Laryngeal mask airway position and the risk of gastric insufflation

A potential risk of the laryngeal mask airway (LMA) is an incomplete mask seal causing gastric insufflation or oropharyngeal air leakage. The objective of the present study was to assess the incidence of LMA malpositions by fiberoptic laryngoscopy, and to determine their influence on gastric insufflation and oropharyngeal air leakage. One hundred eight patients were studied after the induction of anesthesia, before any surgical manipulations. After clinically satisfactory LMA placement, tidal volumes were increased stepwise until air entered the stomach, airway pressure exceeded 40 cm H2O, or air leakage from the mask seal prevented further increases in tidal volume. LMA position in relation to the laryngeal entrance was verified using a flexible bronchoscope. The overall incidence of LMA malpositions was 40% (43 of 108). Gastric air insufflation occurred in 19% (21 of 108), and in 90% (19 of 21) of these patients, the LMA was malpositioned. Oropharyngeal air leakage occurred in 42%, and was independent of LMA position. We conclude that clinically unrecognized LMA malposition is a significant risk factor for gastric air insufflation. Implications: Routine placement of laryngeal mask airways does not require laryngoscopy. In our study, fiberoptic verification of mask position revealed suboptimal placement in 40% of cases. Such malpositioning considerably increased the risk of gastric air insufflation.     

Search for resistances controlling canine gastric emptying of liquid meals

Previous work has indicated that a chemoselective resistance controls gastric emptying. By use of meals of glucose or oleate, which were shown to empty spontaneously from dogs' stomachs half as fast as saline, we sought to locate this resistance by studying flow under controlled pressures in various regions of the gastrointestinal tract. In intact dogs, gastric outflow of glucose or oleate rose one-third as fast as outflow of saline as gastric pressure was raised, and this increased resistance to outflow of nutrients was unaffected by truncal vagotomy and pyloroplasty. In fistula dogs, gastroduodenal outflow rose linearly with gastroduodenal pressure gradients; outflow was markedly inhibited in a dose-related manner by intestinal oleate but not glucose. Inhibition by oleate was abolished by pyloroplasty. Glucose or oleate flowed into the small bowel from a barostat only slightly slower than saline. However, there was a strong inhibition of intestinal inflow of all three meals by gastric distension, an effect unaltered by truncal vagotomy. The findings suggest that gastric emptying is controlled by complex interactions among pressures and resistances, both within and beyond the stomach.     

Reduction of crotoxin-induced neuromuscular blockade by gamma radiation

OBJECTIVES: This study evaluated the application of ultrasound (US) guidance in the percutaneous placement of gastric feeding tubes in patients in whom endoscopic placement of a nutrition tube is not possible. METHODS: Thirty-eight patients with upper gastrointestinal obstruction were entered in a prospective study with US-guided nutrition tube application. Feasibility of placement, side effects, and nutritional states were monitored for a mean follow-up of 4 months. RESULTS: Ultrasound allowed rapid puncture after filling of the stomach with water through a nasal tube in 34/38 cases. In four cases a total upper gastrointestinal obstruction required an initial stomach insufflation through a direct puncture. Puncture-related major complications were not observed. Minor complications during the observation time were one late dislocation, five cases with broken material after about 6 months (four could be changed by using the Seldinger technique), and two minor local infections. The nutrition through feeding tubes stabilized body weight and body composition parameters. CONCLUSION: The percutaneous sonographic gastrostomy (PSG) is a safe and minimally invasive procedure for enteral nutrition in all cases with upper gastrointestinal obstruction when endoscopic placement of a feeding tube is not possible. Percutaneous sonographic gastrostomy may help to stabilize the nutritional parameters and general condition in patients with malignant diseases.     

