Changes In PaCO2 Research Articles

Hypercapnia during transcatheter aortic valve replacement under monitored anaesthesia care: a retrospective cohort study

BackgroundAcute intraoperative hypercapnia and respiratory acidosis, which can occur during monitored anaesthesia care (MAC), pose significant cardiopulmonary risks for patients with aortic stenosis undergoing transcatheter aortic valve replacement (TAVR). The...

Evidence for direct CO2 -mediated alterations in cerebral oxidative metabolism in humans.

How the cerebral metabolic rates of oxygen and glucose utilization (CMRO2 and CMRGlc, respectively) are affected by alterations in arterial PCO2 (PaCO2) is equivocal and therefore was the primary question of this study. This retrospective analysis involved pooled data from four separate studies, involving 41 healthy adults (35 males/6 females). Participants completed stepwise steady-state alterations in PaCO2 ranging between 30 and 60 mmHg. The CMRO2 and CMRGlc were assessed via the Fick approach (CBF × arterial-internal jugular venous difference of oxygen or glucose content, respectively) utilizing duplex ultrasound of the internal carotid artery and vertebral artery to calculate cerebral blood flow (CBF). The CMRO2 was altered by 0.5 mL × min-1 (95% CI: -0.6 to -0.3) per mmHg change in PaCO2 (p < 0.001) which corresponded to a 9.8% (95% CI: -13.2 to -6.5) change in CMRO2 with a 9 mmHg change in PaCO2 (inclusive of hypo- and hypercapnia). The CMRGlc was reduced by 7.7% (95% CI: -15.4 to -0.08, p = 0.045; i.e., reduction in net glucose uptake) and the oxidative glucose index (ratio of oxygen to glucose uptake) was reduced by 5.6% (95% CI: -11.2 to 0.06, p = 0.049) with a + 9 mmHg increase in PaCO2. Collectively, the CMRO2 is altered by approximately 1% per mmHg change in PaCO2. Further, glucose is incompletely oxidized during hypercapnia, indicating reductions in CMRO2 are either met by compensatory increases in nonoxidative glucose metabolism or explained by a reduction in total energy production.

A proof-of-concept study: advantages of the subxiphoid over the lateral intercostal approach.

The study was designed to evaluate the superiority of the subxiphoid approach compared with the lateral intercostal approach during the operation and other perioperative indices. Patients diagnosed with anterior mediastinal disease in our hospital between January 2018 and October 2019 were prospectively assigned to 2 groups; 1 group underwent the lateral intercostal approach and 1 group underwent the subxiphoid approach of video-assisted thoracoscopic surgery to resect the diseased tissue. The PaCO2, SaO2, PaO2 and circulation changes were recorded during the operation; the neutrophil-to-lymphocyte ratio and other perioperative outcomes, including clinical and surgical results, operating time, blood loss, postoperative complication and postoperative pain score were compared. A total of 59 patients diagnosed with an anterior mediastinal tumour or myasthenia gravis underwent a video-assisted thoracoscopic resection. Thirty-one patients were treated via the subxiphoid approach, and 28 patients were treated via the lateral intercostal approach. The PaCO2 increased significantly and the SaO2 remained stable in the subxiphoid group during the operation, whereas PaCO2 increased significantly and SaO2 decreased at the same time in the lateral intercostal group. Operations were more frequently interrupted for the hypoxia or circulation disturbance during the process of dissecting the thymus in the lateral intercostal approach. Compared with the lateral intercostal approach, patients treated via the subxiphoid approach experienced less inflammation and exhibited lower pain scores and shorter postoperative hospital stays. There were no significant differences in postoperative complications between the 2 groups. All of the patients recovered well when discharged. Our study results suggested that the subxiphoid approach has less of an influence on the pulmonary circulation than the lateral intercostal approach, that the whole procedure is safer and easier and that the subxiphoid approach may be the ideal choice for patients with anterior mediastinal disease.

Acute sodium bicarbonate administration improves ventilatory efficiency in experimental respiratory acidosis: clinical implications.

