Ventilación mecánica: pasado y presente / Mechanical ventilation: past and present

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The role of chronic nutritional supplements consumption in a fulminant serotonin syndrome due to citalopram intoxication / El papel del consumo crónico de suplementos nutricionales en un síndrome serotoninérgico fulminante debido a intoxicación por citalopram

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Respiratory CO2 response depends on plasma bicarbonate concentration in mechanically ventilated patients

OBJECTIVE: There is controversy about the effects of high plasma bicarbonate concentration([HCO3−]) and the CO2 response test. We analyzed the relationship between [HCO3−] and the variation in hydrogen ion concentration (pH) for a given change in PaCO2, and its effects uponCO2 response. DESIGN: A retrospective study was carried out. Setting: Two intensive care units. Patients: Subjects with and without chronic obstructive pulmonary disease (COPD), at the beginning of weaning from mechanical ventilation. Interventions: The CO2 response was evaluated by the re-inhalation of expired air method, measuring the hypercapnic ventilatory esponse (ΔVE/ΔPaCO2) and hypercapnic drive response (ΔP01/ΔPaCO2), where VE is minute volume and P0.1 is airway occlusion pressure 0.1s after the initiation of inspiration. Main outcome measures: [HCO3−] and CO2 response. RESULTS: A total of 120 patients in the non-COPD group and 48 in the COPD group were studied. COPD patients had higher mean [HCO3−] than non-COPD patients (33.2±5.4 vs. 25.7±3.7mmol/l, p < 0.001). In both non-COPD and COPD patients we observed a significant inverse linear relationship between [HCO3−] and pH change per mmHg of PaCO2 (p < 0.001), ΔVE/ΔPaCO2 (p < 0.001) and ΔP0.1/ΔPaCO2 (p < 0.001). CONCLUSIONS: There is an inverse linear relationship between [HCO3−] and the variation of pH for a given change in PaCO2 and the CO2 response

OBJETIVO: Existe controversia en si las diferencias en la concentración plasmática de bicarbonato(CO3H−) modifican la respuesta al incremento de CO2. Hemos analizado la relación entre laCO3H− y la variación en la concentración de iones de hidrógeno (pH) por un incremento agudo de la PaCO2 y entre la CO3H− y la respuesta del sistema respiratorio al incremento de CO2.Dise˜no: Estudio retrospectivo. Ámbito: Dos unidades de cuidados intensivos. Pacientes: Pacientes con y sin enfermedad pulmonar obstructiva crónica (EPOC) en el inicio de la desconexión de ventilación mecánica. Intervenciones: La respuesta del sistema respiratorio al incremento de CO2 fue evaluada por el método de reinhalación del aire espirado, midiendo la respuesta ventilatoria a la hipercapnia (ΔVE/ΔPaCO2) y la respuesta del centro respiratorio a la hipercapnia (ΔP0,1/ΔPaCO2), donde VE es el volumen minuto y P0,1 es la presión de oclusión de la vía aérea a 0,1 s del inicio de la inspiración. Variables de interés: principales CO3H− y respuesta al CO2. RESULTADOS: Fueron estudiados 120 pacientes sin EPOC y 48 con EPOC. Las CO3H− medias en los pacientes sin y con EPOC fueron de 25,7±3,7 y 33,2±5,4 mmol/L, respectivamente (p < 0,001). Hallamos, en ambos grupos de pacientes, una relación linear inversa entre la CO3H− y el cambio de pH por mmHg de PaCO2 (p < 0,001), el ΔVE/ΔPaCO2 (p < 0,001) y el ΔP0,1/ΔPaCO2 p < 0,001). CONCLUSIONES: Hay una relación linear inversa entre la CO3H− y la variación en el pH por un incremento agudo de la PaCO2 y entre la CO3H- y la respuesta al CO2

Respiratory CO2 response depends on plasma bicarbonate concentration in mechanically ventilated patients.

