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<< Symptomatic Hypotension: ED Stabilization And The Emerging Role Of Sonography

Controversies / Cutting Edge

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Controversies / Cutting Edge

Controversies / Cutting Edge

Hemodynamic Monitoring

The resuscitation literature points towards early aggressive management as being key to altering outcomes in patients with pathologic hypotension. This awareness has resulted in increased pressure to initiate therapy in the ED and provide close monitoring. Static hemodynamic reports do not accurately predict the patient's responsiveness to fluid administration or their actual clinical improvement.119 For example, while most patients with sepsis are discovered to be in a hyperdynamic state, this may be an early compensatory response.99 The patient with septic shock with a hyperdynamic LV on bedside ultrasound can have LV dysfunction several hours later, especially if the patient has pre-existing cardiac disease. RV dysfunction can also be present in as many as one-third of patients with sepsis. Continuous monitoring of RV function is extremely helpful for the assessment of cardiac and respiratory function and in response to treatments and interventions.

Measurement of cardiac filling pressures and pulmonary artery occlusion pressures are generally used in more intensive care settings and require highly invasive procedures (e.g., central venous pressure readings and right heart catheterization). With normal CVP readings between 6-12 cm H2O, low or high readings can help differentiate between hypovolemic states, cardiac failure, obstructive etiologies, and/or hypervolemic states.

Right heart catheterization (RHC) and pulmonary artery catheters (PAC) are more complicated and are used for occlusive pressure measurements. Further data can be obtained with this modality, especially when determining if pump failure primarily involves the left heart (e.g., decompensated CHF) or the right heart (e.g., right ventricular MI or other obstructive pathology). A meta-analysis of several randomized, controlled trials showed that early (prophylactic) use of PAC-directed therapy aimed at tissue perfusion resulted in a marked improvement in patient outcome.120 Other RCT studies in the meta-analysis, however, showed that there were no outcome improvements when PAC-directed therapy was used in ICU patients after organ failure and sepsis had set in. This was corroborated in other studies.121 In a prospective cohort study of 5735 critically ill patients, there was no patient group in which RHC demonstrated improved patient outcome. However, RHC was associated with increased mortality, length of stay, cost of care, and resource utilization.122 In a busy ED, the practicality of using invasive monitoring is severely limited by patient flow, inordinate amount of procedure time, and staffing issues; thus, it is not recommended.

Fortunately, some noninvasive techniques show promise; as they become more readily available, these techniques will allow the emergency physician to more easily deliver goal-oriented treatment. Bioimpedance monitors for cardiac output, transcutaneous oximetry, and capnometry for tissue perfusion in conjunction with pulse oximetry and blood pressure measurement have been shown to be accurate when compared to the same information typically obtained through a right heart catheter.8,123-125

Shoemaker et al studied the use of noninvasive methods in 151 severely injured patients using the continuous monitoring of certain cardiac pulmonary exchange and tissue perfusion parameters. Cardiac index and tissue oxygenation measured in this manner were significantly higher and well above "optimal" levels (as defined in the study) in survivors as compared to non-survivors.126 

Further support for the more expansive and earlier use of non-invasive hemodynamic monitoring was provided by a study of 680 critically ill patients. New bioimpedance methods for estimating cardiac output combined with arterial BP, pulse oximetry, and transcutaneous PO2 and PCO2 were equivalent to  thermodilution invasive data. The bioimpedance monitor was able to detect low flow states and poor tissue oxygenation early. Lower tissue oxygenation and higher tissue CO2 levels were significantly more prevalent in the non-survivors.124

Limitations of the thoracic bioimpedance instruments may include improper lead positioning, motion artifacts due to tremors, restless patient movements, and patient disease-related conditions like pulmonary edema, pleural effusions, valvular disease, and arrhythmias. With proper implementation of these instruments, however, better outcomes can be accomplished through earlier diagnosis and treatment of individuals at risk for developing hypotension and shock before late effects on the vital signs are seen. As this technology becomes more widespread, additional training in this monitoring will be necessary for emergency physicians, nurses, and other health providers in the ED.

Algorithmic Treatment Of Hypotension And Shock

With accurate monitoring of hemodynamic parameters and tissue perfusion, algorithms can be developed to directly address sub-clinical signs of poor tissue perfusion. The use of algorithms in managing hypotension is not a new concept. In 1983, a retrospective study of fluid resuscitation in 603 patients with hypotension was identified.12 This was a case series of patients with hypotension who were resuscitated with either a fluid administration algorithm or on the individual physician's preferences. A chart review showed that even with this specific clinical guideline, compliance with the algorithm was suboptimal. There were significant delays in the start of fluid challenges and many steps in the algorithm were not followed. There were 114 deaths (19% mortality) in the study group. Significant comorbidities were present in 265 (44%) of the hypotensive patients. Forty-four patients in this subgroup developed severe shock-related organ dysfunction. These patients had a higher mortality rate, more severe hypotension (lower mean arterial pressures), and more challenging and prolonged resuscitations. They also seemed to have noticeably more delayed starts to the resuscitation efforts after hypotension was recognized. The authors concluded that in circumstances where there were less deviations (or more compliance) from the fluid resuscitation guideline, the resuscitation efforts were shorter and there were fewer shock-related problems. Improved clinical outcomes included lowered mortality, shorter intensive care unit (ICU) length of stay (LOS), and less total time spent in the hospital. The patients with severe comorbid conditions were more likely to succumb to death and complications. In various other studies, better outcomes in terms of duration of hypotension, ICU and hospital stays, and overall mortality were also achieved with the use of algorithms.50,127-129

Recombinant Factor VIIa

There has been recent study of the use of rFactor VIIa to control bleeding during surgery. Of particular note to emergency physicians is its use in bleeding trauma patients. This medication is used to induce clotting specifically at the bleeding site and has particular use in blunt trauma and intracerebral hemorrhage, two entities that are not so rare in an ED setting. Current usage is recommended only in refractory bleeding and most case reports show its use as a "last-ditch" effort to control bleeding.130-133 Because of its procoagulant properties and the relative lack of completed randomized, controlled trials in its use, it can only be recommended with a Class III designation  until further information is received.134 There is no significant literature to support its use in medically bleeding patients and it may actually be contraindicated because of the typical multi-system disease in these patients.

Publication Information
Authors

Anthony J. Weekes; Ryan J. Zapata; Antonio Napolitano

Publication Date

November 1, 2007

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