3. fluid electrolyte in anesthesia
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1
Algemene Principes van Vochtbeleid
M. Verhaegen,Hasanul ArifinAnesthesiologyUZ KU Leuven
2
Intraoperative IV Fluid Therapy: Historical Perspective (1)
Fluid restriction Postoperative Salt Intolerance
(Coller et al, Ann Surg 1944, 119: 533-541) “No isotonic saline solution or Ringer’s solution
should be given during the day of operation and during the subsequent first two postoperative days”
3
Intraoperative IV Fluid Therapy: Historical Perspective (2)
Trauma/surgery: large fluid deficits Acute Changes in Extracellular Fluid
Associated with Major Surgical Procedures(Shires et al., Ann Surg 1961, 154: 803-810) Major surgery is associated with significant
functional extracellular fluid volume deficits Replace with large volumes of balanced
electrolyte solutions
Artificiële colloïden en indicaties albumine Bloedproducten Hemodilutie en autotransfusie Electrolietenafwijkingen Het zuur-base evenwicht Vochtbeleid
Vochtcompartimenten Distributie van water over de vochtcompartimenten Electrolieten samenstelling
Het perioperatieve vochtbeleid
Body Fluid Compartments
Total body water = 60 % of body weight (BW)
2/3
Intracellular water= 40 % of BW
1/3
Extracellular water
= 20 % of BW
Plasma (5 % of BW)
Extracellular water
= 20 % of BW
% of body weight
70 kg male (L)
Total body water
60 42
Intracellular 40 28
Extracellular 20 14
Intravascular
5 3.5
Interstitial 15 10.5Sendak in Principles and Practice of Anesthesiology (2nd ed), Longnecker et al.,
7
Extracellular Extravascular Water
Interstitial fluid and lymph Rapid exchange (with plasma) Slow exchange
Bone water «Cavitary» fluids: transudates of plasma
E.g. peritoneal, pericardial, pleural Transcellular fluids: active transport mechanisms
E.g. salivary, hepatic, biliary, pancreatic, gastrointestinal intraluminal, mucosal, dermal, intraocular, intrathecal
Age- and Gender-related Changes in Total Body Water
Total body water (%)
Age Male Female
1 mo 76 76
1 – 12 mo 65 65
1 – 10 yr 62 62
10 – 16 yr 59 57
17 – 39 yr 61 50
40 – 59 yr 55 47
> 60 yr 52 46Hays: Dynamics of body water and electrolytes (1980)In: Maxwell et al (eds): Clinical disorders of fluid and electrolyte metabolism
Relationship Between Body Habitus and Total Body Water in Adults
Total body water (%)
Build Male Female
Thin 65 55
Average 60 50
Obese 55 45Principles and Practice of Anesthesiology (2nd ed), Longnecker et al.
