Vorbereitung

http://www.healthsystem.virginia.edu/internet/anesthesiology/Dept-Info/Education/Lectures/blood.cfm

http://www.muhealth.org/~md2003/draft7/2-12pediactric.doc

http://www.muhealth.org/~md2003/draft7/

Pipettierschema

I. Total Body Water (TBW): 60% of weight in men, 50-55% in women

a. Intracellular: 2/3rds of TBW

b. Extracellular: 1/3rd of TBW

i. Interstitial space: 3/4ths of extracellular; 16% TBW

ii. Vascular: 1/4th extracellular, 4% TBW

iii. Osmolarity: 2 x [Na] + (glucose/18) + [BUN]/2.8 ~ 290mOsm

II. Fluid Balance

a. Normal: 30ml/kg/day of water lost through urine (15ml), stool (3ml), sweat (0-1.5ml) and lungs/skin (10ml).

b. Abnormal:

i. Require 500ml more if febrile; give hypotonic replacement

ii. Abdominal and thoracic surgery requires 1,000ml replacement by LR or normal saline to replace 3rd spacing

iii. 3rd spacing resolves on POD #3 and later

iv. TPN causes osmotic diuresis; don’t confuse high urine output with high fluid status

III. Volume Depletion

a. Clinical diagnosis:

i. 1st signs: skin turgor, dry mucous membranes, oliguria

ii. later signs: mental status changes

b. Treatment: give fluids

i. LR for most causes of isotonic losses (intestinal, biliary, pancreatic, 3rd spacing)

ii. Gastric losses best treated with isotonic crystalloid; LR has inadequate Cl to deal with hypochloric, hypokalemic metabolic alkalosis of persistent vomiting

iii. Glucose solutions not a good idea for volume replacement: can cause osmotic diuresis if too much is given

Durchführung

Vorhandene Flüssigkeiten:

Bezeichnung	Glukose	Na	Cl	K	Ca	Mg	HCO3	kcal /l
D5W	50 mg							170
D10W	100 mg							340
NS (0,9% NaCl)		154	154
1/2 NS (0,45% NaCl)		77	77
1/4 NS (0,25% NaCl)		38	38
LR (Ringer-Laktat)	130	110	4	3			27	< 10

Situation: Erhalt des gegenwärtigen Flüssigkeitsstatus

• Wer?
  • gesunde Patienten, die Wasser, Natrium, Chlorid und Dextrose (D5) zum Erhalt der Urinproduktion benötigen
  • gesundes Herz, gesunde Nieren und Lungen
  • ohne Fieber, ohne Drainagen, ohne Blutungen, ohne Durchfall
    
• Was?
  D5W und 25 meq/l Natrium (1/4 NS) und 20 meq/l Kalium
  
  
• Wie viel?
  30 ml/kg/Tag als Wasserverlust durch Urin (15 ml), Stuhl(3 ml), Schweiß (0 - 1,5 ml) und Lungen/Haut (10 ml)
  1200 - 1500 ml/Tag Urin, 200 - 400 ml/Tag Schweiß, 500 ml/Tag Atmung, 100 ml/Tag Stugl
  Elektrolytbedarf: K^^ = 1-2 meq/kg, Na^^ = 2-3 meq/kg, Cl^-^ = 1-2 meq/kg
  
  100 ml/kg/d (4 ml/kg/h) für die ersten 10 kg = 1000 ml
  50 ml/kg/d (2 ml/kg/h) für die zweiten 10 kg = 500 ml (Beispiel: 12 kg Patient => 1100 ml/d bzw. 45 ml/h)
  20 ml/kg (1 ml/kg/h) für jedes weitere kg (Beispiel: 70 kg Patient => 2500 ml/d bzw. 100 ml/h; den entsprechenden Salzbedarf liefert 1/4 NS + 20 meq KCl/l)
• Besonderheiten:
  • weniger Flüssigkeit/kg für adipöse Patienten
  • für präoperative Nüchternzeit wird auch 2 ml/kg/h benutzt, 50% werden in der 1. Stunde, 50% in den folgenden 2h ersetzt

