An article for physicians by physicians
Originally published December 2008
Hyponatremia may occur during rehydration or with maintenance fluids, and can have serious adverse effects, including neurologic impairment and death.
Of interest to all physicians caring for children
Over the past several years, there have been an increasing number of reports published which recognize that excess or inappropriate rehydration fluids may result in a complication of hyponatremia, particularly in the paediatric population. The intent of this article is to heighten awareness of hyponatremia, a condition that can occur in a variety of clinical settings and for which the warning signs are often non-specific and easily missed by even the most experienced health providers.
Some of the issues are illustrated in the following case.
A two-year-old child with a one-day history of multiple episodes of vomiting and diarrhea was admitted to the paediatric unit of a general hospital with a provisional diagnosis of gastroenteritis. Blood work drawn on arrival in the emergency department (ED) was normal including a serum sodium level of 140 mmol/L. The child was unable to tolerate oral rehydration fluids, so an intravenous (IV) of normal saline was initiated at 100 ml/hr in the ED.
The on-call paediatrician assessed the child and found him to be reasonably hydrated with a moist tongue, slightly sunken eyes and a fever of 38.4°C tympanic. She confirmed the diagnosis of gastroenteritis, probably viral. The child had already received 400 ml of IV normal saline up to this point. Based on the child's weight and estimated dehydration, she changed the IV solution to dextrose 3.3 per cent in sodium chloride 0.3 per cent (2/3-1/3) at 70 ml/hr with maintenance potassium chloride (KCl) 10 mmol per 500 ml after the child's first void.
The paediatrician reassessed the child the following morning. Although irritable, he was afebrile, had normal vital signs and had recently voided a large amount. The physician did not document this visit in the child's health record nor did she order a repeat of the serum electrolytes. Although the child had tolerated sips of fluids overnight, the paediatrician was advised that he continued to vomit intermittently throughout the day. His urine output appeared to be adequate; however, the nursing staff did not document the precise fluid balance.
In the mid-afternoon, the nursing staff notified the paediatrician that the child had become increasingly lethargic and less responsive over the previous two hours, although his vital signs had remained stable. Five minutes after this call, the child had a focal seizure. Further seizure activity was noted 40 minutes later. The paediatrician promptly attended the child, who appeared to be unconscious but reacted to painful stimuli, and an anticonvulsant was administered intravenously. The paediatrician queried an electrolyte imbalance or viral encephalitis at that time and ordered stat blood chemistry, a CT scan of the head and an EEG.
While in the diagnostic imaging suite, the child suffered a respiratory arrest, requiring endotracheal intubation. Electrolytes drawn at the time of the second seizure revealed a serum sodium of 124 mmol/L. Following resuscitative measures, the child was transferred to a tertiary care centre in a comatose state for further management. His condition deteriorated and life support was withdrawn the following day. The autopsy showed evidence of severe cerebral edema with bilateral uncal herniation.
The family initiated a legal action alleging the paediatrician failed to properly assess the child the day following admission and failed to order the appropriate diagnostic investigations and treatments. They also alleged the hospital nurses failed to adequately monitor the child's clinical status and delayed advising the paediatrician of the child's worsening condition.
Experts' opinions for this case
Paediatric experts expressed the view that the paediatrician fell below the standard of care by not performing a more thorough reassessment of the child the morning following his admission and by failing to document this visit. According to the experts, if the physician had performed the appropriate blood tests, the hyponatremia would have been discovered and corrective measures could have been taken.
Without expert support, the CMPA, on behalf of the paediatrician, and the hospital, on behalf of the nurses, contributed to a shared settlement to the plaintiff.
Review of medico-legal cases
The CMPA undertook a review of all medico-legal cases closed between 1998 and 2007 involving paediatric hyponatremia. This case review revealed that medico-legal difficulties associated with paediatric hyponatremia are infrequent at the CMPA. However, the patient clinical outcomes associated with hyponatremia can be extremely serious.
Eight cases were identified. Three children died as a consequence of cerebral edema resulting from hospital-acquired hyponatremia. Two of these three patients had presented with viral enteritis on admission to hospital, and one was a patient who had successfully undergone surgery but developed hyponatremia related to fluid management in the post-operative period. Three other children suffered serious permanent neurologic impairments, although comorbid conditions and other complications also played a role in their clinical outcomes. The remaining two children recovered with no known sequelae. In the majority of these cases, the physician had prescribed a hypotonic IV solution to treat the clinical condition.
In the medico-legal cases reviewed, the following allegations related to the diagnosis and management of hyponatremia were noted:
delay or failure to reasonably perform or monitor serum sodium levels or respond to abnormal results;
delay or failure to prescribe an appropriate IV solution;
delay in recognizing or not appreciating the significance of early warning signs and symptoms of hyponatremia in the child who has received rehydration fluids, either orally or intravenously;
ineffective communication of the treatment plan between physicians or between a physician and another health care professional; and
lack of documentation of clinical assessment and treatment plans.
Risk management considerations
Based on a review of expert opinions obtained from all of the medico-legal cases involving paediatric hyponatremia, consider the following risk management strategies:
Are you familiar with current clinical guidelines for maintenance and replacement fluid therapy, particularly in paediatric patients?
Are baseline and appropriate ongoing monitoring of serum electrolytes indicated?
Are you aware of the early warning signs and symptoms of hyponatremia?
Have you considered why there is a failure of the child to improve clinically?
Have you considered the parents' concerns about their child's condition?
Does the documentation reflect your clinical impressions at the time of assessment and the rationale for your treatment?
Have you communicated the treatment plan effectively to other physicians or health care professionals involved in the child's care?
The symptoms and signs of hyponatremia are frequently non-specific initially. The diagnosis may elude even knowledgeable and experienced physicians. This article is provided to heighten the awareness of the profession to the condition of hyponatremia, particularly in children receiving fluid therapy.