10
Electrolytes:Physiologic and Chemical Activity
Number of particles/unit volume (m)moles / liter of solution
Number of osmotically active particles/unit volume (m)osmoles / liter of solution
Number of electric charges/unit volume (m)equivalents / liter of solution
11
Body Fluids: Ionic Composition
Electrical neutrality In any fluid compartment or intravenous
solution the number of milliequivalents of cations is balanced by precisely the same number of milliequivalents of anions
Chemical combining activity (milliequivalents) 1 equivalent of an anion is the amount
which can combine with 1 g of hydrogen
Body Fluid Compartments: Composition
Intracellular Extracellular
Intravascular Interstitial
Sodium (mEq/l) 10 145 142
Potassium (mEq/l) 140 4 4
Calcium (mEq/l) <1 3 3
Magnesium (mEq/l) 50 2 2
Chloride (mEq/l) 4 105 110
Bicarbonate (mEq/l) 10 24 28
Phosphorus (mEq/l) 75 2 2
Protein (g/dl) 16 7 2
Body Fluid Compartments: CompositionElectrolyte Plasma
(mEq/L)
Plasma water (mEq/L)
Interstitial fluid (mEq/L)
Intracell. fluid (mEq/kg
H2O)
CATIONS
Sodium 142 152 145 10
Potassium 4 4 4 156
Calcium 5 5 3 3
Magnesium 3 3 1 26
Total 154 164 153 195
ANIONS
Chloride 103 109 114 2
Bicarbonate 27 29 30 10
Phosphate 2 2 2 108
Sulfate 1 1 1 20
Organic acids
5 6 5
Protein 16 17 1 55
Total 154 164 153 195
Gibbs - Donnan Principle
Equilibrium
1A 2A 1B 2B
5 Pr-
5 Na+
10 Cl-
10 Na+
5 Pr-
5 Na+
4 Cl-
4 Na+
6 Cl-
6 Na+
•Na+1B x Cl-
1B = Na+2B x Cl-
2B
•Electrical neutrality
Non-diffusible protein anions
Plasma water (mEq/l)
Interstitial fluid (mEq/L)
CATIONS
Sodium 152 145
Potassium 4 4
Calcium 5 3
Magnesium 3 1
Total 164 153
ANIONS
Chloride 109 114
Bicarbonate 29 30
Phosphate 2 2
Sulfate 1 1
Organic acids 6 5
Protein (org. anions) 17 1
Total 164 153
141 147
16
Water Distribution and Movement
Hydrostatic forces Mechanical pressure generated by the heart Weight of blood within the vasculature
Osmotic forces The movement of water is governed by the
compartmental concentrations of osmotically active substances, predominantly electrolytes
Extracellular: sodium, chloride, bicarbonate Intracellular: potassium, magnesium,
phosphate, protein
17
Osmotic Pressure
Osmotic pressure is the hydrostatic pressure that must be applied to the solution of greater concentration to prevent water movement across a semi-permeable membrane separating two aqueous solutions of unequal concentration
Osmotic pressure is dependent on the number of osmotically active molecules in solution
18
Osmotic Pressure 1 Osmole (Osm)
= 1 gram-molecular weight (1 M) of a nondissociating compound and consists of 6.023 x 1023 molecules
Osmolarity (mOsm / L) = the number of osmoles of solute per liter of solution (solvent
plus solute)
Osmolality (mOsm / kg H2O) = the number of osmoles of solute per kilogram of solvent (water)
Osmotic pressure = osmolality x 19.3 (mmHg)
Intracellular Extracellular
10 mEq/l 142 mEq/l
Sodium balance
20
Plasma Osmolality
[Gluc] [BUN]Sosm (mOsm/kg H2O) = (2 x [Na+]) + + 18 2.8
[Na+] in mEq/lGlucose in mg/dlBUN = blood urea nitrogen in mg/dl
Serum osmolality < 260 mOsm/kg H2OSerum osmolality > 325 mOsm/kg H2O
Neurologic abnormalities•Confusion•Obtundation•Abnormal muscular activity•Seizures
Extracellular osmolality = 290 ± 10 mOsm/kg H2O
Intracellular Extracellular
Sodium balance
Oncotic pressure Membrane permeability
Hydrostatic pressureLymphatic drainage
ProteIns
23
Starling’s Equation
Q = kA [ ( Pc - Pi ) + ( i - c ) ] (mEq / L)
Q = fluid filtrationk = capillary filtration coefficientA = area of the capillary membranePc = capillary hydrostatic pressurePi = interstitial hydrostatic pressure = reflection coefficient for albumini = interstitial colloid osmotic pressurec = capillary colloid osmotic pressure
