Patterns and Impact of Arterial CO2 Management in Patients With Acute Respiratory Distress Syndrome: Insights From the LUNG SAFE Study.

BACKGROUND: Considerable variability exists regarding CO2 management in early ARDS, with the impact of arterial CO2 tension on management and outcomes poorly understood. RESEARCH QUESTION: To determine the prevalence and impact of hypocapnia and hypercapnia on the management and outcomes of patients with early ARDS enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) study, an international multicenter observational study. STUDY DESIGN AND METHODS: Our primary objective was to examine the prevalence of day 1 and sustained (day 1 and 2) hypocapnia (Paco2 < 35 mm Hg), normocapnia (Paco2 35-45 mm Hg), and hypercapnia (Paco2 > 45 mm Hg) in patients with ARDS. Secondary objectives included elucidating the effect of CO2 tension on ventilatory management and examining the relationship with ARDS outcome. RESULTS: Of 2,813 patients analyzed, 551 (19.6%; 95%CI, 18.1-21.1) were hypocapnic, 1,018 (36.2%; 95% CI, 34.4-38.0) were normocapnic, and 1,214 (43.2%; 95% CI, 41.3-45.0) were hypercapnic, on day 1. Sustained hypocapnia was seen in 252 (9.3%; 95% CI, 8.2-10.4), sustained normocapnia in 544 (19.3%; 95% CI, 17.9-20.8), and sustained hypercapnia in 654 (24.1%; 95% CI, 22.5-25.7) patients. Hypocapnia was more frequent and severe in patients receiving noninvasive ventilation but also was observed in patients on controlled mechanical ventilation. Sustained hypocapnia was more frequent in middle-income countries, whereas sustained hypercapnia was more frequent in Europe. ARDS severity profile was highest in sustained hypercapnia, and these patients received more protective ventilation. No independent association was seen between arterial CO2 and outcome. In propensity-matched analyses, the hospital mortality rate was 36% in both sustained normocapnic and hypercapnic patients (P = 1.0). ICU mortality was higher in patients with mild to moderate ARDS receiving sustained hypocapnia (38.1%) compared with normocapnia (27.1%). INTERPRETATION: No evidence was found for benefit or harm with hypercapnia. Of concern, ICU mortality was higher with sustained hypocapnia in mild to moderate ARDS.

Hyperoxia and Hypocapnia During Pediatric Extracorporeal Membrane Oxygenation: Associations With Complications, Mortality, and Functional Status Among Survivors.

OBJECTIVES: To determine the frequency of hyperoxia and hypocapnia during pediatric extracorporeal membrane oxygenation and their relationships to complications, mortality, and functional status among survivors. DESIGN: Secondary analysis of data collected prospectively by the Collaborative Pediatric Critical Care Research Network. SETTING: Eight Collaborative Pediatric Critical Care Research Network-affiliated hospitals. PATIENTS: Age less than 19 years and treated with extracorporeal membrane oxygenation. INTERVENTIONS: Hyperoxia was defined as highest PaO2 greater than 200 Torr (27 kPa) and hypocapnia as lowest PaCO2 less than 30 Torr (3.9 kPa) during the first 48 hours of extracorporeal membrane oxygenation. Functional status at hospital discharge was evaluated among survivors using the Functional Status Scale. MEASUREMENTS AND MAIN RESULTS: Of 484 patients, 420 (86.7%) had venoarterial extracorporeal membrane oxygenation and 64 (13.2%) venovenous; 69 (14.2%) had extracorporeal membrane oxygenation initiated during cardiopulmonary resuscitation. Hyperoxia occurred in 331 (68.4%) and hypocapnia in 98 (20.2%). Hyperoxic patients had higher mortality than patients without hyperoxia (167 [50.5%] vs 48 [31.4%]; p < 0.001), but no difference in functional status among survivors. Hypocapnic patients were more likely to have a neurologic event (49 [50.0%] vs 143 (37.0%]; p = 0.021) or hepatic dysfunction (49 [50.0%] vs 121 [31.3%]; p < 0.001) than patients without hypocapnia, but no difference in mortality or functional status among survivors. On multivariable analysis, factors independently associated with increased mortality included highest PaO2 and highest blood lactate concentration in the first 48 hours of extracorporeal membrane oxygenation, congenital diaphragmatic hernia, and being a preterm neonate. Factors independently associated with lower mortality included meconium aspiration syndrome. CONCLUSIONS: Hyperoxia is common during pediatric extracorporeal membrane oxygenation and associated with mortality. Hypocapnia appears to occur less often and although associated with complications, an association with mortality was not observed.

