[Systemic pathologic physiology parameters changes in sheep drowning: a control study in freshwater and seawater].

OBJECTIVE

To compare the systemic pathologic physiology parameter changes in sheep drowning in freshwater and seawater.

METHODS

The experimental animals were healthy crossbred sheep. According to the envelope method, 24 sheep were randomly divided into two groups, with 12 animals in each group. The animals in both groups were subjected to mechanical ventilation and analgesia and sedation, the drowning models were reproduced by injecting 10-25 mL/kg of seawater or freshwater into the endotracheal tube of animals. The changes in hemodynamics before drowning, immediately after drowning (immediately after water injection) and 30, 60, and 120 minutes after drowning in both groups were recorded. The urine color changes after drowning and occurrence time were recorded. The animals were sacrificed at 120 minutes after drowning, and heart, kidney, liver, spleen and intestine were harvested for pathological observation under light microscope using hematoxylin and eosin (HE) staining.

RESULTS

(1) The changes in systemic hemodynamic: there was no significant difference in hemodynamics before drowning between the two groups. Compared with before drowning, heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), left ventricular maximum systolic force index (dPmax), and pulmonary wedge pressure (PAWP) immediately after drowning in both seawater and freshwater groups were significantly increased, which showed a decrease tendency with drowning time prolongation. Compared with drowning immediately, dPmax at 30 minutes after freshwater drowning was significantly decreased (mmHg/s: 919.83±14.51 vs. 2 628.42±59.75, P < 0.01), which was below the level before drowning till 120 minutes. CO at 30 minutes after freshwater drowning was retreated as compared with drowning immediately, but it was still higher than that before drowning (L/min: 8.25±0.66 vs. 5.75±0.73, P < 0.01). Global end-diastolic volume (GEDV) and PAWP at 120 minutes after freshwater drowning were decreased to the level before drowning [GEDV (mL): 642.92±7.29 vs. 638.25±7.00, PAWP (mmHg, 1 mmHg = 0.133 kPa): 5.83±1.19 vs. 5.42±1.08, both P > 0.05]. Compared with immediately after drowning, MAP, CO and PAWP at 30 minutes after seawater drowning were significantly lowered [MAP (mmHg): 90.50±3.58 vs. 159.42±3.18, CO (L/min): 2.37±0.45 vs. 10.33±0.73, PAWP (mmHg): 4.17±0.72 vs. 11.75±1.82, all P < 0.01], which were lower than those before drowning till 120 minutes. After drowning for 30 minutes, MAP, CO and PAWP in seawater group were significantly lower than those in freshwater group [MAP (mmHg): 90.50±3.58 vs. 117.42±1.78, CO (L/min): 2.37±0.45 vs. 8.25±0.66, PAWP (mmHg): 4.17±0.72 vs. 24.83±1.27], dPmax was significantly increased (mmHg/s: 1 251.42±62.50 vs. 919.83±14.51, all P < 0.01), and the tendency continued till 120 minutes. There was no significant difference in HR at all the time points between the two groups. (2) The changes in urine: after freshwater drowning, the animals had hemoglobinuria and lasted until the end of the experiment, and the time of hemoglobinuria occurrence was at 20-35 minutes after drowning with an average of (25.30±5.15) minutes. After seawater drowning, the change in urine was not found until the end of the experiment. (3) The variations of each organ tissue in pathology and hematology at 120 minutes after drowning: after freshwater drowning, the systemic tissue edema was found in organs such as heart, kidney, liver, spleen, and small intestine. After seawater drowning, there were different degrees of edema in the systemic organs, and some of them shrank.

CONCLUSIONS

After freshwater drowning, the animals showed decreased dPmax, increased CO and blood volume, edema and hemolysis of the tissue cells. After seawater drowning, CO and blood volume decreased, and some tissue cells were in atrophy.