Shock Management and Pharmacology PDF

Shock management and pharmacology Monitoring Perfusion Status and Obtaining Intravenous Access Patients with cardiac failure or renal failure may benefit from closer measurement of dynamic variables of fluid responsiveness that can be measured from an arterial line (e.g., stroke volume variation or...

Shock management and pharmacology Monitoring Perfusion Status and Obtaining Intravenous Access Patients with cardiac failure or renal failure may benefit from closer measurement of dynamic variables of fluid responsiveness that can be measured from an arterial line (e.g., stroke volume variation or stroke volume index) or a central venous line (central venous pressure \[CVP\]). A triple- lumen catheter allows for accurate measurement of the CVP, although the clinical utility of these measurements has been debated. However, a triple- lumen catheter can be useful in patients with poor peripheral access as it allows for safe infusion of vasopressors in hypotensive patients unresponsive to an initial fluid bolus, as well as simultaneous infusion of intravenous (IV) fluids and antibiotics when IV access is limited. In children, a 3- or 5- Fr bilumen catheter can be placed in the femoral vein with few complications. If unable to attain adequate peripheral or central venous access rapidly in patients with shock, intraosseous (IO) access should be established, because it is easy and can provide a temporary method of administering fluid resuscitation and medications to adults and children. In situations where both central venous access and IO access are unavailable, but the patient remains in shock, vasoactive medications should be given through a large- gauge (18g or larger) peripheral catheter at the level of the antecubital fossa or more proximally. If vasoactive medications are administered, additional peripheral IV catheters are required for infusion of crystalloid and other treatments. Many patients with renal disease or cancer often have indwelling catheters in place. In patients with empirical criteria for shock, this catheter should be used for IV access, unless satisfactory access has already been established at other anatomic sites. In EDs where the standard practice is not to use these ports at the request of other clinicians, a specific hospital policy and training session should be developed to make an exception in the case of shock. In general, the risk of the failure to administer fluids and vasoactive agents rapidly outweighs considerations about preservation of the line for future therapy. Quantitative Resuscitation Quantitative resuscitation, also called goal- directed therapy, goal- oriented resuscitation, or hemodynamic optimization, was first described in 1988 and refers to the practice of resuscitating patients to predefined physiologic endpoints (i.e., CVP, central venous oxygen saturations) indicating that systemic perfusion and vital organ function have been restored. In the ED, routine use of central venous monitoring for patients with septic shock does not improve outcomes compared to usual care. Therefore, a central line is typically placed when there is lack of adequate peripheral access or anticipated use of high- dose vasopressor agents. Over the last 3 decades, many studies have evaluated the efficacy of a quantitative approach to shock. In such an approach, patients are resuscitated early, within the first 6 hours, to achieve normalization of markers of volume status, perfusion, and adequate oxygen delivery. The first description of an ED- based quantitative resuscitation strategy targeted specific volume, perfusion, and oxygen delivery endpoints and was termed early goal- directed therapy (EGDT). As mentioned previously, external validation in three large multicenter trials did not demonstrate a mortality advantage for patients receiving EGDT compared to modern usual care of shock. Patients in these studies received 2 to 4 L early volume resuscitation and relatively prompt antibiotic administration, suggesting that early recognition and initiation of fluid and antibiotic therapy, in conjunction with close monitoring and thoughtful care, may be more important than the use of invasive measurements to attain the specific resuscitation goals suggested by earlier studies. Given these findings, the importance of specific quantitative targets for the resuscitation of ED septic shock is unproven. For complex patients for whom the physician is unclear as to the adequacy of oxygen delivery, it is recommended to use one of two readily available clinical methods, central venous oxygen saturation or lactate clearance. Central venous oxygen saturation drawn from the central circulation (via a triple lumen catheter) was a key component of EGDT and has been used as an indicator of the ratio of oxygen delivery to oxygen consumption. Central access is time- consuming and invasive, therefore, this approach is rarely taken in the ED anymore. Alternatively, lactate