| Objective:1.To replicate an animal model for study of early oral resuscitation for burn shock.2.To investigate the changes of gastrointestinal functions after burn and the resuscitative effects of early oral resuscitation on early burn shock.3.To evaluate thereputic effects of carbachol on early oral resuscitation of burn shock.Methods:Part one:Male Beagle dogs were surgically prepared for measurement of hemodynamic parameters,and 24 hours later were subjected to a 35%TBSA full-thickness flame injury under a 10-15 minutes of anesthesia byⅣinjection of propofol.Animals were randomly divided into non-resuscitation group,oral resuscitation and intravenous(Ⅳ)resuscitation group.Oral resuscitation included gastric delivery and enteral delivery.In the first 24 hours after burn,non-resuscitation group got no treatment,gastric and enteral resuscitation group received gastric or enteral infusion of a glucose-electrolyte solution(GES),and intravenous resuscitation group received intravenous infusion of lactated Ringer's(LR)solution.The delivery rates of above two solutions were both in accordance with that of Parkland formula,which requires 4 ml/kg of fluid per 1%TBSA burn during the first 24 hours,with half delivered in the first 8 hours and the remaining half during the next 16 hours.Intestinal absorption rate of GES was determined in enteral resuscitation group,and at 8h after burn,the enteral resuscitated dogs were euthanized to collect the total amount of fluid in the intestine for measurement of absorptive percent of GES.In the other three groups, delayedⅣresuscitation were initiated after the first 24h sfter burn,follwed byⅣnutrational support from the 72th hour.Gastric emptying rate in the first 8 hours were determined in gastric resuscitation group.Changes in hemodynamics, gastrointestinal perfusion,haematocrit(HCT)and organ function parameters were determined at 0,2,4,8,24,48,72h and 120h after burn in all groups.At the end of 120-hour-period experiment,all animals were euthanized for pathologic evaluation and calculation of mortality.Part two:Male Beagle dogs were subjected to 50%TBSA burn injury by method of part one,and divided into six groups:non-resuscitation,gastric resuscitation with GES,gastric resuscitation with GES combined with carbachol(20μg/kg),enteral resuscitation with GES, enteral resuscitation with GES combined with carbachol,and intravenous resuscitation with LR.Treatment of each group was similar with part one.Except the two enteral resuscitation groups which were euthanized at 8h after burn,the other groups were euthanized at 72h after burn.Besides all parameters in part one, changes in TNF-αlevel in plasma,and levels ofNOS,XOD,MDA in tissue were also determined.Results:1.The gastric emptying and intestinal absorption rate of GES reduced markedly to half of pre-injury level after 35%TBSA burn.Intestinal mean absorption rate of water in 8 hours after 35%TBSA burn was similar to the infusing rate(99+47 vs.81±11 ml·h-1·m-1,P＞0.05).In the first 24 hours after 35%TBSA burn,oral resuscitation animals showed better hemodynimics, gastrointestinal perfusion,and organ function parameters to non-resuscitation ones (P＜0.05).However,oral resuscitation did not provide same therapeutic effects asⅣresuscitation group(P＜0.05 or P＜0.01).After the initiation of delayedⅣresuscitation,hemodynamics and gastrointestinal perfusion in three groups had no statistical difference(P＞0.05).Early gastric resuscitation reduced the mortality compared to non-treatment(0 vs.33.3%).2.In 50%TBSA burn injured animals, gastric emptying and intestinal absorption rate of GES were both significantly reduced,and mean absorption rate was significantly lower than infusing rate (46±34 VS.97±7 ml·h-1·m-1,P＜0.01).Groups resuscitated with GES plus carbachol showed better gastrointestinal function,gut perfusion,and hemodynamics than groups resuscitated with GES alone(P＜0.05 or P＜0.01). Plasma levelof TNF-αand tissue levels of NOS,XOD and MDA were lower in GES+carbachol group than those in only GES group(P＜0.05 or P＜0.01).All gastrointestinal resuscitation groups did not appear same resuscitative effects as IR group(P＜0.05 or P＜0.01).Conclusion:1.The protocol and animal model in this study exactly reflected the actual circumstance such as battle fields or accident sites whereⅣresuscitation is limited in treating early burn shock.It is an ideal animal model for study of early oral resuscitation of burns.2.After 35%TBSA burn,early oral resuscitation provides better resuscitative and outcomes than non- resuscitation, but can not reach the therapeutic effect ofⅣresuscitation.Because intestinal absorptive ability still can match the requirement of Parkland formula,the attenuated gastric emptying maybe the major limiting factor.3.After 50%TBSA burn,the markedly attenuated gastric emptying and intestinal absorptive ability both can't match the requirement of Parkland formula.4.Carbachol can efficiently promote the resuscitative effects of oral resuscitation in 50%TBSA burn.This might relate to its activating effects on cholinergic pathway.
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