OBJECTIVE: There is controversy about the effects of high plasma bicarbonate concentration ([HCO3(-)]) and the CO2 response test. We analyzed the relationship between [HCO3(-)] and the variation in hydrogen ion concentration (pH) for a given change in PaCO2, and its effects upon CO2 response. DESIGN: A retrospective study was carried out. SETTING: Two intensive care units. PATIENTS: Subjects with and without chronic obstructive pulmonary disease (COPD), at the beginning of weaning from mechanical ventilation. INTERVENTIONS: The CO2 response was evaluated by the re-inhalation of expired air method, measuring the hypercapnic ventilatory response (ΔVE/ΔPaCO2) and hypercapnic drive response (ΔP01/ΔPaCO2), where VE is minute volume and P0.1 is airway occlusion pressure 0.1s after the initiation of inspiration. MAIN OUTCOME MEASURES: [HCO3(-)] and CO2 response. RESULTS: A total of 120 patients in the non-COPD group and 48 in the COPD group were studied. COPD patients had higher mean [HCO3(-)] than non-COPD patients (33.2 ± 5.4 vs. 25.7 ± 3.7 mmol/l, p<0.001). In both non-COPD and COPD patients we observed a significant inverse linear relationship between [HCO3(-)] and pH change per mmHg of PaCO2 (p<0.001), ΔVE/ΔPaCO2 (p<0.001) and ΔP0.1/ΔPaCO2 (p<0.001). CONCLUSIONS: There is an inverse linear relationship between [HCO3(-)] and the variation of pH for a given change in PaCO2 and the CO2 response.

Respiratory CO2 response in acute cervical spinal cord injury (CO2 response in spinal cord injury).

STUDY DESIGN: Retrospective study. OBJECTIVES: The objective of this study was to compare the CO2 response of acute tetraplegic cervical spinal cord injury (SCI) patients undergoing mechanical ventilation with a control group of critically ill patients ready for weaning of mechanical ventilation and successfully extubated. SETTING: This study was conducted at the intensive care unit of a University Hospital in Mallorca, Spain. METHODS: CO2 response was studied in 12 acute tetraplegic cervical SCI patients at the C4-C7 level and 22 control patients. The control group patients were consecutively selected from a database of patients with mechanical ventilation and who were successfully extubated after a CO2 response test. To increase the CO2 , we used the method of re-inhalation of expired air, and we evaluated the hypercapnic ventilatory response, the change in minute ventilation induced by the increase of partial pressure of arterial carbon dioxide (PaCO2 ), which measures the whole respiratory system (metabolic control, neuromuscular or ventilatory apparatus), and the hypercapnic drive response, the change in the airway occlusion pressure at 100 ms induced by the increase in PaCO2, which measures the chemosensitivity of the respiratory center. RESULTS: Cervical SCI patients were younger than the control group patients (26±7 and 62±12 years, respectively; P<0.001). Mean values of the hypercapnic ventilatory response in cervical SCI and control groups were 0.52±0.31 and 0.64±0.33 l min(-1) per mm Hg (P=0.40), respectively, and the hypercapnic drive response was 0.24±0.16 and 0.48±0.23 cm H2O per mm Hg (P=0.001), respectively. CONCLUSION: Acute tetraplegic cervical SCI patients had reduced hypercapnic drive response that may contribute to the difficult weaning, without reduction in hypercapnic ventilatory response.

Hypercapnia test and weaning outcome from mechanical ventilation in COPD patients.

We evaluated the hypercapnia response test as a weaning outcome predictor from mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD). We studied 44 COPD intubated patients considered ready for a weaning trial. The hypercapnia test was based on the modified method of re-inhalation of expired air Through the hypercapnic test we calculated the ratio of the change in minute volume (V(E)) to the change in PaCO2 (deltaV(E)/deltaPaCO2), the change in airway occlusion pressure at 0.1 second of inspiration (P0.1) to change in PaCO2 (deltaP0.1/deltaPACO2), the ratio of the change in P0.1 to baseline PaCO2 (deltaP0.1/PaCO2) and the ratio of the change in V(E) to baseline PaCO2 (deltaV(E)/PaCO2). Nineteen patients were successfully weaned and 25 patients failed. No differences in baseline clinical characteristics were found between the two groups. Weaning failure COPD patients had lower deltaP0.1/deltaPaCO2 (0.19 +/- 0.11 and 0.34 +/- 0.20 cm H2O/mmHg respectively, P = 0.006) and lower deltaV(E)/deltaPaCO2 (0.21 +/- 0.15 and 0.40 +/- 0.22 l/min/mmHg respectively, P = 0.002) than successfully weaned patients. The area under the receiver operating characteristic curve to discriminate weaning outcome was for the baseline PaCO2 0.81 (95% confidence interval: 0.66 to 0.91), hypercapnic PaCO2 0.76 (0.61 to 0.88), hypercapnic drive response 0.74 (0.59 to 0.86), hypercapnic ventilatory response 0.76 (0.60 to 0.87), deltaP0.1/PaCO2 0.76 (0.60 to 0.87) and for the deltaV(E)/PaCO2 0.81 (0.67 to 0.91). COPD patients with weaning failure have a significantly more blunted response to the hypercapnia response test than weaning success patients. This test could be useful to predict weaning failure patients if the combined values of the hypercapnic drive and hypercapnic ventilatory response were below the threshold values.

