Increase In PaCO2 Research Articles

Determinants of venous return in steady-state physiology and asphyxia-induced circulatory shock and arrest: an experimental study

BackgroundMean circulatory filling pressure (Pmcf) provides information on stressed volume and is crucial for maintaining venous return. This study investigated the Pmcf and other determinants of venous return in dysrhythmic and asphyxial circulatory shock and arrest.MethodsTwenty Landrace/Large-White piglets were allocated into two groups of 10 animals each. In the dysrhythmic group, ventricular fibrillation was induced with a 9 V cadmium battery, while in the asphyxia group, cardiac arrest was induced by stopping and disconnecting the ventilator and clamping the tracheal tube at the end of exhalation. Mean circulatory filling pressure was calculated using the equilibrium mean right atrial pressure at 5–7.5 s after the onset of cardiac arrest and then every 10 s until 1 min post-arrest. Successful resuscitation was defined as return of spontaneous circulation (ROSC) with a MAP of at least 60 mmHg for a minimum of 5 min.ResultsAfter the onset of asphyxia, a ΔPmca increase of 0.004 mmHg, 0.01 mmHg, and 1.26 mmHg was observed for each mmHg decrease in PaO2, each mmHg increase in PaCO2, and each unit decrease in pH, respectively. Mean Pmcf value in the ventricular fibrillation and asphyxia group was 14.81 ± 0.5 mmHg and 16.04 ± 0.6 mmHg (p < 0.001) and decreased by 0.031 mmHg and 0.013 mmHg (p < 0.001), respectively, for every additional second passing after the onset of cardiac arrest. With the exception of the 5–7.5 s time interval, post-cardiac arrest right atrial pressure was significantly higher in the asphyxia group. Mean circulatory filling pressure at 5 to 7.5 s after cardiac arrest predicted ROSC in both groups, with a cut-off value of 16 mmHg (AUC = 0.905, p < 0.001).ConclusionMean circulatory filling pressure was higher in hypoxic hypercapnic conditions and decreased at a lower rate after cardiac arrest compared to normoxemic and normocapnic state. A Pmcf cut-off point of 16 mmHg at 5–7.5 s after cardiac arrest can highly predict ROSC.

Indications of oxygenation after thoracic operations depending on the method of selection of dual endobronchial tube used

Annotation. Pulmonary complications are a key problem in the postoperative period in patients with diseases of the thoracic cavity. They are characterized as the main factors of longer recovery and hospital mortality. The aim of the study was to compare the indicators of oxygenation of patients and the number of postoperative pulmonary complications after thoracic surgery, depending on the method used to select a dual endobronchial tube. The study was performed on 192 patients with diseases of the thoracic cavity (esophagus, lungs, mediastinum), operated on in the thoracoabdominal department of the Shalimov National Institute of Surgery and Tranplantology. A retrospective comparison group – 96 patients after thoracic surgery, which used the choice of DLT size according to the well-known method of Slinger “according to the patient's height”. The study group consisted of 96 patients after thoracic surgery, in which the choice of the size of the dual endobronchial tube was used according to the developed method (according to the formula that evaluates morphometric indicators of height, sex and diameter of the left main bronchus). EZR v 1.54 statistical software was used for statistical calculations. (graphical user interface for statistical software R version 4.0.3, R Foundation for Statistical Computing, Vienna, Austria). Pulmonary complications developed in 33 (34.4%) patients of the control group and in 13 (13.5%) patients of the study group, the difference was statistically significant, p=0.001. One-factor analysis revealed a link between the risk of complications and the indicators method, sex, PaCO2, PaO2. For the study group, the risk of complications is lower (p=0.001), BP=0.30 (95% CI 0.15-0.61) compared with the control group. The risk of complications for men is higher (p=0.048), BP=2.33 (95% CI 1.01–5.37) compared to women. An increase in the risk of complications with an increase in PaCO2 (p&lt;0.001), BP=1.34 (95% CI 1.21-1.49) with an increase in the indicator by 1 unit, respectively. With increasing PaO2, the risk of complications decreases (p&lt;0.001): BP=0.96 (95% CI 0.94-0.98) – with increasing 1 unit. Thus, the application of the proposed method in comparison with the traditional method reduces (p=0.001) the number of postoperative pulmonary complications by 2.5 times (from 34.4% to 13.5%).

Diagnosis and management of intra-operative pulmonary embolism under general anaesthesia in a peripheral tertiary care centre with limited resources.

