Kemp's ridley turtle (Lepidochelys kempii) is the smallest and rarest species of sea turtle. It is listed as critically endangered by the World Conservation Union and as endangered by the US Endangered Species Act.1 Adult Kemp's ridley turtles are usually found in the Gulf of Mexico, although juveniles of this species commonly travel to the northeastern coast of the United States to feed during the summer.2,3 Juveniles leave these summer foraging grounds in autumn when the water temperature begins to decrease. Turtles that fail to migrate to warmer waters may become cold-stunned at water temperatures < 10°C (50°F).4–7 Cold-stunned juvenile Kemp's ridley turtles are often found stranded on beaches of New York and Massachusetts from October through December of each year.4–7 Such strandings are thought to be caused by a combination of geographic, oceanographic, and meteorologic conditions.6
In Massachusetts, cold-stunned juvenile Kemp's ridley turtles that are found alive are recovered by a network of volunteers and staff of the Massachusetts Audubon Society and transported to the hospital at the New England Aquarium, Boston, for medical care and long-term rehabilitation. Details of medical management of cold-stunned turtles have been previously described.8 Briefly, turtles are gradually warmed over several days and treated for dehydration, acid-base and electrolyte derangements, cardiorespiratory depression, and concurrent pathological conditions such as pneumonia or traumatic injuries.8 During the first few days of hospitalization, treatments are selected on the basis of physical examination, clinicopathologic, and radiographic findings. These treatments often include mechanical ventilation; administration of fluids that may contain additional potassium, calcium, dextrose, and bicarbonate; and administration of atropine, doxapram, and antimicrobials.8 Results of hematologic, blood biochemical, and plasma biochemical analyses in cold-stunned Kemp's ridley turtles have been described.9–12
Abnormalities in blood gas, pH, lactate, and electrolyte values have been extensively evaluated in domestic animals, and results of these analyses aid clinicians in the determination of prognosis and selection of proper treatments such as mechanical ventilation and administration of fluids.13,14 Blood gas and pH data for Kemp's ridley turtles that survived cold stunning were recently described9; however, to the authors' knowledge, similar values have not been reported for turtles that did not survive cold stunning. The purpose of the study reported here was to assess values of selected clinicopathologic variables, including blood gas and pH values, at the time of hospital admission (day 1) for cold-stunned Kemp's ridley turtles that died during the first 3 days of hospitalization (nonsurvivors) and turtles that survived (survivors) and to determine the percentage change of each variable from day 1 to day of death (nonsurvivors) or to day 2 or 3 of hospitalization (survivors).
Materials and Methods
Case selection—Medical records of all live, cold-stunned Kemp's ridley turtles that were hospitalized at the New England Aquarium from October 2005 through December 2009 were reviewed. Turtles were included in the nonsurvivor group if they died of natural causes within the first 3 days of hospitalization. For each nonsurvivor, a successfully rehabilitated turtle that had been hospitalized closest in time to the nonsurvivor (within a maximum of ± 2 days) was selected for inclusion in a comparison survivor group. This method was chosen to maximize the likelihood that survivors and nonsurvivors had been exposed to similar environmental (ie, weather and oceanographic) conditions prior to hospitalization.
Medical records review—For each patient, information obtained from the medical records included date of admission to the hospital (day 1); weight, straight carapace length, and cloacal temperature at the time of admission; environmental temperature at which the turtle was maintained; outcome of the first 3 days of hospitalization (survival or death); and date of death (ie, day of hospitalization) for nonsurvivors. Results of Hct and blood gas, acid-base, and blood biochemical analyses determined on the first day of hospitalization (day 1) and day of death for nonsurvivors and on corresponding days of hospitalization for matched survivors were recorded. Variables of interest included blood pH, Pco2, Po2, Hct, anion gap, osmolality, and iCa, iMg, sodium, potassium, chloride, glucose, lactate, bicarbonate, and BUN concentrations.
Procedures—Rehabilitation of Kemp's ridley turtles at the New England Aquarium was conducted with authorization of the US Department of the Interior Fish and Wildlife Service and the US Department of Commerce National Marine Fisheries Service. For each turtle, blood sample collections were performed by use of a standard method during the period of interest in this study. For each sample, blood was collected from an external jugular vein into a 1- or 3-mL heparinized syringe.9 The volume of blood collected on day 1 was usually 3 mL, and the sample that remained after analysis was archived for future use. The volume of blood collected on day 2 or day 3 was usually 0.5 mL. Biochemical analysis of whole blood was performed by use of a point-of-care analyzera in accordance with the manufacturer's guidelines; blood was transferred directly from the syringe to the analyzer. The Hct was manually determined as previously described.10 Because the blood analyzer operated at 37°C (98.6°F), pH, Pco2, and Po2 values were corrected for the patient's temperature (cloacal temperature [used in analysis of blood samples on day 1] or environmental temperature [used in analysis of blood samples on all subsequent days]).15–20 Published equations were used for temperature correction, pH correction, and bicarbonate, anion gap, and osmolality calculations13,15–24 (Appendix). Calculation of the iCacor concentration and the iMgcor concentration was performed by use of the pHTC.21,22 Bicarbonate concentration in blood samples was calculated by use of the Henderson-Hasselbalch equation, pHTC, and Pco2TC. The αCO2 and pK values were calculated by use of previously described species-specific equations for use in analysis of blood samples of Kemp's ridley turtles.23 The percentage changes in the Hct and blood gas, acid-base, and biochemical variables for nonsurvivors that died on day 2 or 3 were calculated by use of values from day 1 and from day of death. For comparison, the percentage changes in the values of these variables were calculated for survivors by use of results from day 1 and results from day 2 or 3 (whichever day corresponded to the day of death of the matched nonsurvivor).
