Fluid maintenance Done by : Ala’a khresat

The total fluid requirement is composed of : compensatory intravascular volume expansion (CVE) ..• maintenance fluids ..• preoperative deficits ( NPO ,, GI losses ,, blood loss ) ..• Intra operative surgical Losses ( evaporation ,, blood loss ,, 3de space loss)

1) compensatory intravascular volume expansion (CVE) Intravascular volume must usually be supplemented to compensate for the venodilation and cardiac depression caused by anesthesia Increasing cardiac preload by infusing fluid intravascularly to return stroke volume to an acceptable range . 5 mL/kg of balanced salt solution (Ringer's lactate) should be introduced before or simultaneous with the onset of anesthesia. •Postoperatively ; venodilation and cardiac depression rapidly subside when administration of the anesthetic is stopped ** Note : Patients with impaired cardiac or renal responses may then become acutely hypervolemic !!

2) Maintenance therapy: replaces the ongoing daily losses of water and electrolytes occurring via physiologic processes (urine, sweat, respiration, and stool), which normally preserve homeostasis. Maintenance requirements vary depending on the patient's underlying clinical status and setting especially in postoperative or hospitalized children due to changes in their physiologic responses (eg, excess antidiuretic hormone [ADH] secretion). Maintenance >> in all NPO pt .

In surgery the patient must be NPO, there for fluid maintenance very important. When patient in fasting status there is no input , but we have output (urination , gi secretions , respiration …ect ))) • If we don’t maintain sufficient amount of fluid the patient at risk of complications like acute renal failure and hypovolemia. NPO will cause fluid and electrolytes deficit not just water loss from the body .

Goals for perioperative fluid therapy Optimal perioperative fluid therapy requires an understanding of the changes that occur in the volume and composition of the body fluid compartments Intravenous fluids are used to replenish fluid losses while maintaning ** intravascular volume ( which is essential for adequate perfusion of vital organs ) ** cardiac preload ** oxygen-carrying capacity ** coagulation status ** acid-base balance ** electrolyte balance

Maintenance fluid requirements for any body weight can be calculated using the :"4-2-1" rule for hourly fluid requirements or the "100-50-20" rule for daily fluid requirements

Example, 5 kg …..5*4=20ml/hour 15kg….40+(2*5)=50ml/hour >> ml of water

Rule of 4 -2 -1 :

For example, a 75 kg adult will require:Per hour: 10 kg x 4 ml/hr = 40 ml/hr 10 kg x 2 ml/hr = 20 ml/hr 55 x 1 ml/hr = 55 ml/hr Total : 75 kg 115 ml/hr So if we have an adult male patients that weighs 75 kg, what is the maintenance therapy plan for him? You tell me… = 10x4 + 10x2 + 55 *1 = 115 ml/hour x 24 hours = 2760 ml per day. 24 h >> help us in fasting pt and in calculating input and urine output negative ( input> output ), positive ( output> input ) > in renal problem

Electrolytes : Normal range of sodium >> 135-145 mEq/ L . Normal range of potassium >> 3.5-5.3 mEq/L . Why sodium and potassium so important ? Regulate nerve and muscle function and maintain acid – base balance and water balance + cardiac conduction. Daily requirements of : Na : 2-3meq/kg /day K : 1-2meq/kg/day CL : 1.5 mEq/Kg /day we managed the >> water and the electrolyte loss by either the type of solution or adding electrolytes to the solution. Just for knowledge: 1 mmol of sodium or potassium = 1 mEq , 2 mmol of Ca+2 = 1 mEq

Treatment of hyperkalemia IV calcium gluconate Insulin Ventolen >> Salbutamol. Used a second line management in the treatment of hyperkalaemia when a glucose / insulin infusion is inappropriate or has been unsuccessful in lowering serum potassium levels. Salbutamol reduces serum potassium levels by increasing the shift of extracellular potassium into the intracelluar space.

