Index
The essential functions of the circulatory system are to carry oxygen and nutrients to the cells of the body and the elimination of waste.
The heart, blood, and blood vessels work together to care for the body’s cells.
Using the network of arteries, veins, and capillaries, the blood carries carbon dioxide to the lungs (for exhalation) and picks up oxygen. The blood collects food nutrients from the small intestine and delivers them to each cell.
The blood
Blood is made up of:
- Red blood cells are responsible for transporting oxygen.
- White blood cells are part of the immune system.
- Platelets are necessary for clotting.
- Plasma is the fluid that carries blood cells, nutrients, and waste.
The heart
The heart pumps blood around the body. It is located inside the chest, in front of the lungs, and slightly to the left side.
The heart is a double pump made up of four chambers, with the blood flow going in one direction due to the presence of the heart valves.
The contractions of the chambers make the sound of the heartbeat.
The heart is a robust muscular bag that, by alternately relaxing and contracting, acts as a pump. Each cycle of relaxation and contraction forms a unique heartbeat, which we call a pulse.
The blood circulating through the body and head reaches through large veins (vena cava) to the right side of the heart. The right side of the heart is divided into an upper and lower chamber (space) separated by a one-way valve.
As the heart squeezes (contracts), blood is pushed through this valve and into the lungs through a blood vessel known as the pulmonary artery.
The blood then passes through the lungs, where it absorbs oxygen from the air we breathe with each breath.
The blood, now filled with oxygen, returns to the left side of the heart through the pulmonary vein, first to the upper chamber and then to the lower section. It is finally squeezed into the aorta, the large artery that exits from the left side of the heart.
The blood then passes around the body and head, releasing its valuable oxygen load before returning through the vena cava to begin the whole process again.
The right side of the heart
The upper right chamber (atrium) absorbs deoxygenated blood loaded with carbon dioxide. Blood is squeezed into the lower right chamber (ventricle) and carried by an artery to the lungs, where carbon dioxide is replaced with oxygen.
The left side of the heart
The oxygenated blood travels back to the heart, entering the upper left chamber (atrium). It is pumped into the lower left chamber (ventricle) and then into the aorta (an artery). The blood begins its journey around the body once more.
Blood vessels
Blood vessels have a range of different sizes and structures, depending on their role in the body.
The arteries
The arteries have relatively muscular solid walls that are difficult to stretch but are ideal for maintaining pressure. They can cope with fluctuations in pressure caused by alternative contraction and relaxation of the heart.
Oxygenated blood is pumped from the heart through the muscular arteries.
The arteries divide like tree branches until they are thin.
The largest artery is the aorta, connecting to the heart and collecting oxygenated blood from the left ventricle. The only artery containing deoxygenated blood is the pulmonary artery, which runs between the heart and the lungs.
Capillaries
The arteries eventually divide into the smallest blood vessel, the capillary. Capillaries are so tiny that blood cells can only move through them one at a time.
Oxygen and nutrients from food pass from these capillaries to the cells. Capillaries are also connected to veins, so waste from cells can be transferred to the blood.
The veins
Veins are thinner-walled with less or little muscle. They cannot maintain pressure in the same way as arteries.
By joining the arteries with the veins, there are small arteries known as arterioles, which become smaller capillaries, merging to form the larger venules, developing more prominent veins.
When the blood returns to the veins, most blood pressure has dropped, making the venous system low in force.
Veins have one-way valves instead of muscles to prevent blood from going back the wrong way. In general, veins carry deoxygenated blood from the body to the heart, where it can be sent to the lungs.
The exception is the network of pulmonary veins, which carry oxygenated blood from the lungs to the heart.
Blood pressure
Blood pressure refers to the pressure within the circulatory system as the blood is pumped.
Arteries, due to the condition of their walls, are difficult to stretch and, therefore, cause an increase in pressure within them, which we measure as blood pressure.
Circulatory insufficiency
Blood is so important because all living tissues and cells need oxygen to grow, repair, and reproduce.
The term “circulatory insufficiency” characterizes any condition in which the blood pressure and, consequently, the capillary current are reduced. If continued for a long time, the functions of normal organs are affected, and those of organs previously upset are disabled.
This is a complicated syndrome characterized by abnormalities of the myocardial contractile activity or vascular pathology that results in organs and tissues not receiving the required amount of blood. At the same time, the venous flow does not change or increase.
Types of circulatory failure
Generalized circulatory failure
Generalized circulatory failure occurs when blood flow is not provided adequately to all tissues
- Cardiac: in cases of heart failure, decreased cardiac output.
- Vascular: decreased RP
- Hematic: when there is little blood volume due to bleeding, dehydration, or caused by some diseases.
Local circulatory insufficiency
- Arterial ischemia.
- Venous insufficiency.
Cardiogenic shock
Circulatory failure can lead to collapse. Cardiogenic shock is a clinical syndrome in which a primary circulatory problem causes poor oxygen supply to peripheral organs and tissues.
Without rapid identification, restoration of oxygen supply, and treatment directed at the underlying cause, a process of progressive multi-organ dysfunction and sequential organ failure will lead to death.
Causes
Cardiogenic shock usually occurs in the setting of a large myocardial infarction or a complication of one, such as acute mitral regurgitation or tamponade.
