Using 0.45% saline solution and a modified dosing regimen for infusing N‐acetylcysteine in children with paracetamol poisoning

Introduction: N‐acetylcysteine (NAC) administration is recommended to all patients judged to be at risk of developing hepatotoxicity following paracetamol overdose. However, it has been shown that standard i.v. dosing can cause symptomatic hyponatraemia in children. We describe a case series using 0.45% NaCl plus 5% dextrose for infusing i.v. NAC in children with paracetamol poisoning. Case series: A retrospective review of medical records of patients treated with NAC using 0.45% saline plus 5% dextrose, and a novel two‐stage dosing regimen between January 2003 and July 2006 were undertaken. Results: A total of 40 patients (20 male and 20 female) who received NAC in 0.45% sodium chloride (NaCl) with 5% dextrose were identified. Mean age was 9 years 6 months (95% CI 4 years 4 months to 15 years 1 month) and the range 3 months to 17 years. All patients had NAC infused in a two‐stage infusion regimen (150 mg/kg bolus over 1 h followed by a continuous infusion of 10 mg/kg/h for 20 h). The serum sodium was measured in all 40 patients with a mean of 140 (range of 133 to 152 mmol/L). Repeat sodium was measured in 35 cases, with a mean of 140 mmol/L (range from 134 to 149 mmol/L). Conclusion: These findings support the use of saline‐containing solutions to administer NAC as an alternative to 5% dextrose, and suggest that a two‐stage infusion regimen should be further investigated with prospective studies.     

Lack of laboratory assessment of severe hyponatraemia is associated with detrimental clinical outcomes in hospitalised patients

Objective: Increased mortality with severe hyponatraemia is well known. What is less clear is the mortality risk according to the pattern of the developing hyponatraemia and whether this may be affected by the intervention of the clinician. Methods: From our laboratory database, we retrospectively collected data of a 12‐month period of adult patients with severe hyponatraemia (≤ 120 mmol/l). One hundred and thirteen patients were identified. Normonatraemic controls (n = 113) were identified by plasma sodium of 135 mmol/l over the same period, and whose nadir during hospitalisation was ≥ 130 mmol/l. Results are mean ± SD unless stated otherwise. Duration of hospitalisation and clinical outcomes was confirmed from hospital records. Results: The mean nadir plasma sodium of the hyponatraemic group was 116.0 ± 4.4 mmol/l and 134.0 ± 2.8 mmol/l in controls. Although the hyponatraemic patients were younger than controls (65.8 ± 18.4 vs. 72.3 ± 14.9 years; p = 0.004), they had higher mortality (24 vs. 7, p = 0.002) and longer hospitalisation than controls: median (IQR), 12 (7–22) vs. 7 (3–16.5) days (p < 0.001). A total of 55 patients developed severe hyponatraemia following admission. This subgroup comprised a higher proportion of surgical patients (23.6% vs. 1.7%, p < 0.001) than those with severe hyponatraemia on admission. Furthermore, both mortality (n = 17 vs. n = 7; p = 0.02) and duration of hospitalisation, median 19 days (IQR 10–35) vs. 9.5 (5–15) days (p < 0.001), were greater. Failure to measure plasma and urinary osmolalities was associated with increased mortality. Conclusions: Severe hyponatraemia is associated with prolonged admission and increased mortality compared with normonatraemic patients. Progressive hyponatraemia following admission incurs a higher risk of death. This may represent illness‐severity, inappropriate management or inadequate investigation.     