Administering sodium bicarbonate (NaHCO3) to patients with respiratory acidosis breathing spontaneously is contraindicated because it increases carbon dioxide load and depresses pulmonary ventilation. Nonetheless, several studies have reported salutary effects of NaHCO3 in patients with respiratory acidosis but the underlying mechanism remains uncertain. Considering that such reports have been ignored, we examined the ventilatory response of unanesthetized dogs with respiratory acidosis to hypertonic NaHCO3 infusion (1 N, 5 mmol/kg) and compared it with that of animals with normal acid-base status or one of the remaining acid-base disorders. Ventilatory response to NaHCO3 infusion was evaluated by examining the ensuing change in PaCO2 and the linear regression of the PaCO2 vs. pH relationship. Strikingly, PaCO2 failed to increase and the ΔPaCO2 vs. ΔpH slope was negative in respiratory acidosis, whereas PaCO2 increased consistently and the ΔPaCO2 vs. ΔpH slope was positive in the remaining study groups. These results cannot be explained by differences in buffering-induced decomposition of infused bicarbonate or baseline levels of blood pH, PaCO2, and pulmonary ventilation. We propose that NaHCO3 infusion improved the ventilatory efficiency of animals with respiratory acidosis, i.e., it decreased their ratio of total pulmonary ventilation to carbon dioxide excretion (VE/VCO2). Such exclusive effect of NaHCO3 infusion in animals with respiratory acidosis might emanate from baseline increased VD/VT (dead space/tidal volume) caused by bronchoconstriction and likely reduced pulmonary blood flow, defects that are reversed by alkali infusion. Our observations might explain the beneficial effects of NaHCO3 reported in patients with acute respiratory acidosis.

Characterizing the Relationship Between Arterial Carbon Dioxide Trajectory and Serial Brain Biomarkers with Central Nervous System Injury During Veno-Venous Extracorporeal Membrane Oxygenation: A Prospective Cohort Study

BackgroundCentral nervous system (CNS) injury following initiation of veno-venous extracorporeal membrane oxygenation (VV-ECMO) is common. An acute decrease in partial pressure of arterial carbon dioxide (PaCO2) following VV-ECMO initiation has been suggested as an etiological factor, but the challenges of diagnosing CNS injuries has made discerning a relationship between PaCO2 and CNS injury difficult.MethodsWe conducted a prospective cohort study of adult patients undergoing VV-ECMO for acute respiratory failure. Arterial blood gas measurements were obtained prior to initiation of VV-ECMO, and at every 2–4 h for the first 24 h. Neuroimaging was conducted within the first 7–14 days in patients who were suspected of having neurological injury or unable to be examined because of sedation. We collected blood biospecimens to measure brain biomarkers [neurofilament light (NF-L); glial fibrillary acidic protein (GFAP); and phosphorylated-tau 181] in the first 7 days following initiation of VV-ECMO. We assessed the relationship between both PaCO2 over the first 24 h and brain biomarkers with CNS injury using mixed methods linear regression. Finally, we explored the effects of absolute change of PaCO2 on serum levels of neurological biomarkers by separate mixed methods linear regression for each biomarker using three PaCO2 exposures hypothesized to result in CNS injury.ResultsIn our cohort, 12 of 59 (20%) patients had overt CNS injury identified on head computed tomography. The PaCO2 decrease with VV-ECMO initiation was steeper in patients who developed a CNS injury (− 0.32%, 95% confidence interval − 0.25 to − 0.39) compared with those without (− 0.18%, 95% confidence interval − 0.14 to − 0.21, P interaction < 0.001). The mean concentration of NF-L increased over time and was higher in those with a CNS injury (464 [739]) compared with those without (127 [257]; P = 0.001). GFAP was higher in those with a CNS injury (4278 [11,653] pg/ml) compared with those without (116 [108] pg/ml; P < 0.001). The mean NF-L, GFAP, and tau over time in patients stratified by the three thresholds of absolute change of PaCO2 showed no differences and had no significant interaction for time.ConclusionsAlthough rapid decreases in PaCO2 following initiation of VV-ECMO were slightly greater in patients who had CNS injuries versus those without, data overlap and absence of relationships between PaCO2 and brain biomarkers suggests other pathophysiologic variables are likely at play.