Statistical analysis—Results of analyses of blood samples obtained on day 1 and value of percentage change in each variable were compared for survivors versus nonsurvivors by use of a 1-way ANOVA.b Data that failed to meet assumptions of normality and equal variance were compared by use of a nonparametric Kruskal-Wallis 1-way ANOVA on ranks.b For 1 nonsurvivor that had a blood lactate concentration and Pco2 value that were higher than the analytic range of the analyzer, the maximum recorded values of these 2 variables that were found in the other turtles in this study were assigned. Values of P < 0.05 were considered significant.
Results
Of the 173 cold-stunned Kemp's ridley turtles that were admitted to the hospital at the New England Aquarium during the period of interest in the present study, 32 met the criterion for inclusion in the nonsurvivor group and 32 were selected for the survivor group (Table 1). Four turtles were evaluated in 2005, 18 in 2006, 2 in 2007, 16 in 2008, and 24 in 2009. Of the 32 nonsurvivors, 12 died within the first 24-hour period, 13 died within the second 24-hour period, and 7 died within the third 24-hour period after admission. Analysis of blood samples was not performed on the day of death for 1 turtle that died on day 2. Therefore, data from 19 turtles were used to calculate the percentage change between initial values and values at day 2 or 3 for Hct and blood gas, acid-base, and biochemical variables.
Weight, straight carapace length, and cloacal temperature (determined on the day of hospital admission [day 1]) for 32 cold-stunned Kemp's ridley turtles that died during the first 3 days of hospitalization (nonsurvivors) and 32 turtles that survived (survivors).
| Survivor group (n = 32) | Nonsurvivor group (n = 32) | |||
|---|---|---|---|---|
| Variable | Mean ± SD | Range | Mean ± SD | Range |
| Weight (kg) | 2.48 ± 0.86 | 0.90–4.60 | 2.72 ± 1.09 | 1.25–7.02 |
| Straight carapace length (cm) | 25.3 ± 3.3 | 18.8–31.9 | 26.6 ± 3.5 | 20.3–37.0 |
| Cloacal temperature (°C) | 12.3 ± 2.7 | 8.0–17.0 | 11.6 ± 3.2 | 5.3–18.6 |
For each nonsurvivor, a successfully rehabilitated turtle that had been evaluated closest in time to the nonsurvivor (within a maximum interval of ± 2 days) was selected for inclusion in a comparison survivor group.
Assumptions that data were normally distributed and equal in variance were met for Hct, anion gap, and iCacor, chloride, BUN, and bicarbonate concentrations in samples collected on day 1; data for all other variables did not meet these assumptions. The pHTC (P = 0.001), Po2TC (P = 0.004), and bicarbonate concentration (P = 0.017) were significantly lower on day 1 in nonsurvivors than in survivors (Table 2). The Pco2TC (P = 0.006) and potassium (P < 0.001) concentrations were significantly greater on day 1 in nonsurvivors than in survivors.
Values of selected clinicopathologic variables determined on day 1 in blood samples of survivor and nonsurvivor cold-stunned Kemp's ridley turtles described in Table 1.
| Survivor group (n = 32) | ||||
|---|---|---|---|---|
| Variable | Mean ± SD | Median | Range | 10th–90th percentile range |
| Hct (%) | 42 ± 9 | 40 | 29–71 | 32–50 |
| pHTC* | 7.53 ± 0.17 | 7.57 | 7.05–7.79 | 7.29–7.70 |
| Pco2TC (mm Hg)* | 27.5 ± 16.4 | 22.4 | 13.5–84.0 | 16.6–41.2 |
| Po2TC (mm Hg)* | 56.0 ± 25.6 | 50.4 | 13.8–129.7 | 23.9–85.3 |
| Bicarbonate concentration (mmol/L)* | 30.3 ± 6.9 | 31.3 | 17.4–43.6 | 21.5–39.4 |
| Sodium concentration (mmol/L) | 157.6 ± 5.9 | 157.9 | 146.3–166.7 | 149.7–165.9 |
| Potassium concentration (mmol/L)* | 3.97 ± 0.91 | 3.90 | 2.61–6.33 | 3.01–5.31 |
| Chloride concentration (mmol/L) | 117.2 ± 5.4 | 116.5 | 107.1–125.3 | 110.3–123.9 |
| iCacor concentration (mmol/L) | 0.72 ± 0.14 | 0.70 | 0.52–1.09 | 0.56–0.90 |
| iMgcor concentration (mmol/L) | 0.84 ± 0.17 | 0.85 | 0.61–1.27 | 0.64–1.04 |
| Glucose concentration (mg/dL) | 121 ± 90 | 110 | 17–381 | 35–242 |
| Lactate concentration (mmol/L) | 9.0 ± 5.2 | 8.0 | 2.3–22.5 | 3.9–16.5 |
| BUN concentration (mg/dL) | 15 ± 6 | 15 | 5–30 | 8–23 |
| Osmolality (mOsm) | 313.7 ± 13.3 | 312.9 | 294.1–340.9 | 295.7–336.7 |
| Anion gap (mmol/L) | 12.89 ± 7.30 | 12.58 | 1.80–30.30 | 4.95–21.96 |
Values are significantly (P < 0.05) different between survivors and nonsurvivors.
