Bonny J. Baron

Central venous blood oxygen saturation: an early, accurate measurement of volume during hemorrhage.

Accurate and relatively simple monitoring is essential in managing patients with multiple injuries, and becomes particularly important when there is substantial occult blood loss. Tachycardia, said to occur following a 15% blood loss, is generally regarded as the first reliable sign of hemorrhage. However, heart rate is a nonspecific parameter which is affected by factors other than changing intravascular volume. The purpose of this study was to evaluate available means of monitoring volume status and to identify the parameter which is the earliest and most reliable indication of blood loss. Sixteen mongrel dogs were anesthetized and bled by increments of 3% of their total blood volume until the onset of sustained hypotension or a 25% blood loss. All dogs were monitored with a Swan-Ganz catheter and an arterial line. Vital signs, full hemodynamic parameters, and arterial and mixed venous blood gases were measured after each 3% blood loss. Statistical analysis of the data demonstrated that only Cardiac Index and Mixed Venous Oxygen Saturation showed linearity as function of measure blood loss. Linear regression analysis generated r values that ranged from 0.85-0.99 with a mean of 0.95 for Mixed Venous Oxygen Saturation; r values for Cardiac Index ranged from 0.39-0.98 with a mean of 0.85. Furthermore, all dogs had increased tissue oxygen extraction after 3-6% blood loss. Because Central Venous Blood Oxygen Saturation mirrors Mixed Venous Oxygen Saturation and is easily and rapidly measured, we extended our study by repeating all of the previously measured parameters, with the addition of CVP blood gases in an unanesthetized animal model.(ABSTRACT TRUNCATED AT 250 WORDS)

ACUTE BLOOD LOSS

Acute blood loss is a common, but often challenging, problem facing emergency physicians. Inadequate or delay in treatment can lead to morbidity or mortality. Standard classifications to quantify blood loss, as well as vital signs alone, are inadequate for guiding therapy. Mechanism of injury, base deficit and blood lactate, central venous oxygen saturation, and oxygen transport parameters should all play a role in deciding the need for further diagnostic studies and resuscitation. Extreme care must be taken to evaluate and resuscitate those with decreased physiologic reserve adequately, such as the elderly. Once bleeding has been identified, expeditious control of bleeding should be accomplished, either operatively or angiographically. Care must be individualized, but adherence to these general guidelines will improve outcome.

Nonoperative management of blunt abdominal trauma: The role of sequential diagnostic peritoneal lavage, computed tomography, and angiography

STUDY OBJECTIVE To determine the usefulness of sequential nonoperative diagnostic studies in the evaluation and treatment of stable patients after blunt abdominal trauma. DESIGN AND SETTING Retrospective review of a prospective treatment plan in a large urban Level I trauma center. PARTICIPANTS Fifty-two patients deemed stable after initial evaluation following blunt abdominal trauma. INTERVENTIONS Patients with a positive diagnostic peritoneal lavage for red blood cells underwent abdominal computed tomography (CT) scanning. If CT demonstrated a visceral injury, it was followed by diagnostic angiography. Attempts were made to treat on-going bleeding by transcatheter embolization. RESULTS Fifteen patients had negative CT scans and were successfully observed. In the other 37 patients, CT identified 17 liver, 16 splenic, and eight kidney injuries; eight extra-peritoneal bleeds; and one mesenteric hematoma. Six of these patients were observed. Thirty underwent diagnostic angiograms. Twelve had no active bleeding, and all were observed successfully. Seventeen underwent successful embolization of the bleeding site(s). One had injuries not controllable by embolization and required exploration. Six patients required laparotomy later in their course, but none had intra-abdominal bleeding or a missed intestinal injury. Despite being performed after diagnostic peritoneal lavage, CT missed only two injuries. There was one main complication, delayed recognition of a diaphragmatic injury. Three patients died, two from multiple organ failure and one from a pulmonary embolus; none was believed to be related to this technique. With our algorithm, 45 patients (86%) were spared laparotomy. CONCLUSION Diagnostic peritoneal lavage and CT are complementary when evaluating blunt abdominal trauma. Diagnostic peritoneal lavage is an effective screening tool. CT may be reserved for stable patients with a positive diagnostic peritoneal lavage to specify the organs injured. Bleeding often may be treated by embolization, limiting the rate of surgery.

