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High prevalence of hypokalemia in acute psychiatric inpatients
Available online at www.sciencedirect.com
General Hospital Psychiatry 31 (2009) 262 – 265
High prevalence of hypokalemia in acute psychiatric inpatients Marco Ho-bun Lam, M.R.C.Psych., F.H.K.A.M., Steven Wai-ho Chau, M.B.B.S., Yun-kwok Wing, F.R.C.Psych., F.H.K.A.M.⁎ Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR Received 2 January 2009; accepted 20 February 2009
Abstract Background: Hypokalemia is an easily identifiable, clinically important but commonly neglected condition in psychiatric patients. This study intended to examine the prevalence of hypokalemia and its clinical correlates in acute psychiatric inpatients. Method: This retrospective study was conducted over a 6 month period in 2008. The case notes, computerized records and laboratory results of all patients who were consecutively admitted to the acute psychiatric wards in a University-affiliated regional psychiatric unit were studied. Result: Three hundred forty-seven patients out of 440 admissions were studied. Hypokalemia, as defined by serum potassium level of less than 3.5 mmol/L, was found in 20.5% of patients with a higher prevalence in psychotic patients (27.7%). The mean potassium level of psychotic patients was lower than that of the overall study population (3.72 vs. 3.81 mmol/L, Pb.05). White cell counts among the hypokalemic patients were higher than those without hypokalemia (7.8 vs. 7.1×109/L, P=.02). Conclusion: Hypokalemia was common among acute psychiatric inpatients. Both agitation and the use of antipsychotics were postulated to contribute to the high prevalence of hypokalemia among acutely ill psychiatric patients. © 2009 Elsevier Inc. All rights reserved.
1. Introduction Previous studies found that nearly half of psychiatric patients suffered from various medical diseases [1] but almost one third of the physical conditions were missed, inadequately diagnosed, investigated or managed [2]. Hypokalemia, an easily identifiable and clinically important condition in clinical settings, received little attention from researchers worldwide. Although poor oral intake and drug effects [3] have been implicated as possible etiologies of hypokalemia, detail measurement of nutritional status, psychiatric diagnoses and the choice of psychotropic medications were not closely examined in past studies [4]. Not only is hypokalemia associated with numerous cardiac and neuromuscular complications, but its effect on mental function may also mimic or aggravate psychiatric disturbances [5]. Severe hypokalemia, especially with the combination of arrhythmogenic medications, may lead to potential lethal cardiovascular complications including cardiac arrest and sudden death [6].
⁎ Corresponding author. Tel.: +852 26367748; fax: +852 26475321. E-mail address: [email protected] (Y. Wing). 0163-8343/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.genhosppsych.2009.02.007
As the mechanism of hypokalemia in psychiatric population was not well understood, this study aimed to investigate the prevalence and clinical correlates of hypokalemia in acute psychiatric inpatients.
2. Method The case notes and computerized records of all patients who were consecutively admitted to the acute psychiatric wards in a University-affiliated regional psychiatric unit, from February 1 to August 1, 2008, were studied. The following variables of the subjects were taken into account: sociodemographics, duration of hospital stay, principal psychiatric diagnoses by International Statistical Classification of Diseases, 10th Revision, comorbid physical conditions as well as blood results. The types of psychotropic and nonpsychotropic medications usage before admission were examined, but the equivalent dosages were not calculated as a significant proportion of the admitted patients had relapse of psychiatric illnesses related to poor drug adherence. The following three categories of psychiatric diagnosis were defined. Psychotic spectrum disorders
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265