Compared with blood analysis findings in survivors, there were significantly greater percentage changes (from initial values to values at day 2 or 3) for iCacor (P = 0.032), potassium (P < 0.001), and lactate (P = 0.002) concentrations, and there were significantly lower percentage changes for pHTC (P = 0.005) and glucose (P = 0.001) and bicarbonate (P = 0.007) concentrations in nonsurvivors (Table 3). Assumptions that data for percentage change in each variable were normally distributed and equal in variance were met for the percentage changes in Hct and osmolality; data for all other variables did not meet these assumptions.
Percentage change in selected clinicopathologic variables determined in blood samples of the survivor and nonsurvivor cold-stunned Kemp's ridley turtles described in Tables 1 and 2 between day 1 and the day of death (nonsurvivors) or corresponding day of hospitalization (day 2 or 3; survivors).
| Survivor group (n = 32) | Nonsurvivor group (n = 32) | |||||||
|---|---|---|---|---|---|---|---|---|
| Variable | Mean ± SD | Median | Range | 10th–90th percentile range | Mean ± SD | Median | Range | 10th–90th percentile range |
| Hct | −4.7 ± 20.4 | −4.3 | −44.7 to 37.2 | −27.3 to 20.2 | −4.7 ± 29.8 | 0.9 | −100.0 to 15.4 | −14.9 to 13.4 |
| pHTC* | 1.8 ± 3.9 | 1.0 | −2.2 to 15.1 | −1.6 to 5.1 | −1.6 ± 4.3 | −3.1 | −7.1 to 8.2 | −6.7 to 3.7 |
| Pco2TC | 0 ± 31.3 | −0.2 | −61.4 to 61.0 | −33.8 to 40.6 | 37.3 ± 60.7 | 40.7 | −64.1 to 180.2 | −37.9 to 91.8 |
| Po2TC | 50.4 ± 88.9 | 25.2 | −26.8 to 335.0 | −17.1 to 134.1 | 12.1 ± 59.1 | 3.5 | −82.7 to 168.0 | −56.9 to 75.1 |
| Bicarbonate concentration* | 2.2 ± 20.8 | 0.2 | −47.4 to 44.1 | −15.7 to 28.0 | −12.6 ± 30.6 | −18.0 | −62.4 to 84.3 | −44.4 to 9.2 |
| Sodium concentration | −0.8 ± 2.1 | −1.2 | −4.9 to 3.1 | −3.3 to 1.8 | 0.3 ± 3.6 | −0.6 | −3.5 to 12.0 | −2.8 to 3.4 |
| Potassium concentration* | −12.3 ± 18.3 | −14.4 | −51.7 to 14.8 | −34.2 to 9.4 | 37.6 ± 46.3 | 44.3 | −55.7 to 122.7 | −28.2 to 80.9 |
| Chloride concentration | 0.3 ± 2.5 | 0.9 | −4.7 to 4.1 | −2.9 to 2.7 | 1.2 ± 2.8 | 0.8 | −5.2 to 4.6 | −2.0 to 4.1 |
| iCacor concentration* | 12.3 ± 37.1 | 6.3 | −13.6 to 159.7 | −7.9 to 18.6 | 15.1 ± 13.9 | 14.2 | −7.8 to 43.2 | −2.7 to 32.5 |
| iMgcor concentration | 9.5 ± 56.6 | −7.3 | −27.9 to 166.4 | −23.2 to 51.9 | 5.7 ± 20.2 | 1.4 | −23.1 to 60.6 | −15.7 to 25.5 |
| Glucose concentration* | 65.0 ± 93.0 | 45.6 | −33.8 to 343.8 | −12.2 to 178.4 | −13.6 ± 34.4 | −18.3 | −71.2 to 45.7 | −59.2 to 25.3 |
| Lactate concentration* | −34.8 ± 64.7 | −47.1 | −87.5 to 202.6 | −80.2 to 1.3 | 70.5 ± 98.3 | 45.0 | −63.2 to 233.3 | −42.3 to 222.1 |
| BUN concentration | 9.9 ± 15.9 | 9.2 | −31.6 to 47.4 | 0 to 26.7 | 17.4 ± 33.9 | 7.1 | −20 to 115.6 | −5.8 to 51.8 |
| Osmolality | −0.1 ± 2.2 | 0.1 | −4.2 to 3.1 | −3.0 to 2.6 | 0.2 ± 3.9 | −0.9 | −5.2 to 11.5 | −3.7 to 3.7 |
| Anion gap | 12.6 ± 68.9 | −16.1 | −42.8 to 223.2 | −37.6 to 53.4 | 46.4 ± 136.1 | 24.2 | −91.9 to 501.8 | −85.7 to 97.8 |
Values are significantly (P < 0.05) different between survivors and nonsurvivors.