Does Ethanol Explain the Acidosis Commonly Seen in Ethanol-Intoxicated Patients?

Objective. Emergency physicians frequently treat ethanol-intoxicated trauma patients. In patients with apparently minor injuries, the presence of metabolic acidosis is often attributed to serum ethanol. We tested whether there is justification for the bias that ethanol reliably explains the acidosis commonly seen in alcohol-intoxicated patients. Methods. Prospective, observational. Inclusion criteria: Ethanol-intoxicated patients admitted to the emergency department (ED) following significant trauma mechanisms, in whom diagnostic evaluation revealed only minor injury. Exclusion criteria: Major trauma (blood transfusions, drop in Hct > 10 points over 24 h, or Injury Severity Score [ISS] > 5) or positive urine toxicology screen. Definitions: Ethanol Intoxication: (Blood Alcohol Level (BAL) ≥ 80 mg/dl), Acidosis: BD ≤ − 3.0 mMol/L; Lactic Acidosis (LAC > 2.2 mMol/L). Data were reported as mean ± SD. Data were compared by t-tests or Fishers exact test as appropriate (α = 0.05, 2 tails) and correlations by Pearson correlation coefficient. Results. 192 patients were studied (84% male) with a mean age of 31.7 ± 15.6 years. Acidosis was observed in 19.3% (CI 95%, 14.5% to 25.0%) of all study patients. We observed significant (p < 0.001) difference in prevalence of acidosis in ethanol intoxicated (42%) compared to nonintoxicated (1%) patients. Comparing the two study groups, patients with ethanol intoxication had lower BD ( − 2.24 ± 2.74 vs. − 0.05 ± 2.35, p < 0.001) and higher LAC (2.69 ± 1.48 vs. 2.00 ± 1.78, p = 0.02). However, ethanol levels did not correlate significantly with BD (p = 0.50) or LAC (p = 0.14). Conclusion. Ethanol intoxication is associated with acidosis, which does not correlate with BD or LAC. The complexity of pathogenesis of acidosis in ethanol intoxication justifies further diagnostic evaluation of these patients in order to rule out other causes of acidosis.

Utility of Base Deficit for Identifying Major Injury in Elder Trauma Patients

BACKGROUND Early identification of serious injuries is especially important in elders. Base deficit (BD) is an indicator of serious injury in trauma patients. There are limited data to support the utility of BD in elders who have sustained trauma. OBJECTIVES To assess the diagnostic performance of BD in identifying major injury in elders. METHODS This was a prospective, observational, preliminary study. Elder (age 65 years and older) patients with significant injury mechanisms had BD analyzed during initial emergency department resuscitation. Major injury was defined by an Injury Severity Score > or =15, a decrease in hematocrit of more than ten points, or blood transfusion. Patients were stratified into two groups of minor and major injuries. Data were reported as means (+/-SD). Receiver operating characteristic (ROC) curves tested the diagnostic ability of BD to identify major injury. RESULTS Seventy-four patients were enrolled; the mean (+/-SD) age was 75 (+/-7) years, and 57% were male. Twenty-four patients (32%) had major injury. The mean (+/-SD) for BD in the major injury group (-2.9 [+/-6] mmol/L) was significantly different from that in the minor injury group (0.8 [+/-3] mmol/L), with a mean difference of 3.7 (95% confidence interval = 1.4 to 5.9). ROC curves revealed that BD was able to identify major injury in elder patients (area under the ROC curve, 0.72; 95% confidence interval = 0.60 to 0.85; p = 0.0003). CONCLUSIONS The preliminary data from this study indicate that in trauma patients aged 65 years and older, increased BD at emergency department arrival can predict life-threatening injury.

