Evaluation of a noninvasive continuous cardiac output monitoring system based on thoracic bioreactance

Efficacy of Goal-Directed Therapy Using Bioreactance Cardiac Output Monitoring after Valvular Heart Surgery

PURPOSE

We compared the efficacy of postoperative hemodynamic goal-directed therapy (GDT) using a pulmonary artery catheter (PAC) and bioreactance-based noninvasive cardiac output monitoring (NICOM) in patients with atrial fibrillation undergoing valvular heart surgery.

MATERIALS AND METHODS

Fifty eight patients were randomized into two groups of GDT with common goals to maintain a mean arterial pressure of 60-80 mm Hg and cardiac index ≥2 L/min/m²: the PAC group (n=29), based on pulmonary capillary wedge pressure, and the NICOM group (n=29), based on changes in stroke volume index after passive leg raising. The primary efficacy variable was length of hospital stay. Secondary efficacy variables included resource utilization including vasopressor and inotropic requirement, fluid balance, and major morbidity endpoints.

RESULTS

Patient characteristics and operative data were similar between the groups, except that significantly more patients underwent double valve replacement in the NICOM group. The lengths of hospital stay were not different between the two groups (12.2±4.8 days vs. 10.8±4.0 days, p=0.239). Numbers of patients requiring epinephrine (5 vs. 0, p=0.019) and ventilator care >24 h (6 vs. 1, p=0.044) were significantly higher in the PAC group. The PAC group also required significantly larger amounts of colloid (1652±519 mL vs. 11430±463 mL, p=0.004).

CONCLUSION

NICOM-based postoperative hemodynamic GDT showed promising results in patients with atrial fibrillation undergoing valvular heart surgery in terms of resource utilization.

Central and Peripheral Hemodynamic Adaptations During Cardiopulmonary Exercise Test in Heart Failure Patients With Exercise Periodic Breathing

Some heart failure (HF) patients develop ventilatory oscillation which is composed of exercise periodic breathing (EPB) and sleep apnea. The ventilatory oscillation is associated with exercise intolerance. This study employed an integrated monitoring system to elucidate the way of central and peripheral hemodynamic adaption responding to exercise. This study recruited 157 HF patients to perform exercise testing using a bicycle ergometer. A noninvasive bio-reactance device was adopted to measure cardiac hemodynamics, whereas a near-infrared spectroscopy (NIRS) was used to assess perfusion and O2 extraction in the frontal cerebral lobe (FC) and vastus lateralis muscle (VL) during exercise respectively. Furthermore, quality of life (QoL) was measured with the Short Form-36 (SF-36) and the Minnesota Living with Heart Failure questionnaires (MLHFQ). The patients were divided into an EPB group (n = 65) and a non-EPB group (n = 92) according to their ventilation patterns during testing. Compared to their non-EPB counterparts, the patients with EPB exhibited 1) impaired aerobic capacity with a smaller peak oxygen consumption (VO2peak) and oxygen uptake efficiency slopes; 2) impaired circulatory and ventilatory efficiency with relatively high cardiac output and ventilation per unit workload; 3) impaired ventilatory/hemodynamic adaptation in response to exercise with elevated deoxyhemoglobin levels in the FC region; and 4) impaired QoL with lower physical component scores on the SF-36 and higher scores on the MLHFQ. In conclusion, EPB may reduce circulatory-ventilatory-hemodynamic efficiency during exercise, thereby impairing functional capacity in patients with HF.

Bioreactance Is Not Interchangeable with Thermodilution for Measuring Cardiac Output during Adult Liver Transplantation

Background

Thermodilution technique using a pulmonary artery catheter is widely used for the assessment of cardiac output (CO) in patients undergoing liver transplantation. However, the unclearness of the risk-benefit ratio of this method has led to an interest in less invasive modalities. Thus, we evaluated whether noninvasive bioreactance CO monitoring is interchangeable with thermodilution technique.

Methods

Nineteen recipients undergoing adult-to-adult living donor liver transplantation were enrolled in this prospective observational study. COs were recorded automatically by the two devices and compared simultaneously at 3-minute intervals. The Bland–Altman plot was used to evaluate the agreement between bioreactance and thermodilution. Clinically acceptable agreement was defined as a percentage error of limits of agreement <30%. The four quadrant plot was used to evaluate concordance between bioreactance and thermodilution. Clinically acceptable concordance was defined as a concordance rate >92%.

Results

A total of 2640 datasets were collected. The mean CO difference between the two techniques was 0.9 l/min, and the 95% limits of agreement were -3.5 l/min and 5.4 l/min with a percentage error of 53.9%. The percentage errors in the dissection, anhepatic, and reperfusion phase were 50.6%, 56.1%, and 53.5%, respectively. The concordance rate between the two techniques was 54.8%.

Conclusion

Bioreactance and thermodilution failed to show acceptable interchangeability in terms of both estimating CO and tracking CO changes in patients undergoing liver transplantation. Thus, the use of bioreactance as an alternative CO monitoring to thermodilution, in spite of its noninvasiveness, would be hard to recommend in these surgical patients.

Prediction of fluid responsiveness using a non-invasive cardiac output monitor in children undergoing cardiac surgery

BACKGROUND

This study evaluated the ability of a non-invasive cardiac output monitoring device (NICOM) to predict fluid responsiveness in paediatric patients undergoing cardiac surgery.

METHODS

Children aged <5 yr undergoing congenital heart surgery were included. Once the sternum had been closed after repair of the congenital heart defect, 10 ml kg(-1) colloid solution was administered for volume expansion. Transoesophageal echocardiography (TOE) was performed to measure stroke volume (SV) and respiratory variation in aortic blood flow peak velocity (ΔV(peak)) before and after volume expansion. Haemodynamic and NICOM variables, including SV(NICOM), stroke volume variance (SVV(NICOM)), cardiac index (CI(NICOM)), and percentage change in thoracic fluid content compared with baseline (TFCd0%), were also recorded. Patients in whom the stroke volume index (SVI), measured using TOE, increased by >15% were defined as fluid responders.

RESULTS

Twenty-nine patients were included (13 responders and 16 non-responders). Before volume expansion, only ΔV(peak) differed between groups (P=0.036). The SVV(NICOM), HR, and central venous pressure did not predict fluid responsiveness, but ΔV(peak) did. The CI(NICOM) was not correlated with CI(TOE) (r=0.107, P=0.43). Using Bland-Altman analysis, the mean bias between CI(TOE) and CI(NICOM) was 0.89 litre min(-1) m(-2), with a precision of 1.14 litre min(-1) m(-2). Trending ability of NICOM for SVI and CI was poor when TOE was a reference method.

