Allen Kong

Standard prophylactic enoxaparin dosing leads to inadequate anti-Xa levels and increased deep venous thrombosis rates in critically Ill trauma and surgical patients

BACKGROUND Deep venous thromboses (DVT) continue to cause significant morbidity in critically ill patients. Standard prophylaxis for high risk patients includes twice-daily dosing with 30 mg enoxaparin. Despite prophylaxis, DVT rates still exceed 10% to 15%. Anti-Xa levels are used to measure the activity of enoxaparin and 12-hour trough levels <or=0.1 IU/mL have been associated with higher rates of DVT in orthopedic patients. We hypothesized that low Anti-Xa levels would be found in critically ill trauma and surgical patients and that low levels would be associated with higher rates of DVT. METHODS All patients on the surgical intensive care unit (ICU) service were prospectively followed. In the absence of contraindications, patients were given prophylactic enoxaparin and anti-Xa levels were drawn after the third dose. Trough levels <or=0.1 IU/mL were considered low. Screening duplex exams were obtained within 48 hours of admission and then weekly. Patients were excluded if they did not receive a duplex, if they had a prior DVT, or if they lacked correctly timed anti-Xa levels. DVT rates and demographic data were compared between patients with low and normal anti-Xa levels. RESULTS Data were complete for 54 patients. Eighty-five percent suffered trauma (Injury Severity Score of 25 +/- 12) and 74% were male. Overall, 27 patients (50%) had low anti-Xa levels. Patients with low anti-Xa levels had significantly more DVTs than those with normal levels (37% vs. 11%, p = 0.026), despite similar age, body mass index, Injury Severity Score, creatinine clearance, high risk injuries, and ICU/ventilator days. CONCLUSION Standard dosing of enoxaparin leads to low anti-Xa levels in half of surgical ICU patients. Low levels are associated with a significant increase in the risk of DVT. These data support future studies using adjusted-dose enoxaparin.

Closed-loop fluid administration compared to anesthesiologist management for hemodynamic optimization and resuscitation during surgery: an in vivo study.

BACKGROUND: Closed-loop systems have been designed to assist practitioners in maintaining stability of various physiologic variables in the clinical setting. In this context, we recently performed in silico testing of a novel closed-loop fluid management system that is designed for cardiac output and pulse pressure variation monitoring and optimization. The goal of the present study was to assess the effectiveness of this newly developed system in optimizing hemodynamic variables in an in vivo surgical setting. METHODS: Sixteen Yorkshire pigs underwent a 2-phase hemorrhage protocol and were resuscitated by either the Learning Intravenous Resuscitator closed-loop system or an anesthesiologist. Median hemodynamic values and variation of hemodynamics were compared between groups. RESULTS: Cardiac index (in liters per minute per square meter) and stroke volume index (in milliliters per square meter) were higher in the closed-loop group compared with the anesthesiologist group over the protocol (3.7 [3.4–4.1] vs 3.5 [3.2–3.9]; 95% Wald confidence interval, −0.5 to −0.23; P < 0.0005 and 40 [34–45] vs 36 [31–38]; 95% Wald confidence interval, −5.9 to −3.1; P < 0.0005, respectively). There was no significant difference in total fluid administration between the closed-loop and anesthesiologist groups (3685 [3230–4418] vs 3253 [2735–3926] mL; 95% confidence interval, −1651 to 431; P = 0.28). Closed-loop group animals also had lower coefficients of variance of cardiac index and stroke volume index during the protocol (11% [10%–16%] vs 22% [18%–23%]; confidence interval, 0.8%–12.3%; P = 0.02 and 11% [8%–16%] vs 17% [13%–21%]; confidence interval, 0.2%–11.4%; P = 0.04, respectively). CONCLUSION: This in vivo study building on previous simulation work demonstrates that the closed-loop fluid management system used in this experiment can perform fluid resuscitation during mild and severe hemorrhages and is able to maintain high cardiac output and stroke volume while reducing hemodynamic variability.

Which central venous catheters have the highest rate of catheter-associated deep venous thrombosis: a prospective analysis of 2,128 catheter days in the surgical intensive care unit.

