Salzman A L, Strong K E, Wang H, Wollert P S, Vandermeer T J, Fink M P
Department of Surgery, Massachusetts General Hospital, Boston.
Crit Care Med. 1994 Jan;22(1):126-34. doi: 10.1097/00003246-199401000-00024.
To determine if air introduced directly into the lumen of a hollow viscus can be used instead of fluid in a Silastic balloon to estimate gastrointestinal mucosal PCO2.
Prospective, unblinded comparison of two methods of mucosal PCO2 measurement.
Animal surgery suite at a large, university-affiliated medical center.
Standard, commercially available, tonometric catheters were positioned in the ileum (n = 4) or the stomach and ileum (n = 12) of anesthetized, immature Yorkshire swine. Using gas-tight purse-string sutures, plastic cannulas were inserted into the lumen of the stomach (n = 12) and the lumen of a 10-cm isolated segment of ileum (n = 16). Data were collected after equilibration periods of 30 or 60 mins. Before each equilibration period, the "air tonometers" (i.e., the lumens of the stomach and/or the isolated ileal segment) were lavaged with 200 mL (stomach) or 20 mL (ileum) of air. In group 1 (n = 4) and group 2 (n = 3), graded degrees of mesenteric hypoperfusion were achieved by mechanical mesenteric occlusion or pericardial tamponade, respectively. In group 3 (n = 8), graded degrees of respiratory acidosis were induced. At various intervals, PCO2 was determined simultaneously in arterial blood, gastric air, saline from the gastric tonometric balloon, ileal air, and saline from the ileal tonometric balloon.
In pigs with ischemia created by mesenteric vascular occlusion (group 1), there was a moderate correlation between PCO2 values in air samples from the ileal lumen and samples of saline from the standard tonometer (r2 = .61, p < .001). In pigs with mesenteric ischemia secondary to pericardial tamponade (group 2), air and saline tonometry were well-correlated in the stomach (r2 = .71, p < .001) and ileum (r2 = .83, p < .001). In pigs with normal mesenteric perfusion (group 3) and PaCO2 > 40 torr (5.3 kPa), PaCO2 correlated with ileal mucosal PCO2, determined using air (r2 = .93, p < .001) or saline (r2 = .91, p < .001) tonometry, or gastric mucosal PCO2, determined using air (r2 = 1.00, p < .001) or saline (r2 = .97, p < .001) tonometry. Values obtained by air tonometry were highly correlated with values obtained using standard saline tonometry in the stomach (r2 = .98, p < .001; bias = -5 +/- 5 torr [-0.65 +/- 0.65 kPa]) or ileum (r2 = .96, p < .001; bias = 1 +/- 9 torr [0.13 +/- 1.17 kPa]).
a) Under stable hemodynamic and respiratory conditions, air tonometry (which, in theory, can be performed using a conventional nasogastric or nasoenteric feeding tube) estimates gastrointestinal mucosal PCO2 as accurately as standard saline tonometry in the stomach or ileum; b) respiratory acidosis leads to tissue hypercarbia, a phenomenon that must be considered when tonometry is used to guide therapy in the clinical setting; c) under stable, nonischemic conditions, gastric or intestinal tonometry can be used to estimate PaCO2.
确定直接注入中空脏器管腔内的空气是否可替代硅橡胶球囊内的液体来评估胃肠道黏膜PCO₂。
对两种黏膜PCO₂测量方法进行前瞻性、非盲法比较。
一所大型大学附属医院的动物手术套房。
将标准的市售张力测定导管放置在麻醉的未成熟约克郡猪的回肠（n = 4）或胃和回肠（n = 12）中。使用气密荷包缝合线，将塑料套管插入胃腔（n = 12）和一段10厘米长的孤立回肠腔（n = 16）。在30或60分钟的平衡期后收集数据。在每个平衡期之前，用200毫升（胃）或20毫升（回肠）空气冲洗“空气张力计”（即胃和/或孤立回肠段的管腔）。在第1组（n = 4）和第2组（n = 3）中，分别通过机械性肠系膜阻塞或心包填塞实现不同程度的肠系膜灌注不足。在第3组（n = 8）中，诱导不同程度的呼吸性酸中毒。在不同时间间隔，同时测定动脉血、胃内空气、胃张力测定球囊内的盐水、回肠内空气和回肠张力测定球囊内的盐水的PCO₂。
在因肠系膜血管阻塞导致缺血的猪（第1组）中，回肠腔空气样本中的PCO₂值与标准张力测定仪盐水样本中的PCO₂值之间存在中度相关性（r² = 0.61，p < 0.001）。在因心包填塞继发肠系膜缺血的猪（第2组）中，胃（r² = 0.71，p < 0.001）和回肠（r² = 0.83，p < 0.001）的空气和盐水张力测定相关性良好。在肠系膜灌注正常的猪（第3组）且动脉血二氧化碳分压（PaCO₂）> 40托（5.3千帕）时，PaCO₂与使用空气（r² = 0.93，p < 0.001）或盐水（r² = 0.91，p < 0.001）张力测定法测定的回肠黏膜PCO₂，或与使用空气（r² = 1.00，p < 0.001）或盐水（r² = 0.97，p < 0.001）张力测定法测定的胃黏膜PCO₂相关。空气张力测定法获得的值与胃（r² = 0.98，p < 0.001；偏差 = -5 ± 5托[-0.65 ± 0.65千帕]）或回肠（r² = 0.96，p < 0.001；偏差 = 1 ± 9托[0.13 ± 1.17千帕]）中使用标准盐水张力测定法获得的值高度相关。
a）在稳定的血流动力学和呼吸条件下，空气张力测定法（理论上可使用传统的鼻胃管或鼻肠饲管进行）在胃或回肠中评估胃肠道黏膜PCO₂的准确性与标准盐水张力测定法相同；b）呼吸性酸中毒会导致组织高碳酸血症，在临床环境中使用张力测定法指导治疗时必须考虑这一现象；c）在稳定的非缺血条件下，胃或肠道张力测定法可用于估计PaCO₂。
