Intravenous Fluid Replacement

Almost all forms of circulatory shock make extensive intravenous fluid resuscitation is required. This corresponds to the situation in severe intravascular fluid loss, which can occur during diarrhea or heat stroke. The intravascular volume depletion is initially compensated in the acute situation by vasoconstriction. Within the next few hours, a passage of fluid from the extravascular space to the intravascular compartment is then carried into it. So the circulating volume can be maintained at the expense of total body water. However, these compensatory mechanisms are often topped by further fluid losses. Maintaining the fluid requirement is in water and sodium balance and mild forms of dehydration are discussed in dehydration and fluid therapy in children. Infusion solutions Selection of the appropriate volume replacement depends on the pathological mechanism that caused the deficit. Bleeding red blood cell loss reduces the O2-binding capacity. The reactions of the body, an increase of the cardiac output to maintain a reasonable range O2 (DO2) and an increased O2 extraction. These compensatory mechanisms provide for an increase in the safety margin to nine times the O2 -Ruhebedarfs. Thus, (z. B. crystalloid or colloid solutions) to restore intravascular volume of mild to moderate forms of blood loss are used O2-free infusion solutions. During a severe shock, but blood products are needed. An early administration of plasma and platelets probably minimizes the dilution caused by consumption coagulopathy that accompanies major bleeding. A ratio of 1 unit of plasma at each 1-2 units of blood was recommended, but the optimal ratio has not been confirmed. If the patient is stable, the Hb drops at a time <7 g / dl, a cardiac or cerebral Ekrankung missing, but care should be taken that the O2 transport capacity is restored. For this, the transfusion of blood components (or the future of blood substitutes) is required. Patients with active coronary or cerebral vascular disease or prolonged bleeding require the replacement of blood already at a Hb <10 g / dl. Crystalloid for the intravascular volume replacement are usually isotonic solutions (eg., 0.9% NaCl or Ringer's lactate solution [RL]). In these solutions, H2O leaves the vascular space freely, so that finally remain in the vascular system, only about 10% of the isotonic solution. In hypotonic liquids (eg. B. 0.45% NaCl-solution), however, this proportion is even lower. These solutions are therefore not suitable for volume replacement. Both 0.9% NaCl solution and Ringer's lactate are comparable in volume effect. Ringer's lactate but it preferred in hemorrhagic shock, because it helps reduce acidosis and does not lead to hyperchloraemia. In patients with fresh head injury 0.9% NaCl is selected. Hypertonic saline is not recommended for volume replacement, as evidence suggests that in terms of the result, no difference compared consists of isotonic fluids. Colloids (hydroxyethyl starch, albumin, dextran) are also very effective in volume replacement during a circulation. Colloids offer no great advantage over crystalloid solutions and albumin has been associated with a worse outcome in patients with traumatic brain injury. Both dextrans and hydroxyethyl starch act> 1500 ml anticoagulant at a dosage. In Germany, hydroxyethyl starch is favored. Blood is applied in the form of prepared erythrocyte concentrates (EC), after the cross match. In emergency situations, but also 1-2 EK blood type can be 0 Rh negative given. If more than 1-2 EK transfused (about in extensive trauma), the blood component should be warmed to 37 ° C. be a patient receives more than 6 EK, have usually also the replacement of clotting factors in the form of frozen plasma or cryoprecipitate and the administration of platelet concentrates contemplated (blood products). Blood substitutes are oxygen-carrying solutions that are based on a hemoglobin structure or perfluorocarbons. Hemoglobin-based solutions containing free hemoglobin which is enclosed in liposomes, or otherwise modified (change in the surface texture or in combination with other molecules), so as to limit the urinary excretion and toxicity. Because no antigen-carrying red blood cells are present, no cross-matching is required. The shelf life usually exceeds one year. Thus, the availability of these drugs is significantly more reliable than for products stored blood products. Perfluorocarbons are intravenously applicable Carbonfluorin emulsions that can transport large amounts of O2. For blood substitutes has been Allerding not yet been demonstrated until now that they increase survival, and some show significant side effects (eg. As hypotension). There are no blood substitutes are commercially Verfügung.Hypovolämie without bleeding isotonic crystalloid solutions are usually added for intravascular volume replacement during shock and hypovolemia. Colloids are essentially not used. Patients with dehydration and sufficient circulating volume of liquid typically have a deficit of free water. Here, hypotonic solutions (eg., 5% glucose, 0.45% NaCl-solution) was applied. Nature and scope of application Large (14-16 gauge) intravenous indwelling for peripheral venipuncture are the usual standard for most forms of volume replacement. In this way volumes of 1000 ml in 10-15 min or 1 EK in 20 min can be given. As pressure infusion can be 1 EK also infuse less than 5 minutes. In patients with severe blood loss (8.5 French z. B.) central venous catheter even greater volume of units can be applied per unit of time via a large-bore. Patients in shock require and tolerate largest volumes of liquid. In adults 1000 ml crystalloid are given (20 ml / kg in children), or hemorrhagic shock 5-10 ml / kg of colloids or erythrocyte concentrates. Thereafter, a reassessment of the clinical situation of the patient is carried out. Exceptions are patients with cardiogenic shock, which typically have no increased volume requirements. Patients with intravascular volume depletion without shock symptoms can be obtained by a controlled volume replacement of the order of 500 ml / h. In children, the fluid deficit should be more accurately calculated (Practical Example) and replacement occur over a period of 24 hours (of which the first half in the first 8 h). End point and monitoring The real goal in infusion therapy for shock is the optimization of tissue perfusion. However, this moment can not be determined accurately. Surrogate marker references to an adequate end-organ perfusion as well as the measurement of the preload are. An adequate end-organ perfusion can best be developed on the basis of urine output of more than 0.5 to 1 ml / kg / h. Heart rate, consciousness status and capillary refill can be influenced by the underlying disease and are therefore less reliable as a marker. Even in normal peripheral blood pressure values ??hypoperfusion of organs can be present. Due to the compensatory vasoconstriction of the mean arterial blood pressure (MAP) applies only as a rough standard gauge. An elevated arterial Blutlactatwert reflects the hypoperfusion. The values ??are, however, increased even hours after successful recompensation. The trend in base deficit may indicate whether the volume replacement is sufficient. Other methods of investigation such as the sublingual CO2 determination in tissue or the near-infrared spectroscopy can also be considered. Because central venous pressure, urine production makes no sufficient information about the current situation, measuring the preload in critical care patients may be a useful measure to control the volume replacement. The central venous pressure (CVP) is the average pressure in the superior vena cava, and thus outputs information about the right-ventricular end-diastolic pressure or preload (preload). The normal CVP is 2-7 mmHg (3-9 cm H2O). When unstable or traumatized patients with CVP <3 mmHg can be considered a lack of volume, and the administration of fluids is considered safe measure. However, if the CVP within the normal range, a volume deficit can not be excluded. Therefore, should, where 100 to 200 ml volume and the reaction can be checked out. A modest increase in CVP this infusion lot of back indicated generally in the direction of hypovolemia. An increase of more than 3-5 mm Hg after administration of 100 ml of solution should be interpreted as an indication of a limited cardiac reserve. A CVP> 12-15 mmHg makes hypovolemia as a cause of hypoperfusion very unlikely. Because of the risk of overhydration a fluid administration should be done very cautiously in these cases. Since the CVP may represent only a little reliable measure of volume status, or left ventricular function, should be provided no improvement in hemodynamics was achieved after initial fluid resuscitation, a pulmonary artery catheter (monitoring and study of ICU patients: monitoring with pulmonary artery catheter) for diagnosis and also for accurate design of fluid therapy should be considered. As part of a ventilation filling pressures must be interpreted with caution, especially if the positive end-expiratory pressure (PEEP) cm H2O has been selected more than values ??such as 10, or as part of an acute lung injury where the pleural pressures strong fluctuate. Measurements should be taken always at the end of expiration. The height of the transducer must be adjusted to atrial level (average thorax height). On careful calibration is to achten.Traumatisch caused hemorrhagic shock in patients with traumatic caused hemorrhagic shock a slightly different approach has to be chosen. Experimental and clinical studies have demonstrated that an internal bleeding may be exacerbated (in organ or vascular injury) by raising the MAP to normal or high-normal levels. Some physicians advocate a systolic blood pressure of 80-90 mmHg as a target point for the volume replacement in such patients to the surgical rehabilitation of the bleeding site, unless a higher pressure is needed to ensure an adequate cerebral perfusion. If the blood loss is under control, the hemoglobin can be used as a measure for further need for transfusion. In order to minimize the consumption of blood products, a target hemoglobin of 8-9 g / dl is recommended. In patients who tolerate a mild anemia difficulties (for coronary or cerebrovascular insufficiency), the hematocrit above 30% should be maintained. A higher value does not improve the outcome, however, may deteriorate the capillary perfusion by increasing blood viscosity. Complications Too rapid infusion with any liquid can cause pulmonary edema, ARDS or even a compartment syndrome (abdominal z. B. compartment syndrome, compartment syndrome in the extremities). The hemodilution by crystalloids in itself is not harmful, however, the hematocrit must be carefully controlled so as not to miss the threshold for the necessary implementation of a transfusion. The administration of packed red blood cells poses only a low risk of direct transmission of infection. Still in ICU patients, the rate of infections with hospital germs after transfusions appears slightly raised. However, this risk can be reduced by only blood is placed with a storage period of <12 days. In these preserves the erythrocytes are still deformable, so that the formation of cell rainfall is less likely in the microvessels. Other complications of massive transfusions are presented in transfusion complications.

Health Life Media Team

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