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INTRODUCTION

FOCUS POINTS

  1. The Holliday-Segar formula, known as the “4-2-1” rule, is used to calculate the rate of maintenance fluids.

  2. There is a wide variety of intravenous fluids that can be used as maintenance fluids and it is important to know their composition to select the adequate one depending on the patient’s comorbid condition and the surgical procedure.

  3. Important formulas to remember when taking care of pediatric patients include the estimated blood volume and allowable blood loss formulas.

  4. Adverse reactions to blood transfusions include non-immune-mediated and immune-mediated reactions.

  5. The acid-base balance in the body is regulated by the lungs and the kidneys, via buffer systems.

  6. It is essential to be able to interpret the results of an arterial blood gas to diagnose acidosis or alkalosis and differentiate between a metabolic or respiratory etiology.

Fluid management in the operating room is as important as the medications administered to achieve anesthesia and analgesia. Fasting times can significantly affect infants and toddlers, and subsequently lead to hemodynamic instability under general anesthesia. Furthermore, in the pediatric population, physiological buffer systems are still immature making the patient more prone to acid-base disturbances. This chapter will review the main principles of fluid management, the different strategies for fluid repletion, including the transfusion of blood products, the physiology behind acid-base homeostasis, and the diagnostic approach to acid-base disturbances.

FLUID MANAGEMENT

One of the first considerations when evaluating a pediatric patient who presents to the preoperative area is to inquire about fasting times. This allows the anesthesiologist to calculate the fluid deficit already present prior to induction. The Holliday-Segar formula, developed in the 1950s,1 is used to calculate the rate of maintenance fluids; it is more commonly known as the “4-2-1” rule. For the first 10 kg of a patient’s weight, the patient requires 4 mL/kg/h. For the next 10 kg, the patient should receive an additional 2 mL/kg/h. Lastly, for each kilogram thereafter, 1 mL/kg/h should be administered in addition to the 60 mL/h calculated for the first 20 kg. This holds true for an otherwise healthy patient, or even a patient with comorbid conditions that are medically optimized, presenting for an elective procedure. In a patient who is acutely sick and likely dehydrated, other clinical signs can guide fluid resuscitation perioperatively. There are several criteria obtained from a physical examination that can help classify a patient’s status into mild, moderate, or severe dehydration (Table 12-1). Fluid resuscitation can then be carried out accordingly prior to induction, then continued intraoperatively to achieve hemodynamic stability.

Table 12-1Clinical Criteria to Classify Dehydration2

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