Development of a piglet model for cerebrovascular autoregulation assessment with altered PaCO2

IntroductionCerebrovascular autoregulation (CA) capacity can be impaired in the aftermath of acute brain injuries. Altered physiological states, such as hypo- and hypercapnia, affect CA. Although these effects have been demonstrated in several animal experiments, the exact effect of PaCO₂ on the plateau of cerebral blood flow (CBF) across the spectrum of arterial blood pressures has not been fully disclosed. Research questionThe aim was to explore pial vasodynamics in response to changing PaCO₂ in a porcine cranial window model, as preparation for an experimental setup in which the CBF plateau position is investigated under different PaCO₂ conditions. Material and methodsFive piglets were brought under anesthesia, intubated, ventilated and instrumented with a cranial window through which pial arteriolar diameters could be microscopically observed. By changing ventilation to either hyper- or hypoventilation we were able to investigate a range of PaCO2 from 25 till 90 mmHg. ResultsAltering the respiratory rate to manipulate PaCO₂ by ventilation appeared to be feasible and reliable. Discussion and conclusionWe found that ETCO₂ reliably represents PaCO₂ in our model. Pial arteriolar diameter changes followed the direction of PaCO₂ changes, but the effect of PaCO₂ on the diameters was not linear. Only in the hypercapnia setting did we observe a clear and consistent vasodilation of the pial arterioles.

Brain Oxygenation Response to Hypercapnia in Patients with Acute Brain Injury.

Cerebral hypoxia is a frequent cause of secondary brain damage in patients with acute brain injury. Although hypercapnia can increase intracranial pressure, it may have beneficial effects on tissue oxygenation. We aimed to assess the effects of hypercapnia on brain tissue oxygenation (PbtO2). This single-center retrospective study (November 2014 to June 2022) included all patients admitted to the intensive care unit after acute brain injury who required multimodal monitoring, including PbtO2 monitoring, and who underwent induced moderate hypoventilation and hypercapnia according to the decision of the treating physician. Patients with imminent brain death were excluded. Responders to hypercapnia were defined as those with an increase of at least 20% in PbtO2 values when compared to their baseline levels. On a total of 163 eligible patients, we identified 23 (14%) patients who underwent moderate hypoventilation (arterial partial pressure of carbon dioxide [PaCO2] from 44 [42-45] to 50 [49-53] mm Hg; p < 0.001) during the study period at a median of 6 (4-10) days following intensive care unit admission; six patients had traumatic brain injury, and 17 had subarachnoid hemorrhage. A significant overall increase in median PbtO2 values from baseline (21 [19-26] to 24 [22-26] mm Hg; p = 0.02) was observed. Eight (35%) patients were considered as responders, with a median increase of 7 (from 4 to 11) mm Hg of PbtO2, whereas nonresponders showed no changes (from - 1 to 2mm Hg of PbtO2). Because of the small sample size, no variable independently associated with PbtO2 response was identified. No correlation between changes in PaCO2 and in PbtO2 was observed. In this study, a heterogeneous response of PbtO2 to induced hypercapnia was observed but without any deleterious elevations of intracranial pressure.

Positive Pressure Ventilation Treatment Based on Daytime and Night-time Titration in Patients with Obesity Hypoventilation Syndrome: A Randomized Controlled Trial.