Sir, It is difficult to detect and diagnose acute pulmonary embolism (APE) in patients under general anaesthesia (GA) as signs and symptoms such as dyspnoea, chest pain, haemoptysis and syncope are not evident.[1] A 64-year-old male, with left sided carcinoma buccal mucosa and American Society of Anesthesiologists physical status II, was listed for left anterior hemi-mandibulectomy with bilateral multinodal neck dissection and left sided pectoral muscle musculocutaneous flap (PMMC) under GA. Preoperative contrast enhanced computed tomography (CECT) thorax was unremarkable. After induction, haemodynamics remained stable during excision of the primary lesion. Approximately, 5 hours into the surgery, while raising the PMMC, the patient developed sudden pronounced hypotension with a mean arterial pressure of 45 mmHg and a decrease in end tidal carbon di-oxide (EtCO2) 38 mmHg to 15 mmHg. This was associated with bradycardia (heart rate 44-48/min) and a gradual fall in oxygen saturation to 86-88%. Peak airway pressures gradually increased from 21 cmH2O to 32 cmH2O with an associated increase in plateau pressures from 19 cmH2O to 29 cmH2O. Central venous pressures were elevated and bilateral breath sounds were marginally reduced with no adventitious sounds. There was no significant acute blood loss, nor any evidence of sepsis. Immediately, the inhalational agent was switched off and the fraction of inspiratory oxygen increased to 100%. Intravenous mephentermine 6 mg (two boluses), hydrocortisone 100 mg and atropine 0.6 mg were administered intravenously. A single intravenous adrenaline bolus of 10 μg was subsequently administered, followed by an infusion at the rate of 0.02 μg/kg/min. Immediate arterial blood gas (ABG) analysis showed hypercarbia as well as hypoxia [Table 1a]. Transthoracic echocardiography (TTE) through subcostal four chamber view showed dilated and strained right heart chambers (McConnell sign) and distended inferior vena cava [Figure 1a and b]. A probable diagnosis of APE was made.Table 1: Arterial blood gas analysisFigure 1: (a) Echo showing dilated IVC and RA (b) Dilated RA and RV. IVC: Inferior vena cava; RA: Right atrium; RV: Right ventricleOur institute is a tertiary cancer care centre in a small town with limited resources. After adequate resuscitation, a joint consensus among operating room team members was made for pharmacological treatment. Unfractionated heparin (UFH) 5000 IU was administered intra-venously. Activated partial thromboplastin time (APTT) was maintained 1.5-2 times of the normal value. We were in the middle of the surgery (with tumour excised and the PMMC flap raised), and the haemodynamics had stabilised. Repeat blood gas analysis came normal [Table 1b]. So, we decided to complete the surgery. Post-surgery, the patient was kept on mechanical ventilation. Vitals in the postoperative period remained stable. A dose of 2500 IU of UFH was repeated as the reported APTT was 38.3 seconds. The patient underwent computed tomographic pulmonary angiography which showed no filling defect [Figure 2] and was shifted onto subcutaneous low molecular weight heparin 60 mg twice a day. On post-operative day (POD) 1, the patient was weaned off the ventilator. He was shifted to the ward on POD 2. He was found haemodynamically stable during follow-up.Figure 2: CT Pulmonary Angiography (Post Surgery)APE leads to significant separation of EtCO2 and PaCO2 values intra-operatively. It causes a sudden decrease in EtCO2 and an increase in PaCO2. This separation in EtCO2 and PaCO2 values is also an important tool to measure thrombolysis under GA.[1] TTE coupled with EtCO2 changes seems to be useful in intra-operative cardio- circulatory failure to exclude other differential diagnoses.[2] The 2019 consensus European Society of Cardiology (ESC) guidelines strongly recommend intravenous UFH as a treatment of choice in haemodynamically unstable APE.[3] Catheter-directed therapy (CDT) had been done for APE.[4] CDT is recommended by the American College of Chest Physicians as second-line therapy for massive pulmonary embolism.[5] Our case is a classic example of APE in head and neck malignancy. The involvement of a multidisciplinary team can also help in preparedness for emergent and unanticipated situations.[6] We emphasise that vigilant monitoring of EtCO2, timely use of TTE and systemic anticoagulation with adequate intraoperative haemodynamic resuscitation can lead to safe completion of surgery with minimal morbidity and mortality. Though UFH is not a recommended modality in the intra-operative period, due to the limitations of our set -up, CDT was beyond our purview. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to concealidentity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

Systems on Top of Nasal Cannula Improve Oxygen Delivery in Patients with COVID-19: a Randomized Controlled Trial.

BackgroundTreating hypoxemia while meeting the soaring demands of oxygen can be a challenge during the COVID-19 pandemic.ObjectiveTo determine the efficacy of the surgical facemask and the double-trunk mask on top of the low-flow oxygen nasal cannula on arterial partial pressure of oxygen (PaO2) in hypoxemic COVID-19 patients.DesignRandomized controlled trial.ParticipantsHospitalized adults with COVID-19 and hypoxemia treated with the low-flow nasal cannula were enrolled between November 13, 2020, and March 05, 2021.InterventionsPatients were randomized in a 1:1:1 ratio to receive either the nasal cannula alone (control) or the nasal cannula covered by the surgical facemask or the double-trunk mask. Arterial blood gases were collected at baseline and 30 min after the use of each system. The oxygen output was adapted afterwards to retrieve the baseline pulse oxygen saturation. The final oxygen output value was recorded after another 30-min period.Main MeasuresThe primary outcome was the absolute change in PaO2. Secondary outcomes included changes in oxygen output, arterial partial pressure of carbon dioxide (PaCO2), vital parameters, and breathlessness.Key ResultsArterial blood samples were successfully collected in 24/27 (8 per group) randomized patients. Compared to the nasal cannula alone, PaO2 increased with the surgical facemask (mean change: 20 mmHg, 95% CI: 0.7–38.8; P = .04) and with the double-trunk mask (mean change: 40 mmHg; 95% CI: 21–59; P < .001). Oxygen output was reduced when adding the surgical facemask (median reduction: 1.5 L/min [95% CI: 0.5–4.5], P < .001) or the double-trunk mask (median reduction: 3.3 L/min [95% CI: 2–5], P < .001). The double-trunk mask was associated with a PaCO2 increase of 2.4 mmHg ([95% CI: 0–4.7], P = .049). Neither mask influenced vital parameters or breathlessness.ConclusionsThe addition of the surgical facemask or the double-trunk mask above the nasal cannula improves arterial oxygenation and reduces oxygen consumption.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11606-022-07419-2.

