University of New England DUNE : DigitalUNE Nurse Anesthesia Capstones School of Nurse Anesthesia Summer 2018 Noninvasive Hemodynamic Monitoring In Emergency Trauma Patients

Noninvasive hemodynamic monitoring has evolved steadily over the past few decades in response to healthcare providers' preference for less invasive monitoring methods for their patients. Invasive monitoring has its place in the critically ill patient population as witnessed in intensive care units throughout the country. Even in this environment, providers are opting less for the pulmonary artery catheter which has been the gold standard for invasive cardiac output monitoring in the past. Providers are now utilizing less invasive monitoring techniques which offer fewer potential complications to the patient while providing rapid access to critically important hemodynamic data. Examination of different noninvasive hemodynamic monitoring systems was completed in a literature review. The findings indicate that clinical accuracy is variable from device to device, however as technology has progressed there has been general improvement in this area. The appropriate clinical use for noninvasive hemodynamic monitoring is discussed based on evidence from the literature with a focus on the benefits and drawbacks that are associated with these systems as they specifically apply to the emergent trauma patient population. Introduction Noninvasive monitoring technology is uniquely poised to be of great benefit to the emergent trauma patient population. Knowing these patients’ hemodynamic status is critical to guiding management of these patients appropriately in the early stages of injury and resuscitation. Traditional monitoring of emergency trauma patients includes vital signs, urine output, and mental status. One of the problems with treating trauma patients solely by traditional measurements is that by the time there is a change noticed, the patient has decompensated towards a state of shock. As a patient’s hemodynamic status worsens, their response to treatment also worsens, thus making correction of the injury increasingly difficult. Non-invasive monitoring techniques provide early recognition of changes in NONINVASIVE HEMODYNAMIC MONITORING 3 hemodynamic status thus allowing for early treatment and improved responses to treatment. This preemptive treatment is critical for preventing hypoperfusion which can lead to irreversible organ damage, shock, and ultimately, death. Understanding the risks and benefits of noninvasive hemodynamic monitoring will help the nurse anesthetist to determine the appropriate application of these technologies towards improving the outcomes of their patients. This literature review examines the clinical research and application of various noninvasive hemodynamic techniques over the past 17 years. There have been multiple investigations of how noninvasive hemodynamic monitoring can be utilized in the hospital and emergency setting. The purpose of this literature review is to examine the evolution and application of specific noninvasive hemodynamic techniques as they apply to the trauma and emergency patient population. Literature Review Early noninvasive monitoring techniques were investigated by researcher Dr. William C. Shoemaker and his research colleagues. In 1999, they published a research article that examined the efficacy of early noninvasive hemodynamic monitoring after severe blunt trauma. They used a newly developed thoracic bioimpedance device which continually measured cardiac output and provided a continuous real-time display of data. The goal of the research was to determine if early identification and treatment of altered hemodynamic status via noninvasive monitoring in trauma patients would lead to more rapid and improved resuscitation (Velmahos, Wo, Demetriades, and Shoemaker, 1999). They noted that conventional monitoring which includes blood pressure, urine output, skin color, and mental status changes does not provide quantitative evaluation of cardiovascular function and these values may appear normal despite a significant hemodynamic deficit being present (Velmahos, Wo, Demetriades, and Shoemaker, 1999). The thoracic bioimpedance device was used in combination with a standard pulse oximeter, blood pressure cuff, a transcutaneous oxygen tension monitor, and a transcutaneous NONINVASIVE HEMODYNAMIC MONITORING 4 carbon dioxide tension monitor. The authors utilized thermodilution from pulmonary artery catheters to compare cardiac output values measured by the noninvasive monitor. They found a correlation coefficient which the researchers determined to be acceptable in the clinical setting. “The correlation coefficient for simultaneous pairs of samples of the two methods was r=0.91, r2=0.83. This is consistent with previous reports of critically ill patients predominantly in the ICU and was considered to be reasonably satisfactory from a clinical viewpoint” (Velmahos, Wo, Demetriades, and Shoemaker, 1999). The research results indicated that survivors and non-survivors had significantly