Describe the fluid and blood product management for this neonate intraoperatively.
Intraoperative fluid requirements can be divided into three basic areas: maintenance fluid, preoperative fluid deficit replacement, and replacement of third-space and blood losses.
Maintenance fluid volume is determined based on weight as shown in Table 65.2.
Maintenance requirements for water, electrolytes, and glucose have been standardized using metabolic rates. This has led to D5 0.2% NS being used as standard maintenance fluid. Several factors including increased temperature and increased metabolic rate can increase maintenance fluid requirements. Balanced salt solutions are standard replace-ment fluids used in the operating room and in the older infant are used for maintenance also. Glucose-free fluids are generally used in the operating room for several reasons. Most notably, intraoperative hypoglycemia is very rare in older infants and children. Hyperglycemia, on the other hand, is associated with adverse outcomes related to the brain, heart, and intestines during ischemic events. However, neonates and specifically preterm infants are at risk for hypoglycemia and may require glucose infusions during the intraoperative period. In these situations, only the maintenance fluids should contain glucose.
This patient presenting to the operating room would not have a fluid deficit, as it would have already been cor-rected during the preoperative preparation. Typically, the fluid deficit results from prolonged fasting times. This deficit is determined by multiplying the hourly maintenance fluid requirement by the number of hours that the patient has been fasting. The deficit is replaced with a balanced salt solution over a 3-hour period: 50% infused in the first hour and 25% infused the second and third hours.
The magnitude of third-space losses depends on the site and extent of surgical manipulation. The guidelines for third-space loss replacement recommend 8–15 mL/kg/hr during extensive intra-abdominal surgery. A neonate with gastroschisis could potentially require 5–10 times this amount for third-space replacement. Third-space loss should be replaced with a balanced salt solution without glucose. The state of hydration needs to be continually assessed.
Prior to any procedure where blood loss is expected, the anesthesiologist should determine the approximate blood volume and estimate the allowable blood loss (ABL). It is important to remember that the ABL is an estimate, as many variables are considered when determining the level of anemia that each patient will tolerate. ABL is calculated as follows:
EBV = estimated blood volume (see Table 65.3)
Hcti = initial hematocrit
Hctp = allowable perioperative hematocrit
Hctav = average of Hcti and Hctp (Hcti + Hctp/2).
When determining the estimated allowable periopera-tive hematocrit, the affinity for oxygen of hemoglobin F must be considered. In the neonate with high levels of hemoglobin F, oxygen delivery at the tissue level is low despite potentially high hemoglobin levels (P50 approxi-mately 19 mmHg.)
Replacement of blood and fluid is critical in small neonates since their total blood volume is so small. Blood loss needs to be replaced as it occurs to maintain normovolemia. It can be replaced with crystalloid (3 times the amount of blood loss) or with colloid or blood in equal volumes.
Once a decision is made to transfuse, every effort should be made to limit exposures to multiple donors. In pediatric patients, this means dividing a single donor unit into a “pedi pack” (1 unit divided into multiple 50–100 mL parts) so that the same donor unit can be administered at differ-ent times. A general rule is that the increase in hematocrit with red blood cell administration will be approximately the same as the milliliters per kilogram infused.