Hyponatraemia in patients with normal pressure hydrocephalus

Background: In clinical practice, hyponatraemia was frequently found in patients with hydrocephalus. We conducted this study to determine the prevalence and risk factors for hyponatraemia in patients with normal pressure hydrocephalus (NPH). Methods: We retrospectively reviewed all patients with NPH who were admitted to China Medical University Hospital between 1998 and 2006. Hyponatraemia was defined as a plasma sodium concentration < 135 mEq/l on admission. Possible risk factors between patients with and without hyponatraemia were analysed using Student’s t‐test or χ² test. The association between hyponatraemia and possible factors was analysed using multivariate logistic regression. The odds ratio was calculated to determine the effect of possible risk factors. Results: A total of 146 patients (84 men and 62 women) who had NPH with a mean age of 66.1 ± 15.9 years old were reviewed and 33 (22.6%) patients were found having hyponatraemia. Patients who developed hyponatraemia had a significantly higher prevalence of hypertension, use of nasogastric tube (NG), bed‐ridden status and fever. In multivariate logistic regression, the presence of hypertension and the use of NG were two important risk factors for hyponatraemia. The odds ratio (95% CI) for hypertension and NG were 2.604 (95% CI: 1.136–5.967, p = 0.024) and 7.179 (95% CI: 2.3–22.409, p = 0.001) respectively. Conclusion: Hyponatraemia is not uncommon in patients with NPH. Physicians should be aware of this complication and obtain necessary laboratory examination for early detection of hyponatraemia.     

Pilot safety study of low-dose vasopressin in non-septic critically ill children

Objective  To assess the safety of low-dose vasopressin infusion in critically ill children requiring prolonged mechanical ventilation (MV) at risk of developing sedation/analgesia-related hypotension. Method  Randomized pilot safety study in children expected to require MV for at least 3 days. Children received either vasopressin (0.0005 U/kg/min) or sodium chloride (0.9%) infusion for a period of 48 h. Haemodynamic variables, urine output and serum electrolytes were closely monitored and analyzed. Results  Twelve children in each group had similar baseline characteristics. Vasopressin infusion was associated with an 8 mmol/L fall in serum sodium concentration (p < 0.01) and with higher incidence of hyponatraemia (8 vs. 66%, p < 0.01). In normotensive children, low-dose vasopressin also induced a reversible decrease in urine output, and acutely increased blood pressure (p < 0.01). After stopping the vasopressin there was rebound hypotension (p < 0.01). Conclusion  Low-dose vasopressin infusion in haemodynamically stable, but critically ill, children is associated with reduction in urine output and decreased serum sodium level, yielding a high incidence of hyponatraemia. We conclude that these effects limit further study of prophylactic vasopressin for sedation-related hypotension in a randomized controlled trial.     

Osmotic myelinolysis syndrome after treatment of severe deamino arginine vasopressin-associated hyponatraemia: pitfalls in emergency medicine

Hyponatraemia is among the more common electrolyte abnormalities encountered in the ED. Both the primary disturbance and its correction can result in life-threatening neurological sequelae. Osmotic myelinolysis syndrome is one such complication and is associated with the rapid correction of hyponatraemia. The present case report describes the mechanism of severe hyponatraemia in a patient taking deamino arginine vasopressin, and the subsequent development of both central pontine and extrapontine myelinolysis after rapid correction of sodium levels. Implications for the emergency management of such patients are discussed.     

The epidemiology of intensive care unit-acquired hyponatraemia and hypernatraemia in medical-surgical intensive care units

Introduction

Although sodium disturbances are common in hospitalised patients, few studies have specifically investigated the epidemiology of sodium disturbances in the intensive care unit (ICU). The objectives of this study were to describe the incidence of ICU-acquired hyponatraemia and hypernatraemia and assess their effects on outcome in the ICU.

Methods

We identified 8142 consecutive adults (18 years of age or older) admitted to three medical-surgical ICUs between 1 January 2000 and 31 December 2006 who were documented to have normal serum sodium levels (133 to 145 mmol/L) during the first day of ICU admission. ICU acquired hyponatraemia and hypernatraemia were respectively defined as a change in serum sodium concentration to below 133 mmol/L or above 145 mmol/L following day one in the ICU.

