Effect of ranitidine on gastric intramucosal pH in critically ill patients

Objective: To determine whether ranitidine a) increases the values of gastric intramucosal pH (pHi) in critically ill patients, as determined by tonometry; b) reduces the variability of these measurements. Design: Prospective, double blind, randomized, placebo-controlled study. Setting: General Intensive Care Unit of a teaching hospital. Patients: Twenty-five critically ill, mechanically ventilated patients requiring arterial catheter and nasogastric tube. Interventions: Tonometer placement; blind, random administration of intravenous ranitidine (50 mg) or placebo. Measurements and main results: Tonometer saline PCO₂ (PCO₂i), arterial blood gases, gastric juice pH and pHi were determined immediately before, and 2, 4, 6 and 8 h after, ranitidine (12 patients) or placebo (13 patients). Ranitidine significantly increased gastric juice pH, but did not affect PCO₂i or pHi; pHi was 7.34 ± 0.14 before ranitidine, and 7.30 ± 0.12, 7.31 ± 0.11, 7.31 ± 0.14 and 7.31 ± 0.12 – 2, 4, 6 and 8 h, respectively, after ranitidine administration (p = 0.55). Ranitidine did not modify the coefficients of variation of PCO₂i or pHi, either. No significant changes in gastric juice pH, PCO₂i or pHi were observed in the placebo group. Conclusions: In critically ill patients, ranitidine has no effect on pHi values, and does not increase the reproducibility of pHi measurements. Received: 24 October 1996 Accepted: 22 October 1997     

Effect of sucralfate on gastric intramucosal pH in critically ill patients

Objective: To determine whether sucralfate administration affects the tonometric measurement of gastric intramucosal pH (pHi). Design: Non-randomized observational study. Setting: General intensive care unit of a teaching hospital. Patients: Twenty critically ill, mechanically ventilated, consecutively admitted patients requiring an arterial catheter and nasogastric tube. Interventions: Tonometer placement and sucralfate administration. Measurements and main results: We simultaneously determined tonometer saline PCO₂ (PCO₂i), arterial blood gases, pH of gastric juice and pHi. These parameters were evaluated immediately before sucralfate administration, and 2 h and 4 h after. We did not detect any change in either PCO₂i or pHi after sucralfate administration (PCO₂i: basal 6.4 ± 1.7, 2 h 6.3 ± 1.7, 4 h 6.3 ± 1.7; pHi: basal 7.35 ± 0.13, 2 h 7.36 ± 0.12, 4 h 7.36 ± 0.12). Conclusions: Sucralfate does not affect the tonometric measurement of PCO₂i and pHi. Received: 21 August 1996 Accepted: 18 April 1997     

Usefulness of gastric intramucosal pH for monitoring hemodynamic complications in critically ill children

Objective: To assess the efficacy of gastric intramucosal pH for the evaluation of tissue perfusion and prediction of hemodynamic complications in critically ill children. Design: Open prospective study without controls Received: 28 January 1997 Accepted: 19 September 1997     

Gastric intramucosal PCO2 and pH variability in ventilated critically ill patients

OBJECTIVE: Gastric intramucosal PCO2 (PiCO2) and pH (pHi) are currently used as indices of the adequacy of splanchnic perfusion and as end points to guide therapeutic intervention. However, little is known about their spontaneous variability over time. The present study was designed to define the magnitude of spontaneous variability of PiCO2 and pHi in sedated medical intensive care unit (ICU) patients using an automated recirculating air tonometer and to test whether high-level positive end-expiratory pressure (PEEP) or inverse inspiratory/expiratory (I:E) ratio ventilation resulted in a greater variability than low PEEP with conventional I:E ratio ventilation. DESIGN: Prospective study. SETTING: Medical ICU in a tertiary medical center. PATIENTS: Twenty-three acute respiratory failure patients. INTERVENTIONS: After being sedated, patients were randomized to undergo pressure control ventilation at the following three settings: A, high PEEP (15 cm H2O) with conventional I:E ratio (1:2), and B, low PEEP (5 cm H2O) with inverse I:E ratio (2:1) alternately, and then C, low PEEP (5 cm H2O) with conventional I:E ratio (1:2). Each ventilation setting period lasted 1 hr. MEASUREMENTS AND MAIN RESULTS: The PiCO2 and pHi were measured at baseline (time 0), and at 15, 30, 45, and 60 mins thereafter. The corresponding coefficients of variation (CVs) of PiCO2 for overall pooled group and settings A, B, and C were 4.0%, 4.4%, 3.4%, and 4.2%, respectively. The corresponding CVs of pHi for overall pooled group and settings A, B, and C were 0.36%, 0.37%, 0.33%, and 0.4%, respectively. Analysis of variance showed no significant difference in the CVs of PiCO2 or pHi between the three settings. The 95% confidence interval is approximately +/-8% variability for PiCO2 and +/-0.7% variability for pHi. CONCLUSIONS: In critically ill medical ICU patients with stable hemodynamics, the spontaneous variability of PiCO2 or pHi are not substantial. High PEEP (15 cm H2O) and inverse ratio ventilation (2:1), which does not change the cardiac output or hemodynamics, does not contribute to increased spontaneous variability in PiCO2 or pHi.     