included schizophrenia, schizoaffective disorder, acute transient psychotic disorder, psychotic disorder unspecified, organic psychotic disorder and delusional disorder. Bipolar spectrum disorders covered manic episode, hypomanic episode, bipolar I and bipolar II illness. Depressive spectrum disorders included unipolar major depressive episode, recurrent depression and dysthymia. In our laboratory, those subjects with serum potassium level of less than 3.5 mmol/L were classified to have hypokalemia. Besides, the following laboratory results were of particular interest to the study: 1. Renal function as reflected by serum creatinine level. 2. Nutritional status as reflected by body mass index (BMI), serum urea and albumin levels. 3. White cell count (WCC) was also recorded as previous study suggested that it might also be raised in agitated patients [7]. Patients who did not receive blood checking within the first 3 days of admission to the psychiatric wards and were known to suffer from medical illness including patients with delirium that would directly affect the potassium level, with the exception of hypertension and use of antihypertensive drugs, were excluded. As agitated mental state has been suggested to be correlated with the presence of hypokalemia in psychiatric patients [4], a few clinical markers that might suggest the presence of agitation in our patients, such as the need for close observation as judged by the attending psychiatrists, use of physical restraints and intramuscular tranquilization, were also studied. The study was approved by the institutional research ethics committee. 2.1. Statistics Categorical variables were analyzed by the chi-square test, while continuous variables were analyzed by Student's t test and one-way analysis of variance with post hoc test. The statistical significance level was set at Pb.05. 3. Results A total of 440 admissions were recorded in the study period. Two hundred thirty-four patients (53.2%) were admitted through the casualty department, 116 (26.4%) via outpatient clinic, and 90 (20.5%) were transferred from nonpsychiatric wards. Among them, 86 patients (19.5%) had no previous psychiatric contact. Ninety-three entries were voided, as 87 subjects lacked relevant laboratory investigations and six subjects suffered from major medical diseases including prominent renal failure, Cushing disease and delirium (n=1). It yielded a participation rate of 79%. About 87% of blood checking was taken within first 24 h after admission. The study population constituted of 126 male and 221 female patients with a mean age of 40.1 years (S.D., 12.2). One hundred thirty cases (37.4%) had psychotic
263
spectrum disorders; 47 (13.5%), bipolar spectrum disorders; 102 (29.4%), depressive spectrum disorders and 68 (19.6%), other cases. Among them, 45 patients (13%) suffered from hypertension in which 14 patients received antihypertensive diuretic medication. Nonetheless, possibly due to chronic potassium replacement therapy or nonadherence issue, both history of hypertension and the use of diuretics did not significantly influence the potassium levels. Seventy-one patients (20.5%) had potassium level less than 3.5 mmol/L, but only seven (2% of case series or 10% of hypokalemic cases) subjects had prominent hypokalemia with the level lower than 3.0 mmol/L. Thirty six (27.7%) psychotic spectrum disorders subjects were found to have hypokalemia, and the prevalence was higher than that of overall study population (Table 1) and other psychiatric disorders (Pb.05). Similarly, the mean potassium level of psychotic spectrum patients was lower than that of the overall study population (3.72 vs. 3.81 mmol/L, P=.003). None of the patients were reported to have major cardiac problem. Patients with serum potassium level below 3.2 mmol/L were supplemented with oral potassium medication, and their potassium levels were normalized in the next blood checking. However, there were no differences of potassium level among the bipolar spectrum disorder subjects, depressive spectrum disorder subjects and the overall study population. The psychotic spectrum disorders subjects did not differ from the study population in gender ratio, duration of hospital stay, presence of hypertension, BMI, serum urea, creatinine, albumin, WCC levels and clinical markers of agitation. Nevertheless, 79% psychotic spectrum patients and 34% nonpsychotic spectrum patients were receiving antipsychotics. Besides, psychotic spectrum disorder patients tended to be slightly younger (36.4 vs. 39.9, Pb.001), while depressive patients appeared to be older (45.6 vs. 39.9, Pb.001). In order to examine the clinical correlates of hypokalemia, the study also compared sociodemographic variables, laboratory results and clinical markers of agitation between hypokalemic and non-hypokalemic groups. No statistical significances were found except that the white well count was higher in hypokalemic group (7.8 vs. 7.1×109/L, P=.02).
Table 1 Demographics and spectrums of psychiatric illness and hypokalemia Cases with hypokalemia (prevalence) Sample size Age Gender Psychiatric illness
NS, nonsignificant.
