Fluid, electrolyte and acide-base problems in surgery L.Dadak Dept. of Anesthesia and Intensive Care St. Ann's University Hospital Laboratory ● Never completely trust the laboratory ● errors with blood sample ● Will result change my decision? Never completely trust the laboratory Quick <0.10 ( 0.70 - 1.34 ) <-( ) repeated aPTT >150 s ( 20.0 - 40.0 ) <=( ) repeated Fibrinogen 4.50 g/l ( 1.80 - 4.00 ) ( )-> Antitrombin III 32 % ( 80 - 120 ) <-( ) - - - - - - - - - - - same patient, 30 min later - - - - - - - - - - - - - Quick 0.55 ( 0.70 - 1.34 ) <-( ) aPTT 44.7 s ( 20.0 - 40.0 ) ( )-> Aptt ratio 1.49 Fibrinogen 5.40 g/l ( 1.80 - 4.00 ) ( )-> INR 1.59 ( 0.85 - 1.38 ) ( )-> Antitrombin III 61 % ( 80 - 120 ) <-( ) Blood for analysis ● arterial ● capillar ● venous ● periferal ● central ● mixed venous (v.cava, a.pulmonalis) Osmolarity, osmolality ● Each particle present in the water binds number molecules of water. Serum osmolarity is measured directly by determining the freezing point of serum. normal 275 .. 295 mOsm/l Calculated osmolarity = 2 * Na + Glc + Urea [mOsm/l] 2* 140 + 5 + 3 Gap > 10 mOsm/l ... another solute (lactate, ethanol ) Gap > 50 mOsm/l ... often fatal Osmolality [mmol/kg of water] Electroneutrality ● sum of cations is equal to sum of anions ● Na+, K+, Mg++, Ca++ ... ● Cl-, HCO3-, PO4--, proteins- Water ● 55% - 60%, new born 80% of body weight ● Compartment = place of water + ionts Water - compartments: ECF = IVF + ISF ICF Intracellular fluid ● 40% body weight ● more proteins, K+ Extracellular fluid ● 20% body weight ● interstitial fluid (lymph) ● plasma ● bone ● connective tissue ● transcellular fluid Homeostasis ● tendency to keep stable ● isovolemia ● H+ = pH, pCO2, ● Glc, ions ● isohydria, isoionia, isoosmia Priorities ● fluid volume and perfusion deficits ● correction of pH ● K, Ca, Mg ● Na, Cl Hypovolemia ● deficit of water ● estimated from ● weight loss ● thirst ● physical signs (soft eyes, tachycardia, hypotension, oliguria, organ dysfunction – brain ) ● hypo, iso, hypertonic ● Treatment: add water (crystaloid, coloid) Basic Needs (Adult) ● Basic need 2 ml/kg/h ● Current losses ● 1°C fever = 500ml/d ● sweating ● diarrhea ... water with ions [mmol/l] Hypervolemia ● hypotonic – excess of water (no ions e.g. 5% Glc) ● isotonic – anuria + intake crystaloids ● hypertonic – intake of concentrated solutions, loss of hypoosmolar fluid. / rare/ Ions in the body ^● Sodium Na^+ ● Potassium K^+ ● Calcium Ca^++ ● Magnesium Mg^++ ^● Phosphorus PO[4]^- ● Chloride Cl^- - - - - - - - - - - ● Glucose Glc Sodium Na+ ● extracellular fluid 140 mmol/l ● intracellular fluid 10 mmol/l ● Hyponatremia ● Hypernatremia Hyponatremia Na+ in serum < 120 mmol/l ● usually due to hemodilution by too much water ● sodium loss ● vomiting ● diarrhea ● sweating, ● renal / CNS disorders, diuretics ● third space sequestration (burns, pancreatitis, peritonitis) ● factitous (hyperglycemia, hyperlipidemia, manitol) - osmolality normal / increased Hyponatremia - symptoms ● Fatique ● Apathy, coma, change in mental status ● Headache ● Muscle cramps, weakness ● Anorexia, nausea, vomiting, ● Mild