The microcirculation: linking trauma and coagulopathy

General Medical Emergencies in Athletes

This article focuses on the management of the most common on-field medical emergencies. As with any discipline in medicine, a well-defined plan and systematic approach is the cornerstone of quality health care delivery. In addition, the team-based collaboration is necessary for the safety of the athlete and the success of the treatment plan.

"Blood failure" time to view blood as an organ: how oxygen debt contributes to blood failure and its implications for remote damage control resuscitation

Hemorrhagic shock is both a local and systemic disorder. In the context of systemic effects, blood loss may lead to levels of reduced oxygen delivery (DO2 ) sufficient to cause tissue ischemia. Similar to other physiologic debts such as sleep, it is not possible to incur a significant oxygen debt and suffer no consequences for lack of timely repayment. While the linkage between oxygen debt and traditional organ failure (renal, hepatic, lung, and circulation) has been long recognized, we should consider failure in two additional linked and very dynamic organ systems, the endothelium and blood. These systems are very sensitive to oxygen debt and at risk for failing, having further implications on all other organ systems. The degree of damage to the endothelium is largely modulated by the degree of oxygen debt. Thus hypoperfusion is believed to begin a cascade of events leading to acute traumatic coagulopathy (ATC). This combination of oxygen debt driven endothelial damage and ATC might be considered collectively as "blood failure" due to the highly connected networks between these drivers. This article presents the implications of oxygen debt for remote damage control resuscitation strategies, such as permissive hypotension and hemostatic resuscitation. We review the impact of whole blood resuscitation and red blood cell efficacy in mitigation of oxygen debt. At last, this article recognizes the need for simple and durable, lightweight equipment that can detect the adequacy of tissue DO2 and thus patient needs for resuscitative care. Point-of-care lactate measuring may be a predictive tool for identifying high-risk trauma patients and occult shock because it provides information beyond that of vital signs and mechanism of injury as it may help predict the level of oxygen debt accumulation and need for resuscitation. Serial measurements may also be valuable as a tool in guiding resuscitative efforts.

Systemic and microcirculatory effects of blood transfusion in experimental hemorrhagic shock

Background

The microvascular reperfusion injury after retransfusion has not been completely characterized. Specifically, the question of heterogeneity among different microvascular beds needs to be addressed. In addition, the identification of anaerobic metabolism is elusive. The venoarterial PCO₂ to arteriovenous oxygen content difference ratio (P_v-aCO₂/C_a-vO₂) might be a surrogate for respiratory quotient, but this has not been validated. Therefore, our goal was to characterize sublingual and intestinal (mucosal and serosal) microvascular injury after blood resuscitation in hemorrhagic shock and its relation with O₂ and CO₂ metabolism.

Methods

Anesthetized and mechanically ventilated sheep were assigned to stepwise bleeding and blood retransfusion (n = 10) and sham (n = 7) groups. We performed analysis of expired gases, arterial and mixed venous blood gases, and intestinal and sublingual videomicroscopy.

Results

In the bleeding group during the last step of hemorrhage, and compared to the sham group, there were decreases in oxygen consumption (3.7 [2.8–4.6] vs. 6.8 [5.8–8.0] mL min⁻¹ kg⁻¹, P < 0.001) and increases in respiratory quotient (0.96 [0.91–1.06] vs. 0.72 [0.69–0.77], P < 0.001). Retransfusion normalized these variables. The P_v-aCO₂/C_a-vO₂ increased in the last step of bleeding (2.4 [2.0–2.8] vs. 1.1 [1.0–1.3], P < 0.001) and remained elevated after retransfusion, compared to the sham group (1.8 [1.5–2.0] vs. 1.1 [0.9–1.3], P < 0.001). P_v-aCO₂/C_a-vO₂ had a weak correlation with respiratory quotient (Spearman R = 0.42, P < 0.001). All the intestinal and sublingual microcirculatory variables were affected during hemorrhage and improved after retransfusion. The recovery was only complete for intestinal red blood cell velocity and sublingual total and perfused vascular densities.

Conclusions

Although there were some minor differences, intestinal and sublingual microcirculation behaved similarly. Therefore, sublingual mucosa might be an adequate window to track intestinal microvascular reperfusion injury. Additionally, P_v-aCO₂/C_a-vO₂ was poorly correlated with respiratory quotient, and its physiologic behavior was different. Thus, it might be a misleading surrogate for anaerobic metabolism.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-017-0136-3) contains supplementary material, which is available to authorized users.

Assessment of the relationships among coagulopathy, hyperfibrinolysis, plasma lactate, and protein C in dogs with spontaneous hemoperitoneum

OBJECTIVE

To relate coagulation and fibrinolysis derangements to shock severity as reflected by plasma lactate concentrations in dogs with spontaneous hemoperitoneum (SHP) and determine the impact on transfusions.

DESIGN

Prospective, observational, case-control study.

SETTING

Three veterinary teaching hospitals.

