Optimizing fluid resuscitation in hypertrophic pyloric stenosis

Hypertrophic pyloric stenosis (HPS) is the most common diagnosis requiring surgery in infants. Electrolytes are used as a marker of resuscitation for these patients prior to general anesthesia induction. Often multiple fluid boluses and electrolyte panels are needed, delaying operative intervention. We have attempted to predict the amount of IV fluid boluses needed for electrolyte correction based on initial values.

A single center retrospective review of all patients diagnosed with HPS from 2008 through 2014 was performed. Abnormal electrolytes were defined as chloride <100mmol/L, bicarbonate ≥30mmol/L or potassium >5.2 or <3.1mmol/L. Patients with abnormal electrolytes were resuscitated with 20ml/kg saline boluses and continuous fluids at 1.5 times maintenance rate.

During the study period 542 patients were identified with HPS. Of the 505 who were analyzed 202 patients had electrolyte abnormalities requiring IV fluid resuscitation above maintenance, and 303 patients had normal electrolytes at time of diagnosis. Weight on presentation was significantly lower in the patients with abnormal electrolytes (3.8 vs 4.1kg, p<0.01). Length of stay was significantly longer in the patients with electrolyte abnormalities, 2.6 vs 1.9days (p<0.01). Fluid given was higher over the entire hospital stay for patients with abnormal electrolytes (106 vs 91ml/kg/d, p<0.01). The number of electrolyte panels drawn was significantly higher in patients with initial electrolyte abnormalities, 2.8 vs 1.3 (p<0.01). Chloride was the most sensitive and specific indicator of the need for multiple saline boluses. Using an ROC curve, parameters of initial Cl(-)80mmol/L and the need for 3 or more boluses AUC was 0.71. Modifying the parameters to initial Cl(-) ≤97mmol/L and 2 boluses AUC was 0.65. A patient with an initial Cl(-)85 will need three 20ml/kg boluses 73% (95% CI 52-88%) of the time. A patient with an initial Cl(-) ≤97 will need two 20ml/kg boluses at a rate of 73% (95% CI 64-80%).

Children with electrolyte abnormalities at time of diagnosis of HPS have a longer length of stay; require more fluid resuscitation and more lab draws. This study reveals high sensitivity and specificity of presenting chloride in determining the need for multiple boluses. We recommend the administration of two 20ml/kg saline boluses separated by an hour prior to rechecking labs in patients with initial Cl(-) value ≤97mmol/L. If the presenting Cl(-) <85 three boluses of 20ml/kg of saline separated by an hour are recommended. If implemented these modifications have potential to save time by not delaying care for extraneous lab results and money in the form of fewer lab draws.