Low Pneumoperitoneum Pressure Reduces Gas Embolism During Laparoscopic Liver Resection: A Randomized Controlled Trial.

OBJECTIVE: To compare the effect of low and standard pneumoperitoneal pressure (PP) on the occurrence of gas embolism during laparoscopic liver resection (LLR). BACKGROUND: LLR has an increased risk of gas embolism. Although animal studies have shown that low PP reduces the occurrence of gas embolism, clinical evidence is lacking. METHODS: This parallel, dual-arm, double-blind, randomized controlled trial included 141 patients undergoing elective LLR. Patients were randomized into standard ("S," 15 mm Hg; n = 70) or low ("L," 10 mm Hg; n = 71) PP groups. Severe gas embolism (≥ grade 3, based on the Schmandra microbubble method) was detected using transesophageal echocardiography and recorded as the primary outcome. Intraoperative vital signs and postoperative recovery profiles were also evaluated. RESULTS: Fewer severe gas embolism cases (n = 29, 40.8% vs n = 47, 67.1%, P = 0.003), fewer abrupt decreases in end-tidal carbon dioxide partial pressure, shorter severe gas embolism duration, less peripheral oxygen saturation reduction, and fewer increases in heart rate and lactate during gas embolization episodes was found in group L than in group S. Moreover, a higher arterial partial pressure of oxygen and peripheral oxygen saturation were observed, and fewer fluids and vasoactive drugs were administered in group L than in group S. In both groups, the distensibility index of the inferior vena cava negatively correlated with central venous pressure throughout LLR, and a comparable quality of recovery was observed. CONCLUSIONS: Low PP reduced the incidence and duration of severe gas embolism and achieved steadier hemodynamics and vital signs during LLR. Therefore, a low PP strategy can be considered a valuable choice for the future LLR.

Cardiac Tamponade Caused By Carbon Dioxide Insufflation During Robot-Assisted Thoracic Surgery: A Case Report.

Various complications can occur during robot-assisted thoracic surgery for mediastinal tumors owing to carbon dioxide (CO2) insufflation. This study reports the case of a 43-year-old woman who underwent robot-assisted surgery for an anterior mediastinal tumor with the subxiphoid approach. Shortly after starting CO2 insufflation, the blood pressure decreased significantly. Subsequent examination of the mediastinum revealed a left-sided pericardial injury. Cardiac tamponade due to entry of CO2 gas into the pericardial cavity was suspected. A deliberate incision was made in the right pericardium, ultimately resolving the cardiac tamponade and substantially improving the patient's blood pressure.

Intraperitoneal insufflation of carbon dioxide rescues intestinal damage in an experimental murine model of colitis.

OBJECTIVES: Necrotizing enterocolitis (NEC) is a severe neonatal surgical condition, associated with a prolonged pro-inflammatory state, leading to high mortality and morbidity rates. Carbon dioxide (CO2 ) insufflation during laparoscopy may have an anti-inflammatory effect. We aimed to evaluate the effects of CO2 -insufflation on experimental colitis. METHODS: Acute colitis was induced in 6-week-old Balb/c mice by the administration of 2%-dextran sulfate-sodium (DSS) during 7 days (n = 45). On Day 4, two groups received intraperitoneal insufflation (duration: 30 mn, pressure: 5 mmHg) of CO2 ("DSS+CO2 ") or air ("DSS+air"). A group received no insufflation ("DSS"). Groups were compared for clinical severity using the disease activity index (DAI-body weight loss, stool consistency, and bleeding), histological severity (histopathological activity index, colon length, and ulcerations), colonic mucosecretion, and inflammation. RESULTS: DAI was significantly decreased in DSS+CO2 group, compared to DSS (p < 0.0001) or DSS+air (p < 0.0001) groups. Colon length was increased in DSS+CO2 treated mice compared to DSS (p = 0.0002). The histopathological activity index was lower in DSS+CO2 (vs. DSS, p = 0.0059/vs. DSS+air, p = 0.0389), with decreased ulcerations (3.77 vs. 10.7, p = 0.0306), and persistent mucosecretion with increased mucin-secreting cells. CONCLUSIONS: CO2 -insufflation attenuates DSS-induced colitis and improves both clinical and histological scores. Laparoscopy with CO2 insufflation represents a therapeutic anti-inflammatory strategy for NEC.

Effects of Butorphanol on Respiration in White Rhinoceros (Ceratotherium simum) Immobilized with Etorphine-Azaperone.

