Gastric intramucosal pH and intraluminal PCO2 during weaning from mechanical ventilation

OBJECTIVE: To study the value of gastric intramucosal pH and gastric intraluminal PCO2 measurements to predict weaning outcome from mechanical ventilation. DESIGN: Prospective clinical study. SETTING: Intensive care medicine department of a university hospital. PATIENTS: Nineteen adult critically ill patients who were mechanically ventilated because of acute respiratory failure and were considered ready to be weaned. INTERVENTIONS: The patients were weaned with: synchronized intermittent mandatory ventilation plus positive end-expiratory pressure (SIMV+PEEP) or continuous positive airway pressure with pressure support ventilation (CPAP+PSV). A gastric tonometer was placed in all the patients. Tonometric, respiratory, and hemodynamic variables were measured during the weaning process. MEASUREMENTS: Hemodynamic variables, respiratory mechanics, pulmonary gas exchange, respiratory muscle force, spontaneous pattern of breathing, and the central control of breathing were recorded. Simultaneously, the intramucosal pH and gastric intraluminal PCO2 were measured. MAIN RESULTS: Eleven patients were successfully extubated and eight failed. The patients who failed showed higher values of mouth occlusion pressure, respiratory rate, and effective inspiratory impedance (mouth occlusion pressure/mean inspiratory flow). The intramucosal pH was initially 7.19 +/- 0.22 and decreased to 7.10 +/- 0.16 during the weaning process in patients who failed (p < .05). At the same time, the intramucosal pH showed a nonsignificant change from 7.36 +/- 0.07 to 7.32 +/- 0.07 in the patients who were successfully extubated. The intramucosal pH was statistically different when both groups were compared during the initial and the final evaluations (p < .05). For the initial evaluation, the sensitivity and specificity to predict weaning failure when the intramucosal pH was < or =7.30 were 0.88 (95% confidence interval [CI], 0.66-1) and 0.82 (95% CI, 0.59-1), respectively. The gastric intraluminal PCO2 was higher in patients who failed (p < .05). When gastric intraluminal PCO2 was . or =40 torr during the initial evaluation, weaning failure occurred with a sensitivity of 1 (95% CI, 0.31-1) and a specificity of 0.55 (95% CI, 0.26-0.84). CONCLUSIONS: Weaning failure was associated with gastric intramucosal acidosis. The intramucosal pH and gastric intraluminal PCO2 may be helpful to predict weaning outcome. Further controlled clinical trials in a larger group of patients are needed.     

Foreign body in the gastrointestinal tract: intraluminal migration of laparotomy sponge

We have reported a case of complete transluminal migration of a retained laparotomy sponge that caused repeated partial small bowel obstruction. Diagnosis was made when roentgenograms showed multiple positions of the laparotomy marker. The sponge was surgically removed. This is the 69th reported case of complete transluminal migration and distal movement of a laparotomy sponge.     

Blood in the gastrointestinal tract delays and blunts the PCO2 response to transient mucosal ischaemia

