PERIOPERATIVE FLUID MANAGEMENT IN PAEDIATRICS : CHANGING CONCEPTS
Children undergoing surgery require fluid & blood administration to maintain normal homeostasis.
Paediatric population is heterogenous so one formula may not suffice. The physiological differences between the adult & paediatric population needs to be understood.
Fluid management should be based on the physiology & pathology of the child along with their perioperative needs
The guidelines for fluid & blood administration in children are based on safety & efficacy
The objective is to maintain or re-establish the child’s normal physiological state i.e. normovolaemia, normal tissue perfusion, normal metabolic function, normal acid-base & electrolyte status
Children have a higher metabolic rate, larger surface area to weight ratio and faster respiration resulting in extensive fluid losses which translates to higher fluid requirement.
Fluid is mainly given for perioperative deficits like fasting, third space loss & blood Loss.
PHYSIOLOGICAL CONSIDERATIONS :
There are two fluid compartments – Intracellular (ICF) and Extracellular (ECF)
ECF is further divided into three compartments – plasma , interstitial & transcellular fluid.
Total body water (TBW) is 80% of body weight (BW) in preterm neonate and it is 60% of BW in children after 6 months of age. Total body water decreases with age because of loss of water, mainly from ECF compartment. ECF accounts for 1/3rd of TBW and is larger in children than adults.
Sodium (Na) is the primary cation and chloride (Cl ) is the primary anion of the ECF.
The intracellular compartment (ICF) consists mainly Potassium (K), Magnesium (Mg) , Proteins & phosphates.
Interstitial fluid has low proteins but is otherwise similar to ICF.
Glomerular filtration rate (GFR) in a term neonate reaches adult levels only by two years of age. The low GFR is because of decreased capillary surface area for filtration, low systemic arterial pressure, high renal vascular resistance resulting in low ultrafiltration pressure. The concentrating ability is low at birth and with further water deprivation, urine concentrates to only 600–700 mOsm/kg because of hypotonicity of renal medulla.
In 1957, the American paediatricians Holliday and Segar first provided calculations for ‘the maintenance need for water in parenteral fluid therapy’ and derived the 4-2-1 rule from the caloric expenditure of children. 4ml/kg/h for the first 10 kg of weight, 2ml/kg/h for the next 10 kg, and 1ml/kg/h for each kilogram thereafter.
|Hourly 4/2/1 rule and fluid requirement|
|Weight||Fluid Requirements per hr|
|< 10 kg||4 ml/kg|
|10-20 kg||l + 2 ml/kg for each kg above 10 kgs|
|>20 kg||60 ml + 1 ml/kg for each kg above 20 kgs|
They then analyzed the composition of human and cow’s milk to calculate the maintenance needs for electrolytes, and in the following years this led to the common practice of using hypotonic electrolyte solutions with glucose 5% for maintenance infusion in children.
In the 1990s, this practice was questioned because of reports about postoperative hyponatraemic encephalopathy as a consequence of infusion of hypotonic electrolyte solutions and stress-induced elevated antidiuretic hormone (ADH) levels leading to cerebral oedema and respiratory insufficiency.
In addition, other authors found that the intraoperative use of electrolyte solutions with glucose 5% was associated with hyperglycaemia, whereas the use of lower glucose concentrations of 1–2% was sufficient to maintain plasma glucose concentrations within the physiological range and to prevent a compensatory increase in lipid mobilization.
As a consequence, several working groups recommended the use of isotonic electrolyte solutions with lower glucose concentrations of 1– 2% for intraoperative maintenance infusion as a pragmatic approach to prevent any hyponatraemia, hypoglycaemia, lipolysis and hyperglycaemia.
Preoperative fasting is essential to reduce the risk of aspiration.
Clinical studies have shown that excessive fasting is not uncommon in children presenting for surgery. Prolonged preoperative fasting times were associated with ketoacidosis
The guidelines recommend that the perioperative fasting times for children should be as short as possible to prevent patient discomfort, dehydration and ketoacidosis without increasing the incidence of pulmonary aspiration.
Studies have shown that the stomach empties itself within 1 hr of clear fluids and so children can be allowed to drink clear fluids until 1 hr before the surgery safely.
The recommendation for other fluids and solids are mentioned in the Table 2
Recommendations on preoperative fasting guidelines
|Type of food||Hours of fasting||Recommendation|
|Heavy Solids||8 hrs||A|
|Light meals (solids)/Formula milk/juice with pulp||6 hrs||A|
|Breast Milk||4 hrs||A|
|Clear fluids (water, fruit juices without pulp, carbonated beverages, clear tea, and black coffee excluding alcohol)||1 hr||A|
If preoperative and postoperative fasting times are short, perioperative IV fluid therapy is not required in children beyond neonatal age who drink sufficient volumes and undergo short procedures (<1 h) with a venous access in place.