to moderate hyponatremia is usually asymptomatic. Treatment of hyponatremia ● stable pat. - water restriction ● severe, acute, symptomatic pat. - 3% NaCl i.v. Hypernatremia ● inadequate water intake ● excessive loss of water ● diarrhea ● vomiting ● hyperpyrexia ● excessive sweating ● diabetes insipidus (ADH) = loss of hypotonic urine ● increased intake of salt ● coma, no responce to thirst Therapy: Glc 5% i.v. Potassium K+ ● Major intracellular cation ● serum (2% of total) 3.8 .. 5.6 mmol/l ● electric potential on membrane (Na+/K+ ATPasa) ● arytmias ● extremly responsive to changes of pH!! Acidosis in cell (H+) banish K+ out of cell. Hypokalemia K < 4 mmol/l ● losses in urine ● diurettics, diarrhea, vomiting ● reduced intake ● Alcalosis ● CAVE severe muscle weakness, asystolia Treatment: ● KCl p.os; max KCl 40 mmol/h i.v. ● ECG monitoring !!!! Hyperkalemia ● hemolysis ● muscle damage ● anuria, renal failure ● Acidosis ● CAVE intracardiac block (diastolic arest) or fibrilation ● muscle weakness – ventilatory failure therapy: ● stop intake ● Glc + HMR i.v., loop diuretic (furosemide) ● Calcium i.v., bicarbonate i.v ● resonium p.os ● dialysis Calcium Ca++ ● most abundant mineral in the body 2kg ● Parathormone PTH ● stimulate osteoklast ● stimulate intestine ● resorption in kidney ● Calcitonin ● inhibites osteoklast ● Vitamine D ● potens saving Ca++ Ionised Ca = 1.1 mmol/l // efect of all Calcium bound by proteins =ineffective to receptors Calcium Ca++ ● Hypocalcemia ● Respiratory Alcalosis, hypoPTH, ● shock, sepsis, pancreatitis ● together hypomagnesemia ● Hypercalcemia ● muscle damage ● malignancy Chloride Cl- ● Major anion in Extracellular fluid ● see ABR Glucose ● hyperglycemia ● hypoglycemia / insulin overdose/ ● next week Acide-base arterial blood: pH 7,35-7,45 pCO[2] 4,6-6 kPa pO[2] 10-13 kPa HCO[3]^- 22-26mmol/L BE -2 .. +2 mmol/L SpO2 95-98% CO2 Glc + O[2]  CO[2] + H[2]O CO[2] + H[2]O  H[2]CO[3]  H^+ + HCO[3]^- ∆pH ∆ p CO2 0.1 1,6 kPa = 12 mmHg Genesis of Acid = giver of H+ ● lactate - shock ● strong acids intake (HCl, H2SO4) ● acetylsalicilic acid (drug overdose) ● ... ∆pH ∆ p CO2 0.1 1,6 kPa = 12 mmHg Basic laws pH = - log [H+] [H+] ... mol/l pH = pK + log (H+ acceptor /H+ donor) ● acidosis pH < 7.36 ● alcalosis pH > 7.44 Place of error: ● Respiratory (lung) ... pCO2 ● Metabolic (kidney) ... BE BE = number of acid needed to correct sample to 7.4 Not exact true... ... but it helps ∆pH BE ∆ p CO2 0.1 6mmol/l 1,6 kPa = 12 mmHg Kilopascals for PCO[2]. ● Many texts and papers express the PCO[2] in kilopascals (kPa). It is useful to remember that this value is almost the same as the percentage of atmospheric pressure. For example, the normal arterial PCO[2] of 40 mmHg is 5.33 kPa or 5.61 %. ● To convert pressure in mmHg to kPa, it is necessary to divide the value in mmHg by 7.5. RAc ● Respiratory Acidosis. The decision to ventilate a patient to reduce the PCO[2] is a clinical decision and is based on exhaustion, prognosis, prospect of improvement from concurrent therapy, and in part on the PCO[2] level. Once the decision is made, the PCO[2] helps to calculate the