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Daily requirements

• For the ‘average’ 70 Kg man
  • Total body water is 42 L (~60% of body weight)
  • 28 L is in the intracellular and 14 L in the extracellular compartments
  • The plasma volume is 3 L
  • The extravascular volume is 11 L
  • Total body Na⁺ is 4200 mmol  (50% in ECF)
  • Total body K⁺ is 3500 mmol  (only about 50-60 mmol in ECF)
  • Normal osmolality of ECF is 280 –295 mosmol/kg

Fluid replacement

When calculating fluid replacement for a patients need to consider:

Maintenance requirements

• Daily maintenance fluid requirements vary between individuals.
  • 70 Kg male = 2.5 - 3.0L water, 120 – 140 mmol sodium and 70 mmol potassium
  • 40 Kg woman = 2.0L water,70 – 90 mmol sodium and 40 mmol potassium
• Daily maintenance fluid requirements for children
  • 0-10 kg is 100 ml/kg
  • 10-20 kg is 1000 ml + 50 ml/kg for each kg > 10
  • >20 kg is 1500 ml + 25 ml/kg for each kg > 20

Replacement of losses

• Pre-operative or pre-admission
• Ongoing losses
• Nasogastric aspirate
• Vomit, diarrhoea
• Stoma, drains, fistula etc
• Most ‘surgical ‘ ongoing losses are rich in sodium and should be replaced with 0.9% saline

Insensible losses

• Faeces approximately 100 ml/ day
• Lungs approximately 400 ml/ day
• Skin approximately 600 ml/ day

Composition of crystalloids

• 3L of Dextrose saline is not equivalent to 2L 5% Dextrose and 1L Normal saline
• 3L Dextrose Saline = 3L water and 90 mmol sodium
• 2L 5% Dextrose saline + 1L Normal saline = 3L water and 154 mmol sodium

Composition of colloids

• Monodispersed = All molecules of similar molecular weight
• Polydispersed = Molecules have spread of molecular weights

Albumin

• Monodispersed
• Expensive
• Long half life
• Accounts for 60-80% of normal plasma oncotic pressure
• No adverse effect on coagulation

Dextrans

• Polysaccharides
• Polydispersed with MW 10-90 kDa
• Reduces plasma viscosity
• Reduces platelet aggregation
• 1-5% develop anaphylaxis

Gelatins

• Polypeptides
• Polydispersed with MW ~35 kDa
• Rapidly lost from vascular space
• Hydroxyethyl starch
• Synthetic polysaccharide polymers derived from amylopectin
• Polydispersed with MW 50-450 kDa
• Large molecules engulfed by reticuloendothelial system
• Associated with bleeding diathesis

Assessment of adequacy of resuscitation

• Clinical history and observations – Pulse, blood pressure, skin turgor
• Urine output – oliguria < 0.5 ml/kg/hr
• CVP or pulmonary capillary wedge pressure
• Response of urine output or CVP to fluid challenge
• A fluid challenge should be regarded as a 200-250 ml bolus of colloid
• This should be administered as quickly as possible
• A response in the CVP or urine output should be seen within minutes
• The size and duration of the CVP response rather the actual values recorded is more important

GIFTASUP Recommendations (2008)

Recommendation 1

• Because of the risk of inducing hyperchloraemic acidosis in routine practice, when crystalloid resuscitation or replacement is indicated, balanced salt solutions (e.g. Ringer’s lactate/acetate or Hartmann’s solution) should replace 0.9% saline, except in cases of hypochloraemia

Recommendation 2

• Solutions such as 4% / 0.18% dextrose/saline and 5% dextrose are important sources of free water for maintenance, but should be used with caution as excessive amounts may cause dangerous hyponatraemia, especially in children and the elderly. These solutions are not appropriate for resuscitation or replacement therapy except in conditions of significant free water deficit (e.g. diabetes insipidus)

Recommendation 3

• To meet maintenance requirements, adult patients should receive sodium 50-100 mmol/day, potassium 40-80 mmol/day in 1.5-2.5 litres of water by the oral, enteral or parenteral route (or a combination of routes). Additional amounts should only be given to correct deficit or continuing losses. Careful monitoring should be undertaken using clinical examination, fluid balance charts, and regular weighing when possible