BACKGROUND Catheter-associated deep venous thromboses (CADVTs) are a common occurrence in the surgical intensive care unit (SICU), necessitating central venous catheter (CVC) removal and replacement. Previous studies evaluating risk factors for CADVT in SICU patients are limited, and most lack a true denominator of all CVC days. We sought to determine the true incidence of and risk factors for CADVT based on patient characteristics as well as CVC site, type, and duration of insertion. METHODS The following data from all SICU patients in two urban Level I trauma centers were prospectively collected from 2009 to 2012: demographics, risk factors for DVT, CVC site/type/duration, and duplex results. Sites included the subclavian (SC), internal jugular (IJ), arm (for peripherally inserted central catheter [PICC] lines), and femoral. Types included multilumen (ML), introducer/hemodialysis (I/HD), and PICC. High-risk patients received weekly screening duplex examinations and a CADVT was defined as a DVT being detected on duplex with a CVC in place or within 7 days of removal. Rates of CADVT were normalized per 1,000 CVC days, and independent predictors of CADVT were determined using logistic regression. RESULTS Data were complete for 184 patients, 354 CVCs, and 2,128 CVC days. Fifty-nine CADVTs were diagnosed in 28% of patients. Rates of CADVT were 9 per 1,000 catheter days for SC, 61 for IJ (p < 0.01 vs. SC), 27 for arm (p < 0.01), 36 for femoral (p < 0.01), 22 for ML, 57 for I/HD (p < 0.01 vs. ML), and 27 for PICC (p = 0.24). After adjusting for patient risk factors, predictors of CADVT included the IJ and arm sites (odds ratio, 6.0 and 3.0 compared with SC) and the I/HD type (odds ratio, 2.6 compared with ML, all p < 0.05). CONCLUSION The IJ and arm sites and I/HD type are associated with increased CADVT. These data may be used to determine the optimal site and type of CVC for insertion. LEVEL OF EVIDENCE Prognostic/epidemiologic study, level III.

Risk factors for venous thromboembolism in critically ill trauma patients who cannot receive chemical prophylaxis

BACKGROUND Standard venous thromboembolism (VTE) prevention for critically ill trauma patients includes sequential compression devices and chemical prophylaxis. When contraindications to anticoagulation are present, prophylactic inferior vena cava filters (IVCF) may be used to prevent pulmonary emboli (PE) in high-risk patients, but specific indications are lacking. We sought to identify independent predictors of VTE in critically-ill trauma patients who cannot receive chemical prophylaxis in order to identify a subset of patients who may benefit from aggressive screening and/or prophylactic IVCF placement. METHODS All trauma patients in the surgical ICU from 2008 to 2009 were prospectively followed. Patients with an ICU length of stay ≥2 days who had contraindications to prophylactic anticoagulation were included. Screening duplex exams were obtained within 48 h of admission and then weekly. CT-angiography for PE was obtained if clinically indicated. Patients were excluded if they did not receive a duplex or if they had a post-injury VTE prior to ICU admission. Data regarding VTE rates (lower extremity [LE] DVT or PE), demographics, past medical history (PMH), injuries, and surgeries were collected. Univariate and multivariable analyses were performed to identify independent predictors of VTE with a p<0.05. RESULTS 411 trauma patients with a mean age of 48 (SD 22) years and 8 (SD 9) ICU days were included. 72% were male and the mean ISS was 22 (SD 13). 30 (7.3%) patients developed VTE: 28 (6.8%) with LEDVT and 2 (0.5%) with PE. Risk factors for VTE with a p<0.2 on univariate analysis included: PMH of DVT, injury severity score (ISS), extremity fractures (Fx), and a pelvis or LE extremity Fx repair. After logistic regression, only PMH of DVT (OR=22.6) and any extremity Fx (OR=2.4) remained as independent predictors. CONCLUSION VTE occur in 7% of critically injured trauma patients who cannot receive chemical prophylaxis. Aggressive screening and/or prophylactic IVCF placement may be considered in patients with a PMH of DVT or extremity fractures when anticoagulation is prohibited.

