Changes in the plasma sodium concentration after minor, moderate and major surgery

The efficacy of hypotonic and near-isotonic saline for parenteral fluid therapy given at low maintenance rate in preventing significant change in plasma sodium in post-operative pediatric patients: protocol for a prospective randomized non-blinded study

BACKGROUND

Hyponatremia is the most frequent electrolyte abnormality observed in post-operative pediatric patients receiving intravenous maintenance fluid therapy. If plasma sodium concentration (p-Na+) declines to levels below 125 mmol/L in < 48 h, transient or permanent brain damage may occur. There is an intense debate as to whether the administered volume (full rate vs. restricted rate of infusion) and the composition of solutions used for parenteral maintenance fluid therapy (hypotonic vs. isotonic solutions) contribute to the development of hyponatremia. So far, there is no definitive pediatric data to support a particular choice of parenteral fluid for maintenance therapy in post-surgical patients.

METHODS/DESIGN

Our prospective randomized non-blinded study will be conducted in healthy children and adolescents aged 1 to 14 years who have been operated for acute appendicitis. Patients will be randomized either to intravenous hypotonic (0.23% or 0.40% sodium chloride in glucose, respectively) or near-isotonic (0.81% sodium chloride in glucose) solution given at approximately three-fourths of the average maintenance rate. The main outcome of interest from this study is to evaluate 24 h post-operatively whether differences in p-Na+ between treatment groups are large enough to be of clinical relevance. In addition, water and electrolyte balance as well as regulatory hormones will be measured.

DISCUSSION

This study will provide valuable information on the efficacy of hypotonic and near-isotonic fluid therapy in preventing a significant decrease in p-Na+. Finally, by means of careful electrolyte and water balance and by measuring regulatory hormones our results will also contribute to a better understanding of the physiopathology of post-operative changes in p-Na+ in a population at risk for hyponatremia.

TRIAL REGISTRATION

The protocol for this study is registered with the current controlled trials registry; registry number: ISRCTN43896775.

Randomised controlled trial of intravenous maintenance fluids

AIM

Traditional paediatric intravenous maintenance fluids are prescribed using hypotonic fluids and the weight-based 4:2:1 formula for administration rate. However, this may cause hyponatraemia in sick and post-operative children. We studied the effect of two types of intravenous maintenance fluid and two administration rates on plasma sodium concentration in intensive care patients.

METHODS

A Factorial-design, double-blind, randomised controlled trial was used. We randomised 50 children with normal electrolytes without hypoglycaemia who needed intravenous maintenance fluids for >12 h to 0.9% saline (normal saline) or 4% dextrose and 0.18% saline (dextrose saline), at either the traditional maintenance fluid rate or 2/3 of that rate. The main outcome measure was change in plasma sodium from admission to 12-24 h later.

RESULTS

Fifty patients (37 surgical) were enrolled. Plasma sodium fell in all groups: mean fall 2.3 (standard deviation 4.0) mmol/L. Fluid type (P = 0.0063) but not rate (P = 0.12) was significantly associated with fall in plasma sodium. Dextrose saline produced a greater fall in plasma sodium than normal saline: difference 3.0, 95% confidence interval 0.8-5.1 mmol/L. Full maintenance rate produced a greater fall in plasma sodium than restricted rate, but the difference was small and non-significant: 1.6 (-0.7, 3.9) mmol/L. Fluid type, but not rate, remained significant after adjustment for surgical status. One patient, receiving normal saline at restricted rate, developed asymptomatic hypoglycaemia.

CONCLUSION

Sick and post-operative children given dextrose saline at traditional maintenance rates are at risk of hyponatraemia.