different values as measured by the noninvasive monitoring which included cardiac index, oxygen saturation, and percutaneous oxygen and carbon dioxide tensions. They argued that these values could be used in the early resuscitative period to guide treatment as adequate resuscitation in the initial period after traumatic injury is critical and may determine patient outcome (Velmahos, Wo, Demetriades, and Shoemaker, 1999). The authors concluded that the bioimpedance device correlated adequately with values measured simultaneously by pulmonary artery catheter thermodilution, however there was no clinically agreed level of acceptance from any other source that could confirm this adequate correlation between the two measurements; this was considered a limitation of the study (Velmahos, Wo, Demetriades, and Shoemaker, 1999). Identifying early altered hemodynamic status in emergency trauma patients via easy to use noninvasive monitoring was an important and clinically useful research topic that other researchers would continue to build upon. Dr. Shoemaker was involved in another research project which utilized noninvasive monitoring as an early warning for the development of ARDS (acute respiratory distress syndrome) in trauma patients, published in 2000. The goal was to identify appropriate hemodynamic monitoring early after injury. Pulmonary artery catheterization, which is done in the critical care setting, provides metabolic oxygen delivery and consumption information, however this invasive monitoring is not readily available during the early resuscitation period in the emergency environment, whether that be the emergency NONINVASIVE HEMODYNAMIC MONITORING 5 department or operating room (Tatevossian et al., 2000). The researchers continuously monitored patients with transcutaneous oxygen and carbon dioxide tension measurements which were considered a substitute for invasive blood gas monitoring which only provides spot checks as opposed to continuous trending information. Transcutaneous oxygen and carbon dioxide tensions were used to measure skin oxygenation and perfusion; the authors note that the skin is the first organ to manifest vasoconstriction and uneven blood flow from sympathetic stress stimulation thus providing a general picture of tissue perfusion function (Tatevossian et al., 2000). A thoracic electrical bioimpedance device was also used to monitor cardiac output noninvasively. The results of the study found certain trends that provided useful information; patients who did not develop ARDS had higher cardiac index and tissue perfusion levels than those who developed ARDS. The survivors of ARDS had higher cardiac output and tissue perfusion values than those who died after ARDS. This helped the authors to identify that monitoring and optimal treatment in the late stages after organ failure was ineffective due to severe oxygen debt already accumulated (Tatevossian et al., 2000). The authors found that early recognition of changes in tissue perfusion and cardiac output could guide pre-emptive treatment and decrease the risk that the patient develops ARDS with the application of these noninvasive monitoring techniques. Shoemaker et al. (2006) published another article in the journal Military Medicine which examined how noninvasive monitoring for combat casualties could optimize patient outcomes. Shoemaker focused again on the importance of early monitoring and resuscitation in patients who had suffered traumatic injuries. Recognition of altered hemodynamic status is crucial in this initial period after traumatic injury. Delayed treatment has been shown to lead towards shock, organ failure, and death. The authors noted that goal directed resuscitation therapy with invasive pulmonary artery catheterization did not improve outcomes as this monitoring was usually started greater than 24 hours after hospital admission or after onset of organ failure; however early preoperative hemodynamic optimization showed significant improvement in patient outcomes (in the setting of peripheral vascular NONINVASIVE HEMODYNAMIC MONITORING 6 surgery, trauma, cardiogenic shock, and sepsis) (Shoemaker et al., 2006). The researchers again used a thoracic bioimpedance device which was applied to patients shortly after arrival to the emergency department. They cited previous studies which documented satisfactory correlation between these noninvasive monitoring devices and the gold standard invasive pulmonary artery catheter thermodilution measurement of cardiac output. The authors did note the limitations of the bioimpedance device which is attached via thoracic electrode pads; these include faulty electrode placement, motion artifacts, patient restlessness, shivering, pulmonary edema, pleural effusion, valvular heart disease, dysrhythmias, and electrical leak from instruments using the same circuit (Shoemaker et al., 2006). The study included 851 patients who survived and 149 patients who died during hospitalization with the mortality rate at 14.9%. The authors generalized these large city trauma patients to s