Objective: To determine whether the presence of blood in the gastrointestinal tract impairs the detection of splanchnic mucosal ischaemia by reducing the rate and magnitude of rise in gut luminal PCO₂ Design: Prospective observational study Setting: University Research Laboratory Subjects: Four adult male Wistar rats with four controls from a concurrent study Interventions: Four adult male Wistar rats were anaesthetised with sodium pentobarbitone and ventilated with oxygen and isoflurane to an initial PaCO₂ of 30–40 torr. Electrochemical-fiberoptic gas sensors inserted into silastic tubing placed in the ileal lumen measured luminal PCO₂ at 1-s intervals. Distal aortic pressure was monitored continuously. Six 2-min episodes of aortic hypotension were induced in each rat to a mean pressure of 30 mmHg by intermittent elevation of a silk sling placed around the proximal aorta. Before the last three episodes in each rat 0.75–1.0 ml blood was injected into the ileal lumen via a 25-gauge needle. Four control rats from a concurrent experiment were treated in an identical fashion except that the rats were subjected to five ischaemic episodes, and there was no intraluminal injection of blood, although a 20-gauge cannula was placed in the proximal ileal lumen Measurements and main results: The presence of blood in the lumen significantly decreased the ischaemic ΔPCO₂ response from 33 ± 8 to 15 ± 4 torr (P < 0.001) and also significantly increased the peak response time from 188 ± 12 to 227 ± 24 s (P < 0.001). The corresponding measurements in the concurrent controls differed only from the values after blood injection in the experimental group Conclusions: In this animal model the presence of intraluminal blood significantly delayed the rate and the amplitude of luminal PCO₂ increases in response to transient ischaemia. This raises questions about the validity of luminal CO₂ measurements as an indicator of splanchnic ischaemia in the presence of gastrointestinal haemorrhage. Received: 14 June 1999 Final revision received: 3 March 2000 Accepted: 9 March 2000     

Noninvasive measurement of conjunctival PCO2 with a fiberoptic sensor

A miniaturized fiberoptic PCO2 probe permits direct measurement of tissue PCO2 on nonkeratinized tissue surfaces without the heating effects produced by transcutaneous PCO2 sensors. This study of anesthetized dogs compared PCO2 measured at the palpebral conjunctiva (PcjCO2) with PaCO2 and mixed venous (PVCO2) measurements during normovolemic normotension and hypovolemic hypotension. During the control period, the average PcjCO2 was 3 +/- 1 (SEM) torr greater than PaCO2 (r = 0.98) when the latter ranged from 20 to 80 torr. There was a close association (r = 0.94) between PcjCO2 and PaCO2 when the cardiac index (CI) was greater than 2.0 L/min X m2. However, as CI decreased below this value, PcjCO2 and PaCO2 were less well correlated (r = 0.69). PcjCO2 was closely associated with PVCO2 at all stages of the experiment, both above (r = 0.95) and below (r = 0.82) a CI of 2 L/min X m2. Fiberoptic conjunctival PCO2 monitoring seems promising as a noninvasive measure of physiologic status.     

Hybrid approach with laparoscopic wall-inversion surgery and single-incision intragastric surgery for intraluminal gastrointestinal stromal tumor: A case report

Laparoscopic wedge resection (LWR) for intraluminal gastrointestinal stromal tumor (GIST) leads to excessive resection of normal gastric wall. We report a case of GIST around the cardia successfully treated with full-thickness partial resection using a hybrid approach of laparoscopic surgery and single-incision intragastric surgery (SIIGS). A 69-year-old woman had a 5 cm intraluminal GIST at the posterior wall around the cardia. Submucosal injection of glycerin and indigo carmine was performed with transoral endoscopy. Circumferential seromuscular incision followed by placement of seromuscular sutures to invert the lesion into the stomach was performed under laparoscopy. By SIIGS, resection of the inverted mucosa and retrieval of the tumor were completed. A hybrid approach consisting of laparoscopic wall-inversion surgery and SIIGS was useful for intraluminal GIST and may expand the indications for laparoscopic wall-inversion surgery by removing size limitations.     

Anaerobic skin metabolism in healthy men estimated with transcutaneous PCO2 electrode

It is shown how the anaerobic energy production of the skin may be calculated from a transcutaneous PCO2 curve obtained at 37 degrees C during arterial occlusion. Thirty healthy volunteers were studied three times. The inter-individual differences in estimated ATP production were highly significant, but the intra-individual ones were not. The grand mean of the triplicate experiments of all the 30 subjects was an ATP production rate of 0.33 mmol X l-1 X min-1. Assuming no initial metabolic acidosis or alkalosis, the estimated mean extracellular fluid pH was 7.33 before and 7.26 after 4 min of stasis.     