Osmolality (mOsm/kg)
Plasma ISF
[Na+] (non-protein) 281.4 281.1
Protein 1.2 0.2
Total 282.6 281.3
Plasma ISF
[Na+] (non-protein) 5431.0 5425.2
Protein 23.2 3.9
Total 5454.2 5429.1
25.1 mmHg
Osmotic pressure (mmHg)
Capillary
Arterial Venous
Interstitium
Lymphatic drainage
Pc = 40 mmHg
Pc = 10 mmHg
c = 23 mmHg
Pi = 2 mmHgi = 4 mmHg
Filtration Absorption
c = 18 mmHg
27
Control of Body Fluid Compartments
Atrial natriuretic peptide Vasopressine Renin, angiotensin Parathyroid hormone Calcitonin Prostaglandins Dopaminergic receptors -adrenergic receptors Thirst mechanism Intrinsic renal properties
28
Volume and Electrolyte Status
Abnormalities of Volume Concentration Composition
Basis for assessment Medical history Physical examination Laboratory data
29
Volume changes (1)
Volume deficit Insufficient intake External losses Distributional volume deficit
Volume excess
30
Distributional Volume Deficit
Transfer of isotonic solution from a functional compartment to a nonfunctional space
Equivalent to ECF volume loss Isotonic Both ISF and PV contribute Same systemic manifestations as ECF loss
Surgical trauma, muscle injury, burns, peritonitis, ascites
Extracellular Fluid Deficit: Clinical Findings (1)
Decrease in body weight
(%)
Clinical signs
Mild 3 - 5 Dry mucous membranes, oliguria
Moderate
6 - 10 Orthostatic hypotension,
tachycardia, anorexia, apathy, poor skin
turgor
Extracellular Fluid Deficit: Clinical Findings (2)
Decrease in body weight
(%)
Clinical
signs
Severe 11 - 15 Supine hypotension, stupor, sunken eyes,
cool and dry skin, mild hypothermia
Catastrophic
> 20 Coma, anuria, significant in core
temp., dicrotic pulse, pulsus paradoxus,
circulatory collapse
33
Volume changes (2)
Volume deficit Volume excess
Iatrogenic Medical condition
Cardiac, hepatic or renal dysfunction Mobilization of third space losses
34
Concentration Changes
Loss of extracellular water
Increased serum [Na+]
Increased serum osmolality
Redistribution of water
Changes in osmolality and solute concentrations in other fluid compartments
Disorders of water balance
35
Changes in Composition
Changes in acid-base balance Changes in electrolytes
Sodium Calcium Magnesium Potassium
Changes in plasma proteins
36
Tonicity
Relative osmolality of solutions Isotonic
Osmotic pressure = osmotic pressure of body fluids Hypertonic
Osmotic pressure > osmotic pressure of body fluids intracellular volume depletion
HypotonicOsmotic pressure < osmotic pressure of body fluids cellular swelling
Extracellular Intracellular
Osm. Volume Osm. Volume
Water
Hypertonic salt solution
Isotonic salt solution
Loss of sodium chloride
Sugar(g/l)
Electrolytes Na K Ca Cl
(mEq/l)
Other anions(mEq/l)
Osmol(mOsm/l)
D5W 50 252
D5W + 40 mEq/l KCl
50 40 333
D10W 100 505
LR 130 4 3 109 28 273
D5W - LR 50 130 4 3 109 28 525
0.45% NaCl 77 77 154
0.9% NaCl 154 154 308
Albumin 5% 154 154 310
0
50
100
150
200
250
D5WLactatedRinger’s
Albumin5 %
Volume (ml)
Prough, Anesthesiology Clinics of North America (1996)
Administration of 250 ml of fluid
ICV
ISV
PV
Prough, Anesthesiology Clinics of North America (1996)
Administration of 250 ml of fluid
Volume (ml)
ICV
ISV
PV
-750
-500
-250
0
250
500
750
1000
D5W LR Alb 5% Alb 25%
41
Intraoperative Fluid Management
Volume, composition and concentration of intravenously administered fluids should beadjusted to maintain baseline function of
vital organ systems
42
Intraoperative Fluid Management
Basal fluid requirements Correction of preoperative fluid deficits
