Robert A. Cocks

Leukocyte L-selectin is up-regulated after mechanical trauma in adults.

BACKGROUND Infection and multiple organ failure remain the principal causes of late mortality after trauma despite advances in the resuscitation of injured patients. Because a better understanding of postinjury leukocyte trafficking is essential to the development of possible therapeutic measures aimed at preventing these complications, we have performed a study of one factor in the early posttrauma endothelial adhesion behavior of monocytes, lymphocytes, and neutrophils: their cell surface expression of L-selectin (CD62L). We have also studied the plasma levels of soluble L-selectin in these patients. METHODS Two venous blood samples were taken from each of 41 trauma patients at median times of 1 and 20 hours after injury. The study group included 16 patients with major (Injury Severity Score (ISS) > or = 16), 17 with moderate (ISS = 9-15), and 8 with minor (ISS < 9) trauma. Cell surface L-selectin was measured on leukocyte subsets by staining with specific fluorescent-labeled monoclonal antibodies to CD62L and using flow cytometry. Both the percentage of cells expressing the molecule and the mean channel fluorescence were measured. Levels of soluble L-selectin were measured in the plasma, sampled concurrently, by enzyme-linked immunosorbent assay. RESULTS Monocytes, lymphocytes, and neutrophils all showed an early increase in cell surface L-selectin expression as measured by mean channel fluorescence (p < 0.0001, p < 0.001, and p < 0.0001, respectively), and this persisted in later samples taken at a median 20 hours after injury (p < 0.0001,p < 0.0001, and p < 0.01). Only monocytes showed an increased percentage of cells expressing the molecule in the early phase (p < 0.02), and this remained in the later phase (p < 0.001). Monocytes also showed a further significant increase in mean channel fluorescence (p < 0.02) between the two periods. No significant changes in levels of plasma soluble L-selectin were found at either stage. CONCLUSION An increase in the expression of L-selectin on each of three leukocyte populations has been demonstrated in the early phase after trauma. This would tend to promote rolling behavior of leukocytes and increase their contact with the vascular endothelium. There were marked differences in the later responses of the three populations, which may represent differential control of their behavior.

Adrenaline upregulates monocyte L-selectin in vitro

OBJECTIVE Although surface adhesion molecules mediate leucocyte-endothelial interactions at sites of inflammation, relatively little is known of the factors which increase the expression of L-selectin in circulating leucocytes. The expression of leucocyte L-selectin increases during acute stress events such as injury and is temporally related to an early neuroendocrine response. This study investigates whether adrenaline increases the expression of L-selectin on monocytes, neutrophils and lymphocytes in vitro and whether these effects are mediated via beta-adrenoceptors. METHODS A total of 20 ml of blood was withdrawn from 28 healthy volunteers (21 males) with a mean age of 29 years (range 23-67 years). Adrenaline at physiological doses mimicking trauma (0-200 nmol/l) was added to whole blood prior to immunofluorescent staining and analysis by flow cytometry. Propranolol (50 microl of 2 x 10(-5) M) was also added to separate tubes prior to incubation with adrenaline. Saline (40 microl 0.9% solution) was used as a control. Expression is described firstly as percentage of cells expressing L-selectin and secondly as average intensity (mean channel fluorescence, mcf) per cell expressing CD62L. Summary measures were used to analyse the data. RESULTS A significant increase in both the percentage of monocytes expressing L-selectin and mean channel fluorescence of L-selectin was evident with adrenaline in vitro (P < 0.0001). Maximal increases occurred at 100 nmol/l adrenaline when a 9% increase in the percentage of monocytes expressing L-selectin and a 23% increase in mean channel fluorescence were observed. These effects were both blocked by propranolol (P < 0.0001). No significant differences were observed for neutrophils or lymphocytes except for a slight increase in the percent neutrophils expressing L-selectin, and a small decreasing trend in percent lymphocytes expressing L-selectin. CONCLUSIONS Adrenaline upregulates the surface expression of L-selectin on monocytes in vitro, an effect which is partially mediated by beta-adrenoceptors. As monocytes initiate early aspects of the inflammatory response, these findings suggest that beta-blockade may have an inhibitory role for certain aspects of leucocyte trafficking.