Study of the relationship between regional cerebral saturation and pCO2 changes during mechanical ventilation to evaluate modifications in cerebral perfusion in a newborn piglet model.

Near-infrared spectroscopy (NIRS) could be a useful continuous, non-invasive technique for monitoring the effect of partial pressure of carbon dioxide (PaCO2) fluctuations in the cerebral circulation during ventilation. The aim of this study was to examine the efficacy of NIRS to detect acute changes in cerebral blood flow following PaCO2 fluctuations after confirming the autoregulation physiology in piglets. Fourteen piglets (<72 h of life) were studied. Mean arterial blood pressure, oxygen saturation, pH, glycemia, hemoglobin, electrolytes, and temperature were monitored. Eight animals were used to evaluate brain autoregulation, assessing superior cava vein Doppler as a proxy of cerebral blood flow changing mean arterial blood pressure. Another 6 animals were used to assess hypercapnia generated by decreasing ventilatory settings and complementary CO2 through the ventilator circuit and hypocapnia due to increasing ventilatory settings. Cerebral blood flow was determined by jugular vein blood flow by Doppler and continuously monitored with NIRS. A decrease in PaCO2 was observed after hyperventilation (47.6±2.4 to 29.0±4.9 mmHg). An increase in PaCO2 was observed after hypoventilation (48.5±5.5 to 90.4±25.1 mmHg). A decrease in cerebral blood flow after hyperventilation (21.8±10.4 to 15.1±11.0 mL/min) and an increase after hypoventilation (23.4±8.4 to 38.3±10.5 mL/min) were detected by Doppler ultrasound. A significant correlation was found between cerebral oxygenation and Doppler-derived parameters of blood flow and PaCO2. Although cerebral NIRS monitoring is mainly used to detect changes in regional brain oxygenation, modifications in cerebral blood flow following experimental PaCO2 changes were detected in newborn piglets when no other important variables were modified.

Relation between pulmonary tuberculosis and chronic obstructive pulmonary disease

Background/aim Some studies have showed a link between pulmonary tuberculosis (TB) and the growth of chronic obstructive pulmonary disease (COPD). So, the aim of this work was to study the prevalence of TB-associated COPD among patients with COPD. Patients and methods This study included 500 patients with a precise COPD diagnosis. It has been established in patients with preceding history of pulmonary or extrapulmonary TB. The patients were separated into two equivalent groups: group 1 contained 50 patients with TB-associated COPD, and group 2 contained 50 patients with COPD but without TB history. All included patients underwent full history, complete clinical examination, chest radiography, arterial blood gases, and pulmonary function tests. Results The prevalence of TB-associated COPD among the 500 patients with COPD was 16%. There was a significant difference in smoking habit between both groups (P=0.001). The mainstream of TB-associated COPD group was nonsmokers, even though most patients with COPD without TB were smokers. There was a significant increase in exacerbations in TB-associated COPD group when equated with patients with COPD without TB (P=0.02). Additionally, there was a significant increase in PaCO2 of the TB-associated COPD group compared with the other group (P=0.02). Moreover, this study recorded significant relation between the beginning of COPD and the number of anti-TB courses (P=0.001), and increased number of anti-TB courses was associated with earlier onset of COPD. The authors observed significant reduction in PFTs in patients who received two or more courses compared with patients who had customary only one course. Conclusions TB should be considered in patients with COPD, and COPD can be a consequence of TB even in the absence of any other risk factors. COPD-associated TB is associated with frequent exacerbations, worsened pulmonary function tests, and earlier start of COPD compared with patients with COPD owing to other risk factors.

Protecting the Brain During Pediatric DKA Treatment.

