HCl Infusion Research Articles

Comparison of electrospray and UniSpray™ ion sources with post-column hydrochloric acid infusion for 119 abuse relevant substances

Comparing the sensitivity of the Waters UniSpray™ ion source (USI) with the Waters electrospray ion source (ESI) on a Waters Xevo TQ-XS mass spectrometer with and without additional post-column infusion of low concentrated hydrochloric acid (HCl). To reduce sample volumes or increase analytical sensitivity for drugs of abuse detection in human body fluids, technological advances in mass spectrometry often target an increase in ionization efficiency. One example for this development is the USI, which claims higher ion yields and therefore higher sensitivity due to a unique geometry. Another possibility to increase sensitivity through increased ion yield is the post-column infusion of low concentrated HCl. For sensitivity comparison, we choose the, in our opinion, 119 most relevant medications and drugs of abuse. These were prepared in eleven acetonitrile solutions containing 10 analytes each and one with 9 analytes at a concentration of 1 μg/mL for each substance. For analysis, every solution was diluted 1:1000 in mobile phase A/ethylene glycol (70:30 v/v) to a concentration of 1.0 ng/mL. Solutions were analysed in triplicate on the same day interrupted by the ion source change, to decrease inter-day variations in sensitivity. Chromatographic separation was performed on a Waters 2.1 × 150 mm, 1.8 μm BEH Phenyl column kept at 60 °C on an Acquity UPLC connected to a Xevo TQ-XS detector (Waters). The standard ESI ion source or the USI ion source was mounted on the detector. Mobile phase A consisted of 20 mM ammonium formate and 0.1% formic acid (pH 3) and mobile phase B was 0.1% formic acid in methanol. Gradient elution was conducted within 6.0 min at a flow rate of 0.5 mL/min with 85% A and 15% B at the beginning and 100% B at the end. Data were acquired with the ion sources operating in the positive ionization MRM mode. Two transitions for each analyte were monitored at a constant dwell time of 10 ms over the full chromatographic run time. In an additional experiment, both ion sources were compared with additional post-column infusion of 0.0037% HCl at a flow rate of 5.0 μL/min. Injection volume was 2.0 μL in all experiments. USI provided a general gain in signal intensity (peak area): 12% ( n = 14) of the analytes showed a peak area increase up to 2-fold, 85% ( n = 101) increased between 2- and 4-fold and 3% ( n = 4) increased above 4-fold in peak area. Post-column HCl infusion with the ESI source mounted, resulted in an analyte dependent additional gain in signal intensity for 15% ( n = 18) of the analytes ranging from 2- to 21-fold. 78% ( n = 93) ranged from 0.8-fold to 2-fold. In contrast 7% ( n = 8) showed a signal decrease between 0.4-fold and 0.8-fold. The combination of USI and post-column HCl infusion resulted in an increase in peak area from 2-fold up to 62-fold compared to ESI without infusion for 91% (n = 108) of the analytes. 8% ( n = 9) where between 0.8-fold and 2-fold and 1% ( n = 2) ranged from 0.4-fold to 0.8-fold. With USI, a general improvement in analytical sensitivity under identical conditions could be achieved for all of our 119 “favorite analytes” separated in one chromatographic run. Additional post-column infusion of HCl increased sensitivity for many substances. This approach can be used very selectively when applied to certain retention time windows only. Further experiments are needed to understand how different adjustments of ESI and USI and different matrices will affect ionization. USI, especially in combination with post-column HCl infusion, is a promising tool to increase sensitivity in toxicological multi-target LC-MS/MS analysis.

Evaluation of a simultaneous adsorption device for cytokines and platelet\u2013neutrophil complexes in vitro and in a rabbit acute lung injury model

