STUDY - Technical - New Dacian's Medicine
The
Shock (4)
Translation Draft
Let's finish the shock... with the presentation of elements about the patient's approach.
Shock is an emergency and, for this reason, the optimal approach involves a balance between the need to institute therapy before the shock causes irreversible damage to the vital organs and the need to do a full clinical examination, necessary to understand the cause of the shock and indicate appropriate treatment. A practical way is to quickly make an initial assessment, based on a short anamnesis and clinical examination, and to initiate specific diagnostic procedures to determine the cause and severity of the shock.
Initial laboratory tests generally include a chest X-ray, electrocardiogram, measurement of gases and electrolytes in arterial blood, a complete hemogram and other tests suggested by problems discovered after initial examination. The catheterization of straight hearts with a balloon-directed flow catheter (Swan-Ganz) is frequently useful. While this short evaluation is carried out, therapy should be initiated. After stabilisation, a more thorough diagnostic evaluation will be made and the response to the initial therapy will be assessed.
Now, a few details about catheterizing the right heart for shock evaluation. Different shock categories have different hemodynamic characteristics. Patients with mild hypovolemic shock can be successfully treated by simple rehydration. However, in patients with moderate or severe shock, right heart catheterization is often useful, not only for conducting a diagnostic assessment of the hemodynamic condition, but also for monitoring the response to therapy, since noninvasive evaluation is often incorrect in estimating fill pressure and cardiac flow.
So patients may have hemodynamic data encountered in several types of shock, but when they are combined with clinical data and the evaluation of systemic vascular resistance, etiology can be determined in most cases.
From a treatment point of view there are some general principles. Whenever possible, the patient should be treated in an intensive care unit. Continuous electrocardiographic monitoring should be carried out for the detection of rhythm disorders and an arterial approach to measuring blood pressure at each heart attack. Pulsoximetry is frequently useful for determining fluctuations in arterial oxygenation. In most cases of shock that cannot be treated quickly, serial determinations of right and left ventricular filling pressures and cardiac flow should be made.
Arterial gases, plasma electrolytes, complete haemogram and clotting times should also be determined frequently to monitor the patient's progress and monitor the effects of therapy. Serum values of calcium, phosphorus and magnesium should also be measured, because substantial reductions in these ions are associated with depression of myocardial function and respiratory muscles. The frequency of measurements depends on clinical development and the need to monitor the response to treatment.
In general, the purposes of shock treatment are to maintain average arterial pressure and ensure adequate infusion and supply of oxygen and other nutrients to vital organs. Tissue hypoperfusion and anaerobic metabolism can lead to the formation and release of lactic acid into circulation. A reduction in high serum lactate levels is a good indicator of successful resuscitation and is often used for therapeutic purposes. In addition to these general purposes, specific forms of shock require targeted treatment of characteristic physiopathological processes.
We will approach this "oriented" treatment according to the different types of shock, starting with hypovolemic shock. Liquid infusion is the fundamental treatment of acute hypovolemia. The aim is to quickly and adequately restore cardiac filling pressures to an optimal level without inducing a pulmonary edema and compromising oxygenation.
The marked increase in pressure in the pulmonary microvessels is the most important determinant of fluid transweld into the pulmonary interstitial. The clinical implication of this observation is that monitoring of pulmonary hydrostatic pressure, by physical examination or measured hemodynamically, is essential during resuscitation. Regardless of the type and amount of fluids used in resuscitation, it is imperative to use physiological standards to measure the initial response to treatment and to adapt therapy to the individual needs of the patient.
For initial resuscitation, in most forms of hypovolemic shock are used either crystalloid solutions or physiological ones or Ringer. After initial resuscitation with several liters of crystalloid solutions, the use of colloidal solutions, such as albumin or starch solutions, has been described as a faster and more effective method of vascular volume restoration, a method that can help maintain optimal osmotic colloid pressure.