Partial pressure of arterial carbon dioxide and survival to hospital discharge among patients requiring acute mechanical ventilation: A cohort study.

PURPOSE: To describe the prevalence of hypocapnia and hypercapnia during the earliest period of mechanical ventilation, and determine the association between PaCO2 and mortality. MATERIALS AND METHODS: A cohort study using an emergency department registry of mechanically ventilated patients. PaCO2 was categorized: hypocapnia (<35mmHg), normocapnia (35-45mmHg), and hypercapnia (>45mmHg). The primary outcome was survival to hospital discharge. RESULTS: A total of 1,491 patients were included. Hypocapnia occurred in 375 (25%) patients and hypercapnia in 569 (38%). Hypercapnia (85%) had higher survival rate compared to normocapnia (74%) and hypocapnia (66%), P<0.001. PaCO2 was an independent predictor of survival to hospital discharge [hypocapnia (aOR 0.65 (95% confidence interval [CI] 0.48-0.89), normocapnia (reference category), hypercapnia (aOR 1.83 (95% CI 1.32-2.54)]. Over ascending ranges of PaCO2, there was a linear trend of increasing survival up to a PaCO2 range of 66-75mmHg, which had the strongest survival association, aOR 3.18 (95% CI 1.35-7.50). CONCLUSIONS: Hypocapnia and hypercapnia occurred frequently after initiation of mechanical ventilation. Higher PaCO2 levels were associated with increased survival. These data provide rationale for a trial examining the optimal PaCO2 in the critically ill.

Hypocapnia measured by end-tidal carbon dioxide tension during anesthesia is associated with increased 30-day mortality rate.

STUDY OBJECTIVE: To evaluate the relationship between intraoperative end-tidal carbon dioxide (etco2) values and clinical outcomes with special attention on 30-day postoperative mortality and secondarily on hospital length of stay (LOS). DESIGN: Retrospective, observational study. SETTING: Surgical theaters of the University Hospital Center of Charleroi. PATIENTS: Five thousand three hundred seventeen patients ASA I-IV undergoing various surgical procedures (except pediatric and cardiac surgery) under general anesthesia. INTERVENTIONS: No intervention on the patients. MEASUREMENTS: The mean etco2 level measured during anesthesia was secondarily extracted from an electronic information management system. Patients were divided into 2 separate groups based on etco2 values less than or greater than or equal to 35 mm Hg. The primary end point was the in- and outhospital mortality in the 30-day period after surgery. The second was the LOS more than 6 days. MAIN RESULTS: Hypocapnia occurred in 66% of the patients. Mortality rate at 30-day was 84 of 3554 (2.4%) in the low etco2 group vs 15 of 1763 (0.9%) in the other (odds ratio, 2.99 [1.69-5.28]; P<.001). In multivariate analysis, age and ASA scores had significant independent associations with mortality rate. Adjusting for these factors had an effect on the relative odds ratio of etco2 on mortality of 1.99 ([1.11-3.56]; P<.001). Patients with low etco2 experienced higher LOS (14.1±9.4 vs 13.1±8.9 days; P<.001). Thirty five percent of the patients in the low etco2 group were still hospitalized more than 6 days compared with 30% in the other (P<.001). CONCLUSION: Low etco2 level during anesthesia is associated with an increase in postoperative mortality rate and LOS. These results emphasize the importance of preventing hypocapnia during anesthesia to improve surgical outcomes.

Association Between Arterial Carbon Dioxide Tension and Outcome in Patients Admitted to the Intensive Care Unit After Coronary Artery Bypass Surgery.