BackgroundPlatelet–neutrophil complexes (PNCs) readily migrate into tissues and induce tissue damage via cytokine or other pathogenic factors release. These actions are involved in onset and progression of acute respiratory distress syndrome (ARDS). Thus, simultaneous removal of cytokines and activated neutrophils, including PNCs by blood purification may prevent development of ARDS and enhance drug effects. The goal of this study was to examine the effect of a newly developed adsorption column (NOA-001) that eliminates cytokines and activated neutrophils in a lung injury model.ResultsAdsorption of cytokines, such as IL-8, IL-6 and HMGB-1, and PNCs was first measured in vitro. Lung injury was induced by HCl and lipopolysaccharide intratracheal infusion in rabbits ventilated at a low tidal volume (7–8 mL/kg) and PEEP (2.5 cmH2O) for lung protection. Arterial blood gas, hematologic values, plasma IL-8, blood pressure and heart rate were measured, and lung damage was evaluated histopathologically in animals treated with 8-h direct hemoperfusion with or without use of NOA-001. The in vitro adsorption rates for IL-8, IL-6, HMGB-1, activated granulocytes and PNCs were 99.5 (99.4–99.5)%, 63.9 (63.4–63.9)%, 57.6 (57.4–62.1)%, 9.9 (-4.4–21.3)% and 60.9 (49.0–67.6)%, respectively. Absorption of PNCs onto fibers was confirmed microscopically. These adsorption effects were associated with several improvements in the rabbit model. In respiratory function, the PaO2/FIO2 ratios at 8 h were 314 ± 55 mmHg in the NOA-001 group and 134 ± 41 mmHg in the sham group. The oxygenation index and PaCO2 at 8 h were 9.6 ± 3.1 and 57.0 ± 9.6 mmHg in the sham group and 3.0 ± 0.8 and 40.4 ± 4.5 mmHg in the NOA-001 group, respectively (p < 0.05). Blood pH at 8 h reached 7.18 ± 0.06 in the sham group, but was maintained at 7.36 ± 0.03 (within the normal range) in the NOA-001 group (p < 0.05). In lung histopathology, fewer hyaline membrane and inflammatory cells were observed in the NOA-001 group.ConclusionA column for simultaneous removal of cytokines and PNCs showed efficacy for improvement of pulmonary function in an animal model. This column may be effective in support of treatment of ARDS.

Effects of esophageal acid infusion vs mosapride on distension-induced secondary peristalsis in humans.

Secondary peristalsis contributes to the clearance of the refluxate from the esophagus. Acute administration of 5-hydroxytryptamine 4 (5-HT4 ) receptors agonist, mosapride or esophageal infusion of hydrochloric acid (HCl) facilitates secondary peristalsis. The aim of this study was to determine whether esophageal acid infusion and administration of mosapride had different effects on secondary peristalsis. Secondary peristalsis was performed with esophageal distension with rapid and slow air injections in 16 healthy subjects. We performed two separate sessions with HCl (0.1 N) and 40 mg oral mosapride to compare their influence on secondary peristaltic parameters. The threshold volume of secondary peristalsis was significantly lower with HCl infusion than mosapride (P = 0.01) by slow air injections. The threshold volume to generate secondary peristalsis was significantly lower with HCl infusion than mosapride (P = 0.002) by rapid air injections. More secondary peristalsis was trigged by rapid air injections after HCl infusion than mosapride (P = 0.003). Infusion of HCl or mosapride administration has similar effects on peristaltic wave amplitude and duration of primary and secondary peristalsis. Acute esophageal acid infusion can induce greater mechanosensitivity to distension-induced secondary peristalsis than 5-HT4 receptors agonist mosapride. The data suggest that acid-sensitive afferents are more likely to contribute to sensory modulation of esophageal secondary peristalsis; however, the motility aspects of secondary peristalsis are comparable between acute esophageal acidification and 5-HT4 receptors activation via mosapride.

Effects of esophageal acidification on esophageal reflexes controlling the upper esophageal sphincter.

Esophageal acid exposure can alter upper esophageal sphincter (UES) function, but the mechanism is unknown. The aim of this study was to determine the effects of esophageal acid exposure on esophago-UES relaxation (EURR) and contractile (EUCR) reflexes. Cats, decrebrate ( n = 27) or chronic ( n = 4), were implanted with electromyographic electrodes on pharynx, larynx, and esophagus. The esophagus was infused with either NaCl (0.9%) or HCl (0.1 N). The EUCR was activated by balloon distension in acute cats and slow air injection in chronic cats, and the EURR was activated by rapid air injection in both sets of cats. We found that NaCl infused for 15 or 30 min had no effect on EUCR or EURR in acute cats. HCl infused for 15, 30, or 45 min significantly ( P < 0.05) decreased the sensitivity to activate EUCR. HCl infused for 15 min significantly ( P < 0.05) increased and for 45 min significantly ( P < 0.05) decreased sensitivity to activate EURR. In chronic cats, HCl infused for 15 min/day increased sensitivity to activate EURR and decreased ( P < 0.05) sensitivity to activate EUCR after 4 days of infusion. EURR occurred spontaneously during HCl infusions on the 3rd and 4th ( P < 0.05) days of HCl infusion. We conclude that esophageal acid exposure initially sensitizes the esophagus to activation of EURR and desensitizes to activation of EUCR, but with longer exposure desensitizes to both. The alteration in sensitivity to activate EURR and EUCR caused by gastroesophageal reflux may play a role in the generation of supraesophageal reflux. NEW & NOTEWORTHY In acute studies, short-term esophageal acid exposure sensitizes esophagus to activation of esophago-upper esophageal sphincter relaxation response (EURR), whereas longer-term exposure inhibits EURR. Short- or long-term esophageal acid exposure decreases sensitivity to activation of esophago-upper esophageal sphincter contractile response (EUCR). In chronic studies, short-term esophageal acid exposure has the same effects on EURR and EUCR as occur acutely, but these effects take days to develop. Alteration in EURR and EUCR caused by gastroesophageal reflux may play a role in reflux disease.