However, colloidal solutions are expensive and, despite numerous studies, no net benefit of colloids administration has been demonstrated over crystalloids in the restoration of vascular volume. Preliminary studies with hypertone saline solutions suggest that effective resuscitation can be performed with relatively small volumes of fluid, in some cases, such as burning resuscitation, this limitation of the volume of fluid administered may be important. In hemorrhagic shock, the restoration of oxygen transport capacity is achieved by erythrocytic mass transfusion, with the aim of maintaining a haemoglobin concentration of 10 g/dl.
In cardiogenic shock due to acute myocardial infarction, treatment should be directed towards, inducing myocardial ischemia and saving the ischemic but viable myocardium from the edge of the infarcted area. Initial measures include supplementation of oxygen intake and, when systolic blood pressure allows, intravenous nitroglycerin administration. Inserting an intraaortic balloon probe decreases the post-pregnancy ventricle, improving performance and reducing the oxygen demand of the myocardium, with improvement of coronary infusion pressure by increasing diastolic pressure in the aorta.
The possibility of acute installation of mechanical abnormalities, such as mitral insufficiency or ventricular septum defect, should be excluded by means of echocardiography or catheterization of the right heart. When possible, performing a coronary angiography in an emergency, to determine the anatomy of the coronarys and try revascularization, is the best solution. Studies on revascularization, conducted either by angioplasty or by bypass in patients with cardiogenic shock, suggest that the survival rate is highest compared to classical therapy.
The administration of thrombolytic agents is an alternative, although a decrease in mortality in patients with myocardial infarction and cardiogenic shock has not been clinically demonstrated (through clinical trials). Cardiogenic shock may also occur after a prolonged cardiopulmonary bypass, with the siderate myocardium requiring hours or days to recover sufficiently to resume function. Treatment consists of cardiovascular support with a combination of inotropic agents such as dopamine, dobutamine or amrinone and an intraaortic contrapulsion balloon.
Dopamine, which acts directly on beta1-adrenergic receptors in the myocardium and indirectly through the release of norepinephrine, has both inotropic and vasopressive effects. tachycardia and increased peripheral resistance after dopamine administration may accentuate myocardial ischemia. Dobutamine, a selective beta1-adrenergic agent, can improve myocardial contractility and increase heart rate without causing marked changes in heart rate or systemic vascular resistance.
Amrinone and milrinone are phosphodiesterase inhibitors, with both positive and vasodilating inotropic effects. They have longer half-life than dobutamine and can cause hypotension, so they are used when other therapeutic agents have proven ineffective. Because it does not act directly on adrenergic receptors, it may be useful in situations where the number of beta-adrenergic receptors is diminished. The combination of amrinone or milrinone with dopamine or dobutamine may be considered in patients who do not respond to monotherapy with one of these classes of medicines.
It's the turn of extracardiac obstructive shock. Cardiac tamponade is the prototype of extracardiac obstructive shock and can be recognized due to clinical manifestations (hypotension, paradoxical pulse, relaxed jugular veins) and characteristic echocardiographic aspects. Although the expansion of intravascular volume and sometimes the administration of vasopressor agents are useful timing measures, the only effective treatment being pericardial drainage by pericardiocentesis or surgical.
Pulmonary embolism is usually treated with anticoagulants, but when it is massive and causes insufficiency of the right ventricle and shock, thrombolytic treatment should be considered. In patients with contraindications for the latter, surgical pulmonary embolectomy is an alternative, if there is sufficient time for diagnosis, mobilization of the surgical team and the establishment of a cardiopulmonary bypass.
Treatment of septic shock has three main aspects. First the outbreak of infection should be identified and eliminated by surgical drainage or antibiotic treatment or both. Rapid establishment of appropriate antibiotic treatment has been associated with increased survival rate, but specific microorganisms that produce sepsis are not usually known when presenting the patient.
Thus, broad-spectrum antibiotics that are effective on most microorganisms should initially be administered, depending on the clinical condition of the patient and the type of antibiotic-resistant microorganisms in the hospital. Secondly, while the source of the infection is eradicated, an adequate infusion of organs and their function should be maintained through cardiovascular monitoring. Since antibiotic weather requires 48 hours or more to sterilize a septic outbreak, maintaining oxygen intake to tissues is essential for a further favorable development.