Commercial aviation in-flight emergencies and the physician

Commercial aviation in‐flight emergencies are relatively common, so it is likely that a doctor travelling frequently by air will receive a call for help at some stage in their career. These events are stressful, even for experienced physicians. The present paper reviews what is known about the incidence and types of in‐flight emergencies that are likely to be encountered, the international regulations governing medical kits and drugs, and the liability, fitness and indemnity issues facing ‘Good Samaritan’ medical volunteers. The medical and aviation literature was searched, and information was collated from airlines and other sources regarding medical equipment available on board commercial aircraft. Figures for the incidence of significant in‐flight emergencies are approximately 1 per 10–40 000 passengers, with one death occurring per 3–5 million passengers. Medically related diversion of an aircraft following an in‐flight emergency may occur in up to 7–13% of cases, but passenger prescreening, online medical advice and on‐board medical assistance from volunteers reduce this rate. Medical volunteers may find assisting with an in‐flight emergency stressful, but should acknowledge that they play a vital role in successful outcomes. The medico‐legal liability risk is extremely small, and various laws and industry indemnity practices offer additional protection to the volunteer. In addition, cabin crew receive training in a number of emergency skills, including automated defibrillation, and are one of several sources of help available to the medical volunteer, who is not expected to work alone.

Derivation of a prediction rule for post-traumatic acute lung injury

The purpose of this study was to derive an early, highly sensitive and specific prediction rule for the development of post-traumatic acute lung injury (ALI). In a prospective, non-interventional study a convenience sample of 92 adults admitted to the resuscitation room following blunt trauma was studied in order to derive this prediction rule. The study was conducted in the emergency department of a university hospital in the New Territories of Hong Kong. One emergency physician assessed each patient for 25 variables, which might predict post-traumatic ALI, and the primary outcome measure was the presence or absence of ALI 48 h post-injury. Eleven variables associated with ALI were entered into a classification and regression tree (CART) in order to derive models predictive of ALI. Two models were developed and used to derive the decision rule. Acute lung injury was likely if either: (1) the patient had an ISS > 27 and a haematocrit < 0.37, or (2) the patient had a haematocrit < 0.36 and a total leucocyte count > 15. The first guideline had a classification rate of 96.7% (95% confidence interval (CI), 90.8-99.3%), a sensitivity of 100% (CI 65.2-100%) and a specificity of 96.5% (CI 90.0-99.3%). The second guideline had a classification rate of 96.7% (CI 90.8-99.3%), a sensitivity of 85.7% (CI 42.1-99.6%) and a specificity of 97.7% (CI 91.8-99.7%). Practical highly sensitive and specific prediction guidelines for post-traumatic acute lung injury have been derived and now require prospective validation.

Early role of neutrophil l-selectin in posttraumatic acute lung injury

ObjectiveTo investigate whether early numerical and functional changes in circulating neutrophils and expression of neutrophil l-selectin and soluble l-selectin are related to the subsequent development of posttraumatic acute lung injury (ALI), the systemic inflammatory response syndrome, sepsis, and organ failure. DesignProspective study of whole blood and plasma samples to assess numerical and functional changes in circulating neutrophils and in soluble l-selectin. SettingThe emergency department of a university hospital. PatientsA total of 147 patients admitted to the resuscitation room after trauma were compared with 69 control subjects. Ten patients developed ALI. Laboratory AnalysisFlow cytometry of whole blood and ELISA of plasma. ResultsTotal leukocyte and neutrophil counts, expression of L-selectin, and the ratio of neutrophil to plasma L-selectin increased with injury and were highest in those who developed ALI. Soluble L-selectin decreased with injury severity and was lowest in those who developed ALI. ConclusionsEarly changes in the average expression of L-selectin per cell do not correlate with the development of subsequent posttraumatic ALI. However, the development of ALI is related to the total expression of L-selectin in the neutrophil mass, and the most striking association is in those with lower concentrations of plasma L-selectin.

Derivation of a prediction rule for posttraumatic organ failure using plasma DNA and other variables.

Abstract: The early identification of patients at high risk of developing posttraumatic organ failure would allow preventive therapies to be studied. In this study, highly sensitive and specific guidelines for the early prediction of post‐traumatic organ failure (OF) and multiple organ dysfunction syndrome (MODS) using cell‐free (plasma) DNA and other predictors of posttraumatic complications were derived. As plasma DNA increases after injury and may be used to predict acute lung injury (ALI), we hypothesized that in combination with other predictors it would predict the later development of OF and MODS. Eighty‐three patients (69 males; median age, 36 years) were studied as a consequence of major trauma within 3.5 hours of injury (median time to sampling and assessment, 60 min). Plasma DNA was measured using a real‐time, quantitative, polymerase chain reaction assay for the β‐globin gene. OF and MODS occurred in 20/83 (24%) and 9/79 (11%) cases, respectively. At selected cutoff points, the sensitivity of plasma DNA for predicting OF and MODS ranged from 50% to 100%, specificity ranged from 74% to 95%, and the likelihood ratio ranged from 3.89 to 10.50. Other variables studied included serum albumin, creatine kinase, aspartate transaminase, lactate dehydrogenase, leukocyte count, hematocrit, injury severity score, maximal abbreviated injury score, and shock index. Using a classification and regression tree, plasma DNA and aspartate transaminase at optimal cutoffs predicted OF and MODS with an overall correct classification of 93% and 87%, respectively.