Fasting Disease-related fluid losses
Intraoperative fluid losses Blood loss Redistribution: ”Third space fluid loss” Other fluid losses
43
Basal Fluid and Electrolyte Losses (1)
Constant loss of water and electrolytes Skin
Insensible losses (evaporation) Perspiration
Lungs Insensible losses
Kidneys Gastrointestinal tract
Water (ml) Electrolytes
Skin Insensible 400
Perspiration 100 Na+
Lungs Insensible 400
Kidney Urine 1 500 K+
Gastro-intestinal
Feces 100 Na+, K+
Total 2 500
70 kg adult / 24 h
Basal water losses parallel energy expenditures Maintenance fluids (hospitalized pts): 100 ml/100 kcal/d
From Holliday MA and Segar WE, Pediatrics (1957)
1000
1500
17001900
2100 2300
2500
Computed need for average hospital patients
46
Decreased Metabolic Rate
Starvation Hypothyroidism Addison’s disease Obesity associated with hypothalamic or
pituitary dysfunction General anesthesia Extremes of age
47
Increased Metabolic Rate Skeletal muscle activity Ingestion of nutrients Caffeine, nicotine Fever, sepsis Elevated ambient temperature Diabetes insipidus Leukemia Polycythemia Dyspnea associated with cardiac, pulmonary,
renal disease
Normal activity and temperature
Normal activity, high temperature
Urine 1400 1200
Sweat 100 1400
Feces 100 100
Insensible loss 700 600
Total 2300 3300
Daily loss of water (mL)
From Rhoades and Tanner, Medical Physiology, Little, Brown & Co., Boston (1995)
49
Basal Fluid and Electrolyte Losses (2)
Volume Basal water losses parallel energy
expenditures 4-2-1 RuleWeight
(kg)Volume required
0-10 4 ml/kg/h
11-20 40 ml/h + 2 ml/kg/h above 10 kg
> 20 60 ml/h + 1 ml/kg/h above 20 kg
Weight (kg) Volume 70 kg
0 – 10 4 ml/kg/h 40
11 - 20 2 ml/kg/h 20
> 20 1 ml/kg/h 50
Total 110 ml/h
“4-2-1” rule
51
Basal Fluid and Electrolyte Losses (3)
Electrolytes Sodium: 1 – 2 mEq/kg/d Potassium: 1 – 1.5 mEq/kg/d Calcium: 1 – 1.5 mEq/kg/d
52
Intraoperative Fluid Administration
Maintenance fluids Correction of fluid deficit Replacement of intraoperative fluid losses
53
Intraoperative Maintenance Fluids (1)
Volume “4-2-1” rule Possibly increased intraoperatively
Fever Sweating Denuded skin Exposed peritoneal or pleural surfaces Non-humidified gasses, at high flow rates
54
Intraoperative Maintenance Fluids (2)
Composition Water
D5W Electrolytes
Not for minor surgery in healthy patients Potassium
Bowel preparation
55
Intraoperative Maintenance Fluids (3)
Glucose Indicated in type I diabetes mellitus
2-3 g/kg/d Indicated if risk of hypoglycemia
Total parenteral nutrition Insulinoma Prolonged (> 24 h) fasting Starvation
Avoid if risk of cerebral ischemia Hyperglycemia-induced cerebral acidosis
56
Correction of Preoperative Fluid Deficit
Preoperative fasting fluid deficit Basal maint. fluids/h x npo period (h)
1st hour: 50 % of deficit 2nd hour: 25 % of deficit 3rd hour: 25 % of deficit
Additional fluid deficits Disease-related fluid losses
External Internal
Elhakim et al., Acta Anaesth Scand (1998), 42
Time
VAS for nausea
(mm)
1 h 2 h 4 h 6 h 24 h48 h72 h0
5
10
15
20
25
30
Crystalloid
No crystalloid
**
*
**
* P>0.05
Elhakim et al., Acta Anaesth Scand (1998), 42* P>0.05
Vomiting (n)
Crystalloid No crystalloid
Day unit (6 h) 2 3
6 h – 3 d 0 8
0 - 2 h 2 2
2 - 4 h 0 1
4 - 6 h 0 0
6 - 24 h 0 8
24 - 48 h 0 3
48 - 72 h 0 1
*
59
External Fluid Losses
Gastrointestinal tract Vomiting, diarrhea, ostomy output,
overzealous bowel preparation Hidden: bowel obstruction, ileus Volume, concentration and composition
disturbances External blood loss
Gastrointestinal bleeding Traumatic injuries
Volume and composition of gastrointestinal fluids
From Miller, Anesthesia, 5th ed.