Because oxygen intake depends on haemoglobin concentration in the blood, oxygen saturation and cardiac flow, maintaining haemoglobin levels above 10 g/dL, oxygen saturation above 92% and adequate cardiac output are important therapeutic principles. Initially, cardiovascular therapy should optimize pre-pregnancy by volemic intake to maintain the blocking pressure in the pulmonary artery between 14 and 18 mmHg.
If serum albumin levels are low, increased intravascular oncotic pressure can be done by infusion of albumin concentrates. Because tissue hypoperfusion in sepsis occurs in part due to abnormal cardiac flow, it is sometimes recommended to increase cardiac output to a very high level above normal. However, it has not been demonstrated by controlled studies that the use of inotropic agents to achieve such flows would have a beneficial effect.
If only volemic expansion fails to maintain blood pressure and an adequate infusion of organs, treatment with vasopressor agents should be initiated. in patients with persistent hypotension, dopamine administration frequently increases blood pressure and maintains or increases blood flow to renal or splanhincirculation. Patients who remain hypotensive despite dopamine may be treated with norepinephrine, a stronger vasopressor.
Once hypotension has been corrected, it may be useful to increase the heart index with dobutamine to optimize oxygen intake to tissues. A third therapeutic objective is the interruption of the pathogenic sequence leading to septic shock. Several studies have shown that early administration of corticosteroids does not improve morbidity or mortality in septic shock. Newer therapies focused on inhibiting potentially toxic mediators such as endotoxin, TNF and IL-1. Studies with sepsis mediators, including anti-endotoxin antibodies, anti-TNF antibodies, IL-1 receptor antagonists and soluble TNF receptors, have not shown a significant reduction in the mortality of sepsis patients.
I'm done... Now, out of evil (out of shock), I'll give it in even worse. So, starting June 4, I'm going to tackle cardiovascular collapse, cardiac arrest and sudden cardiac death...
Let's finish the shock... with the presentation of elements about the patient's approach.
Shock is an emergency and, for this reason, the optimal approach involves a balance between the need to institute therapy before the shock causes irreversible damage to the vital organs and the need to do a full clinical examination, necessary to understand the cause of the shock and indicate appropriate treatment. A practical way is to quickly make an initial assessment, based on a short anamnesis and clinical examination, and to initiate specific diagnostic procedures to determine the cause and severity of the shock.
Initial laboratory tests generally include a chest X-ray, electrocardiogram, measurement of gases and electrolytes in arterial blood, a complete hemogram and other tests suggested by problems discovered after initial examination. The catheterization of straight hearts with a balloon-directed flow catheter (Swan-Ganz) is frequently useful. While this short evaluation is carried out, therapy should be initiated. After stabilisation, a more thorough diagnostic evaluation will be made and the response to the initial therapy will be assessed.
Now, a few details about catheterizing the right heart for shock evaluation. Different shock categories have different hemodynamic characteristics. Patients with mild hypovolemic shock can be successfully treated by simple rehydration. However, in patients with moderate or severe shock, right heart catheterization is often useful, not only for conducting a diagnostic assessment of the hemodynamic condition, but also for monitoring the response to therapy, since noninvasive evaluation is often incorrect in estimating fill pressure and cardiac flow.
So patients may have hemodynamic data encountered in several types of shock, but when they are combined with clinical data and the evaluation of systemic vascular resistance, etiology can be determined in most cases.
From a treatment point of view there are some general principles. Whenever possible, the patient should be treated in an intensive care unit. Continuous electrocardiographic monitoring should be carried out for the detection of rhythm disorders and an arterial approach to measuring blood pressure at each heart attack. Pulsoximetry is frequently useful for determining fluctuations in arterial oxygenation. In most cases of shock that cannot be treated quickly, serial determinations of right and left ventricular filling pressures and cardiac flow should be made.
