Marc Ritz

Delayed gastric emptying in ventilated critically ill patients: Measurement by 13C-octanoic acid breath test

ObjectiveTo measure gastric emptying in ventilated critically ill patients with a new noninvasive breath test. DesignSingle-center, open study. SettingCombined medical and surgical intensive care unit of a university hospital. SubjectsThirty unselected mechanically ventilated critically ill patients receiving gastric feeding and 22 healthy volunteers. InterventionsNone. PatientsAfter 4 hrs without feeding, intragastric infusion of 100 mL of a liquid meal (Ensure) labeled with 100 &mgr;L 13C-octanoic acid. End-expiratory breath samples were collected into evacuated tubes from the respirator circuit every 5 mins for the first hour, then every 15 mins for 3 hrs. End-expiratory breath samples were also collected from volunteers studied supine after an overnight fast following an identical infusion via a nasogastric tube. Breath 13CO2 was measured with an isotope ratio mass spectrometer. Measurements and Main Results Performance of the breath test posed no difficulty or interference with patient care. The CO2 level was >1% in 1297/1300 breath samples, indicating satisfactory end-expiratory timing. Data are median and interquartile range. Gastric emptying was slower in patients compared with volunteers: gastric emptying coefficient 2.93 (2.17–3.39) vs. 3.58 (3.18–3.79), p < .001 and gastric half emptying time, derived from the area under the 13CO2 curve, 155 min (130–220) vs. 133 min (120–145), p < .008. Fourteen of the 30 patients had a gastric emptying coefficient <95% of all volunteers and 11 had a gastric half emptying time longer than 95% of all volunteers. The Acute Physiology and Chronic Health Evaluation (APACHE II) score (median 22, range 13–43) either at admission or on the day of the study did not correlate with gastric emptying coefficient. ConclusionGastric emptying of a calorie-dense liquid meal is slow in 40% to 45% of unselected mechanically ventilated patients in a combined medical and surgical intensive care unit. The 13C-octanoic acid breath test is a novel and useful bedside technique to measure gastric emptying in these patients.

Impacts and patterns of disturbed gastrointestinal function in critically ill patients

Disordered upper gastrointestinal tract motility occurs frequently in intensive care unit patients and often represents a substantial treatment challenge. In addition to specific complications such as pulmonary aspiration and diarrhea, abnormal gastrointestinal motility is a limiting factor for delivery and success of enteral nutrition. The pathophysiologies involved are incompletely understood because of the difficulties of making measurements of gastrointestinal function in critically ill patients. With the recent development of techniques that overcome some of these difficulties, the prospects are brighter for significant advances in this field.

Effects of rapid permissive hypercapnia on hemodynamics, gas exchange, and oxygen transport and consumption during mechanical ventilation for the acute respiratory distress syndrome.

ObjectiveTo measure the effects of rapid permissive hypercapnia on hemodynamics and gas exchange in patients with acute respiratory distress syndrome (ARDS).DesignProspective study.Setting: 18-bed, medical intensive care unit, university hospital.Patients11 mechanically ventilated ARDS patients.InterventionPatients were sedated and ventilated in the controlled mode. Hypercapnia was induced over a 30–60 min period by decreasing tidal volume until pH decreased to 7.2 and/or P50 increased by 7.5 mmHg. Settings were then maintained for 2 h.ResultsMinute ventilation was reduced from 13.5±6.1 to 8.2±4.1l/min (mean±SD), PaCO2 increased (40.3±6.6 to 59.3±7.2 mmHg), pH decreased (7.40±0.05 to 7.26±0.05), and P50 increased (26.3±2.02 to 31.1±2.2 mmHg) (p<0.05). Systemic vascular resistance decreased (865±454 to 648±265 dyne·s·cm−5, and cardiac index (CI) increased (4±2.4 to 4.7±2.4 l/min/m2) (p<0.05). Mean systemic arterial pressure was unchanged. Pulmonary vascular resistance was unmodified, and mean pulmonary artery pressure (MPAP) increased (29±5 to 32±6 mmHg,p<0.05). PaO2 remained unchanged, while saturation decreased (93±3 to 90±3%,p<0.05), requiring an increase in FIO2 from 0.56 to 0.64 in order to maintain an SaO2>90%. PvO2 increased (36.5±5.7 to 43.2±6.1 mmHg,p<0.05), while saturation was unmodified. The arteriovenous O2 content difference was unaltered. Oxygen transport (DO2) increased (545±240 to 621±274 ml/min/m2,p<0.05), while the O2 consumption and extraction ratio did not change significantly. Venous admixture (Qva/Qt) increased (26.3±12.3 to 32.8±13.2,p<0.05).ConclusionsThese data indicate that acute hypercapnia increases DO2 and O2 off-loading capacity in ARDS patients with normal plasma lactate, without increasing O2 extraction. Whether this would be beneficial in patients with elevated lactate levels, indicating tissue hypoxia, remains to be determined. Furthermore, even though hypercapnia was well tolerated, the increase in Qva/Qt, CI, and MPAP should prompt caution in patients with severe hypoxemia, as well as in those with depressed cardiac function and/or severe pulmonary hypertension.

