Surgery 6th year, Tutorial (Dr. AbdulWahid)
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Transcript of Surgery 6th year, Tutorial (Dr. AbdulWahid)
Fluid & Electrolytes Fluid & Electrolytes ManagementManagement
Component & composition of body fluid
Mechanisms of fluid homeostasis
Parenteral fluid therapy
Fluid and electrolyte balance is an extremely complicated thing.
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Solutes – dissolved particlesElectrolytes – charged particles Cations – positively charged ions
Na+, K+ , Ca++, H+
Anions – negatively charged ionsCl-, HCO3
- , PO43-
Non-electrolytes - Uncharged Proteins, urea, glucose, O2, CO2
Composition of Body Fluids:Composition of Body Fluids:
Ca 2+
Mg 2+
K+
Na+
Cl-
PO43-
Organic anion
HCO3-
Protein
0
50
50
100
150
100
150
Cations Anions
EC
FICF
Osmolarity = solute/(solute+solvent)Osmolarity = solute/(solute+solvent) Osmolality = solute/solvent (290~310mOsm/L)Osmolality = solute/solvent (290~310mOsm/L) Tonicity = effective osmolalityTonicity = effective osmolality Plasma osmolility = 2 x (Na) + (Glucose/18) + (Urea/2.8)Plasma osmolility = 2 x (Na) + (Glucose/18) + (Urea/2.8) Plasma tonicity = 2 x (Na) + (Glucose/18)Plasma tonicity = 2 x (Na) + (Glucose/18)
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Regulation of Fluids:Regulation of Fluids:
Renal sympathetic nerves
Renin-angiotensin-
aldosterone system
Atrial natriuretic peptide (ANP)
GI secretionsVolume (ml) per day
• Saliva 1500• Gastric 2500• Bile 500 • Pancreatic 700• Intestinal 3000• TOTAL 8000
Composition of GI Composition of GI Secretions:Secretions:
SourceSource Volume Volume (ml/24h)(ml/24h) NaNa+*+* KK++ ClCl-- HCOHCO33
--
SalivarySalivary1500 (500~2000)
10 (2~10)26 (20~30)
10 (8~18) 30
StomachStomach1500 (100~4000)
60 (9~116)10 (0~32)
130 (8~154)
0
DuodenuDuodenumm
100~2000 140 5 80 0
IleumIleum 3000140 (80~150)
5 (2~8)104 (43~137)
30
ColonColon 100-9000 60 30 40 0
PancreasPancreas 100-800140 (113~185)
5 (3~7) 75 (54~95) 115
Bile Bile 50-800145 (131~164)
5 (3~12)100 (89~180)
35
* Average concentration: mmol/L
Crystalloid solutions –
clear fluids made up of water and electrolyte solutions; Will cross a semi-permeable membrane e.g Normal, hypo and hypertonic saline solutions; Dextrose solutions; Ringer’s lactate and Hartmann’s solution.
Colloid solutions – Gelatinous solutions containing particles suspended in solution. These particles will not form a sediment under the influence of gravity and are largely unable to cross a semi-permeable membrane. e.g. Albumin, Dextrans, Hydroxyethyl starch [HES]; Haemaccel and Gelofusine
Saline Solutions(1) 0.9% Normal Saline – Think of it as ‘Salt and water’
Principal fluid used for intravascular resuscitation and replacement of salt loss e.g diarrhoea and vomitingContains: Na+ 154 mmol/l, K+ - Nil, Cl- - 154 mmol/l; But K+ is often added
IsoOsmolar compared to normal plasmaDistribution: Stays almost entirely in the Extracellular space Of 1 litre – 750ml Extra cellular fluid; 250ml intravacular fluidSo for 100ml blood loss – need to give 400ml N.saline [only 25% remains intravascular]
(2) 0.45% Normal saline = ‘Half’ Normal Saline = HYPOtonic salineReserved for severe hyperosmolar states E.g. severe dehydrationLeads to HYPOnatraemia if plasma sodium is normalMay cause rapid reduction in serum sodium if used in excess or infused too rapidly. This may lead to cerebral oedema and rarely, central pontine demyelinosis ; Use with caution!
(3) 1.8, 3.0, 7.0, 7.5 and 10% Saline = HYPERtonic salineReserved for plasma expansion with colloidsIn practice rarely used in general wards; Reserved for high dependency, specialist areasDistributed almost entirely in the ECF and intravascular space. This leads to an osmotic gradient between the ECF and ICF, causing passage of fluid into the EC space. This fluid distributes itself evenly across the ECF and intravascualr space, in turn leading to intravascular repletion. Large volumes will cause HYPERnatraemia and IC dehydration.