CONCLUSIONS

The SVV(NICOM) did not predict fluid responsiveness in paediatric patients during cardiac surgery. In addition, there was no correlation between CI(TOE) and CI(NICOM). Fluid management guided by NICOM should be performed carefully.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01996956.

Non-invasive hemodynamic monitoring in trauma patients

BACKGROUND

The assessment of hemodynamic status is a crucial task in the initial evaluation of trauma patients. However, blood pressure and heart rate are often misleading, as multiple variables may impact these conventional parameters. More reliable methods such as pulmonary artery thermodilution for cardiac output measuring would be necessary, but its applicability in the Emergency Department is questionable due to their invasive nature. Non-invasive cardiac output monitoring devices may be a feasible alternative.

METHODS

A systematic literature review was conducted. Only studies that explicitly investigated non-invasive hemodynamic monitoring devices in trauma patients were considered.

RESULTS

A total of 7 studies were identified as suitable and were included into this review. These studies evaluated in a total of 1,197 trauma patients the accuracy of non-invasive hemodynamic monitoring devices by comparing measurements to pulmonary artery thermodilution, which is the gold standard for cardiac output measuring. The correlation coefficients r between the two methods ranged from 0.79 to 0.92. Bias and precision analysis ranged from -0.02 +/- 0.78 l/min/m(2) to -0.14 +/- 0.73 l/min/m(2). Additionally, data on practicality, limitations and clinical impact of the devices were collected.

CONCLUSION

The accuracy of non-invasive cardiac output monitoring devices in trauma patients is broadly satisfactory. As the devices can be applied very early in the shock room or even preclinically, hemodynamic shock may be recognized much earlier and therapeutic interventions could be applied more rapidly and more adequately. The devices can be used in the daily routine of a busy ED, as they are non-invasive and easy to master.

Noninvasive cardiac output measurement using bioreactance in postoperative pediatric patients

BACKGROUND

Thoracic bioreactance is a noninvasive and continuous method of cardiac output (CO) measurement that is being developed in adult patients. Very little information is available on thoracic bioreactance use in children.

OBJECTIVE

The aim of the study was to evaluate the ability of a bioreactance device (NICOM(®) ; Cheetah Medical, Tel Aviv, Israel) to estimate CO and to track changes in CO induced by volume expansion (VE) in children.

METHODS

Cardiac output values obtained using the NICOM(®) device (CONICOM ) and measured by trans-thoracic echocardiography (COTTE ) were compared in pediatric neurosurgical patients during the postoperative period.

RESULTS

Seventy-three pairs of measurements of CO obtained in 30 children were available for analysis. The bias (lower and upper limits of agreement) between CONICOM and COTTE was -0.11 (-1.4 to 1.2) l·min(-1). The percentage error (PE) was 55%. The precision of the NICOM(®) device was 45%. A significant correlation was observed between the CO values obtained using the two methods (r = 0.89, <0.001). The concordance percentage between changes in COTTE and CON icom induced by VE was 84% following exclusion of patients with changes in CO <15% (n = 5).

CONCLUSIONS

The PE observed is too large, and the limits of agreement too wide, to enable us to comment on the equivalence of the two techniques of CO measurements. However, the NICOM(®) device performs well in tracking changes in CO following VE.

Noninvasive cardiac output monitoring using bioreactance-based technique in pediatric patients with or without ventricular septal defect during anesthesia: in comparison with echocardiography

BACKGROUND

We evaluated the use of bioreactance-based noninvasive cardiac output (CO) monitoring technique (NICOM(™), CO(NICOM)) in pediatric patients with or without ventricular septal defect (VSD) during anesthesia induction to determine its agreement with the measurements assessed by echocardiography (echo, CO(ECHO)).

METHODS

Twenty-eight pediatric patients with normal heart anatomy (group NHA) and 32 with isolated ventricular septal defects (group VSD) were included in this study. The cardiac output was measured simultaneously in minute-by-minute using NICOM and echo (Simpson's rule) during anesthesia induction and intubation. Linear regression and revised Bland-Altman analyses were performed to evaluate the agreement by comparing the paired CO results. The mean percent error ((CO(ECHO)-CO(NICOM))/CO(ECHO) × 100%) was used to assess the impact of congenital heart disease on the agreement.

RESULTS

The measurements of CO by NICOM and echo techniques were highly correlated in group NHA (γ = 0.96, P < 0.005) and VSD (γ = 0.84, P < 0.005). The mean bias (CO(ECHO) - CO(NICOM)) between the two methods was 0.03 and 0.31 l·min(-1) with the limits of agreement (LOA) -0.29 to +0.35 l·min(-1) and -0.44 to +1.05 l·min(-1), which include 96.9% (31/32) and 89.3% (25/28) of all patients' different data in group NHA and VSD, respectively. The median percent errors were significantly lower at all time points in group NHA than those in group VSD (all P < 0.05).

CONCLUSION

In children without heart defects, the CO measured by NICOM shows a good agreement with the echo during anesthesia induction. The NICOM technique underestimates echo although a strong correlation exists between two methods in children with ventricular septal defect.

Comparison of monitoring performance of bioreactance versus esophageal Doppler in pediatric patients

Background and Aims:

Cardiac output (CO) monitoring and goal-directed therapy during major abdominal surgery is currently used to decrease postoperative complications. However, few monitors are currently available for pediatric patients. Nicom^® is a noninvasive CO monitoring technique based on the bioreactance principle (analysis of frequency variations of a delivered oscillating current traversing the thoracic cavity). Nicom^® may be a useful monitor for pediatric patients.

Subjects and Methods:

Pediatric patients undergoing major abdominal surgery under general anesthesia with cardiac monitoring by transesophageal Doppler (TED) were included. Continuously recorded hemodynamic variables obtained from both bioreactance and TED were compared. Data were analyzed using the Bland–Altman method.

Results:

A total of 113 pairs of cardiac index (CI) measurments from 16 patients were analyzed. Mean age was 59 months (95% CI: 42-75) and mean weight was 17 kg (95% CI: 15–20). In the overall population, Bland–Altman analysis revealed a bias of 0.4 L/min/m², precision of 1.55 L/min/m², limits of agreement of −1.1 to 1.9 L/min/m² and a percentage error of 47%. For children weighing >15 kg, results were: Bias 0.51 L/min/m², precision 1.17 L/min/m², limits of agreement −0.64 to 1.66 L/min/m² and percentage error 34%.

