Canadian Journal of Anesthesia-Journal Canadien D Anesthesie最新文献

Purpose: Initially introduced as a safer alternative to smoking, electronic cigarettes (e-cigarettes) and vaping have since been associated with lung injury. Nevertheless, there is limited perioperative data on their potential contribution to the harmful effects of mechanical ventilation on the lungs. We hypothesized that, in adults undergoing noncardiothoracic surgeries, preoperative vaping/e-cigarette use is associated with hypoxemia during the first postoperative hour, and with an increased incidence of intraoperative and postoperative pulmonary complications.

Methods: We conducted a retrospective cohort study in which we included patients reporting as vapers/e-cigarette users within one year before surgery as the exposure group, and nonvapers as the control group. The primary outcome was the time-weighted average (TWA) SpO₂/F_IO₂ ratio in the postanesthesia care unit during the first postoperative hour. The secondary outcome was a composite of intraoperative and postoperative pulmonary complications until discharge. We used entropy balancing to adjust for confounding, and fit weighted linear regression and logistic regression models to estimate treatment effects.

Results: A total of 110,940 patients met the inclusion criteria, and 1,941 of these were vapers/e-cigarette users. The average treatment effect on the treated for TWA SpO₂/F_IO₂ ratio (N = 109,217) was estimated to be a mean difference of 4 (95% confidence interval [CI], 1 to 8; P = 0.007). This is equivalent to a 4% change in SpO₂ at a 30% F_IO₂ (or at a fixed F_IO₂). The difference was statistically significant. The average treatment effect on the treated for experiencing intraoperative and postoperative pulmonary complications (N = 110,940) was an odds ratio of 1.04 (95% CI, 0.71 to 1.54; P = 0.84).

Conclusion: Vaping/e-cigarette use was neither associated with clinically significant hypoxemia during the first hour in the postanesthesia care unit nor with an increase in pulmonary complications. Nevertheless, our findings cannot definitively exclude the deleterious effects of vaping and e-cigarette use on the lungs, and anesthesiologists should consider potential perioperative complications.

Purpose: Opioid anesthesia is commonly employed in minimally invasive surgeries but is associated with adverse effects, including postoperative nausea and vomiting (PONV). Opioid-free anesthesia aims to mitigate these issues. We conducted a systematic review, meta-analysis, and trial sequential analysis (TSA) comparing opioid and opioid-free anesthesia in minimally invasive abdominal surgeries.

Methods: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase for randomized controlled trials (RCTs) comparing these approaches. Our primary outcomes were adverse effects (PONV, bradycardia), while secondary outcomes were pain, opioid consumption, and postanesthesia care unit (PACU) length of stay (LOS). We performed a TSA to investigate the conclusiveness of the results.

Results: We included 26 RCTs encompassing 2,025 patients, with 1,009 (49%) in the opioid-free anesthesia group. Opioid-free anesthesia reduced PONV significantly (risk ratio, 0.55; 95% confidence interval [CI], 0.40 to 0.74; P < 0.001), but we found no significant differences in bradycardia rates. We found nonclinically relevant higher pain scores for opioid anesthesia (mean difference [MD], -0.9; 95% CI, -1.7 to -0.2; P = 0.01) and opioid consumption at 2 hr post surgery (MD, -5.4 mg oral morphine equivalents; 95% CI, -9.1 to -1.8; P = 0.004). We also noted a reduced time to first analgesia (MD, 88 min; 95% CI, 18 to 159; P = 0.01). We found no differences in PACU LOS. The TSA confirmed the sample size's adequacy in showing PONV reduction with opioid-free anesthesia.

Conclusion: Opioid-free anesthesia showed a significant reduction in PONV and a decrease in opioid consumption during the first 2 hr postoperatively, suggesting it can be an alternative to opioid anesthesia in minimally invasive abdominal surgeries.

Study registration: PROSPERO ( CRD42023492385 ); first submitted 18 December 2023.

Purpose: There is significant variability in the application of positive end-expiratory pressure (PEEP) in patients undergoing invasive mechanical ventilation. There are numerous studies assessing methods of determining optimal PEEP, but many methods, patient populations, and study settings lack high-quality evidence. Guidelines make no recommendations about the use of a specific method because of equipoise and lack of high-quality evidence. We conducted a scoping review to determine which methods of determining optimal PEEP have been studied and what gaps exist in the literature.

Source: We searched five databases for primary research reports studying methods of determining optimal PEEP among adults undergoing invasive mechanical ventilation. Data abstracted consisted of the titration method, setting, study design, population, and outcomes.

Principle findings: Two hundred and seventy-one studies with 17,205 patients met the inclusion criteria, including 73 randomized controlled trials (RCTs) with 10,733 patients. We identified 22 methods. Eleven were studied with an RCT. Studies enrolled participants within an intensive care unit (ICU) (216/271, 80%) or operating room (55/271, 20%). Most ICU studies enrolled patients with acute respiratory distress syndrome (162/216, 75%). The three most studied methods were compliance (73 studies, 29 RCTs), imaging-based methods (65 studies, 11 RCTs), and use of PEEP-F_IO₂ tables (52 studies, 20 RCTs). Among ICU RCTs, the most common primary outcomes were mortality or oxygenation. Few RCTs assessed feasibility of different methods (n = 3). The strengths and limitations of each method are discussed.

Conclusion: Numerous methods of determining optimal PEEP have been evaluated; however, notable gaps remain in the evidence supporting their use. These include specific populations (normal lungs, patients weaning from mechanical ventilation) and using alternate outcomes (ventilator-free days and feasibility) and they present significant opportunities for future study.