The most feared complication when treating diabetic ketoacidosis (DKA) is sudden onset of neurologic deterioration, which may include central herniation. Clinical brain swelling complicates 0.5% to 1% of pediatric DKA episodes, and when it occurs, permanent morbidity and mortality are common. However, children in DKA are known to have subclinical brain edema.1 Factors that lead to clinical edema and neurologic abnormalities are not clear. The key issue is to determine the best way to manage these patients, who are dehydrated, severely hyperglycemic, and may have hypo or hypernatremia and severe acidosis.In this issue of Pediatrics, Glaser et al2 provide clinically helpful and reassuring findings in a comparison of 4 intravenous infusion protocols, with varying sodium concentrations and differing rates of rehydration.2,3 There was no difference in rates of neurologic dysfunction or clinically apparent brain swelling in any of the groups.1,2 Even more reassuring, there were no significant differences in these outcomes among those whose serum sodium remained stable or increased versus those whose sodium fell during the first 12 hours of therapy. An important clinical lesson is that this study prospectively demonstrated that rehydration over 1.5 to 2 days does not increase the risk of neurologic injury.2Prevention of DKA is difficult because just over half of episodes are the initial presentation of diabetes.3 Assessment of sensorium can be challenging because headache, throat pain, difficulty waking, and cooperation in infants and younger children can be difficult to judge. The primary study from which Glaser used data included 1389 episodes of DKA in 1255 children. There were 48 episodes (3.5%) when the Glasgow Coma Score was &lt;14 for 2 assessments, and clinically apparent brain injury occurred in 12 episodes (0.9%).3 However, they did not find a significant difference in depression of Glasgow Coma Score or in clinically apparent brain injury among the 4 rehydration protocols.2,3Neuroimaging with MRI and apparent diffusion coefficient (ADC) of water, diffusion weighted images, and spectroscopy reveal that DKA is associated with increased water content in brain tissues supplied by the anterior and middle cerebral arteries with increased perfusion; however, the mean ADCs are abnormally elevated. This differs from what would be predicted by the osmotic disequilibrium theory because the ratio of extracellular volume to total tissue volume determines in part the ADC and should decrease.4,5 Clinical features that were significantly associated with severity of ADC increases during DKA were hypocarbia and elevated serum urea nitrogen but not glucose, sodium, or osmolality.6–8Previous studies with serial neuroimaging of children receiving faster versus slower rehydration during DKA did not differ significantly in the risk of brain edema.9 This previous work, also conducted by Glaser, helped to establish the foundation for this current study to assess different strategies for rehydration.What other pathophysiology occurs that might lead to neurologic injury and brain edema? The brain autoregulates blood flow to meet metabolic needs across a wide range of blood pressure but cerebral blood flow is highly responsive to partial pressure carbon dioxide (paco2). Acute hyperventilation causes vasoconstriction and severe hypocarbia can cause brain ischemia. Although the hypocarbia during DKA causes a compensatory respiratory alkalosis to increase blood pH, the cerebrospinal fluid (CSF) pH typically is normal before treatment. As blood ketosis decreases and the blood paco2 increases, the CSF becomes acidotic. It is important to remember that administration of bicarbonate exacerbates the CSF acidosis associated with DKA treatment. Likewise, a sudden relative increase in paco2 will increase intracranial pressure and CSF acidosis. Airway manipulation should include targeting the child’s baseline paco2 rather than normal values.The current state-of-the-art method to prevent neurologic abnormalities and clinical brain swelling in DKA is not dependent on specific fluid administration but instead on earlier recognition and treatment to avoid profound acidosis and hyperventilation. Current imaging data do not implicate rehydration regimens or changes in blood glucose or sodium with progression to clinical brain edema. The astute clinician will need to rehydrate carefully while paying attention to neurologic status, sustained ventilation, and acid–base status to protect the brain from worsening edema.

Increasing mean arterial pressure or cardiac output in comatose out-of-hospital cardiac arrest patients undergoing targeted temperature management: Effects on cerebral tissue oxygenation and systemic hemodynamics

IntroductionFew data exist on the effects of increasing norepinephrine doses or increasing arterial CO2 (PaCO2) on hemodynamics and cerebral oxygenation in comatose out-of-hospital cardiac arrest (OHCA) patients. MethodsWe prospectively studied 10 resuscitated OHCA-patients undergoing targeted temperature management (36C°). The trial consisted of 5 phases with 20 minutes steady state in-between: Phase 1–4 were increasing doses of norepinephrine to reach targets of mean arterial pressure (MAP). First 65, second 75, third 85, fourth 65 mmHg again. In the fifth phase, MAP was constant while PaCO2 was increased to 6.5–7.3 kPa to increase cardiac output. Primary outcome was cerebral near-infrared spectroscopy (NIRS). Secondary outcomes were hemodynamic variables from Swan-Ganz catheters and blood samples from the radial artery and jugular bulb. ResultsTo reach a MAP at 85 mmHg, norepinephrine was increased from 0.11 ± 0.02 to 0.18 ± 0.02 µg/kg/min (P < 0.001). Norepinephrine uptitration significantly increased systemic vascular resistance (SVR) and pulmonary vascular resistance, without affecting cardiac output, heart rate or cerebral oxygenation.Increasing PaCO2, resulted in a significant increase in cardiac output and cerebral NIRS, but arterial-venous cerebral oxygen-uptake decreased. Norepinephrine demand to keep MAP at 65 mmHg was unaffected by increasing PaCO2. ConclusionsA short-term increase in MAP with norepinephrine in resuscitated comatose cardiac arrest-patients is associated with increased SVR and pulmonary vascular resistance without affecting cardiac output or cerebral NIRS. Increased cardiac output caused by an increase in PaCO2 increased cerebral NIRS, but not cerebral oxygen uptake.

Acute Responses to Oxygen Delivery via High Flow Nasal Cannula in Patients with Severe Chronic Obstructive Pulmonary Disease-HFNC and Severe COPD.

Differences in oxygen delivery methods to treat hypoxemia have the potential to worsen CO2 retention in chronic obstructive lung disease (COPD). Oxygen administration using high flow nasal cannula (HFNC) has multiple physiological benefits in treating respiratory failure including reductions in PaCO2 in a flow-dependent manner. We hypothesized that patients with COPD would develop worsening hypercapnia if oxygen fraction was increased without increasing flow rate. We evaluated the acute response to HFNC in subjects with severe COPD when flow remained constant and inspired oxygen was increased. In total, 11 subjects with severe COPD (FEV1 < 50%) on supplemental oxygen with baseline normocapnia (PaCO2 < 45 mm Hg; n = 5) and hypercapnia (PaCO2 ≥ 45 mm Hg; n = 6) were studied. Arterial blood gas responses were studied at three timepoints: Baseline, HFNC at a flow rate of 30 L/min at resting oxygen supplementation for 1 h, and FiO2 30% above baseline with the same flow rate for the next hour. The primary endpoint was the change in PaCO2 from baseline. No significant changes in PaCO2 were noted in response to HFNC applied at baseline FiO2 in the normocapnic and hypercapnic group. At HFNC with FiO2 30% above baseline, the normocapnic group did not show a change in PaCO2 (baseline: 38.9 ± 1.8 mm Hg; HFNC at higher FiO2: 38.8 ± 3.1 mm Hg; p = 0.93), but the hypercapnic group demonstrated significant increase in PaCO2 (baseline: 58.2 ± 9.3 mm Hg; HFNC at higher FiO2: 63.3 ± 10.9 mm Hg; p = 0.025). We observed worsening hypercapnia in severe COPD patients and baseline hypercapnia who received increased oxygen fraction when flow remained constant. These data show the need for careful titration of oxygen therapy in COPD patients, particularly those with baseline hypercapnia when flow rate is unchanged.