Objectives The aim of the present study was to investigate the improvements of gas exchange and excessive daytime sleepiness in patients with obesity hypoventilation syndrome (OHS) in daytime and night-time split polysomnography (DSPSG and NSPSG). Materials and Methods In the present randomized controlled trial, patients with OHS were enrolled in two DSPSG (51 patients) and NSPSG (50 patients) groups in the Bamdad respiratory and sleep research center in Isfahan, Iran. In both groups, the diagnostic polysomnography (PSG) and titration were conducted in one session according to the guidelines of NSPSG. SpO2, PaCO2, and the Epworth Sleepiness Scale (ESS), were measured initially and 12 weeks after treatment. Furthermore, the PSG parameters and the type of treatments for the two groups were recorded and analyzed. Results A total of 101 OHS patients (age: 62.02 ± 12.4 year old; 61 females [60.4%]) were evaluated. There were no significant differences regarding BMI, gender, and AHI between groups ( p > 0.05). Primary SpO2, PaCO2, and ESS were not significantly different between the two groups. After 12 weeks of treatment by continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP), there were significant improvement of SpO2, PaCO2, and ESS score ( p < 0.001). The amount of change of these variables was not different between groups. Among all variables, only the lower SpO2 and higher PaCO2 were associated with response to BiPAP. Discussion There were no significant differences in the number of changes of SpO2, PaCO2, and ESS by treatment in the DSPSG and NSPSG groups. Therefore, DSPSG may be considered as a valuable alternative method for the diagnosis and titration in OHS patients. Clinical Trials IRCT20170512033930N2.

Comparison of noninvasive respiratory support methods in the postoperative period in cardiac surgery patients: a prospective randomized trial

INTRODUCTION: The frequency of respiratory failure in the postoperative period is 17–22 % [1–3]. The most commonly used methods: noninvasive positive pressure mask ventilation (NIPPMV), high-flow nasal cannula (HFNС), noninvasive positive pressure helmet ventilation (NIPPHV). OBJECTIVE: Comparison of the effectiveness of respiratory support methods depending on their effect on gas exchange in patients with mild to moderate respiratory failure in the early period after cardiac surgery. MATERIALS AND METHODS: The study included 42 cardiac surgery patients with 200 &lt; P/F &lt; 300 who were divided into 3 groups depending on the methods of respiratory support used (NIPPMV, HFNС, NIPPHV). The main point of the study is to assess the dynamics of the gas exchange indicators before, during and after their use. RESULTS: All three methods of NIVL contribute to a statistically significant improvement in gas exchange during NIVL, which persisted after the end of therapy (SpO2, PaO2, P/F, Qsp/Qt). In the group with the use of NIPPMV and HFNС an increase in the oxyhemoglobin fraction. In the course of this study, no data were revealed on changes in PaCO2. The largest increase in SpO2 was revealed in groups using a mask and helmet, but at the end of the NIVL session there were no statistically significant differences between the groups. A decrease in the proportion of patients with P/F &lt; 300 after a single session in the NIPPMV group by 2 times, in the HFNC group — by 1.6 times, in the NIPPHV group — by 3.5 times. CONCLUSIONS: Conducting noninvasive respiratory support significantly improves the indicators of oxygenating lung function in the early postoperative period in cardiac surgery patients. NIPPHV and NIPPMV are more effective compared to HFNC. When using a helmet, a higher level of support is required.

Trending Ability of End-Tidal Capnography Monitoring During Mechanical Ventilation to Track Changes in Arterial Partial Pressure of Carbon Dioxide in Critically Ill Patients With Acute Brain Injury: A Monocenter Retrospective Study.

Changes in arterial partial pressure of carbon dioxide (Pa co2 ) may alter cerebral perfusion in critically ill patients with acute brain injury. Consequently, international guidelines recommend normocapnia in mechanically ventilated patients with acute brain injury. The measurement of end-tidal capnography (Et co2 ) allows its approximation. Our objective was to report the agreement between trends in Et co2 and Pa co2 during mechanical ventilation in patients with acute brain injury. Retrospective monocenter study was conducted for 2 years. Critically ill patients with acute brain injury who required mechanical ventilation with continuous Et co2 monitoring and with 2 or more arterial gas were included. The agreement was evaluated according to the Bland and Altman analysis for repeated measurements with calculation of bias, and upper and lower limits of agreement. The directional concordance rate of changes between Et co2 and Pa co2 was evaluated with a 4-quadrant plot. A polar plot analysis was performed using the Critchley methods. We analyzed the data of 255 patients with a total of 3923 paired ΔEt co2 and ΔPa co2 (9 values per patient in median). Mean bias by Bland and Altman analysis was -8.1 (95 CI, -7.9 to -8.3) mm Hg. The directional concordance rate between Et co2 and Pa co2 was 55.8%. The mean radial bias by polar plot analysis was -4.4° (95% CI, -5.5 to -3.3) with radial limit of agreement (LOA) of ±62.8° with radial LOA 95% CI of ±1.9°. Our results question the performance of trending ability of Et co2 to track changes in Pa co2 in a population of critically ill patients with acute brain injury. Changes in Et co2 largely failed to follow changes in Pa co2 in both direction (ie, low concordance rate) and magnitude (ie, large radial LOA). These results need to be confirmed in prospective studies to minimize the risk of bias.

