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ISPN复习要点提示 05 酸碱平衡
日期：2020-03-16 20:04:43
Tips On How To Review For ISPN Examinations
05
Acid-Base Balance
酸碱平衡
Acid-Base balance is important because it is involved in almost every step of nursing practice贯穿于护理执业的全过程, including assessment before and after treatment. In reviewing the acid-base balance, you may first understand the concepts included in assessment of acid-base balance and the description and cause of each imbalance. You may correlate the pathophysiology with each cause 将病理生理与失调原因关联and note the assessment findings related to each disorder and treatment associated with the clinical manifestations 注重评估所见. An integration of the knowledge of fluid and electrolytes may benefit you a lot in reviewing acid-base balance. Remember, maintenance of a patent airway is a priority; the safety precautions should always be initiated; and seizure precaution is needed.
Key points of this topic will include: basic concepts relating to acid-base balance and imbalance酸碱平衡和失调基本概念; acidosis vs. alkalosis 酸中毒与碱中毒; respiratory vs. metabolic 呼吸性还是代谢性; compensated vs. uncompensated 代偿或失代偿; and arterial blood gas 动脉血气. They will be discussed in three parts: (1) Basic concepts relating to acid-base balance and imbalance酸碱平衡与失调基本概念; (2) Types and Causes of Acid-Base Imbalances酸碱失调及原因; and (3) characteristics and Differentiation of Acid-Base Imbalances 酸碱失调的特征及鉴别.
Part 1
Basic concepts relating to acid-base balance and imbalance
酸碱平衡与失调基本概念
Basic concepts related to acid-base balance are important because they are the criteria for determining whether the client has suffered acid-base imbalance. They are the basis of nursing assessment, diagnosis, and intervention. Therefore, test-takers should be very familiar with these concepts. These basic concepts can be divided into three groups:
A. pH level酸碱度
B. ABG reference interval动脉血气参数参考范围
C. Regulatory Systems调节系统
A. pH level 酸碱度
1. pH (酸碱度potential of hydrogen, H+) is a numeric scale used to express the acidity or basicity of a solution. It is an indicator of acid-base balance or imbalance. Acidity, alkalinity, or neutrality is determined by the concentration of hydrogen ions (pH level).
2. Hydrogen ions (氢离子) circulate in the body in two forms. One is called volatile acid (挥发性酸). It can be exhaled through the lungs. Co2 is the main type of volatile acid. The other is called fixed acid (不挥发酸，固定酸). It is unvolatile and can’t not be exhaled by the lungs. It is excreted or reabsorbed through the renal regulatory system , HCO3− is the main type of fixed acid.
3. The pH scale ranges from 1 to 14. A neutral solution measures 7. The normal reference interval is between 7.35 and 7.45 (Fig. 5-1). If the pH value shifts out of these values, either lower than 7.35 or higher than 7.45, then it is abnormal. When the pH level falls below 7.35, it is acidic; when the pH level exceeds 7.45, it is basic. Pure water is neutral, at pH 7, being neither an acid nor a base.
FIGURE 5-1 pH scale
B. ABG reference interval动脉血气参数参考范围
1. Arterial blood gas (ABG,动脉血气) is a measurement reflecting acid-base balance or imbalance. It tells you whether the client’s acid-base level is normal or abnormal and balanced or imbalanced.
2. Arterial blood gas consists of levels of pH (氢离子浓度), Paco2 (partial pressure of carbon dioxide 二氧化碳分压), HCO3- (bicarbonate碳酸氢盐), and Po2 (partial pressure of oxygen氧分压). Alterations in ABG results, either decreased or increased, may mean that the acid-base levels have gone abnormal. Acid-base imbalance may have occurred.
3. The normal ABG values are as follows:
pH -- 7.35-7.45
Paco2 -- 35-45 mm Hg
HCO3- -- 22-27 mEq/L
Po2 80-100 mm Hg
4. In reviewing ABG contents, there is something that you may pay special attention to. That is, the factors that may affect the accuracy of the results, such as changes in O2 settings, suctioning within the past 20 minutes, and client’s activities.评估可能影响结果正确度的因素，如O2环境的变化，过去20分钟内是否抽吸及患者活动。These factors may temporarily impact the results of ABG tests and lead to the fluctuation of ABG levels. Sometimes, these fluctuations may not actually reflect the changes in client’s condition.
C. Regulatory Systems调节系统
The regulation of acid-base balance is actually the regulation of hydrogen ions. Generally, there are three major homeostatic regulators of hydrogen ions: chemical buffer systems (化学缓冲系统调节); pulmonary mechanisms (呼吸机制调节), and renal mechanisms (肾排泄机制调节). The acid-base balance is regulated and maintained through these three mechanisms.
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