Overview of infection control problems: principles in gastrointestinal endoscopy

The practice of flexible gastrointestinal endoscopy has matured significantly in recent years. Unfortunately, two long-standing problems still exist: the complex physical nature inherent to the endoscopes and accessories, and user compliance with established reprocessing guidelines. Improvements have been made, but newer instruments remain comparatively fragile, expensive, and physically complex, and validated data on reprocessing specific instruments is generally lacking. The practice of flexible gastrointestinal endoscopy today, however, is demonstrably safe and beneficial, provided established practice procedures for reprocessing, with emphasis on instrument cleaning, are followed meticulously in each endoscopy center.     

Gradients de PCO2 : un reflet fiable de la perfusion macroet microcirculatoire

The increase in venous to arterial and tissue to arterial PCO₂ differences (Pv-aCO₂ and Pt-aCO₂) is a constant result found in experimental and clinical studies on circulatory failure. The value of these two gradients depends on the tissue perfusion. In patients with cardiovascular failure, an “anaerobic” CO₂ production occurs by buffering H⁺ ions produced in excess; however, this production cannot offset the simultaneous decrease in “aerobic” CO₂ production. The increase in venous and tissue CO₂ can no longer be explained by an increase in CO₂ production but rather by hypoperfusion, with lower CO₂ clearance creating an accumulation of CO₂ in the tissues and the venous system. In septic shock, the pathophysiology could associate high cardiac output after initial resuscitation and tissue perfusion heterogeneity by alteration of the microcirculation. In this situation, aPv-aCO₂ gradient < 6 mmHg (together with a SvO₂ > 70%) represents a therapeutic goal to restore the macrocirculation; however, the persistence of a high Pt-aCO₂ gradient reflects an abnormality in microcirculation with residual tissue hypoperfusion. All these points are well illustrated in the literature by several experimental and clinical studies, confirming that PCO₂ gradients reflect themacro-and microcirculatory perfusion in shock states. As easily measured in blood samples or using less and less invasive monitoring devices, their use should be promoted and popularized for daily clinical practice.     

Monitoring of clopidogrel action: comparison of methods

BACKGROUND: Clopidogrel is a potent drug for prevention of adverse effects during and after coronary intervention. Increasing experience indicates that a significant proportion of patients do not respond adequately to clopidogrel. Because failure of antiplatelet therapy can have severe consequences, there is need for a reliable assay to quantify the effectiveness of clopidogrel treatment. METHODS: Of 24 healthy volunteers admitted to the study, 18 were treated for 1 week with clopidogrel (300-mg loading dose and 75-mg maintenance dose), and 6 with placebo. Platelet function was monitored by 2 assays, based on flow cytometry and enzyme immunoassay, that measure the phosphorylation status of vasodilator-stimulated phosphoprotein (VASP) and by aggregometry, flow cytometry of P-selectin, and the platelet function analyzer at baseline, on days 1-5, and on day 9 of treatment. RESULTS: Aggregometry and VASP phosphorylation revealed a loss of platelet response to ADP within 12 h after clopidogrel intake. The phosphorylation status of VASP correlated with the inhibition of platelet aggregation. In contrast, neither P-selectin expression nor PFA-100 closure time was a clear indicator of clopidogrel effects on platelets. CONCLUSIONS: VASP phosphorylation assays are reliable for quantifying clopidogrel effects. Because the VASP assay directly measures the function of the clopidogrel target, the P2Y12 receptor, the assay is selective for clopidogrel effects rather than effects of other platelet inhibitors commonly in use.     

Pleural effusion: diagnostic value of measurements of PO2, PCO2, and pH

A review of the literature suggests that the measurement of the partial pressure of oxygen (PO2) and carbon dioxide (PCO2) and pH may provide additional diagnostic, therapeutic, and prognostic information in the management of pleural effusions. Parapneumonic effusions with a pH less than 7.2 indicate an impending empyema requiring tube thoracostomy in more than 98% of cases. A distinction between a tuberculous pleural effusion and a malignant pleural effusion of recent onset (less than two months) can frequently be made by measuring the pleural fluid pH. In 100% of reported cases, tuberculous pleural effusions have a pleural fluid pH less than 7.4, whereas over 60% of recent malignant effusions have a pleural fluid pH greater than 7.4. Generally, measurements of PO2 and PCO2 have little discriminatory value in determining cause or proper management of pleural effusions. It is recommended that proper anaerobic collection of pleural fluid for pH measurements be obtained routinely in all pleural effusions of unknown cause.     