Conclusion:

Simultaneous CI estimations made by bioreactance and TED showed high percentage of errors that is not clinically acceptable. Bioreactance cannot be considered suitable for monitoring pediatric patients.

Cardiovascular parameters in a mixed-sex swine study of severe decompression sickness treated with the emulsified perfluorocarbon Oxycyte

Intravenous perfluorocarbons (PFC) have reduced the effects of decompression sickness (DCS) and improved mortality rates in animal models. However, concerns for the physiological effects of DCS combined with PFC therapy have not been examined in a balanced mixed-sex population. Thirty-two (16 male, 16 female) instrumented and sedated juvenile Yorkshire swine were exposed to 200 feet of seawater (fsw) for 31 min of hyperbaric air. Pulmonary artery pressure (PAP), cardiac output (CO), and systemic arterial pressure (SAP) were monitored before (control) and after exposure. Animals were randomized to treatment with Oxycyte (5 ml/kg; Oxygen Biotherapeutics, Inc., Morrisville, NC) vs. saline (control) with 100% oxygen administered upon DCS onset; animals were observed for 90 min. Parameters recorded and analyzed included PAP, CO, and SAP. In all animals PAP began to rise prior to cutis marmorata (CM) onset, the first sign of clinical DCS, generally peaking after CM onset. Female swine, compared with castrated males, had a more rapid onset of CM (7.30 vs. 11.46 min postsurfacing) and earlier onset to maximal PAP (6.41 vs. 9.69 min post-CM onset). Oxycyte therapy was associated with a sustained PAP elevation above controls in both sexes (33.41 vs. 25.78 mmHg). Significant pattern differences in PAP, CO, and SAP were noted between sexes and between therapeutic groups. There were no statistically significant differences in survival or paralysis between the PFC and control groups during the 48-h observation period. In conclusion, Oxycyte therapy for DCS is associated with a prolonged PAP increase in swine. These species and sex differences warrant further exploration.

The passive leg raise test to predict fluid responsiveness in children--preliminary observations

OBJECTIVE

To assess whether the passive leg raising (PLR) test can predict fluid responsiveness in pediatric patients.

METHODS

This was a prospective observational study in a tertiary care pediatric center. Hemodynamic parameters including heart rate, stroke volume and cardiac output were assessed at baseline, after passive leg raising (PLR), at second baseline, and after volume loading (10 mL/kg normal saline in 10 min). Cutoff values of 7.5 and 10 % increase in cardiac index (CI) with passive leg raising were explored as predictors of volume loading response.

RESULTS

Overall, the changes in CI with passive leg raising varied widely and was a poor predictor of response to volume loading in children under 5 years of age. Of 40 patients, 23 had greater than 10 % increase in CI with PLR which predicted fluid responsiveness with a sensitivity of 94 % (95 % confidence interval 71,100) and specificity of 26 % (95 % confidence interval 10,48). Sensitivity was higher (100 % vs. 91 %) and specificity similar (27 % vs. 25 %) in predicting CI for those over 5 as compared to under 5 y, respectively. In patients over 5 y, simple linear regression revealed a positive correlation (R(2) = 21) while R(2) values were much lower (0-0.07) for those under 5 y.

CONCLUSIONS

Cardiac index changes after PLR varies widely in children and may be a poor predictor to volume loading in children under 5-y-old. However, in those over 5 y, PLR may be helpful in predicting fluid responsiveness in pediatric patients.

Inter-device differences in monitoring for goal-directed fluid therapy

PURPOSE

Goal-directed fluid therapy is an integral component of many Enhanced Recovery After Surgery (ERAS) protocols currently in use. The perioperative clinician is faced with a myriad of devices promising to deliver relevant physiologic data to better guide fluid therapy. The goal of this review is to provide concise information to enable the clinician to make an informed decision when choosing a device to guide goal-directed fluid therapy.

PRINCIPAL FINDINGS

The focus of many devices used for advanced hemodynamic monitoring is on providing measurements of cardiac output, while other, more recent, devices include estimates of fluid responsiveness based on dynamic indices that better predict an individual's response to a fluid bolus. Currently available technologies include the pulmonary artery catheter, esophageal Doppler, arterial waveform analysis, photoplethysmography, venous oxygen saturation, as well as bioimpedance and bioreactance. The underlying mechanistic principles for each device are presented as well as their performance in clinical trials relevant for goal-directed therapy in ERAS.

CONCLUSIONS

The ERAS protocols typically involve a multipronged regimen to facilitate early recovery after surgery. Optimizing perioperative fluid therapy is a key component of these efforts. While no technology is without limitations, the majority of the currently available literature suggests esophageal Doppler and arterial waveform analysis to be the most desirable choices to guide fluid administration. Their performance is dependent, in part, on the interpretation of dynamic changes resulting from intrathoracic pressure fluctuations encountered during mechanical ventilation. Evolving practice patterns, such as low tidal volume ventilation as well as the necessity to guide fluid therapy in spontaneously breathing patients, will require further investigation.

Correlation of cardiac output measured by non-invasive continuous cardiac output monitoring (NICOM) and thermodilution in patients undergoing off-pump coronary artery bypass surgery

Purpose

This observational study was designed to evaluate the clinical value of cardiac output (CO) obtained via bioreactance (NICOM™) as compared with values of CO obtained via thermodilution (using pulmonary artery catheter, Vigilance™) and the thoracic bioimpedance (BioZ.com™), in patients undergoing off-pump coronary artery bypass surgery.

Methods

Fifty American Society of Anesthesiologists physical status I–III patients, aged 38–81 years, scheduled for off-pump coronary artery bypass surgery were enrolled in this study. CO data (NCO, BCO, PCO) were recorded during the operative period at ten time points after stable hemodynamic conditions were achieved.

Results

The equation of the relationship between the PCO and NCO is PCO = 0.945 × NCO + 0.328 (r = 0.77), and that of PCO and BCO is PCO = 0.965 × BCO + 0.729 (r = 0.63). Furthermore, no statistical difference was found between PCO versus NCO (mean (SD): 4.4 (1.1) versus 4.4 (0.9), p = 0.431). A significant correlation was found between PCO and NCO (r = 0.77, p < 0.001). Correlation was also found between PCO and BCO (r = 0.63, p < 0.001).