Additive beneficial effects of the prone position, nitric oxide, and almitrine bismesylate on gas exchange and oxygen transport in acute respiratory distress syndrome

OBJECTIVE To test the hypothesis that prone position ventilation, nitric oxide, and almitrine bismesylate, each acting by a different mechanism to improve arterial oxygenation, could exert additive beneficial effects when used in combination in patients with severe acute respiratory distress syndrome (ARDS). DESIGN Prospective, nonrandomized, interventional study. SETTING Medical and surgical intensive care units at a university tertiary care center. PATIENTS Twelve patients with ARDS and severe hypoxemia, defined as PaO2/FIO2 of < or = 150 and FIO2 of > or = 0.6, with pulmonary artery occlusion pressure of < 18 mm Hg. INTERVENTIONS Inhaled nitric oxide (20 parts per million for 15 mins) in the supine and prone position, and intravenous almitrine bismesylate while prone (1 mg/kg/hr for 60 mins), alone or combined with nitric oxide. MEASUREMENTS AND MAIN RESULTS Hemodynamic, blood gas, and gas exchange measurements were performed at sequential time points as follows: a) baseline supine; b) nitric oxide in the supine position; c) after return to baseline supine; d) after 30 mins prone; e) after 120 mins prone; f) nitric oxide while prone; g) after return to baseline prone; h) almitrine bismesylate prone; and i) nitric oxide and almitrine bismesylate combined, for 15 mins prone. Patients were considered responders to the prone position if a gain in PaO2 of > or = 10 torr (> or = 1.3 kPa) or a gain in the PaO2/FIO2 ratio of > or = 20 was observed. Seven patients (58%) responded to being turned prone. Compared with supine baseline conditions, nitric oxide and supine position increased arterial oxygen saturation from 89 +/- 1 (SD)% to 92 +/- 3% (p < .05) and nitric oxide plus prone position increased arterial oxygen saturation (94 +/- 3% vs. 89 +/- 4%, p < .05) and decreased the alveolar-arterial oxygen difference from 406 +/- 124 torr (54 +/- 15 kPa) to 387 +/- 108 torr (51 +/- 14 kPa) (p < .05). Almitrine bismesylate increased PaO2/FIO2 vs. baseline (122 +/- 58 vs. 84 +/- 21, p < .05). Almitrine bismesylate decreased the alveolar-arterial oxygen difference vs. baseline from 406 +/- 124 torr (53.9 +/- 16.5 kPa) to 386 +/- 112 torr (51.3 +/- 14.8 kPa) and vs. nitric oxide and supine position from 406 +/- 111 torr (53.9 +/- 14.7 kPa) to 386 +/- 112 torr (51.3 +/- 14.8 kPa) (p < .05). Prone position alone did not improve oxygenation. However, the combination of nitric oxide and almitrine bismesylate increased PaO2/FIO2 vs. nitric oxide supine and nitric oxide prone conditions (147 +/- 69 vs. 84 +/- 25 and 91 +/- 18, respectively; p < .05). In patients responding to the prone position (n = 7), combining nitric oxide and almitrine bismesylate led to further improvement in PaO2 compared with the prone position alone, with PaO2 increasing from 78 +/- 12 torr (10.3 +/- 1.6 kPa) to 111 +/- 55 torr (14.7 +/- 7.3 kPa) (p < .05), which was not the case when either nitric oxide or almitrine bismesylate was added separately. Heart rate and cardiac output were increased by almitrine bismesylate compared with all other measurements. Mean pulmonary arterial pressure was decreased by nitric oxide (27 +/- 7 vs. 30 +/- 7 mm Hg nitric oxide supine vs. baseline supine and 29 +/- 7 vs. 33 +/- 8 mm Hg nitric oxide prone vs. baseline prone, p < .05) and increased by almitrine bismesylate (36 +/- 9 vs. 30 +/- 7 mm Hg baseline supine, 27 +/- 7 mm Hg nitric oxide supine, 33 +/- 8 mm Hg baseline prone, and 29 +/- 7 mm Hg nitric oxide prone; p < .05). The increase in mean pulmonary arterial pressure was totally abolished by nitric oxide (31 +/- 5 vs. 36 +/- 9 mm Hg, p < .05). Minute ventilation, respiratory system compliance, physiologic deadspace, and PaCO2 remained unchanged. CONCLUSION In ARDS patients with severe hypoxemia, arterial oxygenation can be improved by combining the prone position, nitric oxide, and almitrine bismesylate, without deleterious effects.