Discussion
Physiologic responses of sea turtles to various natural and experimental stressors, including exposure to cold, have been described.9–12,15–17,25–27 Several studies9–12 have investigated hematologic, blood biochemical, and plasma biochemical values of cold-stunned Kemp's ridley turtles, one of which provided blood gas, pH, and blood biochemical data for turtles that were successfully rehabilitated after cold-stunning events.9 However, to the authors' knowledge, the present study is the first in which blood gas and pH values for cold-stunned turtles that subsequently died were assessed and in which those values were compared with values for cold-stunned turtles that survived.
On day 1, nonsurvivors had a significantly lower pHTC, Po2TC, and blood bicarbonate concentration and a significantly higher Pco2TC value than did survivors. This indicated that many cold-stunned turtles were affected by hypoxemia and a mixed (respiratory and metabolic) acidosis. The mean pHTC in blood samples collected on day 1 from survivors was 7.53 in the present study and 7.65 in another study.9 Homeostatic mechanisms in healthy vertebrates (including sea turtles) maintain relatively alkaline blood pH, and as body temperature decreases, the pH of blood increases.17,27 In the present study, the mean blood pHTC in the nonsurvivors on day 1 was 7.35, which was unexpectedly low for the mean cloacal temperature (11.6°C [52.9°F]) of these turtles and indicated acidosis. In addition, turtles that died on day 2 or 3 of hospitalization had a lower blood pHTC value and bicarbonate concentration on the day of death, compared with values on day 1. This indicated that acidosis was exacerbated prior to death. In contrast, the pHTC value and bicarbonate concentration remained stable or increased in survivors during the first 2 or 3 days of hospitalization.
In contrast to pH, the Pco2 in the blood of turtles decreases as body temperature decreases.17,27 Thus, a Pco2 value that is within the reference range in a turtle that has a cloacal temperature of 25°C (77°F) is considered to be high in a turtle that has a cloacal temperature of 10°C. For example, the mean Pco2TC in the blood of rehabilitated Kemp's ridley turtles is 30.4 mm Hg in those that have a cloacal temperature of 24.5°C (76.1°F) and is 20.7 mm Hg in those that have a cloacal temperature of 12.3°C (54.1°F).9 Similarly, the median Pco2TC in the blood of survivors on day 1 in the present study was 22.4 mm Hg (mean cloacal temperature, 12.3°C). Thus, the median Pco2TC value (35.4 mm Hg) in nonsurvivors having a mean cloacal temperature of 11.6°C on day 1 in the present study was more than 50% greater than the median Pco2 value that would be expected in a healthy turtle at that temperature (ie, this Pco2 value would be considered only mildly increased in a turtle that had a cloacal temperature of 25°C). These findings highlight the importance of temperature correction for pH and blood gas values of ectotherms.
Although there was no significant (P = 0.056) difference in mean percentage change of Pco2TC in survivors versus nonsurvivors in the present study, survivors generally had a Pco2 value on day 2 or 3 that was lower than or equal to their Pco2 value on day 1, and nonsurvivors generally had a Pco2 value on the day of death that was higher than their Pco2 value on day 1. Interpretation of these data suggests that an increase in an already high Pco2 value in a cold-stunned Kemp's ridley turtle that has received medical treatment indicates a poor prognosis. Although standard treatments for cold-stunned turtles are intended to improve the patient's ventilation, tissue perfusion, and buffering capacity, the present study has provided data that may be useful for improvement of these treatments.
As has been found in other studies,10,12 many cold-stunned turtles in the present study had hyperkalemia, and blood potassium concentrations on day 1 were higher in nonsurvivors than in survivors. Potassium concentrations increased over time in nonsurvivors but remained stable or decreased over time in survivors. The cause of hyperkalemia in cold-stunned turtles is unclear, but it is likely multifactorial; possible causes include impaired renal function, dehydration, and a compensatory response to acidosis.10,27 Other authors have reported27 that the plasma potassium concentration in loggerhead turtles (Caretta caretta) increases as the pH of blood decreases in response to a decrease in environmental temperature, and they suggested that this is caused by a shift of hydrogen ions into cells and a shift of potassium ions out of cells in an attempt to maintain physiologically normal pH. It is reasonable to suggest that a similar situation may exist in cold-stunned Kemp's ridley turtles. Concurrent acidosis (pHTC < 7.5) and hyperkalemia (blood potassium concentration > 4.0 mmol/L) were detected on day 1 in 14 nonsurvivors and 7 survivors in the present study (data not shown). Severe hyperkalemia is associated with bradyarrhythmias and death in many species.28,29 Consistent with previous findings10 in cold-stunned Kemp's ridley turtles, severe hyperkalemia was associated with a poor prognosis in the present study, and all 8 turtles with a blood potassium concentration > 6.4 mmol/L died within 72 hours after admission to the hospital. Of the Kemp's ridley turtles evaluated in another study,10 only 2 of the 142 turtles that survived cold stunning had a plasma potassium concentration > 6.4 mmol/L in the initial blood samples (unpublished data).