A method for radiologic-assisted gastrostomy when percutaneous endoscopic gastrostomy is contraindicated

BACKGROUND: Percutaneous endoscopic gastrostomy (PEG) has been established as a faster and safer procedure than open surgical gastrostomy. It cannot be done, however, for many patients with partially obstructing pharyngeal or esophageal carcinoma, previous gastrectomy, upper abdominal surgery, or bowel distension from distal obstruction. PATIENTS AND METHODS: We attempted percutaneous radiologic-assisted gastrostomy (RAG) in 231 patients referred for gastrostomy, 38 of whom had a relative contraindication for PEG. The procedure involves passing, under radiologic guidance, an orogastric inflation tube that contains a snare. We used a 5-inch long, 18-gauge needle to transabdominally insert a wire into the stomach, avoiding loops of bowel visualized by air contrast. Retrieving the transabdominal wire by snare allowed retrograde passage of the gastrostomy tube as done in standard PEG. RESULTS: The procedure was successful in 230 of 231 cases, including 37 of the 38 patients with contraindications. We could not gain gastric access in 1 patient with a 75% gastrectomy. Overall, 6 patients developed complications and 1 died. There was no procedure-related morbidity or mortality in the patients with contraindications to PEG who underwent successful RAG. Subsequent laparotomy indicated tube passage through the liver in 2 of these cases and small bowel mesentery in 1 case without clinical problems. We performed a percutaneous jejunostomy in the efferent limb of the gastrojejunostomy in 1 patient with a previous gastrectomy. CONCLUSION: The snare technique is simpler and faster than the usual radiologic gastropexy technique, and safer than an endoscopic procedure. It has become our procedure of choice for gaining gastric access.     

Gastric necrosis after fundoplication: a novel approach for esophageal preservation

An 11-year-old boy presented moribund, with massive abdominal distension. A Nissen fundoplication and gastrostomy tube had been established at age 2 years. After attempts to pass a nasogastric tube were unsuccessful, the old gastrostomy site was used to gain percutaneous access to the stomach resulting in release of gastric contents and stabilization of blood pressure and perfusion. During operation, massive gastric distention with gastric necrosis was found. Subtotal gastrectomy was performed with stapled closure of the distal intraabdominal esophagus and prepyloric region. Sump suction was placed in the proximal esophagus and the abdomen was drained widely. A distal esophageal perforation was apparent on postoperative day 19 confirmed by imaging and endoscopy. A nasoesophageal tube was passed into the abdomen, tied to a Jackson-Pratt drain, and the composite tube repositioned in the midesophagus allowing controlled proximal and distal drainage. Six months later, a Hunt-Laurence esophagojejunal pouch was created. At age 13, the child is clinically well, and enjoys 50% of his nutritional needs orally, with the remainder delivered overnight via tube feedings. This case describes gastric necrosis after gas bloat syndrome as a late complication of Nissen fundoplication. A novel approach to the management of distal esophageal perforation allowed preservation of a functional, intact native esophagus.     

Postoperative percutaneous endoscopic gastrostomy/jejunostomy

In order to cure complications appeared in the postoperative period two patients were treated with percutaneous endoscopic gastrostomy/jejunostomy (PEG, PEGJ) with the purpose of long-lasting enteral feeding and decompression. The indications of PEG/PEGJ were the following: external gastric fistula in one case and anastomotic leakage in one case. In the patients the PEG was located by intraoperative X-ray examination, this method was not published earlier. Regarding complications of the early postoperative period the PEG and the PEGJ are considered useful and expedient procedures with the aim of lasting enteral feeding and decompression.     

Abnormal sensitivity to duodenal lipid infusion in patients with functional dyspepsia