Distribution of Fos-immunoreactive neurons in the gustatory cortex elicited by intra-oral infusion of taste solutions in conscious rats

The location of neurons in the gustatory cortex (GC) activated by intra-oral infusion of solutions in conscious rats was mapped using Fos immunohistochemistry. Groups of adult male Wistar rats (N's = 5) received an infusion of one of the following: dH2O, 0.1 or 1.0 M NaCl, 0.1 or 1.0 M sucrose, 0.32 M MSG (with 100 µM amiloride and 2.5 M inosine 5′-monophosphate), 0.03 M HCl, or 0.003 M QHCl delivered via an intra-oral cannula (0.233 ml/min for 5 min). Unstimulated control rats received no infusion. Taste reactivity (TR) behaviors were videotaped and scored. The number of Fos-immunoreactive (Fos-IR) neurons was counted in eight sections throughout the anterior-posterior extent of the GC in the medial and lateral halves of the granular (GI), dysgranular (DI), and dorsal (AID) and ventral (AIV) agranular insular cortices. Intra-oral infusion of dH2O, NaCl, or sucrose altered the number of Fos-IR neurons in only specific subareas of the GC and the effects of these tastants were concentration-dependent. For example, 1.0 M NaCl increased Fos-IR neurons in the posterior lateral AID and DI and elicited more aversive TR responses than 0.1 M NaCl. Compared to dH2O, infusions of HCl or QHCl increased the total number of Fos-IR neurons in many subareas of the GC throughout its anterior-posterior extent and increased aversive TR behaviors. Linear regression analyses suggested that neurons in the medial AID of the posterior GC may influence aversive behavioral responses to HCl and QHCl while neurons in the posterior lateral AID and DI may play a role in aversive TR responses to 1.0 M NaCl.

Hydrochloric Acid Infusion for the Treatment of Metabolic Alkalosis in Surgical Intensive Care Unit Patients.

Older reports of use of hydrochloric acid (HCl) infusions for treatment of metabolic alkalosis document variable dosing strategies and risk. This study sought to characterize use of HCl infusions in surgical intensive care unit patients for the treatment of metabolic alkalosis. This retrospective review included patients who received a HCl infusion for >8 hours. The primary end point was to evaluate the utility of common acid-base equations for predicting HCl dose requirements. Secondary end points evaluated adverse effects, efficacy, duration of therapy, and total HCl dose needed to correct metabolic alkalosis. Data on demographics, potential causes of metabolic alkalosis, fluid volume, and duration of diuretics as well as laboratory data were collected. A total of 30 patients were included, and the average HCl infusion rate was 10.5 ± 3.7 mEq/h for an average of 29 ± 14.6 hours. Metabolic alkalosis was primarily diuretic-induced (n = 26). Efficacy was characterized by reduction in the median total serum CO2 from 34 to 27 mM/L ( P < 0.001). The change in chloride ion deficit and change in apparent strong ion difference (SIDa) were not correlated with total HCl administered. There were no documented serious adverse effects related to HCl infusions. HCl was effective for treating metabolic alkalosis, and no serious adverse events were seen. In this clinical setting, the baseline chloride ion deficit and SIDa were not useful for prediction of total HCl dose requirement, and serial monitoring of response is recommended.

Airway hyperresponsiveness induced by repeated esophageal infusion of HCl in guinea pigs.

Gastroesophageal reflux is a common disorder closely related to chronic airway diseases, such as chronic cough, asthma, chronic bronchitis, and chronic obstructive disease. Indeed, gastroesophageal acid reflux into the respiratory tract causes bronchoconstriction, but the underlying mechanisms have still not been clarified. This study aimed to elucidate functional changes of bronchial smooth muscles (BSMs) isolated from guinea pigs in an animal model of gastroesophageal reflux. The marked airway inflammation, hyperresponsiveness and remodeling were observed after guinea pigs were exposed to intraesophageal HCl infusion for 14 days. In addition, contractile responses to acetylcholine (ACh), KCl, electrical field stimulation, and extracellular Ca(2+) were greater in guinea pigs infused with HCl compared with control groups. The L-type voltage-dependent Ca(2+) channels (L-VDCC) blocker, nicardipine, significantly inhibited ACh- and Ca(2+)-enhanced BSM contractions in guinea pigs infused with HCl. The Rho-kinase inhibitor, Y27632, attenuated ACh-enhanced BSM contractions in guinea pigs infused with HCl. Moreover, mRNA and protein expressions for muscarinic M2 and M3 receptors, RhoA, and L-VDCC in BSM were detected by real-time PCR and Western blot. Expressions of mRNA and protein for muscarinic M3 receptors, RhoA, and L-VDCC were greater than in BSM of HCl-infused guinea pigs, whereas levels of muscarinic M2 receptors were unchanged. We demonstrate that acid infusion to the lower esophagus and, subsequently, microaspiration into the respiratory tract in guinea pigs leads to airway hyperresponsiveness and overactive BSM. Functional and molecular results indicate that overactive BSM is the reason for enhancement of extracellular Ca(2+) influx via L-VDCC and Ca(2+) sensitization through Rho-kinase signaling.

