Fluid Management

1. Fluid Management Jeffrey Groom, PhD, CRNADirector and Clinical Associate ProfessorNurse Anesthetist ProgramFlorida International University

2. Goal of perioperative fluid management The goal of perioperative fluid management is to provide the appropriate amount of parenteral fluid to maintain adequate: • intravascular fluid volume, • left ventricular filling pressure, • cardiac output, • systemic blood pressure, • and ultimately, oxygen delivery to tissues.

3. Rational approach to fluid management In addition to surgical considerations (blood loss, evaporative loss, third spacing), certain conditions and changes that occur during the perioperative period can make the management of fluid balance a challenge, including preoperative: • fluid volume status, • preexisting disease states, • and the effect of anesthetic drugs on normal physiology

4. Management of fluid therapy • Management of fluid therapy may influence intraoperative and postoperative morbidity and mortality. • Providing sufficient intravascular fluid volume is essential for adequate perfusion of vital organs. • Although quantitative considerations are of primary concern, oxygen carrying capacity, coagulation, and electrolyte and acid-base balance are also of critical importance.

5. Preoperative assessment of intravascular fluid volume Preoperative assessment of intravascular fluid volume is important before induction of anesthesia. • Common causes of preoperative hypovolemia: • Bowel preparations, vomiting, diarrhea, diaphoresis, hemorrhage, burns, and inadequate intake • Redistribution of intravascular fluid volume without evidence of external loss is another important cause of preoperative volume depletion. • Examples: patients with sepsis, adult respiratory distress syndrome, ascites, pleural effusions, and bowel abnormalities. • Often, these processes are accompanied by increased capillary permeability resulting in loss of intravascular fluid volume to interstitial and other fluid compartments.

6. Evaluation of intravascular fluid volume • Evaluation of intravascular fluid volume relies on indirect measurements such as systemic blood pressure, heart rate, and urine output because measurements of fluid compartments are not readily available. • Even with sophisticated monitoring techniques (pulmonary artery catheters, arterial oxygen saturation), the adequacy of intravascular fluid volume replacement and tissue oxygen delivery to individual vital organs cannot be precisely determined. • For these reasons, clinical evaluation of intravascular fluid volume is necessary.

7. Clinical Estimation of Intravascular Fluid Volume

8. INTRAVASCULAR FLUID VOLUME STATUSAND ANESTHETIC TECHNIQUE • Induction of anesthesia with thiopental leads to a decrease in venous return. • Induction of anesthesia with propofol produces a decrease in systemic vascular resistance, cardiac contractility, and preload. • Ketamine produces increases in systemic blood pressure, heart rate, and cardiac output through stimulation of the sympathetic nervous system and inhibition of norepinephrine reuptake. • Direct myocardial depressant effects of ketamine may be unmasked by exhaustion of catecholamine stores (congestive heart failure, end-stage shock) and result in paradoxical decreases in blood pressure when ketamine is administered

9. INTRAVASCULAR FLUID VOLUME STATUSAND ANESTHETIC TECHNIQUE • Neuromuscular blocking drugs, though generally devoid of direct cardiovascular effects, can lead to histamine release (Sux, Atracurium) and decreased systemic vascular resistance or produce venous pooling because of loss of muscle tone. • Isoflurane, desflurane, and sevoflurane all decrease systemic vascular resistance and mildly depress myocardial contractility. In addition, institution of positive-pressure ventilation of the patient’s lungs reduces preload and is particularly likely to decrease systemic blood pressure in hypovolemic patients.

10. INTRAVASCULAR FLUID VOLUME STATUSAND ANESTHETIC TECHNIQUE • Regional Anesthesia (Spinal & Epidural) AKA Neuraxial blockade - block sympathetic nervous system fibers innervating arterial and venous vascular smooth muscle, causes vasodilatation, pooling of blood, and decreased venous return to the heart. • May cause significant changes in systemic blood pressure, especially in intravascularly depleted patients. • These effects are often mitigated by fluid administration before the institution of regional anesthesia.

11. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits, • Replacement of normal losses (maintenance requirements) • Replacement of surgical wound (“third-space”) losses • Replacement of surgical wound (bleeding) losses

12. PERIOPERATIVE FLUID THERAPY:QUALITATIVE CONSIDERATIONS Crystalloid solutions – NS, LR, Plasma-lyte, Dextrose solutions • NS - large volumes can lead to a hyperchloremic-induced non-gap metabolic acidosis • LR - large volumes can lead to an increased bicarbonate production from the metabolism of lactate and induce metabolic alkalosis • LR and Plasma-Lyte contain potassium and should be used with caution in hyperkalemic patients. • Calcium in LR prohibits its use in the presence of citrated blood products. • Dextrose-containing solutions should be avoided because hyperglycemic-induced hyperosmolality, osmotic diuresis, and cerebral acidosis are known complications. • Infusions of total parenteral nutrition solutions should be continued during anesthesia and surgery to prevent hypoglycemia; or alternatively administer dextrose-containing infusion. In either case, monitor intra op blood glucose.