BACKGROUND AND OBJECTIVES: Patients with functional dyspepsia exhibit increased sensitivity to gastric distension (mechanoreceptors) and to meals rich in fat (chemoreceptors). The aim of this study was to test whether these patients were abnormally sensitive to intraduodenal lipid, and whether this stimulus altered gastric mechanosensitivity. METHODS AND DESIGN: Experiments were conducted on 10 patients and 10 healthy controls. The stomach was distended with a flaccid bag during duodenal infusion of either 10% Intralipid or 0.9% saline. Intragastric pressure was recorded continuously, and the participants were asked to report gastric sensations of fullness and discomfort. RESULTS: Intragastric pressure profiles during distension were similar in patients and controls. Lipid decreased intragastric pressure and reduced phasic contractility. Patients showed enhanced sensitivity to gastric distension compared with controls during both saline and lipid infusions. In the controls, threshold volumes for fullness and discomfort were higher during lipid than saline infusion. In the patients, the sensation of fullness occurred at lower volumes during lipid infusion, whereas discomfort occurred at similar volumes but lower intragastric pressures. Most patients experienced nausea and bloating and three patients vomited during lipid infusion, but remained asymptomatic during saline infusion. Controls reported no symptoms during either infusion. CONCLUSION: Dyspeptic patients have increased sensitivity to both gastric distension and intraduodenal lipid. In contrast to controls, lipid sensitizes their stomachs to distension.     

Effect of distension and feeding on phasic changes in human proximal gastric tone

BACKGROUND: Proximal stomach by virtue of its property of accommodation acts as a reservoir for the ingested food, but its role in emptying and the factors modulating it remain unexplored. AIM: To assess the effects of distension and of feeding on proximal gastric tone. SUBJECTS: 14 healthy volunteers with no current or past history of any gastro-intestinal symptoms. METHODS: Isobaric changes in volume of the proximal stomach were recorded both during fasting and for the first 30 minutes after a meal. RESULTS: For a given degree of distension, the mean (SEM) intragastric pressure was consistently lower, immediately after meal ingestion (9.8 (1.1), mm Hg) than during fasting (12.9 (0.6) mm Hg; p < 0.01). Proximal gastric tone was continuously variable with a frequency of fluctuation of 0.9-1.3/minute and an amplitude of 16.8 (2.2) ml, superimposed upon slower higher amplitude fluctuations in baseline tone. These variations in tone were unaffected by the degree of gastric distension or by food. CONCLUSIONS: While proximal gastric tone decreases after meal ingestions consistent with accommodation, the fluctuations in tone are not an importance factor in the modulation of nutrient emptying from the proximal stomach in the immediate postprandial period.     

Effects of surfactant proteins SP-B and SP-C on dynamic and static mechanics of immature lungs

To investigate the effects of surfactant proteins B (SP-B) and C (SP-C) on lung mechanics, we compared tidal and static lung volumes of immature rabbits anesthetized with pentobarbital sodium and given reconstituted test surfactants (RTS). With a series of RTS having various SP-B concentrations (0-0.7%) but a fixed SP-C concentration (1.4%), both the tidal volume with 25-cmH2O insufflation pressure and the static volume deflated to 5-cmH2O airway pressure increased, significantly correlating with the SP-B concentration: the former increased from 6.5 to 26.0 ml/kg (mean), and the latter increased from 6.4 to 31.8 ml/kg. With another series of RTS having a fixed SP-B concentration (0.7%) but various SP-C concentrations (0-1.4%), the tidal volume increased from 5.1 to 24.8 ml/kg, significantly correlating with the SP-C concentration, whereas the static volume increased from 3.4 to 32.0 ml/kg, the ceiling value, in the presence of a minimal concentration of SP-C (0. 18%). In conclusion, certain doses of SP-B and SP-C were indispensable for optimizing dynamic lung mechanics; the static mechanics, however, required significantly less SP-C.     

Home care triage nurse

OBJECTIVE: To determine the contribution of mechanical factors to the function of different types of fundoplication. DESIGN AND SETTING: An experimental bench-top study using abattoir-sourced pig esophagus and stomach placed on a tray. Preliminary esophageal myotomy ensured free reflux of 'intragastric fluid'. INTERVENTIONS: Anterior, posterior, and total fundoplications were performed on each of ten sets of viscera. MAIN OUTCOME MEASURES: Lower esophageal sphincter pressure was measured using a conventional esophageal manometry catheter. Intragastric pressure was measured with a single channel intragastric manometry catheter, whilst the stomach was inflated with coloured water. The maximum intragastric pressure or the pressure measured when the fundoplication yielded to gastric distension was recorded. RESULTS: All three types of fundoplication restored adequate competence to the gastroesophageal junction, although high-volume gastric infusions resulted in fundoplication yield in 4/10 anterior and 4/10 posterior fundoplications. Gastric distension resulted in fundal dilatation and consequent compression of the adjacent esophagus. Fundoplication generated a median rise of 11-13.5 mmHg in lower esophageal sphincter pressure, comparable to pressures reported in the postoperative clinical setting. Significantly greater intragastric volumes and pressures were tolerated following total fundoplication. CONCLUSIONS: This study suggests that mechanical factors could be major contributors to the ability of a fundoplication to restore gastroesophageal competence. Anterior, posterior and total fundoplications are all effective procedures.     