Tu1800 Functional Connectivity of Somatosensory Cortex Is Enhanced by Acute Esophageal Acid Exposure in Rats

Earlier studies have shown the effect of acute esophageal acid exposure on cerebral cortical functional connectivity. Effect of chronic acid exposure as well as acute acid challenge in the setting of remote chronic acid exposure is not known. Aim: To determine the effect of chronic esophageal acid exposure with and without acute acid re-challenge on functional connectivity (FC) of anterior cingulate cortex (ACC). Methods: We studied two groups of adult Sprague-Dawley rats (n=11/ per group). One group had esophageal HCl infusion (0.1N, 0.1ml/min) 20 min/day for 7 consecutive days. The other group had normal saline (0.9%) infusion with similar frequency and duration. After a 7-day hiatus, each rat underwent a 6 min scan (effect of chronic remote acid exposure), followed by 10 min HCL infusion (0.1N, 0.2ml/min), followed by a 6 min scan (effect of acid re-challenge). We acquired gradient ECHO images on a 9.4T scanner. All image registrations were performed in FSL/ FLIRT and further processing and analysis was done with AFNI. We used seed-based FC analysis between ACC and the rest of brain (cingulate seeds were chosen based on prior demonstration of positive BOLD activity). FC between ACC and insula was re-studied by seeds placed in the insula based on the positive BOLD signal identified from previous studies. Two-sample independent and paired t-test were applied for between and within group analysis. Multiple comparisons were corrected with Monte-Carlo simulations (p<=0.025, cluster size of 6 voxels).Results: Compared with saline group, chronic acid group exhibited significantly reduced FC (decrease correlation coefficient (CC)) between ACC and middle cingulate (MCC), retrosplenial cortex (RSC), hippocampus, primary and secondary somatosensory (S1 and S2), Caudate Putamen (Cpu) and thalamus in the resting state. Acute acid challenge resulted in increased connectivity (increased CC) between ACC and MCC, RSC, hippocampus, S1, S2, Cpu, thalamus and primary and secondary motor area (M1/M2) in both groups, however, the magnitude of increase was significantly greater for saline compared to acid group. In contrast, the connectivity between ACC and insula significantly decreased after acute acid re-challenge in the chronic acid but not in the saline group (table)(figure) (CC: 0.38 to 0.17,P<0.05). Conclusions: Connectivity of cingulate cortex with a number of brain regions is susceptible to change by chronic and acute acid exposure. Chronic acid exposure reduces cingulate connectivity which can last for at least of 7 days. Acute acid rechallenge in the setting of remote chronic acid exposure affects cingulate connectivity differently from remote chronic acid exposure. In that, it enhances the FC and it affects additional brain regions. Effect of acid re-challenge on ACC-insula FC is opposite to that of other altered connections. Acid-induced Changes in ACC Functional Connectivity with Various Brain Regions (P<0.05)

Impairment of secondary peristalsis in Barrett’s esophagus by transnasal endoscopy-based testing

To investigate dysfunctions in esophageal peristalsis and sensation in patients with Barrett's esophagus following acid infusion using endoscopy-based testing. First, physiological saline was infused into the esophagus of five healthy subjects, at a rate of 10 mL/min for 10 min, followed by infusion of HCl. Esophageal contractions were analyzed to determine whether the contractions observed by endoscopy and ultrasonography corresponded to the esophageal peristaltic waves diagnosed by manometry. Next, using nasal endoscopy, esophageal sensations and contractions were investigated in patients with, as well as controls without, Barrett's esophagus using the same infusion protocol. All except one of the propulsive contractions identified endoscopically were recorded as secondary peristaltic waves by manometry. Patients with long segment Barrett's esophagus (LSBE) tended to have a shorter lag time than the control group, although the difference did not reach statistical significance (88 ± 54 s vs 162 ± 150 s respectively, P = 0.14). Furthermore, patients with LSBE had significantly fewer secondary contractions following the infusion of both saline and HCl than did either the control group or patients with short segment Barrett's esophagus (4.1 ± 1.2 vs 8.0 ± 2.8, P < 0.001 and 7.3 ± 3.2, P < 0.01, respectively, following saline infusion; 5.3 ± 1.2 vs 8.4 ± 2.4 and 8.1 ± 2.9 respectively, P < 0.01 for both, following infusion of HCl). Using nasal endoscopy and a simple acid-perfusion study, we were able to demonstrate disorders in secondary peristalsis in patients with LSBE.