347 40.1 (S.D.=12.2) Male Female Psychotic spectrum Bipolar spectrum Depressive spectrum Others
P
71 (20.5%) 126 221 130 47 102 68
36 4 20 13
(27.7%) (8.5%) (19.6%) (19.1%)
.03 NS NS NS
264
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265
4. Discussion Previous study found that hypokalemia was common in medical inpatient settings [7]. About 20% of stroke and 10% of myocardial infarction patients suffered from hypokalemia [8]. The considerable prevalence of hypokalemia was understandable given the fact that these medical conditions were commonly associated with various comorbidities and the use of diuretics and haematinics that could lead to excessive potassium loss [7]. Surprisingly, the prevalence of hypokalemia (20%) in our acute psychiatric inpatients was very similar, if not higher, to that of medical inpatients. In this regard, only one previous study found that one third of schizophrenic patients had hypokalemia [9]. Thus, our study added to the limited database that hypokalemia was indeed highly prevalent among acute psychiatric patients. The etiologies of hypokalemia were complex. The level of serum potassium depended on the balance between oral intake, renal and gastrointestinal losses as well as balance and shifting between extra and intra-cellular compartments [6]. Although previous study found that 7.6% psychiatric patients had nutritional problem [10], inadequate dietary potassium intake was relatively rare unless daily potassium intake was less than one gram (25mmol) [11-12]. Besides, this study did not support the assertion that hypokalemia was due to gross dietary inadequacy as the corroborative markers for nutritional status such as BMI, serum urea, creatinine and albumin were all normal. Alternatively, diuretics use, which commonly caused hypokalemia by promoting renal potassium loss [13], did not affect the potassium level of the study population. Therefore, there must be other mechanisms involved in the causation of hypokalemia in psychiatric patients. This study found that it was the psychotic spectrum subjects, rather than those with bipolar and depressive disorders, that would more likely develop hypokalemia. The exact mechanism was uncertain but both antipsychotic usage and the presence of agitation in psychiatric patients have been postulated to modulate potassium balance and level [4,14,15]. Thus, the lower prevalence of antipsychotic usage in nonpsychotic spectrum patients might partially explain why their prevalence of hypokalemia was lower. Antipsychotics were found to block the potassium efflux channel and prohibit intracellular potassium from shifting into the extracelullar compartment. They have been reported to cause hypokalemia when being taken in excess or overdose [14,15]. Nonetheless, clinical use of antipsychotics rarely leads to overt hypokalemia [16], but further study on the dosage and types of antipsychotics will be needed. Similarly, agitation was postulated to stimulate the surge of serum adrenaline, which, in turn, via the over-stimulation of betaadrenergic receptors, caused influx of serum potassium into cells [4,17]. Extreme emotion such as agitation, possibly by stimulating stress hormones especially the cortisol system, was also found to increase the white cell count, as seen in our patients with hypokalemia [18]. Although the indirect
markers of agitation as reflected by the need of physical restraint, chemical tranquilization and close observation failed to demonstrate any relationship with hypokalemia and white cell count, future prospective study on careful measurement and monitoring of the mental state of acute psychiatric patients is needed. In this regard, further research is needed to examine the potential of adopting serum potassium level as an early indicator of agitation in psychiatric patients. The impact of hypokalemia on the morbidity of psychiatric patients is considerable [19]. Mild hypokalemia is usually well tolerated in healthy people, but this study found that about 10% of hypokalemic cases had prominent low level with the lowest one having serum potassium level of 2.5 mmol/L. Such low potassium level might exacerbate the QTc prolongation effect of psychotropic medications, which, in turn, may predispose to cardiac arrhythmia and even sudden death [20]. Moreover, metabolic syndromes are pervasive among psychiatric patients [21], who will be prone to develop cardiac ischemia, heart failure or left ventricular hypertrophy. In these patients, even mild to moderate hypokalemia may increase the likelihood of cardiovascular complications [22]. As more than one fifth of acute psychiatric inpatients had hypokalemia upon admission, systemic and detailed examination and routine laboratory investigation including electrocardiograms are necessary and mandatory for all psychiatric inpatients to safeguard their physical and mental health. Supplemental potassium administration should be commenced as soon as possible. In addition, arrhythmogenic psychotropics should be used with caution as hypokalemia may augment their arrhythmogenic effect. There were some limitations in this study including retrospective nature, lack of structured interview and psychometric assessment of the subjects. Nonetheless, the common occurrence of hypokalemia in acute psychiatric inpatients should alert all clinicians to the importance of holistic care of psychiatric patients.
