The stability of blood gases and CO-oximetry under slushed ice and room temperature conditions.

OBJECTIVES: Human blood gas stability data is limited to small sample sizes and questionable statistical techniques. We sought to determine the stability of blood gases under room temperature and slushed iced conditions in patients using survival analyses. METHODS: Whole blood samples from ∼200 patients were stored in plastic syringes and kept at room temperature (22-24 °C) or in slushed ice (0.1-0.2 °C) before analysis. Arterial and venous pO2 (15-150 mmHg), pCO2 (16-72 mmHg), pH (6.73-7.52), and the CO-oximetry panel [total hemoglobin (5.4-19.3 g/dL), percentages of oxyhemoglobin (O2Hb%, 20-99%), carboxyhemoglobin (COHb, 0.1-5.4%) and methemoglobin (MetHb, 0.2-4.6%)], were measured over 5-time points. The Royal College of Pathologists of Australasia's (RCPA's) criteria determined analyte instability. Survival analyses identified storage times at which 5% of the samples for various analytes became unstable. RESULTS: COHb and MetHb were stable up to 3 h in slushed ice and at room temperature; pCO2, pH was stable at room temperature for about 60 min and 3 h in slushed ice. Slushed ice shortened the storage time before pO2 became unstable (from 40 to 20 min), and the instability increased when baseline pO2 was ≥60 mmHg. The storage time for pO2, pCO2, pH, and CO-oximetry, when measured together, were limited by the pO2. CONCLUSIONS: When assessing pO2 in plastic syringes, samples kept in slushed ice harm their stability. For simplicity's sake, the data support storage times for blood gas and CO-oximetry panels of up to 40 min at room temperature if following RCPA guidelines.

Association between the time-varying arterial carbon dioxide pressure and 28-day mortality in mechanically ventilated patients with acute respiratory distress syndrome.

BACKGROUND: Recent studies have shown an association between baseline arterial carbon dioxide pressure (PaCO2) and outcomes in patients with acute respiratory distress syndrome (ARDS). However, PaCO2 probably varies throughout the disease, and few studies have assessed the effect of longitudinal PaCO2 on prognosis. We thus aimed to investigate the association between time-varying PaCO2 and 28-day mortality in mechanically ventilated ARDS patients. METHODS: In this retrospective study, we included all adult (≥ 18 years) patients diagnosed with ARDS who received mechanical ventilation for at least 24 h at a tertiary teaching hospital between January 2014 and March 2021. Patients were excluded if they received extracorporeal membrane oxygenation (ECMO). Demographic data, respiratory variables, and daily PaCO2 were extracted. The primary outcome was 28-day mortality. Time-varying Cox models were used to estimate the association between longitudinal PaCO2 measurements and 28-day mortality. RESULTS: A total of 709 patients were eligible for inclusion in the final cohort, with an average age of 65 years, of whom 70.7% were male, and the overall 28-day mortality was 35.5%. After adjustment for baseline confounders, including age and severity of disease, a significant increase in the hazard of death was found to be associated with both time-varying PaCO2 (HR 1.07, 95% CI 1.03-1.11, p<0.001) and the time-varying coefficient of variation for PaCO2 (HR 1.24 per 10% increase, 95% CI 1.10-1.40, p<0.001) during the first five days of invasive mechanical ventilation. The cumulative proportion of exposure to normal PaCO2 (HR 0.72 per 10% increase, 95% CI 0.58-0.89, p = 0.002) was associated with 28-day mortality. CONCLUSION: PaCO2 should be closely monitored in mechanically ventilated ARDS patients. The association between PaCO2 and 28-day mortality persisted over time. Increased cumulative exposure to normal PaCO2 was associated with a decreased risk of death.

Assessing key clinical parameters before and after intraventricular hemorrhage in very preterm infants.

Intraventricular cerebral hemorrhage (IVH) is one of the most severe complications of premature birth, potentially leading to lifelong disability. The purpose of this paper is the assessment of the evolution of three of the most relevant parameters, before and after IVH: mean arterial pressure (MAP), arterial carbon dioxide pressure (pCO2), and cerebral blood flow (CBF). Clinical records of 254 preterm infants with a gestational age of 23-30 weeks, with and without a diagnosis of IVH, were reviewed for MAP and arterial pCO2 in the period up to 7 days before and 3 days after IVH or during the first 10 days of life in cases without IVH.Conclusion: A statistically significant increase in pCO2 and decrease in MAP in patients with IVH compared with those without were detected. Both the mean values and the mean absolute deviations of CBF were computed in this study, and the latter was significantly higher than in control group. High deviations of CBF, as well as hypercapnia and hypotension, are likely to contribute to the rupture of cerebral blood vessels in preterm infants, and consequently, to the development of IVH.What is Known:• The origin of IVH is multifactorial, but mean arterial pressure, carbon dioxide partial pressure, and cerebral blood flow are recognized as the most important parameters.• In premature infants, the autoregulation mechanisms are still underdeveloped and cannot compensate for cerebral blood flow fluctuations.What is New:• The numerical simulation of CBF is shown to be a promising approach that may be useful in the care of preterm infants.• The mean values of CBF before and after IVH in the affected group were similar to those in the control group, but the mean absolute deviations of CBF in the affected group before and after IVH were significantly higher than that in the control group.