The comparison of analgesic effects of Transdermal, Oral and Intramuscular Diclofenac Sodium in Early Postoperative Period in Laparoscopic Cholecystectomy Operations;The efficacy of various administration methods of Diclofenac Sodium in post-operative

Objective: The aim of this study was to compare the efficacy of oral, intra muscular and transdermal diclofenac sodium for pain treatment in patients undergoing laparoscopic cholecystectomy, and their effect on postoperative opioid consumption. Methods: Following informed consent, 90 ASA I-II patients scheduled for laparoscopic cholecystectomy were randomized into three groups. Group PO got oral diclofenac sodium 1 hour before the operation, Group IM 75 mg diclofenac sodium intra muscular and Group TD diclofenac sodium patch 6 hours before the operation. Patients were not premedicated. Routine anaesthesia induction was used. After the operation in post anaesthesia care unit tramadol HCl infusion was delivered by intravenous patient controlled analgesia (iv PCA). Ramsey Sedation Score (RSS), Modified Aldrete’s Score System(MASS) and Visual Analog Scale Pain Score (VAS) was used for postoperative evaluation. Postoperative opioid consumption was recorded. Results: Demographic characteristics, intraoperative and postoperative hemodynamics of the patients were similar between groups. Postoperative VAS were lower at all time points in Group IM and Group TD than in Group PO. Lowest Postoperative RSS were in Group IM and the highest were in Group PO, and the difference between groups was significant. There was no significant difference in Postoperative MASS between groups. Postoperative tramadol consumption was statistically different between groups. Tramadol consumption in Group IM and Group TD was lower than Group PO. Postoperative nausea and vomiting was not observed. Local complications related to transdermal and intra muscular applications was not reported. Conclusion: In patients undergoing ambulatory laparoscopic cholecystectomy, a noninvasive application transdermal diclofenac sodium is as effective as intramuscular diclofenac sodium and can be preferred in postoperative pain treatment.

Pumpless extracorporeal CO2removal restores normocapnia and is associated with less regional perfusion in experimental acute lung injury

Lung protective ventilation may lead to hypoventilation with subsequent hypercapnic acidosis (HA). If HA cannot be tolerated or occurs despite increasing respiratory rate or buffering, extracorporeal CO2-removal using a percutaneous extracorporeal lung assist (pECLA) is an option. We hypothesised that compensation of HA using pECLA impairs regional perfusion. To test this hypothesis we determined organ blood flows in a lung-injury model with combined hypercapnic and metabolic acidosis. After induction of lung injury using hydrochloric acid (HCl) aspiration and metabolic acidosis by intravenous HCl infusion in nine pigs, an arterial-venous pECLA device was inserted. In randomised order, four treatments were tested: pECLA shunt (1) with and (2) without HA, and clamped pECLA shunt (3) with and (4) without HA. Regional blood flows were measured with the coloured microsphere technique. HA resulted in higher perfusion in adrenal glands, spleen and parts of splanchnic area (P < 0.05) compared with normocapnia. During CO2-removal with pECLA, regional perfusion decreased to levels comparable with those without pECLA and normocapnia. Cardiac output (CO) increased during HA without a pECLA shunt and was highest during HA with a pECLA shunt compared with normocapnia. During CO2-removal with pECLA, this variable decreased but stayed higher than during normocapnia with clamped pECLA shunt (P < 0.05). In our lung-injury model, HA was associated with increased systemic and regional blood flow in several organs. pECLA provides effective CO2 removal, requiring a higher CO for perfusion of the pECLA device without improvement of regional organ perfusion.

749 Self-Administered Needleless Acupuncture Therapy to Control Dyspepsia and GERD Symptoms in Patients Diagnosed With Diabetic Gastroparesis

site) and 3 cm (distal site) above the lower esophageal sphincter both prior to and immediately after infusion of either 0.075 mol/L hydrochloric acid (HCl) or saline (sham) was infused into the distal esophagus for 30 min. Vehicle (control), ONO-8539 and pregabalin were administered subcutaneously 60 min before HCl infusion. Sedative effects were assessed by ptosis of eyelids or eye closed. The expression of EP1 receptor mRNA and protein and the concentration of PGE2 in different tissues were measured by quantitative RT-PCR, Western blotting, immunohistochemistry and ELISA methods. The following tissues in the control and sham groups (n=3 in each group) were examined: proximal and distal esophagus, dorsal root ganglion, spinal dorsal horn at T1-T5 and brainstem. Results: After distal esophageal acidification, the NT was significantly decreased at distal and proximal sites in the control group. ONO-8539 suppressed the decrease of the NT at both distal and proximal sites after acid infusion. In contrast, pregabalin (10 mg/kg) suppressed the decrease of the NT only at the proximal site. Pregabalin (30 mg/kg), but not ONO-8539, produced sedative effects in all animals. EP1 mRNA and protein were observed in all tissues. PGE2 levels were significantly higher in all tissues in the control group. Conclusions: Acid infusion to the distal esophagus induced primary and secondary hypersensitivity in monkeys. ONO-8539 prevented the development of not only secondary hypersensitivity but also primary hypersensitivity after distal esophageal acidification. The higher PGE2 levels and expression of EP1 receptor in esophageal sensory pathways following distal esophageal acidification support the mechanism of action of ONO-8539. ONO-8539 may therefore be a novel therapeutic option for controlling symptoms related to central and/or peripheral hypersensitivity in esophageal disorders. Table: Mean change in nociceptive thresholds and Incidence of sedative effects

