Shock medical therapy: Difference between revisions
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==Medical Therapy== | ==Medical Therapy== | ||
===General Principles=== | ===General Principles=== | ||
Revision as of 18:23, 10 April 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Medical Therapy
General Principles
The management of shock can be difficult. There are several basic modalities.
Look for and treat the cause
Perhaps obvious but often overlooked. If patients are bleeding they need blood and the bleeding stopped. Treating hypotension due to variceal bleeding with inotropes is doomed. A Sengstaken tube or endoscopy with definitive treatment more promising.
In those with IHD an urgent angiogram with PCI may reperfuse hibernating myocardium and improve the situation. An intra-aortic balloon pump may augment coronary and cerebral perfusion from a failing myocardium as a bridge to a definite procedure. Drainage of pericardial fluid might restore haemodynamics quickly.
Restoring Physiology
In general, address the pathophysiology in this order:
Fluid resuscitation
Vital in most cases. In those with cardiac disease, excessive fluid may cause pulmonary edema and so should be used judiciously. A CVP line is then indicated or even better a measurement of LVEDP. However be aware that numbers can be wrong and treat the whole patient.
Vasoactive Drugs
(incl. vasopressors, inotropes and chronotropes)
Evidence and Clinical Condition Based Management
In the early stages, shock requires immediate intervention to preserve life. Therefore, the early recognition and treatment depends on the transfer to a hospital.
The management of shock requires immediate intervention, even before a diagnosis is made. Re-establishing perfusion to the organs is the primary goal through restoring and maintaining the blood circulating volume ensuring oxygenation and blood pressure are adequate, achieving and maintaining effective cardiac function, and preventing complications. Patients attending with the symptoms of shock will have, regardless of the type of shock, their airway managed and oxygen therapy initiated. In case of respiratory insufficiency (i.e. diminished levels of consciousness, hyperventilation due to acid-base disturbances or pneumonia) intubation and mechanical ventilation may be necessary. A paramedic may intubate in emergencies outside the hospital, whereas a patient with respiratory insufficiency in-hospital will be intubated usually by a physician.
The aim of these acts is to ensure survival during the transportation to the hospital; they do not cure the cause of the shock. Specific treatment depends on the cause.
A compromise must be found between:
- Raising the blood pressure to be able to transport "safely" (when the blood pressure is too low, any motion can lower the heart and brain perfusion, and thus cause death);
- Respecting the golden hour. If surgery is required, it should be performed within the first hour to maximize the patient's chance of survival.
This is the stay and play versus the load and go debate.
Hypovolemic shock
In hypovolemic shock, caused by bleeding, it is necessary to immediately control the bleeding and restore the victim's blood volume by giving infusions of balanced salt solutions. Blood transfusions are necessary for loss of large amounts of blood (e.g. greater than 20% of blood volume), but can be avoided in smaller and slower losses. Hypovolemia due to burns, diarrhea, vomiting, etc. is treated with infusions of electrolyte solutions that balance the nature of the fluid lost. Sodium is essential to keep the fluid infused in the extracellular and intravascular space whilst preventing water intoxication and brain swelling. Metabolic acidosis (mainly due to lactic acid) accumulates as a result of poor delivery of oxygen to the tissues, and mirrors the severity of the shock. It is best treated by rapidly restoring intravascular volume and perfusion as above. Inotropic and vasoconstrictive drugs should be avoided, as they may interfere in knowing blood volume has returned to normal.
Regardless of the cause, the restoration of the circulating volume is priority. As soon as the airway is maintained and oxygen administered the next step is to commence replacement of fluids via the intravenous route.
Opinion varies on the type of fluid used in shock. The most common are:
- Crystalloids - Such as sodium chloride (0.9%), or Hartmann's solution (Ringer's lactate). Dextrose solutions which contain free water are less effective at re-establishing circulating volume, and promote hyperglycemia.
- Colloids - For example, synthetic albumin (Flexbumin™), polysaccharides (Dextran™), polygeline (Haemaccel™), succinylated gelatin (Gelofusine™) and hetastarch (Hepsan™). Colloids are, in general, much more expensive than crystalloid solutions and have not conclusively been shown to be of any benefit in the initial treatment of shock.
- Combination - Some clinicians argue that individually, colloids and crystalloids can further exacerbate the problem and suggest the combination of crystalloid and colloid solutions.
- Blood - Essential in severe hemorrhagic shock, often pre-warmed and rapidly infused.
Vasoconstrictor agents have no role in the initial treatment of hemorrhagic shock, due to their relative inefficacy in the setting of acidosis, and due to the fact that the body, in the setting of hemorrhagic shock, is in an endogenously catecholaminergic state. Definitive care and control of the hemorrhage is absolutely necessary, and should not be delayed.
Cardiogenic shock
In cardiogenic shock, depending on the type of myocardal infarction, one can infuse fluids or in shock refractory to infusing fluids, inotropic agents. Inotropic agents, which enhance the heart's pumping capabilities, are used to improve the contractility and correct the hypotension. Should that not suffice, an intra-aortic balloon pump can be considered (which reduces the workload for the heart and improves perfusion of the coronary arteries) or a left ventricular assist device (which augments the pump-function of the heart.)
The main goals of the treatment of cardiogenic shock are the re-establishment of circulation to the myocardium, minimizing heart muscle damage and improving the heart's effectiveness as a pump. This is most often performed by percutaneous coronary intervention and insertion of a stent in the culprit coronary lesion or sometimes by cardiac bypass.
Although this is a protection reaction, the shock itself will induce problems; the circulatory system being less efficient, the body gets "exhausted" and finally, the blood circulation and the breathing slow down and finally stop (cardiac arrest). The main way to avoid this deadly consequence is to make the blood pressure rise again with:
- Fluid replacement with intravenous infusions
- Use of vasopressing drugs (e.g. to induce vasoconstriction)
- Use of anti-shock trousers that compress the legs and concentrate the blood in the vital organs (lungs, heart, brain).
- Use of blankets to keep the patient warm - metallic PET film emergency blankets are used to reflect the patient's body heat back to the patient.
Distributive shock
In distributive shock caused by sepsis the infection is treated with antibiotics and supportive care is given (i.e. inotropica, mechanical ventilation, renal function replacement). Anaphylaxis is treated with adrenaline to stimulate cardiac performance and corticosteroids to reduce the inflammatory response. In neurogenic shock because of vasodilation in the legs, one of the most suggested treatments is placing the patient in the Trendelenburg position, thereby elevating the legs and shunting blood back from the periphery to the body's core. However, since blood vessels are highly compliant, and expand as result of the increased volume locally, this technique does not work. More suitable would be the use of vasopressors.
Obstructive shock
In obstructive shock, the only therapy consists of removing the obstruction. Pneumothorax or haemothorax is treated by inserting a chest tube, pulmonary embolism requires thrombolysis (to reduce the size of the clot), or embolectomy (removal of the thrombus), tamponade is treated by draining fluid from the pericardial space through pericardiocentesis.
Endocrine shock
In endocrine shock the hormone disturbances are corrected. Hypothyroidism requires supplementation by means of levothyroxine, in hyperthyroidism the production of hormone by the thyroid is inhibited through thyreostatica, i.e. methimazole (Tapazole®) or PTU (propylthiouracil). Adrenal insufficiency is treated by supplementing corticosteroids.