It has been suggested8 that gradual warming (eg, 2° to 3°C [3.6° to 5.4°F] increase/d for 5 to 7 days) is more successful than rapid warming (eg, 15°C [27°F] increase over 1 day) for successful rehabilitation (survival) of cold-stunned turtles. Although the reason for this clinical observation has not been experimentally determined, it is possible that rapid warming of cold-stunned turtles exacerbates metabolic and respiratory derangements (ie, a further decrease in blood pH and a further increase in Pco2 and blood potassium concentration) that may cause death as a result of severe acidosis or hyperkalemia. However, if a patient is gradually warmed over several days and medically treated to correct metabolic and respiratory derangements, the homeostatic response to the derangements may be more effective. As such, we continue to recommend gradual warming of cold-stunned turtles, especially those that are severely acidotic, hypercapnic, or hyperkalemic.
Investigators in another study10 found that sodium and chloride concentrations are higher in plasma of nonsurviving versus surviving cold-stunned turtles, but those results were not supported by the present study's findings. In addition, there was no significant difference between survivors and nonsurvivors with regard to the mean percentage change of sodium or chloride concentrations in blood samples during the first 2 or 3 days of hospitalization in the present study. The discrepancy in findings between the other study10 and the present study may be explained by the differing methods of case selection between the 2 studies. In the other study,10 data that were obtained up to the first 12 days of hospitalization were used as initial values for comparisons of hematologic and plasma biochemical variables over time, whereas in the present study, comparisons were made only for values that were obtained up to the first 3 days of hospitalization. Thus, analysis of results in the other study10 was more likely than analysis of results in the present study to reveal a change in the turtles' clinical status and response to treatment. Although blood sodium and chloride concentrations on day 1 were not significantly different between nonsurvivors and survivors in the present study, all turtles with sodium concentrations > 167 mmol/L (n = 10 turtles) or chloride concentrations > 125.3 mmol/L (7) died within 2 days after admission to the hospital. These findings suggest that some cold-stunned turtles were affected by dehydration and possibly salt gland dysfunction and that turtles with severe derangement of electrolyte concentrations may have a poor prognosis, as has been reported.10
In the present study, mean concentrations of iCacor in blood samples on day 1 were not significantly different between survivors and nonsurvivors and were similar to previously reported initial iCacor concentrations for cold-stunned Kemp's ridley turtles.9 However, mean concentrations of iCacor in blood samples on day 1 in the present study were lower than values reported for convalescent cold-stunned Kemp's ridley turtles9 and for other reptile species.30–35 The pathophysiologic cause of hypocalcemia in cold-stunned sea turtles is unknown. It is possible that transient hypocalcemia may be caused by a homeostatic response to elevated circulating concentrations of other divalent cations (eg, magnesium). A reduction in plasma iCa concentration in association with hypermagnesemia in humans has been reported and may be attributable to magnesium-induced inhibition of parathyroid hormone secretion.36 In the present study, the mean concentration of iMgcor in blood samples obtained on day 1 was elevated, compared with the iMgcor concentration reported for healthy Kemp's ridley turtles,10 and was similar to blood iMgcor concentrations in cold-stunned Kemp's ridley turtles reported in another study.9 The causes of hypermagnesemia in stranded sea turtles are unknown, but likely include ingestion or aspiration of seawater and impaired renal function.8 It is interesting that concentrations of iCacor in blood samples increased over the first 2 or 3 days of hospitalization to a significantly greater degree in turtles that died, compared with results for turtles that survived. Possible explanations for this finding include impaired renal function, dehydration, loss of cation homeostasis, lactic acidosis, or more aggressive administration of calcium in nonsurvivors than in survivors. Increased plasma calcium and magnesium concentrations have been detected in freshwater turtles during experimentally induced anoxia and lactic acidosis.37 It is thought that the plasma concentrations of these ions increase as calcium and magnesium carbonates (which serve as buffers during lactic acidosis) are released from bone.37 Similar mechanisms may be involved in Kemp's ridley turtles. Additional investigations of the clinical importance and appropriate medical management of iCa and iMg concentration derangements in sea turtles are warranted.
We detected substantial variation in the concentration of glucose in the blood of both survivors and nonsurvivors in the present study; some turtles had hypoglycemia, and some had hyperglycemia. Authors of other studies10–12 have described this same finding in cold-stunned sea turtles. Although speculative, possible causes of hypoglycemia in these turtles include anorexia, exhaustion, and sepsis. Possible causes of hyperglycemia in reptiles include physiologic responses to stress, over-compensation by gluconeogenic mechanisms, disease of the liver or pancreas, or administration of dextrose.38 Hyperglycemia of idiopathic origin has been described in reports of debilitated loggerhead sea turtles.39,40
Prior to completion of this study, it was the authors' clinical impression that nonsurviving cold-stunned Kemp's ridley turtles initially had higher circulating lactate concentrations than did their surviving counterparts. However, there was no significant difference in blood lactate concentration in day 1 samples of survivors versus those of nonsurvivors in the present study. The mean lactate concentration in blood samples collected from survivors on day 1 in this study was higher than that determined in cold-stunned Kemp's ridley turtles that survived in another study9 and was higher than concentrations determined in sea turtles exposed to moderate stressors (eg, pound net capture and general anesthesia).15,16,41 However, the mean lactate concentration in blood samples collected on day 1 in the present study was similar to concentrations detected in blood samples collected from sea turtles exposed to more severe stressors (eg, trawl net capture, experimental forced submergence, or long-duration voluntary dives).15,25,26,42–44 Blood lactate concentration increased by nearly 50% between day 1 and the day of death in nonsurvivors and decreased by approximately 50% in survivors over the corresponding period in the present study. Similar changes in blood lactate concentration in dogs that survived or died during hospitalization for gastric dilatation–volvulus syndrome have been reported.14 Data from the present study suggest that cold-stunned Kemp's ridley turtles with a blood lactate concentration that increases during the first 3 days of hospitalization (despite treatment) have a poor prognosis.
