[Tissue oxygen saturation in the critically ill patient]. / Saturación tisular de oxígeno en el paciente crítico.

Hemodynamic resuscitation seeks to correct global macrocirculatory parameters of pressure and flow. However, current evidence has shown that despite the normalization of these global parameters, microcirculatory and regional perfusion alterations can persist, and these alterations have been independently associated with a poorer patient prognosis. This in turn has lead to growing interest in new technologies for exploring regional circulation and microcirculation. Near infra-red spectroscopy allows us to monitor tissue oxygen saturation, and has been proposed as a noninvasive, continuous and easy-to-obtain measure of regional circulation. The present review aims to summarize the existing evidence on near infra-red spectroscopy and its potential clinical role in the resuscitation of critically ill patients in shock.

[Hemodynamic monitoring in the critically patient. Recomendations of the Cardiological Intensive Care and CPR Working Group of the Spanish Society of Intensive Care and Coronary Units]. / Monitorización hemodinámica en el paciente crítico. Recomendaciones del Grupo de Trabajo de Cuidados Intensivos Cardiológicos y RCP de la Sociedad Española de Medicina Intensiva, Crítica y Unidades Coronarias.

Hemodynamic monitoring offers valuable information on cardiovascular performance in the critically ill, and has become a fundamental tool in the diagnostic approach and in the therapy guidance of those patients presenting with tissue hypoperfusion. From introduction of the pulmonary artery catheter to the latest less invasive technologies, hemodynamic monitoring has been surrounded by many questions regarding its usefulness and its ultimate impact on patient prognosis. The Cardiological Intensive Care and CPR Working Group (GTCIC-RCP) of the Spanish Society of Intensive Care and Coronary Units (SEMICYUC) has recently impulsed the development of an updating series in hemodynamic monitoring. Now, a final series of recommendations are presented in order to analyze essential issues in hemodynamics, with the purpose of becoming a useful tool for residents and critical care practitioners involved in the daily management of critically ill patients.

[Objectives of hemodynamic resuscitation]. / Objetivos de la reanimación hemodinámica.

Cardiovascular failure or shock, of any etiology, is characterized by ineffective perfusion of body tissues, inducing derangements in the balance between oxygen delivery and consumption. Impairment in oxygen availability on the cellular level causes a shift to anaerobic metabolism, with an increase in lactate and hydrogen ion production that leads to lactic acidosis. The degree of hyperlactatemia and metabolic acidosis will be directly correlated to the development of organ failure and poor outcome of the individuals. The amount of oxygen available at the tissues will depend fundamentally on an adequate level of perfusion pressure and oxygen delivery. The optimization of these two physiologic parameters can re-establish the balance between oxygen delivery and consumption on the cellular level, thus, restoring the metabolism to its aerobic paths. Monitoring variables such as lactate and oxygen venous saturations (either central or mixed) during the initial resuscitation of shock will be helpful to determine whether tissue hypoxia is still present or not. Recently, some new technologies have been developed in order to evaluate local perfusion and microcirculation, such as gastric tonometry, near-infrared spectroscopy and videomicroscopy. Although monitoring these regional parameters has demonstrated its prognostic value, there is a lack of evidence regarding to its usefulness during the resuscitation process. In conclusion, hemodynamic resuscitation is still based on the rapid achievement of adequate levels of perfusion pressure, and then on the modification of oxygen delivery variables, in order to restore physiologic values of ScvO(2)/SvO(2) and resolve lactic acidosis and/or hyperlactatemia.

Impact of goal directed basic echocardiography on diagnostic and therapeutic management in an ICU of cardiac surgery. / Impacto en el manejo diagnóstico/terapéutico de la ecocardiografía básica dirigida a objetivos concretos en una UCI de cirugía cardíaca.

OBJECTIVE: Few studies have evaluated the impact in diagnosis and therapeutic management of basic transthoracic echocardiography in postoperated cardiac surgery. The aim of our study was to evaluate the impact of basic transthoracic echocardiography in the management of this kind of patients. DESIGN: Over an 18-month period, we prospectively studied all patients admitted to a university hospital Intensive Care Unit following heart surgery. We evaluated clinically all of them to establish a diagnosis and an initial treatment. We performed basic transthoracic echocardiography for a diagnosis evaluation that was compared with clinical diagnosis. If they differed, we assessed to change treatment and evaluate the therapeutic response. We performed a descriptive analysis. RESULTS: We included 136 patients and performed 203 echocardiographies. Transthoracic echocardiography differed of initial diagnosis in 101 (49.8%) echocardiographies. In 56 of these echocardiographies (55.44%), we could give an alternative diagnosis with a change in the treatment in 30patients (53,6%). We found clinical improvement in 26 patients (86.76%) in the following 30-60minutes. CONCLUSIONS: Basic transthoracic echocardiography is useful in diagnostic and therapeutic management of postoperative cardiac surgery patients. We could not confirm the clinical diagnosis in half of the performed echocardiographies. In most patients in whom we observe a change in the diagnosis due to echocardiography, we observed a clinical improvement after changing the treatment.