Preoperative fluid management

Recommendation 4

• In patients without disorders of gastric emptying undergoing elective surgery clear non-particulate oral fluids should not be withheld for more than two hours prior to the induction of anaesthesia

Recommendation 5

• In the absence of disorders of gastric emptying or diabetes, preoperative administration of carbohydrate rich beverages 2-3 h before induction of anaesthesia may improve patient well being and facilitate recovery from surgery. It should be considered in the routine preoperative preparation for elective surgery

Recommendation 6

• Routine use of preoperative mechanical bowel preparation is not beneficial and may complicate intra and postoperative management of fluid and electrolyte balance. Its use should therefore be avoided whenever possible

Recommendation 7

• Where mechanical bowel preparation is used, fluid and electrolyte derangements commonly occur and should be corrected by simultaneous intravenous fluid therapy with Hartmann’s or Ringer-Lactate/acetate type solutions

Recommendation 8

• Excessive losses from gastric aspiration or vomiting should be treated preoperatively with an appropriate crystalloid solution which includes an appropriate potassium supplement. Hypochloraemia is an indication for the use of 0.9% saline, with sufficient additions of potassium and care not to produce sodium overload. Losses from diarrhoea, ileostomy, small bowel fistula, ileus or obstruction should be replaced volume for volume with Hartmann’s or Ringer-Lactate/acetate type solutions. “Saline depletion,” for example due to excessive diuretic exposure, is best managed with a balanced electrolyte solution such as Hartmann's

Recommendation 9

• In high risk surgical patients, preoperative treatment with intravenous fluid and inotropes should be aimed at achieving predetermined goals for cardiac output and oxygen delivery as this may improve survival

Recommendation 10

• Although currently logistically difficult in many centres, preoperative or operative hypovolaemia should be diagnosed by flow-based measurements wherever possible. The clinical context should also be taken into account as this will provide an important indication of whether hypovolaemia is possible or likely. When direct flow measurements are not possible, hypovolaemia will be diagnosed clinically on the basis of pulse, peripheral perfusion and capillary refill, venous pressure and Glasgow Coma Scale together with acid-base and lactate measurements. A low urine output can be misleading and needs to be interpreted in the context of the patient’s cardiovascular parameters above

Recommendation 11

• Hypovolaemia due predominantly to blood loss should be treated with either a balanced crystalloid solution or a suitable colloid until packed red cells are available. Hypovolaemia due to severe inflammation such as infection, peritonitis, pancreatitis or burns should be treated with either a suitable colloid or a balanced crystalloid. In either clinical scenario, care must be taken to administer sufficient balanced crystalloid and colloid to normalise haemodynamic parameters and minimise overload. The ability of critically ill patients to excrete excess sodium and water is compromised, placing them at risk of severe interstitial oedema. The administration of large volumes of colloid without sufficient free water (e.g. 5% dextrose) may precipitate a hyperoncotic state

Recommendation 12

• When the diagnosis of hypovolaemia is in doubt and the central venous pressure is not raised, the response to a bolus infusion of 200 ml of a suitable colloid or crystalloid should be tested. The response should be assessed using the patient’s cardiac output and stroke volume measured by flow-based technology if available. Alternatively, the clinical response may be monitored by measurement/estimation of the pulse, capillary refill, CVP and blood pressure before and 15 minutes after receiving the infusion. This procedure should be repeated until there is no further increase in stroke volume and improvement in the clinical parameters

Intraoperative fluid management

Recommendation 13

• In patients undergoing some forms of orthopaedic and abdominal surgery, intraoperative treatment with intravenous fluid to achieve an optimal value of stroke volume should be used where possible as this may reduce postoperative complication rates and duration of hospital stay

Recommendation 14

• Patients undergoing non-elective major abdominal or orthopaedic surgery should receive intravenous fluid to achieve an optimal value of stroke volume during and for the first eight hours after surgery. This may be supplemented by a low dose dopexamine infusion

Postoperative fluid, and nutritional management.