This article reports on respiratory function in white rhinoceros (Ceratotherium simum) immobilized with etorphine-azaperone and the changes induced by butorphanol administration as part of a multifaceted crossover study that also investigated the effects of etorphine or etorphine-butorphanol treatments. Six male white rhinoceros underwent two immobilizations by using 1) etorphine-azaperone and 2) etorphine-azaperone-butorphanol. Starting 10 min after recumbency, arterial blood gases, limb muscle tremors, expired minute ventilation, and respiratory rate were evaluated at 5-min intervals for 25 min. Alveolar to arterial oxygen gradient, expected respiratory minute volume, oxygen consumption, and carbon dioxide production were calculated. Etorphine-azaperone administration resulted in hypoxemia and hypercapnia, with increases in alveolar to arterial oxygen gradient, oxygen consumption, and carbon dioxide production, and a decrease in expired minute ventilation. Muscle tremors were also observed. Intravenous butorphanol administration in etorphine-azaperone-immobilized white rhinoceros resulted in less hypoxemia and hypercapnia; a decrease in oxygen consumption, carbon dioxide production, and expired minute ventilation; and no change in the alveolar to arterial oxygen gradient and rate of breathing. We show that the immobilization of white rhinoceros with etorphine-azaperone results in hypoxemia and hypercapnia and that the subsequent intravenous administration of butorphanol improves both arterial blood oxygen and carbon dioxide partial pressures.

Within- and transgenerational stress legacy effects of ocean acidification on red abalone (Haliotis rufescens) growth and survival.

Understanding the mechanisms by which individual organisms respond and populations adapt to global climate change is a critical challenge. The role of plasticity and acclimation, within and across generations, may be essential given the pace of change. We investigated plasticity across generations and life stages in response to ocean acidification (OA), which poses a growing threat to both wild populations and the sustainable aquaculture of shellfish. Most studies of OA on shellfish focus on acute effects, and less is known regarding the longer term carryover effects that may manifest within or across generations. We assessed these longer term effects in red abalone (Haliotis rufescens) using a multi-generational split-brood experiment. We spawned adults raised in ambient conditions to create offspring that we then exposed to high pCO2 (1180 µatm; simulating OA) or low pCO2 (450 µatm; control or ambient conditions) during the first 3 months of life. We then allowed these animals to reach maturity in ambient common garden conditions for 4 years before returning the adults into high or low pCO2 treatments for 11 months and measuring growth and reproductive potential. Early-life exposure to OA in the F1 generation decreased adult growth rate even after 5 years especially when abalone were re-exposed to OA as adults. Adult but not early-life exposure to OA negatively impacted fecundity. We then exposed the F2 offspring to high or low pCO2 treatments for the first 3 months of life in a fully factorial, split-brood design. We found negative transgenerational effects of parental OA exposure on survival and growth of F2 offspring, in addition to significant direct effects of OA on F2 survival. These results show that the negative impacts of OA can last within and across generations, but that buffering against OA conditions at critical life-history windows can mitigate these effects.

Safety, Effectiveness and Pitfalls of Carbon Dioxide Routine Use as a Contrast Agent for Endovascular Abdominal Aortic Repair.

BACKGROUND: Despite the evidence of good performance, carbon dioxide (CO2) routine employment as a contrast agent for endovascular procedures is far from being adopted with its use currently limited to patients with renal impairment and known allergy to iodinated contrast medium (ICM). The purpose of our study is to evaluate the safety and effectiveness of CO2 guided endovascular abdominal aortic aneurysm repair (EVAR) in a standard population and to assess the rationale for a future widespread use. METHODS: We retrospectively collected data of every patient who underwent CO2 guided standard EVAR from September 2020 to May 2021 and compared them with the data of every patient who underwent EVAR using ICM from December 2019 to August 2020 in our unit. The selection of the contrast medium was not based on any preoperative factor as the contrast medium was routinely used in every patient in both periods. The primary end point of the study was the technical success rate. Secondary end points were the early and late complication rates, radiation exposure and renal function impairment. RESULTS: 49 patients underwent ICM guided EVAR and 52 patients underwent CO2 guided EVAR in our unit in the time frames specified above. The technical success rate was 100% in both groups with no accidental coverage of any target vessel. Intraoperative endoleaks were observed in 14% of ICM patients and 25% of CO2 patients. The radiation exposure was higher in the CO2 group if compared to the ICM group (311.48 vs. 159.86 median mGy/cm2 - P < 0.001). The incidence of postoperative acute kidney injury was low and similar in the 2 groups. No significant worsening over time of the renal function has been reported in both groups. CONCLUSIONS: EVAR can be safely performed under CO2 guidance without the integration of any quantity of ICM but with an increase in radiation exposure. The nephroprotective role of CO2 guided EVAR in a standard population is unclear and the same role in renal impaired patients should be validated with further studies on selected populations.