If the child is fasting for >6 h appropriate volume of fluid can be administered based on the degree of dehydration (1% dehydration = 10 ml/kg fluid loss).
For preoperative fluid resuscitation it is recommended that glucose free crystalloid containing sodium in the range of 131–154 mmol/L is administered in a bolus of 20 ml/kg over 10 min in children and 10 ml/kg over 10 min in neonates for a maximum of 40–60 ml/kg provided there is no pre-existing cardiac and renal disease.
Use of Transthoracic Echo for preoperative fluid assessment is a becoming a common tool in combination with clinical parameters. Clinical assessment of dehydration guides us towards the fluid management and can be easily done at the bedside
Assessment of dehydration in Paediatrics
|Severity of Dehydration||% Dehydration Infant||% Dehydration Child||Symptoms|
|Mild||5||3-4||Thirst. mucous membranes moist, EJV visible in supine, CRT >2 sec, Urine sp gr >1.020|
|Moderate||10||6-8||Dry mucous membranes, ↑ HR, ↓ tears, Sunken fontanelle, Decreased skin turgor, CRT 2-4 sec, ↓Urine Output|
|Severe||15||10||Eye sunken, cool peripheries, apathy, somnolence, orthostatic to shock|
|Shock||>15||>10||Decompensation, Poor O2 delivery, ↓BP|
INTRAOPERATIVE FLUID MANAGEMENT :
All guidelines (APA & NICE) recommend intraoperative fluid calculations depending on Holliday – Segar Formula
Infusion of isotonic solutions is recommended.
NICE guidelines recommend restriction of fluids by 50 to 80% because of water retention due to non-osmotic ADH secretion. The German guidelines recommend administration of balanced electrolyte solution with 1–2.5% dextrose at the rate of 10 ml/kg/h as an initial infusion followed by adjustment in rate based on requirement.
Association of Paediatric Anaesthetists of Great Britain and Ireland (APA) consensus guidelines and European consensus statement guidelines recommend intraoperative use of low dextrose (1–2.5%) containing isotonic fluids which have been shown to maintain acceptable blood glucose levels and prevent electrolyte imbalances during surgery.
There is a growing consensus that intraoperative dextrose is selectively administered only in those patients at greatest risk for hypoglycaemia and where required one should consider the use of fluids with lower dextrose concentrations (e.g. 1% or 2.5%). The populations at highest risk of hypoglycaemia include neonates, children receiving hyperalimentation, and those with endocrinopathies, in whom monitoring blood glucose levels and adjusting the rate of infusion is also recommended.
Neonates require dextrose-containing fluid during surgery because they require 4–8 ml/kg glucose for brain development. In addition, limited glycogen reserve makes the neonate susceptible to hypoglycaemia without glucose supply.
Routine dextrose administration is now no longer advised for healthy children receiving anesthesia even in neonatal period.
Replacement Therapy :
According to the APA guidelines, replacement for intraoperative losses is with isotonic solutions and colloids or blood based on the child’s hematocrit. The 3rd space loss (its existence is a matter of debate) due to sequestration of fluid from vascular space into tissues around the surgical site is difficult to quantify and is roughly estimated as 2 ml/kg/h for superficial surgery, 4–7 ml/kg/h for thoracotomy and 5–10 ml/kg/h for abdominal surgery.
The NICE guidelines only mention replacement of ongoing losses with isotonic saline without mentioning the rate of fluid administration. Sumplemann et al. recommend that in patients with circulatory instability balanced isotonic electrolyte solutions without glucose can be given as repeat-dose infusions of 10–20 ml/kg until desired effect is obtained
If the volume of crystalloids exceeds then to avoid interstitial fluid overload, leading to haemodilution and decrease in oxygen supply, colloids like albumin, gelatin, HES 130 are used as repeat dose infusions. However, the total dose should not exceed 10–20 ml/kg (not to exceed 50 ml/kg dose).
Choice of isotonic fluids :
The most commonly available isotonic fluids include 0.9% normal saline, ringer lactate, and plasmalyte.
0.9% saline is the most commonly available and the cheapest fluid available, but it has excess of chloride and absence of bicarbonate precursor. Infusion of large volumes results in suppression of RAS, renal blood flow and in effect leads hyperchloremic acidosis.
Children undergoing major pediatric and neurosurgeries have shown better acid-base status with balanced crystalloids like plasmalyte and ringer lactate.
