Monitoring of Oxygenation
Monitoring of Oxygenation
Clinical Assessment
Assessment of adequate oxygenation during administration of an anesthetic is essential. The skin color and appearance of blood in the surgical field are the simplest and most direct monitor of oxygenation and, although least quantitative, can and should
be assessed continuously. Cyanosis, a condition characterized by a blue color of the peripheral skin and mucous membranes which is symptom of lack of oxygen in the blood, is easily apparent when the concentration of deoxygenated hemoglobin in blood reaches 5 g/dl. This method of assessment requires that the operating room is adequately illuminated so that a portion of the patient, usually the nail beds or lips, is accessible for observation.
In Circuit Oxygen Concentration Monitor
To prevent the administration of a hypoxic gas mixture, the measurement of the concentration of oxygen in the inspired gas by an oxygen analyzer (if available). As discussed earlier in module II of anesthesia machine session, anesthesia machine contain a fail-safe device that automatically shut off the flow of nitrous oxide (if available) when the pressure of delivered oxygen falls below a certain level.
Pulse Oximetry
This monitor will display the patient's oxygen saturation and heart rate. The significance of pulse oximetry is it will often alert the anesthesia provider to hypoxia before detrimental physical signs are seen (Figure 2.1). If pulse oximetry is available it should be used during general anesthesia, regional anesthesia, and surgical cases in which sedative medications are used. Even during short surgical cases a pulse oximeter should be used. It takes only minutes of hypoxia for brain damage or death to occur. The pulse oximetry reading should be greater than 95% in normal patients when administering oxygen with your anesthetic (Table 2.2). Pulse oximetry should be monitored continuously. If supplemental oxygen is not available for use during the recovery period, the patient should maintain a reading of 90% or greater. Ensure that the patient has an adequate depth and rate of respirations.
A patient may exhibit an acceptable level of oxygenation by the pulse oximeter, but may be retaining carbon dioxide due to ineffective respiration. Hypercarbia can result in tachycardia, hypertension, decreased level of consciousness and acidosis. If the patient has shallow respirations or airway obstruction, a chin lift should be performed. If the patient's respirations remain shallow or continue to experience an obstruction, ventilation should be actively assisted or controlled. Many factors can interfere with its proper function including movement, vasoconstriction from cold (hypothermia), drugs, hypoperfusion (hypotension, irregular heart rhythm) and certain dyes. It is important to keep the patient warm for proper monitoring and treatment during surgery and in the postoperative period.