A Novel Isobaric (Gas-Less) Laparoscopic Surgery Device.

BACKGROUND: Laparoscopic Surgery is performed using carbon dioxide gas insufflated into the abdominal cavity to create a space for endoscopic visualization. During a laparoscopic surgical dissection plume is formed from electrocautery dissection. This plume contains viruses and sometimes COVID-19 viruses. The plume obscures the visual field. The unfiltered plume release is dangerous to surgeons, nurses, and patients. The loss of visualization during carbon dioxide release delays surgery. The use of carbon dioxide insufflated gas can have side effects such as C02 embolus, pain from diaphragmatic stretching, physiological complications such as respiratory infections and renal problems. The release of carbon dioxide gas into the atmosphere, unfiltered is significant. This accounts for 7% of greenhouse gases globally. This percentage is rising due to expansion of minimally invasive surgery. METHODOLOGY: The proposed system for gasless surgery was designed by algorithms of tensegrity and geodesic dome pressures. EXPERIMENT RESULTS: 100 simulator studies were performed to develop the device to elevate the abdominal wall to create a gas free (isobaric) space for Laparoscopic Surgery. After design freeze, 4 animal studies were performed using ethical research guidelines at Amsterdam Medical Centre Research Department, Netherlands. 3 cadaveric studies were performed using Ethical guidelines at Hackensack University Medical Centre, New Jersey, USA, to evaluate the device in a human setting. CONCLUSIONS: These devices for Laparoscopic Surgery, Robotic Surgery, and Hand Assisted Laparoscopic Surgery (HALS) successfully proved that a superior intra-abdominal space can be created without carbon dioxide insufflation. The devices are patented in USA and Europe.

Utility of Carbon Dioxide Venography and Intraprocedural CT for Adrenal Venous Sampling in Patients with an Allergy to Iodinated Contrast Media.

PURPOSE: To assess the diagnostic performance of carbon dioxide (CO2) and intraprocedural unenhanced computed tomography (CT) for adrenal venous sampling (AVS) (CO2-intraprocedural unenhanced CT-AVS) in patients with primary aldosteronism (PA) and a history of iodine contrast medium allergy. MATERIALS AND METHODS: CO2-intraprocedural unenhanced CT-AVS was performed in 18 patients with iodine contrast media allergies at the authors' hospital between December 2015 and January 2021. CT and noncontrast magnetic resonance angiography were used to evaluate the preoperative adrenal vein anatomy. CO2 venography was performed to confirm adrenal vein catheterization. Additionally, intraprocedural unenhanced CT was also performed to confirm catheter position in the right adrenal gland. RESULTS: In all cases in which CO2-intraprocedural unenhanced CT-AVS was performed, the right and left adrenal veins were catheterized appropriately, leading to a localized diagnosis. Catheterization of the left adrenal vein was confirmed using CO2 venography in all cases. In 7 of the 18 cases, CO2 venography demonstrated selection of the right adrenal vein. In 15 of 18 cases, intraprocedural unenhanced CT demonstrated selection of the right adrenal vein. CONCLUSIONS: CO2-intraprocedural unenhanced CT-AVS demonstrated the same diagnostic ability for PA localization as conventional AVS with iodine contrast media. The proposed method is clinically feasible for AVS, in which iodine contrast media use is restricted.

Carbon Dioxide Guided Endovascular Aortic Aneurysm Repair in Impaired Renal Function: Propensity Score Matched Study.