OBJECTIVES: The aim of this study was to determine the association between PaCO2 and patient outcome in patients admitted to the intensive care unit (ICU) after coronary artery bypass grafting (CABG). DESIGN: A retrospective cohort study. SETTING: Single-institutional, university hospital. PARTICIPANTS: All patients admitted to the ICU after CABG between January 2009 and December 2012. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Based on PaCO2 status during the first 24 hours after CABG, 1,011 patients were classified into 4 groups: normocapnia, hypocapnia, hypercapnia, and dual hyper/hypocapnia. The 30-day mortality rate was 0.7% (n = 4) for normocapnia, 1.5% (n = 4) for hypocapnia, 2.2% (n = 3) for hypercapnia, and 7.5% (n = 4) for the dual-exposure group. The extubation times were 13.3±21.7 hours, 15.8±21.37 hours, 21.79±39.70 hours, and 42.29±75.35 hours, respectively. After adjusting for confounding variables, the dual hypocapnia and hypercapnia exposure group was associated with increased 30-day mortality (odds ratio [OR] = 8.08; 95% confidence interval [CI], 1.82-35.86; p = 0.006) and delayed extubation (OR = 2.40; 95% CI, 1.24-4.64; p = 0.010). CONCLUSIONS: Exposure to both hypocapnia and hypercapnia within 24 hours after CABG was associated independently with increased risk of 30-day mortality and delayed extubation. Exposure to either hypocapnia or hypercapnia alone was not associated with patient outcome.

End-tidal CO2 on admission is associated with hemorrhagic shock and predicts the need for massive transfusion as defined by the critical administration threshold: A pilot study.

BACKGROUND: Critical administration threshold (≥3 units of packed red blood cells/h or CAT+) has been proposed as a new definition for massive transfusion (MT) that includes volume and rate of blood transfusion. CAT+ has been shown to eliminate survivor bias and be a better predictor of mortality than the traditional MT (>10 units/24h). End-tidal CO2 (ET CO2) negatively correlates with lactate and is an early predictor of shock in trauma patients. We conducted a pilot study to test the hypothesis that low ET CO2 on admission predicts CAT+. METHODS: ET CO2 via capnography and serum lactate were prospectively collected on admission for 131 patients requiring trauma team activation. Demographic data were obtained from patient charts. Excluded were patients with isolated head injuries, traumatic arrests, or pre-hospital intubations. CAT± status was determined for each hour up to 6h from admission as described; likewise, MT± status was determined up to 24h from admission. RESULTS: After exclusion criteria, 67 patients were analyzed. Mean age was 41.2 (SD 18.5). Thirty-three patients had a blunt mechanism of injury (49%), median ISS was 9 (interquartile range 4-19), and there were 6 deaths (9%). ET CO2 and lactate were negatively correlated by Spearman rank-based correlation (rho=-0.41, p=0.0006). Twenty-one (31%) and 8 (12%) patients were CAT+ and traditional MT+, respectively. There were a significantly greater proportion of patients with ISS>15, ET CO2 <35, or who died found to be CAT+. A binomial logistic regression model adjusting for age, SBP <90, HR, and ISS >15 revealed ET CO2 < 35 to be independently predictive of CAT+ (OR 9.24, 95% CI 1.51-56.57, p=0.016). CONCLUSIONS: This pilot study demonstrated that low ET CO2 had strong association with standard indicators for shock and was predictive of patients meeting CAT+ criteria in the first 6h after admission. Further study to verify these results and to elucidate CAT criteria's association with mortality will require a larger sample size.

Associations of arterial carbon dioxide and arterial oxygen concentrations with hospital mortality after resuscitation from cardiac arrest.

INTRODUCTION: Arterial concentrations of carbon dioxide (PaCO2) and oxygen (PaO2) during admission to the intensive care unit (ICU) may substantially affect organ perfusion and outcome after cardiac arrest. Our aim was to investigate the independent and synergistic effects of both parameters on hospital mortality. METHODS: This was a cohort study using data from mechanically ventilated cardiac arrest patients in the Dutch National Intensive Care Evaluation (NICE) registry between 2007 and 2012. PaCO2 and PaO2 levels from arterial blood gas analyses corresponding to the worst oxygenation in the first 24 h of ICU stay were retrieved for analyses. Logistic regression analyses were performed to assess the relationship between hospital mortality and both categorized groups and a spline-based transformation of the continuous values of PaCO2 and PaO2. RESULTS: In total, 5,258 cardiac arrest patients admitted to 82 ICUs in the Netherlands were included. In the first 24 h of ICU admission, hypocapnia was encountered in 22 %, and hypercapnia in 35 % of included cases. Hypoxia and hyperoxia were observed in 8 % and 3 % of the patients, respectively. Both PaCO2 and PaO2 had an independent U-shaped relationship with hospital mortality and after adjustment for confounders, hypocapnia and hypoxia were significant predictors of hospital mortality: OR 1.37 (95 % CI 1.17-1.61) and OR 1.34 (95 % CI 1.08-1.66). A synergistic effect of concurrent derangements of PaCO2 and PaO2 was not observed (P = 0.75). CONCLUSIONS: The effects of aberrant arterial carbon dioxide and arterial oxygen concentrations were independently but not synergistically associated with hospital mortality after cardiac arrest.