Conclusions

The NICOM device is a safe, convenient, and reliable device for measuring continuous non-invasive cardiac output and cardiac index, and the trends of change in CO during the surgery are similar between NICOM and PAC.

Stroke volume variation and indexed stroke volume measured using bioreactance predict fluid responsiveness in postoperative children

BACKGROUND

Postoperative fluid management can be challenging in children after haemorrhagic surgery. The goal of this study was to assess the ability of dynamic cardiovascular variables measured using bioreactance (NICOM®, Cheetah Medical, Tel Aviv, Israel) to predict fluid responsiveness in postoperative children.

METHODS

Children sedated and mechanically ventilated, who require volume expansion (VE) during the immediate postoperative period, were included. Indexed stroke volume (SVi), cardiac index, and stroke volume variation (SVV) were measured using the NICOM® device. Responders (Rs) to VE were patients showing an increase in SV measured using transthoracic echocardiography of at least 15% after VE. Data are median [95% confidence interval (CI)].

RESULTS

Thirty-one patients were included, but one patient was excluded because of the lack of calibration of the NICOM® device. Before VE, SVi [33 (95% CI 31-36) vs 24 (95% CI 21-28) ml m(-2); P=0.006] and SVV [8 (95% CI 4-11) vs 13 (95% CI 11-15)%; P=0.004] were significantly different between non-responders and Rs. The areas under the receiver operating characteristic curves of SVi and SVV for predicting fluid responsiveness were 0.88 (95% CI 0.71-0.97) and 0.81 (95% CI 0.66-0.96), for a cut-off value of 29 ml m(-2) (grey zone 27-29 ml m(-2)) and 10% (grey zone 9-15%), respectively.

CONCLUSIONS

The results of this study show that SVi and SVV non-invasively measured by bioreactance are predictive of fluid responsiveness in sedated and mechanically ventilated children after surgery.

Assessing volume status

Shock is a physiologic state associated with high morbidity and mortality rates. The clinician has several tools available to evaluate volume status. Each modality has its benefits and limitations but, to date, no one test can indicate with 100% accuracy which patients will be truly volume responsive. Although the search for the Holy Grail of a perfect intravascular monitor continues, we must remember the importance of early, aggressive, and goal-directed interventions for patients in shock. Finally, there is no substitute for the most important intervention-the frequent presence of the physician at the patient's bedside.

The feasibility and applications of non-invasive cardiac output monitoring, thromboelastography and transit-time flow measurement in living-related renal transplantation surgery: results of a prospective pilot observational study

Introduction

Delayed graft function (DGF) remains a significant and detrimental postoperative phenomenon following living-related renal allograft transplantation, with a published incidence of up to 15%. Early therapeutic vasodilatory interventions have been shown to improve DGF, and modifications to immunosuppressive regimens may subsequently lessen its impact. This pilot study assesses the potential applicability of perioperative non-invasive cardiac output monitoring (NICOM), transit-time flow monitoring (TTFM) of the transplant renal artery and pre-/perioperative thromboelastography (TEG) in the early prediction of DGF and perioperative complications.

Methods

Ten consecutive living-related renal allograft recipients were studied. Non-invasive cardiac output monitoring commenced immediately following induction of anaesthesia and was maintained throughout the perioperative period. Doppler-based TTFM was performed during natural haemostatic pauses in the transplant surgery: immediately following graft reperfusion and following ureteric implantation. Central venous blood sampling for TEG was performed following induction of anaesthesia and during abdominal closure.

Results

A single incidence of DGF was seen within the studied cohort and one intra-operative (thrombotic) complication noted. NICOM confirmed a predictable trend of increased cardiac index (CI) following allograft reperfusion (mean CI - clamped: 3.17 ± 0.29 L/min/m², post-reperfusion: 3.50 ± 0.35 L/min/m²; P < 0.05) mediated by a significant reduction in total peripheral resistance. Reduced TTFM at the point of allograft reperfusion (227 ml/min c.f. mean; 411 ml/min (95% CI: 358 to 465)) was identified in a subject who experienced intra-operative transplant renal artery thrombosis. TEG data exhibited significant reductions in clot lysis (LY30 (%): pre-op: 1.0 (0.29 to 1.71), post reperfusion 0.33 (0.15 to 0.80); P = 0.02) and a trend towards increased clot initiation following allograft reperfusion.

Conclusions

Reduced renal arterial blood flow (falling without the 95% CI of the mean), was able to accurately predict anastomotic complications within this pilot study. TEG data suggest the emergence of a prothrombotic state, of uncertain clinical significance, following allograft reperfusion. Abrogation of characteristic haemodynamic trends, as determined by NICOM, following allograft reperfusion may permit prediction of individuals at risk of DGF. The findings of this pilot study mandate a larger definitive trial to determine the clinical applications and predictive value of these technologies.

Evaluating the adequacy of fluid resuscitation in patients with septic shock: controversies and future directions

Fluid resuscitation is a cornerstone in the treatment of severe sepsis and septic shock. However, there is little evidence to guide clinicians in its administration. Current guidelines recommend targeting fluid therapy based on measurements of cardiac filling pressures, such as central venous pressure. Static pressures are poor predictors of a patient's response to fluid. Such response can be better predicted by measuring changes in hemodynamic parameters caused by positive pressure ventilation or maneuvers designed to simulate increased preload. These changes can be measured by analysis of arterial waveforms, echocardiography or Doppler, or with emerging noninvasive technologies. This article reviews the current role of fluid replacement strategies and the use of monitoring systems in the overall resuscitation of patients with severe sepsis and septic shock.

Comparison of the hemodynamic effects of nitroprusside and remifentanil for controlled hypotension during endoscopic sinus surgery

PURPOSE

Controlled hypotension (CH) is a well-established technique to decrease blood loss and improve surgical visibility. Although nitroprusside and remifentanil have been safely and effectively used for this purpose, the hemodynamic changes that occur during CH are unclear. This study compared the effects of nitroprusside and remifentanil on hemodynamics using a noninvasive cardiac output monitor (Cheetah NICOM(®); Cheetah Medical Inc., Maidenhead, Berkshire, UK) for endoscopic sinus surgery (ESS).