Results

A first episode of ICU-acquired hyponatraemia developed in 917 (11%) patients and hypernatraemia in 2157 (26%) patients with an incidence density of 3.1 and 7.4 per 100 days of ICU admission, respectively, during 29,142 ICU admission days. The incidence of both ICU-acquired hyponatraemia (age, admission diagnosis, Acute Physiology and Chronic Health Evaluation (APACHE) II score, length of ICU stay, level of consciousness, serum glucose level, body temperature, serum potassium level) and ICU-acquired hypernatraemia (baseline creatinine, APACHE II score, mechanical ventilation, length of ICU stay, body temperature, serum potassium level, level of care) varied according to patients' characteristics. Compared with patients with normal serum sodium levels, hospital mortality was increased in patients with ICU-acquired hyponatraemia (16% versus 28%, p < 0.001) and ICU-acquired hypernatraemia (16% versus 34%, p < 0.001).

Conclusions

ICU-acquired hyponatraemia and hypernatraemia are common in critically ill patients and are associated with increased risk of hospital mortality.     

Critical illness with hyponatraemia and impaired cell membrane integrity--the "sick cell syndrome" revisited

OBJECTIVE: To determine whether impaired cell membrane permeability exists in critically ill patients with "sick cell" type hyponatraemia. DESIGN AND METHODS: A 36 year old male patient was identified in an intensive care unit (ICU) with liver disease and multi-organ failure. His initial serum sodium (Na) was 101 mmol/L and osmolar gap + 35 mmol/L. A flow cytometric system was used to assess lymphocyte membrane integrity using fluorescein diacetate (FDA) and propidium iodide (PI). Following this, similar studies were carried out in 17 hyponatraemic (Na < 130 mmol/L) and 19 normonatraemic (Na > 136 mmol/L) ICU patients. RESULTS: Flow cytometry in the index patient showed two clear populations of cells-one was normal (with identical characteristics to a healthy control) and the other had dysfunctional cell membrane integrity. The extended patient series, however, revealed only 2 other patients with similar flow cytometric patterns-one hyponatraemic and one normonatraemic. CONCLUSIONS: Cell membrane studies in the index patient demonstrated supportive evidence for the "sick cell syndrome" in critically ill patients. The extended series revealed that 3/37 (8%) had this abnormality, which was however not consistently associated with hyponatraemia.     

Severe hyponatraemia in medical in-patients: aetiology, assessment and outcome

BACKGROUND: Hyponatraemia is the most commonly identified electrolyte abnormality. Published data on severe hyponatraemia in general medical in-patients is lacking. AIM: To determine the aetiology, adequacy of assessment, and outcome of severe hyponatraemia in general medical in-patients. DESIGN: Retrospective case-note review. METHODS: All general medical in-patients (n = 108) with serum sodium < or =125 mmol/l were identified from the clinical chemistry database, over a six-month period. A full review of notes and computer records was undertaken at the index date and a pre-determined follow-up date. RESULTS: Follow-up data were available in 105 patients. There was a wide range of aetiologies: diuretic therapy (loop and thiazide), congestive cardiac failure and liver disease were the most common, and 75.3% of patients had multiple causes. None of the 48% of patients whose history suggested a possible diagnosis of the syndrome of inappropriate anti-diuretic hormone (SIADH) met the generally accepted diagnostic criteria. Overall mortality was 20% during the index admission and 44.6% at follow-up, vs. 7.1% and 22%, respectively, for other patients admitted to the same directorate over the same time period (p < 0.001). Mortality was linked to aetiology, but not to reduced absolute serum sodium concentration at admission. DISCUSSION: Severe hyponatraemia in general medical patients is associated with a complex, multifactoral aetiology and a very poor prognosis. Outlook is governed principally by aetiology, and not by serum sodium level. Assessment of patients with hyponatraemia requires a practical clinical algorithm for diagnosing SIADH.     