The most common maintenance fluid is D5 ½ NS with 20 or 40 mEq KCL (because as we said normal saline doesn’t have potassium) But usually its 20 mEq because with 40 you have higher risks on the cardiac conducting system then after 12 h we re messure electrolytes and according to the results we make decisions. 20 mEq of potassium = 1500 mg (daily requirement 3.5-4.6 g) 5 mEq of sodium = 100 mg (daily requirement of < 2g) So if we have an adult male patients that weighs 70kg, what is the maintenance therapy plan for him? You tell me… = 10x4 + 10x2 + 50x1 = 110 ml/hour x 24 hours = 2640 ml/ day of water so roughly 2.5 liters Na = 1.5 mEq x 70 = 105 mEq/day K= 1 x 70 = 70 mEq/day So our choice is D5 ½ NS + KCL

3) Deficit : definition: it’s the fluid that has already been lost, Difference between defect and replacement >> replacement which refers to both the deficit + ongoing losses + future losses Same as maintenance therapy formula, it will give a rough estimate because in reality we have renal conservation so the deficit will be less. difference btw maintenance and deficit>> 1)Deficit> normal maintenance rate * length of the fast ( hours). 2) the fluid infusion rate for normal patients should be set to deliver 3-4 times the maintenance rate .so When replacing the deficit we give an infusion rate higher than the normal maintenance rate until the deficit is corrected ,,Once its corrected you go back to the same rate as before .

Now what if the duration of fasting is unknown or it is known but the patient has abnormal fluids losses (sweating, diarrhea, ascites), what will we do? We will approximate bases on clinical data (physical exam) This is effected by the chronicity of the condition so the longer the worse the deficit So we look at signs of hypovolemia……skin turgor ,hydration of mucous membranes , fullness of a peripheral pulse , the resting heart rate , blood pressure and the orthostatic changes from the supine to sitting or standing positions and urine output.

Deficit ,continue 1. as a result of a period of fasting ( NPO deficit ) : In the absence of oral intake ; fluid and electrolyte deficits can  rapidly develop as a result of continued urine formation, gastrointestinal secretions , and insensible losses ( from the skin and lungs ) .. can be calculated by multiplying the patient's hourly maintenance requirements by the number of hours fasted --->The deficit can be estimated by multiplying the normal maintenance rate by the length of the fast,,,, For the average 70-kg person fasting for 8 h, this amounts to (40 + 20 + 50) mL/h × 8 h, or 880 mL. In fact, the real deficit is less as a result of renal conservation.  2. preoperative losses from the gastrointestinal tract ( eg. vomitting or diarrhea ) ,,   best replaced with a crystalloid of similar composition (0.9% NS or Ringer’s lactate ) bleeding, vomiting, nasogastric suction, diuresis, are often contributory. Losses (actually, redistribution;) due to fluid sequestration by traumatized or infected tissues, coagulopathy- related occult hematoma formation, or ascites can also be substantial. Increased insensible losses due to hyperventilation, fever, and sweating are often overlooked. 3. Blood loss

more rational approach is to diagnose that we actually have a deficit then just treat based on restoration of vital signs and maintaining a good urine output (.5-1 ml/kg per hour)in adult and correction of base deficit if present To achieve this usually the main stay is 1-2 liters of isotonic fluid, 1 liter bolus/hour followed by a continuous infusion and monitoring The fluid use is isotonic crystalloid given ,depending on the particular electrolyte profile

Replacement : Replacement of fluids can be pre or intra operatively When replacing fluids we have to know from which compartment is the fluid lost (blood, GI, thirst space) so we can give the correct type of fluid needed

4) Intra operative replacement   1. Evaporation :This can occur during body cavity surgery ,, most significant with large wounds, especially burns, and are proportional to the surface area exposed and to the duration of the surgical procedure. and here evaporation from exposed viscera is entirely water, but the electrolyte is left behind, leading to a need for free water ..  2. Blood loss :       Depends upon the type and site of surgery ..   3. Third space loss : -->

2) Blood loss Most common way to estimate blood loss during surgery is to measure blood in: Suction container Visually (soaked sponges (4x4, 10 ml), soaked lap (100-150ml))  even serial hematocrit can be done in long surgeries And like we know each ml of blood needs about 3 to 4 ml of crystalloids or 1 ml of colloid More accurate estimates are obtained if sponges and “laps” are weighed before and after use, which is especially important during pediatric procedures. Blood loss we replace with crystalloids or colloids to maintain intravascular volume ,,Now if the danger of anemia overweighs the risk of transfusion, at this point further blood loss is replaced with transfusion of rbcs to maintain hemoglobin( or hematocrit) And like we explained before depending of type of surgery and wound and so on we replaced fluids lost during surgery

we prefer to start with crystalloids in replacement of blood loss bcz they're safer .. we don't prefer to use colloids bcz of the side effects ( eg. coagulopathy ,, anaphylaxis .. ) .. we don't prefer to transfuse blood bcz of the complications until the danger of anemia outweighs the risks of transfusion ( transfusion point )then we should transfuse blood ( red blood cells to maintain hemoglobin concentration or hematocrit at certian level )..

