Optimizing fluid resuscitation in hypertrophic pyloric stenosis

Infographic · Oct 2018 · 2 min read

In brief

This retrospective study of 505 infants with hypertrophic pyloric stenosis demonstrates that initial chloride level predicts fluid resuscitation needs: patients with Cl ≤97 mmol/L require two 20ml/kg boluses 73% of the time, while those with Cl <85 need three boluses at the same rate. Protocol-driven resuscitation based on presenting chloride can reduce unnecessary lab draws and expedite operative intervention.

Initial chloride ≤97 mmol/L predicts need for 2+ fluid boluses with 73% accuracy; chloride <85 predicts need for 3+ boluses with 73% accuracy.
Administer empiric boluses based on presenting chloride rather than waiting for repeat labs: 2×20 ml/kg if Cl ≤97, 3×20 ml/kg if Cl <85.
HPS patients with electrolyte abnormalities have longer LOS (2.6 vs 1.9 days) and require more fluid (106 vs 91 ml/kg/day) than those with normal labs.
Chloride is more sensitive than bicarbonate or potassium for predicting resuscitation needs in HPS; use it to guide initial fluid strategy.
Protocol-driven bolusing reduces unnecessary lab draws and delays to surgery while maintaining safe electrolyte correction before anesthesia.

Written by the GCMD Library team from the infographic.

Clinical decision flowchart on a teal background showing three pathways branching downward from chloride and bicarbonate thresholds. Each pathway leads to illustrated IV fluid bags indicating the number of 20mL/kg normal saline boluses to administer. The Journal of Pediatric Surgery logo appears in the top right corner.

Background

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.

Methods

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

Results

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 4.1 kg, p < 0.01). Length of stay was significantly longer in the patients with electrolyte abnormalities, 2.6 vs 1.9 days (p < 0.01). Fluid given was higher over the entire hospital stay for patients with abnormal electrolytes (106 vs 91 ml/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−80 mmol/L and the need for 3 or more boluses AUC was 0.71. Modifying the parameters to initial Cl− ≤97 mmol/L and 2 boluses AUC was 0.65. A patient with an initial Cl−85 will need three 20 ml/kg boluses 73% (95% CI 52–88%) of the time. A patient with an initial Cl− ≤97 will need two 20 ml/kg boluses at a rate of 73% (95% CI 64–80%).

Conclusion

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 20 ml/kg saline boluses separated by an hour prior to rechecking labs in patients with initial Cl− value ≤97 mmol/L. If the presenting Cl−<85 three boluses of 20 ml/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.

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