Arterial gases, plasma electrolytes, complete haemogram and clotting times should also be determined frequently to monitor the patient's progress and monitor the effects of therapy. Serum values of calcium, phosphorus and magnesium should also be measured, because substantial reductions in these ions are associated with depression of myocardial function and respiratory muscles. The frequency of measurements depends on clinical development and the need to monitor the response to treatment.
In general, the purposes of shock treatment are to maintain average arterial pressure and ensure adequate infusion and supply of oxygen and other nutrients to vital organs. Tissue hypoperfusion and anaerobic metabolism can lead to the formation and release of lactic acid into circulation. A reduction in high serum lactate levels is a good indicator of successful resuscitation and is often used for therapeutic purposes. In addition to these general purposes, specific forms of shock require targeted treatment of characteristic physiopathological processes.
We will approach this "oriented" treatment according to the different types of shock, starting with hypovolemic shock. Liquid infusion is the fundamental treatment of acute hypovolemia. The aim is to quickly and adequately restore cardiac filling pressures to an optimal level without inducing a pulmonary edema and compromising oxygenation.
The marked increase in pressure in the pulmonary microvessels is the most important determinant of fluid transweld into the pulmonary interstitial. The clinical implication of this observation is that monitoring of pulmonary hydrostatic pressure, by physical examination or measured hemodynamically, is essential during resuscitation. Regardless of the type and amount of fluids used in resuscitation, it is imperative to use physiological standards to measure the initial response to treatment and to adapt therapy to the individual needs of the patient.
For initial resuscitation, in most forms of hypovolemic shock are used either crystalloid solutions or physiological ones or Ringer. After initial resuscitation with several liters of crystalloid solutions, the use of colloidal solutions, such as albumin or starch solutions, has been described as a faster and more effective method of vascular volume restoration, a method that can help maintain optimal osmotic colloid pressure.
However, colloidal solutions are expensive and, despite numerous studies, no net benefit of colloids administration has been demonstrated over crystalloids in the restoration of vascular volume. Preliminary studies with hypertone saline solutions suggest that effective resuscitation can be performed with relatively small volumes of fluid, in some cases, such as burning resuscitation, this limitation of the volume of fluid administered may be important. In hemorrhagic shock, the restoration of oxygen transport capacity is achieved by erythrocytic mass transfusion, with the aim of maintaining a haemoglobin concentration of 10 g/dl.
In cardiogenic shock due to acute myocardial infarction, treatment should be directed towards, inducing myocardial ischemia and saving the ischemic but viable myocardium from the edge of the infarcted area. Initial measures include supplementation of oxygen intake and, when systolic blood pressure allows, intravenous nitroglycerin administration. Inserting an intraaortic balloon probe decreases the post-pregnancy ventricle, improving performance and reducing the oxygen demand of the myocardium, with improvement of coronary infusion pressure by increasing diastolic pressure in the aorta.
The possibility of acute installation of mechanical abnormalities, such as mitral insufficiency or ventricular septum defect, should be excluded by means of echocardiography or catheterization of the right heart. When possible, performing a coronary angiography in an emergency, to determine the anatomy of the coronarys and try revascularization, is the best solution. Studies on revascularization, conducted either by angioplasty or by bypass in patients with cardiogenic shock, suggest that the survival rate is highest compared to classical therapy.
The administration of thrombolytic agents is an alternative, although a decrease in mortality in patients with myocardial infarction and cardiogenic shock has not been clinically demonstrated (through clinical trials). Cardiogenic shock may also occur after a prolonged cardiopulmonary bypass, with the siderate myocardium requiring hours or days to recover sufficiently to resume function. Treatment consists of cardiovascular support with a combination of inotropic agents such as dopamine, dobutamine or amrinone and an intraaortic contrapulsion balloon.
Dopamine, which acts directly on beta1-adrenergic receptors in the myocardium and indirectly through the release of norepinephrine, has both inotropic and vasopressive effects. tachycardia and increased peripheral resistance after dopamine administration may accentuate myocardial ischemia. Dobutamine, a selective beta1-adrenergic agent, can improve myocardial contractility and increase heart rate without causing marked changes in heart rate or systemic vascular resistance.