appropriate correction. The PCO[2] reflects a balance between the carbon dioxide production and its elimination. Unless the metabolic rate changes, the amount of carbon dioxide to be eliminated remains constant. It directly determines the amount of ventilation required and the level of PCO[2]. Where V[T] equals tidal volume and f equals respiratory rate: ● PCO[2] x Ventilation = Constant, i.e., PCO[2] x V[T] x f = k MAc • kidney unable to eliminate H+ = anuria • big production of acides. • The treatment for a metabolic acidosis is, again, judged largely on clinical grounds. Bicarbonate therapy is justified when metabolic acidosis accompanies difficulty in resuscitating an individual or in maintaining cardiovascular stability. • A typical dose of bicarbonate might be 1 mEq per kilogram of body weight followed by repeat blood gas analysis. • Calculation is based on BE and the size of the treatable space (0.3 x weight, e.g., 21 liters): Dose (mEq) = 0.3 x Wt (kg) x BE (mEq/L). RAl ● hyperventilation ● lost of ionized Calcium / hypocalcemia / tetania MAl ● increased loss of NH4 to urine ● saving HCO3- by kidney ● loss of Cl- (vomiting) ● BE > O ● pH > 7.44 ● Th: i.v. FR (NaCl) How to ● what is wrong ● what the body do ● what to do OR / AAA, 5 000ml lost, haemorh. shock, NA i.v., general anesthesia, VCV pH akt. 7.083 ( 7.350 - 7.450 ) <-( ) pCO2 6.36 kPa ( 4.80 - 5.90 ) ( )-> pO2 30.78 kPa ( 10.66 - 13.30 ) ( )=> BE -15.8 mmol/l ( -2.6 - 2.6 ) <=( ) BB 32.1 mmol/l ( 40.0 - 44.0 ) <=( ) HCO3 akt. 13.9 mmol/l ( 22.0 - 26.0 ) <=( ) O2 sat. 99.3 ( 95.0 - 98.0 ) ( )=> OR / AAA, 6 500ml loost, haemorh. shock, NA i.v. pH akt. 7.1 ( 7.350 - 7.450 ) <=( ) pCO2 5.0 kPa ( 4.80 - 5.90 ) ( * ) BE -18 mmol/l ( -2.6 - 2.6 ) <=( ) lactate 13 mmol/l ( 1 – 2.5 ) ( )= => Try it yourself pH = 7,2 pCO2 = 14 kPa BE = 20 mmol/l SUMARY ● Biologic system react primary to rate of change and not to absolute concentrations. ● Abnormalities should be treated at proximately the rate at which they developed. ● DO NOT rapid correction of a chronic asymptomatic abnormality. When order electrolytes exam: ● poor oral intake ● vomiting ● chronic hypertension ● diuretic use ● recent seizure ● muscle weakness ● age over 65 ● alcoholism ● history of electrolyte abnormality When order blood gasses: ● acid-base problems ● artificial ventilation acute CNS change immediately look for ● hypoxemia ● hypoglycemia ● hyponatremia ● sepsis Priorities ● fluid volume and perfusion deficits ● correction of pH ● K, Ca, Mg ● Na, Cl Bleeding – transfusion strategy Indication: ● Transfuse any symptomatic patient (e.g., tachycardia, hypotension, CHF, angina) ● Asymptomatic, presurgical, stable patient ● Hemodynamically stable postsurgical stable patient ● Postsurgical patient at risk for ischemic disease (e.g., cardiac, bowel) ● Hemodynamically stable, nonpregnant, ICU patients >age 16 without ongoing blood loss Transfuse to Maintain: ● Until no longer symptomatic ● Hb 7-8 g/dl ● Hb 8 g/dl ● Hb 10 g/dl ● Transfuse at 7 g/dl to maintain Hb at 7-9 g/dl ● Estimated blood loss. ● Intraoperative fluids and blood products administered.