ANIMALS

Twenty-eight client-owned dogs with SHP and 28 breed- and age-matched control dogs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Blood samples for platelet counts, coagulation, and anticoagulant assays (prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin, and protein C, thromboelastography [TEG]), fibrinolysis testing (d-dimer and TEG lysis parameters with and without the addition of 50 U/mL of tissue plasminogen activator [TEG LY30 measured with the addition of 50 U/mL of tPA to the blood sample, LY3050 and TEG LY60 measured with the addition of 50 U/mL of tPA to the blood sample, LY6050 ; LY30 and LY60]), and plasma lactate as an indicator of severity of shock were collected from SHP dogs at the time of diagnosis. SHP dogs were hypocoagulable (prolonged prothrombin time and activated partial thromboplastin time, decreased TEG maximum amplitude) and hyperfibrinolytic (increased LY3050 and TEG LY6050 ) compared to controls. The severity of hypocoagulability was related to protein C activity, while the severity of hyperfibrinolysis was related to plasma lactate concentration. Among the 18 dogs discharged from the hospital, LY3050 was significantly associated with the dose of fresh frozen plasma administered, but none of the parameters were associated with the dose of red blood cells administered.

CONCLUSIONS

Dogs with SHP have evidence of hypocoagulability, protein C deficiency, and hyperfibrinolysis. Parameters of hyperfibrinolysis were related to plasma lactate concentrations and volume of plasma transfused during hospitalization. These derangements resemble those found in people with acute coagulopathy of trauma and shock, and activation of protein C may be a common feature to both syndromes.

A novel severity scoring system for dogs with heatstroke

OBJECTIVE

To develop a statistically-derived scoring system that can aid in severity assessment and outcome prediction for dogs with heatstroke.

DESIGN

Retrospective study.

SETTING

Veterinary teaching hospital.

ANIMALS

One hundred twenty-six client-owned dogs diagnosed with heatstroke.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Logistic regression analysis was performed to identify clinicopathologic variables, available in the first 24 hours of hospitalization, which were associated with outcome (P ≤ 0.1). These were subjected to further analyses. In Model A, continuous variables were divided into quartiles, and logistic regression was performed to yield quartile-specific odds ratios (ORs) for the outcome. Model A was developed, assigning weighted values to each quartile, based on its corresponding OR for the outcome. An individual predictive score was calculated for each dog by summating all weighted values. Model B was a multivariable logistic regression model. Receiver operator characteristic (ROC) analyses were performed to assess models' performance and to calculate sensitivity, specificity, and optimal cutoff points. The overall mortality rate was 53%. The total predictive score (Model A) was negatively and significantly (P < 0.001) associated with probability of survival. The areas under the ROC curve for Models A and B were 0.92 and 0.86, respectively. The optimal cutoff score for Model A was 35.0, corresponding to sensitivity of 93% and specificity of 86%, correctly classifying 90% of the cases.

CONCLUSIONS AND CLINICAL RELEVANCE

The proposed models are applicable, allowing objective assessment of the severity and prognosis of heatstroke in dogs; however, they should be validated further in an independent cohort, and used cautiously for assessment of individual cases.

Plasma colloid osmotic pressure is an early indicator of injury and hemorrhagic shock

OBJECTIVE

Hemorrhagic shock is the leading cause of traumatic deaths; many could be potentially prevented with appropriate resuscitation. However, to initiate resuscitation, one must identify patients with hemorrhagic shock early. In this article, we determined the associations between plasma colloid osmotic pressure (COP) and clinical outcomes in severely injured trauma patients.

METHODS

Plasma samples were collected from 104 trauma patients upon admission to the emergency department and 10 healthy volunteers to serve as control subjects. Plasma osmolality, COP, and serum protein were measured and correlated to clinical data. Thrombelastography and impedance aggregometry were performed to assess coagulopathy. Commercial enzyme-linked immunosorbent assays were used to quantify syndecan 1.

RESULTS

Plasma COP was significantly reduced in trauma patients compared to control subjects 17.7 ± 2.6 vs. 20.7 ± 2.1 mmHg (P < 0.05) and strongly correlated to serum protein values (R = 0.7). We divided our cohort into low (COP ≤16.5 mmHg) and normal (COP >16.5 mmHg) subgroups, illustrating significantly higher Injury Severity Score scores in patients with low COP (21 vs. 10, P = 0.007), despite no differences in vital signs. Patients with low COP received more red blood cells, plasma, and platelets (4 vs. 0 total units, P = 0.0005) within 24 h of admission. Syndecan 1 levels were significantly higher (184 vs. 52 ng/mL, P = 0.027) in patients with low COP.

CONCLUSIONS

Reduced plasma COP and serum protein in trauma patients are indicative of injury severity. In the absence of significant alterations in vital signs, plasma COP levels were associated with increased requirements for blood products and increased syndecan 1 shedding. We believe that plasma COP provides new insight in guiding resuscitation.

Volume therapy in trauma and neurotrauma

Volume therapy in trauma should be directed at the restitution of disordered physiology including volume replacement to re-establishment of tissue perfusion, correction of coagulation deficits and avoidance of fluid overload. Recent literature has emphasised the importance of damage control resuscitation, focussing on the restoration of normal coagulation through increased use of blood products including fresh frozen plasma, platelets and cryoprecipitate. However, once these targets have been met, and in patients not in need of damage control resuscitation, clear fluid volume replacement remains essential. Such volume therapy should include a balance of crystalloids and colloids. Pre-hospital resuscitation should be limited to that required to sustain a palpable radial artery and adequate mentation. Neurotrauma patients require special consideration in both pre-hospital and in-hospital management.