Amrinone and milrinone are phosphodiesterase inhibitors, with both positive and vasodilating inotropic effects. They have longer half-life than dobutamine and can cause hypotension, so they are used when other therapeutic agents have proven ineffective. Because it does not act directly on adrenergic receptors, it may be useful in situations where the number of beta-adrenergic receptors is diminished. The combination of amrinone or milrinone with dopamine or dobutamine may be considered in patients who do not respond to monotherapy with one of these classes of medicines.
It's the turn of extracardiac obstructive shock. Cardiac tamponade is the prototype of extracardiac obstructive shock and can be recognized due to clinical manifestations (hypotension, paradoxical pulse, relaxed jugular veins) and characteristic echocardiographic aspects. Although the expansion of intravascular volume and sometimes the administration of vasopressor agents are useful timing measures, the only effective treatment being pericardial drainage by pericardiocentesis or surgical.
Pulmonary embolism is usually treated with anticoagulants, but when it is massive and causes insufficiency of the right ventricle and shock, thrombolytic treatment should be considered. In patients with contraindications for the latter, surgical pulmonary embolectomy is an alternative, if there is sufficient time for diagnosis, mobilization of the surgical team and the establishment of a cardiopulmonary bypass.
Treatment of septic shock has three main aspects. First the outbreak of infection should be identified and eliminated by surgical drainage or antibiotic treatment or both. Rapid establishment of appropriate antibiotic treatment has been associated with increased survival rate, but specific microorganisms that produce sepsis are not usually known when presenting the patient.
Thus, broad-spectrum antibiotics that are effective on most microorganisms should initially be administered, depending on the clinical condition of the patient and the type of antibiotic-resistant microorganisms in the hospital. Secondly, while the source of the infection is eradicated, an adequate infusion of organs and their function should be maintained through cardiovascular monitoring. Since antibiotic weather requires 48 hours or more to sterilize a septic outbreak, maintaining oxygen intake to tissues is essential for a further favorable development.
Because oxygen intake depends on haemoglobin concentration in the blood, oxygen saturation and cardiac flow, maintaining haemoglobin levels above 10 g/dL, oxygen saturation above 92% and adequate cardiac output are important therapeutic principles. Initially, cardiovascular therapy should optimize pre-pregnancy by volemic intake to maintain the blocking pressure in the pulmonary artery between 14 and 18 mmHg.
If serum albumin levels are low, increased intravascular oncotic pressure can be done by infusion of albumin concentrates. Because tissue hypoperfusion in sepsis occurs in part due to abnormal cardiac flow, it is sometimes recommended to increase cardiac output to a very high level above normal. However, it has not been demonstrated by controlled studies that the use of inotropic agents to achieve such flows would have a beneficial effect.
If only volemic expansion fails to maintain blood pressure and an adequate infusion of organs, treatment with vasopressor agents should be initiated. in patients with persistent hypotension, dopamine administration frequently increases blood pressure and maintains or increases blood flow to renal or splanhincirculation. Patients who remain hypotensive despite dopamine may be treated with norepinephrine, a stronger vasopressor.
Once hypotension has been corrected, it may be useful to increase the heart index with dobutamine to optimize oxygen intake to tissues. A third therapeutic objective is the interruption of the pathogenic sequence leading to septic shock. Several studies have shown that early administration of corticosteroids does not improve morbidity or mortality in septic shock. Newer therapies focused on inhibiting potentially toxic mediators such as endotoxin, TNF and IL-1. Studies with sepsis mediators, including anti-endotoxin antibodies, anti-TNF antibodies, IL-1 receptor antagonists and soluble TNF receptors, have not shown a significant reduction in the mortality of sepsis patients.
I'm done... Now, out of evil (out of shock), I'll give it in even worse. So, starting June 4, I'm going to tackle cardiovascular collapse, cardiac arrest and sudden cardiac death...
Let's hear it for good!
Dorin, Merticaru