Fluid and Electrolyte Balance during Injury

1. Fluid and Electrolyte Balance during Injury Zohair Al Aseri. MD. FCEM(UK).FRCPC (EM&CCM) Chairman ,National Emergency Medicine Committee Consultant, ICU Department of Critical Care College of Medicine, King Saud University Medical City. Riyadh, KSA.  zalaseri@ksu.edu.sa http://fac.ksu.edu.sa/zalaseri

2. Fluid and Electrolyte Balance during Injury • Objectives • Understand and inflammatory response to surgery and trauma • Understand normal regulation of fluid balance • Fluid Imbalance In Shock State • Fluid Therapy (Types) & Indication • Electrolyte disturbances in trauma and surgery • Acid base in surgery patients

3. Fluid and Electrolyte Balance during Injury Water depletion • Pure water depletion is common in surgical practice, and is usually combined with sodium loss. • The most frequent causes are inadequate intake or excessive gastrointestinal losses.

4. Fluid and Electrolyte Balance during Injury Water excess common in patients who receive large volumes of intravenous 5% dextrose in the early postoperative period. Such patients have an increased extracellular volume and are commonly hyponatraemic.

5. Fluid and Electrolyte Balance during Injury Water Excess: • Difficult to detect clinically • Patients with water excess usually remain well • Oedema may not be evident until the extracellular volume has increased by more than 4 litres.

6. Fluid and Electrolyte Balance during Injury Hypernatraemia: Normal sodium levels are in range 136-144mmol/l. Hypernatraemia (>145mmol) results from either water or hypotonic fluid loss or sodium gain.

7. Fluid and Electrolyte Balance during Injury Hypernatraemia: Water loss is commonly caused by • reduced water intake • vomiting, diarrhea • diuresis, burns • sweating and • insensible losses from the respiratory tract • diabetes insipidus. Typically associated with hypovolaemia

8. Fluid and Electrolyte Balance during Injury Hypernatraemia: Sodium gain is usually caused by excess sodium administration in hypertonic intravenous fluids Typically associated with hypervolaemia.

9. Fluid and Electrolyte Balance during Injury Hypovolaemic Hypernatraemia is treated with isotonic crystalloid followed by the more gradual administration of water to correct the relative water deficit. We can use 5%dextrose,1/2 NS or 1/4 NS

10. Fluid and Electrolyte Balance during Injury Cells, particularly brain cells, adapt to a high sodium concentration in extracellular fluid, and once this adaptation has occurred, rapid correction of severe hypernatraemia can result in a rapid rise in intracellular volume, cerebral oedema, seizures and permanent neurological injury.

11. Fluid and Electrolyte Balance during Injury Hyponatraemia (Na- < 135mmolfl) can occur with high, low or normal extracellular volume. The commonest cause is the administration of hypotonic intravenous fluids (as intravenous 5% dextrose) is administered in the postoperative period (dilutional hyponatraemia).

12. Fluid and Electrolyte Balance during Injury Hyponatraemia Other causes include diuretic use and (SIADH) Co-morbidities associated with secondary hyperaldosteronism, such as cirrhosis and congestive cardiac failure.

13. Fluid and Electrolyte Balance during Injury Sodium deficit This can be calculated as follows: 140- measured sodium x 0.2 x weight in kg where 0.2 refers to the 20% extracellular space which represents the compartment in which sodium is the main cation.

14. Fluid and Electrolyte Balance during Injury Hyponatraemia Treatment depends on correct identification of the cause: If ECF volume is normal or increased, the most likely cause is excessive intravenous water administration and this will correct spontaneously if water intake is reduced.

15. Fluid and Electrolyte Balance during Injury Hyponatraemia Although less common in surgical patients, SIADH promotes the renal tubular reabsorption of water independently of sodium concentration, resulting in inappropriately concentrated urine (osmolality> 100m0sm / l) in the face of hypotonic plasma (osmolality< 290m0sm/ l).

16. Fluid and Electrolyte Balance during Injury Hyponatraemia The urine osmolality helps to distinguish inappropriate ADH secretion from excessive water administration. 'Spot‘ measurement of urine sodium will be high.

17. Fluid and Electrolyte Balance during Injury Hyponatraemia In patients with decreased ECF volume, hyponatracmia usually indicates combined water and sodium deficiency. This is most frequently the result of • Diuresis • Diarrhea • Adrenal insufficiency Treatment by 0.9 sodium chloride

18. Fluid and Electrolyte Balance during Injury Hyponatraemia severe hyponatraemia (< 120mmol/ l) associated with confusion, seizures and coma.

19. Fluid and Electrolyte Balance during Injury Hyponatraemia Rapid correction of sodium concentration can precipitate an irreversible demyelinating condition known as central pontine myelinolysis Sodium concentration should not increase by more than 0.5 mmol/h.

20. Fluid and Electrolyte Balance during Injury Hyponatraemia This can usually be achieved by the cautious administration of isotonic (0.9%) sodium chloride, occasionally combined with the use of a loop diuretic (e.g. furosemide). Hypertonic saline solutions only for sever hyponatremia with CNS manifestation like seizure

22. Fluid and Electrolyte Balance during Injury Potassium 98% of total body potassium (around 3500mmol) is intracellular serum potassium concentration (normally 3.5-5 mmol/ l) is a poor indicator of total body potassium.

