Abstract 55: Gasping During Fatal Hemorrhagic Shock Increases Cerebral Blood Flow
Objectives: Gasping has been characterized by rapid and vigorous inspirations commonly observed during cardiac arrest. In recent studies, spontaneous gasping has been associated with improved ventilation, stroke volume, and cerebral blood flow (CBF) during untreated cardiac arrest. However, spontaneous gasping has not well observed during fatal hemorrhagic shock. In this study, we hypothesized that spontaneous gasping is observed and improves CBF during fatal hemorrhagic shock.
Methods: This study was approved by the Institute’s Animal Use and Care Committee. Eight Wistar male rats (body weight: 195 to 225 g) were anesthetized with sodium pentobarbiturate intraperitoneally (1.25 to 1.75 mg/kg) and heparinized. Arterial pressure was recorded from the left femoral artery. Respiratory movement was recorded by a pressure sensor placed on the animal’s back (Sukinos Co., Ltd., Nagoya, Japan). The left carotid artery was cannulated to draw blood (0.1 ml/min) continuously to induce hemorrhagic shock. The tracheal cannula was not inserted and the animal’s spontaneous respiration was kept during this study. CBF was measured by Laser flow meter (Advance Co., Ltd., Tokyo, Japan). Statistical analyses were performed by paired t-test using SPSS12.0J™. All values were expressed as the mean±SEM.
Results: After 7.3±0.3 ml of blood drawing, pulseless electrical activity (PEA) was induced and 6 to 20 times (median: 18) of spontaneous gasping were observed in all animals. Although CBF, which was averaged 49.4±3.9 ml/min/100mg before starting hemorrhage, significantly decreased to 2.8±0.7 ml/min/100mg during PEA (paired t-test: P=0.001), gasping generated significant CBF increases (28.7±6.3 ml/min/mg, paired t-test: P=0.004).
Conclusions: During fatal hemorrhagic shock, spontaneous gasping was observed and produced prominent increases in CBF. Forceful contraction of inspiratory muscles during gasping may decrease the intrathoracic pressure and favor venous return to the heart and thereby increase CBF.