Hypo- and hypercapnia predict mortality in oxygen-dependent chronic obstructive pulmonary disease: a population-based prospective study.

BACKGROUND: The prognostic role of the arterial blood gas tension of carbon dioxide (PaCO2) in severe Chronic Obstructive Pulmonary Disease (COPD) remains unknown. The aim of this study was to estimate the association between PaCO2 and mortality in oxygen-dependent COPD. METHODS: National prospective study of patients starting long-term oxygen therapy (LTOT) for COPD in Sweden between October 1, 2005 and June 30, 2009, with all-cause mortality as endpoint. The association between PaCO2 while breathing air, PaCO2 (air), and mortality was estimated using Cox regression adjusted for age, sex, arterial blood gas tension of oxygen (PaO2), World Health Organization performance status, body mass index, comorbidity, and medications. RESULTS: Of 2,249 patients included, 1,129 (50%) died during a median 1.1 years (IQR 0.6-2.0 years) of observation. No patient was lost to follow-up. PaCO2 (air) independently predicted adjusted mortality (p < 0.001). The association with mortality was U-shaped, with the lowest mortality at approximately PaCO2 (air) 6.5 kPa and increased mortality at PaCO2 (air) below 5.0 kPa and above 7.0 kPa. CONCLUSION: In oxygen-dependent COPD, PaCO2 (air) is an independent prognostic factor with a U-shaped association with mortality.

Admission oxygenation and ventilation parameters associated with discharge survival in severe pediatric traumatic brain injury.

PURPOSE: Current Brain Trauma Foundation guidelines recommend avoiding hypoxemia after severe pediatric traumatic brain injury (TBI). Yet, recent studies on optimum admission oxygenation and ventilation parameters associated with discharge survival in pediatric TBI are lacking. MATERIALS AND METHODS: After IRB approval, a retrospective study involving pediatric patients ages ≤14 years with severe TBI (head Abbreviated Injury Scale (AIS) score of ≥3, Glasgow Coma Scale score of ≤8 on admission) admitted to Harborview Medical Center (level 1 pediatric trauma center), Seattle, WA, during 2003 to 2007 was performed. Admission demographics, clinical data, and laboratory characteristics were abstracted. Hypoxemia was defined as PaO2 < 60 mmHg, hypocarbia was defined as PaCO2 ≤ 35 mmHg, and hypercarbia was defined as PaCO2 ≥ 46 mmHg. RESULTS: One hundred ninety-four patients met inclusion criteria of which 162 (83.5 %) patients survived. Admission hypoxemia occurred in nine (5.6 %) patients who survived and eight (25 %) patients who died (p < 0.001). Children with admission PaCO2 between 36 and 45 mmHg had greater discharge survival compared with those with both admission hypocarbia (PaCO2 ≤ 35 mmHg) and hypercarbia (PaCO2 ≥ 46 mmHg). Admission PaO2 301-500 mmHg (adjusted odds ratio (AOR), 8.02 (95 % confidence interval (CI), 1.73-37.10); p = 0.008) and admission PaCO2 = 36-45 mmHg (AOR, 5.47 (95 % CI, 1.30-23.07); p = 0.02) were independently associated with discharge survival. CONCLUSIONS: Discharge survival after severe pediatric TBI was associated with admission PaO2 301-500 mmHg and PaCO2 = 36-45 mmHg. Admission hypocarbia and hypercarbia were each associated with increased discharge mortality.

Alteraciones electrocardiográficas en personas sanas con Síndrome de Apnea Hipopnea del Sueño inducido, predictoras de arritmias ventriculares y muerte súbita / Electrocardiographic alterations in healthy people with hypopnea Apnea syndrome of induced sleep, predictors of ventricular arrhythmias and sudden death