Comparison of mathematically arterialised venous blood gas sampling with arterial, capillary, and venous sampling in adult patients with hypercapnic respiratory failure: a single-centre longitudinal cohort study

BackgroundAccurate arterial blood gas (ABG) analysis is essential in the management of patients with hypercapnic respiratory failure, but repeated sampling requires technical expertise and is painful. Missed sampling is common...

Dual titration of minute ventilation and sweep gas flow to control carbon dioxide variations in patients on venovenous extracorporeal membrane oxygenation

BackgroundThe implantation of venovenous extracorporeal membrane oxygenation (VV-ECMO) support to manage severe acute respiratory distress syndrome generates large variations in carbon dioxide partial pressure (PaCO2) that are associated with intracranial bleeding. We assessed the feasibility and efficacy of a pragmatic protocol for progressive dual titration of sweep gas flow and minute ventilation after VV-ECMO implantation in order to limit significant PaCO2 variations.Patients and methodsA protocol for dual titration of sweep gas flow and minute ventilation following VV-ECMO implantation was implemented in our unit in September 2020. In this single-centre retrospective before-after study, we included patients who required VV-ECMO from March, 2020 to May, 2021, which corresponds to two time periods: from March to August, 2020 (control group) and from September, 2020 to May, 2021 (protocol group). The primary endpoint was the mean absolute change in PaCO2 in consecutive arterial blood gases samples drawn over the first 12 h following VV-ECMO implantation. Secondary endpoints included large (> 25 mmHg) initial variations in PaCO2, intracranial bleedings and mortality in both groups.ResultsFifty-one patients required VV-ECMO in our unit during the study period, including 24 in the control group and 27 in the protocol group. The protocol was proved feasible. The 12-h mean absolute change in PaCO2 was significantly lower in patients of the protocol group as compared with their counterparts (7 mmHg [6–12] vs. 12 mmHg [6–24], p = 0.007). Patients of the protocol group experienced less large initial variations in PaCO2 immediately after ECMO implantation (7% vs. 29%, p = 0.04) and less intracranial bleeding (4% vs. 25%, p = 0.04). Mortality was similar in both groups (35% vs. 46%, p = 0.42).ConclusionImplementation of our protocol for dual titration of minute ventilation and sweep gas flow was feasible and associated with less initial PaCO2 variation than usual care. It was also associated with less intracranial bleeding.

Hypercapnia under controlled mechanical ventilation in patients with high-risk acute pulmonary thromboembolism

