The etiology of pulmonary edema in fresh water near-drowning

Noncardiogenic pulmonary edema in small animals

OBJECTIVE

To review various types of noncardiogenic pulmonary edema (NCPE) in cats and dogs.

ETIOLOGY

NCPE is an abnormal fluid accumulation in the lung interstitium or alveoli that is not caused by cardiogenic causes or fluid overload. It can be due to changes in vascular permeability, hydrostatic pressure in the pulmonary vasculature, or a combination thereof. Possible causes include inflammatory states within the lung or in remote tissues (acute respiratory distress syndrome [ARDS]), airway obstruction (post-obstructive pulmonary edema), neurologic disease such as head trauma or seizures (neurogenic pulmonary edema), electrocution, after re-expansion of a collapsed lung or after drowning.

DIAGNOSIS

Diagnosis of NCPE is generally based on history, physical examination, and diagnostic imaging. Radiographic findings suggestive of NCPE are interstitial to alveolar pulmonary opacities in the absence of signs of left-sided congestive heart failure or fluid overload such as cardiomegaly or congested pulmonary veins. Computed tomography and edema fluid analysis may aid in the diagnosis, while some forms of NCPE require additional findings to reach a diagnosis.

THERAPY

The goal of therapy for all types of NCPE is to preserve tissue oxygenation and reduce the work of breathing. This may be achieved by removing the inciting cause (eg, airway obstruction) and cage rest in mild cases and supplemental oxygen in moderate cases and may require mechanical ventilation in severe cases.

PROGNOSIS

Prognosis is generally good for most causes of veterinary NCPE except for ARDS, although data are scarce for some etiologies of NCPE.

Potential forensic application of receptor for advanced glycation end products (RAGE) and aquaporin 5 (AQP5) as novel biomarkers for diagnosis of drowning

Drowning is the most common cause of unnatural death worldwide. There is no single biomarker to diagnose drowning, so the diagnosis of drowning is one of the most difficult tasks in forensic medicine. Especially, distinguishing a victim of drowning from a body disposed of in water following death remains a problem. The objective of this study was to identify specific biomarkers of drowning compared with other causes of death such as hypoxia and postmortem submersion. The present study investigated the intrapulmonary expression of receptor for advanced glycation end products (RAGE), aquaporin-5 (AQP5), surfactant protein-A (SP-A), interleukin 6 (IL-6) and interleukin 1β (IL-1β) as markers of drowning. In animal experiments, all rats (n = 45) were classified into four groups (drowning, postmortem-submersion, hypoxia and control group). The lungs of experimental animals were analyzed as mRNA expression, immunoblot expression and immunohistochemical staining. qRT-PCR demonstrated increased mRNA expression of RAGE and AQP5 in drowning group compared with that in control, hypoxia and postmortem-submersion group, but not other molecules. Western blotting also showed high expression of RAGE and AQP5 in drowning group, immunostaining of RAGE and AQP5 was highly detected in a linear pattern in type I alveolar epithelial cells, compared with control and postmortem-submersion group. These observations indicate a difference of expression in pulmonary molecular pathology compared with other causes, suggesting RAGE and AQP5 may be useful for differentiation between drowning and postmortem-submersion.

Real-time imaging of mechanically and chemically induced ATP release in human lung fibroblasts

Extracellular adenosine 5'-triphosphate (ATP) acts as an inflammatory mediator of pulmonary fibrosis. We investigated the effects of mechanical and chemical stimuli on ATP release from primary normal human lung fibroblasts. We visualized the ATP release from fibroblasts in real time using a luminescence imaging system while acquiring differential interference contrast cell images with infrared optics. Immediately following a single uniaxial stretch for 1s, ATP was released from a certain population of cells and spread to surrounding spaces. Hypotonic stress, which causes plasma membrane stretching, also induced the ATP release. Compared with the effects of mechanical stretch, ATP-induced release sites were homogeneously distributed. In contrast to the effects of mechanical stimuli, application of platelet-derived growth factor caused ATP release from small numbers of the cells. Our real-time ATP imaging demonstrates that there is a heterogeneous nature of ATP release from lung fibroblasts in response to mechanical and chemical stimuli.

Combat-associated drowning

BACKGROUND

The purpose of this article is to describe the clinical course and outcome of drowning cases related to current US military combat operations.

METHODS

This retrospective case series spans December 2002 to January 2009 of survivors transferred to an echelon IV military trauma center in Europe serving as the primary evacuation hub for ongoing combat operations. Patient demographics and the situational and clinical findings at the initial drowning scene were reviewed. A comprehensive analysis of care as each patient transitioned through the combat theater to the echelon IV trauma center in Europe was performed.

RESULTS

Overall, mortality was 37.5% mortality rate (3 of 8 patients). Advanced modes of respiratory support such as high-frequency ventilation, airway pressure release ventilation, and extracorporeal membrane oxygenation were required in a majority of the cohort (6 of 8 patients). Limited-duration vasopressor infusions (7 of 8 patients) were also required to ensure adequate end-organ perfusion. Glasgow Coma Scale (GCS) scores and the need for cardiopulmonary resuscitation (CPR) at the scene of injury were associated with eventual patient mortality (100% mortality for an initial GCS score of 3 and 75% mortality for on-scene CPR). Survivor long-term morbidity was often related to the sequelae of acute respiratory distress syndrome and hypoxic encephalopathy.

