tailieunhanh - AIRWAY MANAGEMENT IN EMERGENCIES - PART 2

Các bác sĩ nên nhận ra rằng các yếu tố khác có thể đóng góp cho sự xuất hiện của tím tái. Giảm dòng chảy tế bào máu có thể gây ra cái gọi là tím tái ngoại vi, trong đó rõ ràng tím tái xảy ra ngay cả với một lượng oxy động mạch bình thường. Điều này có thể được quan sát thấy ở bệnh nhân bị hạ thân nhiệt | AIRWAY PHYSIOLOGY AND ANATOMY 17 Time to Hemoglobin Desaturation with Initial Fao2 Figure 3-2. Times to oxygen desaturation following onset of apnea in preoxygenated elective surgical patients From Benumof J 1 with permission . MONITORING OXYGENATION Signs and symptoms of hypoxemia include tachycardia dysrhythmias tachypnea dyspnea cyanosis and mental status changes. All are nonspecific and of little value in reliably detecting hypoxemia. The clinician should be well-versed in the advantages and limitations of methods available for monitoring the oxygenation status of the critically ill patient. Cyanosis Cyanosis is a bluish discoloration of skin and mucus membranes which occurs with oxygen desaturation. The presence of cyanosis should be used as an indication to more objectively monitor and manage who is most likely a hypoxemic patient. Cyanosis will appear at an SaO2 of 85 -90 although variation exists. It will be less apparent in the anemic patient and more readily visible in the polycythemic patient. The clinician should recognize that other factors may contribute to the appearance of cyanosis. Decreased tissue blood flow can cause so-called peripheral cyanosis whereby apparent cyanosis occurs even with a normal arterial oxygen content. This can be observed in patients with hypothermia decreased cardiac output or in some simply when placed in the supine or Trendelenburg position. Ambient lighting differences can affect how easily cyanosis is detected and certain drugs . benzocaine can cause the appearance of cyanosis also with a normal arterial oxygen content. Arterial Blood Gases Arterial blood gas monitoring is the gold standard for monitoring blood oxygen tension. Although invasive it has the advantage of also giving information about carbon dioxide and acid-base status many contemporary point-of-care bloodgas analyzers can also deliver other blood chemistry results. However it is important to recognize that even with a normal PaO2 and SaO2 tissue .