Shock is an acute circulatory disorder with tissue perfusion failure, leading to cellular anoxia.
It is a life-threatening emergency that requires rapid recognition and urgent symptomatic treatment.
The prognosis depends on the etiology and the speed of implementation of corrective measures.
Pathophysiology:
The insuffi acute circulatory impairment (shock) leading to defensive reactions responsible for:
– The increase in capillary permeability;
– Cellular anoxia with dysfunction of various organs.
The positive goals of these defensive reactions are:
– Maintain perfusion of vital organs such as the heart and brain, at the expense of the splanchnic area, muscles and skin;
– Promote hydrosaline retention in order to maintain effective circulating volume;
– Promote the release of energy substrates such as glucose and free fatty acids.
The disadvantage is that the increase in capillary permeability, or even destruction of the
capillary barrier, due to the peripheral hypoperfusion, causes interstitial edema and therefore a decrease in effective circulating volume.
CLINICAL DIAGNOSTICS:
Symptoms can be classified into 3 major groups that variously combine:
– Symptoms of peripheral hypoperfusion: decreased blood pressure, tachycardia, oliguria and cutaneous signs (skin pale, cold, clammy, optionally in combination with sloping mottling, weakness, prostration, anxiety, thirst);
– Tissue anoxia: brain damage is most evident clinically, with confusion, agitation and disturbance of consciousness (obtundation or coma);
. – Symptoms moving towards the etiology of shock etiology may be obvious febrile chills in sepsis, chest pain in cases of pulmonary embolism or infarction, externalized hemorrhage, allergic context etc. Otherwise, the examination of the patient and his entourage, history, treatments, context and recent events (drug taking, pain, infection, etc.) Can guide the diagnosis.
Physical examination for signs of bleeding, dehydration, heart failure, phlebitis, an asymmetry of peripheral pulses.
ETIOLOGY:
Recognizes 4 major types of shocks as the predominant initial physiological mechanism: cardiogenic (C), hypovolemic (H), obstructive (O), peripheral circulatory (C). These mechanisms may be associated differently.
Cardiogenic shock (C):
This is the worst prognosis. The underlying cause is a failure myocardial infarction often extended. Other causes of low cardiac output include advanced cardiomyopathy, acute infectious or inflammatory cardiomyosites, severe arrhythmia and drug poisoning (tricyclics, carbamates, nivaquine, digitalis, etc.). This is usually a shock “cold” whose diagnosis is helped by the electrocardiogram.
Hypovolemic shock (H):
Hypovolemic shock true (decrease in circulating blood volume) is generated by three main mechanisms:
– By blood loss:
– Internal acute hemorrhage (ruptured ectopic pregnancy, trauma liver / spleen femur) or iatrogenic (anticoagulants) or externalized (digestive origin, post-surgical, obstetric, post-traumatic). The hemoglobin assay can be normal in the acute phase,
– Hemolysis: transfusion accident, endotoxin shock, severe malaria, rarely challenge cit G6PD;
– By water loss: severe dehydration affects mainly infants and the elderly (diarrhea, profuse vomiting, heat stroke).However, dehydration may be related to the formation of a “third sector” (intestinal obstruction, peritonitis, ascites) or rarely due to abundant polyuria (diabetic ketoacidosis or hyperosmolar coma, hypercalcemia, etc.);
– By plasma leakage: extensive burns, lodges syndrome secondary to a crushing member, or angioedema, Clarkson syndrome (see edema), IL2 infusion.
Obstructive shock (O):
Obstructive shock is related to the presence of an obstacle in the cardiovascular circulation. The most common causes are:
– Pulmonary embolism, which should be considered routinely because of its high frequency. Thrombolytic therapy is indicated in the presence of hemodynamic shock;
– Pericardial tamponade: signs of right heart failure in the foreground.
The only treatment is pericardiocentesis which must be done urgently;
– Aortic dissection: diagnosis very difficult prehospital (asymmetry blood pressure, hypertensive thrust, transfixing chest pain).
Peripheral circulatory shock (or distributive) (C):
This is related hypovolemic shock, by redistribution of the vascular space: the blood volume is normal but there is a significant vasodilation.