third space or thirst space : first ( intra vascular ) and second ( interstitial ) spaces are the constituents of the ECF which are normal physiological compartments ‘’third space" its referes to space other than ICF and ECF, examples :     ** peritoneal cavity ( eg. ascites ) ..     ** pleural cavity ( eg. pleural effusion ) ..    ** lumen of the gastrointestinal tract ( as in a patient with ileus ) ..   ** swelling of the tissues after surgical trauma or burns .. When too much fluid from the intravascular space moves into the interstitial or third space (non functional areas) that causes serious problems; hypotention, reduced CO, edema. The estimation fluid loss is very hard here, if we have ascites we can do aspiration or maybe nasogastric tube in ileus >> we know amount and composition of that fluid . Mangement by 1)colloid fluid like albumin >> fluid to intra vascular 2) diuretic >> exertion by renal and we must replace the loss.

Example: 70 kg patient with ileus , lost 2L of fluid in a nasogastric aspirate, aspirate has 240 mEq of sodium and 20 mEq of potassium What is the replacement therapy and what type of fluid would u use? Lets take it step by stepA..we start by the maintenance which like we calculated is approximately 2.5 L We add these to the 2 liters he lost so now we need 4.5 L Now the sodium like we said in maintenance 105 mEq add the 240 lost so we need 345 mEq Potassium lost is 20 so also add 105 we need 125 mEq of potassium >> so we can start with 2 bags of normal saline ( has about 300 mEq of sodium) Then 1 liter of ¼ NS about 39 mEq of sodium And add 1 liter of D5 with 120 kcl (6 bags each 20 mEq

According to truma Because redistributive and evaporative losses are primarily related to wound size and the extent of surgical dissections and manipulations, procedures can be classified according to the degree of tissue trauma. These additional fluid losses can be replaced according to whether tissue trauma is minimal, moderate, or severe. These values are only guidelines, and actual needs vary considerably from patient to patient.

INTRAVENOUS FLUIDS Done by Marah Saeed

Types of fluid : >> crystalloids>> Isotonic ( eg.>> .9% normal saline ,Ringer’s lactate ) >> hypotonic >> Those that contain less or no electrolytes >> but contain glucose to ensure that they have an osmolality similar to plasma (eg, 5% dextrose, 0.25% NS, 0.45% NS, and 4% glucose + 0.18% NS)  >> hypertonic > 3% Saline , 5% Saline , 10% Dextrose in Water (D10W) ,5% Dextrose in 0.9% Saline , 5% Dextrose in 0.45% saline , 5% Dextrose in Lactated Ringer’s >> colloids >> Natural (human albumin) >> Artificial (gelatins, dextrans and hydroxyethyl starches)

1) Crystalloids : Crystalloids are aqueous solutions of low molecular weight ions ,with or without glucose . That are often considered as the initial resuscitation fluid in patients with hemorrhagic and septic shock, in burn patients, in patients with head injury (to maintain cerebral perfusion pressure), and in patients undergoing plasmapheresis and hepatic resection

C. Hypertonic solutions used recently A. Isotonic, Those that contain electrolytes in a similar composition to plasma, have an osmolality similar to plasma,  B.hypotonic    C. Hypertonic solutions used recently For losses primarily involving water, replacement is hypotonic solutions also known as maintenance type solutions like: Dextrose solution 5% If losses involve both water and electrolytes replacement is with isotonic electrolytes solutions or replacement type solutions like: ringer’s lactate

A) Isotonic solutions Because most intra operative fluid losses are isotonic (water and solutes) ,replacement-type solutions are generally used. These fluid are isotonic to ECF ,after IV administration they distribute rapidly into ECF compartment and are appropriate when the main fluid deficiency derives from this source >> for example > GI losses or intra –operative losses other than bleeding >> so 1littere of these fluid administered intravenously will increase the intra vascular volume by about 220 ml after equilibrium (complete within 30-60 minutes) and this are also useful as plasma volume expanders but it must be remembered that only about ¼ remains in the circulating volumes after redistribution.

Normal saline or sodium chloride 0.9% is a mixture of sodium chloride in water that is slightly hypertonic and contains more chloride than ECF, when given in large volumes, it produces hyperchloremic metabolic acidosis ??? because of its high chloride content and lack of bicarbonate In addition, chloride-rich crystalloids such as normal saline may contribute to perioperative acute kidney injury. Therefore, we prefer balanced salt solutions for most intraoperative uses. Normal saline is the preferred solution for 1.hypochloremic metabolic alkalosis 2.diluting packed red blood cells prior to transfusion and diluting of drug.