Objective: To evaluate the variation of arterial partial pressure of carbon dioxide (PaCO2) in patients with high-risk pulmonary embolism under mechanical ventilation. Methods: We retrospectively analyzed the cases of high-risk pulmonary embolism who underwent intravenous thrombolysis in Peking Union Medical College Hospital from January 1, 2012, to May 1, 2022. The enrolled patients were divided into a mechanical-ventilated group and an active-breathing group according to whether they received invasive mechanical ventilation or not. The level of PaCO2 under active breathing between the two groups, the changes in PaCO2 before intubation, after intubation and after thrombolysis in the mechanical-ventilated group were compared. The 14-day all-cause mortality of the two groups was calculated and compared. Results: A total of 49 patients with high-risk pulmonary embolism were enrolled, including 22 patients in the mechanical-ventilated group and 27 patients in the active-breathing group. Before intubation, PaCO2 in both groups was lower than normal without statistically significant difference between the two groups. After effective thrombolysis therapy, PaCO2 in both groups recovered to the normal range. In the mechanical-ventilated group, PaCO2 significantly increased 11-147 min after intubation and returned to the normal range after thrombolysis therapy. The 14-day mortality in the mechanical-ventilated group was 54.5%, while all patients in the active-breathing group survived. Conclusions: Under mechanical controlled ventilation, patients with high-risk pulmonary embolism could represent hypercapnia which resolved after effective thrombolytic therapy. In mechanical ventilated patients with sudden-onset hypoxemia and hypercapnia, the possibility of high-risk pulmonary embolism should be considered.

Effects of an asymmetrical high flow nasal cannula interface in hypoxemic patients

BackgroundOptimal noninvasive respiratory support for patients with hypoxemic respiratory failure should minimize work of breathing without increasing the transpulmonary pressure. Recently, an asymmetrical high flow nasal cannula (HFNC) interface (Duet, Fisher & Paykel Healthcare Ltd), in which the caliber of each nasal prong is different, was approved for clinical use. This system might reduce work of breathing by lowering minute ventilation and improving respiratory mechanics.MethodsWe enrolled 10 patients ≥ 18 years of age who were admitted to the Ospedale Maggiore Policlinico ICU in Milan, Italy, and had a PaO2/FiO2 < 300 mmHg during HFNC support with a conventional cannula. We investigated whether the asymmetrical interface, compared to a conventional high flow nasal cannula, reduces minute ventilation and work of breathing. Each patient underwent support with the asymmetrical interface and the conventional interface, applied in a randomized sequence. Each interface was provided at a flow rate of 40 l/min followed by 60 l/min. Patients were continuously monitored with esophageal manometry and electrical impedance tomography.ResultsApplication of the asymmetrical interface resulted in a −13.5 [−19.4 to (−4.5)] % change in minute ventilation at a flow rate of 40 l/min, p = 0.006 and a −19.6 [−28.0 to (−7.5)] % change at 60 l/min, p = 0.002, that occurred despite no change in PaCO2 (35 [33–42] versus 35 [33–43] mmHg at 40 l/min and 35 [32–41] versus 36 [32–43] mmHg at 60 l/min). Correspondingly, the asymmetrical interface lowered the inspiratory esophageal pressure–time product from 163 [118–210] to 140 [84–159] (cmH2O*s)/min at a flow rate of 40 l/min, p = 0.02 and from 142 [123–178] to 117 [90–137] (cmH2O*s)/min at a flow rate of 60 l/min, p = 0.04.The asymmetrical cannula did not have any impact on oxygenation, the dorsal fraction of ventilation, dynamic lung compliance, or end-expiratory lung impedance, suggesting no major effect on PEEP, lung mechanics, or alveolar recruitment.ConclusionsAn asymmetrical HFNC interface reduces minute ventilation and work of breathing in patients with mild-to-moderate hypoxemic respiratory failure supported with a conventional interface. This appears to be primarily driven by increased ventilatory efficiency due to enhanced CO2 clearance from the upper airway.

A Comparative Study Between pH and PaCO2 Changes during Laparotomy VS Laparoscopic Abdominal Surgeries

A Comparative Study Between pH and PaCO2 Changes during Laparotomy VS Laparoscopic Abdominal Surgeries

Efficacy and safety of high-flow nasal cannula therapy in elderly patients with acute respiratory failure