Tissue blood flow and oxygen transport in critically ill patients.

The theoretical and practical solutions to the problems of increasing oxygen transport are well understood. Unfortunately the quantitation of hypoxia, both as an absolute deficit and as a precise method of prognosis is not yet available. This may well be because regional hypoxia in a vital tissue cannot be mirrored in a total body measurement. In the low-flow state, oxygen delivery can be maintained by redistribution of cardiac output, reduction of oxygen uptake by ischemic tissue by reducing work load, by increasing oxygenation of the blood, or by decreasing the affinity of oxygen for hemoglobin. The latter provides for more oxygen to be delivered by a given amount of oxyhemoglobin before the tension falls to deleterious regions (about 20 torr). There is some evidence that pharmacologic doses of methylprednisolone may be beneficial in this respect.     

Intrahospital transport of critically ill patients.

Intrahospital transport of critically ill patients must be considered as part of the critical care continuum. The level of care provided must be commensurate with the severity of illness. These transfers are intensive in terms of utilization of personnel and resources. Advance preparation and optimal coordination of the transport process go a long way toward safer transfers of the critically ill.     

Systemic hemodynamics, gastric intramucosal PCO2 changes, and outcome in critically ill burn patients

OBJECTIVES: To define the hemodynamic and gastric intramucosal PCO2 (PiCO2) changes during the first 48 hrs after burn trauma and to analyze their relationship with outcome. DESIGN: Prospective, observational study in a cohort of consecutively admitted critically ill burn patients. SETTING: Intensive care burn unit in a university hospital. PATIENTS: Forty-two patients with burns covering >20% of body surface area or inhalation injury. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were monitored with an oximetric pulmonary arterial catheter and a gastric tonometer to measure PiCO2. The difference between arterial and gastric mucosal PCO2 (P[i-a]CO2) was considered indicative of gastric mucosal hypoxia. Hemodynamic and PiCO2 measurements were performed during the first 48 hrs after admission. Patients suffered burns covering 36.1% +/- 14.3% (mean +/- SD) and 45.3% +/- 21.9% of body surface area (survivors and nonsurvivors, respectively). All patients were successfully resuscitated by conventional standards. Nonsurvivors (n = 16) died a median of 17 days after admission. In univariate analysis, the presence of shock during the resuscitation phase, age, mixed venous pH, P[i-a]CO2, right atrial pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac index, systemic and pulmonary vascular resistance, left ventricular stroke work index, mixed venous oxygen saturation, and systemic oxygen delivery, consumption, and extraction ratio, measured over the first 12 hrs after admission, were significantly (p < .05) different between survivors and nonsurvivors. These differences disappeared after 12 hrs after admission. Multivariate analysis identified age, percentage body surface area burned, and oxygen delivery index (6 hrs after admission) as factors independently associated with a poor outcome. P[i-a]CO2 (12 hrs after admission) was significantly greater in patients with than in those without inhalation injury (17 +/- 13 torr [2.26 +/- 1.73 kPa] vs. 6 +/- 10 torr [0.79 +/- 1.33 kPa]; p = .005). Patients with a P[i-a]CO2 difference (6 hrs after admission) > or =10 torr (1.33 kPa) had a mortality rate of 56% vs. 25% of those patients with <10 torr (p = .044). CONCLUSIONS: Our data indicate that there are hemodynamic and biochemical changes that occur early after burn trauma that are associated with prognosis after an apparently successful resuscitation. Particularly, a hemodynamic profile characterized by systemic acidosis, low systemic blood flow, and systemic and pulmonary vasoconstriction early after trauma is associated with a poor outcome. Additionally, intestinal mucosal acidosis occurs after burn trauma, is influenced by inhalation injury, and is a variable related to outcome.     