Antecedentes: El Síndrome de Apnea Hipopnea durante el sueño puede producir trastornos de la conducción cardiaca que pueden conducir a la muerte súbita. Objetivo: Determinar las alteraciones electrocardiográficas y del ritmo cardíaco en sujetos con Síndrome de Apnea-Hipopnea del Sueño (SAHS) y apnea central inducida. Métodos: Evaluación clínica y electrocardiográfica de 50 sujetos aparentemente sanos con SAHS, mediante maniobra de Mueller y con apnea central postespiratoria. Se comparan resultados basales, durante y después de la maniobra mediante análisis de varianza para mediciones repetidas. Resultados: El 60 por ciento de casos fueron varones y 40 por ciento mujeres, con edades promedio de 36 años para varones y de 35,55 años para mujeres (p>0,05). Con la maniobra de Mueller no hubo efecto sobre la duración de la onda P (101,5 ms antes y durante la maniobra, 101,6 ms luego; p>0,05). El complejo QRS tampoco se afectó de manera significativa (90,7 ms antes, 90,9 ms durante y 90,6 ms después; p>0,05). El intervalo QTc aumentó de 413,3 ms antes, a 423,3 ms durante y 423,1 ms después de la maniobra (p0,05), pero la PAM descendió de 89,7 mmHg en el basal a 88,2 mmHg durante el procedimiento y ascendió a 93,6 mmHg después de la misma (p<0,05); no hubo efecto sobre la frecuencia cardiaca y no hubo contracciones supraventriculares...

Background: Obstructive Sleep Apnea can cause cardiac conduction disorders that can lead to sudden death. Objective: To determine the electrocardiographic changes and heart rate in subjects with Obstructive Sleep Apnea and central apnea induced. Methods: Clinical and electrocardiographic evaluation of 50 apparent1y healthy subjects with OSA, using Mueller maneuver and central apnea post-expiratory. Baseline values are compared, during and after the maneuver by analysis of variance for repeated measurements. Results: 60 per cent of cases were male and 40 per cent female mean age of 36 years for males and 35.55 years for females (p>0.05). With Mueller maneuver had no effect on P-wave duration (101.5 msec before and during the maneuver, 101.6 msec following, P>0.05). The QRS wave is not significantly affected (90.7 msec before and 90.6 msec, 90.9 msec after, P>0.05). The QTc raised from 413.3 to 423.3 msec before and 423.1 msec after the maneuver msec (p0.05), but MAP decreased from 89.7 mmHg at baseline to 88.2 mmHg during the procedure and amounted to 93.6 mmHg (p<0.05), there was no effect on heart rate and no supraventricular or ventricular premature contractions with the maneuver. Conclusions: Patients with SAHS QT prolongation and Tp-Tec, and increase in MAP with Mueller maneuver, and only affected the PAM with central apnea postespiratory.

Hypocapnia and hypercapnia are predictors for ICU admission and mortality in hospitalized patients with community-acquired pneumonia.

OBJECTIVE: The purpose of our study was to examine in patients hospitalized with community acquired pneumonia (CAP) the association between abnormal Pa CO 2 and ICU admission and 30-day mortality. METHODS: A retrospective cohort study was conducted at two tertiary teaching hospitals. Eligible subjects were admitted with a diagnosis of CAP. Arterial blood gas analyses were obtained with measurement of PaCO2 on admission. Multivariate analyses were performed using 30-day mortality and ICU admission as the dependent measures. RESULTS: Data were abstracted on 453 subjects with a documented arterial blood gas analysis. One hundred eighty-nine patients (41%) had normal PaCO2 (35-45 mm Hg), 194 patients (42%) had aPa CO 2 , 35 mm Hg (hypocapnic), and 70 patients (15%) had a Pa CO 2 . 45 mm Hg (hypercapnic).In the multivariate analysis, after adjusting for severity of illness, hypocapnic patients had greater 30-day mortality (OR= 2.84; 95% CI, 1.28-6.30) and a higher need for ICU admission (OR= 2.88;95% CI, 1.68-4.95) compared with patients with normal PaCO2. In addition, hypercapnic patients had a greater 30-day mortality (OR= 3.38; 95% CI, 1.38-8.30) and a higher need for ICU admission(OR =5.35; 95% CI, 2.80-10.23). When patients with COPD were excluded from the analysis,the differences persisted between groups. CONCLUSION: In hospitalized patients with CAP, both hypocapnia and hypercapnia were associated with an increased need for ICU admission and higher 30-day mortality. These findings persisted after excluding patients with CAP and with COPD. Therefore, PaCO2 should be considered for inclusion in future severity stratification criteria to appropriate identified patients who will require a higher level of care and are at risk for increased mortality.

Hypocarbia and adverse outcome in neonatal hypoxic-ischemic encephalopathy.