Predictive factors for prognosis following unsedated percutaneous endoscopic gastrostomy in ALS patients.

INTRODUCTION: This study aimed to determine the prognostic factors and the values that predict survival after percutaneous endoscopic gastrostomy (PEG) tube placement in patients with amyotrophic lateral sclerosis (ALS). METHODS: We retrospectively analyzed the correlations for 97 consecutive patients with ALS between clinical parameters and survival following PEG tube placement using the log-rank test and Cox proportional-hazards models. RESULTS: The log-rank test showed that an arterial carbon dioxide pressure (PaCO2 ) of ≤ 40 mmHg (P = 0.0054), a forced vital capacity (FVC) of ≥ 38% of predicted (P = 0.0003), and bulbar-onset (P = 0.0121) were significantly associated with better post-PEG survival. Multivariate analysis showed that the FVC and PaCO2 were associated with better post-PEG survival (P = 0.0081 and P = 0.0265, respectively). CONCLUSIONS: PEG tube placement in ALS is recommended when FVC is ≥ 38% of predicted and when PaCO2 is normal. Muscle Nerve 54: 277-283, 2016.

Relationship Between Episodic Nocturnal Hypercapnia and History of Exacerbations in Patients with Advanced Chronic Obstructive Pulmonary Disease.

Purpose: An episodic increase in transcutaneous carbon dioxide pressure (PtcCO2) is often recognized in patients with advanced chronic obstructive pulmonary disease (COPD) by overnight PtcCO2 monitoring. This phenomenon, called episodic nocturnal hypercapnia (eNH), mainly corresponds to rapid eye movement (REM) sleep-related hypoventilation. However, it is unclear whether eNH is associated with the frequency of COPD exacerbation. We aimed to investigate whether a relationship exists between COPD exacerbation and eNH. Patients and Methods: We enrolled consecutive patients with stable, severe, or very severe COPD with a daytime arterial carbon dioxide pressure (PaCO2) <55.0 mmHg who underwent overnight PtcCO2 monitoring from April 2013 to January 2017. We retrospectively analyzed the prevalence of eNH and sleep-associated hypoventilation (SH) as defined by the American Academy of Sleep Medicine. Moreover, we compared the relationship between the frequency of COPD exacerbations in the previous year and eNH or SH. Results: Twenty-four patients were included in this study. The study patients had a mean daytime PaCO2 and nocturnal PtcCO2 of 43.3 ± 6.8 mmHg and 42.9 ± 9.6 mmHg, respectively. Six (25.0%) and 11 (45.9%) of the 24 patients met the SH and eNH criteria, respectively. The odds ratios of SH and eNH for at least one annual exacerbation were 1.0 [95% confidence interval (CI): 0.16-6.00] and 11.1 [95% CI: 1.39-87.7], respectively. The odds ratios of SH and eNH for at least two annual exacerbations were 0.3 [95% CI: 0.04-2.64] and 6.6 [95% CI: 1.06-39.4], respectively. Conclusion: In patients with advanced COPD and a daytime PaCO2 <55.0 mmHg, eNH may be associated with a history of more frequent exacerbations than SH. Further studies are required to validate these findings.

Assessment of Nocturnal Hypoventilation by Different Methods and Definitions in Children with Neuromuscular Disease: Oxycapnography and Blood Gas Analysis.

OBJECTIVE: To investigate whether partial arterial carbon dioxide pressure (PaCO 2 ) level in arterial blood gas analysis that was used to predict nocturnal hypoventilation (NH) is concordant with nocturnal end-tidal CO 2 (PetCO 2 ) measurement obtained by a noninvasive method of oxycapnography in children with neuromuscular disease (NMD). METHODS: Twenty-one patients aged 6-18 years with a confirmed diagnosis of NMD were enrolled. Each patient underwent a nocturnal oxycapnography study using an orinasal probe and a pulse oximetry finger probe to record PetCO 2 , oxygen saturation (SpO 2 ), pulse rate, and respiratory rate. Arterial blood gas analysis was performed to record PaCO 2 levels on three occasions at night (23:00 pm, 03:00 am, 07:00 am). RESULTS: The mean overnight PaCO 2 level of the three blood gas analyses (mean PaCO 2 noct) was 41.78±4.69 mmHg. A significant change was observed between mean PaCO 2 23:00 and PaCO 2 07:00 levels (p=0.032). There was no significant difference between PaCO 2 , PetCO 2 , and SpO 2 levels in the NMD group. The interclass correlation coefficient between PaCO 2 07:00 and PetCO 2 levels was 0.791 (95% CI: 0.533-0.923); the interclass correlation coefficient between overnight mean PaCO 2 and PetCO 2 levels was 0.811 (95% CI:0.533-0.923). CONCLUSION: Our study indicates that nocturnal PetCO 2 and PaCO 2 levels were statistically comparable but the use of PaCO 2 alone is not adequate to make an early diagnosis of NH in NMD. There is a need for making more restrictive definitions for NH, and conducting studies with larger study populations to reach an agreement on the best definition of hypoventilation, and updating consensus guidelines.