METHODS

Twenty-eight adult patients scheduled for ESS were randomly assigned to the nitroprusside group (n = 14) or remifentanil group (n = 14). After anesthesia induction, hypotension was induced with continuous infusion of nitroprusside or remifentanil at a target mean arterial blood pressure (MAP) of 60-70 mmHg. Cardiac index (CI), stroke volume index (SVI) and total peripheral resistance index (TPRI) were measured at 10-min intervals.

RESULTS

The heart rate was higher and SVI was lower in the nitroprusside group than in the remifentanil group during CH. There were no significant differences in MAP, CI or TPRI between the two groups. Both nitroprusside and remifentanil reduced MAP and TPRI during CH compared with baseline values. However, there was no significant change in CI.

CONCLUSIONS

Both nitroprusside and remifentanil were effective to induce CH and maintain CI during CH.

Accuracy of impedance cardiography for evaluating trends in cardiac output: a comparison with oesophageal Doppler

BACKGROUND

Impedance cardiography (ICG) enables continuous, beat-by-beat, non-invasive, operator-independent, and inexpensive cardiac output (CO) monitoring. We compared CO values and variations obtained by ICG (Niccomo™, Medis) and oesophageal Doppler monitoring (ODM) (CardioQ™, Deltex Medical) in surgical patients.

METHODS

This prospective, observational, single-centre study included 32 subjects undergoing surgery with general anaesthesia. CO was measured simultaneously with ICG and ODM before and after events likely to modify CO (vasopressor administration and volume expansion). One hundred and twenty pairs of CO measurements and 94 pairs of CO variation measurements were recorded.

RESULTS

The CO variations measured by ICG correlated with those measured by ODM [r=0.88 (0.82-0.94), P<0.001]. Trending ability was good for a four-quadrant plot analysis with exclusion of the central zone (<10%) [95% confidence interval (CI) for concordance (0.86; 1.00)]. Moderate to good trending ability was observed with a polar plot analysis (angular bias: -7.2°; 95% CI -12.3°; -2.5°; with radial limits of agreement -38°; 24°). After excluding subjects with chronic obstructive pulmonary disease, a Bland-Altman plot showed a mean bias of 0.47 litre min(-1), limits of agreements between -1.24 and 2.11 litre min(-1), and a percentage error of 35%.

CONCLUSION

ICG appears to be a reliable method for the non-invasive monitoring of CO in patients undergoing general surgery.

The influence of different mechanical ventilator settings of peak inspiratory pressure on stroke volume variation in pediatric cardiac surgery patients

Background

The usefulness of dynamic parameters derived by heart-lung interaction for fluid responsiveness in pediatric patients has been revealed. However, the effects of peak inspiratory pressure (PIP) that could affect the absolute values and the accuracy in pediatric patients have not been well established.

Methods

Participants were 30 pediatric patients who underwent ventricular septal defect repair. After completion of surgical procedure and sternum closure, mean arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index and stroke volume variation (SVV) were measured at PIP 10 cmH₂O (PIP10), at PIP 15 cmH₂O (PIP15), at PIP 20 cmH₂O (PIP20) and at PIP 25 cmH₂O (PIP25).

Results

SVV at PIP15 was larger than that at PIP10 (13.7 ± 2.9% at PIP10 vs 14.7 ± 2.5% at PIP15, P < 0.001) and SVV at PIP20 was larger than that at PIP10 and PIP15 (13.7 ± 2.9% at PIP10 vs 15.4 ± 2.5% at PIP20, P < 0.001; 14.7 ± 2.5% at PIP15 vs 15.4 ± 2.5% at PIP20, P < 0.001) and SVV at PIP25 was larger than that at PIP10 and PIP15 and PIP20 (13.7 ± 2.9% at PIP10 vs 17.4 ± 2.4% at PIP25, P < 0.001; 14.7 ± 2.5% at PIP15 vs 17.4 ± 2.4% at PIP25, P < 0.001; 15.4 ± 2.5% at PIP20 vs 17.4 ± 2.4% at PIP25, P < 0.001).

Conclusions

SVV is affected by different levels of PIP in same patient and under same volume status. This finding must be taken into consideration when SVV is used to predict fluid responsiveness in mechanically ventilated pediatric patients.

A novel hypothesis comprehensively explains shock, heart failure and aerobic exhaustion through an assumed central physiological control of the momentary cardiovascular performance reserve

BACKGROUND

Heart failure (HF) and shock are incomprehensively understood, inconclusively defined and lack a single conclusive test. The proceedings that preceded and triggered clinical manifestations are occult. The relationships in between different shock and HF types and between each HF type and its matched shock are poorly understood.

THE ASSUMED HYPOTHESIS

We suggest that HF and shock are attributed to a momentary cardiovascular performance reserve - "the reserve". The reserve is controlled through an assumed central physiological mechanism that continuously detects and responds accordingly--"the reserve control". The assumed reserve is maximal at rest, and decreases with aerobic activity. When it decreases to a given threshold the reserve control alerts by induces manifestations of dyspnea and fatigue enforcing activity decrease, follow which the manifestations dissolve. HF is a condition of low reserve at baseline; hence, fatigue and dyspnea are frequently experienced following mild activity. Shock is assumed to occur when the cardiovascular reserve deteriorates below a sustainable limit where the reserve control induces a salvage-sacrifice response, preserving vital organ perfusion while impairing microcirculation effective perfusion in non-vital organ in which it causes cellular hypoxia followed by the familiar devastating cascade of events seen in shock.

DISCUSSION AND CONCLUSIONS

The hereby hypothesis may comprehensively explain the heart failure - shock puzzle as no alternative theory had ever succeeded. It provides the missing link between the different types of HF as of shock and in between. The hypothesis poses a great prove challenge but opens new research and clinical possibilities.

Preload reserve is restored in patients with decompensated chronic heart failure who respond to treatment

The authors designed this prospective study to show the relationship between preload reserve and treatment effectiveness of chronic heart failure (CHF). Fifty patients, aged 77±24 years, with decompensated CHF (B-type brain natriuretic peptide [BNP] >1000 pg/mL) were included. Preload reserve was assessed by the changes in contraction indices during a passive leg raise (PLR). Contraction indices were assessed noninvasively using Bioreactance technology. After 4 days of optimized therapy, the same variables were reassessed and treatment-induced differences were calculated. Treatment effectiveness was assessed by the 4-day changes in BNP, body weight, and thoracic fluid content. The authors then compared treatment-induced changes in preload reserve with treatment effectiveness. Therapy was associated with an overall decrease in heart rate, blood pressure, and cardiac power index (CPi) and with an increase in all preload reserve indices. Treatment effectiveness correlated well with changes in preload reserve. The best correlation was found between treatment-induced changes in BNP and in PLR-induced changes of CPi (R=0.63, P<.001). The PLR-induced changes in CPi increased from 21±48 to 51±48 in BNP responders and decreased from 34±34 to 5±19 mW/m(2) in BNP nonresponders (P<.0001). Hence, effective treatment, as indexed by a decrease in BNP, restores the preload reserve in patients with decompensated CHF.