Evaluation of intensivist basic training in transthoracic echocardiography in the postoperative period of heart surgery.

BACKGROUND: Transthoracic echocardiography can significantly change the management of many critical patients, and is being incorporated into many Intensive Care Units (ICU). Very few studies have examined the feasibility and impact of intensivists performing basic transthoracic echocardiography upon the management of critical patients after cardiac surgery. The present study therefore evaluates the quality of acquisition and accuracy of intensivist interpretation of basic transthoracic echocardiograms in the postoperative period of heart surgery. METHODS: Over an 8-month period we prospectively studied 148 patients within 24h after admission to a university hospital ICU following heart surgery. We performed basic transthoracic echocardiography to evaluate ventricular function, pericardial effusion, hypovolemia and mitral regurgitation. Cohen's Kappa was used to compare transthoracic echocardiograms obtained by intensivists with basic versus advanced training. Concordance on image acquisition and interpretation was evaluated. RESULTS: We analyzed data of adequate transthoracic echocardiograms in 148 patients (92.5%). Apical four-chamber view and advanced trainees obtained better quality images. Concordance was good for right and left ventricular function (kappa=0.7±0.14 and 0.87±0.05, respectively), and moderate for the remaining parameters. Interpretation concordance between basic and advanced training intensivists was good (kappa=0.73±0.05). CONCLUSIONS: Intensivists with basic training in echocardiography are capable of performing and interpreting echocardiograms in most patients during the postoperative period of heart surgery.

[Limitation of therapeutic effort: a "question for professionals or for patients as well?"]. / Limitación del esfuerzo terapéutico: "cuestión de profesionales o también de enfermos?"

Limitation of therapeutic effort (LTE) is a medical term that is not free of polemic. Thus, some hold that limitation is an expression that could be considered pejorative and believe it would be more appropriate to speak of "adjustment", in order to avoid "negative" considerations concerning patient care. Because it is not a case of "ceasing to act" but of adopting a proactive attitude that includes adding or modifying measures according to the therapeutic aims of the moment. There are numerous definitions of LTE. They usually coincide in referring to not starting or withdrawing a certain treatment in which no benefits to the patient are generated, in situations where the latter is able or unable to decide for himself. Its justification is found facing a perception of disproportion between therapeutic ends and means. Nowadays, LET is fully accredited. Its use is very frequent in the field of critical care, with positions adopted by different scientific societies that endorse it to the point of considering it a standard of quality. LTE has been dealt with from numerous perspectives in many articles and forums of debate, so it would initially seems difficult to contribute something novel concerning the issue. However, there is one question that does not seem to have been sufficiently explored: Does the decision on LTE have a purely technical character, that is to say, is it the responsibility of the professional, or should the patient also intervene, or if he/she is unable to, his/her representative?

Relationship between expired capnogram and respiratory system resistance in critically ill patients during total ventilatory support.

To examine the relationship of expired capnograms and respiratory system resistance (Rrs) in intubated critically ill patients, we consecutively studied 41 mechanically ventilated patients to (1) analyze the association between expired CO2 slope and auto-positive end-expiratory pressure (auto-PEEP), between Rrs and auto-PEEP, between Rrs and expired CO2 slope, and between Rrs and arterial minus end-tidal PCO2 gradient (PaCO2-PETCO2 gradient) and (2) to investigate the capacity of the expired CO2 slope and PaCO2-PETCO2 gradient to predict Rrs during mechanical ventilation. Regression analysis found a close correlation between Rrs and expired CO2 slope (r = 0.86; p < 0.001), between Rrs and auto-PEEP (r = 0.75; p < 0.001), and between auto-PEEP and expired CO2 slope (r = 0.74; p < 0.001). Weak correlation was found between Rrs and PaCO2-PETCO2 gradient (r = 0.48; p < 0.01). Prediction interval limits at 95 percent confidence level for Rrs are approximately +/- 7.39 cm H2O/L/s from the predicted value obtained by the regression equation, where Rrs = 11.42 + 2.28 expired CO2 slope. These observations suggest that CO2 elimination in critically ill patients is strongly modulated by lung, airway, endotracheal tube, and ventilator equipment resistances. Although continuous capnogram waveform monitoring at the bedside might be useful to assess Rrs, very accurate predictions could be done only in determinate patients.

Lack of oxygen supply dependency in patients with severe sepsis. A study of oxygen delivery increased by military antishock trouser and dobutamine.