23. Fluid and Electrolyte Balance during Injury Potassium no absolute formula to determine K deficit. When the serum K is < 2.5mmol/ l about 100-200mmol of KCL will be needed in a 70kg adult. Serial monitoring of serum K is necessary to prevent overcorrection

24. Fluid and Electrolyte Balance during Injury Potassium Once the serum K comes above 3.0 mmol /1, K supplements can be reduced. Acidosis reduces Na+/kATpase activity and results in a net efflux of potassium from cells and hyperkalaemia. Conversely, alkalosis results in an influx of potassium into cells and hypokalaemia.

25. Fluid and Electrolyte Balance during Injury Hyperkalaemia This is a potentially life-threatening condition. caused by • exogenous administration of K • release of K from cells (transcellular shift) as a result of tissue damage or changes in the Na / K-ATPase function • impaired renal excretion.

26. Fluid and Electrolyte Balance during Injury Hyperkalaemia Mild hyperkalaemia (K" < 6mmol/l) is often asymptomatic. High K cause progressive slowing of electrical conduction in the heart and the development of significant cardiac arrhythmias. So ECG is mandatory in all suspected hyperkalaemia

27. Fluid and Electrolyte Balance during Injury Hyperkalaemia ECG Finding • Tall 'tented' T-waves in the precordial leads are the earliest • flattening (or loss) of the P waves • prolonged PR interval • widening of the QRS • asystole.

30. Fluid and Electrolyte Balance during Injury Hyperkalaemia Severe hyperkalaemia (K > 7m mmol/l) requires immediate treatment

31. Treatment of hyperkalaemia

32. Fluid and Electrolyte Balance during Injury Hypokalaemia common in surgical patients. Dietary intake of k is normally 60-80 mmol / day. Under normal conditions, the majority of k loss (> 85%) is via the kidneys Maintenance of K balance largely depends on normal renal tubular regulation.

33. Fluid and Electrolyte Balance during Injury Hypokalaemia K excretion is increased by • Metabolic alkalosis • Diuresis • Increased aldosterone release • Increased losses from the GI tract.

34. Fluid and Electrolyte Balance during Injury Hypokalaemia Diagnostic features • Muscle weakness • Paralytic ileus • Flattening of T waves • Prominent u waves

36. Fluid and Electrolyte Balance during Injury Hypokalaemia For every 3 K ions that come out from the intracellular compartment, one H and two Na ions are exchanged causing extracellular alkalosis and intracellular acidosis.

37. Fluid and Electrolyte Balance during Injury Hypokalaemia Treatment Oral or NG potassium replacement in mild hypokalaemia. • Severe (K" < 2.5 mmol/1) or symptomatic hypokalaemia requires IV replacement.

38. Fluid and Electrolyte Balance during Injury

39. Fluid and Electrolyte Balance during Injury Calcium Clinically significant abnormalities in endocrine surgery.

40. Fluid and Electrolyte Balance during Injury Magnesium Hypomagnesaemia is common in • restricted oral intake • intra­venous fluids for several days

41. Fluid and Electrolyte Balance during Injury Magnesium It is frequently associated with other electrolyte abnormalities, notably hypokalaemia, hypocalcaemia and hypophosphataemia.

42. Fluid and Electrolyte Balance during Injury Hypomagnesaemia associated with arrhythmias (most notably torsades de pointes (polymorphic ventricular tachycardia) and atrial fibrillation) Manifestations of are nonspecific (muscle weakness, muscle cramps, altered mentation, tremors, hyperreflexia and generalized seizures).

43. Fluid and Electrolyte Balance during Injury Hypomagnesaemia When hypokalaemia and hypomagnesaemia coexist it may be difficult to correct the former without correcting the latter.

44. Fluid and Electrolyte Balance during Injury Phosphate Phosphate is a critical component in many biochemical processes such as ATP synthesis, cell signaling and nucleic acid synthesis.

45. Fluid and Electrolyte Balance during Injury Hypophosphataemia common in surgical patients Severe (< 0.4 mmol/1) causes • widespread cell dysfunction, • muscle weakness, • impaired myocardial contractility, • reduced cardiac output • altered sensorium.

46. Fluid and Electrolyte Balance during Injury Hypophosphataemia most commonly occurs in malnourished and/ or alcoholic patients commencing enteral or parenteral nutrition. Sepsis is another situation in which marked hypophosphataemia can be seen

47. Fluid and Electrolyte Balance during Injury Hypophosphataemia refeeding syndrome Hypophosphataemia accompanied by fluid retention and an increase in ECF volume To avoid it feeding should be established gradually with measurement and supplementation of serum electrolytes (phosphate, magnesium and potassium).

48. Fluid and Electrolyte Balance during Injury Hypophosphataemia Treatment Phosphate can be supplemented orally or by slow intravenous infusion.

49. Fluid and Electrolyte Balance during Injury Acid-base balance Acidosis ('acidaemia' if plasma pH< 7.35) Alkalosis ('alkalaemia' if plasma pH> 7.45). Both acidosis and alkalosis may be respiratory or metabolic in origin.

50. Fluid and Electrolyte Balance during Injury Acid-base balance VBG is good, ABG is more accurate coupled with measurement of blood lactate concentration