OBJECTIVE: Carbon dioxide (CO2) is the preferred contrast agent in patients with impaired renal function and or contrast allergy and, particularly, in patients who require large volumes of contrast for complex endovascular procedures. In this study, the aim was to clarify the possible protective effects of CO2 guided endovascular aneurysm repair (EVAR) for patients with impaired renal function by propensity score matching. METHODS: A retrospective analysis of the database was performed for 324 patients having EVAR between January 2019 and January 2022. A total of 34 patients treated with CO2 guided EVAR were evaluated. This cohort was matched for age, sex, pre-operative serum creatinine levels and glomerular filtration rate (GFR) levels and specific comorbidities to obtain homogeneous groups that included only patients with impaired renal function (eGFR < 60 mL/min/1.73m2). The primary endpoint was to compare the decrease in eGFR from baseline and development of contrast induced nephropathy (CIN) using propensity score matching. Secondary endpoints were the need for renal replacement therapy, other peri-procedural morbidity and mortality. RESULTS: Thirty-one patients (9.6%) of the total population developed CIN. There was no difference in the rate of CIN development between the standard EVAR group and the CO2 guided EVAR group in the unmatched population (10% vs. 3%, p = .15). After matching, the decrease in eGFR values after the procedure was more pronounced for the standard EVAR group (from 44 to 40 mL/min/1.73m2, interaction p = .034). Meanwhile, CIN development was more frequent for the standard EVAR group (24% vs. 3%, p = .027). In matched patients, early death did not differ between the groups (5.9% vs. 0, p = .15) CONCLUSION: Patients with impaired renal function are at higher risk of CIN after an endovascular procedure. CO2 guided EVAR is a safe, effective, and feasible treatment option, especially for patients with impaired renal function. CO2 guided EVAR may be a protective measure for contrast induced nephropathy.

Carbon dioxide angiography during peripheral vascular interventions is associated with decreased cardiac and renal complications in patients with chronic kidney disease.

OBJECTIVE: Patients with chronic kidney disease (CKD) who undergo peripheral vascular interventions (PVI) with iodinated contrast are at higher risk of post-contrast acute kidney injury (PC-AKI). Carbon dioxide (CO2) angiography can reduce iodinated contrast volume usage in this patient population, but its impact on PC-AKI has not been studied. We hypothesize that CO2 angiography is associated with a decrease in PC-AKI in patients with advanced CKD. METHODS: The Vascular Quality Initiative PVI dataset from 2010 to 2021 was reviewed. Only patients with advanced CKD (estimated glomular filtration rate <45 ml/min/1.73 m2) treated for peripheral arterial disease were included. Propensity matching and multivariate logistic regression based on demographics, comorbidities, CKD stage, and indications were used to compare the outcomes of patients treated with and without CO2. RESULTS: There were 20,706 PVIs performed in patients with advanced CKD, and only 22% utilized CO2 angiography. Compared with patients treated without CO2, patients who underwent CO2 angiography were younger and less likely to be women or White, and more likely to have poor renal function, diabetes, cardiac comorbidities, and present with tissue loss. Propensity matching yielded well-matched groups with 4472 patients in each group. The procedural details after matching demonstrated 50% reduction in the volume of contrast used (32±33 vs 65±48 mL; P < .01). PVI with CO2 angiography was associated with lower rates of PC-AKI (3.9% vs 4.8%; P = .03) and cardiac complications (2.1% vs 2.9%; P = .03) without a significant difference in technical failure or major/minor amputations. Low contrast volumes (≤50 mL for CKD3, ≤20 mL for CKD4, and ≤9 mL for CKD5) are associated with reduced risk of PC-AKI (hazard ratio, 0.59; P < .01). CONCLUSIONS: CO2 angiography reduces iodinated contrast volume usage during PVI and is associated with decreased cardiac complications and PC-AKI. CO2 angiography is underutilized and should be considered for patients with advanced CKD who require endovascular therapy.

Oral Oxycodone-Induced Respiratory Depression During Normocapnia and Hypercapnia: A Pharmacokinetic-Pharmacodynamic Modeling Study.

