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Severe Hypophosphataemia in Anorexia Nervosa A.K Postgrad Med J: first published as 10.1136/pgmj.70.829.825 on 1 November 1994. Downloaded from Postgrad Med J (1994) 70, 825 - 827 ) The Fellowship of Postgraduate Medicine, 1994 Severe hypophosphataemia in anorexia nervosa A.K. Cariem, E.R. Lemmer, M.G. Adams, T.A. Winter and S.J.D. O'Keefe Gastrointestinal Clinic, Department ofMedicine, Groote Schuur Hospital, E23, E-Floor, Observatory 7925, South Africa Summary: In addition to well-described acid-base and electrolyte disturbances, anorexia nervosa may be complicated by severe hypophosphataemia. We report a case of anorexia nervosa complicated by life-threatening hypophosphataemia manifesting as generalized muscle weakness and bulbar muscle dysfunction, resulting in an aspiration pneumonia and cardiorespiratory arrest. Introduction Anorexia nervosa is a complex psychosocial all present but depressed. A mild peripheral sen- disorder which, when severe, is associated with sory neuropathy was present. Chvostek's and well-described metabolic and endocrine distur- Trousseau's signs were negative. The only investi- bances. Reviews on acid-base and electrolyte gations available at the time revealed a haemo- disturbances that may accompany this disorder globin of 11.1 g/dl (reference range (RR) 11.6- have concentrated on hypochloraemic alkalosis 15.6), white cell count 3.5 x 109/l (RR 3.7-5.3), and depletion of sodium and potassium.' We wish platelets 68 x 109/l (RR 164-432), sodium 131 to draw attention to severe life-threatening hypo- mmol/l (RR 135-145), potassium 3.8 mmol/I (RR by copyright. phosphataemia which may also occur. 3.5-5.5), urea 8.9 mmol/l (RR 1.7-6.7), creatinine 70 ILmol/l (RR 75- 115). Red blood cell morphology was grossly abnormal with numerous anisocytes, Case report acanthocytes, microcytes with hypochromasia, spherocytes, and poikilocytes. Her chest X-ray A 21 year old woman with a 3-year history of revealed a small heart size and clear lung fields. The anorexia nervosa, characterized by severe dietary electrocardiogram was normal. restriction only, was admitted to the psychiatric In view of her clinical evidence of dehydration, ward 10 days earlier because of progressive loss of the patient was given 2 litres of a 0.9% sodium weight, feeling generally weak, and marked fatigue. chloride/5% dextrose solution over 12 hours. Over http://pmj.bmj.com/ Her premorbid weight was 56 kg whereas on the next 12 hours her generalized weakness admission it was 35 kg (body mass index of worsened, with the development of dysphagia and 12.5 kg/m2). She had severe anorexia, and was able nasal speech. Her gag reflex was weak. Arterial to manage only 500-700 ml of a liquid polymeric blood gases on room air revealed a pH 7.40 (RR preparation (Ensure@ Ross-Abbott Laboratories) 7.38-7.42), Paco2 4.2 kPa (RR 4.5-6.1), Pao2 and little else. 14.4 kPa (RR 10.0- 13.3), bicarbonate 24.9 mmol/l In view ofher inability to maintain nutrition and (RR 21-24). Serum biochemistry revealed the on September 30, 2021 by guest. Protected her progressive weakness, which now confined her following: sodium 126 mmol/l, potassium to bed, she was referred to the gastrointestinal unit 3.4 mmol/l, urea 1.4 mmol/l, creatinine 29 gAmol/l, for further management. On examination she was corrected calcium 2.05 mmol/l (RR 2.10-2.60), fully conscious, markedly emaciated and dehydrat- magnesium 0.67 mmol/l (RR 0.70-1.00), creatine ed with a blood pressure of 100/70 mmHg with a kinase 34 IU/I (RR 0-110). Liver function tests 40 mmHg systolic postural drop. Heart sounds were unremarkable. The most dramatic abnor- were normal and the chest clear. Abdominal mality was an extremely low serum inorganic examination was normal. She was mentally alert phosphate of 0.08 mmol/l (RR 0.70-1.00). and her speech normal. She had generalized weak- The severe hypophosphataemia was corrected ness (grade 3), which was more marked proximally. with 30 mmol ofphosphate administered as potas- Bulbar muscle function was normal. Reflexes were sium phosphate diluted in 500 ml normal saline infused intravenously over 12 hours. Although blood tests shortly after completion of the infusion Correspondence: A.K. Cariem, F.C.P.(S.A.). showed improvement in her biochemistry with Accepted: 9 March 1994 serum inorganic phosphate of 0.61 mmol/l, cor- Postgrad Med J: first published as 10.1136/pgmj.70.829.825 on 1 November 1994. Downloaded from 826 CLINICAL REPORTS rected calcium 1.90 mmol/l, magnesium 0.59 phosphate determination. However, more impor- mmol/l and potassium 3.5 mmol/l, her condition tantly, immediately prior to this blood sample further deteriorated with the development of res- being taken, she had received 2 litres of a dextrose- piratory distress and signs of a right lower lobe containing solution intravenously. The administra- pneumonia. She had a sudden cardiorespiratory tion of glucose results in the release of insulin, arrest and required ventilatory support for the next which promotes uptake of both glucose