Study registration: Open Science Framework ( https://osf.io/atzqc ); first posted, 19 July 2022.

Purpose: Platypnea orthodeoxia syndrome (POS) is a rare cause of hypoxemia. Diagnosis of POS is challenging, requiring a high index of clinical suspicion, special investigations, and collaboration with multiple specialists.

Clinical features: We describe an 86-yr-old male who presented to the emergency department with hip pain after a witnessed fall. He was noted to be hypoxemic at presentation with a peripheral oxygen saturation (SpO₂) of 84% on room air, with an inadequate increase in oxygenation after administration of a fractional concentration of inspired oxygen (F_IO₂) of 1.00. A chest radiograph, computed tomography pulmonary angiogram, and Doppler ultrasound of the liver were unremarkable. In the supine position with an F_IO₂ of 0.65, his SpO₂ and arterial partial pressure of oxygen (PaO₂) (96% and 74 mm Hg, respectively) increased significantly relative to the seated position (84% and 50 mm Hg, respectively). Contrast transthoracic echocardiography (TTE) showed a large patent foramen ovale (PFO) with right-to-left shunt. Transthoracic echocardiography showed rotation of the patient's heart, enabling direct alignment of the inferior vena cava with the PFO, creating a large anatomical right-to-left shunt in the seated position. Right heart catheterization confirmed a large PFO with normal right-sided heart pressures. He was treated with a septal occlusion and his SpO₂ in the seated position improved immediately. The patient was discharged home without requiring supplemental oxygen.

Conclusions: Platypnea orthodeoxia syndrome is a rare presentation of hypoxemia. Positional changes in oxygenation are the cardinal feature of POS. Discordance between lung imaging and the severity of hypoxemia should prompt investigation for an intracardiac shunt, which can occur in POS even in the absence of increased right-sided heart pressures. Either contrast TTE or transesophageal echocardiography is necessary to make this diagnosis.

Purpose: The purpose of our study was to determine the minimum effective dose of oxytocin maintenance infusion required to maintain adequate uterine tone in 90% of patients (ED₉₀) after administration of the initial bolus at elective Cesarean delivery (CD) under spinal anesthesia.

Methods: We conducted a prospective, double-blind dose-finding study with biased coin up-down design. Immediately after delivery, a 1-IU oxytocin bolus was administered, followed by a maintenance infusion. The obstetrician assessed the uterine tone by palpation as satisfactory or unsatisfactory. In case of unsatisfactory response, the dose for the next patient was increased by 2 IU·hr^-1. For satisfactory response, the dose for the next patient was either decreased by 2 IU·hr^-1 with a probability of 1/9, or remained unchanged. The primary outcome was a satisfactory uterine tone from five minutes after delivery until discharge from postanesthesia care unit. The secondary outcomes were blood loss, need for additional uterotonics, and side effects.

Results: We analyzed data for 40 patients. The ED₉₀ of oxytocin maintenance infusion was 4.5 IU·hr^-1 (95% confidence interval, 3.3 to 5.5) based on the isotonic regression estimator. The median [interquartile range] blood loss was 861 [553-1,181] mL; 18% received additional uterotonics, and 38% developed hypotension post delivery.

Conclusion: Based on the results of this dose-finding study, we recommend a maintenance infusion rate of 4.5 IU·hr^-1 following an oxytocin bolus of 1 IU for adequate uterine tone in pregnant patients undergoing elective CDs. This infusion rate is four-fold lower than that required without an initial bolus.

Study registration: ClinicalTrials.gov ( NCT04946006 ); first submitted 25 June 2021.

Purpose: The modified Mallampati classification is part of the preoperative airway risk assessment. Inconsistency in the way it is examined may contribute to heterogeneity in its diagnostic performance. The best visible Mallampati score could reduce interobserver heterogeneity but its diagnostic characteristics remain unknown.

Methods: During preoperative anesthesia consultation of adult patients with a senior anesthesiologist, we compared the modified Mallampati classification score vs the best visible Mallampati score using cervical extension, tongue in, and phonation. The primary outcome was the diagnostic characteristic of the modified Mallampati classification score vs the best visible Mallampati score as predictors of difficult orotracheal intubation (more than two direct laryngoscopies or need for an alternate device). We performed a multivariable analysis to identify independent predictors of difficult orotracheal intubation in the tested cohort.

Results: Difficult orotracheal intubation occurred in 77/3,243 (2.4%) patients. A best visible Mallampati score was obtained in 1,596 (49.2%) patients. Sensitivity and specificity of the modified Mallampati classification score for predicting difficult orotracheal intubation were 0.56 (95% confidence interval [CI], 0.44 to 0.66) and 0.69 (95% CI, 0.68 to 0.71), respectively. By comparison, the best visible Mallampati score was less sensitive (difference, -0.30; 95% CI, -0.19 to -0.30; P < 0.001) but more specific (difference, 0.24; 95% CI, 0.22 to -0.25; P < 0.001). In patients with difficult orotracheal intubation, 53% were incorrectly reclassified as low risk by the best visible Mallampati score.

Conclusion: Compared with the modified Mallampati classification score, the best visible Mallampati score decreased sensitivity for predicting difficult orotracheal intubation and falsely classified half of the patients with difficult orotracheal intubation. Taking the risks associated with difficult airways into account, our findings indicate that a careful examination of the modified Mallampati classification is required during the global preoperative airway examination.

Study registration: ClinicalTrials.gov ( NCT02788253 ); 9 February 2016.