Ventricular deterioration causes a drop in stroke volume and a resulting drop in cardiac output. Blood pressure depends on cardiac output and peripheral resistance.
Clinical characteristics of the condition
The wide range in the etiology of cardiogenic shock is reflected in the diversity of clinical features. Impaired oxygen supply will eventually affect all systems.
Their history and clinical findings can often identify the cause of a patient suffering cardiogenic shock.
For example, a 50-year-old man with a history of hypertension and diabetes who develops severe central chest pain and is cold, clammy, and hypotensive is more likely to experience cardiogenic shock due to an acute heart attack.
However, there may be considerable overlap in clinical syndromes, especially if mixed etiologies or later presentation in the disease.
Compensatory mechanisms for maintaining systemic blood pressure through increased resistance include high levels of catecholamines, activation of the RAA system, and vasopressin release.
Unfortunately, these tend to cause a more excellent compromise in oxygen supply through severe vasoconstriction and increased subsequent loading.
Hypoperfusion of the coronary artery due to hypotension exacerbates the problem, and in a vicious cycle, it can spiral to death.
Emergency management
If not treated urgently or aggressively, the shock of any etiology will lead to death.
With any critically ill patient, you should start with the following approach:
- An (airway).
- B (breathing).
- C (circulation).
Suppose your patient does not have a patent airway, adequate respiratory effort, or pulse. In that case, they should follow a well-rehearsed advanced life support algorithm, including airway maneuvers, bag-mask ventilation, tracheal intubation, CPR, vasoactive drugs, and defibrillation.
Elective intubation and mechanical ventilation should be considered in advance for any patient with cardiogenic shock to maximize oxygen delivery, reduce respiratory oxygen consumption, eliminate carbon dioxide and improve acidosis.
This must be balanced with the potential for further cardiovascular collapse, which can occur due to the reduced sympathetic drive and decreased venous return with sedation and positive intrathoracic pressure.
Diagnosis
The differential diagnosis of a shocked patient is comprehensive. Establishing a specific diagnosis can be as easy as spotting the knife sticking out of your chest. However, patients may present obtuse, hypotensive, and acidotic with minimal clues to the cause on physical examination.
In the acute setting, recognition of the shocked patient followed by resuscitation according to the above approach takes precedence over the specific diagnosis, which may require a panel of additional investigations, collateral history, and a comprehensive examination.
However, making a specific diagnosis is critically important because each cause of cardiogenic shock has particular considerations that, if left unmanaged and treated, will lead to additional morbidity and mortality.
To achieve a specific diagnosis, the following approach is recommended:
- In principle, the diagnostic approach to shock is the same as in any other presentation: combining history taking, physical examination, routine and specialized investigations, and imaging. However, due to the seriousness of the situation, this must be done quickly and simultaneously with resuscitation measures.
- Attempts should be made to match the findings of history, examination, and investigations with the three categories of shock described above, remembering that the characteristics of all three may coexist and that the different underlying etiologies may have similar clinical features but other management.
For example, tamponade, cardiogenic shock, and massive pulmonary embolism may present with cold, closed peripheries, tachypnea, tachycardia, hypotension, and elevated JVP, but treatment is different.
History
All aspects of the classic medical history can provide vital information for the diagnosis, tailored treatment, and prognosis.
In addition to the symptoms and circumstances that precipitate the presentation, ensure an accurate history of comorbidities, vulnerability to disease (cardiac/immunosuppressive / bleeding tendency), drugs and allergies, and physical functional status.
Information on tobacco, alcohol and illicit drug use should be sought.
Collateral history from relatives or family doctors may be needed.
Physical exam
The physical examination should be comprehensive and achieve:
- Accurate measurement of vital signs (heart rate, postural blood pressure, respiratory rate, oxygen saturation, temperature, capillary blood glucose).
- An airway assessment, including compromise due to reduced consciousness (GCS <8).
- Complete chest examination and adequacy of respiratory effort and oxygenation.
- A cardiovascular examination, paying particular attention to (a) whether the patient is warm and vasodilated or cold, moist and vasoconstriction; and (b) the degree of hypotension if present (postural maneuvers can provoke it).
- Abdominal examination: tenderness, distension, organomegaly, and altered bowel sounds should be carefully examined.
- Neurological examination: evaluation of GCS, pupillary reflexes, meningism, and localization signs.
Diagnostic tests
Diagnostic tests should not delay essential treatment. The actual tests are:
- Biochemistry.
- Hematology.
- Urine analysis.
- Gasometría arterial.
- Electrocardiogram.
- Chest X-ray.
- Image tests.
Treatment
The critical components of the successful management of cardiogenic shock are:
- Early recognition and immediate action.
- Make sure a qualified team, including an experienced doctor, works together.
- Management of the patient in an appropriate environment such as a resuscitation room or a coronary care unit.
- Follow a logical ABC approach (airway, breathing, circulation).
- Address the treatable components of the shock: rhythm and classification control, optimize preload, afterload and contractility.
- Establish adequate monitoring: cardiac monitor, pulse oximeter, arterial cannula, central venous catheter, urinary catheter, hemodynamic monitoring (cardiac output).
Diagnostic tests, history taking, clinical examination, the establishment of monitoring devices, and specific treatments that depend on the etiology must be performed in parallel with resuscitation.