24 h vol. (mL)
Na+ (mEq/L)
K+ (mEq/L)
Cl- (mEq/L)
HCO3-
(mEq/L)
Saliva 500-2000 2-10 20-30 8-18 30
Stomach 1000-2000 60-100 10-20 100-130 0
Pancreas 300-800 135-145 5-10 70-90 95-120
Bile 300-600 135-145 5-10 90-130 30-40
Jejunum 2000-4000 120-140 5-10 90-140 30-40
Ileum 1000-2000 80-150 2-8 45-140 30
Colon - 60 30 40 -
61
Internal Fluid Losses (1)
Sequestered ECF pool Cavitary fluid losses
Pathologic transudate of plasma (pleural, ascitic, pericardial)
Anatomical compartment Develop slowly compensation
Third space fluid losses Extracellular tissue fluid Non-anatomical compartment Develop quickly considerable impact on ECF
Internal blood loss
62
Internal Fluid Losses (2)
Sequestered ECF pool Cavitary fluid losses Third space fluid losses Internal blood loss
Retroperitoneal hematoma Aorta aneurysm Leaking vascular anastomosis Pelvic or femoral fracture Splenic rupture Liver trauma
63
Correction of Preoperative Disease-related Fluid Losses (1)
Assessment of ECF volume deficit 1 % in body weight 10 ml/kg fluid
e.g. moderate fluid loss: 8% of body weight 70 kg 8 x 10 x 70 = 5 600 ml
Isotonic fluid: water + salt Normal saline (NaCl 0.9%) Balanced salt solution
e.g. lactated Ringer’s
64
Correction of Preoperative Disease-related Fluid Losses (2)
Ideally: preoperative correction < 20 % of blood volume
Replace over 15 min Redistribution to ISF: 40-60 % within 15-30 min 75 %
within 60 min Large deficit and surgery not urgent
Replace 25-50 % over 1 h Remainder over several hours
Correction of electrolyte abnormalities
65
Replacement of Intraoperative Fluid Losses (1)
Blood loss Redistribution and subsequent loss of
extracellular and intracellular fluid Replacement with crystalloids
Volume blood:crystalloid ratio 3:1 to 5:1 (even 7:1)
Composition NaCl 0.9 % Balanced electrolyte solution
Colloids Blood products
Third space losses
Cervera et al., Am J Surg (1975), 129
67
Replacement of Intraoperative Fluid Losses(2)
Redistribution: “Third space fluid loss” Sequestered extracellular fluid Volume related to surgical trauma
Minor: 2 - 4 ml/kg/h Intermediate: 4 - 8 ml/kg/h Major: 8 - 15 ml/kg/h
Replacement fluid NaCl 0.9 % Balanced electrolyte solution
Continues 24 – 48 h Mobilization 1 – 3 days postoperatively
Roberts et al., Ann Surg (1985), 202
Lactated Ringer’s D5W
Fluid (ml) 1660 ± 96 530 ± 92
Duration (min) 253 ±50 187 ± 113
ECV preop (l) 12.5 ± 2.3 12.5 ± 2.4
ECV postop (l) 12.3 ± 7.0 10.6 ± 1.9
* P<0.05 between groups** P<0.05 vs preop
**
*
69
Postoperative Fluid Losses
Basal fluid losses Internal fluid losses
Third space loss Blood loss Accumulation of fluid within body cavities
External fluid losses Blood loss Enhanced insensible loss Transcellular fluid loss
70
Postoperative Fluid Therapy
Basal fluid loss + increased insensible loss Hypotonic maintenance fluids Until adequate oral intake