Mean BUN concentration in turtles in the present study was lower than concentrations typically found in healthy Kemp's ridley turtles,9,10 which is consistent with other published data for debilitated sea turtles.9–12 The pathophysiologic cause of this finding is unknown. However, impaired hepatic function, anorexia, or other metabolic disturbances have been proposed as contributing factors to low BUN concentrations in cold-stunned turtles.10 Specific clinicopathologic markers of liver disease in sea turtles have not been described, to the authors' knowledge. Results of 1 study45 indicate that measurement of circulating bile acids concentration may be useful in freshwater turtles. Therefore, measurement of circulating bile acids concentration should be considered in future studies of debilitated sea turtles. The mean Hct on day 1 was higher in cold-stunned turtles in the present study than in healthy Kemp's ridley turtles.10 This finding may be attributable to dehydration. A wide range of Hct values was detected in blood samples of turtles in the present study (severe hemoconcentration [Hct, 71%] to moderate anemia [Hct, 15%]). Anion gap values were somewhat higher than those previously reported for Kemp's ridley turtles.9,25 The reason for the discrepancy between findings of the present study and other studies is unclear, but it may be related to the high sodium concentration and low bicarbonate concentration in blood that were found in many turtles in the present study. The mean osmolality of blood was similar to previously published values for cold-stunned Kemp's ridley turtles.9 Because of a low BUN concentration, the osmolality of blood in cold-stunned sea turtles before treatment and rehabilitation may be lower than that in convalescent turtles.9
The methods that were used for blood collection and processing and for correction of results for temperature and pH in the present study are consistent with the methods used in other studies9,15,16 on the physiologic state of sea turtles, including Kemp's ridley turtles. Although the equations that were used in the present study to correct results of blood analyses for temperature and pH have not been validated in Kemp's ridley turtles, they are believed to provide data that are more relevant to the physiologic status of sea turtles than are data that have not been corrected for temperature and pH (ie, raw data from analyses performed at 37°C).15 In the present study, the values of pH in blood samples were corrected for patient temperature in accordance with the findings of other researchers that the pH of Kemp's ridley turtle blood increases approximately 0.015 U for every 1°C (1.8°F) decrease in environmental temperature within a specific range of temperatures (ie, actual pH value of blood > pH value of blood measured at 37°C).17 Because of this relationship between measured pH and temperature, the iCa and iMg concentrations in blood analyzed at 37°C are higher than the actual iCa and iMg concentrations in blood at lower temperatures.21,22 Therefore, the pHTC was used to calculate iCacor and iMgcor concentrations in the present study. Similarly, blood gas values were corrected for patient temperature in accordance with other researchers' findings that the actual values of Pco2 and Po2 in Kemp's ridley turtle blood at cloacal or environmental temperatures < 37°C are less than the values of these variables when they are measured at 37°C.15,16,18–20
Analysis of results of the present study indicated that cold-stunned Kemp's ridley turtles were often affected by metabolic and respiratory derangements and that the more severe derangements were associated with death. Thorough clinical assessment of cold-stunned Kemp's ridley turtles should include serial evaluation of venous blood pH, blood gas, and selected hematologic and blood biochemical variables. Such evaluations may provide useful clinical and prognostic information for clinicians and rehabilitators.
ABBREVIATIONS
| iCa | Ionized calcium |
| iCacor | pH-corrected ionized calcium |
| iMg | Ionized magnesium |
| iMgcor | pH-corrected ionized magnesium |
| Pco2TC | Temperature-corrected Pco2 |
| pHTC | Temperature-corrected pH |
| Po2TC | Temperature-corrected Po2 |
Critical Care Express, NOVA Biomedical, Waltham, Mass.
SigmaStat, Systat Software, San Jose, Calif.
References
- 1.↑
Marquez-Millan R, Burchfield PM, Diaz-Flores J, et al. Status of the Kemp's ridley turtle, Lepidochelys kempii. Chelon Conserv Biol 2005; 4:761–766.
- 2.
Morreale SJ, Standora EA. Western North Atlantic waters: crucial developmental habitat for Kemp's ridley and loggerhead sea turtles. Chelon Conserv Biol 2005; 4:872–882.
- 3.
Lazell JD. New England waters: critical habitat for marine turtles. Copeia 1980; 2:290–295.
- 4.
