De leon with serum sodium
POLYDIPSIA IS A condition in which individuals consume excessive amounts of liquids, which places them at risk for life-threatening hyponatremia. The volume consumed ranges from 3,000 to 10,000 cubic centimeters (10 liters) of fluid per day (Verghese, De Leon, & Josiassen, 1996). The condition of polydipsia can be either chronic or episodic and symptoms range from mild to severe (De Leon, Verghese, Tracy, Josiassen, & Simpson, 1994). In some individuals, polydipsia is coupled with impaired water elimination resulting in water intoxication or acute hyponatremic episodes (serum sodium falls below 135 mEq/L; Shutty, Hundley, Leadbetter, Vieweg, & Hill, 1992). Polydipsia and subsequent hyponatremia can cause considerable morbidity and mortality rates as high 18.5% from water intoxication (Vieweg et al., 1985).
De Leon et al. (1994) performed a meta-analysis of nine epidemiological studies on polydipsia among inpatients of psychiatric facilities. They estimated that polydipsia (excluding medically induced cases) occurred in more than 20% of inpatients, and of these, approximately 5% developed episodic water intoxication and hyponatremia. De Leon et al. (1994) found that some patients with polydipsia failed to be diagnosed, and thus, polydipsia may not be reported in the medical history.
The prevalence of polydipsia has been recognized in select individuals with chronic mental illness residing in long-term inpatient psychiatric units. Patients diagnosed with schizophrenia are reported to be at highest risk for this condition (De Leon et al 2002; De Leon et al 1994; Patel 1994; Shutty et al 1992 and Vieweg et al 1994). However, to a lesser extent polydipsia has also been reported in patients with other diagnoses such as manic-depressive psychosis, psychosis with onset during childhood, psychotic depression, mental retardation, personality disorders, alcohol abuse, and organic mental syndromes (De Leon et al 1994; Hayfron-Benjamin et al 1996; Patel 1994 and Reynolds et al 2004).
Although inpatient psychiatric facilities are the most obvious setting where polydipsia is observed, nursing homes may also care for residents prone to develop polydipsia. Data from the 1995 National Nursing Home Survey show that mental disorders are the second most frequent primary diagnosis accounting for 17.1% of all elderly nursing home resident admissions (National Center for Health Statistics, 1997. Advance Data. Characteristics of elderly nursing home residents: Data from the 1995 national nursing home survey. Vital and Health Statistics of the Centers for Disease Control and Prevention Advance Date No. 289, July 2, 1997. .National Center for Health Statistics, 1997). Knowing that polydipsia is frequently underdiagnosed in inpatient psychiatric units, it is likely this condition would be present but undetected in nursing home residents. Furthermore, staff may be ill prepared to identify polydipsia.
Methods to identify polydipsia have been imprecise and typically focus on anecdotal staff reports of excessive drinking behaviors and polyuria. De Leon et al. (1994) concluded that no single measurement approach had yet been developed to identify this condition. More recently, a quality improvement project developed a protocol for diagnosing polydipsia when the condition was suspected by staff, but no criteria for initiating the screening/diagnostic process were provided (Visalli, 1997). This paper describes the scientific basis of the Polydipsia Screening Tool (© 2000 by Sheila Reynolds) and evaluates its psychometric properties.
Literature review
The exact mechanisms of polydipsia are unclear. Symptoms experienced by individuals with polydipsia seem to result directly from hyponatremia and the ensuing low serum osmolality. It is thought that hyponatremia develops as excessive fluid intake exceeds the normal excretory capacity of the kidneys, which results in impaired renal water excretion (Riggs, Dysken, Kim, & Opsahl, 1991). The severity of hyponatremic symptoms depends on the rate of development and the amount of sodium dilution (Porth, 2002). A drop in serum sodium of 10 mEq/L below the normal range of 135–148 mEq/L (i.e.,125 mEq/L), may not produce signs and symptoms if the onset is slow. However, a 10 mEq/L drop over a couple hours can produce recognizable symptoms (Verghese et al., 1996). Additionally, symptoms may not appear in some individuals with polydipsia until the serum sodium reaches120 mEq/L (Cosgray et al 1993 and Porth 2002). This phenomenon of “reset osmostat” occurs when the body physiologically fails to react to abnormal serum sodium (Cosgray et al., 1993). Thus, individuals who are insensitive to low serum sodium may not exhibit any symptoms or characteristics of polydipsia and the only exception would be a serum sodium value below 135 mEq/L.
Conversely, those who are sensitive to low serum sodium present with a cadre of symptoms and characteristics depending on how hyponatremic they are (Verghese et al 1996 and De Leon et al 1994). In less severe cases, the individual may exhibit deterioration in behavior. They may become angry, irritable, hostile, and disruptive; exhibit slurred speech; strike out at others; and be difficult to manage, overall (Boyd 1990 and May 1995). In severe cases, seizures, coma, and death may result when the level drops to 110 mEq/L or less (Porth 2002 and Shutty et al 1992).
Polydipsia screening tool
A 17-item symptom/characteristic, noninvasive Polydipsia Screening Tool (PST) was developed to be used by nursing personnel who provide care for at risk residents (Reynolds, 1999; Table 1). Reynolds observed that nursing home staff has limited knowledge in identifying residents at risk for polydipsia. The intent of this tool is to provide staff with the knowledge and ability to quickly and routinely screen residents at risk for polydipsia. The symptoms and characteristics reported in the literature have been synthesized and integrated into the tool. Criterion values selected were based on the literature.
Tags: Serum sodium