistance to maintain the blood pressure and ensure adequate perfusion of the cells as their needs change
What are the 2 key hormones in the cardiovascular system that regulate blood pressure and how do they work?
Any change in CO will tend to cause a reduction in systolic pressure. This change in pressure is detected by special pressure receptors. The receptors trigger the ANS, which attempts to restore CO and BP to normal. The 2 key hormones in this system are adrenalin and noradrenalin?
Adrenaline and noradrenalin cause:
- An increase in heart rate and a more forceful contraction. These increase CO and BP.
- Vasoconstriction (constriction of arterioles) in non-vital organs, decreasing blood flow to these organs, which redistributes blood flow to the vital organs
- Diaphoresis (sweating). This can increase fluid loss and aggravate shock. The OFA attendant must watch for this effect as it is a key sign in the detection of shock.
How does the body compensate for hypovolemic shock?
Releasing large amounts of adrenaline and noradrenalin to increase blood volume, as well as redistribute blood flow to vital organs and away from non-vital organs through vasoconstriction
Describe the cascade of effects of hypovolemic shock:
- Decreased blood volume
- Inadequate venous return
- Decreased CO (Cardiogenic shock)
- Blood pressure falls
- ANS stimulated
- Peripheral blood vessels constrict - leading to cool skin, pallor, and sweating (identify these)
- Increased CO (increased HR) - sign of ANS activation
- BP rises briefly, the lowers - evident through weak/absent limb pulses
- Inadequate perfusion of vital organs - altered LOC, air hunger, increased respiratory rate
- Death
What are the 5 types of shock
- Hypovolemic
- Cardiogenic
- Anaphylactic
- Septic/Bacteremic
- Neurogenic
What are the signs and symptoms of hypovolemic shock?
Hypovolemic shock is primarily caused by excessive blood loss through a traumatic injury, but can also be due to excessive fluid loss due to prodound diarrhoea, vomiting, or when a patient has extensive burns.
The symptoms include:
- COOL SKIN - when warm blood is re-routed from the skin as a consequence of vasoconstriction
- PALLOR - with vasoconstriction, blood is no longer flowing to the body’s surface, giving a more ‘white-ish’ appearance
- SWEATING - This develops as a direct effect on the sweat glands because of ANS response to shock
- INCREASED HR (usually >100 BPM) - due to ANS activation and release of adrenaline and noradrenalin, indicating more severe shock
- LOW BP (HYPOTENSION) - defined as systolic pressure less than 100 mmHg measured on a blood pressure cuff. Alternatively, the absence of radial pulses indicates a BP reading of less than 90 mmHg. Weak or absent pulses indicate hypotension, which is a late sign of shock and indicates a massive loss of blood volume with inability to compensate
- ALTERED LOC - in its early stages, shcok is often associated with anxiety, restlessness, or combativeness. This is due in part to the release of adrenalin. As shock increases and hypoxia become smore pronounced, the patient may become very agitated and restless. As perfusion of the brain decreases, LOC increases.
- TACHYPNEA - increased respiratory rate of between 20-30 breaths/min - usually a patient in shock breathes more rapidly and can gasp for breath with ‘air hunger’ as a consequence of hypoxia and acidosis. This may also be present with associated chest injuries. The OFA attendant must be very concerned about an associated chest injury if the respiratory rate is greater than 30 breaths/min
- THIRST - owing to a reduced blood volume, patients in shock often complain of intense thirst. The patient should be given nothing by mouth in case surgery is needed
Which patients with hypovolemic shock must receive special consideration?
- Athletes - Athletes have a well-conditioned heart muscle and CV system, which means their HR may be below 50 BPM. Despite significant blood loss, their body may compensate for shock and not display an increased HR or diminished BP until either a large volume of blood has been lost or shock state has become advanced
- Pregnant women - During pregnancy, a woman will have up to 20% increase in blood volume. Consequently, following trauama, she may not initially exhibit signs of shock. The fetus, however, will experience profound shock as the maternal vasoconstrictive response to shock shunts the blood from the fetus to the maternal vital organs. Any pregnant woman who has received trauma, even if insignificant, should be referred to a physician for assessment
- Cardiac patients: There are 2 major complications with cardiac patients
a) Cardiac patients are at higher risk of developing shock from trauma because of their weaker hearts, and hence are more likely to have chest pain and/or dyspnea
b) Patients on heart medication may not exhibit the early signs of shock because these medications dampen the body’s normal vasoconstrictive response+
Describe cardiogenic shock, its most common causes, and the signs and symptoms:
In cardiogenic shock, the heart muscle does not pump enough blood to peripheral tissues.
The most common cause is acute MI. The strength and force of the left ventricular contraction is reduced because of the extensive structural damage to the ventricle wall. Congestive heart failure and chest trauma can also cause cardiogenic shock.
The signs and symptoms are the same as hypovolemic shock: cool skin, pallor, sweating, increased HR, hypotension, altered LOC, tachypnea, thirst
Describe anaphylactic shock and its main causes
This condition is caused by a severe allergic reaction. It may be caused by the injection, ingestion, or inhalation of a roeign protein substance into a person sensitised to it. The allergic reaction may lead to a loss of the normal tone of the blood vessels. The shock state is caused by abnormal systemic dilation of the blood vessels (vasodilation), cause the blood pressure to drop and resulting in body-wide inadequate perfusion of the cells.
What are the main agents that can cause anaphylactic shock?
Insect stings, antibiotics, seafood, nuts, and blood or other transfusion.