Effect of Global Ventilation to Perfusion Ratio, for Normal Lungs, on Desflurane and Sevoflurane Elimination Kinetics

Background Kinetics of the uptake of inhaled anesthetics have been well studied, but the kinetics of elimination might be of more practical importance. The objective of the authors’ study was to assess the effect of the overall ventilation/perfusion ratio ( .VA/.Q ), for normal lungs, on elimination kinetics of desflurane and sevoflurane. Methods The authors developed a mathematical model of inhaled anesthetic elimination that explicitly relates the terminal washout time constant to the global lung .VA/.Q ratio. Assumptions and results of the model were tested with experimental data from a recent study, where desflurane and sevoflurane elimination were observed for three different .VA/.Q conditions: normal, low, and high. Results The mathematical model predicts that the global .VA/.Q ratio, for normal lungs, modifies the time constant for tissue anesthetic washout throughout the entire elimination. For all three .VA/.Q conditions, the ratio of arterial to mixed venous anesthetic partial pressure Part/Pmv reached a constant value after 5 min of elimination, as predicted by the retention equation. The time constant corrected for incomplete lung clearance was a better predictor of late-stage kinetics than the intrinsic tissue time constant. Conclusions In addition to the well-known role of the lungs in the early phases of inhaled anesthetic washout, the lungs play a long-overlooked role in modulating the kinetics of tissue washout during the later stages of inhaled anesthetic elimination. The .VA/.Q ratio influences the kinetics of desflurane and sevoflurane elimination throughout the entire elimination, with more pronounced slowing of tissue washout at lower .VA/.Q ratios. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Arterial and Mixed Venous Kinetics of Desflurane and Sevoflurane, Administered Simultaneously, at Three Different Global Ventilation to Perfusion Ratios in Piglets with Normal Lungs

Background Previous studies have established the role of various tissue compartments in the kinetics of inhaled anesthetic uptake and elimination. The role of normal lungs in inhaled anesthetic kinetics is less understood. In juvenile pigs with normal lungs, the authors measured desflurane and sevoflurane washin and washout kinetics at three different ratios of alveolar minute ventilation to cardiac output value. The main hypothesis was that the ventilation/perfusion ratio ( .VA/.Q ) of normal lungs influences the kinetics of inhaled anesthetics. Methods Seven healthy pigs were anesthetized with intravenous anesthetics and mechanically ventilated. Each animal was studied under three different .VA/.Q conditions: normal, low, and high. For each .VA/.Q condition, desflurane and sevoflurane were administered at a constant, subanesthetic inspired partial pressure (0.15 volume% for sevoflurane and 0.5 volume% for desflurane) for 45 min. Pulmonary arterial and systemic arterial blood samples were collected at eight time points during uptake, and then at these same times during elimination, for measurement of desflurane and sevoflurane partial pressures. The authors also assessed the effect of .VA/.Q on paired differences in arterial and mixed venous partial pressures. Results For desflurane washin, the scaled arterial partial pressure differences between 5 and 0 min were 0.70 ± 0.10, 0.93 ± 0.08, and 0.82 ± 0.07 for the low, normal, and high .VA/.Q conditions (means, 95% CI). Equivalent measurements for sevoflurane were 0.55 ± 0.06, 0.77 ± 0.04, and 0.75 ± 0.08. For desflurane washout, the scaled arterial partial pressure differences between 0 and 5 min were 0.76 ± 0.04, 0.88 ± 0.02, and 0.92 ± 0.01 for the low, normal, and high .VA/.Q conditions. Equivalent measurements for sevoflurane were 0.79 ± 0.05, 0.85 ± 0.03, and 0.90 ± 0.03. Conclusions Kinetics of inhaled anesthetic washin and washout are substantially altered by changes in the global .VA/.Q ratio for normal lungs. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Treatment of Acute Severe Asthma Exacerbation with Extracorporeal Membrane Oxygenation and Inhaled Volatile Anesthetic