Fatal hyponatraemic brain oedema due to common gastroenteritis with accidental water intoxication

Acute symptomatic hyponatraemia is a life-threatening emergency which must be diagnosed and treated promptly. The initial symptoms are often dramatic, with seizures and coma, and there is therefore a risk that the diagnosis and the urgent sodium correction therapy may be delayed by procedures such as computed tomography (CT) of the brain. As the most common aetiological factors are psychotic polydipsia and different iatrogenic causes, this condition usually develops in hospitalised patients. Water intoxication alone is very unlikely to cause severe hyponatraemia in a person with normal renal function, unless for some reason the antidiuretic hormone secretion is increased. We describe a case in which dehydration due to common gastroenteritis in combination with excessive intake of water caused the death of a young, previously healthy woman. Increased awareness of this potentially fatal condition is recommended. Received: 6 August 1996 Accepted: 13 December 1996     

Exercise‐Induced Natriuretic Peptide Secretion Predicts Cardioversion Outcome in Patients with Persistent Atrial Fibrillation: Discordant ANP and B‐Type Natriuretic Peptide Response to Exercise Testing

Background: Measurement of natriuretic peptide's (NP) release in response to hemodynamic stress may be complementary to its baseline assessment in individuals. Atrial natriuretic peptide (ANP) and B‐type natriuretic peptide (BNP) increase in patients with atrial fibrillation (AF) and decrease after successful cardioversion, suggesting that AF may stimulate secretion of NPs. However, there are conflicting data on the predictive value of NPs on the cardioversion outcome. Objectives: The purpose of this study was to investigate whether baseline and exercise‐induced NP plasma levels can be useful in predicting successful cardioversion of persistent AF and maintenance of sinus rhythm during 6‐month follow‐up. Methods: A prospective study enrolled 77 consecutive subjects with persistent AF with normal left ventricular function, referred for elective cardioversion. Patients underwent a modified Bruce protocol treadmill exercise test 24 hours before cardioversion. Blood samples for ANP and BNP analyses were obtained at rest and 5 minutes after exercise peak. Results: The group of successful cardioversion and stable sinus rhythm presented higher exercise ANP (110.6 ± 41.2 pg/mL vs 43.8 ± 36.1; pg/mL, P < 0.0001) and lower BNP increase (5.2 ± 5.2 pg/mL vs 40.5 ± 34.2 pg/mL, P < 0.0001) than the group of unsuccessful cardioversion or AF recurrence. Using an optimized cutoff level of ≤12% of relative exercise‐induced increase in BNP concentration, and of >50 pg/mL of ANP increase, successful cardioversion can be predicted with high accuracy. Conclusions: An increase in ANP and stability of BNP plasma concentration during exercise testing are independently associated with successful cardioversion and maintenance of sinus rhythm during 6‐month follow‐up. (PACE 2010; 33:1203–1209)     

Berg adder (Bitis atropos) envenoming: an analysis of 14 cases

Introduction: The berg adder (Bitis atropos) is a little-studied, lesser-known viperid snake found in southern Africa and there is limited information available regarding the manifestations of envenoming.

Materials and methods: This observational series of 14 cases documents features of berg adder envenoming over a period of 16 years (1987–2003).

Clinical features of envenomed patients: All 14 patients developed local cytotoxic effects. Thirteen patients developed systemic effects manifesting and documented in varying degrees. These include (1) prominent vomiting (2) disturbances in cranial nerve function (anosmia and altered taste, an ophthalmological triad of ptosis, mydriasis and visual disturbances including loss of accommodation, and dysphagia) (3) a global decrease in motor power where mechanical ventilation was often required for respiratory failure and (4) hyponatraemia (lowest value recorded 111?mmol/L), sometimes with associated convulsions.

Discussion: The full range of polypeptides present in berg adder venom is yet to be characterised. However, two closely related phospholipases A₂ (PLA₂; PLA₂-1 and PLA₂-2) have been purified from the venom of B. atropos and clinical evidence suggests that a natriuretic peptide is also possibly present. Envenoming results in distinctive, sometimes life-threatening, manifestations.     