clearance refers to serial measurements of the venous or arterial lactate level. Lactate clearance has been shown to be equivalent to central venous oxygen saturation as an endpoint of early septic shock resuscitation, though it has not been systematically studied in other forms of shock. Lactate clearance measurements are easily obtained from peripheral venous blood and therefore represent a simpler and preferred endpoint of resuscitation. If the lactate concentration has not decreased by 10% to 20% 2 hours after resuscitation has begun, additional steps are undertaken to improve systemic perfusion. Pharmacology Volume Replacement Most patients with shock can be fully resuscitated with peripheral venous access established with at least two 18- gauge catheters. The goal in volume replacement is slightly elevated left ventricular end- diastolic volume, which is difficult to measure in the ED. Historically, CVP has been used to estimate right ventricular filling pressure and has been used in some quantitative resuscitation algorithms. CVP does not accurately reflect left ventricular end- diastolic volume, and poorly predicts the hemodynamic response to a fluid bolus. Thus, fluid resuscitation should not be based solely on CVP. A better approach involves the use of clinical response to fluid resuscitation, such as increases in urine output, BP, and decreasing lactate concentrations, either alone or in combination with CVP measurements. In patients for whom f luid resuscitation may be associated with higher risk of harm (e.g., severe systolic heart failure, dialysis- dependent renal failure), the use of dynamic variables of fluid responsiveness that can be measured from an arterial line (e.g., stroke volume variation, stroke volume index, passive straight leg raise) may be beneficial over empirical fluid boluses, but their use in the ED to guide therapy has not been sufficiently studied to recommend routinely. Crystalloids. Standard treatment for hemorrhagic shock historically consisted of rapidly infusing several liters of isotonic crystalloid in adults or three successive 20- mL/kg boluses in children. Some studies have endorsed the concept of delayed resuscitation or hypotensive resuscitation for hemorrhagic shock (see Chapter 32), although recent consensus statements have come out against this practice and favor early transfusion and minimization of hypotension.7 Recent data suggest balanced isotonic crystalloids (predominantly lactated Ringers) decrease the risk of acute kidney injury in admitted ED patients, while treatment of patients in shock with balanced fluids in the intensive care unit decreases the combination of renal failure and death.8 Therefore, balanced crystalloids are recommended once a patient is identified as having shock, if available, and in the absence of competing priorities (e.g., medication incompatibility with limited intravenous access). Initial volume replacement consists of the rapid infusion of 20 to 25 mL of isotonic crystalloid per kilogram, though these numbers represent conventional volumes utilized and clear evidence for the superiority of a specific volume of crystalloid bolus is lacking. More rapid initiation of fluid resuscitation may be associated with improved patient outcomes, reiterating the importance of early identification and treatment of shock. Colloids and hypertonic saline. Colloids offer the theoretical advantage of a high osmotic pressure, which should help maintain normal intravascular volume. Colloids, including albumin, have been used in patients with hemorrhage, but at a considerable increase in cost and without effect on morbidity or mortality. Initial resuscitation fluid treatment with hypertonic saline or hypertonic saline and dextran, compared with normal saline, does not decrease mortality in studies to date. In the setting of septic shock, initial fluid resuscitation should consist of serial boluses of IV isotonic crystalloid as long as the patient continues to demonstrate a positive hemodynamic response to fluid loading, and the majority of ED patients are initially volume responsive. Persistent hypotension, despite 30 mL/kg of IV fluid, indicates the need to add vasopressors to the resuscitation (see below). If patients require large volumes of crystalloid (\>4 L), we recommend adding 5- to 10- mL/kg boluses of a natural colloid (e.g., albumin), rather than additional isotonic crystalloid alone, until further volume fails to improve hemodynamics. We do not recommend the use of synthetic colloids, such as hydroxyethyl hetastarch, which are associated with a higher risk of renal failure. The infusion of hemoglobin- based blood substitutes as alternatives to packed red blood cells (PRBCs) for the resuscitation of hemorrhagic shock has been extensively studied and is associated with significant increased risk of death and myocardial infarction; we recommend against their use. Blood products. In the setting of hemorrhage or a critically low hemoglobin level (\