OBJECTIVE: To evaluate the association between early hypocarbia and 18- to 22-month outcome among neonates with hypoxic-ischemic encephalopathy. STUDY DESIGN: Data from the National Institute of Child Health and Human Development Neonatal Research Network randomized, controlled trial of whole-body hypothermia for neonatal hypoxic-ischemic encephalopathy were used for this secondary observational study. Infants (n = 204) had multiple blood gases recorded from birth to 12 hours of study intervention (hypothermia versus intensive care alone). The relationship between hypocarbia and outcome (death/disability at 18 to 22 months) was evaluated by unadjusted and adjusted analyses examining minimum PCO(2) and cumulative exposure to PCO(2) <35 mm Hg. The relationship between cumulative PCO(2) <35 mm Hg (calculated as the difference between 35 mm Hg and the sampled PCO(2) multiplied by the duration of time spent <35 mm Hg) and outcome was evaluated by level of exposure (none-high) using a multiple logistic regression analysis with adjustments for pH, level of encephalopathy, treatment group (± hypothermia), and time to spontaneous respiration and ventilator days; results were expressed as odds ratios and 95% confidence intervals. Alternative models of CO(2) concentration were explored to account for fluctuations in CO(2). RESULTS: Both minimum PCO(2) and cumulative PCO(2) <35 mm Hg were associated with poor outcome (P < .05). Moreover, death/disability increased with greater cumulative exposure to PCO(2) <35 mm Hg. CONCLUSIONS: Hypocarbia is associated with poor outcome after hypoxic-ischemic encephalopathy.

Aminophylline therapy during endotoxemia in anesthetized spontaneously breathing rats.

Phosphodiesterase inhibitors, such as pentoxifylline and aminophylline, may reduce inflammatory cytokine-induced endothelial permeability. We tested the hypothesis that aminophylline treatment may ameliorate the pulmonary and extrapulmonary effects of endotoxemia in a rat model. In anesthetized rats, a tracheotomy was performed along with catheterization of a femoral vein and artery. Anesthesia, fluid balance, and normothermia were maintained throughout the 6-h experiment. A stable hemodynamic and gas-exchange baseline was established at which time the rats were randomly divided into three groups. Group I received aminophylline (1mg/kg) over 30 min followed by 0.5mg/kg/h. Group II received a single dose of endotoxin (4 mg/kg) while Group III received both aminophylline and endotoxin as described for Groups I and II, respectively. Gas-exchange profiles, mean arterial blood pressure, and heart rate were determined every 2h. At hour 6, the rats were euthanized and lung, kidney, and heart tissue were removed for determination of water content. As our control group, we utilized data from our previously published study involving an identical surgical procedure with normal saline. Endotoxemia produced characteristic respiratory and hemodynamic signs of sepsis including hypotension, hyperventilation, tachycardia, and renal and pulmonary edema. Aminophylline treatment failed to prevent these endotoxemia-induced respiratory and hemodynamic manifestations of sepsis, but significantly improved the acid-base imbalance that developed during surgical procedures in saline-treated control rats. Further studies are warranted to determine potentially beneficial doses of aminophylline and resulting theophylline serum concentrations under such septic conditions.

Inestabilidad ventilatoria en infecciones agudas del sistema nervioso central / Ventilatory inestability in acute infections of the central nervous system

Se evaluaron en forma retrospectiva 114 pacientes egresados del Hospital "Dr. F.J. Muñiz" con diagnóstico de infecciones agudas del sistema nervioso central. Se utilizó como criterio de inclusión, ausencia de patología pleuropulmonar concomitante, que se interpreta como posible factor desencadenante de un cuadro de insuficiencia respiratoria. Todos los pacientes fueron sometidos a asistencia respiratoria mecánica, por distintos criterios y con diferentes parámetros gasométricos previos. La tasa de letalidad global fue del 44,75 por ciento, hallándose en los pacientes ventilados, gasométricamente normales, previa asistencia respiratoria, el menor índice de letalidad, 13,63 por ciento en contraste con aquellos que fueron sometidos a ventilación mecánica con criterios de insuficiencia respiratoria, cuya mortalidad alcanzó el 61,76 por ciento. A pesar de tratarse de un estudio retrospectivo, se desea hacer hincapié en la necesidad de considerar los mecanismos compensatorios ante la hipertensión endocraneana, la hiperventilación, como una inestabilidad ventilatoria en sí, extremando las precauciones para indicar una asistencia ventilatoria precoz, para asegurar una ventilación alveolar efectiva (AU)