chapter 15 - blood patho Flashcards
Describe how obstructive shock develops in trauma, in particular due to tension pneumothorax and cardiac tamponade..
obstructive shock occurs when blood flow in the heart or great vessels becomes blocked.
two most common examples are: tension pneumothorax and cardiac tamponade
tension pneumothorax
caused by damage to the lung tissue.
air form lung escapes into chest cavity.
air accumulates in chest cavity and applies pressure to the mediastinum.
when the trapped air shifts organs to the uninjured side, a pneumothorax becomes a tension pneumothorax.
pneumothorax is a resp. problem but tension pneumothorax causes kinking of the vena cava.
treatment: decompression of the injured side of the chest is the cure for tension pneumothorax.
Cardiac Tamponade
caused by blunt or penetrating trauma, tumours, or pericarditis.
progresses quickly.
occurs when blood leaks into pericardium, causing accumulation of blood in the pericardial sac.
compresses the heart.
pericardium has minimal stretch. the more blood that fills the sac prevents the heart form expanding and chambers refilling.
signs: tachycardia, small QRS, muffled heart sounds, systolic and diastolic pressure merge.
treatment: drain the pericardial sac
Describe how distributive shock develops, in particular due to sepsis and anaphylaxis
occurs when there is wide spread dilation of resistance vessels (small arterioles), the capacitance vessels (small venules), or both.
blood volume pools in the expanded vascular beds and tissue perfusion decreases.
4 most common types of distributive shock
septic shock
anaphylactic shock
neurogenic shock
psychogenic shock
Septic shock
is defined as the presence of sepsis syndrome, systolic less then 90mmHg or systolic 40mmHg below baseline.
Systemic inflammatory response syndrome is defined as presence of 2 or more of the following in the presence of a trigger such as burns, trauma, pancreatitis, bacterial infection, or hypovolaemia:
temp >38.3 or <36
HR > 90
Tachypnea >20
White cell count <4 or >12
in the presence of suspected infection it is known as sepsis.
if the sepsis results in organ failure its known as severe sepsis.
This can progress to multiple organ dysfunction syndrome and/or septic shock if the blood pressure is non-responsive to fluid boluses.
Sepsis occurs due to widespread infection
The infection activates inflammatory immune response. Resulting in:
increased microvascular permeability (leaky capillaries)
vasodilation
third-space fluid shifts
micro-thrombi formation
in some patients unregulated inflammatory response occurs, resulting in hypoperfusion to the cells owing to opening of arteriovenous shunts, tissue destruction, and organ death.
septic shock causes blood to leak out of the vascular system (hypovolaemia).
The fluid that leaks out often collects in the resp. system, interfering with ventilation.
lastly a larger-then-normal vascular bed is asked to contain a smaller-then-normal volume of intravascular fluid.
Anaphylactic Shock
is a sever, life threatening, generalised or systemic hypersensitivity reaction.
It occurs when a person reacts violently to a substance to which they have been sensitised.
sensitisation means developing a heightened reaction to a substance.
An allergic reaction typically does not occur, or occurs in a milder form., during sensitisation.
each subsequent sensitisation produces more severe reactions.
In anaphylactic shock there is no blood loss, minor vascular damage, and only a slight possibility of direct cardiac muscular injury.
The patient experiences widespread vascular dilation, resulting in relative hypovolaemia. In other words, relative to the now larger container, the normal blood volume is less.
The combination of poor oxygenation and poor perfusion can be fatal.
in anaphylaxis immune system chemicals such as histamine and other vasodilator proteins are released when exposed to an allergen.
Their release causes the sever bronco-constriction accounting for wheezing.
Also accompanied by urticarial (hives), wide-spread vasodilation, which causes distributive shock, and blood vessels that continue to leak.
Fluids leak out of blood vessels and into interstitial space, resulting in hypovolaemia and potentially causing swelling.
In some cases this swelling may occlude the upper airway.
Recurrent large areas of subcutaneous oedema of sudden onset, usually disappearing within 24 hours and mainly seen in young women, are called ‘angioedema’.
Describe the pathological processes which lead to acute coronary syndrome, in particular atherosclerosis
ACS is the term used to describe any group of clinical symptoms consistent with acute myocardial ischaemia.
Acute myocardial ischaemia typically presents as chest pain because of insufficient blood supply to the heart muscle, which itself is a result of coronary heart disease (CHD).
