08. fluid and electrolytes
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Transcript of 08. fluid and electrolytes
Fluid and Electrolytes
Water Content
• 50 to 60% of body weight
• Higher in neonates and children
• Lower in elderly
• Lower in women
52
21
14
13
39
27
18
16
18
36
24
22
0%
20%
40%
60%
80%
100% Solids
ECW
ICW
Fat
IntracellularInterstitial
Intravascular
2/3 1/3
3/4 1/4
IntracellularInterstitial
Intravascular
2/3 1/3
3/4 1/4
ECF osmolality = ICF osmolality
K, ATPCreatinine PO4phospholipids
Na, ClHCO3
Intravascular
Interstitial
3/4 1/4
Capillary membrane
Plasma proteins
IntracellularInterstitial
Intravascular
2/3 1/3
3/4 1/4
Na
K
Plasma Na 153
IC K 150
Water Loss - Starvation
Intracellular Interstitial
Intravascular
2/3 1/3
3/4 1/4
Water & Electrolyte Loss -- GI
Intracellular
Interstitial Intravascular
2/3 1/3
3/4 1/4
Replacement Fluids 5% Dextrose
IntracellularInterstitial
Intravascular
2/3 1/3
666ml 250ml 84ml
1L of Crystalloid
IntracellularInterstitial
Intravascular
2/3 1/3
750ml 250ml
1L of Colloid
IntracellularInterstitial
Intravascular2/3 1/3
1000ml
1L of Colloid
IntracellularInterstitial
Intravascular2/3 1/3
1000ml
Sepsis / Shock
IntracellularInterstitial
Intravascular
2/3 1/3
3/4 1/4
Na
Daily Water Requirement
Weight Water requirement
0-10 kg 4mL/kg/hr
10-20 kg 40mL/hr +2ml/kg/hr for each kg>10kg
>20kg 60ml/hr +1ml/kg/hr for each kg>20kg
for 60kg man this = 100ml/hr or 2400 ml/24 hrsfor normal people!!
Ca 2+
Mg 2+
K+
Na+
Cl-
PO43-
Organic anion
HCO3-
Protein
0
50
50
100
150
100
150
Cations AnionsEC
FIC
F
Solutions Volumes Na+ K+ Ca2+ Mg2+ Cl- HCO3- Dextrose mOsm/L
ECF 142 4 5 103 27 280-310
Lactated Ringer’s 130 4 3 109 28 273
0.9% NaCl 154 154 308
0.45% NaCl 77 77 154
D5W 50 250
D5/0.45% NaCl 77 77 50 406
3% NaCl 513 513 1026
6% Hetastarch 500 154 154 310
5% Albumin 250,500 130-160 <2.5 130-
160 330
25% Albumin 20,50,100 130-160 <2.5 130-
160 330
Hyponatremia
• Serum sodium concentration to a level below 136 mmol per liter
• hyponatremia can be associated with low,
normal, or high tonicity
Hyponatremia
• Clinically associated with mainly CNS changes
• Headache, nausea, vomiting, muscle cramps, lethargy, restlessness, disorientation, and depressed reflexes
Hyponatremia
• 32-year-old woman has three grand mal seizures two days after an appendectomy
• 3L of 5 % D5W infused during 1st PO day
• Unknown oral fluids
• O/E she is euvolemic, and weighs 46 kg
• S Na is 112 mmol per liter
• S K is 4.1 mmol per liter
• S osmolality is 228 mOsm / Kg of water
• Urine osmolality is 510 mOsm / Kg of water
513 –112
23 + 1
1L of 3% Nacl will inc Na by 16.7 meq
60ml will increase Na by 1 meq
• EBWater 23 litres
Na now 112 x 23If you give 1L of 3% saline
(513 x 1) + (112x 23)
New conc of Na = (513 x 1) + (112x 23)/24
diff of Na = [(513 x 1) + (112x 23)/24] – (112)
Rate of correction:Can we exceed 1.5 mEq/L/hr?
Total Correction:Should we limit it to less than 12mEq/L for the first 24 hrs?
