The Effects of Isovolemic Hemodilution on Hemodynamic Changes in Myocardial Ischemia-Induced Dogs / 대한마취과학회지

BACKGROUND: Anesthesiologists often encounter patients who have acute, massive blood loss and severe hemodilution as the result of fluid therapy in the operating room. It is known that patients with normal heart function survive at hemoglobin 4 6 g/dl. Recently, the incidence of elderly patients with ischemic heart disease have been increasing progressively but studies about critical hematocrit level in patients with ischemic heart disease are rare. This study, therefore, was designed to evaluate the hemodynamic response of isovolemic hemodilution in myocardial ischemia-induced dogs. METHODS: In 12 anesthetized dogs, a Swan-Ganz catheter and left ventricle catheter were inserted and hemodynamic parameters were measured as control values. Myocardial ischemia was induced with a left anterior descending (LAD) coronary artery ligation. Thereafter, isovolemic hemodilutions were done several times to set the hematocrit levels of 36%, 31%, 26%, 21%, 16%, and 11%. Records and samples for hemodynamic parameters were obtained after LAD ligation and at each hematocrit level. RESULTS: There were significant decreases in diastolic blood pressures in hematocrits 21%, 16%, 11%, in mean arterial pressures in hematocrits 16%, 11% and in systolic blood pressure in hematocrit 11% (P < 0.05). Oxygen delivery progressively decreased in hematocrits 36%, 31%, 26%, 21%, 16% and 11% (P < 0.05). Oxygen extraction ratios progressively increased and were statistically significant in hematocrits 21%, 16% and 11% (P < 0.05). Arterial blood gases showed metabolic acidosis in hematocrits 16% and 11%. There was decreased PCO2 in hematocrit 11% (P < 0.05). Mixed venous blood oxy-hemoglobin saturation decreased in hematocrit 16% and 11% (P < 0.05). Other variables were not significant. CONCLUSIONS: Blood pressure decreased at hematocrit 16% so it is necessary to maintain a hematocrit level above 21% at least in cardiac depressed dogs.

Acid-Base Regulation during Hypothermia in Dogs / 대한마취과학회지

BACKGROUND: Controversy exists regarding acid-base management during hypothermia. Two different concepts of arterial blood gas (ABG) management during hypothermia have been proposed to date; pH-stat and alpha-stat. There has been no consistency about physiological benefit provided by one protocol over the other. Most of previous studies have investigated the effects of two different strategies during cardiopulmonary bypass or controlled ventilation. We studied the actual acid-base regulation during acute hypothermia in anesthetized dogs with spontaneous ventilation. METHODS: With institutional review board approval, 10 mongrel dogs were anesthetized with intravenous pentobarbital 25 mg/kg. The dogs were kept to have spontaneous ventilation with trachea intubated. After monitoring devices were placed, the rectal temperature was lowered to 32oC with wet towel, cold solution, and ice cubes. ABG analyses were performed at each degree drop of body temperature from 37oC to 32oC. The pH and arterial carbon dioxide tension (PaCO2) were measured at 37oC and were corrected to the actual body temperature. [OH- ]/[H- ] was also calculated. RESULTS: Non-corrected pH values tended to decrease and PaCO2 values tended to increase as the temperature dropped. The temperature corrected pH and PaCO2 values were almost constant through 37oC to 32oC. [OH- ]/[H-] was declined with a drop of temperature. CONCLUSIONS: The acid-base regulation during acute hypothermia in anesthetized dogs with spontaneous ventilation is considered to be the pattern close to "pH-stat" regulation.