The widely prescribed opioid oxycodone may cause lethal respiratory depression. We compared the effects of oxycodone on breathing and antinociception in healthy young volunteers. After pharmacokinetic/pharmacodynamic (PK/PD) modeling, we constructed utility functions to combine the wanted and unwanted end points into a single function. We hypothesized that the function would be predominantly negative over the tested oxycodone concentration range. Twenty-four male and female volunteers received 20 (n = 12) or 40 (n = 12) mg oral oxycodone immediate-release tablets. Hypercapnic ventilatory responses (visit 1) or responses to 3 nociceptive assays (pain pressure, electrical, and thermal tests; visit 2) were measured at regular intervals for 7 hours. the PK/PD analyses, that included carbon dioxide kinetics, stood at the basis of the utility function: probability of antinociception minus probability of respiratory depression. Oxycodone had rapid onset/offset times (30-40 minutes) with potency values (effect-site concentration causing 50% of effect) ranging from 0.05 to 0.13 ng/mL for respiratory variables obtained at hypercapnia and antinociceptive responses. Ventilation at an extrapolated end-tidal carbon dioxide partial pressure of 55 mmHg, was used for creation of 3 utility functions, one for each of the nociceptive tests. Contrary to expectation, the utility functions were close to zero or positive over the clinical oxycodone concentration range. The similar or better likelihood for antinociception relative to respiratory depression may be related to oxycodone's receptor activation profile or to is high likeability that possibly alters the modulation of nociceptive input. Oxycodone differs from other µ-opioids, such as fentanyl, that have a consistent negative utility.

The optimal operative protocol to accomplish CO2-EVAR resulting from a prospective interventional multicenter study.

OBJECTIVES: Carbon dioxide (CO2) angiography for endovascular aortic repair (CO2-EVAR) is used to treat abdominal aortic aneurysms (AAAs), especially in patients with chronic kidney disease or allergy to iodinated contrast medium (ICM). However, some technical issues regarding the visualization of the lowest renal artery (LoRA) and the best quality image through angiographies performed from pigtail or introducer sheath are still unsolved. The aim of this study was to analyze different steps of CO2-EVAR to create an operative standardized protocol. METHODS: Patients undergoing CO2-EVAR were prospectively enrolled in five European centers from 2019 to 2021. CO2-EVAR was performed using an automated injector (pressure, 600 mmHg; volume, 100 cc); a small amount of ICM was injected in case of difficulty in LoRA visualization. LoRA visualization and image quality (1 = low, 2 = sufficient, 3 = good, 4 = excellent) were analyzed at different procedure steps: preoperative CO2 angiography from pigtail and femoral introducer sheath (first step), angiographies from pigtail at 0%, 50%, and 100% of proximal main body deployment (second step), contralateral hypogastric artery (CHA) visualization with CO2 injection from femoral introducer sheath (third step), and completion angiogram from pigtail and femoral introducer sheath (fourth step). Intraoperative and postoperative CO2-related adverse events were also evaluated. χ2 and Wilcoxon tests were used for statistical analysis. RESULTS: In the considered period, 65 patients undergoing CO2-EVAR were enrolled (55/65 [84.5%] male; median age, 75 years [interquartile range (IQR), 11.5 years]). The median ICM injected was 17 cc (IQR, 51 cc); 19 (29.2%) of 65 procedures were performed with 0 cc ICM. Fifty-five (84.2%) of 65 patients underwent general anesthesia. In the first step, median image quality was significantly higher with CO2 injected from femoral introducer (pigtail, 2 [IQR, 3] vs introducer, 3 [IQR, 3]; P = .008). In the second step, LoRA was more frequently detected at 50% (93% vs 73.2%; P = .002) and 100% (94.1% vs 78.4%; P = .01) of proximal main body deployment compared with first angiography from pigtail; similarly, image quality was significantly higher at 50% (3 [IQR, 3] vs 2 [IQR, 3]; P ≤ .001) and 100% (4 [IQR, 3] vs 2 [IQR, 3]; P = .001) of proximal main body deployment. CHA was detected in 93% cases (third step). The mean image quality was significantly higher when final angiogram (fourth step) was performed from introducer (pigtail, 2.6 ± 1.1 vs introducer, 3.1 ± 0.9; P ≤ .001). The intraoperative (7.7%) and postoperative (12.5%) adverse events (pain, vomiting, diarrhea) were all transient and clinically mild. CONCLUSIONS: Preimplant CO2 angiography should be performed from femoral introducer sheath. Gas flow impediment created by proximal main body deployment can improve image quality and LoRA visualization with CO2. CHA can be satisfactorily visualized with CO2 alone. Completion CO2 angiogram should be performed from femoral introducer sheath. This operative protocol allows performance of CO2-EVAR with 0 cc or minimal ICM, with a low rate of mild temporary complications.

Carbon Dioxide Angiography for the Detection of Lower Gastrointestinal Arterial Bleeding Initially Occult to Angiography with Iodinated Contrast Media.