Temporary gastrostomy as an alternative procedure for nasogastric suction

Based on personal experience with 70 cases of temporary tube gastrostomy - used as an alternative procedure to nasogastric suction in 50 cases and as a double-purpose tube in 20 cases of radical esophagectomy - pertinent problems concerning indication, technique, advantages, and possible complications are presented. The results indicate that temporary gastrostomy is a safe procedure, reduces cardiopulmonary disorders, and increases the patient's comfort. The procedure is therefore strongly recommended for patients with poor cardiopulmonary reserve and for the age group above 60 years. Temporary gastrostomy is also indicated in younger patients, if prolonged gastric distension with the necessity of decompression is anticipated.     

Use of single percutaneous endoscopic gastrostomy in management of gastric volvulus in three patients

Gastric volvulus is a rare condition that occurs when the stomach twists either in an organoaxial or mesenteroaxial direction. In patients with recurrent episodes of volvulus, standard therapy is surgical correction. Many patients, however, are not candidates for surgical therapy because of comorbid conditions or advanced age. Our aim was to determine if the insertion of a single percutaneous gastrostomy tube placement would assist in management of gastric volvulus in patients not able to undergo surgical therapy. The alpha-loop maneuver was used to reduce gastric volvulus in three elderly patients. A percutaneous endoscopic gastrostomy tube was then inserted to prevent recurrent volvulus. Single percutaneous gastrostomy tube placement was successful in managing volvulus in these three patients. Single percutaneous endoscopic gastrostomy tube placement is a useful treatment alternative to surgery in patients requiring therapy of gastric volvulus.     

Laparoscopic gastrostomy according to Janeway

Percutaneous endoscopic gastrostomy is not suitable for all patients requiring gastrostomies. Patients with endoscopically impassable tumors require a safe and effective alternative procedure for paraesophageal alimentation. We present the surgical technique and results of the laparoscopic gastrostomy according to Janeway. Using an endoscopic stapling device a gastric tube is created from a stomach fold, led out through the trocar site, and fixed to the skin in the left upper quadrant. Via an inserted catheter enteral alimentation can be performed intermittently since the gastrostoma is continent. Between July 1995 and November 1996 laparoscopic gastrostomy was performed in 15 patients (10 male, five female) with tumors in the pharynx or esophagus. Mean operation time was 35 min. One stoma necrosis developed; the other postoperative courses were complication-free. All gastrostomies were continent. Laparoscopic gastrostomy is easy to perform and involves minimal discomfort and complications for the patient.     

Lyme disease--on the basis of our observations

We biologically assessed functions of several reconstituted surfactants with the same minimum surface tension (2-3 mN/m) as "complete" porcine pulmonary surfactant (natural surfactant) but with longer surface adsorption times. Administration of natural surfactant (adsorption time 0.29 s) into the lungs of surfactant-deficient immature rabbits brought a tidal volume of 16.1 +/- 4.4 (SD) ml/kg during mechanical ventilation with 40 breaths/min and 20 cmH2O insufflation pressure. In static pressure-volume recordings, these animals showed a lung volume of 62.4 +/- 9.7 ml/kg at 30 cmH2O airway pressure and maintained 55% of this volume when the pressure decreased to 5 cmH2O. With two reconstituted surfactants consisting of synthetic lipids or isolated lipids from porcine lungs plus surfactant-associated hydrophobic proteins (adsorption times 0.57 and 0.78 s, respectively), tidal volumes were < 38% of that with natural surfactant (P < 0.05), but static pressure-volume recordings were not different. Care is therefore needed in estimating the in vivo function of surfactant preparations from minimum surface tension or static pressure-volume measurements.     