A 12 lead ECG can determine if there is any ST-segment elevation
Most patients whose ECG displays ST segment elevation will ultimately develop a Q-wave AMI (heart attack), also known as STEMI (ST-elevation myocardial infarction)
Patients who have ischaemic discomfort (chest pain) without ST-segment elevation are having unstable angina or a non-ST segment elevation AMI that usually leads to a non-Q-wave AMI; these conditions are collectively known as UAP/NSTEMI (unstable angina pectoris/non-ST-segment myocardial infarction).
Patients to experience angina may also present with ST segment depression.
some patients experiencing angina or AMI may have no changes indicated by the ECG
ACS management
Not all chest pain is caused by cardiac ischemia or injury.
Many other conditions such as: pulmonary embolism, pneumothorax, pneumonia, pericarditis, aortic dissection, indigestion, and peptic ulcer.
Can cause chest pain that can be mistaken for angina or an Acute Myocardial Infarction (AMI).
Angina Pectoris
Angina pectoris, literally “choking in the chest”
the principal symptom of coronary artery disease (CAD)
Angina occurs when the supply of oxygen to the myocardium is insufficient to meet the demand.
As a result, the cardiac muscle becomes ischaemic, and a switch to anaerobic metabolism leads to the accumulation of lactic acid and carbon dioxide.
The concept of supply and demand is critical here. When at rest, a person with heart disease may have an adequate supply of oxygen to the heart to meet these sedentary needs, despite some narrowing of the coronary arteries.
When the same person exercises or experiences some other stress, however, the blood flow to the myocardium may not be able to satisfy the hearts increased demand oxygen; in that case, angina will result.
Clearly, the patient who experiences angina at rest, when oxygen needs are minimal, has more severe CAD than a person who experiences angina only with vigourous exercise.
Stable Angina
Stable angina follows a recurrent pattern. A person with stable angina experiences pain after a certain, predictable amount of exertion. The pain and also has a predictable location, Intensity, and duration.
treatment: patients with chronic, stable angina often take GTN or some other form of nitrate for relief of anginal pain.
Unstable Angina
Unstable angina is much more serious then stable angina and indicates a greater degree of obstruction of the coronary arteries.
It is characterised by noticeable changes in frequency, severity, and duration of pain and often occurs without predictable stress.
The patient may report that the anginal attacks have grown more frequent and severe during the past several days or weeks.
Or that they awaken them from sleep or occur when otherwise at rest.
Such attacks are often warning signs of impending AMI
Acute Myocardial Infarction (AMI)
A heart attack.
Occurs when a portion of the cardiac muscle is deprived of coronary blood flow for long enough to cause portions of the muscle to die (to undergo necrosis or infarct).
Several things can diminish flow through coronary vessels, especially if the vessels are already narrowed by atherosclerotic disease.
Conclusion of a coronary artery by blood clot (thrombus)
Spasm of coronary artery
Reduction of overall bloodflow from any cause. Such a shock, arrhythmias, or pulmonary embolism.
The location and size of a myocardial infarction depend on which coronary artery is blocked and where along its course the blockage occurred.
Majority of infarcts involve the left ventricle. When the anterior, lateral, or septal walls of the left ventricle are infarcted, the source is usually occlusion of the left coronary artery or one of its branches.
Inferior wall infarcts are usually the result of RCA occlusion.
When the ischaemic process affects only the inner layer of muscle, the infarct is referred to as subendocardial.
When the infarct extends through the entire wall of the ventricle, it is a transmural AMI giving a Q-wave.
The infarcted tissue is invariably surrounded by a ring of ischaemic tissue, an area that is relatively deprived of oxygen but still viable.
That ischaemic tissue tends to be electrically unstable and is often the source of cardiac arrhythmias.
Cardiogenic shock
Cardiogenic shock is a condition in which your heart suddenly can’t pump enough blood to meet your body’s needs.
The condition is most often caused by a severe heart attack, but not everyone who has a heart attack has cardiogenic shock.
If treated immediately, about half the people who develop the condition survive.
symptoms:
pulmonary congestion - DIB, productive cough with a lot of fluid.
Jugular vein distention
Angina - heart gets starved for oxygen
organ failure and organ dysfunction due to decreased oxygenation.
cool skin
Heart failure
Valve problems - could cause difficulty for blood to flow
Arrhythmia’s - issue with electric conduction
contractility - stiffness of wall of heart, means it cant pump properly
these things lead to cardiogenic shock. which causes fluid overload - backing up of blood in the vascular system.
Congestive heart failure is characterised as left or right sided depending on which ventricle is compromised.
The most common cause of right ventricle failure is left heart failure.
