手术前后的呼吸衰竭

手術前後呼吸衰竭 Perioperative Respiratory Failure 重症課程 2004.07.01. Key Manifestations nPulmonary edema (肺積水, 水分太多) nAtelectasis (肺塌陷, 容量減少) nAlveolar hypoventilation (換氣不足) nAspiration (異物吸入) Pulmonary Edema nMicrovascular hydrostatic pressure n“normal” response trauma ADH, aldosterone conserve water nFluid overload nPulmonary capillary permeability nUnrecognized sepsis Lung Edema Atelectasis (collapse) nConcepts nFRC nClosing volume nPerioperative Atelectasis nReduced FRC nIncreased closing volume Lung Volumes IRV ERV RV TV FRC TLC CV nFunctional residual capacity (FRC) is the volume of air in the lungs at the end of a normal expiration. nFRC is determined by a balance between the inward elastic forces of the lung and the outward forces of the respiratory cage (mostly due to muscle tone). nFRC falls with lying supine, obesity, pregnancy and anaesthesia, though not with age. The FRC is of particularly importance to anaesthetists because: nDuring apnoea it is the reservoir to supply oxygen to the blood nAs it falls the distribution of ventilation within the lungs changes leading to mismatching with pulmonary blood flow nIf it falls below a certain volume (the closing capacity), airway closure occurs leading to shunt (see later - Ventilation/perfusion/shunt) Lung Collapse Risk Factors of Atelectasis PromotingPreventing Reduced FRC SupineUpright ObesityAlternating postures AscitesPEEP PeritonitisSighs Upper abdominal incisionAnalgesia Increased closing volume AgePreop physiotherapy SmokingCessation BronchospasmBronchodilation Airway secretionCough, suction Pulmonary edemaAvoid over hydration Atelectasis nDiaphragm dysfunction nUpper abdominal surgery nComplex effects nFall in vital capacity, decrease in FRC, increase in closing volume nA major component of perioperative respiratory failure Diaphragm Dysfunction Alveolar Hypoventilation nImpairment of ventilation nPain nPeritonitis nAnesthesia nCNS injury nIncreased metabolic requirement Aspiration nGastric acid aspiration nVariable presentation nOne of the major causes of morbidity and mortality The Treatment of Acid Aspiration lrapid removal of debris l placement of a nasogastric tube l oxygen administration and mechanical l ventation l bronchodilator therapy l maintenance of normovolemia l treatment of pnemonia Predicting and Preventing nRisk factors correction nLung function study nNo precise parameters nSpecific respiratory dysfunction treatment modalities improve preoperative status nLung resection Treatment Principles n