Do peripheral blood counts have any prognostic value following trauma

BACKGROUND Both lymphocytosis and lymphopenia have been observed following trauma and each has been claimed to predict mortality. An understanding of the early temporal changes in leucocyte counts may help to explain why such discrepancies have been found. The purpose of this study was to determine the early serial changes in peripheral leucocyte counts following injury. METHODS A whole blood cell counter was used to measure serial total leucocyte, granulocyte, lymphocyte and monocyte counts from 20 patients in the first 3 h following blunt injury. Four to six peripheral blood samples were taken from each subject and grouped into 20 min intervals. RESULTS Granulocytosis, lymphocytosis and monocytosis were evident within 40 min of injury. A biphasic granulocyte and monocyte response was observed in the first 3 h following trauma. Lymphocytes showed a linear resolution towards normal (regression coefficient -0.022; p < 0.01) with some individuals developing a lymphopenia. No correlation with injury severity was observed. CONCLUSION Rapid mobilisation and subsequent redistribution of leucocytes occurs early following injury. Temporal changes will affect any predictive value of circulating leucocytes and studies must be precise with respect to blood sampling time.

Effect of stress hormones on the expression of fibrinogen-binding receptors in platelets

Acute coagulopathy is a common clinical complication after trauma, and contributes to posttraumatic multiple organ failure. The phenomenon may be due to the effect of stress hormones on platelet adhesion molecule expression after trauma. Catecholamine levels correlate with injury severity scores and changes of L-selectin expression on leucocytes, whilst adrenaline (ADR) (epinephrine) alone also activates platelets. This study thus investigates the effects of ADR and noradrenaline (NOR) (norepinephrine) on platelets, at doses similar to those found in the plasma of normal and trauma subjects. Blood was taken from 19 healthy subjects and placed in tubes containing sodium citrate. Anti-platelet-bound fibrinogen monoclonal antibody was used to identify the activated platelets while anti-CD41 was used to identify platelets with and without activation. Five increasing concentrations of ADR and NOR (1, 3, 5, 10, 30 nmol/l) as well as one negative control (0.9% normal saline) and one positive control (10 micromol/l adenosine diphosphate/ADP) were prepared for the stimulation. A whole blood protocol was used in order to minimize any activation artefacts, which might be created by centrifugation. The percentage of platelets expressing fibrinogen receptors increased significantly with ADR and NOR even at the lowest dose (1 nmol/l) and continued to increase in a dose-dependent manner. Although the effect of ADR was greater than NOR in stimulating platelets to express fibrinogen receptors, the average number of fibrinogen receptors on each platelet was constant. ADR and NOR activated platelets to express fibrinogen receptors at doses that are similar to those found in the plasma of trauma patients.

Role of monocyte L-selectin in the development of post-traumatic organ failure

The vascular leucocyte adhesion molecule, L-selectin, plays an important early role in monocyte trafficking at sites of inflammation, a process which leads to the development of inflammatory organ failure. In this prospective observational study, we investigate whether early numerical and functional changes in circulating monocytes, expression of monocyte L-selectin (CD62L) and monocyte:neutrophil L-selectin ratios are related to the subsequent development of post-traumatic organ failure (OF) and multiple organ dysfunction syndrome (MODS). Monocyte counts and cell surface L-selectin were measured by an automated cell counter and flow cytometry, respectively. Of 164 trauma patients admitted to a university emergency department resuscitation room, 64 had multiple injuries, 51 developed OF, 20 developed MODS and 21 died. Early monocyte counts in patients with multiple injuries were lower in those who developed MODS (0.44 x 10(9)/l) compared with those who did not (0.60 x 10(9)/l; P=0.024). Monocyte L-selectin mean channel fluorescence increased with injury severity and was highest in those who developed MODS (P=0.033). In the sub-group of patients with multiple injuries, L-selectin mean channel fluorescence was also greater in those patients who developed MODS compared with patients who did not develop MODS (P=0.042). The monocyte to neutrophil count ratio also decreased with injury severity (P=0.006). Using optimal cut off values for L-selectin mean channel, fluorescence, the positive and negative predictive values for OF was 43.5 and 91.4%, respectively and for MODS it was 25.4 and 92.9%, respectively. Alterations in early circulating monocyte counts and L-selectin expression after injury are related to the development of post-traumatic organ failure and suggest an area in the inflammatory pathway that may be influenced by L-selectin blockade.

Predictors of Flight Diversions and Deaths for In-flight Medical Emergencies in Commercial Aviation

In-flight medical emergencies are clinically challenging and may result in aircraft diversions, which are costly and inconvenient, or in-flight deaths. We provide an updated description of in-flight medical emergencies and systematically examine predictors of medical flight diversions and in-flight deaths.