All other postoperative fluid losses Balanced salt solution + electrolytes
Postoperative day 1- 3: mobilization of third space fluid losses
71
Intraoperative Fluid Therapy: Lack of Good Target Points (1)
Cardiovascular parameters ECG Blood pressure Central venous pressure Pulmonary artery catheter Transesophageal echocardiography
Perfusion directed therapy Fluid overload
72
Intraoperative Fluid Therapy: Lack of Good Target Points (2)
Cardiovascular parameters Perfusion directed therapy
Global Lactate
Regional: Gastrointestinal Gastrointestinal Pco2 tonometry
Organ specific Kidney: urine output
Fluid overload
73
Intraoperative Fluid Therapy: Lack of Good Target Points (3)
Fluid overload Intraoperative absorption of irrigating fluids
during endoscopic surgery Transurethral resection of the prostate Hysteroscopic surgery Absorption can be accurately monitored
74
Fatal Postoperative Pulmonary Edema: Pathogenesis and Literature Review(Arieff: Chest 1999, 115: 1371-1377)
Fatal postoperative pulmonary edema 13 patients (incidence of 0.02 %)
10 generally healthy 3 serious associated medical conditions Age 38 ± 21 y
Within 3 postoperative days Range: 3 to 66 h, mean ± SD: 27 ± 20 h
No predictive variables No predictive warning signs
Cardiorespiratory arrest first clinical sign in 8 pts Fluid overload as single cause
Mean net fluid retention of 7.0 ± 4.5 l first 27 h postop (24 % increase of total body water)
75
Hyperchloremic Metabolic Acidosis
“Dilutional acidosis” Metabolic acidosis resulting from rapid
administration of fluids that contain near-physiologic concentrations of sodium accompanied by anions (usually chloride) other than bicarbonate or bicarbonate precursors, such as lactate. (D.S. Prough, Anesthesiology 2000)
Dose-dependent
76
Rapid Saline Infusion Produces Hyperchloremic Acidosis in Patients Undergoing Gynecological Surgery.(Scheingraber et al.: Anesthesiology 1999, 90)
Saline(n = 12)
Lact. Ringer’s (n = 12)
Time of infusion (min) 135 ± 23 138 ± 20
Volume after 120 min (ml/kg)
71 ± 14 67 ± 18
Estimated blood loss (ml) 962 ± 332 704 ± 447
Urine output (ml) 717 ± 459 1 075 ± 799
Scheingraber et al., Anesthesiology 90 (1999)
Saline Lactated Ringer ’s
0 min 120 min 0 min 120 min
Bicarbonate
(mM)23.5 ± 2.2 18.4 ± 2.0 23.3 ± 2.0 23.0 ± 1.1
Anion gap (mM)
16.2 ± 1.2 11.8 ± 1.4 15.8 ± 1.4 12.5 ± 1.8
Chloride (mM)
104 115 104 106
Scheingraber et al., Anesthesiology 90 (1999)
Lactated Ringer’sNormal saline
7.50
7.45
7.40
7.35
7.30
7.25
7.200 30 60 90 120 min 0 30 60 90 120 min
0 30 60 90 120 min0 30 60 90 120 min
50
46
42
38
34
30
26
4
0
-4
-8
-12
3.0
2.5
2.0
1.5
1.0
0.5
0.0
mm
Hg
mm
ol/
l
mm
ol/
lpH Carbon dioxide
Base excess Lactate
# # #
### #*
#*
#* #*
*
*
** *
** *
* P<0.05 intragroup# P<0.05 intergroup
Scheingraber et al., Anesthesiology 90 (1999)
Lactated Ringer’sNormal saline
Sodium Chloride
Calculated SID Prot-
0 30 60 90 120 min 0 30 60 90 120 min