Recommendation 15

• Details of fluids administered must be clearly recorded and easily accessible

Recommendation 16

• When patients leave theatre for the ward, HDU or ICU their volume status should be assessed. The volume and type of fluids given perioperatively should be reviewed and compared with fluid losses in theatre including urine and insensible losses

Recommendation 17

• In patients who are euvolaemic and haemodynamically stable a return to oral fluid administration should be achieved as soon as possible

Recommendation 18

• In patients requiring continuing i.v. maintenance fluids, these should be sodium poor and of low enough volume until the patient has returned their sodium and fluid balance over the perioperative period to zero. When this has been achieved the i.v. fluid volume and content should be those required for daily maintenance and replacement of any on-going additional losses

Recommendation 19

• The haemodynamic and fluid status of those patients who fail to excrete their perioperative sodium load, and especially whose urine sodium concentration is <20mmol/L, should be reviewed

Recommendation 20

• In high risk patients undergoing major abdominal surgery, postoperative treatment with intravenous fluid and low dose dopexamine should be considered, in order to achieve a predetermined value for systemic oxygen delivery, as this may reduce postoperative complication rates and duration of hospital stay

Recommendation 21

• In patients who are oedematous, hypovolaemia if present must be treated, followed by a gradual persistent negative sodium and water balance based on urine sodium concentration or excretion. Plasma potassium concentration should be monitored and where necessary potassium intake adjusted

Recommendation 22

• Nutritionally depleted patients need cautious refeeding orally, enterally or parenterally, with feeds supplemented in potassium, phosphate and thiamine. Generally, and particularly if oedema is present, these feeds should be reduced in water and sodium. Though refeeding syndrome is a risk, improved nutrition will help to restore normal partitioning of sodium, potassium and water between intra and extra-cellular spaces

Recommendation 23

• Surgical patients should be nutritionally screened, and NICE guidelines for perioperative nutritional support adhered to. Care should be taken to mitigate risks of the refeeding syndrome

Fluid management in acute kidney injury

Recommendation 24

• Based on current evidence, higher molecular weight hydroxyethyl starch should be avoided in patients with severe sepsis due to an increased risk of AKI

Recommendation 25

• Higher molecular weight hydroxyethyl starch should be avoided in brain-dead kidney donors due to reports of osmotic-nephrosis-like lesions

Recommendation 26

• Balanced electrolyte solutions containing potassium can be used cautiously in patients with AKI closely monitored on HDU or ICU in preference to 0.9% saline. If free water is required 5% dextrose or dextrose saline should be used. Patients developing hyperkalaemia or progressive AKI should be switched to non potassium containing crystalloid solutions such as 0.45% saline or 4%/0.18 dextrose/saline Ringer’s lactate versus 0.9% saline for patients with AKI

Recommendation 27

• In patients with AKI fluid balance must be closely observed and fluid overload avoided. In patients who show signs of refractory fluid overload, renal replacement therapy should be considered early to mobilize interstitial oedema and correct extracellular electrolyte and acid base abnormalities

Recommendation 28

• Patients at risk of developing AKI secondary to rhabdomyolysis must receive aggressive fluid resuscitation with an isotonic crystalloid solution to correct hypovolaemia. There is insufficient evidence to recommend the specific composition of the crystalloid.

Bibliography

Choi P T-L,  Yip G,  Quinonez L G,  Cook D J.  Crystalloids vs. colloids in fluid resuscitation:  a systematic review.  Crit Care Med 1999;  27:  200-210.

Jung B, Pahlman L, Nystrom PO et al. Multicentre randomized clinical trial of mechanical bowel preparation in elective colonic resection. Br J Surg 2007; 94: 689-695.

Lobo D N, Bostock KA, Neal KR et al. Effect of salt and water balance on recovery of gastrointestinal function after elective colonic resection: a randomised controlled trial. Lancet 2002; 359: 1812-1818.

Noblett S E, Snowden C P, Shenton B K et al. Randomized clinical trial assessing the effect of doppler-optimized fluid management on outcome after elective colorectal resection. Br J Surg 2006; 93: 1069-1076.

Schierhout G,  Roberts I,  Alderson P.  Colloids versus crystalloids for fluid resuscitation in critically ill patients (Cochrane Review). In: The Cochrane library,  Issue 1,  1999.  Oxford.

Traylor R J,  Pearl R G.  Crystalloid versus colloid versus colloid: All colloids are nor equal.  Anaesth Analg 1996;  83;  209-212.

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