Mucosal lesions due to gastric distension in the rat

The pathogenesis of acute gastric mucosal lesions produced by distension of the rat stomach was studied. One hour of distension with 0.1 N HCl, but not saline, produced lesions in the glandular stomach in all rats. Histologic studies revealed marked thinning of the mucosa plus thrombus formation in the ulcerated area. Gastric distension with 8 ml HCl (per 100 g body weight) produced severe lesions, 4 ml minimal lesions and 2 ml no lesions. Intragastric pressure in the 8-ml group remained above 110 mm H2O for the first 10 min. Distension with 8 ml acid/100 g body weight for just 10 min resulted in significant lesion formation. Acid distension did not cause generalized disruption of the gastric mucosal barrier to H+ back-diffusion. It appears that an intragastric pressure of over 110 mm H2O for 10 min damages the mucosa by pressure (with thinning) and ischemia (with thrombosis), resulting in decreased resistance to acid peptic digestion and consequent acute lesion formation.     

The surgical physiopathology of essential pulmonary emphysema and volume-reduction intervention

The breaking of the interalveolar septa represents, in the pathogenetic mechanism of emphysema, a final event, common to the different etiologic agents. This elementary injury causes a series of consequences, essentially of mechanic-structural type (intrapulmonary aerial spaces-confining parenchyma collapse, bronchial obstruction, dead space augmentation) on the thin and articulate bronchoalveolar architecture, whose final rearrangement determines, at least in part, the clinical picture. In short, the break of alveolar septa involves the formation of intraparenchymal aerial spaces with collapse of the confining lung; the compensatory mechanism to this situation, involves the hyperexpansion of the thoracic cage and flattening of the diaphragm, with the aim of allowing ventilation of the healthy residual parenchyma. Because of the finite capability of expansion of the thoracic cage and of the diaphragm in respect to the theoretical capability of the lung of large intraparenchymal aerial spaces formation, it is easy to imagine that emphysema can cause a serious functional respiratory deficit even before a significant quantity of pulmonary parenchyma is destroyed by the pathogenic process. It may then be hypothesized that a simple reduction of the volume of the lung, even sacrificing a part of "working" parenchyma, might allow the residual lung to come back to a normal ventilation, wholly ameliorating the respiratory exchanges. The clinically more remarkable consequence of lung volume reduction is the amelioration of ventilation mechanics with a decreased respiratory work due to the shift of the tidal volume toward values less proximal to the maximal expandability of the thoracic wall and of the diaphragm. On the other end, it is possible to anticipate an equally significant effect on bronchial obstruction, due to the more favorable matching of the compliance of the thoracic wall and that of the lung. LVRS has significant effect on the TV sharing ratio between emphysematous spaces and residual healthy parenchyma; the hyperexpansion of the residual lung in fact causes the distension of the emphysematous spaces, continuing in the natural compensatory mechanism of the emphysema. The decreased ventilation and thus re-breathing of the residual emphysematous spaces, together with the improved ventilation may ameliorate hypercapnia. Obviously no direct effects can be expected from LVRS on the conditions of the alveolar membrane and thus on gas diffusion capacity through it. The time duration of the amelioration achieved with the lung volume reduction is still to be demonstrated.     

