Variation in the PaO<Subscript>2</Subscript>/FiO<Subscript>2</Subscript> ratio with FiO<Subscript>2</Subscript>: mathematical and experimental description,and clinical relevance

Introduction  

Previous studies have shown through theoretical analyses that the ratio of the partial pressure of oxygen in arterial blood (PaO₂) to the inspired oxygen fraction (FiO₂) varies with the FiO₂ level. The aim of the present study was to evaluate the relevance of this variation both theoretically and experimentally using mathematical model simulations, comparing these ratio simulations with PaO₂/FiO₂ ratios measured in a range of different patients.     

Arterial line for monitoring SpO<Subscript>2</Subscript> in patients with ischemic peripheries

Monitoring the oxygenation status of patients with poor peripheral perfusion or ischemic peripheries is challenging in view of unreliable or unrecordable pulse oximeter data. In this article we describe a very simple and innovative technique of using the arterial line for reliable recording of arterial oxygen saturation (SpO₂) in such patients. We conclude that the arterial line can be used as an extension of the artery and SpO₂ may be reliably measured using the arterial line in such patients as long as the blood in the arterial tubing is pulsatile and a good contact is ensured between the arterial tubing and the sensor of the pulse oximeter.     

Ongoing NovoSeven<Subscript>®</Subscript> trials

Recombinant activated factor VII (rFVIIa, ‘NovoSeven_®’) was initially developed for the treatment of bleeding in patients with haemophilia and inhibitors, and is currently licensed in most countries worldwide. The mechanism of action suggests that its enhancing effects in haemostasis are limited to the site of injury and that systemic activation of the coagulation cascade does not occur. These properties, together with anecdotal reports of its beneficial effects in different patient populations with severe bleeds, suggest that rFVIIa may be valuable as a general haemostatic agent. In case reports, rFVIIa has been reported to reduce bleeding in patients with liver disease, thrombocytopenia or thrombocytopathia, trauma those undergoing radical prostatectomy or receiving oral anticoagulant therapy. A number of clinical trials have recently been initiated to collect data on the safety and efficacy of rFVIIa in these patient groups. The beneficial effects of rFVIIa occurring in these studies will support the potential use of rFVIIa as a universal haemostatic agent.     

Changes in FiO<Subscript>2</Subscript> affect PaO<Subscript>2</Subscript> with minor alterations in cerebral concentration of oxygenated hemoglobin during liquid ventilation in healthy piglets

Objective To measure the impact of changes in the fraction of inspired oxygen (FiO₂) on systemic and cerebral oxygen supply in gas and liquid ventilated healthy animals.Design Interventional prospective animal study.Setting University research laboratory.Participants Ten healthy, new-born piglets.Interventions Variations in FiO₂ during conventional mechanical ventilation (CMV) followed by partial liquid ventilation (PLV) with two different filling volumes of PF 5080 (10 vs. 30 ml/kg).Measurements and results Arterial blood gases were obtained 15 min after changing FiO₂ and concentrations of cerebral oxygenated and total hemoglobin were determined with near infrared spectroscopy. During CMV an increase in FiO₂ 1.0 was associated with a constant rise in PaO₂ but only a small increase in the cerebral concentration of oxygenated Hb. Initiation of PLV (at FiO₂ of 1.0) caused a rapid drop in PaO₂ towards values that were similar to CMV at FiO₂ of 0.5. At FiO₂ of 0.5 a reduction in oxygenated Hb was found in the 30 ml/kg filling group. Complete filling of the lungs with PFC caused a significant drop in total cerebral Hb concentration.Conclusions According to our data, PLV in healthy lungs should be performed with a FiO₂ of 1.0 and a small filling volume to avoid deterioration in cerebral oxygen supply.Financial support: The study was supported by a grant of German Ministry of Education and Research (BMBF Perinatale Lunge-01ZZ9511). NIRO 300 was kindly supplied by Hamamatsu Germany.     

NREM sleep staging using WAV<Subscript>CNS</Subscript> index

Objective  

Visual scoring of 30-s epochs of sleep data is not always adequate to show the dynamic structure of sleep in sufficient details. It is also prone to considerable inter- and intra-rater variability. Moreover, it involves considerable training and experience, and is very tedious, time-consuming, labor-intensive and costly. Hence, automatic sleep staging is needed to overcome these limitations. Since naturally occurring NREM sleep and anesthesia have been reported to possess various underlying neurophysiological similarities, EEG-based depth-of-anesthesia monitors have started to penetrate into sleep research. This study investigates the ability of WAV_CNS index (as implemented in NeuroSENSE depth-of-anesthesia monitor) to detect NREM sleep stages and wake state for full overnight PSG data.     

