Reflectance spectrophotometry in the gastrointestinal tract: Limitations and new applications

OBJECTIVE:Reflectance spectrophotometry (RS) assesses blood flow changes by measuring an index of Hb concentration (IHB) and index of Hb oxygen saturation (ISO2). We tested the following hypotheses: 1) endoscopic RS measurements obtained by two observers and with the aid of fiber optic and video endoscopes are similar, and 2) the method is suitable for documenting mesenteric venoconstriction associated with systemic hypoxia and blood flow autoregulation associated with hemorrhagic hypotension.METHODS:Study 1: two investigators obtained baseline gastric mucosal RS measurements in anesthetized rats (n = 3) before and after stepwise reduction of blood pressure induced by arterial hemorrhage. Study 2: subjects were examined by both fiber optic and video endoscopes. Endoscopic RS measurements were obtained at 20 cm from the anal verge. Study 3: video endoscope was used to obtain RS measurements in oxygen-dependent patients on and off oxygen treatment. Study 4: the procedures in study 1 were repeated in five additional rats by one of the investigators.RESULTS:Study 1: there was good agreement between the measurements of IHB and ISO2 between the two investigators. Study 2: video endoscope-assisted measurements were consistently lower. Study 3: cessation of oxygen treatment produced a significant drop in oxygen saturation (pulse oximetry), decline in ISO2, and rise in IHB. Study 4: when blood pressure varied between 90% and 40% of baseline, gastric mucosal blood flow (IHB) was maintained at ∼70% of baseline level.CONCLUSIONS:We confirmed that reproducible measurement can be obtained by different investigators using standardized techniques. Standardization of endoscopic equipment is also necessary to overcome the significant limitation of endoscopic equipment on RS measurements. RS measurements can document mesenteric venoconstriction associated with systemic hypoxia and blood flow autoregulation associated with hemorrhagic hypotension.

[1]  H. Fusamoto,et al.  Gastric mucosal hemodynamics after thermal or head injury. A clinical application of reflectance spectrophotometry. , 1982, Gastroenterology.

[2]  H. Fusamoto,et al.  Gastric mucosal blood distribution and its changes in the healing process of gastric ulcer. , 1983, Gastroenterology.

[3]  F. Leung,et al.  Endoscopic assessment of blood flow in duodenal ulcers. , 1994, Gastrointestinal endoscopy.

[4]  S. Lo,et al.  Factors influencing reflectance spectrophotometric measurements of gastrointestinal mucosal blood flow. , 1995, Gastrointestinal endoscopy.

[5]  S. Chung,et al.  Endoscopic assessment of mucosal hemodynamic changes in a canine model of gastric ulcer. , 1991, Gastrointestinal Endoscopy.

[6]  F. Leung,et al.  Regional differences in mucosal hemodynamics in experimental colonic injury in rats , 1993, Digestive Diseases and Sciences.

[7]  J. Bosch,et al.  Effects of propranolol on gastric mucosal perfusion in cirrhotic patients with portal hypertensive gastropathy , 1993, Hepatology.

[8]  F. Leung,et al.  Gastroduodenal mucosal hemodynamics by endoscopic reflectance spectrophotometry. , 1987, Gastrointestinal endoscopy.

[9]  Z. Bosnjak,et al.  Isoflurane-Mediated Inhibition of the Constriction of Mesenteric Capacitance Veins and Related Circulatory Responses to Acute Graded Hypoxic Hypoxia , 1995, Anesthesia and analgesia.

[10]  K. Konishi,et al.  Rectal mucosal hemodynamics, evaluated by reflectance spectrophotometry, in patients with chronic hepatitis , 1998, Journal of Gastroenterology.

[11]  T. Kamada,et al.  Measurement of hemoperfusion and oxygen sufficiency in gastric mucosa in vivo. Evidence of mucosal hypoxia as the cause of hemorrhagic shock-induced gastric mucosal lesion in rats. , 1979, Gastroenterology.

[12]  M. Nicholls,et al.  Reproducible demonstration of blood flow at duodenal ulcer margins by endoscopic reflectance spectrophotometry. , 1991, Gastrointestinal endoscopy.

[13]  M. Itoh,et al.  Role of blood flow in gastric and duodenal mucosal injury in the rat. , 1985, Gastroenterology.

[14]  J. Llach,et al.  Gastric intramucosal acidosis in mechanically ventilated patients: role of mucosal blood flow. , 1998, Critical care medicine.

[15]  K. Mitamura,et al.  Evaluation of rectal mucosal hemodynamics in patients with liver cirrhosis using reflectance spectrophotometry. , 1997, American Journal of Gastroenterology.

[16]  F. Leung,et al.  Assessment of mucosal hemodynamics in normal human colon and patients with inflammatory bowel disease. , 1989, Gastrointestinal endoscopy.

[17]  F. Leung.  Role of capsaicin-sensitive afferent nerves in mucosal injury and injury-induced hyperemia in rat colon. , 1992, The American journal of physiology.

[18]  J. Rodés,et al.  Increased gastric mucosal perfusion in cirrhotic patients with portal hypertensive gastropathy. , 1992, Gastroenterology.

[19]  F. Leung,et al.  Endoscopic demonstration that vasopressin but not propranolol produces gastric mucosal ischemia in dogs with portal hypertension. , 1988, Gastrointestinal endoscopy.

[20]  Z. Bosnjak,et al.  The inhibitory effect of halothane on mesenteric venoconstriction and related reflex responses during acute graded hypoxia in rabbits. , 1992, Anesthesiology.

[21]  K. Hirabayashi,et al.  Octreotide decreases canine gastric mucosal blood flow: a controlled assessment by endoscopic reflectance spectrophotometry. , 1994, Gastrointestinal endoscopy.

[22]  S. Targan,et al.  Inflammatory Bowel Disease: From Bench to Bedside , 1994 .

[23]  E. Livingston,et al.  Reflectance spectrophotometry for the assessment of gastroduodenal mucosal perfusion. , 1987, The American journal of physiology.

[24]  A. García Gil,et al.  [Ischemic colitis]. , 1981, Revista espanola de las enfermedades del aparato digestivo.

[25]  Z. Bosnjak,et al.  Sympathetic and Mesenteric Venous Responses to Baroreceptor or Chemoreceptor Stimulation during Epidural Anesthesia in Rabbits , 1996, Anesthesiology.