BACKGROUND: During severe sepsis, the existence of a pathologic oxygen supply dependency remains controversial. STUDY OBJECTIVE: To evaluate the relationship between oxygen delivery (DO2) and oxygen consumption (VO2) during severe sepsis and to compare, in this respect, survivors and nonsurvivors and patients with normal or increased concentration of plasma lactate. STUDY DESIGN: Cohort analytic study. SETTING: Three European ICUs in university hospitals. PATIENTS: Seventeen mechanically ventilated patients with severe sepsis (six with high blood lactate levels) studied within the first day of diagnosis. INTERVENTIONS AND MEASUREMENTS: Pulmonary elimination of carbon dioxide, or carbon dioxide production (VCO2) and VO2 were measured by indirect calorimetry before and after two interventions designed to increase DO2 (calculated from the Fick equation): inflation of a military antishock trouser (MAST) and infusion of dobutamine. RESULTS: During MAST inflation, DO2 increased by 19% in patients with a normal concentration of plasma lactate (p < 0.01), but remained unchanged in patients with high lactate levels. During dobutamine infusion, DO2 increased in both groups by 16% (p < 0.01) and 20% (p < 0.05), respectively. In both groups, we found that the VO2 and VCO2 were not affected by either the MAST or the dobutamine-induced increase in DO2. There was no difference between survivors and nonsurvivors. CONCLUSION: There was no evidence of a pathologic oxygen supply dependency in patients with severe sepsis, even in those who had an elevated concentration of plasma lactate and in those who ultimately died. These results do not favor the conclusion that maximizing DO2 is a primary therapeutic objective in such patients.

Pressure support ventilation via face mask in acute respiratory failure in hypercapnic COPD patients.

OBJECTIVE: To test whether non-invasive ventilation via facial mask could reduce the need for tracheal intubation when mechanical ventilation must be initiated in COPD patients. DESIGN: Open prospective interventional study. SETTING: General Intensive Care Service of a County Hospital. PATIENTS: We have studied 12 COPD patients during 14 episodes of acute exacerbation of chronic respiratory failure who failed to improve with intensive medical therapy and showed impairments in severe respiratory acidosis and/or hypercapnic encephalopathy leading their attending physicians to order mechanical ventilation. INTERVENTIONS: In these circumstances, a trial of pressure-support (PS) ventilation (Servo Ventilator 900C) via facial mask Vital Signs Inc.) was performed. The level of pressure support was adjusted to obtain a tidal volume > 400 ml. If the patient deteriorated, tracheal intubation and standard mechanical ventilation were performed. MEASUREMENTS AND RESULTS: Measurements are presented as means +/- SEM. A pressure-support level of 14 +/- 3 cmH2O was used during a period of 8 +/- 4 h. Low levels of external PEEP were used in 4 patients, while it generated excessive leaks in the others. Significant differences (p < 0.05 ANOVA for repeated measures) in data obtained on admission, when patients deteriorated and after pressure support was administered were only observed in PaCO2 (68 +/- 3 versus 92 +/- 3 versus 67 +/- 3 mmHg), arterial pH (7.27 +/- 0.03 versus 7.19 +/- 0.02 versus 7.31 +/- 0.01). SaO2 (60 +/- 4 versus 86 +/- 3 versus 92 +/- 1%) and respiratory rate (35 +/- 2 versus 32 +/- 2 versus 23 +/- 1 breaths.min-1). Three patients needed intubation and one of them died in the ICU. CONCLUSION: Non-invasive ventilation (pressure-support) via face mask may reduce the need for tracheal intubation in the severe hypercapnic failure of COPD patients.

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.

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.

Hemodynamic and gas exchange responses to inhalation of nitric oxide in patients with the acute respiratory distress syndrome and in hypoxemic patients with chronic obstructive pulmonary disease.