Dextrose solutions(1) 5% Dextrose (often written D5W) – Think of it as ‘Sugar
and Water’Primarily used to maintain water balance in patients who are not able to take anything by mouth; Commonly used post-operatively in conjuction with salt retaining fluids ie saline; Often prescribed as 2L D5W: 1L N.Saline [‘Physiological replacement’ of water and Na+ losses]Provides some calories [ approximately 10% of daily requirements]Regarded as ‘electrolyte free’ – contains NO Sodium, Potassium, Chloride or CalciumDistribution: <10% Intravascular; > 66% intracellularWhen infused is rapidly redistributed into the intracellular space; Less than 10% stays in the intravascular space therefore it is of limited use in fluid resuscitation. For every 100ml blood loss – need 1000ml dextrose replacement [10% retained in intravascular spaceCommon cause of iatrogenic hyponatraemia in surgical patient
(2) Dextrose saline – Think of it as ‘a bit of salt and sugar’Similar indications to 5% dextrose; Provides Na+ 30mmol/l and Cl- 30mmol/l Ie a sprinkling of salt and sugar!Primarily used to replace water losses post-operativelyLimited indications outside of post-operative replacement – ‘Neither really saline or dextrose’; Advantage – doesn’t commonly cause water or salt overload.
Colloid solutionsThe colloid solutions contain particles which do not readily cross semi-permeable membranes such as the capillary membraneThus the volume infused stays (initially) almost entirely within the intravascular space Stay intravascular for a prolonged period compared to crystalloidsHowever they leak out of the intravascular space when the capillary permeability significantly changes e.g. Severe trauma or sepsisUntil recently they were regarded as the gold standard for intravascular resuscitation (see next slide)Because of their gelatinous properties they cause platelet dysfunction and interfere with fibrinolysis and coagulation factors (factor VIII) – thus they can cause significant coagulopathy in large volumes.
Fluid & electrolyte balance
Fluid replacement1. Maintenance requirement2. Replacement of losses3. Ongoing losses
Volume Deficit-Clinical Types
Total body water: Water loss (diabetes insipidus, osmotic diarrhea)
Extracellular: Salt and water loss ( ascites, edema) Third spacing
Intravascular: Acute hemorrhage
Replacement of losses
1. Actual losses Bleeding Vomiting/diarrhoea
2. Ongoing losses Stoma Drains Fistulae NGT U/O
Parenteral Fluid Therapy:Parenteral Fluid Therapy:
Crystalloids:Crystalloids: - contain Na as the main osmotically active particle - useful for volume expansion (mainly interstitial space) - for maintenance infusion - correction of electrolyte abnormality
Crystalloids:Crystalloids:
Isotonic crystalloids - Lactated Ringer’s, 0.9% NaCl - only 25% remain intravascularly
Hypertonic saline solutions - 3% NaCl
Hypotonic solutions - D5W, 0.45% NaCl - less than 10% remain intra- vascularly, inadequate for fluid resuscitation
Colloid Solutions:Colloid Solutions:
Contain high molecular weight substancesdo not readily migrate across capillary walls
Preparations - Albumin: 5%, 25% - Dextran - Gelifundol
- Haes-steril 10%
SolutionSolutionss
VolumeVolumess
NaNa++ KK++ CaCa2+2+ MgMg2+2+ ClCl-- HCOHCO33-- DextroseDextrose mOsm/LmOsm/L
ECFECF 142 4 5 103 27 280-310
Lactated Lactated Ringer’sRinger’s
130 4 3 109 28 273
0.9% 0.9% NaClNaCl
154 154 308
0.45% 0.45% NaClNaCl
77 77 154
D5WD5W
D5/0.45% D5/0.45% NaClNaCl
77 77 278 406
3% NaCl3% NaCl 513 513 1026
6% Hetast6% Hetastarcharch 500 154 154 310
5% 5% AlbuminAlbumin
250,500130-160
<2.5
130-160
330
25% 25% AlbuminAlbumin
20,50,100
130-160
<2.5
130-160
330
Common parenteral fluid therapyCommon parenteral fluid therapy
The Influence of Colloid & The Influence of Colloid & Crystalloid on Blood Volume:Crystalloid on Blood Volume:
1000cc
500cc
500cc
500cc
200
600
1000
Lactated Ringers
5% Albumin
6% Hetastarch
Whole blood
Blood volumeInfusion volume
Example of IVF order
Maintenance (patient of average weight): 1L N/S + 20mmol KCl 1L 4% Dex N/5 + 20mmol KCl 1L 4% Dex N/5 + 20mmol KCl
Note: Gastric outlet obstruction – N/S + KCl SBO – Hartmann’s solution Most of ongoing “surgical” losses are rich in Na
Your fluid chart should look something like this. (I have written it out twice as I was unconvinced of my first attempt)
Maintenance
VariableUsually 2.5-3L/day
Rough guide: 2-3mmol
NaCl/kg/day 1-2mmol K/kg/day
Volume Electrolytes
Fluid Management:Fluid Management:
Goal:Goal: - to maintain urine output of 0.5~1.0ml/kg/h
Electrolytes require:Electrolytes require: - Na+: 1-2mmol/kg/day - K+: 0.5~1.0mmol/kg/day
Avoid fluid overload, especially in malnutrition,
heart failure and renal insufficiency patient
Fluid Management:Fluid Management:
For acute blood lossFor acute blood loss - Begin with 2-3L isotonic crystalloid to restore blood pressure and peripheral perfusion - Early use of colloid - Crystalloid + 5% albumin in a ratio of
4:1 - Blood transfusion - Large borne IV line