This study evaluated the utility of carbon dioxide (CO2) in angiography for the detection of lower gastrointestinal arterial bleeding initially occult to angiography with iodinated contrast media. Fourteen patients underwent CO2-enhanced angiography. In all patients, extravasation was identified by contrast-enhanced computed tomography but not by initial iodinated contrast-enhanced angiography. After iodinated contrast-enhanced angiography, CO2-enhanced angiography was performed from the same catheter position. The detection capability for extravasation on CO2-enhanced angiography was evaluated. CO2-enhanced angiography allowed for the visualization of extravasation and subsequent transcatheter arterial embolization in 11 of 14 (79%) cases, with extravasation seen during either CO2-enhanced angiography (n = 8) or subsequent repeat iodinated contrast-enhanced angiography immediately after negative CO2-enhanced angiography (n = 3). Conservative treatment was performed in the remaining 3 cases. In conclusion, CO2-enhanced angiography appears useful for identifying occult lower gastrointestinal bleeding.

Detection of carbon dioxide embolism by transesophageal echocardiography during transanal/perineal endoscopic surgery: a pilot study.

The transanal/perineal (ta/tp) endoscopic approach has been widely used for anorectal surgery in recent years, but carbon dioxide embolism is a possible lethal complication. The frequency of this complication in this approach is not known. In this study, we investigated the frequency of intraoperative (including occult) carbon dioxide embolism using transesophageal echocardiography. Patients who underwent surgery via the ta/tp approach and consented to participate were included. Intraoperative transesophageal echocardiography was used to observe the right ventricular system in a four-chamber view. Changes in end-tidal carbon dioxide (EtCO2), oxygen saturation (SpO2), and blood pressure were taken from anesthesia records. Median maximum insufflation pressure during the ta/tp approach was 13.5 (12-18) mmHg. One patient (4.8%) was observed to have a bubble in the right atrium on intraoperative transesophageal echocardiography, with a decrease in EtCO2 from 39 to 35 mmHg but no obvious change in SpO2 or blood pressure. By lowering the insufflation pressure from 15 to 10 mmHg and controlling bleeding from the veins around the prostate, the gas rapidly disappeared and the operation could be continued. Among all patients, the range of variation in intraoperative EtCO2 was 5-22 mmHg, and an intraoperative decrease in EtCO2 of > 3 mmHg within 5 min was observed in 19 patients (median 5 mmHg in 1-10 times).Clinicians should be aware of carbon dioxide embolism as a rare but potentially lethal complication of anorectal surgery, especially when using the ta/tp approach.

Extracorporeal carbon dioxide removal in acute hypoxaemic respiratory failure: a systematic review, Bayesian meta-analysis and trial sequential analysis.

PURPOSE: To assess the safety and efficacy of extracorporeal carbon dioxide removal (ECCO2R) versus standard care in patients with acute hypoxaemic respiratory failure (AHRF). METHODS: MEDLINE, Embase and clinical trial registries were searched from 1994 to 31 December 2021. We included randomised controlled trials (RCTs) and observational studies. Pairs of reviewers independently extracted data and assessed the risk of bias. The primary outcome was mortality. Secondary outcomes included ventilator-free days, length of stay, safety and adverse events and physiological changes. As a primary analysis, we performed a meta-analysis of mortality until day 30 using a Bayesian random effects model. We then performed a trial sequential analysis of RCTs. RESULTS: 21 studies met inclusion criteria: three RCTs, enrolling 531 patients, and 18 observational studies. In a pooled analysis of RCTs, the posterior probability of increased mortality with the use of ECCO2R was 73% (relative risk 1.19, 95% credible interval 0.70-2.29). There was substantial heterogeneity in the reporting of safety and adverse events. However, the incidence of extra and intracranial haemorrhage was higher (relative risk 3.00, 95% credible interval 0.41-20.51) among those randomised to ECCO2R. Current trials have accumulated 80.8% of the diversity-adjusted required information size and the lack of effect reaches futility for a 10% absolute risk reduction in mortality. CONCLUSIONS: The use of ECCO2R in patients with AHRF is not associated with improvements in clinical outcomes. Furthermore, it is likely that further trials of ECCO2R aiming to achieve an absolute risk reduction in mortality of ≥10% are futile.

Respiratory Effects of the Atypical Tricyclic Antidepressant Tianeptine in Human Models of Opioid-induced Respiratory Depression.