Prone Position in Mechanically Ventilated COVID-19 Patients: A Multicenter Study.

Background: The prone position (PP) is increasingly used in mechanically ventilated coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS) patients. However, studies investigating the influence of the PP are currently lacking in these patients. This is the first study to investigate the influence of the PP on the oxygenation and decarboxylation in COVID-19 patients. Methods: A prospective bicentric study design was used, and in mechanically ventilated COVID-19 patients, PP was indicated from a partial pressure of oxygen in arterial blood (PaO2)/fraction of inspired oxygen (FIO2) ratio of <200. Patients were left prone for 16 h each. Pressure levels, FIO2, were adjusted to ensure a PaO2 greater than 60 mmHg. Blood gas analyses were performed before (baseline 0.5 h), during (1/2/5.5/9.5/13 h), and after being in the PP (1 h), the circulatory/ventilation parameters were continuously monitored, and lung compliance (LC) was roughly calculated. Responders were defined compared to the baseline value (PaO2/FIO2 ratio increase of ≥15%; partial pressure of carbon dioxide (PaCO2) decrease of ≥2%). Results: 13 patients were included and 36 PP sessions were conducted. Overall, PaO2/FIO2 increased significantly in the PP (p < 0.001). Most PaO2/FIO2 responders (29/36 PP sessions, 77%) were identified 9.5 h after turning prone (14% slow responders), while most PaCO2 responders (15/36 PP sessions, 42%) were identified 13 h after turning prone. A subgroup of patients (interval intubation to PP ≥3 days) showed less PaO2/FIO2 responders (16% vs. 77%). An increase in PaCO2 and minute ventilation in the PP showed a significant negative correlation (p < 0.001). LC (median before the PP = 38 mL/cm H2O; two patients with LC >80 mL/cm H2O) showed a significant positive correlation with the 28 day survival of patients (p = 0.01). Conclusion: The PP significantly improves oxygenation in COVID-19 ARDS patients. The data suggest that they also benefit most from an early PP. A decrease in minute ventilation may result in fewer PaCO2 responders. LC may be a predictive outcome parameter in COVID-19 patients. Trial registration: Retrospectively registered.

The association of acute hypercarbia and plasma potassium concentration during laparoscopic surgery: a retrospective observational study

BackgroundIt is uncertain whether increases in PaCO2 during surgery lead to an increase in plasma potassium concentration and, if so, by how much. Hyperkalaemia may result in cardiac arrhythmias, muscle weakness or paralysis. The key objectives were to determine whether increases in PaCO2 during laparoscopic surgery induce increases in plasma potassium concentrations and, if so, to determine the magnitude of such changes.MethodsA retrospective observational study of adult patients undergoing laparoscopic abdominal surgery was perfomed. The independent association between increases in PaCO2 and changes in plasma potassium concentration was assessed by performing arterial blood gases within 15 min of induction of anaesthesia and within 15 min of completion of surgery.Results289 patients were studied (mean age of 63.2 years; 176 [60.9%] male, and mean body mass index of 29.3 kg/m2). At the completion of the surgery, PaCO2 had increased by 5.18 mmHg (95% CI 4.27 mmHg to 6.09 mmHg) compared to baseline values (P < 0.001) with an associated increase in potassium concentration of 0.25 mmol/L (95% CI 0.20 mmol/L to 0.31 mmol/L, P < 0.001). On multiple regression analysis, PaCO2 changes significantly predicted immediate changes in plasma potassium concentration and could account for 33.1% of the variance (r2 = 0.331, f(3,259) = 38.915, P < 0.001). For each 10 mmHg increment of PaCO2 the plasma potassium concentration increased by 0.18 mmol/L.ConclusionIn patients receiving laparoscopic abdominal surgery, there is an increase in PaCO2 at the end of surgery, which is independently associated with an increase in plasma potassium concentration. However, this effect is small and is mostly influenced by intravenous fluid therapy (Plasma-Lyte 148 solution) and the presence of diabetes.Trial registration Retrospectively registered in the Australian New Zealand Clinical Trials Registry (Trial Number: ACTRN12619000716167).

Exploring the limits of prolonged apnoea with high-flow nasal oxygen: an observational study.

