Plasma and renal clearances of lactated Ringer's solution in pediatric and adult patients just before anesthesia is induced.

BACKGROUND

Lactated Ringer's solution is most widely used in children, but little is known about how children who are scheduled for surgery handle a fluid load when compared to adults. This study explores whether a more cautious regimen for the administration of lactated Ringer's is warranted in children awaiting minor surgery when compared to adults.

METHODS

Plasma dilution (based on hemoglobin), urinary excretion, and volume kinetics were used to assess the disposition of an i.v. infusion of 10 ml x kg(-1) of lactated Ringer's solution over 20 min in 14 pediatric patients (4 years of age, average body weight 15 kg) and in 14 adult patients scheduled for similar minor pelvic surgery. Experiments were performed after premedication, but before anesthesia was induced.

RESULTS

Plasma dilution was less pronounced in the pediatric patients (P < 0.03) who also had excreted more of the infused fluid within 90 min than the adults (43% vs 18%, P < 0.03). After correction for body weight, their plasma clearance was 4 times higher (P < 0.02) and the renal clearance of lactated Ringer's solution 7 times higher (P < 0.001) than those of the adults. The more rapid turnover of fluid in the children might be explained by a shorter period of preoperative fasting (6 vs 10 h) and/or by physiological differences attributable to age.

CONCLUSION

The plasma and renal clearances of lactated Ringer's solution were higher in children with a body weight of about 15 kg in comparison with adults. Therefore, children in this age group may receive at least the same amounts of fluid per kilo body weight during preparation for surgery as the amounts recommended for adults.