What is the level to which we should correct the sodium?Full correction?Limit to 120-125 mEq/L?
Should we treat all hyponatremia? What if the patient isasymptomatic ?
Outcome in severe symptomatic hyponatremia:Age (extremes do well; infants and elderly)Sex (women fare poorly)Respiratory arrest always worsens outcomeRate of correction is not a major factor as long asthe total correction in 24 hours is limited
Common causes:Euvolemic: SIADH, Psychogenic polydipsia, hypothyroidOverloaded: Renal, liver, heart failureDry: Diuretic abuse, GI losses, adrenal hypofunction
Effects of Hyponatremia on the Brain
QuadriplegiaPseudobulbar palsySeizuresComaDeath
Hepatic failureK depletionmalnutrition
Hypernatremia
Na >145 Usually due to dehydration:Water loss: GI losses, sweating, Diabetes InsipidusInadequate intake: Access to water impaired
Excessive salt intake is an unusual cause
Correct with NS if patient is hypotensiveUse hypotonic solutions otherwise
Hypernatremia
Hypernatremia
My Surgery Is Postponed!
You had admitted a 67 year old diabetic with end-stagerenal disease, who has been undergoing thrice-weekly dialysis, for the placement of a new A-V fistula. The case has to be postponed by a day because of another emergency.The next morning, as you arrive to see your patient a panicky nurse informs you that he is hypotensive (BP 80/sys.) and has a heart rate of 38/min. A “sharp”medical intern had administered atropine without successfully improving the blood pressure or heart rate.What
investigation / laboratory testmonitoring device
would you request emergently?
Treatment of this patient should be based on all of thefollowing EXCEPT:
a. There should be no delay in treatment, waiting for the electrolyte imbalance to be confirmed by the labb. Administration of intravenous calcium (chloride or gluconate) is the first stepc. Sodium bicarbonate is neededd. Parenteral administration of an ion exchange resin (kayexelate) is needed e. Glucose / insulin will help
Hyperkalemia:Common Causes:
Renal Failure, AcidosisDrugs: K-sparing diuretics, ACE inhibitorsCell death: burns, rhabdomyolysis
Pseudohyperkalemia is an in-vitro rise in K associated with WBC > 100K/mm3 or platelets > 600K/mm3
Haemolysis should also be considered
ECG changes:Peaked T, wide PR&QRS, bradycardia, heart block
Hyperkalemia:
Post Op Ileus
A 47 year old with a history of bronchial asthma has undergone an open cholecystectomy. His postoperative recovery has been complicated by respiratory distressdue to exacerbation of asthma. He is already on peri-opampicillin, gentamicin and metronidazole. Since hisasthma did not respond to 2-hourly nebulized salbutamolhe has been given parenteral steroids. With poor mobilization of secretions he has developed atelectasis of the R lung base and moderate hypoxia. A physician had advised the administration of lasix to help improve PO2 Even though it is now the third post-op day, the patient hasan ileus with RT returns of nearly 1200 ml / day.
Electrolyte Concentration in Body Fluids
Na K Cl HCO3
Saliva Low Moderate Low ModerateBile High Low Moderate ModerateStomach Moderate Variable Low NoneSmall gut High Low Low HighDiarrhea Low High Low ModerateSweat Moderate Low Moderate None
Na and K
• Daily requirements
– Na 1 to 2 mEq / Kg / day– K 1 mEq / Kg / day
Seizures Followed by Unresponsiveness
A52-year-old woman had undergone a mastectomy andaxillary node dissection about 11 years ago. She was nodepositive and received combination chemotherapy. Shehad otherwise been well till 2-3 days prior to admission, whenhas been complaining of nausea, vomiting and anorexia. She was noted to be irritable and then increasingly somnolent. She was brought to your hospital after she had a single generalized convulsion after which she has not awoken. The family also notes that she has been voiding large quantities of urine and has been bedwetting in the last two days. A contrast CT scan of the brain shows no abnormality.