High-flow nasal oxygen is increasingly used for oxygenation during apnoea. Extending apnoea duration using this technique has mainly been investigated during minor laryngeal surgery, but it is unclear how long it can be administered for before it should be discontinued due to acidosis. We aimed to describe the dynamics of arterial blood gases during apnoeic oxygenation with high-flow nasal oxygen with jaw thrust only, to explore the limits of this technique. We included adult orthopaedic patients scheduled for general anaesthesia. After pre-oxygenation, anaesthesia with neuromuscular blockade was induced and high-flow nasal oxygen (70l.min-1 ) was continued with jaw thrust as the only means of airway management, with monitoring of vital signs and arterial blood gas sampling every 5minutes. Apnoeic oxygenation with high-flow nasal oxygen was discontinued when arterial carbon dioxide tension (PaCO2 ) exceeded 12kPa or pH fell to 7.15.This technique was used in 35 patients and median (IQR [range]) apnoea time was 25 (20-30 [20-45]) min and was discontinued in all patients when pH fell to 7.15. The mean (SD) PaCO2 increase was 0.25 (0.06) kPa.min-1 but it varied substantially (range 0.13-0.35kPa.min-1 ). Mean (SD) arterial oxygen tension was 48.6 (11.8) kPa when high-flow nasal oxygen was stopped. Patients with apnoea time >25minutes were significantly older (p=0.025).We conclude that apnoeic oxygenation with high-flow nasal oxygen resulted in a significant respiratory acidosis that varies substantially on the individual level, but oxygenation was maintained.

Arterial blood gases and ventilation at rest by age and sex in an adult Andean population resident at high altitude.

Arterial blood gases (ABG) are influenced by the altitude above sea level, age and sex. Most studies have been conducted at sea level and in small populations ascending to or residents at very high altitudes. Our objective was to evaluate the ventilation and ABG by age and sex in an Andean population resident at high altitude (2640m). Analytical cross-sectional study was done in healthy volunteers. ABG and minute ventilation (VE) were measured. T test and ANOVA for differences by sex and age, and Pearson test for correlations between age, VE and ABG were performed. We included 374 adults, 55% women from 18 to 83years and hemoglobin of 15.7 ± 1.6g/dl. There was a significant decrease in PaO2 and SaO2 and an increase in P(A-a)O2 with age (p < 0.001). Unlike men, with age women had a significant increase in PaCO2 and a higher decrease in PaO2. The correlations between age, the decrease in PaO2 and the increase in PaCO2 were greater in women than in men. The VE adjusted to body surface area decreased with age, but this correlation was significantly higher in women. In this study, with a considerable number of healthy adults living at high altitude (2640m), we established the physiological impact of altitude, aging and gender in ABG. The PaO2 and PaCO2 were significantly lower and the hemoglobin values slightly higher than described at sea level. In addition to PaO2 decline with age, there was an age-related increase in PaCO2 in women, associated with a greater reduction of VE.

Interventionist videothermometry: a new model of cardiac ischemia evaluation

BackgroundThe purpose of the present study was to evaluate, through videothermometry, the temperature variation in the hearts of rabbits, that underwent induced myocardial ischemia and reperfusion.ResultsA total of 20 female rabbits were divided into two groups: a treated group and a sham group, the treatment group underwent 5 min of cardiac arrest and reperfusion, using the inflow occlusion technique. Throughout the experiment, the animals were monitored by videothermometry, observing the thermal variations of the myocardial tissue. During the experiment, at different times, blood gas tests and tests to evaluate the lactate concentrations were performed. At the end of the experiment, each heart was submitted to histopathological evaluation. In the treated group, there was a reduction in temperature of the myocardial tissue during the circulatory arrest compared to the sham group. Additionally, a colder area next to the caudal vena cava ostium and the right atrium was observed. Notably, despite the 5 min of cardiac arrest in the treated group, both the lactate and bicarbonate levels were maintained without significant variation. However, there was an increase in PaCO2 and pH reduction, featuring respiratory acidosis. In relation to the histopathological study, the presence of hydropic degeneration in the myocardium of animals in the treated group was observed.ConclusionsBased on these results, the videothermometry was efficient in identifying the range of myocardial tissue temperature, suggesting that the first areas to suffer due to cardiac arrest were the caudal vena cava ostium and the right atrium. However, in regard to the angiographic coronary thermography, the study was not feasible due to the small size of the coronary. There was no variation between the groups regarding the presence of myocardial infarction, myocardial congestion, myocardial edema and myocardial hemorrhage.

The severity of sleep hypoventilation in stable chronic obstructive pulmonary disease.

An increase in PaCO2 is the element that defines sleep hypoventilation (SH). We queried if patients with SH, and those with PaCO2 increases during sleep for shorter time periods than SH (shamSH) differed from the patients without SH (noSH) in other ways. This was a retrospective re-analysis of data from 100 stable inpatients with COPD with and without chronic hypercapnic respiratory failure. COPD was defined by criteria of the Global initiative for Chronic Obstructive Lung Disease (GOLD). For this study, SH was defined by an increase in PaCO2 ≥ 1.33 kPa to a value exceeding 6.7 kPa for ≥ 10 min (≥ 20 epochs of 30 s). Patients fulfilling the increase in PaCO2 for less than 10 min (1-19 epochs) were designated shamSH. All patients had daytime arterial blood gases, lung function tests, and polysomnography (PSG) with transcutaneous CO2 (PtcCO2). Of 100 patients, 25 had PtcCO2 increase ≥ 1.33 kPa. One never exceeded 6.7 kPa, 15 had SH, and 9 shamSH. SH and shamSH patients had extra CO2 load (= PtcCO2*time) both during and between the SH periods compared to the noSH group, the SH group more than the shamSH group. Using CO2 load as a measure of severity of sleep hypoventilation, SH patients have worse hypoventilation than the shamSH. Both shamSH and SH groups have extra CO2 load during and between SH periods, indicating that the SH/shamSH patients may represent a separate group of true hypoventilators during sleep.