CONCLUSION

Drowning associated with combat operations was associated with severe acute respiratory distress syndrome and cardiovascular shock. GCS score and the need for CPR at the scene of injury were associated with eventual mortality because of anoxic brain injury in all cases.

Systematic review of definitions for drowning incidents

OBJECTIVES

In preparation for the World Congress on Drowning uniform reporting consensus document of drowning incidents we reviewed systematically the medical literature for the terms and definitions used to describe drowning incidents to assess the uniformity of these terms in the medical literature.

METHODS

The search strategy included a literature search of PubMed, MEDLINE and the Cochrane Database from 1966 to April 2002, as well as a review of reference lists of identified studies and a hand search of relevant textbooks and reference works. Search terms used included drowning, near-drowning, submersion, immersion, suffocation, asphyxiation, water injuries, and aspiration. Any article with drowning as a primary focus and containing a definition of drowning was included. Study designs included experimental studies, observational studies, case control studies, reviews, letters, and editorials.

RESULTS

The search identified approximately 6000 articles. Of these 650 were reviewed and 43 articles addressing the definition of drowning were identified. We found a total of 33 different definitions to describe drowning incidents, 20 for drowning and 13 for near-drowning; along with another 13 related terms. There were at least 20 different outcome measures for drowning incidents reported.

CONCLUSIONS

A review of existing drowning literature demonstrates a lack of a standard definition of drowning and a lack of agreement on measures of outcome. This variability in definitions and outcomes makes it very difficult to assess and analyze studies both individually and as a whole and draw conclusions that will influence practice. These objective findings support the need for the drowning Utstein focus on one definition of drowning and validated measures of functional and neurological outcome.

Possible factors contributing to the postmortem lung weight in fire fatalities

The aim of the present study was to examine the factors that contribute to the postmortem lung weight in acute fire fatalities (n=149) including those with lower (<60%) and higher (>60%) blood carboxyhemoglobin (COHb) levels (n=94 and 55, respectively). The control groups consisted of acute myocardial infarction/ischemia (AMI, n=99) and mechanical asphyxiation (n=85). For all cases (n=333), the lung and heart weights were independent of the postmortem time (4.5-72 h) and charring of the body. The combined weight of both lobes of the lung showed a significant gender difference (males>females, P<0.001), negative regression with respect to age (R=0.167, P<0.01) and positive regression with respect to heart weight (R=0.316, P<0.001). The gender difference was also significant for each cause of death even after being corrected using body height measurements. When the lung-heart weight ratio was estimated to diminish the influence of possible cardiogenic factors, the gender difference was insignificant for each cause of death among the non-elderly (<60 years of age). However, for elderly fire fatalities (>60 years of age), there was a gender difference (males>females) for the lower COHb group (P<0.05) and higher COHb group (P<0.001). A significant age-dependent difference (non-elderly>elderly) in the lung-heart weight ratio was observed for fire fatalities with a lower COHb and AMI among males and for fire fatalities with a higher COHb among females. Such gender- and/or age-dependent influences were not significant for fatal mechanical asphyxiation. These findings suggest that a person's heart weight may be a possible contributory factor to an increase in the lung weight in acute death, and that gender- and/or age-dependent susceptibilities may be additional factors that contribute to fire fatalities and AMI. In addition, elderly females appear to be most susceptible among fire casualties, and extreme cardiomegaly may also be a potential fatal risk factor.

Pleural effusion in bodies recovered from water

Both in saltwater and freshwater drowning cases, a common autopsy sign is pleural effusion. However, the factors that determine the amount of pleural effusion have not been well established. An attempt was therefore made to correlate the amount of pleural fluid in bodies recovered from water with several parameters registered on the judicial files as well as autopsy findings from the years 1994-1998. The number of cases with pleural fluid increase was found to be very high in saltwater drowning (P<0.001). But, when the freshwater and saltwater drowning cases with pleural fluid increase were compared according to pleural fluid amount, no significant difference was detected (521+/-340 and 768+/-536 ml, respectively). Although there was a positive correlation between the decomposition degree and the fluid in the pleural cavity, a relative decrease was detected in the amount of effusion contrary to the expectations in cases of extreme decomposition. Pleural fluid amount provides significant data about the type of water and the cause of death in early postmortem interval. And there is a link between the time spent in water and the amount of pleural effusion. With the advance of the postmortem interval, decomposition level and the duration of immersion should be taken into account in differential diagnosis.

Drowning and near-drowning

Water immersion is a frequent cause of accidental death and hospital admission. This article outlines the pathogenesis and principles of treatment. Drowning is defined as death by asphyxia due to submersion in a liquid medium. Near-drowning is defined as immediate survival after asphyxia due to submersion.