Evaluation of oxygen consumption and resting energy expenditure in critically ill patients with systemic inflammatory response syndrome.

OBJECTIVE: To determine whether oxygen consumption VO2), CO2 production, and resting energy expenditure (REE) in critically ill patients differ in varying grades of systemic inflammatory response syndrome (SIRS). DESIGN: Prospective, clinical study. SETTING: Intensive care unit at a university hospital. PATIENTS: Twenty-six critically ill patients requiring mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 100 metabolic measurements were performed. The grade of SIRS and the Acute Physiology and Chronic Health Evaluation II score were evaluated at the time of the metabolic cart study. VO2 and REE differed among the groups inadequate for SIRS (non-SIRS), with SIRS without infection (nonseptic SIRS), and with SIRS with infection (septic SIRS) (125 +/- 37 mL/min/m2 and 855 +/- 204 kcal/day/m2, 135 +/- 33 mL/min/m2 and 948 +/- 214 kcal/day/m2, and 166 +/- 55 mL/min/m2 and 1149 +/- 339 kcal/day/m2, respectively; p < .005). Patients with septic SIRS had higher VO2 and REE than patients with non-SIRS and nonseptic SIRS. CONCLUSION: VO2 and REE differ among groups of patients with non-SIRS, nonseptic SIRS, and septic SIRS. Patients with septic SIRS have higher VO2 and REE than patients with non-SIRS or nonseptic SIRS. The present study shows that classifying patients into three grades (non-SIRS, nonseptic SIRS, and septic SIRS) is a valid predictor of metabolic stress in critically ill patients.     

Hemodynamic and oxygen transport effects of dobutamine in critically ill general surgical patients

The effects of dobutamine on hemodynamic and oxygen transport were evaluated in 43 studies on 34 critically ill general (noncardiac) surgical patients. Dobutamine, beginning at a low dose (2.5 micrograms/kg X min) significantly increased cardiac index (CI), oxygen delivery (DO2), and oxygen consumption (VO2), while decreasing mean arterial pressure, pulmonary artery and wedge pressures, and systemic and pulmonary vascular resistances; blood gases, pH, and pulmonary shunt were not significantly changed. These effects were seen in postoperative and septic patients, as well as in patients with normal, low, and high control CI. These responses were poor in terminally ill and hypovolemic patients; however, when the latter were given additional fluids, their responses were markedly improved. The hemodynamic effects of dobutamine are well known, but the DO2 and VO2 effects, which suggest improved tissue perfusion, have not been appreciated.     

Validation of an indirect calorimeter to measure oxygen consumption in critically ill patients

We tested a system of indirect calorimetry (Deltatrac Metabolic Monitor) for accuracy to measure oxygen consumption and sensitivity to detect small changes in oxygen consumption, in vitro, using a lung model simulation of ventilating patients who have stiff lungs. In vivo, we assessed reproducibility of the system to measure oxygen consumption in patients who had adult respiratory distress syndrome (ARDS) or sepsis. In vitro, oxygen consumptions of 100, 200, 300, and 500 mL/min were simulated by injecting N₂ into the lung model at 3-minute ventilations (10, 15, and 20 L/min) and at four levels of FIO₂ (0.40, 0.60, 0.70, and 0.80). After each baseline measurement, N₂ flow was increased to simulate an increase in VO₂ of 10% to 15%. At FIO₂ of 0.6 and 0.8, 15 cm H₂O of positive end-expiratory pressure (PEEP) was applied to the lung model and measurements repeated. The Deltatrac had an average error of −2.1% (range, −7% to 3%). After simulated increases in oxygen consumption, the Deltatrac detected the change with an error less than 1% in all combinations tested. Although adding PEEP to the lung model altered accuracy of measurement, error was always less than 5%. We measured oxygen consumption in 27 ventilated and sedated patients who had severe ARDS or sepsis (FIO₂, 0.60 ± 0.1; PEEP, 9 ± 3 cm H₂O; static compliance, 27 ± 12 mL/cm H₂O [mean ± SD]). Coefficient of variation for oxygen consumption was 4.6% ± 1.6%. Even at FIO₂, 0.80 coefficient of variation was less than 6%. We conclude that this system of indirect calorimetry is accurate, sensitive, and reproducible to measure VO₂ in critically ill patients.     