References [1] Williams E, Shepherd S. Medical clearance of psychiatric patients. Emerg Med Clin North Am 2000;18:185–98. [2] Karasu TB, Waltzman SA, Lindenmayer JP, Buckley PJ. The medical care of patients with psychiatric illness. Hosp Community Psychiatry 1980;31:463–72. [3] Greenfeld D, Mickley D, Quinlan DM, Roloff P. Detection and importance of laxative use in adolescents with anorexia nervosa. Am J Psychiatry 1995;152:60–3. [4] Hatta K, Takahashia T, Nakamurab H, Yamashiroa H, Asukaic N, Yonezawaa Y. Hypokalemia and agitation in acute psychotic patients. Psychiatry Res 1999;86:185–8. [5] Riggs JE. Neurologic manifestations of electrolyte disturbances. Neurol Clin 2002;20:227–39. [6] Gennari FJ. Hypokalemia. N Engl J Med 1998;339:451–8. [7] Paice BJ, Paterson KR, Onyanga-Omara F, Donnelly T, Gray JMB, Lawson DH. Record linkage study of hypokalaemia in hospitalized patients. Postgrad Med J 1986;62:187–91.
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265 [8] Gariballa SE, Robinson TG, Fotherby MD. Hypokalemia and potassium excretion in stroke patients. J Am Geriatr Soc 1997;45: 454–8. [9] Hatta K, Takahashi T, Nakamura H, Yamashiro H, Endo H, Fujii S, et al. Abnormal physiological conditions in acute schizophrenic patients on emergency admission: dehydration, hypokalemia, leukocytosis and elevated serum muscle enzymes. Eur Arch Psychiatry Clin Neurosci 1998;248:180–8. [10] Cheung KL, Kong BM, Chan EL, Ku PS. The prevalence and risk factors of protein-energy malnutrition in three different institutions for elderly Chinese in Hong Kong. J HK Geriatr Soc 2000;10:5–9. [11] Hernandez RE, Schambelan M, Cogan MG, Colman J, Morris Jr RC, Sebastian A. Dietary NaCl determines the severity of potassium depletion-induced metabolic alkalosis. Kidney Int 1987; 31:1356–67. [12] Squires RD, Huth EJ. Experimental potassium depletion in normal human subjects. I. Relation of ionic intakes to the renal conservation of potassium. J Clin Invest 1959;38:1134–48. [13] Hoes AW, Grobbee DE, Peet TM, Lubsen J. Do non-potassium-sparing diuretics increase the risk of sudden cardiac death in hypertensive patients? Recent evidence. Drugs 1994;47:711–33.
265
[14] Lin YC, Chen HZ, Chang TJ, Lane HY. Hypokalemia following rapid titration of quetiapine treatment. J Clin Psychiatry 2008;69:165–6. [15] Malik AR, Wolf PK, Ravasia S. Hypokalemia from risperidone and quetiapine overdose. Can J Psychiatry 2005;50:76. [16] Shader RI, Greenblatt DJ. Potassium, antipsychotic agents, arrhythmias, and sudden death. J Clin Psychopharmacol 1998;18(6):427–8. [17] Brown MJ, Brown DC, Murphy MB. Hypokalemia from beta2receptor stimulation by circulating epinephrine. N Engl J Med 1983;8: 1414–9. [18] Hennig J, Nettera P, Voigt KH. Cortisol mediates redistribution of CD8+ but not of CD56+ cells after the psychological stress of public speaking. Psychoneuroendocrinology 2001;26:673–87. [19] Aunsholt NA. Prolonged Q-T interval and hypokalemia caused by haloperidol. Acta Psychiatr Scand 2007;74:411–2. [20] Zareba W, Lin DA. Antipsychotic drugs and QT interval prolongation. Psychiatr Q 2003;74:291–306. [21] Heiskanen T, Niskanen L, Lyytikäinen R, Saarinen PI, Hintikka J. Metabolic syndrome in patients with schizophrenia. J Clin Psychiatry 2003;64:575–9. [22] Schulman M, Narins RG. Hypokalemia and cardiovascular disease. Am J Cardiol 1990;65:4E–9E.