Effects of traditional versus delayed resuscitation on serum lactate and base deficit

OBJECTIVE To test the hypothesis that delayed resuscitation of hemorrhagic shock produces a less severe shock insult than traditional resuscitation, characterized by repeated episodes of alternating hypotension and normotension. METHODS Female pigs were divided into three groups. Sham operated controls (C) (n = 4), sustained hypotension (SS) (n = 6), and hypotension with multiple cycles of shock and resuscitation (SR) (n = 6). SS and SR animals were bled to a mean arterial pressure (MAP) of 50 mmHg. SS animals were maintained at an MAP of 50 mmHg for 65 min and then resuscitated to baseline blood pressure with normal saline and shed blood. SR animals were initially bled and maintained at an MAP of 50 mmHg for 35 min, resuscitated to baseline BP, and subsequently bled and resuscitated twice more. The total period of shock was the same in both SS and SR. RESULTS Following hemorrhage, there was a significant increase in lactate and base deficit in SS as compared to C and SR. CONCLUSION Delayed resuscitation produces a more profound shock insult than traditional resuscitation.

The Hemodynamic Effects of Cocaine During Acute Controlled Hemorrhage in Conscious Rats

Background: Cocaine is often associated with trauma; however, little is known about how its use alters the response to blood loss. The effect of cocaine on hemodynamics following acute hemorrhage was studied in a rat model. Methods: Following baseline measurements, rats were administered either intravenous cocaine, or saline as a control. Both groups then underwent arterial catheter hemorrhage of 30% of total blood volume. Outcome variables include blood pressure, heart rate, hematocrit, pH, Pco2, Po2, and serum bicarbonate. Results: Following hemorrhage, blood pressure decreased in both groups but the hypotension was significantly greater in the saline group than the intravenous cocaine group at 0 and 5 minutes posthemorrhage. Heart rate was increased significantly for the intravenous cocaine group compared to the saline group starting at 15 minutes postcocaine and lasting for the next 25 minutes. No difference was noted for hematocrit, pH, Po2, or serum bicarbonate. Conclusion: Although transient, cocaine blunted the hypotensive response to acute controlled hemorrhage and resulted in tachycardia.

The prognostic role of non-critical lactate levels for in-hospital survival time among ED patients with sepsis☆☆☆

OBJECTIVE This study describes emergency department (ED) sepsis patients with non-critical serum venous lactate (LAC) levels (LAC <4.0 mmol/L) who suffered in-hospital mortality and examines LAC in relation to survival times. METHODS An ED based retrospective cohort study accrued September 2010 to August 2014. Inclusion criteria were ED admission, LAC sampling, >2 systemic inflammatory response syndrome criteria with an infectious source (sepsis), and in-hospital mortality. Kaplan-Meier curves were used for survival estimates. An a priori sub-group analysis for patients with repeat LAC within 6 hours of initial sampling was undertaken. The primary outcome was time to in-hospital death evaluated using rank-sum tests and regression models. RESULTS One hundred ninety-seven patients met inclusion criteria. Pulmonary infections were the most common (44%) and median LAC was 1.9 mmol/L (1.5, 2.5). Thirteen patients (7%) died within 24 hours and 79% by ≤28 days. Median survival was 11 days (95% CI, 8.0-13). Sixty-two patients had repeat LAC sampling with 14 (23%) and 48 (77%) having decreasing increasing levels, respectively. No significant differences were observed in treatment requirements between the LAC subgroups. Among patients with decreasing LAC, median survival was 24 days (95% CI, 5-32). For patients with increasing LAC median survival was significantly shorter (7 days; 95% CI, 4-11, P = .04). Patients with increasing LAC had a non-significant trend toward reduced survival (HR = 1.6 95% CI, 0.90-3.0, P = .10). CONCLUSIONS In septic ED patients experiencing in-hospital death, non-critical serum venous lactate may be utilized as a risk-stratifying tool for early mortality, while increasing LAC levels may identify those in danger of more rapid deterioration.

The effect of pregnancy on the response to blood loss in a rat model.