[Post-tonsillectomy hyponatremia: a posible lethal complication]

Death following tonsillectomy in children is very rare. It is most commonly due to bleeding or aspiration. But, there is another potentially lethal complication following the pediatric tonsillectomy, post-surgical hyponatremia. Acute hyponatremia can lead to catastrophic neurological sequelae. Although this cmplication is not related to the surgical technique, it is potentially life-threatening. The most important factor for hospital acquired hyponatremia is the administration of excessive amounts of hypotonic fluid in situations in wich antidiuretic hormone (ADH) is secreted for non osmotic reasons. We will discuss the etiology and pathophysiology of post-operative hyponatremia. We expect that fatal post-operative hyponatremia can be avoided in pediatric tonsillectomy patients.

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.

Carbamazepine-related hyponatremia following cardiopulmonary bypass

A 67-year-old man on long-term carbamazepine therapy underwent elective coronary artery bypass grafting. Following an initially uncomplicated recovery, he developed symptomatic hyponatremia. The symptoms and biochemical abnormality improved after gradual discontinuation of carbamazepine. We discuss the association between carbamazepine and hyponatremia and the causes of hyponatremia after cardiopulmonary bypass. Surgeons should consider stopping carbamazepine before operations with cardiopulmonary bypass.

Acute symptomatic hyponatremia complicating invasive cardiac procedures: a report of three patients

Hyponatremic encephalopathy is a well-known complication of surgical procedures. This syndrome has not been described in the cardiology literature. We report three patients who developed acute hyponatremia with life-threatening encephalopathy following an invasive cardiac procedure. Diagnosis and treatment were delayed because of a lack of awareness for the syndrome among the cardiology staff. The diagnosis of hyponatremia should be suspected in any patient who develops behavioral or neurological manifestations following an invasive cardiac procedure. Prompt diagnosis and treatment are essential to avoid permanent neurological damage or death.

Hyponatraemia: biochemical and clinical perspectives

Hyponatraemia is a common bio-chemical abnormality, occurring in about 15% of hospital inpatients. It is often associated with severe illness and relatively poor outcome. Pathophysiologically, hyponatraemia may be spurious, dilutional, depletional or redistributional. Particularly difficult causes and concepts of hyponatraemia are the syndrome of inappropriate antidiuresis and the sick cell syndrome, which are discussed here in detail. Therapy should always be targeted at the underlying disease process. 'Hyponatraemic symptoms' are of doubtful importance, and may be more related to water overload and/or the causative disease, than to hyponatraemia per se. Artificial elevation of plasma sodium by saline infusion carries the risk of induction of osmotic demyelination (central pontine myelinolysis).

Significant hyponatremia following DDAVP administration in a healthy adult

We report the development of significant hyponatremia (121 mEq/L) following three daily intravenous doses of desmopressin acetate (DDAVP; 18 micrograms; 0.3 micrograms/kg) in a healthy adult with moderate von Willebrand's disease. Previous reports suggest that clinically important hyponatremia due to DDAVP administration only occurs in the very young, those receiving hypotonic intravenous fluids or those given multiple frequent (e.g., every 8-12 hours) doses of DDAVP. None of these conditions was present in this case. Consideration should be given to monitoring serum sodium levels and fluid balance in patients receiving more than a single dose of DDAVP, even in the absence of previously reported risk factors for the development of hyponatremia.

Postoperative fatigue

Uncomplicated major surgery is followed by a pronounced increased feeling of fatigue extending throughout the first month in about one-third of patients. Postoperative fatigue correlates with the degree of surgical trauma but is not related to duration of general anesthesia and surgery or to preoperative nutritional status, age, or sex. Fatigue also correlates with postoperative deterioration in nutritional parameters and impaired adaptability of heart rate during exercise. Furthermore, a postoperative decrease in muscle force and endurance is related to postoperative fatigue, whereas psychological factors are of minor importance. These findings suggest postoperative fatigue to be mediated by the endocrine-metabolic response to surgery, impaired nutritional intake, or immobilization, but the relative role of these factors remains to be established. Until then, therapeutic measures against the development of postoperative fatigue should aim at reducing the surgical stress response, effective treatment of pain to facilitate mobilization, and exercise to increase postoperative nutritional intake.