Experimentally induced hyperchloremic and dl-lactic acidosis in calves: An attempt to study the effects of oral rehydration on acid-base status

Many diarrheic calves suffer from metabolic acidosis, which is commonly treated by oral rehydration therapy. Oral rehydration solutions can be prepared in water, milk, or milk replacer. Therefore, the aim of the study was to verify dietary effects of water- or milk replacer-based oral rehydration solutions on parameters of acid-base balance in calves with experimentally induced hyperchloremic and dl-lactate acidosis. In 12 calves, hyperchloremic or dl-lactate acidosis was induced by HCl or dl-lactic acid infusions according to protocols outlined in previous literature. Immediately after induction, the calves were fed with milk replacer or water- or milk replacer-based oral rehydration solutions, or remained fasting, respectively. Blood samples were taken to monitor acid-base status over an experimental period of 4h. Using the protocols, all calves revealed a manifest hyperchloremic or dl-lactate acidosis. Because of high infusion volumes, plasma volume was expanded and effects of feeding regimens on blood parameters were rare. Unexpected clinical aberrations occurred after repeated induction of dl-lactate acidosis: all calves developed a thrombophlebitis of the jugular vein, whereas HCl infusion had no effect on endothelium. Induction of acidosis via infusion is not suitable to study dietary effects. A protocol to induce acidosis and dehydration simultaneously is required to duplicate the metabolic conditions of diarrheic calves. In further investigations, attention should be focused on effects of d-lactate or its metabolites on endothelial tissue.

Influence of Intraluminal Acidification on Esophageal Secondary Peristalsis in Humans

Secondary peristalsis contributes to clearance of retained refluxate or material from the esophagus. The goal of our study was to investigate the effects of hydrochloric acid (HCl) on physiological characteristics of esophageal secondary peristalsis in healthy adults. After recording esophageal motility baseline for primary peristalsis, secondary peristalsis was stimulated with slow and rapid air injections in the mid-esophageal in 16 healthy subjects. Normal saline and HCl (0.1 N) were separately infused into the esophagus to test whether they had effects on secondary peristalsis. After infusion of HCl, the threshold volume to generate secondary peristalsis was significantly decreased during rapid and slow air infusions (both P < 0.05). The frequency of secondary peristalsis was increased after HCl infusion (90 % [72.5-100 %] versus 85 % [72.5-90 %], P = 0.002). Infusion of HCl significantly increased pressure wave amplitude during rapid and slow air infusions (both P < 0.05). Infusion of saline did not affect any parameters of secondary peristalsis. The occurrence of heartburn was generated in 7 of 16 subjects after infusion of HCl with an increase in visual analogue scale score (12.5). Our data show that acute esophageal acid infusion enhances sensitivity of distension-induced secondary peristalsis and enhances secondary peristaltic activity. The study supports the evidence of the presence of acid-sensitive afferents in the modulation of distension-induced secondary peristalsis in humans.

Modulation of esophageal afferent pathways by 5‐HT3 receptor inhibition

The study aims were to investigate whether neural pathways involving 5-HT3 receptors mediate: (i) distension-induced upper esophageal sphincter (UES) relaxation reflex, (ii) esophageal sensitivity to acid and electrical stimuli, and (iii) viserosomatic sensitization following acid exposure. In Study I, in a double-blind crossover trial (n = 9) esophageal sensory and pain thresholds to electrical stimulation were measured in the esophagus, midsternum, and the foot, before subjects were randomized to receive either Ondansetron (8 mg i.v.) or NaCl (0.9% w/v). HCl (0.15 mol L(-1)) was then infused into distal esophagus and electrical thresholds were reassessed. Following electrical sensory threshold testing, subjects received a second esophageal infusion of HCl to evaluate esophageal sensitivity to acid. In Study II (N = 10), frequencies of distension-induced UES relaxation responses were scored before and after treatment with Ondansetron and NaCl in a double-blind crossover trial. In Study I, ondansetron had no effect on esophageal sensitivity to HCl or acid-induced sensitization. However, blockade of 5-HT3 receptors did reduce midsternum somatic pain thresholds. Sixty minutes after esophageal acid exposure, pain thresholds were significantly lower in the ondansetron arm (mean Δ-1.36 ± 0.4 mA) when compared with NaCl (mean Δ-0.14 ± 0.58 mA) (P < 0.05). In Study II, 5-HT3 receptor blockade had no significant effect on UES relaxation reflex. This study does not support the hypothesis that in health, 5-HT3 receptors play a significant role in esophago-UES distention-induced relaxation reflex and esophageal sensitivity to acid or electrical stimulation. It does provide new evidence for involvement of 5-HT3 receptors in viscerosomatic sensitization.