Gerle E, Digiovanni R, Pisciotta RP. A fifteen year review of cold-stunned sea turtles in New York Waters, in Proceedings. 18th Int Sea Turtle Symp 2000; 222–224.
- 5.
Morreale SJ, Meylan AB, Sadove SS, et al. Annual occurrence and winter mortality of marine turtles in New York waters. J Herp 1992; 26:301–308.
- 6.↑
Still BM, Griffin CR, Prescott R. Climatic and oceanographic factors affecting daily patterns of juvenile sea turtle cold stunning in Cape Cod Bay, Massachusetts. Chelon Conserv Biol 2005; 4:883–890.
- 7.
Burke VJ, Standora EA, Morreale SJ. Factors affecting strandings of cold stunned juvenile Kemp's ridley and loggerhead sea turtles in Long Island, NY. Copeia 1991; 4:1136–1138.
- 8.↑
Wyneken J, Mader DR, Weber ES, et al. Medical care of sea turtles. In: Mader D, ed. Reptile medicine and surgery. 2nd ed. St Louis: Elsevier, 2006;972–1007.
- 9.↑
Innis CJ, Tlusty M, Merigo C, et al. Metabolic and respiratory status of cold stunned Kemp's ridley sea turtles (Lepidochelys kempii). J Comp Physiol B 2007; 177:623–630.
- 10.↑
Innis CJ, Ravich JB, Tlusty MF, et al. Hematologic and plasma biochemical findings in cold-stunned Kemp's ridley turtles: 176 cases (2001–2005). J Am Vet Med Assoc 2009; 235:426–432.
- 11.
Carminati C, Gerle E, Kiehn LL, et al. Blood chemistry comparison of healthy vs. hypothermic juvenile Kemp's ridley sea turtles (Lepidochelys kempii) in the New York Bight, in Proceedings. 14th Annu Symp Sea Turtle Biol Conserv 1994; 203–207.
- 12.
Turnbull BS, Smith CR, Stamper MA. Medical implications of hypothermia in threatened loggerhead (Caretta caretta) and endangered Kemp's ridley (Lepidochelys kempii) and Green (Cheloniamydas) sea turtles, in Proceedings. Joint Conf Am Assoc Zoo Vet/Int Assoc Aquat Anim Med 2000; 31–35.
- 13.
Wellman ML, Dibartola SP, Kohn VW. Applied physiology of body fluids in dogs and cats. In: Dibartola SP, ed. Fluid, electrolyte and acid-base disorders in small animal practice. 3rd ed. St Louis: Saunders Elsevier, 2006;3–26.
- 14.↑
Zacher LA, Berg J, Shaw SP, et al. Association between outcome and changes in plasma lactate concentration during presurgical treatment in dogs with gastric dilatation-volvulus: 64 cases (2002–2008). J Am Vet Med Assoc 2010; 236:892–897.
- 15.↑
Chittick EJ, Stamper MA, Beasley JF, et al. Medetomidine, ketamine, and sevoflurane for anesthesia of injured loggerhead sea turtles: 13 cases (1996–2000). J Am Vet Med Assoc 2002; 221:1019–1025.
- 16.
Harms CA, Mallo KM, Ross PM, et al. Venous blood gases and lactates of wild loggerhead sea turtles (Caretta caretta) following two capture techniques. J Wildl Dis 2003; 39:366–374.
- 17.↑
Moon DY, Mackenzie DS, Owens DW. Simulated hibernation of sea turtles in the laboratory: I. feeding, breathing frequency, blood pH, and blood gases. J Exp Zool 1997; 278:372–380.
- 18.
Nunn JF, Bergman NA, Bunatyan A, et al. Temperature coefficients for Pco2 and Po2 of blood in vitro. J Appl Physiol 1965; 20:23–26.
- 19.
Ashwood ER, Kost G, Kenny M. Temperature correction of blood-gas and pH measurements. Clin Chem 1983; 29:1877–1885.
- 20.
Roughton FJW, Severinghaus JW. Accurate determination of O2 dissociation curve of human blood above 98.7% saturation with data on O2 solubility in unmodified human blood from 0° to 37°C. J Appl Physiol 1973; 35:861–869.
- 21.
Fogh-Anderson N. Ionized calcium analyzer with built in pH correction. Clin Chem 1981; 27:1264–1267.
- 22.
Ising H, Bertschat F, Günther T, et al. Measurement of free magnesium in blood, serum and plasma with an ion-sensitive electrode. Eur J Clin Chem Clin Biochem 1995; 33:365–371.
- 23.↑
Stabenau EK, Heming TA. Determination of the constants of the Henderson-Hasselbalch equation, αCO2 and pKa, in sea turtle plasma. J Exp Biol 1993; 180:311–314.
- 24.
Dorwart WV, Chalmers L. Comparison of methods for calculating serum osmolality from chemical concentrations, and the prognostic value of such calculations. Clin Chem 1975; 21:190–194.
- 25.
Stabenau EK, Heming TA, Mitchell JF. Respiratory, acid base, and ionic status of Kemp's ridley sea turtles (Lepidochelys kempii) subjected to trawling. Comp Biochem Physiol 1991; 99:107–111.
- 26.