This is usually an anaphylactic shock, and rarely a neurogenic shock (brainstem lesions).
Septic shock is characterized by fever or deep hypothermia, a clinical context favoring (immunosuppression) or an obvious infectious context. Its prognosis is poor with the possibility of very sharp aggravation.
This is a shock “hot” (hot ends and erythematous) but vasoconstriction is classic in the initial phase (myocardial failure or hypovolemia).
Treatment is based on antibiotics adapted to the presumed site of infection, which must be rapidly company after bacteriological samples if possible.
Prehospital diagnostic orientation:
Depending on the context and symptoms, prehospital diagnostic orientation can be established:
– Transfusion or drug intake: anaphylaxis, endotoxin transfusion accident;
– Trauma hemorrhagic shock or neurogenic;
– Chest pain: right heart failure: pulmonary embolism, tamponade, myocardial infarction complicated,
– Left heart failure myocardial infarction (MI), rupture of mitral rope
– Without heart failure: aortic dissection, aortic aneurysm;
– Abdominal or back pain:
– Apyrexia: acute pancreatitis, intestinal obstruction, aneurysm, abdominal aortic IDM, ulcer bleeding, ruptured ectopic pregnancy,
– Fever or hypothermia: peritonitis, pyelonephritis, diverticulitis, cholangitis;
– Context of abdominal surgery: gastrointestinal hemorrhage, obstetric or surgical site, drug allergies, intestinal obstruction, MI, pulmonary embolism (PE), peritonitis, abscesses or postoperative sepsis.
TO DO IN EMERGENCY:
First steps:
Position the patient: lying on his back, head elevated, if possible lower limbs elevated, undressed, covered with a sheet or an aluminum cover to avoid hypothermia.
In case of disturbance of consciousness or vomiting, placing the patient on the side (left side position of safety).
Measure vital signs (PA [blood pressure], FC [heart rate], temp [temperature], FR [respiratory rate], blood pressure, heart rate, temperature).
Insert an IV line in case of external bleeding; tamponade bleeding has priority compression or withers.
To warn the SAMU (center 15), meanwhile, stating: “shock in a XX years of patient, the doctor is on site and request an ambulance,” the phone number and address details.
Assessment of respiratory status:
We must seek cyanosis, rapid breathing, sweating or wrestling signs (supraclavicular or intercostal pulling, swinging thoracoabdominal).
If hemodynamic failure:
This symptom requires looking for anaphylaxis (history of atopy, erythema, pruritus, angioedema, bronchospasm).
Processing: injection of adrenaline at best intravenously.
SYMPTOMATIC TREATMENTS ON SITE:
oxygen:
It must be systematic for all the shock, the mask, or, if necessary, assisted ventilation sometimes requiring tracheal intubation.
Medications:
The recommended drugs face a shock are:
– D obutamine: sympathomimetic first line of cardiogenic shock, if the mean arterial pressure (MAP)> 70 mmHg;tonicardiaque predominant share;
– Dopamine: if PAM <60 mmHg; positive inotropic, peripheral vasoconstrictor proportional to dose;
– Adrenaline (α + β and +): high doses, alpha effect predominates; increased venous return;
– Isoprenaline (β1 and β2 + +): reserved to conduction disorders resistant to atropine, pending pacing.
The drugs against-indicated are: furosemide, nitro derivatives (reduction in cardiac output and vasodilators).
Vascular filling:
On site, it often comes down to positional methods pending the possibility of activating a sub-diaphragmatic compression and administration of plasma expanders. The elevation of the lower limbs is more effective in moderate hypovolemia. The Trendelenburg position is against-indicated in patients with head injury.
In case of filling of the products are available locally, should be favored: solutes synthetic colloids such [hydroxyethyl starch (HES), gelatin, dextrans] or natural colloids which enable equal expansion and prolonged infused volume.
Crystalloids (saline, Ringer lactateR), the effect is related to their osmolality, may also be used. In case of massive bleeding, you should change to modified gelatin solutions, despite an expansion of only 70% and very brief. But if one has only a iso glucose or NaCl iso, it must pass, if only to keep the IV line.