13. PERIOPERATIVE FLUID THERAPY:QUALITATIVE CONSIDERATIONS • Colloid solutions – albumin, hydroxyethyl starch, and dextran • Albumin (5% or 25%) is purified from human plasma • there is no known risk of transmission of hepatitis B or C or HIV. • However, because albumin is a blood product, Jehovah’s Witness patients may object to its use for religious reasons. • The half-life of albumin in plasma is approximately 16 hours, with about 90% of the dose remaining in the intravascular space 2 hours. • Hydroxyethyl starch (hetastarch) is a semisynthetic colloid synthesized from amylopectin • 6% high-molecular-weight hetastarch in saline (Hespan) • 6% high-molecular-weight hetastarch in balanced electrolytes (Hextend) • The half-life for 90% of hydroxyethyl starch particles is 17 days. • Dextran is a semisynthetic colloid biosynthesized from sucrose • Based on differing molecular weights, dextran 70 is generally preferred for volume expansion, whereas dextran 40 is thought to improve blood flow in the microcirculation, presumably by decreasing blood viscosity. • Hypersensitivity reactions, including anaphylaxis, have been reported with albumin, hydroxyethyl starch, and dextran. • Considerably more expensive than crystalloids.

14. PERIOPERATIVE FLUID THERAPY:QUALITATIVE CONSIDERATIONS COAGULATION ABNORMALITIES • Bleeding associated with the use of the synthetic colloids has been widely reported. • Dextran 70 and, to a lesser extent, dextran 40 produce a dose-related reduction in platelet aggregation and adhesiveness. • Hydroxyethyl starch can lead to a reduction in factor VIII and von Willebrand factor, impairment of platelet function, and prolongation of the partial thromboplastin time. • Coagulation studies and bleeding times are not generally significantly affected after infusions of up to 1 L. • However, these colloids are best avoided in patients with a known coagulopathy. Colloid versus Crystalloid Solutions • Numerous comparison studies with NO distinct advantages • Because colloids are more expensive and do not have the same safety profile as crystalloids, it is hard to justify their use outside situations in which rapid intravascular fluid volume expansion is needed.

15. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits, • Replacement of normal losses (maintenance requirements) • Replacement of surgical wound (“third-space”) losses • Replacement of surgical wound (bleeding) losses

16. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits Sometimes called the “4-2-1 Rule” Examples: _____ ml/hr minimum maintenance req 60 kg = ______ 100 kg = _____ 200 kg = _____

17. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits Sometimes called the “4-2-1 Rule” Quick Version for patients over 20kg is to take weight (kg) plus 40 (ml/hr)Hourly Maintenance Fluid Rate ___kg + 40ml = ____ ml/hrEx 120 kg pt 120kg + 40 = 160 ml/hr

18. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy based on: • The predicted daily maintenance fluid requirements for healthy adults may exceed 2500ml/day including 20 mEq/L Sodium and 15-20mEq/L Potassium • Insensible loss (diaphoresis, respiration, etc.) may exceed 1000ml/day • Urinary losses to maintain renal function average 1000ml/day, GI losses 200ml/day

19. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits Hourly Maintenance Fluid Requirement XHours NPO Fluid Deficit Examples: _____ ml Estimated Fluid Deficit 60kg/8hr = ___ 100kg/10hr = ___ 200kg/12hr= ___

20. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits usually over 3 hours 1stHR ½ 2nd HR ¼ 3rd HR ¼ Examples: _____ ml Estimated Fluid Deficit 1000 ml deficit = ___ ml 1st HR ___ ml 2nd HR ___ ml 3rd HR

21. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: • Replacement of preexisting fluid deficits Abnormal fluid losses (vomiting, diarrhea, preoperative bleeding), occult losses (ascites, infected tissues), and insensible losses (fever, sweating, hyperventilation) must not be overlooked in the preoperative correction of fluid deficits so that the hypotension and hypoperfusion that can occur during induction of anesthesia can be minimized.(Clinical estimation - No formula for replacement amount) The fluid used for replacement should be similar in composition to the fluid lost (Crystalloids).

22. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: 2. Replacement of normal losses (maintenance requirements) _____ ml/hr minimum maintenance requirements(Administered With or Without Surgery Losses)

23. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: 3. Replacement of surgical wound (“third-space”) losses

24. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: 4. Replacement of surgical wound (bleeding) losses Replace 1 mL of blood loss with 3 mL crystalloid solution Examples: 100ml blood = ___ml cryst 500ml blood = ___ml cryst

25. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS Perioperative fluid therapy includes: 4. Replacement of surgical wound (bleeding) losses Replace 1 mL of blood loss with 3 mL crystalloid solution 4x4 = 10 ml blood Lap = 100-150 ml

26. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS • Continually record ongoing estimates of surgical blood loss. • Include: Measurement of blood in the surgical suction container; • Estimate: occult bleeding into the wound or under surgical drapes • Estimate: blood on surgical sponges and laparotomy pads (“laps”) • Use of irrigating solutions may also complicate the estimates. • Serial hematocrit values reflect the ratio of blood cells to plasma, not blood loss. • Typically, surgeons and anesthesia providers underestimate actual blood loss. • Clinical signs such as tachycardia are insensitive and nonspecific. • Decreasing urine output, decline in arterial pH, and a rising base deficit may be manifested only when tissue hypoperfusion has become moderate to severe. • Therefore, visual estimation of continual blood loss is mandatory to guide fluid therapy and transfusion. Replace blood loss with isotonic crystalloid solution at 3ml : 1ml blood loss ratio, -OR- milliliter-per-milliliter replacement with colloid or blood

27. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS

28. PERIOPERATIVE FLUID THERAPY:QUANTITATIVE CONSIDERATIONS * * Hourly Maintenance Fluid Rate (4-2-1 Rule ml/hr)

29. PERIOPERATIVE FLUID THERAPY:EXAMPLE 1 (insensible Loss Rate)

30. PERIOPERATIVE FLUID THERAPY:EXAMPLE 2 (Maintenance Rate)

31. PERIOPERATIVE FLUID THERAPY:EXAMPLE 1 (insensible Loss Rate)

32. PERIOPERATIVE FLUID THERAPY:EXAM (insensible Loss Rate)

33. Transfusion Considerations • Considered on a case by case basis • Blood loss should be replaced with crystalloid or colloid solutions to maintain intravascular fluid volume until the danger of anemia or depletion of coagulation factors necessitates the administration of blood products. • Below a hemoglobin level of 7 g/dL, resting cardiac output has to increase greatly to maintain normal oxygen delivery to tissues. Therefore, blood loss should be replaced with transfusion of erythrocytes to maintain a hemoglobin concentration between 7 and 8 g/dL. A level of 10 g/dL is generally desired for patients with significant cardiac or pulmonary disease. • The most common intraoperative coagulopathy is dilutional thrombocytopenia, which occurs with either large-volume blood product transfusion or crystalloid/ colloid administration. • Factor deficiency is less common in the absence of hepatic dysfunction because stored blood retains 20% to 30% activity of factors VII and VIII, which is sufficient for coagulation.

34. Calculating Allowable Blood Loss • Estimated Blood Volume (EBV) and ABL • Blood Volume as a function of total body water • Composition decreases with age • Premature 100-120cc/kg • Newborn 80-90cc/kg • Infant (age 3-12 months) 75-80cc/kg • Adult male 70cc/kg • Adult female 65cc/kg

35. Calculating Allowable Blood Loss Hematocrit (70kg male initial crit 45% target 30%) • If you know what the preoperative HCT is, • Calculate MABL to a minimum target HCT: MABL = (EBV) x (Starting HCT – Target HCT) Starting HCT MABL = (70cc/kg x 70kg) x (45%-30%) 45% MABL = (4900) x (15)/45 = 1633ml Estimate that PT will be at approximate Hct of 30% at a blood loss of 1633 ml

36. Calculating Allowable Blood Loss Hematocrit (100kg male initial crit 35% target 25%) MABL = (EBV) x (Starting HCT – Target HCT) Starting HCT MABL = (70cc/kg x 100kg) x (35%-25%) 35% MABL = (7000) x 10)/35 = 2000ml Estimate that PT will be at approximate Hct of 25% at a blood loss of 2000 ml

37. Basics of AnesthesiaBlood Therapy Chapter 24 • Emergency Transfusion – Order of preference • Type and Screen vs Type and Cross • Decision to transfuse • Blood components – PRBCs, Acute Loss, Complications, FFP • Transfusion reactions • Autologous Blood – PreDeposit, Salvage, Dilution • Basic nursing procedures to administer blood products – Safety checks, IV Setup, Administration, Documentation

38. CASE - 40 yo 220lb hernia 10hr npo • Convert pounds to kilograms • Calculate maintenance • Calculate deficit • Calculate 3rd Space replacement requirement • Include possible need to replace blood loss

39. CASE - 40 yo 220lb hernia 10hr npo

40. CASE - 40 yo 220lb hernia 10hr npo Urine Output

41. Calculating allowable blood loss Hematocrit (70kg female initial crit 45% target 30%)

42. Exam I • Surgical Services (5% slides/Stoelting Ch3) • Preanesthesia Assessment (30% slides/text) • Surgical Patient Positioning (30% slides/text) • Fluid Management (35% slides/text)