IntroductionTo assess the efficacy and safety of high-flow nasal cannula (HFNC) in elderly patients with acute respiratory failure (ARF) not due to COVID-19, refractory to treatment with conventional oxygen therapy and/or intolerant to noninvasive ventilation (NIV) or continuous positive airway pressure (CPAP) and without criteria for admission to intensive care units (ICU). MethodsProspective observational study of patients with ARF treated with HFNC who presented clinical and arterial blood gas deterioration after 24 h of medical treatment and oxygenation by conventional systems. The degree of dyspnoea, gas exchange parameters (arterial O2 pressure/inspired O2 fraction ratio (PaO2/FiO2); oxygen saturation measured by oximetry/ inspired fraction of oxygen (Sp02/Fi02), ROX index), degree of patient tolerance and mortality were evaluated. These were measured at discharge from the emergency department (ED), 24 h after treatment with conventional oxygenation and 60, 120 min and 24 h after initiation of HFNC. The results were analyzed for all patients as a whole and for patients with hypercapnia (arterial carbon dioxide tension (PaCO2) < 45 mmHg) separately. Results200 patients were included in the study between November 2019 and November 2020, with a mean age of 83 years, predominantly women (61.9%), obese (Body Mass Index (BMI) 31.1), with high comorbidity (Charlson index 4) and mild-moderate degree of dependence (Barthel 60). A number of 128 patients (64%) were hypercapnic. None had respiratory acidosis (pH 7.39). Evaluation at 60 min, 120 min and 24 h showed significant improvement in all patients and in the subgroup of hypercapnic patients with respect to baseline parameters in respiratory rate (RR), dyspnoea, ROX index, PaO2/FiO2, SpO2/FiO2 and patient comfort. No changes in PaCO2 or level of consciousness were observed. HFNC was well tolerated. Ten patients (5%) died due to progression of the disease causing ARF. ConclusionsHFNC is an effective and safe alternative in elderly patients with ARF not due to COVID-19, refractory to treatment with conventional oxygen therapy and/or intolerant to NIV or CPAP and without criteria for admission to ICU.

Laryngeal mask airway facilitates a safe and smooth emergence from anesthesia in patients undergoing craniotomy: a prospective randomized controlled study

BackgroundEndotracheal extubation under deep anesthesia (deep extubation) has been proved to present stable hemodynamics and steady intracranial pressure during emergence from anesthesia in patients undergoing craniotomy. This study aims to examine, in comparison with deep extubation, if a laryngeal mask airway (LMA) could provide a safer and smoother emergence from anesthesia in patients undergoing craniotomy.MethodsThis prospective randomized controlled study was conducted on patients undergoing elective craniotomy for brain tumors. After the complement of the surgical procedure, the patients had anesthesia maintained with end-tidal sevoflurane concentration 2.5% and also fully regained muscle power (Time Zero), they were randomly assigned to ETT Group (n = 29) for deep extubation or to LMA Group (n = 29), where the endotracheal tube was replaced by a laryngeal mask airway. The primary outcomes were respiratory complications, airway interventions and hemodynamic changes through emergence from anesthesia till 30 min following Time Zero. The secondary outcomes were re-operation incidence in 24 h, stay time in the intensive care unit and postoperative hospital days.ResultsAt 5 min before Time Zero either oxygen partial pressures (PaO2) or carbon dioxide partial pressures (PaCO2) between the two groups were comparable. No significant PaCO2 change was noted in both groups in 5 min after Time Zero, yet there was a remarkably lower PaO2 in ETT Group at that time point, 188.9 (± 71.1) in ETT Group vs 264.4 (± 85.4) in LMA Group. In ETT Group, coughs and snores were considerably more frequent, and thus more interventions were needed to maintain adequate respiration. From Time Zero on, blood pressures (systolic, diastolic and mean) and heart rates in ETT Group were generally higher than those in LMA Group, but the differences were insignificant at all time points except heart rate at 10 min after Time Zero. The secondary outcomes between the two groups were similar.ConclusionsCompared with deep extubation, a LMA, as a temporary airway replacement, facilitates a safer and smoother emergence from anesthesia for patients undergoing craniotomy, in terms of better oxygen saturation, fewer respiratory complications and fewer airway interventions.Trial registrationThe study was conducted after receiving approval from Institutional Review Board of Chang Gung Memorial Hospital, Linkou Branch, Taiwan (registration number 202102115A3; January 27, 2022), and the clinicaltrials.gov (NCT05253404) on 23 February 2022.