A case of severe acute exacerbation of Yokkaichi asthma treated with a vibrating mesh nebulizer.

Yokkaichi asthma was one of the most common environmental pollution diseases in Japan in the 1960s and 1970s. The problem of air pollution in Yokkaichi was solved in the 1970s. However, mortality and life expectancy were still affected by the late effects of air pollution in patients with Yokkaichi asthma even in the 2000s. In this case report, we described the experience of successful treatment of a patient with severe asthmatic status due to Yokkaichi asthma. A 40s-year-old man, who was officially certified as a patient with Yokkaichi asthma from his infancy, was admitted to hospital due to acute exacerbation of asthma. Mechanical ventilation, intravenous administration of aminophylline and dexamethasone, enteral administration of montelukast, and a transdermal patch of tulobuterol were started. However, because of the lack of improvement in clinical status, inhalation of procaterol using vibrating mesh nebulizer systems was started. Inhalation of procaterol was used three times a day. After using the vibrating mesh nebulizer, respiratory system compliance and hypercapnia rapidly improved. Bilateral expiratory wheezing was diminished. Weaning from mechanical ventilation was initiated, and on the eighth day of mechanical ventilation, the patient was extubated. Although intractable respiratory failure with decreased respiratory system compliance resulting from the late effects of air pollution and a long-time asthmatic inflammatory condition was observed, the use of a vibrating mesh nebulizer for the inhaled administration of procaterol was useful to relieve severe bronchospasm due to Yokkaichi asthma.

Metodología físico-matemática de evaluación del pH y la presión de dióxido de carbono arteriales y venosos en la unidad de cuidados intensivos / Physical-mathematical assessment methodology ph dioxide pressure and arterial and venous carbon in the intensive care unit

ResumenIntroducción:La dinámica cardíaca ha sido caracterizada a partir de la teoría de los sistemas dinámicos y la geometría fractal, permitiendo generar metodologías de aplicación clínica.Objetivo:desde los sistemas dinámicos, se desarrollará una metodología de evaluación de los pH y presiones de dióxido de carbono arteriales y venosos para pacientes de la Unidad de Cuidados Intensivos.Materiales y Métodos:se escogieron 10 pacientes con diversas patologías de la Unidad de Cuidados Intensivos Postqui rúrgicos del Hospital Militar Central, registrando pH y presiones de dióxido de carbono arteriales y venosas durante su tiempo de estancia; posteriormente se construyeron atractores, determinando su tipo de trayectoria y estableciendo los valores máximos y mínimos de estas variables en el mapa de retardo.Resultados:se encontró un comportamiento caótico de las variables evaluadas, hallando valores mínimos y máximos de 7,01 y 7,59 para pH arterial, 6,97 y 7,53 para pH venoso, 14,40 y 73,70 para presión arterial de dióxido de carbono, y 19,20 y 97,90 para presión venosa de dióxido de carbono.Conclusiones:La evaluación de los valores máximos y mínimos del atractor en el mapa de retardo constituye un nuevo método, objetivo y reproducible, para la evaluación matemática de cada una de las variables estudiadas, de utilidad para el seguimiento de pacientes en UCI.

SummaryIntroduction:Cardiac dynamics has been characterized from the theory of dynamical systems and fractal geometry, allowing to generate methodologies with clinical application. Objective: from dynamic systems, a methodology for evaluating the arterial and venous pH and dioxide of carbon pressures for patient in Intensive Care Unit will be developed.Materials and Methods:10 patients with various pathologies were selected from Post-surgical Intensive Care Unit of the Central Military Hospital, recording arterial and venous pH and dioxide of carbon pressures of during its stay; attractors were built subsequently, determining the type of path and setting the maximum and minimum values of these variables on the delay map.Results:chaotic behavior of the variables evaluated was found, finding maximum and minimum values of 7,01 and 7,59 for arterial pH values, 6,97 and 7,53 for venous pH, 14,40 and 73,70 for arterial dioxide of carbon pressure, and 19,20 and 97,90 for venous dioxide of carbon pressure.Conclusions:The evaluation of the maximum and minimum values of the attractor on the delay map is a new method, objective and reproducible for the mathematical evaluation of each of the variables studied, useful for monitoring patients in Intensive Care Unit.