Assessment of the progression of emphysema by quantitative analysis of spirometrically gated computed tomography images

RATIONALE AND OBJECTIVES: The authors assessed the progression of pulmonary emphysema by means of quantitative analysis of computed tomography images. METHODS: Twenty-three patients suffering from emphysema due to an alpha 1-antitrypsin deficiency, aged 45 +/- 7 years and exsmokers, were scanned twice with a 1-year time interval. At 90% of the vital lung capacity, slices with a thickness of 1.5 mm were acquired at the level of the carina and 5 cm above the carina; slices with a thickness of 1 cm were acquired 5 cm below the carina. The entire lung was scanned spirally at a respiratory status, corresponding with 75% of the total lung capacity at baseline. The mean lung densities (MLD) were calculated in an objective manner with new analytic software featuring automated detection of the lung contours. RESULTS: Mean lung densities decreased by 14.2 +/- 12.0 Hounsfield units (HU; P < 0.001) above the carina, by 18.1 +/- 14.4 HU (P < 0.001) at the carina level, by 23.6 +/- 15.0 HU (P < 0.001) below the carina, and by 12.8 +/- 22.2 HU (P < 0.01) for the entire lung. The decrease in MLD was most obvious in the lower lung lobes. For the same patient group, the annual decrease in the forced expiratory volume (FEV1) and the carbon monoxide-diffusion were 120 +/- 190 mL (P < 0.01) and 10 +/- 70 mmol/kg/minute ( P < 0.2), respectively. No significant correlation was found between the decrease in MLD and the decrease in FEV1. CONCLUSIONS: Progression of emphysema can be assessed in an objective manner based on the mean lung density (MLD), measured from computed tomography volume scans as well as from single-slice scans. Mean lung density has proved to be more sensitive than FEV1 and carbon monoxide-diffusion.     

Femoral venous flow dynamics during intraperitoneal and preperitoneal laparoscopic insufflation

BACKGROUND: Laparoscopic herniorrhaphy may be performed using an intraperitoneal or a preperitoneal approach. Anecdotal and experimental evidence indicates that alterations in lower extremity venous flow, which occur during intraperitoneal laparoscopic insufflation, may be associated with an increased risk of deep vein thrombosis. However, no study has directly compared femoral venous flow during intraperitoneal insufflation with that during preperitoneal insufflation. METHOD: In eight consecutive patients undergoing laparoscopic herniorrhaphy under general anesthesia, flow through the common femoral vein was evaluated with B-mode and color flow duplex. Pre- and intraperitoneal pressures were standardized to 10 mm Hg, and respiratory tidal volumes were standardized to 10 cc/kg. Flow measurements were taken at end expiration. Flow through the common femoral vein was measured after induction of anesthesia, during intraperitoneal insufflation, during preperitoneal insufflation, and between insufflations to ensure return to baseline. RESULTS: All patients in the study were males. Their mean age was 59 years. Mean flow in the common femoral vein was essentially identical at baseline (138 ml/min) and during preperitoneal insufflation (135 ml/min). Alternatively, mean flow in the common femoral vein was significantly reduced during intraperitoneal insufflation (65 ml/min, p = 0.02). CONCLUSIONS: Flow in the common femoral vein is significantly reduced during intraperitoneal insufflation. However, flow in the common femoral vein is not affected by preperitoneal insufflation. These data suggest that laparoscopic preperitoneal inguinal hernia repair may pose as less a risk of thromboembolic complications than laparoscopic intraperitoneal inguinal hernia repair.     

