The 10 Great Teachings of Clinical Fluid Therapy
D. John Doyle MD PhD
Fluid therapy involves covering fluid losses
due to bleeding, "third-spacing", maintenance
needs and other causes. This involves the
administration of crystalloids or colloids
(pentastarch, albumin, fresh frozen plasma
[FFP] and blood). Plasma volume expansion
to correct for losses is the primary objective
of fluid therapy in the perioperative setting,
although corrections of coagulopathies,
oliguria and electrolyte disorders are other
Large volume fluid resuscitation [“massive fluid resuscitation”] is often necessary in situations such as severe trauma. Under these circumstances a number of physiological derangements may occur with continuing crystalloid and nonblood colloid resuscitation. Hypofibrinogenemia develops first followed by other coagulation factor deficits. Later, thrombocytopenia contributes to coagulation derangements. FFP is the primary intervention to treat abnormal bleeding due to replacement of massive blood loss with plasma-poor red cells. The need for FFP is guided by the visual monitoring of clotting at the surgical site as well as by PT/PTT/ INR monitoring. The development of thrombocytopenia is a highly individual phenomenon, so the use of platelets should be guided by repeated platelet counts where practical. Finally, severe anemia may follow unless red blood cells are eventually administered.
 You need a good IV.
 Don't cool the patient with room-temperature fluids given in large volume - use a fluid warmer.
 Keep an image of the volume status from urine output and clinical behaviour. For serious resuscitation a CVP line is nice to have. A PA catheter is even nicer. Don’t forget about the expected finding of low urine sodium with hypovolemia.
 The [instantaneous] fluid delivery rate [ml/hr] = fluid deficit correction rate + fluid maintenance requirement + “third-space” correction rate + blood loss correction rate. This is how fast one should generally run the IV [containing a crystalloid such as Ringer’s lactate]. This amount varies with time.
 The fluid deficit correction rate for the first two hours [only] is given below.
Fluid deficit correction rate [ml/hr] [first two hours only] = estimated deficit [ml] / 2,
estimated presurgical fluid deficit [ml] = Hours NPO without IV fluid replacement x estimated fluid maintenance requirement [ml/hr] [discussed below]
 Estimated fluid maintenance requirements are [“4-2-1” rule]:
4 ml/kg/hr for first 10 kg 2 ml/kg/hr for next 10 kg 1 ml/kg/hr thereafter
Example - 70 kg adult situation: 40 + 20 + 50 = 110 ml/hr estimated fluid maintenance requirement. If NPO for 10 hours without an IV, presurgical fluid deficit is then 1100 ml. This presurgical fluid deficit should be corrected over 2 hours by administering 550 ml/hr of crystalloid for two hours and then stopping. [You must also continue to administer the ongoing maintenance requirement, and corrections for third spacing and blood loss.]
 The “third-space” correction rate may be estimated roughly as follows:
Small surgical procedures: 1 to 3 ml/kg/hr [such as hand surgery or tubal ligations]
Medium procedures: 3 to 6 ml/kg/hr [such as a cholecystectomy]
Large procedures: 6 to 10 ml/kg/hr [such as colon resection or a Whipple operation]
 Replace blood losses four-to-one with crystalloid to start. When you have corrected for blood losses to the extent of 15 - 20 % of the estimated blood volume [70 ml/kg], consider achieving volume expansion by adding a colloid on a 1-to-1 basis, using 10% pentastarch (Pentaspan) or 5% albumin. Administer FFP if there is concern about the development of a coagulopathy due to diluted clotting factors [PT, PTT, INR elevated]. Administer platelets is there is concern about the development of a coagulopathy due to dilutional thrombocytopenia. If coagulation is seriously impaired due to low fibrinogen levels, administer cryoprecipitate or call a hematologist for help.
 Administer packed cells [or autologous blood] when the patient’s hematocrit falls below a “transfusion trigger” or if the patient is symptomatic or encountering clinical problems from severe anemia.. Up till the mid 1980s the “transfusion trigger” was taken to be 10 g/dl. Today the usual answer is between 6 and 8 in otherwise healthy patients and between 8 and 10 in patients with coronary artery disease or similar “high-risk” patients.
 Remember that all the above are just a starting point; they should not necessarily be followed exactly, but be guided by local teaching, clinical experience and collegial advice. Also, this approach would not be expected to be especially useful in the early treatment of burn victims, where the “Parkland Burn Formula” is often used.
(PARKLAND FORMULA: Lactated Ringers 2 ml/kg x % body burned. Give 50% in 1st 8 hrs since burn, then 25% over each of 8 hours for the next 16 hrs.)
SOME FLUID THERAPY LINKS