Endpoints of resuscitation: what are they anyway?

Hemodynamic optimization of surgical patients during and after surgery in the Surgical Intensive Care Unit is meant to improve outcomes. These outcomes have been measured by Length Of Stay (LOS), rate of infection, days on ventilator, etc. Unfortunately, the adaptation of modern technology to accomplish this has been slow in coming. Ever since Shoemaker described in 1988 using a pulmonary artery catheter (PAC) to guide fluid and inotropic administration to deliver supranormal tissue oxygenation, many authors have written about different techniques to achieve this "hemodynamic optimization". Since the PAC and CVC have both gone out of favor for utilization to monitor and improve hemodynamics, many clinicians have resorted using the easy to use static measurements of blood pressure (BP), heart rate (HR), and urine output. In this paper, the authors will review why these static measurements are no longer adequate and review some of the newer technology that have been studied and proven useful. This review of newer technologies combined with laboratory measurements that have also proven to help guide the clinician, may provide the impetus to adopt new strategies in the operating rooms (OR) and SICU.

The ability of stroke volume variation measured by a noninvasive cardiac output monitor to predict fluid responsiveness in mechanically ventilated children

Continuous noninvasive cardiac output monitoring (NICOM) is a clinically useful tool in the pediatric setting. This study compared the ability of stroke volume variation (SVV) measured by NICOM with that of respiratory variations in the velocity of aortic blood flow (△Vpeak) and central venous pressure (CVP) to predict of fluid responsiveness in mechanically ventilated children after ventricular septal defect repair. The study investigated 26 mechanically ventilated children after the completion of surgery. At 30 min after their arrival in an intensive care unit, a colloid solution of 10 ml/kg was administrated for volume expansion. Hemodynamic variables, including CVP, stroke volume, and △Vpeak in addition to cardiac output and SVV in NICOM were measured before and 10 min after volume expansion. The patients with a stroke volume increase of more than 15 % after volume expansion were defined as responders. The 26 patients in the study consisted of 13 responders and 13 nonresponders. Before volume expansion, △Vpeak and SVV were higher in the responders (both p values <0.001). The areas under the receiver operating characteristic curves of △Vpeak, SVV, and CVP were respectively 0.956 (95 % CI 0.885-1.00), 0.888 (95 % CI 0.764-1.00), and 0.331 (95 % CI 0.123-0.540). This study showed that SVV by NICOM and △Vpeak by echocardiography, but not CVP, reliably predicted fluid responsiveness during mechanical ventilation after ventricular septal defect repair in children.

Non-invasive cardiac output monitoring in preterm infants undergoing patent ductus arteriosus ligation: a comparison with echocardiography

BACKGROUND

Non-invasive cardiac output monitoring (NICOM; NICOM™) may be useful in the management of extremely premature preterm infants.

OBJECTIVES

To evaluate a new bioreactance-based method of continuous NICOM in preterm infants following patent ductus arteriosus (PDA) ligation.

METHODS

Infants underwent three paired NICOM and echocardiography assessments of stroke volume (SV) and left ventricular output (LVO) in the postoperative period: at 1, 6-8, and 16-18 h postoperatively. NICOM- and echocardiography-measured SV and LVO during those periods were compared using Bland-Altman analysis and the intraclass correlation coefficient (ICC).

RESULTS

Twenty-five infants with a median (interquartile range) gestational age and birth weight of 25.0 weeks (24.5-25.9) and 700 g (615-775), respectively, were included. The overall systematic bias (limits of agreement) across all time points between the NICOM and echocardiography SV readings was 39% (8-69) with NICOM consistently underestimating echocardiography values. There was moderate consistency between NICOM and echocardiography SV values (ICC 0.78, p < 0.001). Compared with the 1-hour scans, the 6- to 8- and 16- to 18-hour scans had increased biases of 7.9% (95% CI 2.5-13.2) and 9.7% (95% CI 3.6-15.8), respectively.

CONCLUSION

Continuous LVO measurement using NICOM was feasible and demonstrated a consistent systematic bias compared with echocardiography in unstable extremely preterm infants without a PDA ligation. NICOM may be used as a trending tool for continuous monitoring in this population, but wide limits of agreement and increasing bias over time suggest it is not interchangeable with echocardiography. © 2014 S. Karger AG, Basel.

A comparison of noninvasive bioreactance with oesophageal Doppler estimation of stroke volume during open abdominal surgery: an observational study

CONTEXT

The anaesthetist must maintain tissue perfusion by ensuring optimal perioperative fluid balance. This can be achieved using less invasive cardiac output monitors such as oesophageal Doppler monitoring (ODM). Other less invasive cardiac output monitors using bio-impedence technology (noninvasive cardiac output monitoring, NICOM) may have a role in monitoring the circulation and informing fluid management decisions.

OBJECTIVE

To compare estimates of stroke volume from ODM with those from NICOM, a noninvasive monitor using bioreactance, a modification of transthoracic bio-impedence.

DESIGN

An observational study.

SETTING

Manchester Royal Infirmary, UK. Data collected in 2011 and 2012.

PARTICIPANTS

Twenty-two patients scheduled for major, open abdominal surgery. Reasons for noninclusion: atrial fibrillation; heart failure; oesophageal disease; lack of capacity; and known sensitivity to colloid.

INTERVENTION

All patients had oesophageal Doppler cardiac output monitoring as a standard element of anaesthesia care. We placed NICOM Bioreactance electrodes and recorded stroke volume estimates from both devices. Fluid challenges were given by the anaesthetist and the haemodynamic responses were recorded.

MAIN OUTCOME MEASURE

Stroke volume during surgery. The Bland-Altman method was used to compare bias and limits of agreement for stroke volume and cardiac output. Fluid responders were defined as patients who increased stroke volume by at least 10% after fluid loading. The precision of each device was calculated during periods of haemodynamic stability.