OBJECTIVE: Inhalation of nitric oxide (NO) can improve oxygenation and decrease mean pulmonary artery pressure (MPAP) in patients with the acute respiratory distress syndrome (ARDS). It is not known whether inhaled NO exerts a similar effect in hypoxemic patients with chronic obstructive pulmonary disease (COPD). DESIGN: Prospective clinical study. SETTING: General intensive care unit in Sabadell, Spain. PATIENTS: Nine mechanically ventilated COPD patients (mean age 72 +/- 2 years; forced expiratory volume in 1 s 0.91 +/- 0.11 l) and nine ARDS patients (mean age 57 +/- 6 years; mean lung injury score 2.8 +/- 0.1). MEASUREMENTS AND RESULTS: We measured hemodynamic and gas exchange parameters before NO inhalation (basal 1), during inhalation of 10 ppm NO (NO-10), and 20 min after NO was discontinued (in basal 2) in the ARDS group. In the COPD group, these parameters were measured before NO inhalation (basal 1), during different doses of inhaled NO (10, 20, and 30 ppm), and 20 min after NO was discontinued (basal 2). A positive response to NO was defined as a 20% increment in basal arterial partial pressure of oxygen (PaO2). MPAP and pulmonary vascular resistance (PVR) decreased significantly, while other hemodynamic parameters remained unchanged after NO-10 in both groups. Basal oxygenation was higher in the COPD group (PaO2/FIO2 (fractional inspired oxygen) 190 +/- 18 mmHg) than in the ARDS group (PaO2/FIO2 98 +/- 12 mmHg), (p < 0.01). After NO-10, PaO2/FIO2 increased (to 141 +/- 17 mmHg, p < 0.01) and Qva/Qt decreased (39 +/- 3 to 34 +/- 3%, p < 0.01) in the ARDS group. There were no changes in PaO2/FIO2 and Qva/Qt when the NO concentration was increased to 30 ppm in the COPD group. In both groups, a correlation was found between basal MPAP and basal PVR, and between the NO-induced decrease in MPAP and in PVR. The NO-induced increase in PaO2/FIO2 was not correlated with basal PaO2/FIO2. In the ARDS group, six of the nine patients (66%) responded to NO and in the COPD group, two of nine (22%) (p = 0.05). CONCLUSIONS: NO inhalation had similar effects on hemodynamics but not on gas exchange in ARDS and COPD patients, and this response probably depends on the underlying disease.

Oxygen delivery in critical illness.

Oxygen consumption is physiologically dependent on DO2 below the critical DO2. Thus, patients in overt shock have physiologic dependence of VO2 on DO2. The first priority of prevention and reversal of tissue hypoxia is to balance oxygen demand and oxygen supply. Pathologic dependence of VO2 on DO2 has not yet been demonstrated convincingly in critically ill patients. Furthermore, in our opinion, contradicting results of RCTs of supernormal DO2 versus normal DO2 do not support routine maintenance of supernormal levels of DO2. Finally, we suggest that intensivists continue to assess DO2 and VO2 carefully. Global assessment of VO2 and DO2 appears inadequate to detect occult tissue hypoxia in most critically ill patients. However, research focused on regional assessment such as gastric tonometer measurement of gastric mucosal PCO2 and pH provides opportunity for safe, convenient detection of occult tissue hypoxia in critically ill patients.

[Selective pulmonary vasodilator effect of inhaled nitric oxide in a patient with pulmonary thromboembolism]. / Efecto vasodilatador pulmonar selectivo del óxido nítrico inhalado en un paciente con tromboembolismo pulmonar.

The increase in pulmonary vascular resistences in acute pulmonary thromboembolism (APT) is the consequence of anatomical obstruction and pulmonary artery constriction. The administration of inhaled nitric oxide (NO) may be therapeutically useful in acute pulmonary hypertension by APT given its limited vasodilator effect on pulmonary circulation. A patient with APT in whom this selective vasodilator effect was observed is presented. The authors suggest that the administration of inhaled NO may be a potentially beneficial coadjuvant therapy in acute pulmonary hypertension induced by APT.

Prognostic implications of tissue oxygen saturation in human septic shock.

PURPOSE: To analyze the prognostic value of tissue oxygen saturation (StO(2)) in septic shock patients with restored mean arterial pressure (MAP). METHODS: This was a prospective observational study of patients admitted to the ICU in the early phase of septic shock, after restoration of MAP. Demographic data, severity score, hemodynamics, blood lactate, acid-base status, and StO(2) were measured at inclusion followed by a transient vascular occlusion test (VOT) to obtain the StO(2)-deoxygenation (DeOx) and StO(2)-reoxygenation (ReOx) rates. Sequential organ failure assessment (SOFA) score was measured at inclusion and after 24 h. RESULTS: Thirty-three patients were studied. StO(2) was 76 ± 10%, DeOx -12.2 ± 4.2%/min, and ReOx 3.02 ± 1.70%/s. MAP showed a significant correlation with VOT-derived slopes (r = -0.4, p = 0.04 for DeOx; and r = 0.55, p < 0.01 for ReOx). After 24 h, 17 patients (52%) had improved SOFA scores. Patients who did not improve their SOFA showed less negative DeOx values at inclusion. The association between DeOx and SOFA evolution was not affected by MAP. Both DeOx and ReOx impairment correlated with longer ICU stay (r = 0.44, p = 0.05; and r = -0.43, p = 0.05, respectively). CONCLUSIONS: In a population of septic shock patients with restored MAP, impaired DeOx was associated with no improvement in organ failures after 24 h. Decrements in DeOx and ReOx were associated with longer ICU stay. DeOx and ReOx were linked to MAP, and thus, their interpretation needs to be made relative to MAP.