Situation: Maintenance plus

• Wer?
  • für gut hydrierte Patienten mit vermehrten Verlusten
  • Fieber: jedes Grad Celsius erhöht den Flüssigkeits-und Sauerstoffbedarf um 13%
  • 3. Raum: bei Trauma- oder chirurgischen Patienten (Ödeme), Verbrennungen, Pleuraergüsse
    ...
  • Blutverlust: Jeder ml Blutverlust muß durch 3 ml isotone i.v.-Flüssigkeit ersetzt werden (da 2/3 aus dem Gefäßsystem verloren gehen)
  • Operationen: IN: i.v.-Flüssigkeit, OUT: Blutverlust, Urin; Defizit durch NS oder LR ersetzen (über 24h)
• Was?
  

  • Third spacing means there is an increase in the patient’s weight as well as total body water and salt, but the fluid in the 3rd space is not supporting perfusion. You still have partially empty blood vessels. • In the abdomen, fluid goes to 1) peritoneal cavity (ascites), 2) bowel lumen, 3) bowel wall “boggy” • Other losses: chest tubes, NG tubes/gastrostomy, drains, diarrhea, vomiting • Chest tubes – fluid has composition of blood/serum; replace with LR • NG tube/gastrostomy – drainage color is important to determine tonicity • Clear drainage (only contains spit and gastric acid) is replaced with 1/2NS + 10-20 cc KCl/L • Green/yellow drainage (biliary secretions, pancreatic bicarb.) Any secretions past the pylorus are isotonic and replaced by LR. • Third space losses are isotonic (so if you try to replace the fluid with 1/4 NS, your serum Na+ will decrease). The replacement must also be isotonic. [Na+] = 140, Osmo = 280 • After surgery, you must give extra fluid to replace what is being third spaced. Fluid loss depends on length of surgery. • First 2 -3 days post-op - give a lot more fluid to maintain urine output. • At about 36-48 hrs, the patient starts to mobilize the third space fluid, and suddenly the patient is urinating much more fluid than what’s put in. If third space losses aren’t replaced, urine output will be compromised. • So in non-surgical patients, weight gain is seen as a bad thing, but in surgical patients, it’s expected and if not seen, probably means they’re not getting enough fluid. Isotonic Solutions: 1) Nl saline (NS) where Na+=Cl- 2) Lactated Ringers (LR) which is more like serum w/ 4meq/L of K+; repletes plasma

   So, in maintenance plus patient we need to start with maintenance fluids (i.e. ¼ NS + 20 of KCl) and at the same time replace the fluids that are being lost which are mainly isotonic (i.e. full strength NS or LR) Therefore in order to accommodate both objectives, the fluid to be used should be ½ NS with 20 of KCl at a rate of 1-2X maintenance rate (150%) to take care of the third spacing. Also make sure to monitor urine output and electrolytes periodically.

  Fluid = D5/1/2NS + 20 KCl/L Rate = 150% maintenance

  Do not exceed 2x’s maintenance rate b/c glucosuria will result. This creates an osmotic diuresis and invalidates the urine output as an indicator of perfusion/volume. It is best to make the best-estimated adjustment and see what the pt does w/ it, how their kidneys adjust.

  In general 7-9L of fluid are produced ( 1L of oral, 2L gastric secretions, 1L bile, 2L pancreatic fluid, 1-3L small bowel fluids) with the majority reabsorbed in the bowel. It is easy to understand why cholera with decreased transit time can create such a problem. There are exceptions to this rule at both ends of the age spectrum. First, premature infants and newborns are born wet, with increased total body water and Na+ b/c it takes time for the breast milk to let down. Fluids must be balanced carefully in the preemie b/c they also have greater evaporative losses. The second exception is found in older folks who have problems maintaining fluid balance as well as those with primary cardiac, pulmonary and/or renal disease. It is important to fluid resuscitate patients before taking them to OR b/c anesthetics decrease vascular tone. Order a 20cc/kg/hr bolus until specific gravity < 1.015. Replace the deficit, which is usually > than you thought. The way patients compensate for hypovolemia is vasoconstriction so if you have a patient who is hypovolemic, but he’s compensated, by reducing perfusion to the periphery, when you give him an anesthetic, his blood pressure will drop, and the body will then kick out catechols and steroids. This stress response actually increases the amount of third spacing, increases the amount of fluids required, increases how sick the patient is, increases length of stay in the hospital, increases the time it takes to mobilize the third space fluid. So when writing an op note, it is important to include estimated blood loss and how much fluid the patient received during the case.