Retraction: Effects of a transtheoretical model–based exercise stage–matched intervention on exercise behaviour and quality of life in patients with coronary heart disease: a randomized controlled trial

The above article from Journal of Advanced Nursing, published online on 26th June 2014 in Wiley Online Library ( wileyonlinelibrary.com ) has been retracted by agreement between the journal Editor‐in‐Chief and John Wiley & Sons Ltd. The retraction has been agreed due to considerable overlap with the following papers: Zhu L.‐X., Ho S.‐C., Sit J.W.H., He H.‐G. (2014) Effect of a transtheoretical model‐based stage‐matched exercise intervention on exercise behavior and angina in patients with coronary heart disease: a randomized controlled trial. Journal of Cardiovascular Nursing DOI: 10.1097/JCN.0000000000000162 . Zhu L.‐X., Ho S.‐C., Sit J.W.H., He H.‐G. (2014) The effects of a transtheoretical model‐based exercise stage‐matched intervention on exercise behavior in patients with coronary heart disease: A randomized controlled trial. Patient Education and Counseling 95, 384–392. Reference Zhu L‐X., Ho S‐C., Sit J.W.H. & He H‐G. (2014) Effects of a transtheoretical model–based exercise stage–matched intervention on exercise behaviour and quality of life in patients with coronary heart disease: a randomized controlled trial. Journal of Advanced Nursing. doi: 10.1111/jan.12469     

High-sensitivity C-reactive protein as a predictor of atrial fibrillation recurrence after primary circumferential pulmonary vein isolation

Background: Atrial fibrillation (AF) recurrence after circumferential pulmonary vein isolation (CPVI) is difficult to predict. Inflammation is associated with the development of AF. Inflammatory markers, such as high sensitivity C‐reactive protein (hsCRP), are related to AF development via atrial remodeling. However, it is unknown whether plasma hsCRP concentration before CPVI can be used as a predictor for AF recurrence. Methods: A total of 121 patients without structural heart disease who underwent primary CPVI by a single operator were included in the study (paroxysmal/persistent AF: 77/44). Left atrial diameter was measured by transesophageal echocardiography. Plasma hsCRP concentration was determined by enzyme‐linked immunosorbent assay. Based on the follow‐up outcomes, patients were divided into two groups, a recurrence group and a nonrecurrence group. AF recurrence was defined as AF or atrial flutter or atrial tachycardia episodes lasting for ≥30 s during regular follow‐up (>12 months). Results: A total of 36 (29.8%) patients (paroxysmal/persistent AF: 19 [24.7%]/17 [38.6%]) had AF recurrence in a mean 23 (range, 12–44) month follow‐up period. The plasma hsCRP concentration in the recurrence group was significantly higher than that in the nonrecurrence group for all patients (median [quartile range] 2.22 [1.97] mg/L vs 0.89 [1.30] mg/L, P < 0.001), for patients with paroxysmal AF (2.12 [2.78] mg/L vs 0.84 [1.15] mg/L, P = 0.028), and for those with persistent AF (2.29 [1.08] mg/L vs 0.89 [1.53] mg/L, P = 0.005). Multiple logistic regression analyses showed that the higher level of the plasma hsCRP (P < 0.001) was a significant prognostic predictor of AF recurrence, both for patients with paroxysmal AF (P = 0.012) and those with persistent AF (P = 0.003). Conclusion: Plasma hsCRP concentration before CPVI was associated with AF recurrence after primary CPVI procedure for both paroxysmal and persistent AF patients. Plasma hsCRP concentration could play a role in prediction of AF recurrence after primary CPVI. (PACE 2011; 34:398–406)     

Noninvasive risk stratification techniques in pediatric patients with ventricular preexcitation