Laser Doppler Imaging for Early Detection of Hemorrhage

BACKGROUND Laser Doppler Imaging (LDI) is a noninvasive means to measure blood flow through the superficial skin capillary plexus using flux units. Our objective was to determine the ability of LDI of the skin to detect and quantify rapid, severe hemorrhage. METHODS Five Yucatan mini-pigs (25-35 kg) underwent controlled hemorrhage of 25 mL/kg blood for 20 minutes. Median flux of a 10 cm × 10 cm area of the lower abdomen was measured at 2-minute intervals from initiation of hemorrhage to resuscitation with concurrent measurement of heart rate (HR), systolic blood pressure (SBP), and mean arterial pressure (MAP). RESULTS Average time to a change of 5 U in flux following start of hemorrhage was 2.4 minutes. This was significantly faster than time to change in HR (19.2 minutes, p < 0.05) and showed a trend toward more rapid identification of hemorrhage relative to changes in SBP (3.2 minutes, p = 0.157) and MAP (3.6 minutes, p = 0.083). Flux changes occurred at smaller % total blood volume lost than HR (3.94% vs. 28.8%, p < 0.05) and trended toward smaller volume identification than SBP (4.88%, p = 0.180) and MAP (5.36%, p = 0.102). Average correlation (ρ) of blood volume lost to flux was -0.974; HR, 0.346; SBP, -0.978; and MAP, -0.975. A change of 5 flux units was significantly more sensitive for hemorrhage than a change of 5 beats per minute in HR or 5 mm Hg in SBP or MAP (0.596 vs. 0.169, 0.438, and 0.287 respectively, all p < 0.05). CONCLUSION LDI is a sensitive, specific, and early means to detect and quantify severe hemorrhage.

Predictors of Hazardous Drinking Behavior in 1,340 Adult Trauma Patients: A Computerized Alcohol Screening and Intervention Study

BACKGROUND Alcohol screening and brief intervention (SBI) is used to decrease alcohol consumption, health care costs, and injury recidivism in trauma patients. Despite SBI being mandated for trauma centers, various concerns have led many centers to conduct SBI only on patients with a detectable blood alcohol concentration (BAC). We sought to determine the predictive nature of BAC on hazardous drinking behavior. STUDY DESIGN Adult trauma patients were included if they received an SBI before discharge. SBI was administered using a computerized alcohol screening and intervention (CASI) system with the Alcohol Use Disorder Identification Test (AUDIT). Data regarding demographics, injuries, and BAC were prospectively collected. Multivariate analyses were performed to identify independent predictors of hazardous drinking behavior. RESULTS Data were complete for 1,340 patients, with a mean age of 43 years (SD 20 years). Sixty-eight percent were male, 33% had detectable BAC, and 19% had hazardous drinking behavior. Multivariate analysis identified age (odds ratio [OR] 0.97 per year), male sex (OR 3.1), BAC (OR 1.009 per mg/dL), detectable BAC (OR 3.9), and legal intoxication (OR 7.8) as independent predictors of hazardous drinking behavior. Asian/Pacific Islander ethnicity was a significant negative predictor (OR 0.53) compared with white. Thirty-eight percent of patients with hazardous drinking behavior had no detectable BAC. CONCLUSIONS Younger age, male sex, and higher BAC are early predictors of hazardous drinking behavior in adult trauma patients. Asian/Pacific Islander patients are half as likely to report hazardous drinking behavior compared with white patients. More than one-third of patients with hazardous drinking behavior do not have detectable BAC on admission and are not receiving interventions in centers that screen solely based on BAC.

The natural history of upper extremity deep venous thromboses in critically ill surgical and trauma patients: what is the role of anticoagulation?

BACKGROUND The natural history and optimal treatment of upper extremity (UE) deep venous thromboses (DVTs) remains uncertain as does the clinical significance of catheter-associated (CA) UE DVTs. We sought to analyze predictors of UE DVT resolution and hypothesized that anticoagulation will be associated with quicker UE DVT clot resolution and that CA UE DVTs whose catheters are removed will resolve more often than non-CA UE DVTs. METHODS All patients on the surgical intensive care unit service were prospectively followed from January 2008 to May 2010. A standardized DVT prevention protocol was used and screening bilateral UE and lower extremity duplex examinations were obtained within 48 hours of admission and then weekly. Computed tomography angiography for pulmonary embolism was obtained if clinically indicated. Patients with UE DVT were treated according to attending discretion. Data regarding patient demographics and UE DVT characteristics were recorded: DVT location, catheter association, occlusive status, treatment, and resolution. The primary outcome measure was UE DVT resolution before hospital discharge. Interval decrease in size on the subsequent duplex after UE DVT detection was also noted. UE DVTs without a follow-up duplex were excluded from the final analysis. Univariate and multivariate analyses were used to identify independent predictors of UE DVT resolution. RESULTS There were 201 UE DVTs in 129 patients; 123 DVTs had a follow-up duplex and were included. Fifty-four percent of UEDVTs improved on the next duplex, 60% resolved before discharge, and 2% embolized. The internal jugular was the most common site (52%) and 72% were nonocclusive. Sixty-four percent were CAUEDVTs and line removal was associated with more frequent improvement on the next duplex (55% vs. 17%, p = 0.047, mid-P exact). Sixty-eight percent of UEDVTs were treated with some form of anticoagulation, but this was not associated with improved UE DVT resolution (61% vs. 60%). Independent predictors of clot resolution were location in the arm (odds ratio = 4.1 compared with the internal jugular, p = 0.031) and time from clot detection until final duplex (odds ratio =1.052 per day, p = 0.032). CONCLUSION A majority of UE DVTs are CA, more than half resolve before discharge, and 2% embolize. Anticoagulation does not appear to affect outcomes, but line removal does result in a quicker decrease in clot size.