General Hospital Psychiatry 31 (2009) 262 – 265
High prevalence of hypokalemia in acute psychiatric inpatients Marco Ho-bun Lam, M.R.C.Psych., F.H.K.A.M., Steven Wai-ho Chau, M.B.B.S., Yun-kwok Wing, F.R.C.Psych., F.H.K.A.M.⁎ Department of Psychiatry, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR Received 2 January 2009; accepted 20 February 2009
Abstract Background: Hypokalemia is an easily identifiable, clinically important but commonly neglected condition in psychiatric patients. This study intended to examine the prevalence of hypokalemia and its clinical correlates in acute psychiatric inpatients. Method: This retrospective study was conducted over a 6 month period in 2008. The case notes, computerized records and laboratory results of all patients who were consecutively admitted to the acute psychiatric wards in a University-affiliated regional psychiatric unit were studied. Result: Three hundred forty-seven patients out of 440 admissions were studied. Hypokalemia, as defined by serum potassium level of less than 3.5 mmol/L, was found in 20.5% of patients with a higher prevalence in psychotic patients (27.7%). The mean potassium level of psychotic patients was lower than that of the overall study population (3.72 vs. 3.81 mmol/L, Pb.05). White cell counts among the hypokalemic patients were higher than those without hypokalemia (7.8 vs. 7.1×109/L, P=.02). Conclusion: Hypokalemia was common among acute psychiatric inpatients. Both agitation and the use of antipsychotics were postulated to contribute to the high prevalence of hypokalemia among acutely ill psychiatric patients. © 2009 Elsevier Inc. All rights reserved.
1. Introduction Previous studies found that nearly half of psychiatric patients suffered from various medical diseases [1] but almost one third of the physical conditions were missed, inadequately diagnosed, investigated or managed [2]. Hypokalemia, an easily identifiable and clinically important condition in clinical settings, received little attention from researchers worldwide. Although poor oral intake and drug effects [3] have been implicated as possible etiologies of hypokalemia, detail measurement of nutritional status, psychiatric diagnoses and the choice of psychotropic medications were not closely examined in past studies [4]. Not only is hypokalemia associated with numerous cardiac and neuromuscular complications, but its effect on mental function may also mimic or aggravate psychiatric disturbances [5]. Severe hypokalemia, especially with the combination of arrhythmogenic medications, may lead to potential lethal cardiovascular complications including cardiac arrest and sudden death [6].
⁎ Corresponding author. Tel.: +852 26367748; fax: +852 26475321. E-mail address: [email protected] (Y. Wing). 0163-8343/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.genhosppsych.2009.02.007
As the mechanism of hypokalemia in psychiatric population was not well understood, this study aimed to investigate the prevalence and clinical correlates of hypokalemia in acute psychiatric inpatients.
2. Method The case notes and computerized records of all patients who were consecutively admitted to the acute psychiatric wards in a University-affiliated regional psychiatric unit, from February 1 to August 1, 2008, were studied. The following variables of the subjects were taken into account: sociodemographics, duration of hospital stay, principal psychiatric diagnoses by International Statistical Classification of Diseases, 10th Revision, comorbid physical conditions as well as blood results. The types of psychotropic and nonpsychotropic medications usage before admission were examined, but the equivalent dosages were not calculated as a significant proportion of the admitted patients had relapse of psychiatric illnesses related to poor drug adherence. The following three categories of psychiatric diagnosis were defined. Psychotic spectrum disorders
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265