Background: Individuals with ventricular preexcitation (VP) are known to have an increased risk of sudden death. This risk has been associated with conduction properties of the accessory pathway. Methods: Patients with VP underwent risk stratification through the use of exercise and transesophageal testing. All patients were initially screened with exercise testing and those with preexcitation throughout exercise went on to have transesophageal testing. Patients who demonstrated high‐risk pathway characteristics by transesophageal testing or developed clinical indications for an electrophysiology (EP) study underwent ablation. This stepwise risk stratification technique was evaluated for the ability to avoid the need for intracardiac EP study. Patients stratified as low risk were contacted for follow‐up. Results: One hundred and twenty‐nine exercise studies were performed in 127 patients. Thirty‐five of 129 exercise studies demonstrated accessory pathway block during exercise. Twenty‐seven of 35 underwent no additional testing. Sixty‐six patients underwent transesophageal testing. Forty‐nine of 66 patients demonstrated low‐risk pathway characteristics and 40 of 49 underwent no further testing. In total, 68 of 129 (53%) patients avoided the need for intracardiac EP study and ablation. A noncardiac indication for the initial diagnostic electrocardiogram was associated with lower likelihood of intracardiac EP study. None of the patients stratified as low risk had additional invasive procedures or life‐threatening arrhythmias upon follow‐up. Conclusions: Successful risk stratification of pediatric patients with VP is possible through the use of exercise and transesophageal testing. In this patient population, half of the patients were able to avoid an intracardiac EP study. (PACE 2011; 34:555–562)     

A new method to quantify postexercise ST‐deviation – the ST‐deficit. A study in men at high and low‐risk for coronary heart disease

Background Quantitative heart rate adjusted exercise ST criteria like μV/beats per minute (bpm) improve the diagnostic accuracy of the exercise ECG. However, there are few quantitative HR adjusted postexercise variables available. The aim of the present exercise study was to evaluate a new such variable from computerized averaging of the postexercise ECG. Methods The presence of possible myocardial ischaemia in a population based sample of 74 elderly male hypertensives at high‐risk of coronary heart disease, and in 42 age‐matched clinically healthy males (reference group) at low‐risk was assessed by exercise ECG. All men had a normal resting ECG without signs of ischaemia. Variables studied: standard ST‐criteria, ST/HR slope ≤–2·4 μV · bpm^–1, shape of the rate‐recovery loop, the latter also with a new quantitative variable, the ST‐deficit. Results In spite of a normal resting ECG many subjects showed an abnormal ST/HR slope during exercise, 43% in the hypertension group and 26% in the reference group. An abnormal rate‐recovery loop (ST‐deficit) also contributed substantially to identify patients with possible myocardial ischaemia, 30 vs. 10%, respectively (P<0·02); cumulatively for the two HR adjusted criteria 53% vs. 29%, respectively (P<0·02). Mean ST‐deficit was significantly lower in the high‐risk group. Conclusions Effort‐related myocardial ischaemia is frequently silent in elderly high‐risk hypertensives and necessitates testing, preferably with computerized exercise ECG and heart rate adjusted ST criteria. A new quantitative variable to assess the postexercise rate‐recovery loop in the time domain, the ST‐deficit is described. This variable seems to effectively discriminate between subjects with low and high‐risk for coronary heart disease and thus provides new information. Further studies are warranted to validate this variable against myocardial perfusion scintigraphy and coronary angiography.     

Prognostic role of high-sensitivity C-reactive protein and B-type natriuretic peptide in implantable cardioverter-defibrillator patients

Background: High‐sensitivity C‐reactive protein (hs‐CRP) and B‐type natriuretic peptide (BNP) are useful biomarkers for cardiovascular risk stratification. Little data are available regarding the prognostic value of hs‐CRP and BNP serum levels and future ventricular arrhythmic events triggering implantable cardioverter defibrillator (ICD) therapy. Methods: A total of 100 patients eligible for ICD implantation were enrolled in a prospective cohort study. Serum levels of hs‐CRP and BNP were obtained the day before ICD implantation and at scheduled follow‐up visits. For risk analysis, the study cohort was dichotomized based on serum level of hs‐CRP using a cut‐off value of 3 mg/L. The endpoint was appropriate ICD therapy triggered by ventricular arrhythmias during a follow‐up of 24 months. Results: Appropriate ICD therapy was delivered in 20% of patients. Median baseline serum level of hs‐CRP was significantly higher in patients with appropriate ICD therapy than in those without appropriate ICD therapy (5.33 mg/L vs 2.19 mg/L; P = 0.002). The same was true for median serum levels of hs‐CRP and BNP during follow‐up (5.43 mg/L vs 2.61 mg/L, P = 0.001 and 261.0 pg/mL vs 80.1 pg/mL, P = 0.01, respectively). Multivariate analysis demonstrated that baseline hs‐CRP level > 3 mg/L was independently associated with appropriate ICD therapy (odds ratio 4.0, 95% 1.1–14.2; P = 0.03). Conclusion: Elevated preimplantation hs‐CRP serum level is independently associated with increased risk for appropriate ICD therapy. Monitoring for elevated BNP levels during follow‐up adds to the assessment of risk for future arrhythmias. (PACE 2011;1–8)     