Snoddy JE, Landon M, Blanvillain G, et al. Blood biochemistry of sea turtles captured in gillnets in the lower Cape Fear River, North Carolina, USA. J Wildl Manage 2009; 73:1394–1401.
- 27.↑
Lutz PL, Bergey A, Bergey M. Effects of temperature on gas exchange and acid-base balance in the sea turtle Caretta caretta at rest and during routine activity. J Exp Biol 1989; 144:155–169.
- 28.
Normal BC, Barrett KA. Wide complex tachycardia associated with severe hyperkalemia in three cats. J Feline Med Surg 2006; 8:372–378.
- 29.
Gorantitou G, Stavrianki D, Babalis D. Wide QRS tachycardia caused by severe hyperkalemia and digoxin intoxication. Acta Cardiol 2005; 60:437–441.
- 30.
Silver RB, Jackson DC. Ionic compensation with no renal response to chronic hypercapnia in Chrysemys picta belli. Am J Physiol Reg Int Comp Physiol 1986; 251:1228–1234.
- 31.
Rooney MB, Levine G, Gaynor J, et al. Sevoflurane anesthesia in desert tortoises. J Zoo Wildl Med 1999; 30:64–69.
- 32.
Sleeman JM, Gaynor J. Sedative and cardiopulmonary effects of medetomidine and reversal with atipamezole in desert tortoises (Gopherus agassizii). J Zoo Wildl Med 2000; 31:28–35.
- 33.
Dennis PM, Bennett RA, Harr KE, et al. Plasma concentration of ionized calcium in healthy iguanas. J Am Vet Med Assoc 2001; 219:326–328.
- 34.
Eatwell K. Variations in the concentration of ionized calcium in the plasma of captive tortoise (Testudo species). Vet Rec 2009; 165:82–84.
- 35.
Eatwell K. Comparison of total calcium, ionized calcium and albumin concentrations in the plasma of captive tortoises (Testudo species). Vet Rec 2009; 165:466–468.
- 36.↑
Cholst IN, Steinberg SF, Tropper PJ, et al. The influence of hypermagnesemia on serum calcium and parathyroid hormone levels in human subjects. N Engl J Med 1984; 310:1221–1225.
- 37.↑
Reese SA, Jackson DC, Ultsch GR. The physiology of overwintering in a turtle that occupies multiple habitats, the common snapping turtle (Chelydra serpentina). Physiol Biochem Zool 2002; 75:432–438.
- 38.↑
Stahl S. Hyperglycemia in reptiles. In: Mader D, ed. Reptile medicine and surgery. 2nd ed. St Louis: Elsevier, 2006;822–830.
- 39.
Jacobson ER, Homer BL, Stacy BA, et al. Neurological disease in wild loggerhead sea turtles Caretta caretta. Dis Aquat Organ 2006; 70:139–154.
- 40.
Norton T, Rowles T, Stacy B, et al. Loggerhead neurological disease complex (2001 and 2006 mortality events) and event response, in Proceedings. Initial Meet Loggerhead Neurol Dis Complex Work Group 2008;22.
- 41.
Moon PF, Stabenau EK. Anesthetic and postanesthetic management of sea turtles. J Am Vet Med Assoc 1996; 208:720–726.
- 42.
Berkson H. Physiological adjustments to prolonged diving in the Pacific green turtle (Chelonia mydas agassizii). Comp Biochem Physiol 1966; 18:101–119.
- 43.
Wood SC, Gatz RN, Glass ML. Oxygen transport in the green sea turtle. J Comp Physiol B 1984; 154:275–280.
- 44.
Lutz PL, Bentley TB. Respiratory physiology of diving in the sea turtle. Copeia 1985; 3:671–679.
- 45.↑
Knotkova Z, Dorrestein GM, Jekl V, et al. Fasting and postprandial serum bile acid concentrations in 10 healthy female red-eared terrapins (Trachemys scripta elegans). Vet Rec 2008; 163:510–514.
Appendix
Equations used in calculation of metabolic and respiratory variables for cold-stunned Kemp's ridley turtles.
| Calculation category | Equation | References |
|---|---|---|
| Correction for temperature | pHTC = (0.015 × ΔT) + pH | 17 |
| Pco2TC = Pco2 × 10(−0.019 × ΔT) | 15, 16, 18, and 19 | |
| Po2TC = Po2 × 10(−0.0058 × ΔT) | 15, 16, 19, and 20 | |
| Correction for pH | iCacor concentration = iCa concentration × (1 + [0.53 × {pH − pHTC}]) | 21 |
| iMgcor concentration = iMg concentration × 10(−0.2 × [pHTC − pH]) | 22 | |
| Henderson-Hasselbalch | HCO3− concentration = αCO2 × Pco2TC × 10(pHTC − pK) | 23 |
| Additional calculations | Anion gap = (Na+ concentration + K+ concentration) − (Cl− concentration + HCO3− concentration) | 13 |
| Osmolality = (1.86 × Na+ concentration) + (Glu concentration/18) + (BUN concentration/2.8) + 9 | 24 |
ΔT = 37 − patient temperature (in °C), where patient temperature is the temperature (cloacal [day 1] or environmental [day 2 or 3]) of the turtle. Glu = Glucose.