Effects of clinically relevant acute hypercapnic and metabolic acidosis on the cardiovascular system: an experimental porcine study

IntroductionHypercapnic acidosis (HCA) that accompanies lung-protective ventilation may be considered permissive (a tolerable side effect), or it may be therapeutic by itself. Cardiovascular effects may contribute to, or limit, the potential therapeutic impact of HCA; therefore, a complex physiological study was performed in healthy pigs to evaluate the systemic and organ-specific circulatory effects of HCA, and to compare them with those of metabolic (eucapnic) acidosis (MAC).MethodsIn anesthetized, mechanically ventilated and instrumented pigs, HCA was induced by increasing the inspired fraction of CO2 (n = 8) and MAC (n = 8) by the infusion of HCl, to reach an arterial plasma pH of 7.1. In the control group (n = 8), the normal plasma pH was maintained throughout the experiment. Hemodynamic parameters, including regional organ hemodynamics, blood gases, and electrocardiograms, were measured in vivo. Subsequently, isometric contractions and membrane potentials were recorded in vitro in the right ventricular trabeculae.ResultsHCA affected both the pulmonary (increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR)) and systemic (increase in mean arterial pressure (MAP), decrease in systemic vascular resistance (SVR)) circulations. Although the renal perfusion remained unaffected by any type of acidosis, HCA increased carotid, portal, and, hence, total liver blood flow. MAC influenced the pulmonary circulation only (increase in MPAP and PVR). Both MAC and HCA reduced the stroke volume, which was compensated for by an increase in heart rate to maintain (MAC), or even increase (HCA), the cardiac output. The right ventricular stroke work per minute was increased by both MAC and HCA; however, the left ventricular stroke work was increased by HCA only. In vitro, the trabeculae from the control pigs and pigs with acidosis showed similar contraction force and action-potential duration (APD). Perfusion with an acidic solution decreased the contraction force, whereas APD was not influenced.ConclusionsMAC preferentially affects the pulmonary circulation, whereas HCA affects the pulmonary, systemic, and regional circulations. The cardiac contractile function was reduced, but the cardiac output was maintained (MAC), or even increased (HCA). The increased ventricular stroke work per minute revealed an increased work demand placed by acidosis on the heart.

Acid Sensitization of Esophageal Mucosal Afferents

Sensitization of esophageal chemoreceptors, either directly by intermittent acid exposure or indirectly through esophagitis-associated inflammatory mediators, is likely to be the mechanism underlying the perception of heartburn. To compare basal esophageal sensitivity with electrical stimulation and acid, and to compare the degree of acid-induced sensitization in controls and in patient groups across the entire spectrum of gastroesophageal reflux disease: erosive oesophagitis (EO), nonerosive reflux disease (NERD), and functional heartburn (FH). Esophageal sensory and pain thresholds to electrical stimulation were measured before, 30, and 60 minutes after an intraesophageal infusion of saline or HCl. Patients received a 30-minute infusion of 0.15 M HCl and controls were randomized to receive either HCl (n = 11) or saline (n = 10). After electrical sensory threshold testing, participants received another 30-minute infusion of HCl to determine whether sensitivity to acid is increased by prior acid exposure All patient groups had higher basal sensory thresholds than healthy controls (controls, 13 ± 1.4 mA; FH, 20 ± 5.1 mA; NERD, 21 ± 5.1 mA; EO, 23 ± 5.4 mA; P < 0.05). Acute esophageal acid exposure reduced sensory thresholds to electrical stimulation in FH and NERD patients (P < 0.05). The level of acid sensitivity during the first HCl infusion was comparable between all patient groups and controls. The secondary infusion caused increased discomfort in all participants (P < 0.01). This acid-induced sensitization to HCl was significantly elevated in the patient groups ( P < 0.05). (1) Esophageal acid infusion sensitizes it to subsequent electrical and chemical stimulation. (2) The acid-related sensitization is greater in gastroesophageal reflux disease than in controls and may influence in part symptom perception in this population. (3) Acid-related sensitization within the gastroesophageal reflux disease population is not dependant on mucosal inflammation.