Use of liposomal amphotericin B in critically ill patients: a retrospective, multicenter, clinical study.

The clinical use of liposomal amphotericin B in 179 patients admitted to 30 medical-surgical intensive Care Units (ICUs) treated with this agent in 2006 was analyzed. Invasive fungal infections were proven, probable and possible in 44%, 16%, and 25% of cases, respectively. Fungi isolated were Candida albicans (38%), non-albicans Candida spp. (15%) and Aspergillus spp. (7%). The mean duration of treatment was 15 days (mean dose 3.7 mg/kg/day). The drug was used as rescue treatment after fluconazole or caspofungin in 47% of patients and as first line in 52% with a satisfactory clinical response in 54% of cases (72.6% with proven infection). Microbiological eradication was achieved in 68% of cases. Adverse events occurred in 51 patients but were severe in only 4. The use of liposomal amphotericin B both as first line and rescue treatment and mainly for proven invasive fungal infection was associated with a high rate of satisfactory clinical response.

Short-term effects of inhaled nitric oxide and prone position in pulmonary and extrapulmonary acute respiratory distress syndrome.

Inhaled nitric oxide (NO) and prone position (PP) are frequently used in the treatment of acute respiratory distress syndrome (ARDS). We compared the gas exchange and hemodynamic effects induced by the combination of NO inhalation and PP in patients with ARDS and analyzed whether or not pulmonary (Pu) and extrapulmonary (Epu) ARDS patients behave differently. Eight Pu and seven Epu ARDS patients were studied in four situations: supine position (SP); SP with NO inhalation at 5 ppm (SP + NO); PP; and PP with NO inhalation (PP + NO). In comparison with SP, NO inhalation and PP induced significant increases in Pa(O(2))/FI(O(2)) (from 106 +/- 58 in SP to 131 +/- 69 mm Hg in SP + NO, p = 0.01, and to 184 +/- 67 mm Hg in PP, p < 0.001). Pu and Epu ARDS showed a similar improvement in Pa(O(2))/FI(O2) with PP. Only Pu ARDS patients showed a significant increase (p < 0.001) in oxygenation induced by NO inhalation from 81 +/- 45 to 100 +/- 50 mm Hg in SP, and from 146 +/- 53 to 197 +/- 98 mm Hg in PP. In conclusion, PP is associated with a marked improvement in oxygenation, irrespective of the causes of ARDS, and additive effects of NO inhalation are mainly seen in patients with Pu ARDS.

A prospective study of unplanned endotracheal extubation in intensive care unit patients.

OBJECTIVE: To evaluate incidence, factors associated with unplanned endotracheal extubation (UEE), and prognostic factors for reintubation. DESIGN: A prospective study over a 32-mo period. SETTING: A 16-bed general intensive care unit of a tertiary university hospital. PATIENTS: Adult subjects undergoing endotracheal intubation for >48 hrs. INTERVENTIONS: Observation of patients who presented unplanned extubation. MEASUREMENTS AND MAIN RESULTS: Over the 32-mo period, there were 59 episodes of UEE in 55 patients (frequency 7.3%). Deliberate self-extubation occurred in 46 episodes (77.9%), while there were 13 episodes (22.1%) of accidental extubation. Twenty-seven (45.8%) episodes occurred in patients who were receiving full mechanical ventilatory support and 32 (54.2%) episodes occurred during the weaning period from mechanical ventilation. Reintubation was required in 27 (45.8%) episodes of UEE. The need for reintubation after UEE was 36.9% in deliberate self-extubation patients and 76.9% in accidental extubation patients (p = .01). Only 15.6% (5/32) of patients who presented UEE during weaning required reintubation, while reintubation was mandatory in 81.5% (22/27) of patients who presented UEE during full mechanical ventilatory support (p < .001). A multiple logistic regression analysis was performed to determine the variables independently associated with the need for reintubation: days of mechanical ventilation were significantly associated with the need for reintubation, and weaning was associated with no need for reintubation. The model correctly classified the need for reintubation in 84.7% (50/59) of cases. CONCLUSIONS: Reintubation in UEE patients strongly depends on the type of mechanical ventilatory support. The probability of requiring reintubation if UEE occurs during full ventilatory support is higher than if UEE occurs during weaning. These data suggest that some patients are under mechanical ventilation longer than necessary.

