An experimental model of intestinal resection and compensated non-hypotensive blood loss.

BACKGROUND: Massive hemorrhage results in hypovolemia and hypotension that activate the sympathetic-adrenal-system, the hypothalamic-pituitary-adrenal axis, and induce metabolic changes such as hyperglycemia. Blood loss during surgery, however, is rapidly compensated by intravenous fluids to minimize negative impact on circulation. The aim of this study was to develop an experimental model for studies of the stress response and metabolic alterations seen after major abdominal surgery by combining intestinal resection with compensated non-hypotensive blood loss. MATERIAL AND METHODS: Intestinal resection in the rat was combined blood loss (7% and 16% of total blood volume) with subsequent fluid replacement (2 x volume of saline + hydroxyethyl starch, 50:50) to investigate the effects on blood pressure, plasma adrenaline, noradrenaline (0-2 h postoperatively), glucose, insulin, corticosterone, and hematocrit (0-24 h postoperatively). RESULTS: Surgical trauma alone or in combination with blood loss and fluid replacement did not decrease mean arterial blood pressure (MAP) compared with anesthetized controls. Plasma levels of catecholamines were unchanged during the period of blood loss. After surgery and blood loss, plasma glucose showed a blood loss volume-dependent increase up to 12 h postoperatively compared to surgery alone (P < 0.001-0.05). Plasma corticosterone increased after surgery alone and in combination with blood loss but the changes were not dependent on the magnitude of blood loss. CONCLUSIONS: Surgical trauma combined with compensated non-hypotensive blood loss induced persistent volume-dependent hyperglycemia that did not depend on changes in plasma corticosterone and, in the early postoperative phase, MAP and catecholamines. Our data indicate that blood loss per se, without causing hypotension or acute elevations in catecholamines, can induce marked postoperative hyperglycemia. The experimental model presented in this report will be a useful tool to further elucidate mechanisms underlying the changes in glucose metabolism seen after surgical injury.

Preoperative glucocorticoid administration attenuates the systemic stress response and hyperglycemia after surgical trauma in the rat.

The stress response to surgery is characterized by activation of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, and by an inflammatory response and hyperglycemia. The aim of the present study was to investigate if preoperative corticosterone could reduce the postoperative systemic stress response, without aggravating hyperglycemia or interfering with activation of the hypothalamic-pituitary-adrenal axis, in a standardized rat model of surgical trauma. We used a standardized experimental model of intestinal resection in the rat. Exogenous corticosterone (8 mg/kg body weight) or vehicle was administered 2 hours before surgery; and postoperative plasma concentrations of interleukin-6, interleukin-10, adrenaline, noradrenaline, glucose, and insulin were determined. Exogenous corticosterone decreased preoperative plasma adrenaline but did not change plasma glucose or insulin levels. Moreover, corticosterone reduced postoperative plasma interleukin-6, catecholamines, and glucose (all P < .001-.05) without any effect on the plasma corticosterone concentration compared with vehicle-treated controls. A preoperative 2-hour exposure of physiologic poststress corticosterone concentrations not only suppressed plasma IL-6 levels but also inhibited surgery-induced adrenaline release and suppressed plasma glucose levels. We hypothesize that glucocorticoids attenuated the inflammatory response in injured tissues that reduced afferent input into brain areas regulating the neuroendocrine response.

CRF-receptor 1 blockade attenuates acute posttraumatic hyperglycemia in rats.

BACKGROUND: Hyperglycemia and insulin resistance after surgical stress are mediated by a complex neuroendocrine response. The present studies were undertaken to determine whether a corticotropin releasing factor (CRF)-receptor 1 (R1) antagonist, CP-154,526 (CP) could alter trauma-induced effects on blood glucose levels, insulin action on skeletal muscle, and dexamethasone-induced suppression of endogenous glucocorticoid secretion. MATERIALS AND METHODS: We used a standardized experimental model of small intestinal resection in the rat. Studies were performed 2 hours after surgery in four groups of rats (n = 24-48) given vehicle or 40 mg of CP i.p. 1 hour before surgical trauma or only anesthesia (controls). Measurements of (I) b-glucose and p-insulin, corticosterone, and ACTH; (II) glucose transport; (III) phosphatidylinositol 3-kinase (PI 3-K) activity in skeletal muscle; and (IV) the dexamethasone-suppression test were performed. RESULTS: Surgery resulted in hyperglycemia, reduced insulin-stimulated glucose transport, and a pathological dexamethasone-suppression test. B-glucose levels were attenuated in traumatized rats given CP compared to vehicle (P < 0.05). After surgery, p-corticosterone levels were moderately reduced by CP (P < 0.05) and p-ACTH unchanged by the drug. Glucose transport and PI 3-kinase activity as well as the dexamethasone-suppression test were unaffected by administration of CP. CONCLUSIONS: Hyperglycemia in response to small intestinal resection in the rat could be reduced but not inhibited by CRF-R1 blockade. We hypothesize that CRF action within the central nervous system can regulate the hyperglycemic response to surgical stress via mechanisms other than the pituitary-adrenal axis. Our results also indicate that the hypothalamic stress response after surgical stress is dependent on other factors apart from CRF.