The effect of 50% oxygen on PtCO2 in patients with stable COPD, bronchiectasis, and neuromuscular disease or kyphoscoliosis: randomised cross-over trials

BackgroundHigh-concentration oxygen therapy causes increased arterial partial pressure of carbon dioxide (PaCO2) in patients with COPD, asthma, pneumonia, obesity and acute lung injury. The objective of these studies was to investigate whether this physiological response to oxygen therapy occurs in stable patients with neuromuscular disease or kyphoscoliosis, and bronchiectasis.MethodsThree randomised cross-over trials recruited stable patients with neuromuscular disease or kyphoscoliosis (n = 20), bronchiectasis (n = 24), and COPD (n = 24). Participants were randomised to receive 50% oxygen and 21% oxygen (air), each for 30 min, in randomly assigned order. The primary outcome was transcutaneous partial pressure of carbon dioxide (PtCO2) at 30 min. The primary analysis was a mixed linear model.ResultsSixty six of the 68 participants had baseline PtCO2 values < 45 mmHg. The intervention baseline adjusted PtCO2 difference (95% CI) between oxygen and room air after 30 min was 0.2 mmHg (− 0.4 to 0.9), P = 0.40; 0.5 mmHg (− 0.2 to 1.2), P = 0.18; and 1.3 mmHg (0.7 to 1.8), P < 0.001, in the neuromuscular/kyphoscoliosis, bronchiectasis and COPD participants respectively.ConclusionsThe small increase in PtCO2 in the stable COPD patients with high-concentration oxygen therapy contrasts with the marked increases in PaCO2 seen in the setting of acute exacerbations of COPD. This suggests that the model of studying the effects of high-concentration oxygen therapy in patients with stable respiratory disease is not generalisable to the use of oxygen therapy in the acute clinical setting. Appropriate studies of high-concentration compared to titrated oxygen in acute clinical settings are needed to determine if there is a risk of oxygen-induced hypercapnia in patients with neuromuscular disease, kyphoscoliosis or bronchiectasis.Trial registrationAustralian New Zealand Clinical Trials Registry ACTRN12615000970549 Registered 16/9/15, ACTRN12615000971538 Registered 16/9/15 and ACTRN12615001056583 Registered 7/10/15.

Conscious Sedation with Local Anesthesia versus General Anesthesia for Patients Undergoing Transcatheter Aortic Valve Implantation

Abstract Background Transcatheter Aortic Valve Implantation (TAVI) procedure is being performed under general anesthesia (GA), conscious sedation associated with local anesthesia (CSLA) and local anesthesia alone. There have been limited studies to determine which plan of anesthesia is associated with better results. Aim We aimed in this study to assess the role of CSLA in outcome, complications, mortality and to assess quality of life in immediate post-procedural period (ICU and hospital stay). Methodology After approval of ethical committee, seventy cases of moderate to severe aortic stenosis planned for TAVI were randomized into two groups. Group-GA: received general anesthesia and Group-CSLA: received conscious sedation combined with local anesthesia. We measured intraoperative hemodynamic changes, pH, PaO2, PaCO2, need for inotropic support and need for blood products. Post-operative variables were need for inotropic support, prolonged respiratory support, need for renal dialysis, and incidence of stroke, heart block, aortic regurge as well as mortality. Results The CSLA group showed more incidence of respiratory acidosis with increase in PaCO2 (p=0.024), less decrease in mean arterial blood pressure (p=0.028), less need for inotropic support both intraoperative (p=0.001) and post-operative (p=0.005). The CSLA patients showed less hospital length of stay (LOS) (p=0.006) and less prolonged respiratory support more than 24h (p=0.001) compared to the GA group patients. However, there was no significant difference between the two groups as regards need for blood products (p=0.587) and incidence of complications in the form of renal failure (p=0.113), heart block (p=0.756), aortic regurge (paravalvular leak) (p=0.168) and mortality (p=0.238). There was no incidence of stroke in either group. Conclusion CSLA for TAVI patients in the current study showed better intraoperative hemodynamic stability, less need for inotropic support whether intaoperative or postoperative and less hospital LOS despite the presence of mild acceptable respiratory acidosis. So we can recommend to consider CSLA in such patients.

Tolerability and Safety of High-Flow Nasal Therapy in Patients Hospitalized with an Exacerbation of COPD.