As compared with lactate, metabolization of acetate (Plasmalyte) is significantly faster, more independent of hepatic function, with a lower increase in oxygen consumption and no interference with the diagnostic use of lactate as a marker of low tissue perfusion. Most of the anesthetic drugs are compatible with acetate except phenytoin and diazepam.
After administration of a total of 30–50 ml/kg− 1 of crystalloid solution, the administration of a colloid solution (albumin or synthetic colloid) to maintain intravascular osmotic pressure is indicated.
Albumin remains the main colloid used in the neonatal period and early infancy for volume expansion. However, its use is restricted in view of high cost and possibility of it carrying other sources of infection.
In hypotensive premature infants, 5% albumin was shown to be more effective than 20% albumin.
Thus 5% albumin remains the preferred colloid in young infants as it is iso-oncotic to plasma and very effective to maintain blood pressure and plasma colloid perfusion pressure.
A meta-analysis opined that intravascular volume expansion with low molecular weight 6% HES did not appear to modify renal function, blood loss or transfusion when administered to children during the peri-operative period
However further studies are still required
There is no role for non-emergent use for volume replacement with colloids and no advantage of one colloid over the other in preventing shift of fluids to interstitial space.
BLOOD & BLOOD PRODUCTS :
The requirement of blood transfusion depends on many factors like age, quantity of blood loss, the baseline haemoglobin concentration and different blood physiology. Neonates and infants have higher blood volume per weight but are less tolerant of the loss. Also, the metabolic rate and baseline oxygen demands are greater than adults. Preoperative iron deficiency anaemia is more prevalent in this population and increases the risk of blood transfusion requirement intraoperatively. Neonatal haemoglobin (Hb) is more than 70% foetal Hb in term neonates compared to 90% in preterms implying decreased oxygen delivery to the tissues.
Normal blood volume in neonates and children
|Preterm neonate||90 ml/kg|
|Full term neonate – 3 months||80-90 ml/kg|
|Above 3 months||70-80 ml/kg|
|Above 2 years||70 ml/kg|
Initially when there is bleeding, 2:1 regimen for volume of colloids to be transfused when compared to crystalloids. After the bleeding has crossed 20% of blood volume preferred ratio of crystalloid to colloid is 1:1.
The decision when to transfuse blood to children depends on the maximum allowable blood loss (MABL) calculated as: MABL = EBV × (H0 – H1)/H0 (EBV = estimated blood volume; H0 = starting Hct; H1 = lowest acceptable Hct).
Transfusion Trigger is usually accepted to be around hemoglobin of 7-8 g/dl in children having intraoperative loss. Current evidence for optimum haemoglobin threshold in neonates is controversial and evolving (12 g/dL).
The volume of packed cells required is calculated as body weight (kg) × desired increment in hemoglobin (g/dl) × 5
Low cardiac output and low blood pressure should be treated immediately as it can lead to decreased tissue oxygen delivery. Hence, prompt fluid management and initiating vasopressors is of prime importance.
POST OPERATIVE MANAGEMENT:
Shortening of the fasting time should also be extended into the postoperative period.
Oral fluids should be restarted as early as possible.
The American Academy of Pediatrics (AAP) recommends in a recently published guideline that patients 28 days to 18 years of age requiring maintenance intravenous fluids postoperatively should receive isotonic solutions with appropriate potassium chloride and dextrose as they significantly decrease the risk of developing hyponatremia.
Preoperative deficit to be calculated on a case-to-case basis
- ESA/ASA Guidelines for preoperative fasting – Clear fluids may be given up till 1 h
- Holiday and Segar – 4/2/1 rule to give a general direction
- Clinical Assessment of dehydration and its correction
Isotonic Fluids the mainstay of maintenance fluids
- 1-2% Dextrose may be added if there is possibility of hypoglycaemia
- Routine Dextrose administration no longer advised.
- Postop – Early restarting of enteral feeding
- If intravenous fluids need to be continued – Prefer Isotonic Fluids
- Perioperative fluid therapy should be based on the patient’s physiology, type of surgery & focused on maintaining normal homeostasis.
- Preoperative & postoperative fasting times have to be optimized.
- Use of balanced isotonic electrolyte solutions with or without glucose are preferred
- Use of colloids in children is not extensively studied & should be used in a guarded manner
- The decision for blood transfusion in children depends on the preoperative Hb, type of surgery and maximum allowable blood loss (MABL)
Perioperative fluid therapy in paediatrics
Paediatric Anaesthesia, Wiley Online Library
First published: 18 March 2008 https://doi.org/10.1111/j.1460-9592.2008.02505.xCitations: 63
Isabelle Murat, MD, PhD, Department of Anesthesia, Hôpital Armand Trousseau, 26 avenue Arnold Netter, 75012 Paris, France (email: firstname.lastname@example.org).
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