included schizophrenia, schizoaffective disorder, acute transient psychotic disorder, psychotic disorder unspecified, organic psychotic disorder and delusional disorder. Bipolar spectrum disorders covered manic episode, hypomanic episode, bipolar I and bipolar II illness. Depressive spectrum disorders included unipolar major depressive episode, recurrent depression and dysthymia. In our laboratory, those subjects with serum potassium level of less than 3.5 mmol/L were classified to have hypokalemia. Besides, the following laboratory results were of particular interest to the study: 1. Renal function as reflected by serum creatinine level. 2. Nutritional status as reflected by body mass index (BMI), serum urea and albumin levels. 3. White cell count (WCC) was also recorded as previous study suggested that it might also be raised in agitated patients [7]. Patients who did not receive blood checking within the first 3 days of admission to the psychiatric wards and were known to suffer from medical illness including patients with delirium that would directly affect the potassium level, with the exception of hypertension and use of antihypertensive drugs, were excluded. As agitated mental state has been suggested to be correlated with the presence of hypokalemia in psychiatric patients [4], a few clinical markers that might suggest the presence of agitation in our patients, such as the need for close observation as judged by the attending psychiatrists, use of physical restraints and intramuscular tranquilization, were also studied. The study was approved by the institutional research ethics committee. 2.1. Statistics Categorical variables were analyzed by the chi-square test, while continuous variables were analyzed by Student's t test and one-way analysis of variance with post hoc test. The statistical significance level was set at Pb.05. 3. Results A total of 440 admissions were recorded in the study period. Two hundred thirty-four patients (53.2%) were admitted through the casualty department, 116 (26.4%) via outpatient clinic, and 90 (20.5%) were transferred from nonpsychiatric wards. Among them, 86 patients (19.5%) had no previous psychiatric contact. Ninety-three entries were voided, as 87 subjects lacked relevant laboratory investigations and six subjects suffered from major medical diseases including prominent renal failure, Cushing disease and delirium (n=1). It yielded a participation rate of 79%. About 87% of blood checking was taken within first 24 h after admission. The study population constituted of 126 male and 221 female patients with a mean age of 40.1 years (S.D., 12.2). One hundred thirty cases (37.4%) had psychotic
263
spectrum disorders; 47 (13.5%), bipolar spectrum disorders; 102 (29.4%), depressive spectrum disorders and 68 (19.6%), other cases. Among them, 45 patients (13%) suffered from hypertension in which 14 patients received antihypertensive diuretic medication. Nonetheless, possibly due to chronic potassium replacement therapy or nonadherence issue, both history of hypertension and the use of diuretics did not significantly influence the potassium levels. Seventy-one patients (20.5%) had potassium level less than 3.5 mmol/L, but only seven (2% of case series or 10% of hypokalemic cases) subjects had prominent hypokalemia with the level lower than 3.0 mmol/L. Thirty six (27.7%) psychotic spectrum disorders subjects were found to have hypokalemia, and the prevalence was higher than that of overall study population (Table 1) and other psychiatric disorders (Pb.05). Similarly, the mean potassium level of psychotic spectrum patients was lower than that of the overall study population (3.72 vs. 3.81 mmol/L, P=.003). None of the patients were reported to have major cardiac problem. Patients with serum potassium level below 3.2 mmol/L were supplemented with oral potassium medication, and their potassium levels were normalized in the next blood checking. However, there were no differences of potassium level among the bipolar spectrum disorder subjects, depressive spectrum disorder subjects and the overall study population. The psychotic spectrum disorders subjects did not differ from the study population in gender ratio, duration of hospital stay, presence of hypertension, BMI, serum urea, creatinine, albumin, WCC levels and clinical markers of agitation. Nevertheless, 79% psychotic spectrum patients and 34% nonpsychotic spectrum patients were receiving antipsychotics. Besides, psychotic spectrum disorder patients tended to be slightly younger (36.4 vs. 39.9, Pb.001), while depressive patients appeared to be older (45.6 vs. 39.9, Pb.001). In order to examine the clinical correlates of hypokalemia, the study also compared sociodemographic variables, laboratory results and clinical markers of agitation between hypokalemic and non-hypokalemic groups. No statistical significances were found except that the white well count was higher in hypokalemic group (7.8 vs. 7.1×109/L, P=.02).
Table 1 Demographics and spectrums of psychiatric illness and hypokalemia Cases with hypokalemia (prevalence) Sample size Age Gender Psychiatric illness
NS, nonsignificant.
