Selective impairment of nutrient absorption from intestines with chronic venous hypertension.

Malnutrition is frequently associated with advanced cirrhosis. To investigate the role of portal hypertension in nutritional impairment, we developed an animal model to isolate and characterize the effects of chronic intestinal venous hypertension on intestinal nutrient absorption. We performed mesenteric arteriovenous anastomosis combined with portal vein banding in rats. Hepatic architecture and excretory function (bile flow and bile salt output) were unaltered, while severe and persistent intestinal venous hypertension was produced. We then measured in vivo absorption rates of three test nutrients (vitamin D3, valine, and tryptophan) and water. Vitamin D3 absorption was significantly impaired by intestinal congestion, while amino acid absorption was unaffected. Splanchnic hypertensive rats absorbed less water than controls. We conclude that chronic intestinal venous hypertension alone selectively impairs nutrient absorption.

Transcutaneous pacing in a hypothermic-dog model.

STUDY OBJECTIVE: To evaluate the hemodynamic response to transcutaneous pacing (TCP) during rewarming from hypothermia. METHODS: We conducted a prospective, controlled laboratory investigation using 20 mongrel dogs. The animals were anesthetized, intubated, and mechanically ventilated. Arterial pressure, core temperature, and cardiac rhythm were continuously monitored. All dogs were cooled to a core temperature of 27 degrees C; experimental animals were then subjected to TCP with active rewarming, and control animals underwent sham transcutaneous pacing and rewarmed in the same manner. Serial hemodynamic measurements, time to rewarming, and cardiac isoenzyme concentrations were analyzed. RESULTS: Rewarming was accomplished significantly faster in the paced group (171.5 +/- 31.5 minutes) than in the control group (254 +/- 55.9 minutes, P < .05). After rewarming, the mean cardiac index in the paced dogs returned to 84% of baseline, compared with 63% of baseline in the nonpaced group (P < .05). None of the paced animals demonstrated significant hemodynamic deterioration, potentially lethal arrhythmias, or other evidence of myocardial injury. CONCLUSION: TCP is safe, effective and easily implemented in dogs. In this small series of dogs, TCP restored and maintained hemodynamic stability and allowed the hypothermic animals to rewarm in half the time required by their nonpaced counterparts.