Which of the following would be logical explanationsfor the patient’s symptoms (arrange in decreasing order of likelihood):A. Despite a negative CT scan, brain mets. and associated diabetes insipidus should be considered. Hypernatremia may be the cause of symptoms.B. Mets. to other sites producing ectopic ADH may be causing hyponatremia and an associated encephalopathyC. Since metastaic breast cancer is a common cause of hypercalcemia, we must consider this as the most likely etiology.
What laboratory investigations would you ask for?
“Routine” laboratory values are received:
Na = 152 mEq/LBUN = 50 mg/dlCr. = 2.0 mg/dlBP = 90/50 mm HgHR = 130 frequent PVC's
Ca = 16 mg/dl
Immediate management should include:
a. Disodium etidronate (biphosphonate) to lower Ca levelsb. Immediate hydration with NS; followed by 1/2NS to provide 4-6litres/day + lasix or ethacrynic acidc. Immediate hydration with 5%dextrose followed by fluid to correct 1/2 the estimated free water deficit based on S. Nad. Immediate dialysis with Ca free dialysatee. Calcitonin + steroids
HypercalcemiaCauses:
Malignancy Lung 35%Breast 25%Hematological 14%Head & Neck 6%Renal 3%
Hyperparathyroid Solitary adenoma 80%Hyperplasia 15%Malignancy <5%
Sarcoid and granulomatous diseaseVitamin A&D intoxication
90%ofall
HypercalcemiaSigns & symptoms:
Mental: Stupor, obtundation, apathy, lethargy, confusion, comaNeurological: Reduced muscle tone, reflexesGI& Renal: Nausea, vomiting, constipation, polyuria, polydypsiaECG: Short QT, arrhythmia
Case 4:
In this case which of the following maneuvers will helpresolution of the ileus:a. D/C ampicillinb. D/C gentamicinc. D/C flagyld. Avoid inhaled salbutamole. Switch to parenteral salbutamolf. Change parenteral to inhaled steroidsg. Administer iv calcium gluconateh. Administer iv magnesium sulphate i. D/C lasix j. D/C Ryle’s tubeh. Improve the asthma What is
the defi
nitive t
reatm
ent?
Hypokalemia
Case 5:
A 78 year old male with no known medical illness had presented with septic shock due to a large bowel perforation,which has been treated with a colostomy and antibiotic Rx.He has needed ventilatory and haemodynamic supportbut has stabilized. His weaning off the ventilator is compromised by inadequate patient effort. He is receiving enteral feeding and is tolerating about 100cc/hr (1800 Kcal/day). The only abnormal laboratory values are:
S. Calcium (total) 6.2mg/dl, S. Albumin 2.0 g/dl,
Case 5:
In this case, it would be absolutely imperative to:a. Administer albumin to improve nutritional parameters and enhance weaning from the ventilator b. Administer 10 ml (1 amp) of calcium gluconate (~90 mg) at once and follow-up with an infusion of 0.3-2 mg/kg/hrc. Use calcium “chloride” instead of “gluconate” because its actions are more rapid in onset.d. Provide no treatment, though there is severe hypocalcemia, as the patient is otherwise asymptomatice. Provide no specific treatment, as the clinical and lab parameters are not of concern in the short run
Case 6:
A45 year-old has undergone repeat surgery for the Rxof hyperparathyroidism. His prior surgery over a year agodid not provide symptomatic or biochemical improvement.There is no available documentation of the procedure performed and amount of parathyroid tissue removed. By theevening of the surgery the patient develops hyperreflexia,carpopedal spasm and paresthesias. After initial treatmentwith injectable calcium preparations he is placed on oraldoses of nearly 2.5 g of elemental calcium / day. About 10 days from the surgery he has persistent hyperreflexia and has an ionized Ca of 1.0 mmol/L and PO4 is 5.9 mg/dl
Case 6:
Further treatment should include:
a. Lower the phosphate levels by antacids or sucralfate b. Evaluation for and correction of magnesium deficitsc. Increase the oral calcium supplementsd. Addition of vitamin D supplements
Causes of HypocalcemiaChronic renal failure
Hypoparathyroidism
Acute Pancreatitis
Sepsis
Burns, rhabdomyolysis
Hypomagnesemia
Massive transfusion