A comparison of thoracic CT and abdominal CT for the identification of thoracic blunt trauma

BACKGROUND In light of current trends to limit radiation exposure and costs, as well as increased traffic safety, computed tomography (CT) may have decreasing value for evaluating patients with blunt trauma. The authors examined the utility of chest x-ray and abdominal CT for identifying clinically significant thoracic blunt trauma. METHODS In this prospective study, findings on thoracic CT, abdominal CT, and chest x-ray from trauma patients were compared to assess injury prevalence and relevance to treatment outcomes. RESULTS Four hundred forty-four patients were identified, of whom 76% had no findings. Occult findings had significantly lower Injury Severity Scores. All clinically relevant pneumothoraces and most other injuries could be identified without thoracic CT. Two of 3 aortic abnormalities were suspected from chest x-ray. CONCLUSIONS Clinically significant injuries can be identified with abdominal CT and chest x-ray, safely allowing reductions in radiation exposure, hospital stays, and costs by limiting the use of thoracic CT.

National risk factors for blunt cardiac injury: Hemopneumothorax is the strongest predictor

BACKGROUND Blunt cardiac injury (BCI) can occur after chest trauma and may be associated with sternal fracture (SF). We hypothesized that injuries demonstrating a higher transmission of force to the thorax, such as thoracic aortic injury (TAI), would have a higher association with BCI. METHODS We queried the National Trauma Data Bank (NTDB) from 2007-2015 to identify adult blunt trauma patients. RESULTS BCI occurred in 15,976 patients (0.3%). SF had a higher association with BCI (OR = 5.52, CI = 5.32-5.73, p < 0.001) compared to TAI (OR = 4.82, CI = 4.50-5.17, p < 0.001). However, the strongest independent predictor was hemopneumothorax (OR = 9.53, CI = 7.80-11.65, p < 0.001) followed by SF and esophageal injury (OR = 5.47, CI = 4.05-7.40, p < 0.001). CONCLUSION SF after blunt trauma is more strongly associated with BCI compared to TAI. However, hemopneumothorax is the strongest predictor of BCI. We propose all patients presenting after blunt chest trauma with high-risk features including hemopneumothorax, sternal fracture, esophagus injury, and TAI be screened for BCI. SUMMARY Using the National Trauma Data Bank, sternal fracture is more strongly associated with blunt cardiac injury than blunt thoracic aortic injury. However, hemopneumothorax was the strongest predictor.

Risk factors for venous thromboembolism in critically ill nontrauma surgical patients who cannot receive chemical prophylaxis

BACKGROUND We sought to identify independent predictors of venous thromboembolism in critically ill general surgery patients who cannot receive chemical prophylaxis in order to identify those who may benefit from aggressive screening and/or prophylactic inferior vena cava filter placement. METHODS Nontrauma patients in the surgical intensive care unit were prospectively followed for 2 years. Patients who had contraindications to prophylactic anticoagulation and received routine screening duplex examinations were included. Data regarding lower-extremity deep venous thrombosis or pulmonary embolism (PE) rates, past medical history (PMH), surgeries, and transfusions were collected. Logistic regression was used to identify independent predictors of lower-extremity deep venous thrombosis or PE (venous thromboembolism) with a P < .05. RESULTS Data were complete for 204 patients. Twenty (9.8%) patients developed venous thromboembolism. Independent predictors of venous thromboembolism included postoperative blood product requirements (odds ratio = 1.04 per unit), a PMH of PE (OR = 10.1), and a PMH of renal insufficiency (odds ratio = 5.1). CONCLUSIONS Aggressive screening and/or prophylactic inferior vena cava filter may be considered when prophylactic anticoagulation is prohibited in patients with increased postoperative transfusion requirements or a PMH of either PE or renal insufficiency.