Severe asthma affects approximately 1-2% of all asthmatic patients. Acute exacerbations are associated with high mortality in this population. There are many treatment options for asthma exacerbation; however, if these treatments fail, patients can develop progressive hypoxia, hypercarbia, respiratory acidosis, and hemodynamic instability. Extracorporeal membrane oxygenation (ECMO) and inhaled anesthetic both have a role in the management of acute severe refractory asthma exacerbation, though there is limited information about the use of both together. We present the case of a patient with severe asthma who suffered a refractory asthma exacerbation and was successfully managed with veno-venous ECMO and inhaled anesthetic. ECMO and inhaled volatile anesthetic both have a role in the management of severe refractory asthma exacerbations. It is safe and beneficial to use these therapies together and more benefit is noted if initiated early in the course of the patient’s illness.

Biochemical markers of surgical stress in endoscopic rhinosinus surgery under combined anesthesia in children

BACKGROUND: Endoscopic rhinosinus surgery in children is associated with a high anesthetic risk because of intraoperative stress. This study aimed to, considering the dynamic picture of the biochemical markers of surgical stress, to assess the effectiveness of regional methods of combined anesthesia in rhinosinus surgery in children. MATERIALS AND METHODS: A comparative study was conducted in parallel groups composed of 100 patients aged 617 years who had undergone an assessment of their physical condition using the ASA I-II scales and planned endoscopic endonasal surgery lasting up to 2 h under combined anesthesia. In all groups, the introductory anesthesia was combined, i.e., inhalation of sevoflurane in an oxygenair mixture in combination with intravenous administration of propofol. To ensure the patency of the respiratory tract, endotracheal anesthesia was administered. Patients were divided into two groups of 50 people each, depending on the method of maintaining anesthesia. Group 1 received inhalation of sevoflurane in an airoxygen mixture with a target value of the minimum alveolar concentration of (MAC) 0.70.9, and regional blockage was performed bilaterally, i.e., pterygopalatine anesthesia with palatine access (palatinal) and infra-orbital intraoral access with ropivacaine solution. Group 2 received inhalation of sevoflurane in an airoxygen mixture with a target value of 1.5 МАС, and 5% tramadol solution was used intravenously for analgesia. RESULTS: Data on the dynamics of glucose, lactate, and cortisol levels in both groups proved the effectiveness and stability of the anesthesia methods used. However, the concentration of the inhaled anesthetic agent in the tramadol group was used was twice as high as the concentration in the regional anesthetic group. DISCUSSION: The dynamics and deviations of biochemical markers of surgical stress were not significantly different in the intergroup and intragroup interstage parameters beyond the reference values. CONCLUSIONS: The proposed anesthesia methods did not induce stress reactions to surgical intervention, and the anesthesia methods in both groups were adequate and effective.

Suspected Malignant Hyperthermia and the Application of a Multidisciplinary Response

Purpose: Malignant hyperthermia (MH) is a critical and potentially life-threatening emergency associated with inhaled anesthetic and depolarizing neuromuscular blocker administration. This is a single center’s response to MH. Summary: When signs of MH are observed, a page for “anesthesia STAT-MH crisis” is called, triggering a multidisciplinary response, including the deployment of a Malignant Hyperthermia Cart. The MH cart and the delegation of duties allows nurses, physicians and pharmacists to quickly understand their role in the stabilization, transition and recovery of a suspected MH patient. Conclusion: This case highlights the importance of multi-disciplinary involvement in these rare, but potentially fatal, cases.

Prophylactic premedication can reduce Emergence Agitation after Sevoflurane Anesthesia in Pediatrics: A placebo-controlled prospective trial.

Sevoflurane is an inhaled anesthetic widely used for pediatric anesthesia, but emergence agitation (EA) or emergence delirium (ED) is a common sevoflurane anesthesia recovery-associated problem.1 Emergence agitation is associated with increased risk of injury in children and parents' dissatisfaction with anesthesia care.2 In a web-based survey of pediatric anesthesiologists in Canadian Pediatric Anesthesia Society, 42% felt that EA was a significant problem and 45% of them were giving medication before or during anesthesia to prevent its development.