RESULTS

We made 788 acceptable measurements of cardiac output. The bias was -6.9 ml and the limits of agreement were -22.9 to 36.8 ml. The percentage error was 57%. Average precision for both the ODM and NICOM were similar, 8.5% (SD 5.4%) and 8.7% (SD 3.2%). The concordance for the stroke volume change following fluid challenge was 90.5%. Both devices produced unacceptable readings with electrical diathermy.

CONCLUSION

Simultaneous stroke volume estimations made by noninvasive Bioreactance (NICOM) and oesophageal Doppler showed bias and limits of agreement that are not clinically acceptable. The measurements made by these two devices cannot be regarded as interchangeable.

Hypoxic exercise training improves cardiac/muscular hemodynamics and is associated with modulated circulating progenitor cells in sedentary men

BACKGROUND

Circulating progenitor cells (CPCs) improve cardiovascular function and organ perfusion by enhancing the capacities of endothelial repair and neovasculogenesis. This study investigates whether exercise regimens with/without hypoxia affect cardiac and muscular hemodynamics by modulating CPCs and angiogenic factors.

METHODS

Forty sedentary males were randomly divided into hypoxic (HT, n=20) and normoxic (NT, n=20) training groups. The subjects were trained on a bicycle ergometer at 60%VO(2max) under 15% (HT) or 21% (NT) O2 conditions for 30 min daily, five days weekly for five weeks.

RESULTS

After the five-week interventions, the HT group exhibited a larger improvement in aerobic capacity than the NT group. Furthermore, the HT regimen (i) enhanced cardiac output (Q(H)) and perfusion (Q(M))/oxygenation of vastus lateralis during exercise; (ii) increased levels of CD34(+)/KDR(+)/CD117(+), CD34(+)/KDR(+)/CD133(+), and CD34(+)/KDR(+)/CD31(+) cells in blood; (iii) promoted the proliferative capacity of these CPC subsets, and (iv) elevated plasma nitrite/nitrate, stromal cell-derived factor-1 (SDF-1), matrix metalloproteinase-9 (MMP-9), and vascular endothelial growth factor-A (VEGF-A) concentrations. Despite the lack of changes in Q(H) and the number or proliferative capacity of CD34(+)/KDR(+)/CD117(+) or CD34(+)/KDR(+)/CD31(+) cells, the NT regimen elevated both Q(M) and plasma nitrite/nitrate levels and suppressed the shedding of endothelial cells (CD34(-)/KDR(+)/phosphatidylserine(+) cells).

CONCLUSIONS

The HT regimen improves cardiac and muscular hemodynamic adaptations, possibly by promoting the mobilization/function of CPCs and the production of angiogenic factors.

Perioperative hemodynamic monitoring

Hemodynamic monitoring is the cornerstone of perioperative anesthetic monitoring. In the unconscious patient, hemodynamic monitoring not only provides information relating to cardiac output, volume status and ultimately tissue perfusion, but also indicates depth of anesthesia and adequacy of pain control. In the 21st century the anesthesiologist has an array of devices to choose from. No single device provides a complete assessment of hemodynamic status, and the use of all devices in every situation is neither practical nor appropriate. This article aims to provide the reader with an overview of the devices currently available, and the information they provide, to assist anesthesiologists in the selection of the most appropriate devices for any given situation.

The effects of propofol and dexmedetomidine infusion on fluid responsiveness in critically ill patients

BACKGROUND

We studied the effects of propofol or dexmedetomidine on preload dependency and fluid responsiveness in critically ill patients.

METHODS

In the study, we included 91 patients with acute circulatory failure (70 ± 15 y) who received propofol (n = 45 patients, PROP group) or dexmedetomidine (n = 46 patients, DEX group). An initial passive leg-raising (PLR 1) test was performed in all patients to evaluate preload dependency at baseline. Propofol and dexmedetomidine were infused and titrated according to the Richmond Agitation Sedation Scale; the results ranged from -2 to -1, and the bispectral index values ranged from 60-75. A second PLR test (PLR 2) was performed before administration of a 250-mL normal saline fluid challenge over a 5-min period. We obtained central venous pressure and cardiac index (CI) measurements before and after the two PLR tests and volume expansion. An increase of ≥10% in CI during PLR was considered to be a positive test finding that was indicative of preload dependency, whereas an increase of <10% in CI during PLR was considered to be a negative test finding.

RESULTS

At baseline, 22 of 45 patients had negative PLR 1 in the PROP group, whereas 20 of 46 patients had negative PLR 1 in the DEX group. After propofol or dexmedetomidine sedation, there were significant decreases in CI (-9.5% [±6.6%] versus -16.4% [±8.5%], P < 0.001) in the PROP and DEX groups, respectively. In the PROP group, there were significant increases in CI (+18.4% [±9.5%] versus +10.7% [±12.3%], P < 0.05) induced by PLR 2 compared with that induced by PLR 1. In the DEX group, there were no significant increases in CI (+13.2% [±14.9%] versus +12.8% [±17.7%]) induced by PLR 2 compared with that induced by PLR 1. Although the mean arterial pressure values increased comparably with the volume expansion observed in both groups, the volume expansion resulted in a significantly higher increase in CI compared with the baseline values in the PROP group (3.2 ± 0.8 versus 3.2 ± 0.7 L/min/m(2)) but not in the DEX group (2.9 ± 0.7 versus 3.1 ± 0.8 L/min/m(2), P < 0.05).

CONCLUSIONS

We observed that propofol infusion, but not dexmedetomidine infusion, can increase preload dependency and fluid responsiveness in patients with circulatory failure.

Should high-intensity-aerobic interval training become the clinical standard in heart failure?

Aerobic exercise training in the heart failure (HF) population is supported by an extensive body of literature. The clinically accepted model for exercise prescription is currently moderate-intensity-aerobic continuous training (MI-ACT). Documented benefits from the literature include improvements in various aspects of physiologic function, aerobic exercise capacity and quality of life while the impact on morbidity and mortality is promising but requires further investigation. Recently, however, a body of evidence has begun to emerge demonstrating high-intensity-aerobic interval training (HI-AIT) can be performed safely with impressive improvements in physiology, functional capacity and quality of life. These initial findings have led some to question the long-standing clinical approach to aerobic exercise training in patients with HF (i.e., MI-ACT), implying it should perhaps be replaced with a HI-AIT model. This is a potentially controversial paradigm shift given the potential increase in adverse event risk associated with exercising at higher intensities, particularly in the HF population where the likelihood of an untoward episode is already at a heightened state relative to the apparently healthy population. The present review therefore addresses key issues related to HI-AIT in the HF population and makes recommendations for future research and current clinical practice.