Always provide two-way first large-bore (16 or 14 G).
Two concepts are fundamental:
– Do not overfill a patient in hemorrhagic shock: the objective is to obtain a
MAP = DBP + 1/3 (PAS – PAD) of about 80 mmHg (MAP, DBP and SBP: arterial average systolic and diastolic pressures). Hemodilution and blood volume adjustment could reduce the spontaneous hemostasis by dilution of coagulation factors;
– Thoroughly complete a patient with septic shock.
ORIENTATION:
The transfer of the patient should be medicalized (UAS) and fast. The hospitable host structure should be contacted and warned by regulating the SAMU, so as not to delay the treatment. This structure must be able to provide treatments in connection with the etiological shock (vascular interventional surgical tray and in hemorrhagic shock).
The prognosis depends on the severity and duration of tissue hypoxia. When the shock has extended hours, the tissue anoxia causes irreversible damage, and evolution is often fatal, even if the cause is treated.
FILLING VASCULAR HOSPITAL:
The goal of fluid therapy is the normalization of blood volume.
Different fillers:
Effectiveness:
All volume replacement products are equally effective provided they are administered in doses that reflect their broadcasting space. It depends on the osmolality and oncotic their weight.
Isotonic crystalloid are as effective as the other solutions but require volumes 2-4 times greater than colloids.
Hypotonic crystalloid volume is equal to less effective than isotonic crystalloid and face the risk of hyponatremia.
Colloids, which have the advantage of requiring less volume, are more quickly effective than crystalloids. The HEA have high blood volume expansion capacity and prolonged efficacy.
Disadvantages:
Dextrans may be responsible for disorders of hemostasis, in contrast to albumin and gelatins.
Low molecular weight HEA interfere less with hemostasis that the high molecular weight HEA; however, the maximum recommended dose is 33 mL / kg / day on the first day and 20 to 33 mL / kg on the following days.
Colloids exhibit allergic risk (incidence of serious accidents <1 per 1,000 patients).
Gelatins and especially gelatins urea bridge (Hemacel®) have the highest allergy risk, albumin and lowest HEA. The responsibility of gelatine has never been proven to date in the occurrence of infections due to non conventional transmissible agents (prions). Despite this, the biological risk of these gelatins are of bovine origin can be considered invalid.
The responsibility of albumin in a pathogenic virus transmission known accident or unconventional transmissible agent (prions) has never been proven to date. However, albumin is a manmade derivative, the biological risk can be considered invalid.
Finally, the colloids are more expensive than crystalloid and albumin is the most expensive of colloids.
In practice, the following products should not be used:
– Fresh frozen plasma counterpart;
– Albumin, justified only in case of cons-indication to the use of synthetic colloids or if lower hypoprotidemia 35 g / L or hypoalbuminemia less than 20 g / L not on the dilution of the plasma protein by prior infusion of artificial colloids.
It is recommended that you use:
– Among the colloids: the hydroxyethyl starch (HES), which have lower side effects to those of gelatin and which are of plant origin;
– The isotonic crystalloid. Ringer lactate R is also recommended unless head trauma, overt hepatic failure, lactic acidosis and severe or in any situation of metabolic alcidose.
ANAPHYLACTIC SHOCK:
The first gesture includes administering 50 to 100 mcg of intravenous epinephrine, optionally repeatedly according to the hemodynamic response.
Fluid replacement is necessary when persistent hypotension despite repeated injections of adrenaline or when blood pressure settled secondarily after recovery of blood pressure. Crystalloid solutions are recommended because they do not increase histamine.
PREGNANT WOMAN:
Because of the serious consequences for the fetus of anaphylaxis or anaphylactoid breast induced by synthetic colloids, they are cons-indicated during pregnancy. It is recommended to use crystalloid associated with indirect sympatomimétique drug, ephedrine or phenylephrine.
For the curative treatment of hypovolemia, while the fetus is in utero, it is recommended to use crystalloid if hypovolemia is moderate, and albumin 4% in severe hypovolemia.