Efficacy benefit of an NK<Subscript>1</Subscript> receptor antagonist (NK<Subscript>1</Subscript>RA) in patients receiving carboplatin: supportive evidence with NEPA (a fixed combination of the NK<Subscript>1</Subscript> RA,netupitant, and palonosetron) and aprepitant regimens

Purpose

Antiemetic guideline recommendations are inconsistent as to whether a neurokinin-1 receptor antagonist (NK₁ RA) should be administered with a 5-hydroxytryptamine-3 (5HT₃) RA + dexamethasone (DEX) in patients receiving carboplatin. Patients receiving cisplatin routinely receive an NK₁ RA-containing regimen with a resulting 14–22 % benefit in no emesis rates over a 5-HT₃ RA/DEX control. Recent studies suggest a similar benefit in patients receiving carboplatin. NEPA is the first fixed antiemetic combination agent and comprises the highly selective NK₁ RA, netupitant, and pharmacologically distinct 5-HT₃ RA, palonosetron (PALO). This paper presents the efficacy of NEPA in the subset of patients receiving carboplatin in a phase 3 trial (NCT01376297), in the context of aprepitant (APR) data in the carboplatin setting.

Methods

One hundred ninety-six patients (47 % of all study patients: n = 145 NEPA + DEX; n = 51 APR + PALO + DEX) received carboplatin in a multinational, double-blind, randomized phase 3 study. Complete response (CR: no emesis/rescue) and no significant nausea (NSN: score ≤25 on 100 mm visual analog scale) rates were calculated.

Results

Cycle 1–4 overall (0–120 h) CR rates were similar for NEPA (80, 91, 92, and 93 %) and APR (82, 88, 88, and 90 %). Overall NSN rates were also similar (NEPA 84–96 %; APR 82–90 %).

Conclusions

Response rates for NEPA and APR regimens were similar and consistent with prior studies evaluating the contribution of adding NK₁ RAs in patients receiving carboplatin. Considering such evidence, guideline groups/practitioners should consider giving a NK₁ RA antiemetic triplet in patients receiving carboplatin.

     

Clinical Validation of a Digital Transcutaneous PCO<Subscript>2</Subscript>/SpO<Subscript>2</Subscript> Ear Sensor in Adult Patients after Cardiac Surgery

Objective The aim of this study was to validate the V-Sign digital sensor (SenTec AG, Therweil, Switzerland) for combined noninvasive assessment of pulse oxymetric oxygen saturation (SpO₂) and transcutaneous carbon dioxide tension (PtcCO₂) in adults after cardiac surgery. Methods In twenty one patients, aged 51–86 years, simultaneous measurements of blood gases with the V-Sign Sensor and with two Nellcor Durasensors (model DS-100A), one at the opposite earlobe and one with a finger clip, were compared first during hyper-, normo- and hypocapnia and at different pulse rates using a pacemaker, and then at 2-h intervals up to 8 h. Agreement was assessed by Bland-Altman analysis. Results PtcCO₂ data of three patients were excluded because of calibration failure of the device. Median (range) PtcCO₂ for the remaining patients was 5.49 (3.3–7.6) kPa and arterial carbon dioxide tension (PaCO₂) was 5.43 (3.61–7.41) kPa. Corresponding mean bias was +0.05 kPa and limits of agreement (LOA) were −1.2/+1.3 kPa. During normo- and hypoventilation, mean bias was good at +0.02 and +0.04 kPa respectively, but limits of agreement were poor at −0.67/+0.69 and −0.81/+0.88 kPa. In 10 patients, an initial overshoot of PtcCO₂ was observed. Mean bias of SpO₂ and pulse rate was close to zero (−1.5% and +0.001 bpm respectively), but limits of agreement were unacceptably high (−21.4/+18.4% and −22.3/+22.3 bpm). Conclusions In the present state of development the SenTeC Digital monitor V-Sign device has serious limitations. Additional efforts are necessary to eliminate calibration failures and the initial overshoot of PtcCO₂ as well as to improve detection of SpO₂ and pulse rate. Baulig W, Schütt P, Roth HR, Hayoz J, Schmid ER. Clinical validation of a digital transcutaneous PCO₂/SpO₂ ear sensor in adult patients after cardiac surgery.     