Analysis of brain activity during visceral stimulation

Functional magnetic resonance imaging (fMRI) is a useful technology for investigating regional metabolic activity in the brain. Many experiments using fMRI have been performed, but because of variations in protocols and analytic techniques, the results vary. When a priori information of the task is known, a model-based technique, such as statistical parametric mapping, is often used for analysis. In the case of acid stimulation of the esophagus the task model is unclear, so we analyzed brain activity during an acid or isotonic saline infusion to the esophagus using independent component analysis (ICA), which does not depend on a priori information of the task. Six healthy male volunteers (29-45 years) participated in the study. A multi-lumen catheter was inserted transnasally and side-hole infusions ports were approximately 15 cm proximal to the lower esophageal sphincter. The experimental protocol was 5-min interval, 5-min saline infusion, 5-min interval, 5-min 0.1 N HCl, and a final 5-min interval. After magnetic resonance scanning, fMRI image data were analyzed using group ICA. The cerebral regions activated during the first interval, saline infusion, and HCl infusion were the thalamus, insula, cingulate gyri, temporal pole and some parts of the frontal, parietal, temporal and occipital lobes. Activation of the postcentral and precentral gyri occurred during both infusions, but was not observed during the first interval. ICA, which can show the cerebral areas activated in relation to liquid in the esophagus, may be a powerful technique for studying the brain's response to visceral stimulation.

Randomised clinical trial: pregabalin attenuates the development of acid‐induced oesophageal hypersensitivity in healthy volunteers – a placebo‐controlled study

Acid infusion in humans induces primary and secondary oesophageal hypersensitivity. The effects of pregabalin, a centrally-acting modulator of voltage-sensitive calcium channels, on development of acid-induced oesophageal hypersensitivity remain unknown. To study the effects of pregabalin on development of secondary oesophageal hypersensitivity in healthy humans. Placebo-controlled, double-blind, randomised, cross-over study of 15 healthy volunteers (six women, age 21-56 years). After oesophageal manometry, baseline pain thresholds (PTs) to proximal oesophageal electrical stimulation were determined using bipolar ring electrodes. A 30-min infusion of HCl was performed in the distal oesophagus followed by PT measurements at 30 and 90 min. This protocol was repeated after administration of pregabalin (dosing schedule: 75 mg twice daily for 3 days then 150 mg twice daily for 1 day and then 150 mg on the morning of study) or placebo. T0 PTs were similar in patients after receiving placebo or pregabalin [mean (s.d.) 32.9 mA (20.5) vs. 34.1 (15.7), P = 0.42]. Pregabalin reduced development of acid-induced hypersensitivity in the proximal oesophagus at 30 min [mean change in PT (C.I.) placebo -6.2 mA (-11.3 to +1.3) vs. pregabalin +0.20 mA (-2.7 to +3.3)] and 90 min [placebo -3.7 mA (-10.0 to +2.0) vs. pregabalin +0.7 mA (-4.7 to 7.3)] overall P = 0.001. Pregabalin reduced median visual analogue scale score for acid-induced pain (1/10 vs. placebo 3/10, P = 0.027). Pregabalin attenuates development of secondary hypersensitivity in the proximal oesophagus after distal oesophageal acidification; it may thus have a role in treatment of patients with proven oesophageal pain hypersensitivity.

Coagulation Changes to Systemic Acidosis and Bicarbonate Correction in Swine

As part of our overall interest in the mechanisms and treatment related to the development of the lethal triad of hypothermia, acidosis, and coagulopathy seen in trauma patients, the purpose of this study was to determine whether acidosis, inducible either by HCl infusion or hemorrhage/hypoventilation, leads to coagulopathy, and if correction of the acidosis will alleviate this coagulopathy. In two separate experiments, acidosis was induced in anesthetized swine by (1) HCl infusion (n = 10) or (2) hemorrhage/hypoventilation (n = 8). Arterial blood samples were taken before HCl infusion or hemorrhage (arterial pH 7.4), after HCl infusion or hemorrhage (pH 7.1), and after bicarbonate infusion to return pH to 7.4. Arterial pH and blood gases were measured every 15 minutes. Acidosis (arterial pH 7.1) led to a hypocoagulation as measured by several coagulation parameters. In both experiments, acidosis was associated with a significant decrease in the maximum strength of the clot and the rate at which the clot formed. There was a significant decrease in endogenous thrombin potential and maximum thrombin concentration after acidosis in both groups (thrombin generation assay). However, the activated clotting time, prothrombin time, and activated partial thromboplastin time were significantly elevated only in the HCl-infused group. Fibrinogen concentration and platelet count were significantly reduced in both groups after acidosis. The hypocoagulation that was induced by either hemorrhage/hypoventilation or HCl infusion was not immediately corrected after returning pH to 7.4 with bicarbonate injection. These data suggest that acidosis induced by HCl infusion or by hemorrhage/hypoventilation leads to hypocoagulation. Simple correction of the arterial pH with bicarbonate is not sufficient to correct this coagulopathy.