Basic Concepts of Fluid and Electrolyte Therapy

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50 Patients receiving artificial nutrition (parenteral or enteral) usually receive an adequate amount of water and electrolytes via the feed and most do not require additional intravenous fluids. It is a common mistake to prescribe intravenous maintenance requirements in addition to the water and electrolyte content of the feed, leading to avoidable fluid overload. (2) This question is crucial. Many patients are fluid overloaded because prescriptions based on resuscitation are continued thoughtlessly when maintenance fluids are all that is required. Tables 1 and 2 in Chapter 1 show how low such maintenance requirements are. For example 1 litre of 0.9% saline contains enough salt to meet 2 days’ normal maintenance requirements. Intravenous fluid therapy may be needed for resuscitation, replacement or maintenance, depending on the stage of the illness (Fig. 6). Inadequate replacement Replacement Adequately resuscitated, but ongoing losses Resusciation Adequate replacement, no ongoing losses Inadequate maintenance/ ongoing losses New losses (e. g. haemorrhage) Adequately resuscitated, no ongoing losses Maintenance Intravenous fluids no longer required Oral maintenance Figure 6: The relationship between resuscitation, replacement and maintenance.
a. Resuscitation: In the event of blood loss from injury or surgery, plasma loss e.g. from burns or acute pancreatitis, or gastrointestinal or renal losses of salt and water, a resuscitation regimen is needed to restore and maintain the circulation and the function of vital organs. In this situation, the recommendation is to infuse 500 ml (250 ml if cardiac failure) of a balanced crystalloid stat (e.g. Hartmann’s solution or Ringer’s lactate) rapidly. If hyperkalaemia is present (K + >5.5 mmol/l) or suspected oliguric AKI or rhabdomyolysis 0.9% saline is preferred initially (no potassium in crystalloid). However, there is no evidence that administration of crystalloids containing 3-5 mmol/l of K + worsen the hyperkalaemia. The clinical response should be assessed immediately following administration of the fluid bolus in terms of improved peripheral perfusion, decreased pulse rate, rise in blood pressure, rise in JVP and increase in urine output. Further administration will depend on response (Fig. 7). If 0.9% saline has been used initially conversion to a balanced crystalloid can be considered once potassium concentrations are known and good urine output established. In the case of intravascular fluid losses, colloids or a combination of colloids and crystalloids are appropriate to avoid causing excessive rises in oncotic pressure and potential osmotic nephrosis (renal tubular injury). Large volumes of 0.9% saline are best avoided, except after gastric losses, because of the risk of producing hyperchloraemic metabolic acidosis and its undesirable sequelae. In the case of major blood loss it is also necessary to cross match and to give packed cells. Early and adequate treatment of the underlying cause of fluid loss, e.g. control of bleeding, is vital. In the severely injured patient, resuscitation of blood loss with packed cells, fresh frozen plasma and platelets in a ratio of 1:1:1 has been shown to be more beneficial than packed cells alone, as this helps correct the associated coagulation defects. 51
Page 1 and 2: Dileep N. Lobo Andrew J. P. Lewingt
Page 3 and 4: Basic Concepts of Fluid and Electro
Page 5 and 6: Foreword This book, ‘Basic Concep
Page 7: Table of Contents 1. Normal Physiol
Page 10 and 11: ever, contains large anions such as
Page 12 and 13: Oral intake 1.5-2 L Saliva 1.5 L Ga
Page 14 and 15: Table 2: Normal maintenance require
Page 16 and 17: Kidney: this is the main organ for
Page 18 and 19: Conversely, if the intake of Na + i
Page 20 and 21: volume at all costs. It also explai
Page 22 and 23: Conclusion Appropriate fluid therap
Page 24 and 25: Intravascular fluid volume - the to
Page 26 and 27: Colloid - a fluid consisting of mic
Page 28 and 29: Base excess - Base excess is define
Page 30 and 31: Parameter Urine output Significance
Page 32 and 33: Figure 5: Example of a vital signs
Page 34 and 35: Fluid balance charts These provide
Page 36 and 37: Osmolality In the presence of AKI,
Page 38 and 39: Chloride Despite the fact that seru
Page 41 and 42: 4. Properties of Intravenous Crysta
Page 43 and 44: 6-12 h. The colloid should be metab
Page 45 and 46: Table 8: Advantages and disadvantag
Page 47: Plasma- Sterofundin 0.18% Plasma-Ly
Page 52 and 53: Once resuscitation has been achieve
Page 54 and 55: (3) The answer to this question is
Page 57 and 58: 6. Methods of Fluid Administration
Page 59 and 60: Central Modern single or multi lume
Page 61 and 62: 7. Acid-Base Balance Introduction M
Page 63 and 64: vide a simple description of the mo
Page 65 and 66: change in Pco 2 = respiratory proce
Page 67 and 68: Table 15: Causes of metabolic acido
Page 69 and 70: Renal HCO 3 - loss results from re
Page 71: Mixed acid-base disorders These are
Page 74 and 75: Urine output should be interpreted
Page 76 and 77: assess clinical response to fluid i
Page 78 and 79: Oliguria following surgery 48 h and
Page 80 and 81: Definition AKI is a result of a rap
Page 82 and 83: AKI is most commonly secondary to a
Page 84 and 85: History Examination Investigations
Page 86 and 87: Management Prevention Any patient a
Page 88 and 89: if no clinical response and no pulm
Page 90 and 91: acidosis pH 7.2-7.4 - there is ver
Page 92 and 93: Referral to nephrologist NOT all p
Page 94 and 95: Follow up Acute kidney injury is a
Page 96 and 97: DKA and HONK represent the two extr
Page 98 and 99: Fluids and insulin In the absence
Page 100 and 101:
Surgery in the patient with diabete
Page 102 and 103:
10 mmol/l/day. In the differential
Page 104 and 105:
portionately more water is lost tha
Page 106 and 107:
Hypokalaemia: a fall in serum conce
Page 108 and 109:
Four common aspects of Ca 2+ disord
Page 110 and 111:
Treatment depends on severity and c
Page 112 and 113:
112
Page 114 and 115:
Hypophosphataemia
Page 116 and 117:
116
Page 118 and 119:
Prolonged periods of preoperative f
Page 120 and 121:
position to postoperative parotitis
Page 122 and 123:
13. *Chowdhury AH, Lobo DN. Fluids
Page 124 and 125:
42. Hussein H, Lewington A, Kanagas
Page 126 and 127:
67. *Michell AR. Diuresis and diarr
Page 128 and 129:
94. *Stewart PA. Modern quantitativ
Page 130 and 131:
colloids 7, 26, 41, 42, 43 44, 45,
Page 132 and 133:
intravascular compartment 20, 41, 4
Page 134 and 135:
Stewart approach 63, 71 sympathetic
Page 136:
Dileep N. Lobo Andrew J. P. Lewingt
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Basic Concepts of Fluid and Electrolyte Therapy

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