Ion-selective electrodes for sodium and potassium: a new problem of what is measured and what should be reported

For clinical purposes the activities of Na+ and K+ obtained with ion-selective electrodes in undiluted whole blood or serum should be multiplied by an appropriate factor to obtain the same values as the substance concentrations obtained by flame photometry. The factor is primarily dependent on the mass concentration of water in normal plasma divided by the molal activity coefficient of Na+ (or K+) of normal plasma. We discuss the value of the molal activity coefficient of Na+ obtained by theoretical calculations and by direct measurement. The discrepancies between theory and measurement (gamma Na+ of 0.747 and 0.73, respectively) may be due to some binding of Na+ (protein binding or ion pair formation), a small and variable residual liquid-junction potential, or certainty about the appropriate value for the ionic strength of normal plasma (0.16 mol/kg or somewhat higher).     

Burn size estimation in children: Still a problem

Background: Accurate determination of burn size and depth forms an integral part of the initial assessment of any burn injury. Errors might lead to inaccurate fluid resuscitation and inappropriate transfer of patients to specialized burns units (BUs). Although recent data suggest some improvement in the estimation of burn injury in adults, this has not been shown in children. Methods: A retrospective review of children with burn injuries referred to the BU of our institution was performed. Data were collected from all patients presenting to the BU during the calendar year 2009. The total body surface area burned (TBSA‐B) estimated by the referring centre was compared with the actual TBSA determined measured on arrival at the BU. Results: Of the 71 paediatric patients referred during the study period, 10 did not have any TBSA‐B estimation documented by the referring hospital. Inaccurate estimation of burn area was noted in 48 out of 61 patients (79%). Burn size was more likely to be overestimated than underestimated by a ratio of 2.2 to 1, especially in burns >10% TBSA‐B (P= 0.002). Conclusions: Inaccurate estimation of burn size remains a problem in children. The persistent miscalculation of burn size might be a result of the various methods employed in assessing burn area, the inclusion of simple erythema and inadequate training or exposure of first responders. Accurate assessment of TBSA‐B and burn depth in children remains elusive and would appear to require additional training and education.     

Limiting care: should age be a criterion?

The rising costs of health care coupled with the dramatic increase in the number of individuals over the age of 65 years presents the health care industry with the dilemma of an increased demand for services and goods, with limited resources. Physicians, economists, and ethicists have suggested various solutions to this problem, including the controversial proposal strongly advocated by Daniel Callahan, of age-based rationing. This article explores some of the issues that are woven into the allocation of health care resources based on age. Although there are no easy answers to this dilemma, the critical care nurse needs to be familiar with these issues to function effectively as a patient advocate. Some suggestions to enhance this aspect of critical care nursing will also be discussed.     

针对透析患者的营养不良应深入研究及规范性治疗

维持性透析治疗的终末期肾脏病患者逐年增加已成为世界性的公共卫生和社会问题。2002-2003年世界各地统计数据显示，澳大利亚、欧洲、美国每百万人的终末期。肾脏疾病（ESRD）患病率分别达658、700、1403人。随着我国经济水平的提高，透析技术的不断发展，维持性透析患者长期生存率大大提高，但营养不良的问题日趋突出。不仅影响患者的生活质量，也是并发症和病死率增加的一个重要因素，因此防治透析患者营养不良是肾脏病工作者面临的重要课题。     

Peripartum cardiomyopathy: a condition intensivists should be aware of

We use an illustrative case of severe peripartum cardiomyopathy with congestive heart failure to introduce this topic and proceed to cover its pathophysiology, incidence, management and outcome.     

Oral and maxillofacial surgery: should a district service be retained?

The adult new patient attendances at a District General Hospital for 1988 and 1989 have been analysed and the patients with oral and maxillofacial injuries identified. The injuries were classified using the International Classification of Diseases. The time spent undertaking emergency surgery out of hours by each firm using the operating facility has been analysed. An argument for a national district service in Oral and Maxillofacial Surgery is developed and advanced drawing on the results obtained from the study.     

Plasma potassium, serum magnesium and ventricular fibrillation: a prospective study

Low plasma potassium and magnesium concentrations have beenadvanced as risk factors for ventricular fibrillation (VF).For potassium, this assertion is based almost exclusively onretrospective data; for magnesium the evidence shows an associationwith ventricular arrhythmias but no direct association withVF. We studied the relationship between these electrolytes andVF prospectively. Plasma potassium and serum magnesium concentrations were measuredon admission to our coronary care unit. Drug therapy, time fromonset of symptoms, ECG, enzyme changes and clinical status wereall recorded. VF was confirmed by analysis of 24 h monitoringtapes. Mean plasma potassium in the 21 patients with VF who had measurementsprior to their arrhythmia was 3.49±0.54 mmol/l, lowerthan that of the 1165 patients without VF (mean K 3.88±0.57mmol/l, p<0.05). Plasma potassium concentrations in the 17patients with myocardial infarction and VF were lower (mean3.58 ± 0.41 mmol/l) than in those without VF (n = 417,mean 3.89 ± 0.61 mmol/l) (p < 0.05). Mean serum magnesiumin the 12 patients with VF, measured prior to their arrhythmia(all with myocardial infarction) was 0.80 ± 0.07 mmol/l,which was not different from the mean for patients without VF(n = 781, 0.82 ± 0.09 mmol/l) or from the mean of 0.81± 0.08 mmol/l for those with infarction but not VF (n= 331). Low plasma potassium concentrations are associated with increasedrisk of ventricular fibrillation, but low serum magnesium concentrationsare not.