Respiratory mechanics in patients with tense cirrhotic ascites

Lung volumes are decreased by tense ascites and increase after large volume paracentesis (LVP). The overall effect of ascites and LVP on the respiratory function is poorly understood. We studied eight cirrhotic patients with tense ascites before and after LVP. Inspiratory muscle force (maximal transdiaphragmatic pressure (Pdi,max), and the lowest pleural pressure (Pp1,min)) was assessed while the patients were seated. Rib cage and abdominal volume displacements, as well as pleural and gastric pressures were measured during quiet breathing while the patients were supine. Pdi,max and Ppl,min were normal and did not change after LVP (from 84.2+/-19.7 to 85.2+/-17.0 cmH2O and from 68.3+/-19.7 to 74+/-15.9 cmH2O, respectively). The abdominal contribution to the generation of tidal volume was greater than that of the rib cage (79 vs 21%), a pattern which did not change after LVP (73 and 27%). Before LVP, tidal swings both of pleural pressure (Ppl,sw) and transdiaphragmatic pressure (Pdi,sw) were large (15.3+/-4.3 and 18.5+/-3.9 cmH2O, respectively) and the load on inspiratory muscles was increased as a consequence of elevated dynamic elastance of the lung (El,dyn) (11.4+/-2.6 cmH2O x L(-1)) and ("intrinsic") positive end-expiratory pressure (PEEPi) (4.3+/-3.5 cmH2O). LVP reduced the load on the inspiratory muscles, as shown by the significant decrease in Ppl,sw (10.6+/-2.0 cmH2O), Pdi,sw (12.8+/-3.0 cmH2O), El,dyn (10.0+/-2.0 cmH2O x L(-1)) and PEEPi (1.1+/-1.3 cmH2O). The amount of fluid removed was closely related to changes in Ppl,sw and PEEPi. We conclude that the strength of the inspiratory muscles is normal or reduced in seated cirrhotic patients. In the supine position, tense ascites results in an increase in lung elastic load and development of positive end-expiratory pressure, with a consequent overload and increased activation of inspiratory muscles. Large volume paracentesis decreases overloading and activation, but does not change the strength of the inspiratory muscles.     

Differential c-fos expression in the nucleus of the solitary tract and spinal cord following noxious gastric distention in the rat

c-Fos has been used as a marker for activity in the spinal cord following noxious somatic or visceral stimulation. Although the viscera receive dual afferent innervation, distention of hollow organs (i.e. esophagus, stomach, descending colon and rectum) induces significantly more c-Fos in second order neurons in the nucleus of the solitary tract and lumbosacral spinal cord, which receive parasympathetic afferent input (vagus, pelvic nerves), than the thoracolumbar spinal cord, which receives sympathetic afferent input (splanchnic nerves). The purpose of this study was to determine the contribution of sympathetic and parasympathetic afferent input to c-Fos expression in the nucleus of the solitary tract and spinal cord, and the influence of supraspinal pathways on Fos induction in the thoracolumbar spinal cord. Noxious gastric distention to 80 mmHg (gastric distension/80) was produced by repetitive inflation of a chronically implanted gastric balloon. Gastric distension/80 induced c-Fos throughout the nucleus of the solitary tract, with the densest labeling observed within 300 microns of the rostral pole of the area postrema. This area was analysed quantitatively following several manipulations. Gastric distension/80 induced a mean of 724 c-Fos-immunoreactive nuclei per section. Following subdiaphragmatic vagotomy plus distention (vagotomy/80), the induction of c-Fos-immunoreactive nuclei was reduced to 293 per section, while spinal transection at T2 plus distention (spinal transection/80) induced a mean of 581 nuclei per nucleus of the solitary tract section. Gastric distension/80 and vagotomy/80 induced minimal c-Fos in the T8-T10 spinal cord (50 nuclei/section), but spinal transection/80 induced 200 nuclei per section. Repetitive bolus injections of norepinephrine produced transient pressor responses mimicking the pressor response produced by gastric distension/80. This manipulation induced minimal c-Fos in the nucleus of the solitary tract and none in the spinal cord. It is concluded that noxious visceral input via parasympathetic vagal afferents, and to a lesser extent sympathetic afferents and the spinosolitary tract, contribute to gastric distention-induced c-Fos in the nucleus of the solitary tract. The induction of c-Fos in the nucleus of the solitary tract is significantly greater than in the viscerotopic segments of the spinal cord, which is partially under tonic descending inhibition, but is not subject to modulation by vagal gastric afferents. Distention pressures produced by noxious gastric distention are much greater than those produced during feeding, suggesting that c-Fos induction in the nucleus of the solitary tract to noxious distention is not associated with physiological mechanisms of feeding and satiety. The large vagal nerve-mediated induction of c-Fos in the nucleus of the solitary tract following gastric distension suggests that parasympathetic afferents contribute to the processing of noxious visceral stimuli, perhaps by contributing to the affective-emotional component of visceral pain.