Ronald J. Manning

Can near-infrared spectroscopy identify the severity of shock in trauma patients?

BACKGROUND Our recent experimental study showed that peripheral muscle tissue oxygen saturation (StO2), determined noninvasively by near-infrared spectroscopy (NIRS), was more reliable than systemic hemodynamics or invasive oxygenation variables as an index of traumatic shock. The purpose of this study was to establish the normal range of thenar muscle StO2 in humans and the relationship between shock state and StO2 in trauma patients. METHODS This was a prospective, nonrandomized, observational, descriptive study in normal human volunteers (n = 707) and patients admitted to the resuscitation area of our Level I trauma center (n = 150). To establish a normal StO2 range, an NIRS probe was applied to the thenar eminence of volunteers (normals). Subsequently, in a group of trauma patients, an NIRS probe was applied to the thenar eminence and data were collected and stored for offline analysis. StO2 monitoring was performed continuously and noninvasively, and values were recorded at 2-minute intervals. Five moribund trauma patients were excluded. Members of our trauma faculty, blinded to StO2 values, classified each patient into one of four groups (no shock, mild shock, moderate shock, and severe shock) using conventional physiologic parameters. RESULTS Mean +/- SD thenar StO2 values for each group were as follows: normals, 87 +/- 6% (n = 707); no shock, 83 +/- 10% (n = 85); mild shock, 83 +/- 10% (n = 19); moderate shock, 80 +/- 12% (n = 14); and severe shock, 45 +/- 26% (n = 14). The thenar StO2 values clearly discriminated the normals or no shock patients and the patients with severe shock (p < 0.05). CONCLUSION Decreased thenar muscle tissue oxygen saturation reflects the presence of severe hypoperfusion and near-infrared spectroscopy may be a novel method for rapidly and noninvasively assessing changes in tissue dysoxia.

Prehospital Intubations and Mortality: A Level 1 Trauma Center Perspective

BACKGROUND: Ryder Trauma Center is a Level 1 trauma center with approximately 3800 emergency admissions per year. In this study, we sought to determine the incidence of failed prehospital intubations (PHI), its correlation with hospital mortality, and possible risk factors associated with PHI. METHODS: A prospective observational study was conducted evaluating trauma patients who had emergency prehospital airway management and were admitted during the period between August 2003 and June 2006. The PHI was considered a failure if the initial assessment determined improper placement of the endotracheal tube or if alternative airway management devices were used as a rescue measure after intubation was attempted. RESULTS: One-thousand-three-hundred-twenty patients had emergency airway interventions performed by an anesthesiologist upon arrival at the trauma center. Of those, 203 had been initially intubated in the field by emergency medical services personnel, with 74 of 203 (36%) surviving to discharge. When evaluating the success of the intubation, 63 of 203 (31%) met the criteria for failed PHI, all of them requiring intubation, with only 18 of 63 (29%) surviving to discharge. These patients had rescue airway management provided either via Combitube® (n = 28), Laryngeal Mask Airway® (n = 6), or a cricothyroidotomy (n = 4). An additional 25 of 63 patients (12%) had unrecognized esophageal intubations discovered upon the initial airway assessment performed on arrival. We found no difference in mortality between those patients who were properly intubated and those who were not. Several other variables, including age, gender, weight, mechanism of injury, presence of facial injuries, and emergency medical services were not correlated with an increased incidence of failed intubations. CONCLUSION: This prospective study showed a 31% incidence of failed PHI in a large metropolitan trauma center. We found no difference in mortality between patients who were properly intubated and those who were not, supporting the use of bag-valve-mask as an adequate method of airway management for critically ill trauma patients in whom intubation cannot be achieved promptly in the prehospital setting.

First report on safety and efficacy of hetastarch solution for initial fluid resuscitation at a level 1 trauma center.

BACKGROUND For logistics, the US Army recommends Hextend (Hospira; 6% hetastarch in buffered electrolyte, HET) for battlefield resuscitation. To support this practice, there are laboratory data, but none in humans. To test the hypothesis that HET is safe and effective in trauma, we reviewed our first 6 months of use at a civilian level 1 trauma center. STUDY DESIGN From June 2008 to December 2008, trauma patients received standard of care (SOC) +/- 500 to 1,000 mL of HET within 2 hours of admission at surgeon discretion. Each case was reviewed, with waiver of consent. RESULTS There were 1,714 admissions; 805 received HET and 909 did not. With HET versus SOC, overall mortality was 5.2% versus 8.9% (p = 0.0035) by univariate analysis. Results were similar after penetrating injury only (p = 0.0016) and in those with severe injury, defined by Glasgow Coma Scale <9 (p = 0.0013) or Injury Severity Score >26 (p = 0.0142). After HET, more patients required ICU admission (40.9% vs. 34.5%; p = 0.0334) and transfusions of blood (34.4% vs. 20.2%; p = 0.0014) or plasma (20.7% vs. 12.2%; p = 0.0251), but there were no treatment-related differences in prothrombin time or partial thromboplastin time. The 24-hour urine outputs and requirements for blood, plasma, and other fluids were similar. However, increased early deaths with SOC implicate possible selection bias. If that factor was controlled for with multivariate analysis, the same trends were present, but the apparent treatment effects of HET were no longer statistically significant. CONCLUSIONS In the first trial to date in hemodynamically unstable trauma patients, and the largest trial to date in any population of surgical patients, initial resuscitation with HET was associated with reduced mortality and no obvious coagulopathy. A randomized blinded trial is necessary before these results can be accepted with confidence.