3) Deficit (dehydration/hypovolemia)

Most dehydration is isotonic. • Hypotonic fluid administration -> hyponatremia; therefore, not the treatment of choice. • Administer LR (isotonic solution) – also helps metabolic acidosis due to peripheral anaerobic metabolism • Rapid resuscitation with 5% dextrose in the maintenance IV fluids prevents ketosis. too much dextrose in rapid resuscitation -> osmotic diuresis -> hyperglycemia, glycosuria

Sign and Sx of hypovolemia include: • orthostatic BP changes, particularly in the elderly. Children and healthy young adults have good vascular tone and can maintain blood pressure. Therefore, if the blood pressure drops, it indicates that the patient is in serious trouble. Monitoring the heart rate in these patients is more valuable than blood pressure. In older patients, blood pressure should be monitored because it is slower to drop. • tachycardia, hint: sick pts are tachycardic • urine output • increased U/A specific gravity, nl am = 1.020, daytime = 1.010, whereas anything > 1.020 indicates a dry pt • dry mucous membranes • decreased fontanelles • sunken eyes

Administering NS and RL- A bolus is used when the fluid is needed as quickly as possible. Give enough fluid to make them pee and then switch to Maintenance Plus fluids. If the pt is hypothermic, warm the fluid. The speed of resuscitation depends on whether the patient will be admitted to the hospital or OR.

Child: 20 cc/kg bolus (1-2L). Repeat bolus 3X before giving blood. In a young, otherwise healthy patient, however, urine output should improve and the pulse rate will decline if you’re doing the right thing. Adult: 1000 cc/kg bolus (In an adult trauma, you should rip in 1L; if not stabilized, give a 2nd liter.) Repeat bolus 2X before giving blood. For a 70 yo COPDer or pt w/ previous MIs, put in a Swan Ganz catheter to monitor the filling pressures of the left side of the heart while fluid resuscitating them, because their urine volume may not indicate their hydration state.

Examples 1. 15 kg child coming in for surgery  give maintenance therapy (1/4 NS)  1000 cc + 250 cc = 1250 cc/day = 50 cc/hr (actually 53.25, but don’t worry about being exact)

2. 10 kg 1 year-old post-op -> give 1000 cc -> 40 cc/hr (maintenance rate) 1 ½-2X -> 60-80 cc/hr of D5 ½ NS (if electrolytes nl) add K+ if trauma or burn use LR if pt needs 2X maintenance rate or is hyponatremic b/c of risk of metabolic acidosis & hyperglycemia

3. 20 kg trauma pt w/ increased HR, poor capillary refill, increased specific gravity  20 cc/kg bolus -> 400 cc/hr LR; check pulse and urine output

Tidbits from last year: *Fluid Overload can result from running fluids to fast; rare if well monitored *Vasopressors- Do not give vasopressors in the volume depleted b/c if the vessels are not full, there is nothing for the heart to pump. “Must fill up the tank.” *D5W- no sugar in fluids b/c they are running so fast, the pt will be hyperglycemic. *Renal considerations- In pts with renal failure infuse NS, b/c RL has K+ which will increase with renal failure. *Head injury- fluid restrict for 1st 24h when the brain characteristically swells, watch pt, mobilize 3rd spacing. *The pulse is a good indication as to how sick the patient is! *In the OR – Watch for anesthetics because they dilate peripheral vessel and create hypovolemia with a drop in blood pressure causing your body to pump out catechols and steroids which will increase 3rd spacing and recovery time.

Autor

Tobias Schäfer

Erstellt

08.11.2004

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