0.9% NS is distributed throughout the intravascular and interstitial volumes ( ECF compartment) in proportion to their size  •After 15-30 min, only 25-30% of the volume administered remains intravascular, i.e. limited intra-vascular half-life. Therefore, if such a fluid is used to restore the circulating volume, three to four times the deficit will need to be given.  Commonly used for electrolyte replacement The preferred fluid for hypovolaeminc resuscitation in many countries Useful for replacing electrolyte-rich GI losses

Lactated Ringer’s solution Ringer's lactate solution or (Hartmann's solution), is a mixture of sodium chloride, sodium lactate, potassium chloride, and calcium chloride in water Physiological solutions Osmolality is similar to ECF and thus useful for restoring extracellular volume  First-line replacement therapy in the perioperative period and for emergency fluid resuscitation  •May reduce iatrogenic hyperchlorarmic metabolic acidosis, associated with use of higher chloride-containing solutions>> note>> plasma bicarbonate concentration decrease as chloride concentration increases so as mechanism of action in this solution that rapidly metabolized in the liver this generates bicarbonate ions ,bicarbonate cannot be directly added to the solution Because it is unstable (tend to precipitate)>>> used as a buffer. Hypotonic and provide approximately 100 ml of free water per liter and tending to lower serum sodium In most settings , the benefits of replacing such as balance( mimics plasma composition) when large volume are needed outweigh the risk.

Uses of ringer lactate 1.It is used for replacing fluids and electrolytes in those who have low blood volume or low blood pressure. 2.It may also be used to treat metabolic acidosis in cases other than those caused by lactic acidosis 3.And to wash the eye following a chemical burn Safe in emergency cases so it’s the first line in emergency

Other types of solutions: Plasmalyte : is a family of balanced crystalloid solutions with multiple different formulations available It closely mimics human plasma in content of electrolytes, osmolality and pH that’s why it is a replacement type solution These solutions also have additional buffer capacity and contain anions such as acetate ,gluconate and also contain magnisum

B.Hypotonic solutions > Five percent dextrose in water (D5W) : Five percent dextrose in water (D5W) It is a hypotonic ,isosmotic solution that doesn’t contain electrolytes>> 5 g of dextrose /100 ml water . It’s important to note that although this fluid is hypotonic , it still iso osmotic ,that is ,it doesn’t cause hemolysis like what happens if you injected only water. Dextrose is rapidly metabolized in the body such as dextrose solution is equivalent to administering water which distributes rapidly throughout the entire body water (i.e. ECF and ICF), and so it provides a convenient way of giving free water. But less than 10% will remain intravascular, and thus, they have no role as plasma expanders >> no use as a resuscitation fluid to expand the intra vascular volum Glucose-containing solutions are a way of treating dehydration as a result of water losses. Sugar-containing solutions provide 4kcal/g glucose (glucose 5% contains 5g/100ml), a considerable energy source, but their potential deleterious osmotic effects limit use

Dextrose solution is equivalent to administering water that’s why 1.It is used for replacement of pure water deficits 2.as a maintenance fluid for patients on sodium restriction (hypernatremia) >> because it contains sugar>> take water with it and water take the sodium 3.It prevents the catabolic state (hypoglycemia and ketosis ) that follows prolonged fasting( eg.keeping the pt NPO before surgery) >> so use in maintenance. ***More concentrated dextrose solutions (10%,20% and 50%) are available but their use is limited to the management of diabetic patients and patients of hypoglycemia >> these solutions are irritant to veins.

Hypotonic solution Important: Watch out for depleting the circulatory system of fluid since you are trying to push extracellular fluid into the cell to re-hydrate it. Never give hypotonic solutions to patient who are at risk for increased cranial pressure (can cause fluid to shift to brain tissue), extensive burns, trauma (already hypovolemic) etc. because you can deplete their fluid volume

C. Hypertonic solutions Less commonly used There sodium concentrations range from 250-1200 mEq/L >> the greater the sodium concentration,the lower the total volume required for satisfactory resuscitation. This difference reflects the movement due to osmotic forces of water from intracellular space very cautiously….most likely to be given in the ICU due to quickly arising side effects of pulmonary edema/fluid over load). In addition, it is prefered to give hypertonic solutions via a central line due to the hypertonic solution being vesicant on the veins and the risk of infiltration. Hypertonic 3% saline is employed in therapy of severe symptomatic hyponatremia