Evaluation of the 13C‐triolein breath test for fat malabsorption in adult patients with cystic fibrosis

Background and Aims: A simple non‐invasive test not requiring the use of radioactive isotopes is required to assess fat malabsorption in adult cystic fibrosis (CF) patients. Breath tests using substrates labeled with 13C meet these conditions. The 14C‐triolein breath test is sensitive and specific for measuring fat malabsorption, but involves radiation exposure. The aim of this study was to examine the utility of a test using a 13C label and to determine whether pancreatic replacement therapy would return the test to the values of a normal control group.

The effect of acute hyperglycaemia on appetite and food intake in Type 1 diabetes mellitus

Aims  To determine the effects of acute hyperglycaemia on appetite and food intake in Type 1 diabetes mellitus.

Effects of inhaled salmeterol and salbutamol (albuterol) on morning dips compared in intensive care patients recovering from an acute severe asthma attack.

Objective: To assess the effect of a long-acting inhaled β2-agonist, salmeterol (SM), compared to a short-acting inhaled β2-agonist, salbutamol (or albuterol, SB), on the occurrence of morning dip (MD) in patients recovering from an acute severe asthma attack (ASA).Design: Prospective study Setting: 18-bed, medical intensive care unit (ICU) in a university hospital.Patients: 19 patients suffering from an ASA.Interventions: Serial measurements of the peak expiratory flow rate (PEFR), arterial blood gases, vital capacity and forced expiratory volume in one second (FEV1) were performed from admission. All patients were first treated with i. v. methyl prednisolone and i.v. SB. Once the PEFR was stable and > 35 % of predicted value, i. v. SB was stopped while i. v. steroids were maintained, and patients were randomised to either inhaled SB (9 patients, 400 μg every 4 h) or inhaled SM (10 patients, 100 μg every 12 h).Results: The mean admission PEFR was 26.1 ± 11.7 % of the predicted value and was not different between the two groups. MD was more frequent with SB (6/9 patients) than with SM (4/10). The severity of MD, expressed in 1/min fall in PEFR, was higher in SB than in SM (106 ± 25 vs 55±37;p<0.05).Discussion: MD is frequent in ASA. In ASA, SM appears to reduce the frequency and the severity of MD more than SB. The clinical implications of this observation, particularly a lowering of mortality and a shortening of the ICU stay, remain to be investigated.

Evaluation of miniature manometric techniques for the measurement of esophageal body pressure waves

Perfused miniature manometric assemblies with lumina of 0.4–0.5 mm i.d. have been developed. Reduced luminal size offers the advantages of reduced assembly bulk and increased assembly complexity with greater numbers of lumina and lower manometric infusion volumes because of a slower perfusion rate. This study investigated the recording fidelity of miniature manometric assemblies in the measurement of esophageal peristalsis.