Although Hyponatremia is a lab finding, based upon various clinical situations, this can also be a patient presentation. When a clinician is directly looking at an abnormal lab result, the clinician can start the evaluation process in a reverse order. Since serum sodium is often reported as a part of a metabolic panel, additional lab results, such as serum osmolality and serum potassium, should be available for evaluating hyponatremia. For this reason, this clinical mind map is organized based upon three types of hyponatremias, which are isotonic, hypertonic, and hypotonic. Hypotonic is further divided into three types, which are hypovolemic, euvolemic and hypervolemic. This arrangement seems to be leading to a reverse evaluation process, which is different from the majority of the clinical mind maps contained in this book. The reverse process is first reviewing the labs, then looking at physical exam findings, and finally taking a patient history or gathering past medical history-related information. However, a clinician can still apply the Epi-logical approach for diagnostic reasoning while following this clinical mind map.

Probable diagnoses are displayed as differentials on the lower part of the clinical mind map. Urgent and emergent situations should be addressed by reviewing the patient’s vitals, appearance, and mental status. Based upon the patient’s clinical status, almost any diagnosis can cause an urgent/emergent situation. An urgent/emergent situation does not necessarily lead to any particular life-threatening diagnoses because all diagnoses are potentially life-threatening. However, the geriatric population and patients with several co-morbidities, in whom the body’s compensatory mechanisms may not be robust, are at particular risk for rapid deterioration. In addition, a rapid and significant drop in serum sodium is more likely to lead to clinical decompensation than a slow and mild drop. Since in most situations, information about the patient’s trend of serum sodium level may not be available, a clinician may have difficulty in making a determination as to whether the reduction in sodium is rapid or gradual. Therefore, this determinant is not included in the clinical mind map to distinguish between urgent/emergent and non-urgent/emergent situations.

Weighing and removing anchor bias depends on a physical exam, information gathered from the patient, and relevant medical records. Typically, arriving at a final diagnosis in a patient with hyponatremia is simple and does not pose much of a cognitive challenge.

 

A few tips to remember the differentials:

1. Isotonic causes are not true hyponatremic states.

2. Hypertonic causes are usually easily identifiable.

3. Among hypotonic causes,

   1. Hypovolemic states are all those states in which the body loses fluid and the same states can result in hypernatremia depending upon how fast sodium loss occurs in relation to fluid loss.

   2. Hypervolemic states are all those states in which fluid can be retained in third space and similar states can give rise to hypernatremia.

   3. Euvolemic states, which usually are of significant clinical interest, can be memorized with the help of the mnemonic Psycho HASS Beer.