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Ventilation-perfusion mismatch in anesthesia

Kenji Watanabe, Nobuko Ito, Takuya Ohata, Taro Kariya, Hiroshi Inui, Yoshitsugu Yamada
RATIONALE: Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease with a poor prognosis, characterized by chronic thromboembolic obstruction of the pulmonary arteries and pulmonary hypertension. Balloon pulmonary angioplasty (BPA) is a newly emergent treatment for CTEPH, which may substitute pulmonary endarterectomy, the standard but more invasive treatment for CTEPH. Here, we report the case of a CTEPH patient who underwent 2 noncardiac surgeries without complications after preoperative intervention of BPA...
March 2019: Medicine (Baltimore)
Ben Korman, Ranjan K Dash, Philip J Peyton
The second gas effect (SGE) occurs when nitrous oxide enhances the uptake of volatile anesthetics administered simultaneously. Recent work shows that the SGE is greater in blood than in the gas phase, that this is due to ventilation-perfusion mismatch, that as mismatch increases, the SGE increases in blood but is diminished in the gas phase, and that these effects persist well into the period of nitrous oxide maintenance anesthesia. These modifications of the SGE are most pronounced with the low soluble agents in current use...
December 6, 2018: Journal of Applied Physiology
Julien Dupont, Didier Serteyn, Charlotte Sandersen
Horses are susceptible to developing large areas of pulmonary atelectasis during recumbency and anesthesia. The subsequent pulmonary shunt is responsible for significant impairment of oxygenation. Since ventilation perfusion mismatch persists into the post-operative period, hypoxemia remains an important concern in the recovery stall. This case report describes the diagnosis and supportive therapy of persistent hypoxemia in a 914 kg draft horse after isoflurane anesthesia. It highlights how challenging it can be to deal with hypoxemia after disconnection from the anesthesia machine and how life-threatening it can become if refractory to treatment...
2018: Frontiers in Veterinary Science
Hiroki Nishine, Hiromi Muraoka, Takeo Inoue, Teruomi Miyazawa, Masamichi Mineshita
Stenting at the flow-limiting segment can improve the ventilation-perfusion ratio in patients with central airway stenosis. However, there is no quantitative examination for assessing the perfusion status during interventional bronchoscopy. Intrabronchial capnography can estimate regional gas exchange by measuring carbon dioxide concentration. We herein report a case of bilateral bronchial stenosis where stenting was able to improve ventilation-perfusion ratio using intrabronchial capnography. A 44-year-old man was admitted to our institution with orthopnea...
2018: Respiration; International Review of Thoracic Diseases
Ben Korman, Ranjan K Dash, Philip J Peyton
BACKGROUND: Recent clinical studies suggest that the magnitude of the second gas effect is considerably greater on arterial blood partial pressures of volatile agents than on end-expired partial pressures, and a significant second gas effect on blood partial pressures of oxygen and volatile agents occurs even at relatively low rates of nitrous oxide uptake. We set out to further investigate the mechanism of this phenomenon with the help of mathematical modeling. METHODS: Log-normal distributions of ventilation and blood flow were generated representing the range of ventilation-perfusion scatter seen in patients during general anesthesia...
June 2018: Anesthesiology
Savino Spadaro, Salvatore Grasso, Dan Stieper Karbing, Alberto Fogagnolo, Marco Contoli, Giacomo Bollini, Riccardo Ragazzi, Gilda Cinnella, Marco Verri, Narciso Giorgio Cavallesco, Stephen Edward Rees, Carlo Alberto Volta
BACKGROUND: Arterial oxygenation is often impaired during one-lung ventilation, due to both pulmonary shunt and atelectasis. The use of low tidal volume (VT) (5 ml/kg predicted body weight) in the context of a lung-protective approach exacerbates atelectasis. This study sought to determine the combined physiologic effects of positive end-expiratory pressure and low VT during one-lung ventilation. METHODS: Data from 41 patients studied during general anesthesia for thoracic surgery were collected and analyzed...
March 2018: Anesthesiology
Moritz Kretzschmar, Alf Kozian, James E Baumgardner, Joao Batista Borges, Göran Hedenstierna, Anders Larsson, Thomas Hachenberg, Thomas Schilling
BACKGROUND: Increasing numbers of patients with obstructive lung diseases need anesthesia for surgery. These conditions are associated with pulmonary ventilation/perfusion (VA/Q) mismatch affecting kinetics of volatile anesthetics. Pure shunt might delay uptake of less soluble anesthetic agents but other forms of VA/Q scatter have not yet been examined. Volatile anesthetics with higher blood solubility would be less affected by VA/Q mismatch. We therefore compared uptake and elimination of higher soluble isoflurane and less soluble desflurane in a piglet model...