Association between rate of change in PaCO2 and functional outcome for patients with hypercapnia after out-of-hospital cardiac arrest: Secondary analysis of a randomized clinical trial

BackgroundNormocapnia is suggested for post resuscitation care. For patients with hypercapnia after cardiac arrest, the relationship between rate of change in partial pressure of carbon dioxide (PaCO2) and functional outcome was unknown. MethodsThis was the secondary analysis of Resuscitation Outcomes Consortium (ROC) amiodarone, lidocaine, and placebo (ALPS) trial. Patients with at least 2 PaCO2 recorded and the first indicating hypercapnia (PaCO2 > 45 mmHg) after return of spontaneous circulation (ROSC) were included. The rate of change in PaCO2 was calculated as the ratio of the difference between the second and first PaCO2 to the time interval. The primary outcome was modified Rankin Score (mRS), dichotomized to good (mRS 0–3) and poor (mRS 4–6) outcomes at hospital discharge. The independent relationship between rate of change in PaCO2 and outcome was investigated with multivariable logistic regression model. ResultsA total of 746 patients with hypercapnia were included for analysis, of which 264 (35.4%) patients had good functional outcome. The median rate of change in PaCO2 was 4.7 (interquartile range [IQR] 1.7–12) mmHg per hour. After adjusting for confounders, the rate of change in PaCO2 (odds ratio [OR] 0.994, confidence interval [CI] 0.985–1.004, p = 0.230) was not associated the functional outcome. However, rate of change in PaCO2 (OR 1.010, CI 1.001–1.019, p = 0.029) was independently associated with hospital mortality. ConclusionsFor OHCA patients with hypercapnia on admission, the rate of change in PaCO2 was not independently associated with functional outcome; however, there was a significant trend that higher decreased rate was associated with increased hospital mortality.

Challenging neurovascular coupling through complex and variable duration cognitive paradigms: A subcomponent analysis.

A similar pattern of cerebral blood velocity (CBv) response has been observed for neurovascular coupling (NVC) assessment with cognitive tasks of varying complexity and duration. This lack of specificity could result from parallel changes in arterial blood pressure (BP) and PaCO2, which could confound the estimates of NVC integrity. Healthy participants (n=16) underwent recordings at rest (5min sitting) and during randomized paradigms of different complexity (naming words (NW) beginning with P-, R-, V- words and serial subtractions (SS) of 100-2, 100-7, 1000-17, with durations of 5, 30 and 60s). Bilateral CBv (middle cerebral arteries, transcranial Doppler), end-tidal CO2 (EtCO2, capnography), blood pressure (BP, Finapres) and heart rate (HR, ECG) were recorded continuously. The bilateral CBv response to all paradigms was classified under objective criteria to select only responders, then the repeated data were averaged between visits. Bilateral CBv change to tasks was decomposed into the relative contributions (subcomponents) of arterial BP (VBP; neurogenic), critical closing pressure (VCrCP; metabolic) and resistance area product (VRAP; myogenic). A temporal effect was demonstrated in bilateral VBP and VRAP during all tasks (p<0.002), increased VBP early (between 0 and 10s) and followed by decreases of VRAP late (25-35s) in the response. VCrCP varied by complexity and duration (p<0.046). The main contributions to CBv responses to cognitive tasks of different complexity and duration were VBP and VRAP, whilst a smaller contribution from VCrCP would suggest sensitivity to metabolic demands. Further studies are needed to assess the influence of different paradigms, ageing and cerebrovascular conditions.

Efficacy and safety of remifentanil dose titration to correct the spontaneous hyperventilation in aneurysmal subarachnoid haemorrhage: protocol and statistical analysis for a prospective physiological study

IntroductionSpontaneous hyperventilation (SHV) is common in aneurysmal subarachnoid haemorrhage (aSAH). The reduction in arterial partial pressure of carbon dioxide (PaCO2) may change the brain physiology, such as haemodynamics, oxygenation, metabolism...