STUDY OBJECTIVES A commonly held belief is that the blunted hemodynamic response to hemorrhage observed in pregnant women is secondary to expanded blood volume. In addition to increased blood volume, pregnancy is also a vasodilated state. Vasodilatation may have deleterious effects on the response to hemorrhage by inhibiting central blood shunting after blood loss. How these conflicting variables of increased blood volume and vasodilatation integrate into a whole body model of maternal hemorrhagic shock has yet to be studied in a controlled experiment. We tested the null hypothesis that there would be no difference in the hemodynamic and metabolic responses to hemorrhage between pregnant (PRG) and non-pregnant (NPRG) rats. METHODS Twenty-four adult female Sprague-Dawley rats (12 PRG and 12 NPRG) were anesthetized with Althesin via the intraperitoneal route. Femoral arteries were cannulated by cut-down. Twelve (six PRG and six NPRG) rats underwent controlled catheter hemorrhage of 25% of their total blood volume. Twelve rats (six PRG and six NPRG) served as non-hemorrhage controls. Mean arterial pressure (MAP) and base excess (BE) were measured pre-hemorrhage and then every 15 min post-hemorrhage for the next 90 min. Data were reported as mean+/-standard error of the mean (S.E.M.) over the 90-min post-hemorrhage observation period. Group comparisons were analyzed by ANOVA with repeated values post-hoc by Bonferroni. Statistical significance was defined by an alpha=0.05. RESULTS PRG and NPRG rats were evenly matched for MAP (P=0.788) and BE (P=0.146) pre-hemorrhage. Post-hemorrhage there were no mortalities in either group. Post-hemorrhage both the PRG and NPRG groups experienced significant (P=0.011) drops in systolic and diastolic blood pressures as compared to their non-hemorrhage controls. Post-hemorrhage there was no significant (P=0.43) difference in MAP between the PRG (89+/-2 mmHg) and NPRG (80+/-2 mmHg) rats. BE also dropped significantly within both PRG (P=0.004) and NPRG (P=0.001) groups post-hemorrhage. No significant (P=0.672) difference was noted in BE between PRG and NPRG groups post-hemorrhage -6.1+/-0.3 mEq/l and -6.9+/-0.4 mEq/l, respectively. CONCLUSION After a controlled hemorrhage of 25% of total blood volume we found no significant differences in MAP and BE between pregnant and non-pregnant rats. Pregnancy does not affect the response to hemorrhage.

Successful Thrombolysis of Massive Pulmonary Embolism

A 52-year-old man with a medical history significant only for hypertension presented to the emergency department (ED) after a syncopal episode. He was walking to work and experienced the sudden onset of severe chest pain followed by a syncopal episode, during which he sustained minor head trauma after falling to the ground. He awoke shortly thereafter with intense back pain and arrived in the ED in severe distress with the following vital signs: blood pressure 73 ⁄ 45 mm Hg, pulse 120 beats ⁄ min, respirations 38 breaths ⁄ min, temperature 99.0 F, and an oxygen saturation of 82% on 100% oxygen delivered via face mask. He was diaphoretic and anxious, his lungs were clear, and his exam was otherwise remarkable only for abrasions to his face, a small left lip laceration, and a moderate occipital scalp hematoma. After intravenous access was obtained, the patient was intubated for severe hypoxemia and agitation. During the initial stabilization and assessment, the treating emergency physician performed a bedside cardiac ultrasound using a 5–1 MHz phased array transducer (SonoSite MTurbo, Bothell WA). This demonstrated marked right ventricular enlargement with severely impaired right ventricular systolic function and preservation of right apical systolic function (McConnell’s sign, Video Clip S1). The patient’s condition then deteriorated quickly into pulseless electrical activity, with return of spontaneous circulation after chest compressions and one dose of intravenous epinephrine. Suspicious of massive pulmonary embolism, a limited compression ultrasound of the lower extremities was performed using a 10–5 MHz linear transducer. This demonstrated a noncompressible right popliteal vein with visible echogenic thrombus within the vein. (Figure 1, Video Clip S2). The patient experienced two subsequent cardiac arrests, with return of spontaneous circulation within 2 minutes of each arrest. Despite the evidence of head trauma, the patient was treated with a 2-hour infusion of 100 mg of tissue plasminogen activator given the high suspicion for massive pulmonary embolism with severe hypotension and multiple cardiac arrests. A dopamine infusion was initiated and the patient was admitted to the intensive care unit in critical condition. The emergency physician performed a repeat bedside echocardiogram with the intensivists on hospital day 2 (Video Clip S3), which demonstrated normal right and left ventricular function. A comprehensive echocardiogram by the cardiology department the following day confirmed these findings. The patient was extubated on hospital day 3 and was discharged from the hospital neurologically intact and with no cardiorespiratory symptoms on hospital day 6.