Hemodynamic and oxygen transport response to modified fluid gelatin in critically ill patients

The hemodynamic and oxygen transport effects of the rapid infusion of 500 ml of modified fluid gelatin, an artificial colloid widely used in Europe, were studied in a group of critically ill patients suffering from cardiovascular instability. Oxygen consumption tended to increase. There were no significant changes in heart rate, shunt fraction, or systemic vascular resistance index. There were significant increases in mean arterial pressure, pulmonary artery wedge pressure, stroke index, cardiac index, and oxygen delivery. There were significant decreases in Hgb concentration and arterial oxygen content. The overall circulatory effects of modified fluid gelatin are beneficial.     

胃黏膜pH监测对重度急性颅脑外伤患者的临床意义

目的探讨重度急性颅脑外伤患者胃黏膜pH值(pHi)及其衍生指标PgapCO2和pHgap的变化与重度急性颅脑外伤患者脑外并发症(应激性溃疡出血和多器官功能障碍综合征)及近期预后之间的关系。方法队列研究2002-11～2003-12收治的重度急性颅脑外伤患者共41例,入院予以常规治疗。用自动空气张力计法每小时测一次PgCO2,共测24h。入院当时及入院后8、16、24h测动脉血气,应用S/5监护仪自动计算胃pHi及其衍生指标PgapCO2、pHgap。将一次或一次以上胃pHi值<732者归为降低组,≥732者归为正常组。根据1周内是否存活,分为存活组和死亡组。每日观察胃液隐血。连续7d每日进行SOFA评价和MOF评分。结果胃pHi正常组23例,降低组18例。死亡12例。胃pHi降低组与正常组1周内病死率、胃液隐血阳性发生率、MODS发生率、SOFA评分和MOF评分的差别有统计意义(P<001或P<005)。存活组与死亡组的胃液隐血阳性发生率和MODS发生率的差别有统计意义(P<005和P<001)。存活组与死亡组入院时PgapCO2差别有统计意义(P<001)。入院24h两组PgCO2、PgapCO2、pHi和pHgap差别均有统计意义(P<005或P<001)。结论入院24h内胃pHi及其衍生指标PgapCO2、pHgap的异常对重度急性颅脑外伤的脑外并发症及其近期预后有预警作用。     

急诊危重患者转运的安全护理

转运是急诊危重患者抢救不可分割的重要组成部分,是救治过程不可忽略的重要环节。急诊危重患者安全转运关键在于掌握转运的指征、转运前的风险评估、转运人员的组成、转运的急救器械和药品的准备、转运前的预防处理、转运途中的观察与抢救、搬运方法是否正确、抢救预案是否有效实施及严格交接班等。     

Intrahospital transport of critically ill patients

Severe complications sometimes occur in critically ill patients during intrahospital transport. Possible causes may be inadequate ventilation, insufficient monitoring, interrupted application of vasoactive drugs, or disconnections and accidental extubation. We constructed a transport unit equipped with a respirator; capnometer; monitor to measure ECG, arterial and intracranial pressures, and temperature; and two syringe pumps that can be connected easily to the patient's bed. Gas is supplied by cylinders with oxygen and air. Electrical power is supplied by two accumulators connected to recharger and transformer devices that deliver 220 V (110 V). Since this transfer unit was introduced, we have had no unanticipated problems during intrahospital ICU patient transport.     

Acute hyperventilation increases oxygen consumption and decreases peripheral tissue perfusion in critically ill patients