Coenzyme Q<Subscript>10</Subscript> deficiency in septic shock patients

Donnino and colleagues provide new insights into the field of oxidative stress and mitochondrial dysfunction during septic shock. These authors suggest a coenzyme Q₁₀ (CoQ₁₀) deficiency in patients with septic shock. Larger prospective observational trials measuring CoQ₁₀ in patients with septic shock are required to confirm the possibility of CoQ₁₀ depletion. This study is a new step toward a study testing CoQ₁₀ as a potential therapeutic agent for patients with septic shock.     

ECMO,ECCO<Subscript>2</Subscript>R: From origins to date

This article reviews the history of extracorporeal membrane oxygenation (ECMO) from the first successful case reported at the beginning of the seventies till the recent extensive ECMO use in the intensive care unit to treat acute respiratory distress syndrome, especially following the 2011 H1N1 flu epidemics. ECMO development was contemporary with the improvements in ARDS ventilation and the development of various complementary techniques including extracorporeal CO₂ removal (ECCO₂R). However, despite the evidence already obtained, the definitive benefit and indications of ECMO to treat ARDS remain to be established. The history is still continuing.     

The prognostic value of muscle StO<Subscript>2</Subscript> in septic patients

Objective: To quantify sepsis-induced alterations in changes in muscle tissue oxygenation (StO₂) after an ischemic challenge using near-infrared spectroscopy (NIRS), and to test the hypothesis that these alterations are related to outcome. Design Prospective study. Setting Thirty-one-bed, university hospital Department of Intensive Care. Patients Seventy-two patients with severe sepsis or septic shock, 18 hemodynamically stable, acutely ill patients without infection, and 18 healthy volunteers. Interventions Three-minute occlusion of the brachial artery using a cuff inflated 50 mmHg above systolic arterial pressure. Measurements and main results Thenar eminence StO₂ was measured continuously by NIRS before (StO₂baseline), during, and after the 3-min occlusion. Changes in StO₂ were assessed by the slope of increase in StO₂ during the first 14 s following the ischemic period and by the difference between the maximum StO₂ and StO₂baseline (Δ). The slope was lower in septic patients than in controls and volunteers [2.3 (1.3–3.6), 4.8 (3.5–6.0), and 4.7 (3.2–6.3) %/s, p < 0.001]. Δ was also significantly lower in septic patients than in the other groups. Slopes were lower in septic patients with than without shock [2.0 (1.2–2.9) vs 3.2 (1.8–4.5) %/s, p < 0.05]. In 52 septic patients, in whom the slope was obtained every 24 h for 48 h, slopes were higher in survivors than in non-survivors and tended to increase in survivors but not in non-survivors. Conclusions Altered recovery in StO₂ after an ischemic challenge is frequent in septic patients and more pronounced in the presence of shock. The presence and persistence of these alterations in the first 24 h of sepsis are associated with worse outcome. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The initial slope of the VCO<Subscript>2</Subscript>/VO<Subscript>2</Subscript>-curve (s1) in cardiopulmonary exercise testing is a strong and independent predictor of outcome in patients with previous myocardial infarction

Background  Detecting heart failure (HF) patients at risk is a relevant clinical problem. Our goal was to define associations of clinical HF-markers and exercise parameters with respect to their prognostic power in HF-patients. Methods  We performed cardiopulmonary exercise testing (CPET) in 103 ischemic HF-patients. CPET-parameters included peak VO₂, VO₂ at AT, peak oxygen pulse, minimal CO₂ and O₂ equivalents, VE/VCO₂ and s1, a motivation-independent and submaximal parameter representing the initial slope of the VCO₂/VO₂-curve that has not been described in HF-patients so far. Results  Median follow-up was 668 days. The combined endpoint of cardiovascular death and rehospitalization due to HF occurred in 14 patients. Patients with/without events differed significantly regarding their age, NYHA-class, LVEF and NT-proBNP serum-levels. Patients with events had significantly lower peak VO₂- and higher s1-values. NT-proBNP serum-levels, NYHA-class and LVEF were significantly correlated with peak VO₂. Only age, peak VO₂ and s1 were independent predictors of adverse events. Using multivariate analysis, s1 was a strong and independent parameter with good sensitivity and specificity. Conclusion  s1 is an independent and powerful predictor in HF-patients. Since s1 is independent of maximal exercise capacity, s1 might be more accurate for the evaluation of HF-patients not willing or unable to perform maximal exercise.