The aim of this web is to provide stranding responders with all the information required for the successful study of gas embolism in stranded marine mammals.

 

In our experience and in agreement with human forensic science guidelines, describing the distribution and amount of gas are as important as to analyze its composition. In human forensic science, post-mortem computed tomography or other imaging techniques are used as a pre-autopsy step for observation and localization of gas. In stranded marine mammals, many different logistical obstacles and obvious challenges, such as the size of the animal or the transport of the animal from the stranding location to the scanner, limits the use of these techniques. Instead, we have developed a gross gas score index . The vascular locations to be studied in the specific case of cetaceans  are subcutaneous, mesenteric, coronary veins, and the lumbo-caudal venous plexus. This method is inexpensive, simple, and can be used by all stranding networks, any time, any place. It allows for the comparison of gas amount among different individuals of the same species and decomposition code.

 

We strongly recommend integrating the gas score index into the necropsy protocol of each stranding network to ensure that the gas score is evaluated in every stranded animal. This way a baseline for each species can be built and abnormal cases with elevated gas scores identified. As an index, the method is subjective, and such it requires that each stranding network develop its own baseline. To help harmonizing criteria, here you can find a training quiz (coming soon) .

 

To study gas embolism (both, gas score and gas composition) it is paramount performing a very careful dissection, minimizing cutting large blood vessels. It is important to evaluate all vascular locations using the gas score and starting with subcutaneous veins. Once the abdominal and thoracic cavities have been opened, the mesenteric, coronary veins and the lumbo-caudal venous plexus should also be evaluated, photographed, and sampled. No organs should be removed; neither the head should be disarticulated, before the study of gas embolism. Otherwise, the gas score and gas composition results will be compromised and invalidated for publication. Therefore we strongly recommend following this step by step protocol .

 

Within our methodology manuscript  you could find detailed information to carry out the gas analysis. Regarding gas sampling it is important to highlight that:

 

- It is paramount to use the material specified for gas sampling and storage in order to prevent atmospheric air pollution:

  •  Tubes: Glass 5-mL additive-free BD vacutainer ® or 2 mL MONOJECTTM Red Stopper  (Silicone Coated) glass tubes  (ref #8881301116). No other tubes (brands, material, volume, etc. are valid!)
  •  Disposable Insulin syringes: BD Plastipak U-100 insulin  (ref #329651). No other syringes are valid!

- Sample each bubble with a new dispensable insulin syringe and inject it into a new vacutainer® each time. Label the vacutainer® with volume recovered and location of the bubble in addition to the animal ID.

- Sample multiple gas bubbles from different locations, especially within the thoracic cavity (e.g.: coronary veins) as thoracic veins are longer unaltered by decomposition gases.

- Store blank tubes with the samples; minimum of three blanks per animal, five preferably.

- If samples need to be transported in a plane, they should travel within the passenger cabin to prevent dramatic changes in atmospheric pressure that might alter the vacuum tubes, or we can provide you with a resistant housing so samples can be shipped.

-   Time to gas analysis is two weeks maximum

 

Here you can find a one-page protocol  summary which you can plasticize and kept within your necropsy material, as well as a recommended data sheet.

 

We are available for assisting you with the necropsy (pathological study) as well as with the sampling and analysis of gas samples. Contact information: direccion_iusa@ulpgc.es, yara.bernaldo@ulpgc.es, antonio.fernandez@ulpgc.es

 


 References

Bernaldo De Quirós, Y., González-Díaz, Ó., Saavedra, P., Arbelo, M., Sierra, E., Sacchini, S., Jepson, P.D., Mazzariol, S., Di Guardo, G., and Fernández, A. (2011). Methodology for in situ gas sampling, transport and laboratory analysis of gases from stranded cetaceans. Scientific Reports 1, 193.

Bernaldo De Quirós, Y., González-Díaz, Ó., Arbelo, M., Andrada, M., and Fernandez, A. (2012). Protocol for gas sampling and analysis in stranded marine mammals. Protocol exchange.

Bernaldo De Quirós, Y., González-Diaz, O., Arbelo, M., Sierra, E., Sacchini, S., and Fernández, A. (2012). Decompression vs. decomposition: distribution, amount, and gas composition of bubbles in stranded marine mammals. Frontiers in Physiology 3.

Bernaldo De Quirós, Y., González-Díaz, O., Møllerløkken, A., Brubakk, A.O., Hjelde, A., Saavedra, P., and Fernández, A. (2013). Differentiation at autopsy between in vivo gas embolism and putrefaction using gas composition analysis. International Journal of Legal Medicine 127, 437-445.

Bernaldo De Quirós, Y., Seewald, J.S., Sylva, S.P., Greer, B., Niemeyer, M., Bogomolni, A.L., and Moore, M.J. (2013). Compositional discrimination of decompression and decomposition gas bubbles in bycaught seals and dolphins. PLoS One 8, e83994.

Bernaldo De Quiros, Y., Saavedra, P., Mollerlokken, A., Brubakk, A.O., Jorgensen, A., Gonzalez-Diaz, O., Martin-Barrasa, J.L., and Fernandez, A. (2016). Differentiation at necropsy between in vivo gas embolism and putrefaction using a gas score. Res Vet Sci 106, 48-55.