BACKGROUND: Animal data suggest that the antidepressant and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor modulator tianeptine is able to prevent opioid-induced respiratory depression. The hypothesis was that oral or intravenous tianeptine can effectively prevent or counteract opioid-induced respiratory depression in humans. METHODS: Healthy male and female volunteers participated in two studies that had a randomized, double blind, placebo-controlled, crossover design. First, oral tianeptine (37.5-, 50-, and 100-mg doses with 8 subjects) pretreatment followed by induction of alfentanil-induced respiratory depression (alfentanil target concentration, 100 ng/ml) was tested. Primary endpoint was ventilation at an extrapolated end-tidal carbon dioxide concentration of 55 mmHg (V̇E55). Next, the ability of four subsequent and increasing infusions of intravenous tianeptine (target tianeptine plasma concentrations 400, 1,000, 1,500, and 2,000 ng/ml, each given over 15 min) to counteract remifentanil-induced respiratory depression was determined in 15 volunteers. Ventilation was measured at isohypercpania (baseline ventilation 20 ± 2 l/min). The primary endpoint was minute ventilation during the 60 min of tianeptine versus placebo infusion. RESULTS: Alfentanil reduced V̇E55 to 13.7 (95% CI, 8.6 to 18.8) l/min after placebo pretreatment and to 17.9 (10.2 to 25.7) l/min after 50-mg tianeptine pretreatment (mean difference between treatments 4.2 (-11.5 to 3.0) l/min, P = 0.070). Intravenous tianeptine in the measured concentration range of 500 to 2,000 ng/ml did not stimulate ventilation but instead worsened remifentanil-induced respiratory depression: tianeptine, 9.6 ± 0.8 l/min versus placebo 15.0 ± 0.9 l/min; mean difference, 5.3 l/min; 95% CI, 2.5 to 8.2 l/min; P = 0.001, after 1 h of treatment. CONCLUSIONS: Neither oral nor intravenous tianeptine were respiratory stimulants. Intravenous tianeptine over the concentration range of 500 to 2000 ng/ml worsened respiratory depression induced by remifentanil.

Outlying End-Tidal Carbon Dioxide During General Anesthesia Is Associated With Postoperative Pulmonary Complications: A Multicenter Retrospective Observational Study From US Hospitals Between 2010 and 2017.

BACKGROUND: Postoperative pulmonary complications (PPCs) occur in up to 33% of patients who undergo noncardiothoracic surgery. Emerging evidence suggests that permissive hypercapnia may reduce the risk of lung injury. We hypothesized that higher intraoperative end-tidal carbon dioxide (Etco2) concentrations would be associated with a decreased risk of PPCs. METHODS: This retrospective, observational, multicenter study included patients undergoing general anesthesia for noncardiothoracic procedures (January 2010-December 2017). The primary outcome was PPC within 30 postoperative days. Secondary outcomes were PPC within 1 week, postoperative length of stay, and inhospital 30-day mortality. The association between these outcomes, median Etco2, and 4 time-weighted average area-under-the-curve (TWA-AUC) thresholds (<28, <35, <45, and >45 mm Hg) was explored using a multivariable mixed-effect model and by plotting associated risks. RESULTS: Among 143,769 cases across 11 hospitals, 10,276 (7.1%) experienced a PPC. When compared to a baseline median Etco2 of 35 to 40 mm Hg, a median Etco2 >40 mm Hg was associated with an increase in PPCs within 30 days (median Etco2, 40-45 mm Hg; adjusted OR, 1.16 [99% confidence interval {CI}, 1.00-1.33]; P value = .008 and median Etco2, >45 mm Hg; OR, 1.64 [99% CI, 1.33-2.02]; P value < .001). The occurrence of any Etco2 value <28 mm Hg (ie, a positive TWA-AUC < 28 mm Hg) was associated with PPCs (OR, 1.40 [95% CI, 1.33-1.49]; P value < .001), mortality, and length of stay. Any Etco2 value >45 mm Hg (ie, a positive TWA-AUC >45 mm Hg) was also associated with PPCs (OR, 1.24 [95% CI, 1.17-1.31]; P < .001). The Etco2 range with the lowest incidence of PPCs was 35 to 38 mm Hg. CONCLUSIONS: Both a very low (<28 mm Hg) and a high Etco2 (>45 mm Hg) were associated with PPCs within 30 days. The lowest PPC incidence was found in patients with an Etco2 of 35 to 38 mm Hg. Prospective studies are needed to clarify the relationship between postoperative PPCs and intraoperative Etco2.