347 40.1 (S.D.=12.2) Male Female Psychotic spectrum Bipolar spectrum Depressive spectrum Others
P
71 (20.5%) 126 221 130 47 102 68
36 4 20 13
(27.7%) (8.5%) (19.6%) (19.1%)
.03 NS NS NS
264
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265
4. Discussion Previous study found that hypokalemia was common in medical inpatient settings [7]. About 20% of stroke and 10% of myocardial infarction patients suffered from hypokalemia [8]. The considerable prevalence of hypokalemia was understandable given the fact that these medical conditions were commonly associated with various comorbidities and the use of diuretics and haematinics that could lead to excessive potassium loss [7]. Surprisingly, the prevalence of hypokalemia (20%) in our acute psychiatric inpatients was very similar, if not higher, to that of medical inpatients. In this regard, only one previous study found that one third of schizophrenic patients had hypokalemia [9]. Thus, our study added to the limited database that hypokalemia was indeed highly prevalent among acute psychiatric patients. The etiologies of hypokalemia were complex. The level of serum potassium depended on the balance between oral intake, renal and gastrointestinal losses as well as balance and shifting between extra and intra-cellular compartments [6]. Although previous study found that 7.6% psychiatric patients had nutritional problem [10], inadequate dietary potassium intake was relatively rare unless daily potassium intake was less than one gram (25mmol) [11-12]. Besides, this study did not support the assertion that hypokalemia was due to gross dietary inadequacy as the corroborative markers for nutritional status such as BMI, serum urea, creatinine and albumin were all normal. Alternatively, diuretics use, which commonly caused hypokalemia by promoting renal potassium loss [13], did not affect the potassium level of the study population. Therefore, there must be other mechanisms involved in the causation of hypokalemia in psychiatric patients. This study found that it was the psychotic spectrum subjects, rather than those with bipolar and depressive disorders, that would more likely develop hypokalemia. The exact mechanism was uncertain but both antipsychotic usage and the presence of agitation in psychiatric patients have been postulated to modulate potassium balance and level [4,14,15]. Thus, the lower prevalence of antipsychotic usage in nonpsychotic spectrum patients might partially explain why their prevalence of hypokalemia was lower. Antipsychotics were found to block the potassium efflux channel and prohibit intracellular potassium from shifting into the extracelullar compartment. They have been reported to cause hypokalemia when being taken in excess or overdose [14,15]. Nonetheless, clinical use of antipsychotics rarely leads to overt hypokalemia [16], but further study on the dosage and types of antipsychotics will be needed. Similarly, agitation was postulated to stimulate the surge of serum adrenaline, which, in turn, via the over-stimulation of betaadrenergic receptors, caused influx of serum potassium into cells [4,17]. Extreme emotion such as agitation, possibly by stimulating stress hormones especially the cortisol system, was also found to increase the white cell count, as seen in our patients with hypokalemia [18]. Although the indirect
markers of agitation as reflected by the need of physical restraint, chemical tranquilization and close observation failed to demonstrate any relationship with hypokalemia and white cell count, future prospective study on careful measurement and monitoring of the mental state of acute psychiatric patients is needed. In this regard, further research is needed to examine the potential of adopting serum potassium level as an early indicator of agitation in psychiatric patients. The impact of hypokalemia on the morbidity of psychiatric patients is considerable [19]. Mild hypokalemia is usually well tolerated in healthy people, but this study found that about 10% of hypokalemic cases had prominent low level with the lowest one having serum potassium level of 2.5 mmol/L. Such low potassium level might exacerbate the QTc prolongation effect of psychotropic medications, which, in turn, may predispose to cardiac arrhythmia and even sudden death [20]. Moreover, metabolic syndromes are pervasive among psychiatric patients [21], who will be prone to develop cardiac ischemia, heart failure or left ventricular hypertrophy. In these patients, even mild to moderate hypokalemia may increase the likelihood of cardiovascular complications [22]. As more than one fifth of acute psychiatric inpatients had hypokalemia upon admission, systemic and detailed examination and routine laboratory investigation including electrocardiograms are necessary and mandatory for all psychiatric inpatients to safeguard their physical and mental health. Supplemental potassium administration should be commenced as soon as possible. In addition, arrhythmogenic psychotropics should be used with caution as hypokalemia may augment their arrhythmogenic effect. There were some limitations in this study including retrospective nature, lack of structured interview and psychometric assessment of the subjects. Nonetheless, the common occurrence of hypokalemia in acute psychiatric inpatients should alert all clinicians to the importance of holistic care of psychiatric patients.