[Cranioencephalic trauma in adults: clinical and radiologic features]. / Traumatismo craneoencefálico del adulto: aspectos clínicos y radiológicos.

BACKGROUND: To analyse extracranial complications and basic variables in head-injury patients, such as Glasgow coma score (GCS), intracranial pressure (ICP) and cranial computerized tomography (CT), in relation to the outcome of these patients. PATIENTS AND METHODS: 64 consecutive patients (47 males and 17 females) with head injury, admitted from January 1992 to May 1994, were studied in this prospective study. Mean age was 37 +/- 18 years. Overall mortality was 23% (15/64). Student-t and Chi-square tests were used for statistical analysis, and p < 0.05 was considered statistical significant. RESULTS: Overall GCS was 7 +/- 3, survivors presenting GCS of 7.7 +/- 2.9 and non-survivors 4.7 +/- 1.5 (p = 0.04). CT were classified as follows: diffuse injury, 4 patients (7%); focal injury, 32 (53%), and mixed injury 24 (40%). Depending on the presence or absence of mesencephalic cisterns in the CT, GSC was 7.6 +/- 2.8 and 4.3 +/- 1.4, respectively (p = 0.04). Subarachnoid hemorrhage (SAH) was associated to a GCS of 6.3 +/- 2.5 and its absence to 8 +/- 3.3 (p = 0.03). The absence of mesencephalic cisterns and SAH were more frequent in the non-survivors, 72% and 32% (p = 0.01 and 0.04), respectively. ICP was recorded in 42 patients. Regarding to ICP, mortality was: 6.7% with ICP < or = 20 mmHg, 37% with ICP 21-30, 44% with ICP 31-40 and 67% with ICP > 50 mmHg (p = 0.03). Diabetes insipidus, cardiorespiratory arrest, shock, prolonged mechanical ventilation, SDRA and sepsis were the most frequent extracranial complications in non-survivors. CONCLUSIONS: There is an association between the outcome of head-injury patients with the GCS and ICP values. Absence of mesencephalic cisterns and SAH were radiologic signs of poor prognosis. Patients who died had more extracranial complications.

Prognostic indexes and mortality in critically ill patients with acute renal failure treated with different dialytic techniques.

The objective of this study was to compare the evolution of patients with acute renal failure (ARF) treated conservatively or with different dialytic techniques in an intensive care unit (ICU). From June 1992 to November 1994, 1087 consecutive patients were admitted in our ICU. Two hundred and twenty of these presented with ARF, and were divided into three groups; group I (control group): 156 patients with ARF who did not receive substitutive techniques; group II: 21 patients under intermittent hemodialysis (IHD) or peritoneal dialysis (PD); group III: 43 patients under continuous hemodiafiltration (CHDF). The studied variables were age, etiology of renal failure, requirement of dialysis, type of dialysis, length of ICU and hospital stay, and renal function outcome. APACHE II and SAPS scores were recorded on admission and analyzed for hospital mortality. Chi-square test and the analysis of variance were used for the statistical analysis. Results are presented as mean +/- SD. A p value below 0.05 was considered statistically significant. Although etiology of ARF was multifactorial, we found a high frequency of ARF due to sepsis (56.8%), hypoperfusion (58.7%), and acute tubular necrosis (62.5%). Sepsis and heart failure were clinical conditions associated to a greater mortality. We did not find any statistical difference between the two dialyzed groups for all the studied variables, nor between the three groups regarding APACHE II and hospital stay. Significant differences were found between dialyzed and non-dialyzed patients respect to age, group I: 64.1 +/- 13.6, group II: 56.4 +/- 19.7, and group III: 56.0 +/- 14.1 (p < 0.001), creatinine peak serum levels, group I: 260 +/- 130, group II: 494 +/- 209, and group III: 441 +/- 170 mumol/L (p < 0.0001), and mortality, group I: 46.9%, group II: 66.7%, and group III: 76.2% (p < 0.002). SAPS score showed differences between the control group and the CHDF group 13.9 +/- 4.8 and 16.4 +/- 5.4 (p < 0.007), respectively. The use of dialytic techniques in critically ill ARF patients is associated with greater mortality. Prognostic indexes on admission did not correctly classify our patients with ARF. Continuous hemodiafiltration does not involve greater mortality or length of stay as compared to conventional dialysis.