The effect of high-flow nasal therapy (HFNT) in individuals with an exacerbation of chronic obstructive pulmonary disease (COPD) and hypercapnia is not well studied. We assessed patient tolerance and impact of air-gas therapy delivered by humidified HFNT (20-35 L/min) on gas exchange in hypercapnic COPD patients during hospitalization for COPD exacerbation. We hypothesized that HFNT use would be safe and well tolerated in individuals hospitalized for COPD exacerbation regardless of the degree of hypercapnia. Patients hospitalized for a COPD exacerbation were included if they were hypercapnic (arterial partial pressure of carbon dioxide [PaCO2] > 45 mmHg), ≥ 10 pack-year history, and agreed to treatment with HFNT, along with daily arterial blood gas (ABG) samples and bedside spirometry. They were placed on a HFNT system following admission for at least 3 days with an air-gas blend to maintain a flow rate between 20-35 L/min and fraction of inspired oxygen (FiO2) titrated to keep oxygen saturation (SaO2) values > 90%. Patient tolerance of HFNT and evidence of clinical deterioration as defined by worsening hypoxia or hypercapnia was the primary endpoint. Ten consecutive patients participated in the study. The patients had frequent prior exacerbations, were hypercapnic, dyspneic, and gas trapped. Participants received an air-gas flow rate (median [interquartile range (IQR)] 25 (IQR 20-30) L/min and FiO2 of 30 (IQR 30-30) %. There was no increase in PaCO2- levels (p = 0.26) or dyspnea (Borg scale, p= 0.52) while using HFNT. No patient discontinued HFNT, had further decompensation, required non-invasive ventilation or intubation during the study period. In a pilot study, patients experiencing a severe COPD exacerbation were able to tolerate continuous HFNT safely regardless of degree of hypercapnia.

Noninvasive tri-level positive airway pressure ventilation: is it a new challenging mode in management of patients with chronic obstructive pulmonary disease?

Background Chronic obstructive pulmonary disease (COPD) is a serious issue of sickness and rise in global fatality rates. Noninvasive positive pressure ventilation is the first-line therapy in patients with COPD with respiratory fialure (RF). Tri-level positive airway pressure (Tri-PAP) is new challenging mode of noninvasive ventilation (NIV). Objectives To compare between two modes of noninvasive positive pressure ventilation [bi-level positive airway pressure (Bi-PAP) and Tri-PAP] and to spell out outcomes, complication, and predictors of favorable outcome of NIV in patients with COPD with respiratory failure. Patients and methods This prospective comparative study was accomplished on 30 patients with COPD with respiratory failure, who were subjected to NIV (Bi-PAP or Tri-PAP) and standard conventional therapy. Arterial-blood gases (ABGs) (initially, 6 h, and finally) were analyzed. NIV outcomes, complications, and predictors of success were encountered. Results Patients were categorized according to managerial therapeutic NIV into Bi-PAP (n=15) or Tri-PAP (n=15) groups. Initial, 6-h, and final ABGs analyses (pH, PO2, PCO2, HCO3, and O2 sat) and NIV outcomes (successful or failed weaning) were analogous, without considerable variation between both Bi-PAP and Tri-PAP groups. pH showed crucial advancement after 6 h of initiation of Tri-PAP NIV. Terminal ABG interpretation (pH, PaCO2, PaO2, and O2 sat) had better outcomes than initial and 6-h ABG analyses of Tri-PAP NIV group. Irritations and ulcerations of nasal bridge, dry nose or mouth, nasal congestion, hypotension, and PaCO2 increase were the most hazardous events in both Bi-PAP and Tri-PAP NIV groups. Shorter duration of NIV, lower BMI, higher pH, and lower PCO2 (initially, 6 h, and final ABGs) as well as higher O2 saturation (in final ABG) were predictors of successful weaning in NIV (Bi-PAP and Tri-PAP) groups collectively. Conclusion Bi-PAP and Tri-PAP are appropriate mode of NIV in patients with COPD with RF with minimal complication and better outcomes. Tri-PAP had no superiority of utilization than Bi-PAP mode. pH and PCO2 are the powerful predictors of favorable NIV outcomes.

Evaluation of hyperoxia-induced hypercapnia in obese patients after cardiac surgery: a randomized crossover comparison of conservative and liberal oxygen administration.

Recent studies on patients with stable obesity-hypoventilation syndrome have raised concerns about hyperoxia-induced hypercapnia in this population. This study aimed to evaluate whether a higher oxygen saturation target would increase arterial partial pressure of carbon dioxide (PaCO2) in obese patients after coronary artery bypass grafting surgery (CABG). Obese patients having CABG were recruited. With a randomized crossover design, we compared two oxygenation strategies for 30 min each, immediately after extubation:aperipheral oxygen saturation (SpO2)target of ≥ 95% achieved with manual oxygen titration (liberal) and a SpO2target of 90% achieved with FreeO2, an automated oxygen titration device (conservative). The main outcome was end-of-periodarterial PaCO2. Thirty patients were included. Mean (standard deviation [SD]) body mass index (BMI) was 34 (3) kg·m-2 and mean (SD) baseline partial pressure of carbon dioxide (PCO2) was 40.7 (3.1) mmHg. Mean (SD) end-of-period PaCO2 was 42.0 (5.4) mmHg in the conservative period, compared with 42.6 (4.6) mmHg in the liberal period [mean difference - 0.6 (95% confidence interval - 2.2 to 0.9) mmHg; P = 0.4]. Adjusted analysis for age, BMI, narcotics, and preoperative PaCO2 did not substantively change the results. Fourteen patients were retainers, showing an elevation in mean (SD) PaCO2 in the liberal period of 3.3 (4.1) mmHg. Eleven patients had the opposite response, with a mean (SD) end-of-period PaCO2 decrease of 1.8 (2.2) mmHg in the liberal period. Five patients had a neutral response. This study did not show a clinically important increase in PaCO2 associated with higher SpO2 values in this specific population of obese patients after CABG. Partial pressure of carbon dioxide increased with liberal oxygen administration in almost half of the patients, but no predictive factor was identified. www.clinicaltrials.gov (NCT02917668); registered 25 September, 2016.