References [1] Williams E, Shepherd S. Medical clearance of psychiatric patients. Emerg Med Clin North Am 2000;18:185–98. [2] Karasu TB, Waltzman SA, Lindenmayer JP, Buckley PJ. The medical care of patients with psychiatric illness. Hosp Community Psychiatry 1980;31:463–72. [3] Greenfeld D, Mickley D, Quinlan DM, Roloff P. Detection and importance of laxative use in adolescents with anorexia nervosa. Am J Psychiatry 1995;152:60–3. [4] Hatta K, Takahashia T, Nakamurab H, Yamashiroa H, Asukaic N, Yonezawaa Y. Hypokalemia and agitation in acute psychotic patients. Psychiatry Res 1999;86:185–8. [5] Riggs JE. Neurologic manifestations of electrolyte disturbances. Neurol Clin 2002;20:227–39. [6] Gennari FJ. Hypokalemia. N Engl J Med 1998;339:451–8. [7] Paice BJ, Paterson KR, Onyanga-Omara F, Donnelly T, Gray JMB, Lawson DH. Record linkage study of hypokalaemia in hospitalized patients. Postgrad Med J 1986;62:187–91.
M.H. Lam et al. / General Hospital Psychiatry 31 (2009) 262–265 [8] Gariballa SE, Robinson TG, Fotherby MD. Hypokalemia and potassium excretion in stroke patients. J Am Geriatr Soc 1997;45: 454–8. [9] Hatta K, Takahashi T, Nakamura H, Yamashiro H, Endo H, Fujii S, et al. Abnormal physiological conditions in acute schizophrenic patients on emergency admission: dehydration, hypokalemia, leukocytosis and elevated serum muscle enzymes. Eur Arch Psychiatry Clin Neurosci 1998;248:180–8. [10] Cheung KL, Kong BM, Chan EL, Ku PS. The prevalence and risk factors of protein-energy malnutrition in three different institutions for elderly Chinese in Hong Kong. J HK Geriatr Soc 2000;10:5–9. [11] Hernandez RE, Schambelan M, Cogan MG, Colman J, Morris Jr RC, Sebastian A. Dietary NaCl determines the severity of potassium depletion-induced metabolic alkalosis. Kidney Int 1987; 31:1356–67. [12] Squires RD, Huth EJ. Experimental potassium depletion in normal human subjects. I. Relation of ionic intakes to the renal conservation of potassium. J Clin Invest 1959;38:1134–48. [13] Hoes AW, Grobbee DE, Peet TM, Lubsen J. Do non-potassium-sparing diuretics increase the risk of sudden cardiac death in hypertensive patients? Recent evidence. Drugs 1994;47:711–33.
265
[14] Lin YC, Chen HZ, Chang TJ, Lane HY. Hypokalemia following rapid titration of quetiapine treatment. J Clin Psychiatry 2008;69:165–6. [15] Malik AR, Wolf PK, Ravasia S. Hypokalemia from risperidone and quetiapine overdose. Can J Psychiatry 2005;50:76. [16] Shader RI, Greenblatt DJ. Potassium, antipsychotic agents, arrhythmias, and sudden death. J Clin Psychopharmacol 1998;18(6):427–8. [17] Brown MJ, Brown DC, Murphy MB. Hypokalemia from beta2receptor stimulation by circulating epinephrine. N Engl J Med 1983;8: 1414–9. [18] Hennig J, Nettera P, Voigt KH. Cortisol mediates redistribution of CD8+ but not of CD56+ cells after the psychological stress of public speaking. Psychoneuroendocrinology 2001;26:673–87. [19] Aunsholt NA. Prolonged Q-T interval and hypokalemia caused by haloperidol. Acta Psychiatr Scand 2007;74:411–2. [20] Zareba W, Lin DA. Antipsychotic drugs and QT interval prolongation. Psychiatr Q 2003;74:291–306. [21] Heiskanen T, Niskanen L, Lyytikäinen R, Saarinen PI, Hintikka J. Metabolic syndrome in patients with schizophrenia. J Clin Psychiatry 2003;64:575–9. [22] Schulman M, Narins RG. Hypokalemia and cardiovascular disease. Am J Cardiol 1990;65:4E–9E.