PurposeThis study aimed to evaluate the effects of acute hyperventilation on central venous-to-arterial carbon dioxide tension difference (Pv-aCO₂), central venous oxygen saturation (ScvO₂), central venous-to-arterial CO₂ difference/arterial-central venous O₂ difference ratio (CO₂GAP-Ratio), and peripheral perfusion index (PI) in hemodynamically stable critically ill patients.MethodsFifty-four mechanically ventilated patients were evaluated. The cardiac index, Pv-aCO₂, ScvO₂, CO₂GAP-Ratio, PI, and arterial and venous blood gas parameters were measured in the first set of measurements. Then, alveolar ventilation was increased by raising the respiratory rate (10 breaths/min). After a 30 min hyperventilation period, the second set of measurements was recorded.ResultsAcute hyperventilation induces an increase in Pv-aCO₂ (from 3.87 ± 1.31 to 8.44 ± 1.81 mmHg, P < 0.001) and a decrease in ScvO₂(from 71.78 ± 4.82 to 66.47 ± 5.74%, P < 0.001). The CO₂GAP-Ratio was significantly increased(from 0.97 ± 0.40 to 1.74 ± 0.46, P < 0.001), and the PI showed a remarkable decrease caused by acute hyperventilation(from 1.82 ± 1.14 to 1.40 ± 0.99,P = 0.04). Hyperventilation-induced ∆_Pv-aCO₂ was negatively correlated with ∆PaCO₂(r = −0.572, P<0.001). The change in ∆_PaCO₂ was correlated with ∆_ScvO₂(r = 0.450, P<0.001). However, the left ventricular outflow tract velocity time integral (LVOT-VTI) remained unchanged during hyperventilation.ConclusionsAcute hyperventilation induced an increase in oxygen consumption and decreased peripheral tissue perfusion in patients. For critical care patients, it is necessary to pay attention to the influence of hyperventilation on peripheral tissue perfusion indices and oxygen consumption indices.     

pH homeostasis during cardiopulmonary resuscitation in critically ill patients.

We investigated the effect of repeated administration of sodium bicarbonate on acid-base balance and serum chemistry in a group of patients who developed cardiac arrest. A mixed acidosis persisted throughout the duration of resuscitation in the majority of patients in spite of the large ventilatory volume and multiple doses of bicarbonate they received. However, the repeated administration of bicarbonate prevented a severe fall in serum pH. Our study demonstrated the beneficial role of bicarbonate in the treatment of metabolic acidosis associated with cardiac arrest of prolonged duration. Analysis of our data strongly indicated that the primary factors which determine the serum pH during cardiopulmonary resuscitation are the duration of circulatory arrest, adequacy of ventilation and circulation, pH immediately before arrest, and quantity of bicarbonate administered and its volume of distribution in the various fluid and tissue compartments.     

Comparison of transcutaneous oxygen and carbon dioxide monitors in normal adults and critically ill patients.

The performance characteristics of two transcutaneous combined PO2 (tcPO2) and PCO2 (tcPCO2) sensors were compared with single tcPO2 and tcPCO2 electrodes in critically ill patients. The relationship between arterial blood gases (PaO2, PaCO2) and transcutaneous values was linear. Correlation coefficients (r) varied from 0.79 to 0.87 for tcPO2 and 0.92 to tcPCO2. The tcPO2 readings were always lower than PaO2 values, but the tcPCO2, with modified calibration of the electrodes, did not differ significantly from PaCO2. There was no significant difference of clinical importance in the performance of the three monitoring systems.     

Continuous oxygen consumption measurement during initial emergency department resuscitation of critically ill patients

A portable microcomputer-based monitoring system was adapted to permit frequent, on-line measurement of oxygen consumption (VO2) in critically ill, unstable patients in the ED during initial resuscitation. Nine adult patients were monitored with this system; they were found to have initial VO2 values that were markedly elevated, averaging 409 +/- 53 ml/min.m2. In the 11 major physiologic events which were observed in these patients, VO2 changes appropriately reflected alterations in the patients' clinical condition induced by therapeutic interventions or changes in cardiorespiratory state. This study demonstrates the feasibility of VO2 monitoring during initial resuscitation and suggests that measurement of VO2 in the ED may assist in the management of critically ill patients in this setting.     

Optimal oxygen delivery in critically ill patients

Standard hemodynamic support in septic shock is to increase pulmonary capillary wedge pressure to above 15 mmHg by volume replacement and to give inotropic support if the mean arterial pressure (MAP) is not adequate. In an attempt to decrease mortality in critically ill patients, oxygen delivery (DO₂) was increased by switching inotropic support from dobutamine alone or in combination with norepinephrine to dopamine alone, or by adding dopexamine, prostacyclin, or hypertonic saline to the treatment. DO₂ increased significantly in all patients, but the increase in DO₂ was accompanied by only a 10% increase in oxygen consumption (VO₂). The increase in VO₂ was similar in survivors and nonsurvivors and in patients with and without septic shock. The results indicate that if adequate volume and inotropic support is provided for critically ill patients, the detectable oxygen debt is small and has little effect on patient outcome. When DO₂ is adequate, factors other than a tissue oxygen deficit seem to determine patient outcome.