and phos- 10 days. Nerve conduction studies during this phorus into cells, thus causing a slight decline in period were normal and electromyography showed serum phosphorus levels. This phenomenon has features of a myopathic process. A normal serum been shown to be much more pronounced when inorganic phosphate level was maintained on con- glucose is administered to a starving individual.4 tinued oral supplementation. She was fully ambu- These three factors seem to be the most likely lant, although still weak, 4 days after being weaned explanation for the life-threatening hypophospha- off the ventilator. taemia that occurred in our patient. This illustrates well the brittle metabolic state of severely mal- nourished patients, which can easily be upset by Discussion unbalanced nutrient solutions such as glucose. The cause of her cardiorespiratory arrest is This patient, with a background of near starvation unclear but may have been due to aspiration due to anorexia nervosa, developed progressive secondary to a weak gag reflex, respiratory muscle weakness and became bedridden over a 10-day weakness, and/or cardiomyopathy secondary to period during refeeding. After receiving an intra- starvation and hypophosphataemia. The clinical venous dextrose-containing solution, there was manifestations of severe hypophosphataemia main- further deterioration of her muscle weakness, with ly involve the neuromuscular and cardiovascular the development of a bulbar palsy, complicated by systems.2 Paraesthaesia and numbness, muscle an aspiration pneumonia. The serum creatine weakness, acute rhabdomyolysis, acute respiratory kinase was normal and normal nerve conduction failure, acute bulbar symptoms, as well as central studies excluded the presence of a motor neuro- nervous system abnormalities such as tremors,by copyright. pathy. The first available serum inorganic phos- confusion, seizures and coma, have all been des- phate level was obtained at the time of maximum cribed. It has been implicated as a cause of weakness and was found to be extremely low reversible cardiomyopathy.5 In a report of three (0.08 mmol/l). The bulbar palsy resolved within 4 cases of anorexia nervosa complicated by sudden days of correcting the serum inorganic phosphate death, one case had severe hypophosphataemia with gradual improvement in her general weakness. (0.06 mmol/l) on the day of the event, which was In the absence ofearlier serum inorganic phosphate characterized by the development of a wide- values, we cannot be certain that acute hypophos- complex idioventricular rhythm.6 Our patient had phataemia was the cause of her sudden deteriora- a normal serum inorganic phosphate level for at tion. However, the clinical picture was similar to least 36 hours prior to her cardiorespiratory arrest. http://pmj.bmj.com/ that previously ascribed to severe hypophospha- There is no documentation of ventilatory failure taemia.2 prior to this event. She maintained her small heart The cause of this patient's severe hypophospha- size and normal electrocardiogram during her taemia is probably multifactorial. A diet deficient hospitalization, and at no stage was there evidence in phosphorus is rare as it is widely distributed in all of heart failure. natural foodstuffs. However, a prolonged period of Haematological abnormalities associated with near starvation, as in our patient, can lead to total severe hypophosphataemia include haemolytic on September 30, 2021 by guest. Protected body phosphorus depletion. Phosphorus is pre- anaemia, impaired leucocyte phagocytic function dominantly an intracellular anion, and the serum and possibly disordered platelet function. Ano- inorganic phosphate level is thus a poor reflection rexia nervosa itself commonly leads to haemato- of the intracellular and total body phosphorus logical abnormalities, which are reversible on status. improved nutrition and is the likely explanation for A second contributary factor is 'nutritional the abnormalities seen in this patient.5 The recovery syndrome', one of a small number of mechanisms postulated to play a role in most ofthe clinical situations described to cause severe hypo- clinical manifestations of hypophosphataemia in- phosphataemia, that is, less than 0.32 mmol/l.3 clude depletion of cellular adenosine triphosphate, During the anabolic state induced by refeeding, tissue hypoxaemia due to reduced erythrocyte 2,3 there is an influx of inorganic phosphate from the diphosphoglycerate resulting in impaired oxygen extracellular to the intracellular compartment. release and partial blockade of glycolysis due to This patient had 10 days of a balanced liquid lack of phosphorus as an important cofactor. polymeric preparation with a phosphate content of Although the hypophosphataemia was corrected 14.5 mmol/l prior to her first serum inorganic within 24 hours, the bulbar muscle weakness was Postgrad Med J: first published as 10.1136/pgmj.70.829.825 on 1 November 1994. Downloaded from CLINICAL REPORTS 827 fully recovered after 4 days.
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