November 2017: Anesthesiology
Laura A Wilding, Joe A Hampel, Basma M Khoury, Stacey Kang, David Machado-Aranda, Krishnan Raghavendran, Jean A Nemzek
At research institutions, isoflurane delivered by precision vaporizer to a face mask is the standard for rodent surgery and for procedures with durations that exceed a few minutes. Pure oxygen is often used as the carrier gas for isoflurane anesthesia, despite documented complications from long-term 100% oxygen use in humans and known occupational safety risks. We therefore examined the effect of anesthetic delivery gas on physiologic variables in mice and rats. Rodents were anesthetized for 60 min with isoflurane delivered in either 21% or 100% oxygen by means of a nose cone...
March 1, 2017: Journal of the American Association for Laboratory Animal Science: JAALAS
Ary Serpa Neto, Marcus J Schultz, Arthur S Slutsky
Mechanical ventilation with high tidal volumes (VT) has been common practice in operating theatres because this strategy recruits collapsed lung tissue and improves ventilation-perfusion mismatch, thus decreasing the need for high inspired oxygen concentrations. Positive end-expiratory pressure (PEEP) was not used routinely because it was thought to impair cardiovascular function. Over the past two decades there have been advances in our understanding of the causes and importance of ventilation-induced lung injury based on studies in animals with healthy lungs, and trials in critically ill patients with and without acute respiratory distress syndrome...
2015: Swiss Medical Weekly
James E Baumgardner, Göran Hedenstierna
PURPOSE OF REVIEW: A major cause of hypoxemia in anesthesia is ventilation-perfusion (VA/Q) mismatch. With more advanced surgery and an aging population, monitoring of VA/Q is of increasing importance. RECENT FINDINGS: The classic multiple inert gas elimination technique has been simplified with a new approach based on mass spectrometry. VA/Q distributions can also be measured, at the bedside, by varying inspired oxygen concentration. MRI, 3-dimensional single photon emission computed tomography, positron emission tomography, and electrical impedance tomography enable imaging of perfusion and ventilation, and in some of the techniques also the distribution of inflammation...
February 2016: Current Opinion in Anaesthesiology
Marcin Karcz, Peter J Papadakos
General anesthesia and mechanical ventilation impair pulmonary function, even in normal individuals, and result in decreased oxygenation in the postanesthesia period. They also cause a reduction in functional residual capacity of up to 50% of the preanesthesia value. It has been shown that pulmonary atelectasis is a common finding in anesthetized individuals because it occurs in 85% to 90% of healthy adults. Furthermore, there is substantial evidence that atelectasis, in combination with alveolar hypoventilation and ventilation-perfusion mismatch, is the core mechanism responsible for postoperative hypoxemic events in the majority of patients in the postanesthesia care unit (PACU)...
2013: Canadian Journal of Respiratory Therapy: CJRT
Stijn Schauvliege, Ioannis Savvas, Frank Gasthuys
OBJECTIVES: To investigate the influence of two inspired oxygen fractions (FiO(2)) on the arterial oxygenation in horses anaesthetized with isoflurane. STUDY DESIGN: Retrospective, case-control clinical study. ANIMALS: Two hundred equine patients undergoing non-abdominal surgery (ASA class 1-2), using a standardized anaesthetic protocol and selected from anaesthetic records of a period of three years, based on pre-defined inclusion criteria...
May 2015: Veterinary Anaesthesia and Analgesia
A K Staehr-Rye, L S Rasmussen, J Rosenberg, C Steen-Hansen, T F Nielsen, C V Rosenstock, H V Clausen, M K Sørensen, J VON H Regeur, M R Gätke
BACKGROUND: Pulmonary function may be impaired in connection with laparoscopic surgery, especially in the head-down body position, but the clinical importance has not been assessed in detail. The aim of this study was to assess pulmonary function after laparoscopic hysterectomy and laparoscopic cholecystectomy. We hypothesised that arterial oxygenation would be more impaired after hysterectomy performed in the head-down position than after cholecystectomy in the head-up position. METHODS: We included 60 women in this prospective, observational study...
February 2014: Acta Anaesthesiologica Scandinavica
Göran Hedenstierna, Hans Ulrich Rothen
Anaesthesia causes a respiratory impairment, whether the patient is breathing spontaneously or is ventilated mechanically. This impairment impedes the matching of alveolar ventilation and perfusion and thus the oxygenation of arterial blood. A triggering factor is loss of muscle tone that causes a fall in the resting lung volume, functional residual capacity. This fall promotes airway closure and gas adsorption, leading eventually to alveolar collapse, that is, atelectasis. The higher the oxygen concentration, the faster will the gas be adsorbed and the aleveoli collapse...
