Maintenance Rate
--
mL/hr
| 1st Hour | 2nd Hour | 3rd Hour | |
|---|---|---|---|
| NPO Deficit | -- | -- | -- |
| Maintenance Rate | -- | -- | -- |
| 3rd Space | -- | -- | -- |
| TOTAL | -- | -- | -- |
Trinooson, C., & Patel, N. G. (2023). Fluids, electrolytes, and goal-directed therapy. In S. Elisha, J. S. Heiner, & J. J. Nagelhout (Eds.), Nurse anesthesia (7th ed., pp. 376-399). Elsevier.
Wilson, R. P. (2023). Blood and blood component therapy. In S. Elisha, J. S. Heiner, & J. J. Nagelhout (Eds.), Nurse anesthesia (7th ed., pp. 400-410). Elsevier.
Krogh, M. A. (2023). Obesity and anesthesia practice. In S. Elisha, J. S. Heiner, & J. J. Nagelhout (Eds.), Nurse anesthesia (7th ed., pp. 1092-1108). Elsevier.
Kim, T. K., Obara, S., & Johnson, K. B. (2025). Basic principles of pharmacology. In M. A. Gropper, N. H. Cohen, L. I. Eriksson, L. A. Fleisher, S. Johnson-Akeju, & K. Leslie (Eds.), Miller's anesthesia (10th ed., pp. 347-371). Elsevier.
Sheets, S. A. (2023). Preoperative evaluation and preparation of the patient. In S. Elisha, J. S. Heiner, & J. J. Nagelhout (Eds.), Nurse anesthesia (7th ed., pp. 336-375). Elsevier.
Fernandez-Bustamante, A., & Bucklin, B. A. (2024). Anesthesia and obesity. In B. F. Cullen, M. C. Stock, R. Ortega, C. W. Connor, & N. Nathan (Eds.), Barash, Cullen, and Stoelting's clinical anesthesia (9th ed., pp. 3814-3876). Wolters Kluwer.
Hourly maintenance is 4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the second 10 kg, and 1 mL/kg/hr for every kg above 20. A 70 kg adult works out to 40 + 20 + 50 = 110 mL/hr.
The fasting deficit is the maintenance rate multiplied by the hours NPO. Half of the deficit is replaced in the first hour of the case and one quarter in each of the next two hours, on top of ongoing maintenance and third space losses.
Surgical trauma pulls fluid out of the intravascular space. Typical estimates run 1-2 mL/kg/hr for superficial procedures, 2-4 for minimal trauma such as herniorrhaphy, 4-6 for moderate cases like laparoscopic abdominal surgery, and 6-8 for severe open abdominal cases.
Estimated blood volume is about 70 mL/kg in adults, 80-90 mL/kg in term neonates, and 90-100 mL/kg in preterm neonates. Maximum allowable blood loss is EBV x (initial Hct - lowest acceptable Hct) / initial Hct, using the initial hematocrit in the denominator. For a 70 kg adult run from a Hct of 42% down to 21%: EBV = 4,900 mL and MABL = 4,900 x (42 - 21) / 42 = 2,450 mL. Blood loss beyond MABL is replaced with blood at 1:1; below it, crystalloid at 3:1 or colloid at 1:1.
With a BMI over 30, calculate maintenance and third space needs on ideal body weight rather than total body weight, and estimate blood volume on lean body weight plus 20%.
Trinooson & Patel (2023), Fluids, electrolytes, and goal-directed therapy (Ch. 21); Wilson (2023), Blood and blood component therapy (Ch. 22); Krogh (2023), Obesity and anesthesia practice (Ch. 48). In Elisha, Heiner, & Nagelhout (Eds.), Nurse anesthesia (7th ed.). Elsevier.