Heart rate variability is an independent predictor of morbidity and mortality in hemodynamically stable trauma patients.

BACKGROUND Reduced heart rate variability (HRV) reflects autonomic dysfunction and can triage patients better than routine trauma criteria or vital signs. However, there is questionable specificity and no consensus measurement technique. The purpose of this study was to analyze whether factors that alter autonomic function affect the specificity of HRV for assessing traumatic injury. METHODS We evaluated 216 hemodynamically stable adults (3:1 M:F; 97:3 blunt:penetrating; age 49 years ± 1 year, mean ± standard error) undergoing computed axial tomography (CT) scan to rule out traumatic brain injury (TBI). All were prospectively instrumented with a Mars Holter system (GE Healthcare, Milwaukee, WI). HRV was determined offline using time domain (standard deviation of normal-normal intervals, root-mean-square successive difference) and frequency domain (very low frequency [VLF], LF, wideband frequency, high frequency [HF], low to HF index ratio) calculations from 15-minute electrocardiogram and correlated with routine vital signs, mortality, TBI, morbidity, length of stay (LOS), and comorbidities. Significance (p ≤ 0.05) was determined using nonparametric analysis, Students t test, analysis of variance, or multiple logistic regression. RESULTS VLF alone predicted survival, severity of TBI, intensive care unit LOS, and hospital LOS (all p < 0.05). Beta-blockers or diabetes had no effect, whereas age, sedation, mechanical ventilation, spinal cord injury, and intoxication influenced one or more of the variables with age being the most powerful confounder (all p < 0.05). Except for the Glasgow Coma Scale, no other routine trauma or hemodynamic criteria correlated with any of these outcomes. CONCLUSIONS Decreased VLF is an independent predictor of mortality and morbidity in hemodynamically stable trauma patients. Other time and other frequency domain variables correlated with some, but not all, outcomes. All were heavily influenced by factors that alter autonomic function, especially patient age.

Insertion of central venous catheters induces a hypercoagulable state

BACKGROUND Central venous catheters (CVCs) increase the risk of venous thromboembolism. We have previously demonstrated that pulmonary artery catheters are associated with a hypercoagulable state in an animal model and in patients. The purpose of this study is to determine whether the insertion of a CVC is associated with a similar response. METHODS Animal: 7F femoral artery catheters were placed in healthy anesthetized swine (N = 16). Serial arterial blood samples were drawn immediately before and after an 8.5F jugular vein CVC and then for 3 hours after CVC removal. Samples were analyzed using kaolin-activated thromboelastography (TEG) at precisely 2 minutes. Human: An institutional review board–approved prospective observational trial was conducted, with informed consent, in patients with critical illness (N = 8) at a Level I trauma center. Blood was drawn from indwelling arterial catheters immediately before and 60 minutes after CVC insertion. Samples were stored in sodium citrate for 15 minutes before TEG. Routine and special coagulation tests were performed on stored samples in the hospital pathology laboratory. RESULTS Insertion of a CVC decreased TEG clotting time (R) by 55% in swine and by 29% in humans (p < 0.001 and 0.019, respectively). Initial clot formation time (K) was reduced by 41% in swine and by 36% in humans (p = 0.003 and 0.019). Fibrin cross-linking (&agr;) was accelerated by 28% in swine and by 17% in humans (p = 0.007 and 0.896), but overall clot strength (maximum amplitude) was not affected. There was no change in routine or special coagulation factors, including von Willebrand factor, antithrombin III, prothrombin time, international normalized ratio, or activated partial thromboplastin time. In animals, the hypercoagulable TEG response was persistent for 3 hours after CVC removal and was prevented by pretreatment with enoxaparin (n = 4) but not heparin (n = 2). CONCLUSION In healthy swine and patients with critical illness, a systemic hypercoagulable state occurred after CVC insertion, and this may partially account for an increased risk of venous thromboembolism. However, because the sample size was small and not powered to detect changes in coagulation proteins, no inferences can be made about the mechanism for the hypercoagulable response.

Recent Advances in Forward Surgical Team Training at the U.S. Army Trauma Training Department.

U.S. Army Forward Surgical Teams (FSTs) are elite, multidisciplinary units that are highly mobile, and rapidly deployable. The mission of the FST is to provide resuscitative and damage control surgery for stabilization of life-threatening injuries in austere environments. The Army Trauma Training Center began in 2001 at the University of Miami Ryder Trauma Center under the direction of COL T. E. Knuth, MC USA (Ret.), as a multimodality combination of lectures, laboratory exercises, and clinical experiences that provided the only predeployment mass casualty and clinical trauma training center for all FSTs. Each of the subsequent five directors has restructured the training based on dynamic feedback from trainees, current military needs, and on the rapid advances in combat casualty care. We have highlighted these evolutionary changes at the Army Trauma Training Center in previous reviews. Under the current director, LTC J. M. Seery, MC USA, there are new team-building exercises, mobile learning modules and simulators, and other alternative methods in the mass casualty exercise. This report summarizes the latest updates to the state of the art training since the last review.