Evolution of bioimpedance: a circuitous journey from estimation of physiological function to assessment of body composition and a return to clinical research

BACKGROUND/OBJECTIVES

Bioimpedance is the collective term that describes safe, non-invasive methods to measure the electrical responses to the introduction of a low-level, alternating current into a living organism, and the biophysical models to estimate body composition from bioelectrical measurements. Although bioimpedance techniques have been used for more than 100 years to monitor assorted biological components, the desire to translate bioelectrical measurements into physiological variables advanced the creation of empirical prediction models that produced inconsistent results.

SUBJECTS/METHODS

This paper succinctly reviews the origin, and critically evaluates the conceptual models and the implementation of bioimpedance in clinical research, including indirect assessment of assorted physiological functions and body composition (fluid volumes and fat-free mass), classification of hydration, regional fluid accumulation, prognosis in disease and wound healing.

RESULTS

Despite widespread and mounting interest in the use of bioimpedance to characterise body structure and function, most experimental findings reveal the limitations of existing physical models and reliance on multiple regression models for use in assessments of an individual.

CONCLUSIONS

Contemporary applications of bioimpedance emphasise the value of bioimpedance variables per se in some novel biomedical applications with the objective of identifying opportunities for future outcome-based research.

Advances in monitoring and management of shock

Early recognition and treatment of pediatric shock, regardless of cause, decreases mortality and improves outcome. In addition to the conventional parameters (eg, heart rate, systolic blood pressure, urine output, and central venous pressure), biomarkers and noninvasive methods of measuring cardiac output are available to monitor and treat shock. This article emphasizes how fluid resuscitation is the cornerstone of shock resuscitation, although the choice and amount of fluid may vary based on the cause of shock. Other emerging treatments for shock (ie, temperature control, extracorporeal membrane oxygenation/ventricular assist devices) are also discussed.

Feasibility of noninvasive hemodynamic monitoring by bioreactance for air-evacuated casualties

BACKGROUND

The purpose of this study was to assess the feasibility of hemodynamic monitoring by bioreactance during the air evacuation of war casualties.

METHODS

From June 2011 to January 2012, the French Air Force used a noninvasive bioreactance monitor during the aeromedical evacuation of patients with severe battle injury. Patients were continuously monitored from takeoff (baseline) until arrival. Cardiac index, quality, and viability of signal and fluctuations in values were assessed during the entire flight.

RESULTS

Eighteen patients were included, and monitoring was possible for 16 patients. The implementation of the monitoring was found to be straightforward for both doctors and paramedics, and we observed no loss of signal or interference during the flights. Cardiac index decreased significantly during the takeoff and returned to baseline value after the 50th minute of flight.

CONCLUSION

The application of noninvasive bioreactance hemodynamic monitoring is feasible and pertinent in the specific environment of aeromedical evacuation. This monitoring can be particularly useful during the strategic evacuation of patients with severe injury from field hospital to tertiary centers.

LEVEL OF EVIDENCE

Care management study, level V.

Noninvasive Cardiac Output Monitoring in Paediatric Cardiac Surgery: Correlation between Change in Thoracic Fluid Content and Change in Patient Body Weight

Objective:

Change in thoracic fluid content (TFC) derived via a bioreactance technique with a noninvasive cardiac output monitoring device (NICOM) reportedly shows a good correlation with the amount of fluid removed. The present study prospectively evaluated the utility and clinical application of TFC in the intraoperative fluid management of paediatric patients with congenital heart disease, undergoing cardiac surgery with bioreactance-based noninvasive monitoring.

Methods:

Haemodynamic parameters, patient body weight and parameters derived from the NICOM device (including cardiac output, cardiac index, TFC, percentage change in TFC compared with baseline [TFCd0%] and stroke volume variation) were recorded after anaesthesia induction but before surgical incision, and just before departure from the operating room to the intensive care unit.

Results:

In the 80 paediatric patients included in this study, linear regression analyses demonstrated good correlations between body weight gain and TFCd0%, between body weight gain % and TFCd0%, and between intra -operative fluid balance and TFCd0%.

Conclusion:

TFCd0% may be a useful indicator for intraoperative fluid management in paediatric patients with congenital heart disease, undergoing cardiac surgery.

Emergency department noninvasive (NICOM) cardiac outputs are associated with trauma activation, patient injury severity and host conditions and mortality

BACKGROUND

Anoninvasive cardiac output (CO) monitor (NICOM), using Bioreactance technology, has been validated in several nontrauma patient studies. We hypothesized that NICOM CO would have more significant associations with clinical conditions than would systolic blood pressure (sBP).

METHODS

This is a prospective observational study of consecutive trauma activation patients during the first 10 to 60 minutes after emergency department arrival.

RESULTS

Analysis includes 270 consecutive trauma activation patients with 1,568 observations. CO was decreased (p ≤ 0.002) with major blood loss, hypotension, red blood cell transfusion, Injury Severity Score (ISS) higher than 20, low PetCO₂, abnormal pupils, elderly, preexisting conditions, low body surface area level, females, hypothermia, and death. CO was increased (p < 0.0001) with base deficit, ethanol positivity, and illicit drug positivity. The sBP was decreased (p ≤ 0.0005) with major blood loss, red blood cell transfusion, low PetCO₂, low body surface area level, and illicit drug positivity. The sBP was increased (p e 0.01) with ISS higher than 20, elderly, and preexisting conditions. Total significant condition associations were CO 83% (15 of 18 patients) and sBP 47% (8 of 17 patients; p = 0.03). In hypotensive patients, CO was lower with major blood loss (3.3 ± 2.1 L/ min) than without (6.0 ± 2.2 L/min; p < 0.0001). Of survivors with ISS 15 or higher, NICOM patients experienced a shorter hospital length of stay (10.5 days) when compared with 2009 and 2010 patients (14.0 days; p = 0.03).

CONCLUSION

The multiple associations of CO with patient conditions imply that NICOM provides an objective and clinically valid, relevant, and discriminate measure of cardiac function in acutely injured trauma activation patients. NICOM use may be associated with a shorter length of stay in surviving patients with complex injuries.