January 2012: Comprehensive Physiology
Tamara Grubb, Jan H M Frendin, Anna Edner, Pia Funkquist, Göran Hedenstierna, Görel Nyman
OBJECTIVES: Anaesthetized horses commonly become hypoxaemic due to ventilation/perfusion (V·A/Q·) mismatch and increased pulmonary shunt fraction (Qs·/Qt·). Pulse-delivered inhaled nitric oxide may improve oxygenation but may increase plasma concentration of the potent vasoconstrictor, endothelin-1 (ET-1). Objectives: Study 1) compare arterial oxygen concentration (PaO2) and saturation (SaO2), calculated Qs·/Qt· and ET-1 concentration; and Study 2) assess V·A/Q· matching and measured Qs·/Qt· in isoflurane-anaesthetized horses in left lateral recumbency receiving pulse-delivered inhaled nitric oxide (PiNO group) or inhalant gas only (C group)...
November 2013: Veterinary Anaesthesia and Analgesia
S Matsuse, Y Hara, T Ohkura, N Yahagi
During one-lung ventilation, ventilation-perfusion mismatch decreases the arterial concentration of inhaled anaesthetics due to the arterial-to-venous concentration difference. This study tested the hypothesis that in humans, the 'presumed effect-site concentration' (taken as the mid-point between the arterial and superior jugular venous concentrations) of inhaled anaesthetic falls during one-lung (vs two-lung) ventilation. Four patients scheduled for elective prostatectomy (two-lung ventilation) and four patients for elective thoracotomy (one-lung ventilation) were randomly selected and assigned to receive sevoflurane (vaporiser-dial setting, 1...
October 2012: Anaesthesia
Aloka Samantaray, Nathan Hemanth
BACKGROUND: The cardiopulmonary bypass (CPB)-associated atelectasis accounted for most of the marked post-CPB increase in shunt and hypoxemia. We hypothesized that pressure-regulated volume-control (PRVC) modes having a distinct theoretical advantage over pressure-controlled ventilation (PCV) by providing the target tidal volume at the minimum available pressure may prove advantageous while ventilating these atelactic lungs. METHODS: In this prospective study, 36 post-cardiac surgical patients with a PaO(2)/FiO(2) (arterial oxygen tension/Fractional inspired oxygen) < 300 after arrival to intensive care unit (ICU), (n = 34) were randomized to receive either PRVC or PCV...
April 2011: Saudi Journal of Anaesthesia
Terry J Kreeger, Matthew Huizenga, Cole Hansen, Benjamin L Wise
From October 2009 through July 2010, five captive, 3-yr-old, female Rocky Mountain elk (Cervus elaphus) and nine free-ranging elk (one male, eight female) were immobilized with 0.1 mg/kg sufentanil plus 0.5 mg/kg xylazine which was antagonized with 1 mg/kg naltrexone and 2 mg/kg tolazoline. Induction and recovery times averaged 4.9 ± 0.3 min and 3.9 ± 0.4 min, respectively. Physiologic and blood gas parameters as well as bispectral index (BIS) were measured on the captive elk every 10 min for 30 min. Immobilization induced profound hypoxemia via hypoventilation and ventilation-perfusion mismatching as demonstrated by depressed partial pressure of arterial oxygen (P(a)O(2)) and increased partial pressure of arterial carbon dioxide (P(a)CO(2))...
July 2011: Journal of Wildlife Diseases
Christian S Bruells, Rolf Rossaint
Mechanical ventilation is a prerequisite for many surgical interventions. Furthermore, during states of severe gas exchange disturbance or impaired neurological conditions with the threat of aspiration or cardiovascular instability, it is a life-saving intervention on every ICU. Even the induction of anaesthesia disturbs the physiological lung function, due to changes in chest wall mechanics and diaphragm relaxation, generating atelectases, gas exchange disturbance and ventilation-perfusion mismatch. Additionally, the application of positive pressure to lung structures elicits ventilator-induced lung injury, with the severity of injury dependent on the applied volume, peak pressures and levels of positive end-expiratory pressure...
August 2011: European Journal of Anaesthesiology
John A E Hubbell, Turi K Aarnes, Richard M Bednarski, Phillip Lerche, William W Muir
BACKGROUND: The purpose of this study was to compare the effects of 0.5 fraction of inspired oxygen (FiO₂) and >0.95 FiO₂ on pulmonary gas exchange, shunt fraction and oxygen delivery (DO₂) in dorsally recumbent horses during inhalant anesthesia. The use of 0.5 FiO₂ has the potential to reduce absorption atelectasis (compared to maximal FiO₂) and augment alveolar oxygen (O₂) tensions (compared to ambient air) thereby improving gas exchange and DO₂. Our hypothesis was that 0...
2011: BMC Veterinary Research
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