Respiratory arterial pH and PCO2 oscillations in patients with chronic obstructive airways disease

1. Arterial pH oscillations have been monitored in vivo in patients with well defined chronic obstructive bronchitis, asthma and clinical emphysema. 2. The patients with clinical emphysema were shown to differ from those with chronic obstructive bronchitis on the basis of a number of clinical and physiological criteria. 3. Patients with asthma showed least attenuation of their pH oscillations as a group, in contrast to emphysematous patients who showed most attenuation. In patients with clinical emphysema the attenuation was relatively homogeneous. The patients with chronic obstructive bronchitis showed the full range from normal oscillations (zero attenuation) to zero (complete attenuation). 4. The amplitude and approximate rate of change of upslope of the PaCO2 oscillations in vivo were calculated, from measured pH oscillation amplitudes, using buffer slope values in vitro from Siggaard Anderson [(1962, 1963) Scandinavian Journal of Clinical and Laboratory Investigation, 14, 598-604; 15, 211-217], then dividing the PaCO2 amplitude by half the respiratory period. 5. Mean arterial PCO2 in vitro showed a very strong correlation with the downslope of the pH oscillation in vivo (calculated as for PaCO2 upslope) in patients without clinical emphysema. This correlation would be expected to some extent, owing to the logarithmic relationship of PaCO2 oscillations to pH oscillations. However, the mean arterial PCO2 also showed a very strong correlation with the upslope of the calculated PaCO2 oscillations, again excluding patients with clinical emphysema.     

Increased ileal-mucosal-arterial PCO2 gap is associated with impaired villus microcirculation in endotoxic pigs

OBJECTIVE: To investigate whether an increased ileal-mucosal-arterial PCO2 gap (delta PCO2) during hyperdynamic porcine endotoxemia is associated with impaired villus microcirculation. DESIGN: Prospective, randomized, controlled, experimental study. SETTING: Animal research laboratory. ANIMALS: Twenty-two domestic pigs. INTERVENTIONS: After baseline measurements, anesthetized and ventilated pigs received continuous i.v. endotoxin (ETX, n = 12) for 24 h or placebo (SHAM, n = 10). MEASUREMENTS AND RESULTS: Before, as well as 12 and 24 h after, the start of endotoxin or saline portal venous blood flow (QPV, ultrasound flow probe) and lactate/pyruvate ratios (L/P), the ileal-mucosal-arterial delta PCO2 (fiberoptic sensor) and bowel-wall capillary hemoglobin O2 saturation (%Hb-O2-cap, remission spectrophotometry) were assessed together with intravital video records of the ileal-mucosal microcirculation (number of perfused/heterogeneously perfused/unperfused villi) using orthogonal polarization spectral imaging (CYTOSCAN A/R) via an ileostomy. At 12 and 24 h endotoxin infusion, about half of the evaluated villi were heterogeneously or unperfused which was paralleled by a progressive significant increase of the ileal-mucosal-arterial delta PCO2 and portal venous L/P ratios, whereas QPV as well as both the mean %Hb-O2-cap and the %Hb-O2-cap frequency distributions remained unchanged. By contrast, in the SHAM-group, mucosal microcirculation was well-preserved, and none of the other parameters were influenced. CONCLUSIONS: We conclude that an increased ileal-mucosal-arterial delta PCO2 during porcine endotoxemia is related to impaired villus microcirculation. A putative contribution of disturbed cellular oxygen utilization resulting from "cytopathic hypoxia" may also assume importance.