Validity of Oxycon Mobile in measuring inspiratory capacity in healthy subjects

Introduction: Inspiratory capacity (IC) assessments have been performed mainly in laboratory settings, because of fixed measurement devices. Oxycon Mobile^® (OM) is the mobile and wireless version of Oxycon Pro^® (OP), a commonly used fixed measurement device. The purpose of this study was to examine IC agreement between OM and OP at rest and during steady‐state exercise. Also, the within‐ and between‐days variability of IC’s were determined. Methods: Thirty‐five healthy subjects were recruited. Twenty‐five subjects were included for determining validity of the OM and ten subjects for the variability study. For validation of OM, resting and exercise IC’s (IC_rest and IC_exercise respectively) were measured consecutively by OM and OP, in random order. Exercise consisted of cycle ergometry at 50% of subject’s predicted maximal exercise capacity. Results: The mean difference between OM and OP regarding IC_rest was ?0·05L, with limits of agreement of ?0·47 to 0·37L (or ?1·2% with limits of agreement of ?11·6 to 9·3%) (P>0·05). The mean difference of IC_exercise was ?0·06L, and the limits of agreement were ?0·48 to 0·35L (or ?1·4% with limits of agreement of ?11·8 to 9·0%) (P>0·05). No significant differences in IC’s within‐ or between‐days were found. Discussion: The limits of agreement of the IC measured by OM and OP were ±10%, which is recommended for interdevice reproducibility. We conclude that OM and OP can be used interchangeably for measuring IC at rest and during steady‐state exercise.     

Osmotic demyelination syndrome: a potentially avoidable disaster

Osmotic demyelination of the brain (ODS) is a dreaded complication that typically occurs several days after aggressive therapy for chronic hyponatraemia, but is eminently avoidable. In this teaching exercise, Professor McCance, an imaginary consultant, is asked to explain how he would have treated a 28-year-old female who had hyperkalaemia, hypoglycaemia, hypotension and hyponatraemia (118 mM) to prevent the development of ODS. He begins with a review of the physiology, including his own landmark work on chronic hyponatraemia associated with a contracted extracellular fluid volume. Adding quantitative analysis, the cause of the excessive rise in plasma sodium concentration is revealed, and a better plan for therapy is proposed.     

Rapid correction of hyponatraemia with urea may protect against brain damage in rats

1. Rapid correction of hyponatraemia in humans has been reported to be associated with central pontine myelinolysis (CPM). In patients with hyponatraemia related to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) we have rapidly corrected hyponatraemia by using urea, without observing clinical CPM. This led us to analyse the brain damage induced by hypertonic saline and by urea when used for the correction of hyponatraemia in a rat model of SIADH. 2. Severe hyponatraemia (serum Na+ less than 115 mmol/l) was produced in 28 rats. Seven rats were excluded from statistical analysis because they died during the correction of hyponatraemia, or because they were under- or over-corrected. Normalization of serum Na+ (135-146 mmol/l) was obtained in 48 h by hypertonic saline (group I, n = 7) or urea (group II, n = 8). 3. Despite similar correction of serum Na+ at 24 h and 48 h, all the rats treated with hypertonic saline presented severe brain damage, whereas those treated with urea were free of any brain damage. A third group of rats (n = 6) who spontaneously corrected their serum sodium level and presented mild hyponatraemia at 48 h (129 +/- 5.2 mmol/l) were also free of any brain damage.