0 30 60 90 120 min0 30 60 90 120 min
148
144
140
136
120
115
110
105
100
17.5
15
12.5
10
7.5
45
40
35
30
25
mm
ol/
l
mm
ol/
l
mm
ol/
l
mm
ol/
l
#*#* #*
#*#*
#*#*
#*
#*#*
**
**
***
*
**
*
***
*
**
**
**
* P<0.05 intragroup# P<0.05 intergroup
Replacing 1 Liter of Blood Loss with Crystalloid (3:1)
Crystalloid Excess chloride load(mmol)
3 l of NaCl 0.9 % 165
3 l of lactated Ringer’s 27
81
Hyperchloremic Metabolic Acidosis: Therapy
Switch to balanced electrolyte solution Lactated Ringer’s Plasmalyte
Hyperventilation pH > 7.2 and preferably > 7.3
Furosemide (Fresh frozen plasma)
Transfusion criteria
82
Plasma Volume Expansion (PVE): Static Concept
Plasma volumePVE = Volume infused x
Distribution vol.
Distribution volume:D5W = total body waterLactated Ringer’s = extracellular vol.NaCl 0.9% = extracellular vol.
One-compartment Volume of Fluid Space Model
Ki V V
Kb Kr(V - V)
V
V = expandable space of volume
V = target volume
Ki = constant fluid infusion rate
Kb = basal rate of fluid elimination (perspiration, basal diuresis)
Controlled rate of fluid elimination proportional by a constant Kr to the relative deviation of v from V
Svensén et al., Anesthesiology (1997), 87
Two-compartment Volume of Fluid Space Model
The net rate of fluid exchange between the 2 compartments is proportional to the difference in relative deviations from the target volumes by a constant Kt
Ki V1V1
Kb Kr(V1 - V1)
V1
Kt
V2 V2
Secondary fluid space
Svensén et al., Anesthesiology (1997), 87
85
Plasma Volume Expansion (PVE): Kinetic Analysis
Bolus of fluid Peak effects Rates of clearance
Infusion of fluid necessary to maintain PVE at a certain level
Effects of anesthesia, surgery and trauma on fluid requirements
Usefull during severe pathophysiologic disturbances?
0 20 40 60 80 100 120Time (min)
0 20 40 60 80 100 120Time (min)
0.2
0.15
0.10
0.05
0
0.2
0.15
0.10
0.05
0
Pla
sm
a d
ilu
tion
, (v
– V
)/V Single bolus of Ringer’s
40 ml/min for 40 min
Bolus + continuous infusion of Ringer’s at 25 ml/min
Hahn and Svensen, Br J Anaesth (1997), 79
Hahn and Svensen, Br J Anaesth (1997), 79
88
Volume Kinetics of Ringer’s Solution during Induction of Spinal and General Anaesthesia. (Ewaldsson and Hahn: Br J Anaesth 2001, 87)
10 patients: 20 ml/kg of Ringer acetate over 60 min (0.33 ml/kg/min) Spinal anesthesia 20 min after start of infusion
5 patients: 350 ml of Ringer’s over 2 min immediately after spinal
followed by Ringer’s at 0.33 ml/kg/min Ephedrine 5-10 mg IV if SAP < 60 % of baseline Parameters
Blood pressure Blood hemoglobin concentration
Every 3 min during 60 min
Ewaldsson and Hahn, Br J Anaesth (2001), 87
Spinal anesthesia
Rapid infusion group
0.33 ml/kg/min during 60 min
0.33 ml/kg/min during 40 min350 ml over 2 min
Semipermeable membrane
Solvent
Osmosis
Solute
Solution
Osmoticpressure
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