Mainly >> isotonic solutions for replacement Hypotonic solution for maintenance

Effect of large volume crystalloid infusion
 
1- extravascular accumilation in skin, connective tissue, kidney. 
2-inhibition of GI motility 
3-delay healing of anastomosis
 4-large volume ,Rapid infusion cause hypercoagulability

colloids colloids Are those containing high mw substances that exert an oncotic pressure Primarily, they expand the intravascular volume and can initially be given in a volume similar to the estimated deficit to maintain the circulating volume . when colloid solution is administered the solution remained in the circulation until the colliod particle are removed (predominantly by the reticuloendothelial system ) after which it distributes into the ECF volume because it’s also contains electrolytes Good resuscitation fluids (plasma fluid expanders) >> all the volume administered stays in the circulation,,colloids solutions are replaced in a 1:1 ratio in contrast with crystalloid solutions which approximately require 3or more times the volume of fluids lost

indications for colloids include 1.fluid resuscitation in patients with severe intravascular fluid deficits (eg, hemorrhagic shock) prior to the arrival of blood for transfusion 2.fluid resuscitation in the presence of severe hypoalbuminemia or conditions associated with large protein losses such as burns. (Replacing an intravascular volume deficit with crystalloids generally requires three to four times the volume needed when using colloids , this justifies their indication for the use where more than 3_4 liters of crystalloid solution has been injected Most solutions-remain in the circulation for between 6 and 24 hours.

The 2 categories of colloids are 1.Natural (human albumin) 2.Artificial (gelatins, dextrans and hydroxyethyl starches)

Albumin Albumin : Half life =1.6 hours in plasma Stays in intravascular space solution for the treatment of hypovolaemia >> Expands volume 5x in 30 minutes and its effect lasts 1-2 days and as a salt-poor 20% solution for the treatment of hypoalbuminemia  •It is manufactured from whole blood fractionation •5% solution isotonic 10% and 25% hypertonic . Side effects : 1.volume overload 2.Fever ?? Pyrogens in albumin 3.Defects in hemostasis

Advantages: Natural colloid: As albumin is a natural colloid it is associated with lesser side-effects like pruritus, anaphylactic reactions and coagulation abnormalities compared to synthetic colloids. Degree of volume expansion: 25%Albumin has a greater degree of volume expansion as compared to rest of colloids. 5% albumin solution has a similar degree of volume expansion as compared to hetastarch but greater than gelatins and dextrans. Other benefits: Albumin acts a principal binding protein of endogenous and exogenous substances. It also possesses antioxidant effects. Albumin being negatively charged protein contributes to the formation of normal anion gap, influencing the acid-base status.

Dextran Branched polysaccharides derived from bacterial action on sucrose •High molecular weight polysaccharide Dextran 70 “ MW 70000”: (Better volume expander).Dextran 40: “MW 40000”  (Improves blood flow through microcirculation). 40000 >coagulation effect than dextran 70000 ) 10% solution in NS or D5W •SE: anaphylaxis, coagulopathy ,renal failure •is used as a volume expander but also reduces blood viscosity, von Willebrand factor antigen, platelet adhesion, and red blood cell aggregation ,that’s why it is used by microsurgeons to improve microcirculatory flow and decrease risk of microthrombus formation Associated with anticoagulation.*Use for vascular surgery – prevent thrombosis.*Can cause mild-moderate anaphylactoid and anaphylactic reactions*Infusions exceeding 20 ml/kg/d can interfere with blood typing, renal failure, prolong Beeding Time (Dextran 40).  •Initially 20ml/kg for the 1st 24 hours and 10ml/kg thereafter for 5 days only! 

hydroxyethyl starch (the best colloid) is highly effective as a plasma expander and is less expensive than albumin. Allergic reactions are rare, but anaphylactic reactions have been reported >> hypersensitivity, mild influenza-like symptoms, tachycardia, bronchospasm and non-cardiogenic pulmonary edema , Hetastarch can decrease von Willebrand factor antigen levels, may prolong the prothrombin time, and has been associated with hemorrhagic complications, Also  Decrease in hematocrit , It is potentially nephrotoxic

Side effects and precautions Anaphylaxis with the gelatins  •coagulopathy and bleeding with starched, in addition to itching after their use  There is no limit on the volume of gelatins that can be given (provided that haemoglobin concentration is maintained!) whereas starches are limited to 30-50ml/kg

Differences between colloids and crystalloids 1.Colloids are more expensive than crystalloids 2.Colloids have higher molecular weight 3.Half life of crystalloids is between 15 to 20 minutes while colloids last 2-3hrs 4.Colloids act as plasma expanders