Metabolic Acidosis in the Neonatal Period - Management of

Publication: 18/12/2013  --
Last review: 02/02/2017  
Next review: 02/02/2020  
Clinical Guideline
CURRENT 
ID: 3605 
Approved By: Trust Clinical Guidelines Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2017  

 

This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Management of Metabolic Acidosis in the Neonatal Period

Summary of Guideline

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Background

Definition
There is no established definition of metabolic acidosis, however a pH of <7.25 or base deficit worse than -10 (e.g. -12) with a normal / low pco2 may warrant treatment.

Aetiology
Metabolic acidosis is a common finding especially in the preterm infant. Acidosis occurs due

  1. To the loss of base from either renal or gastrointestinal routes.
  2. In renal failure due to the retention of acid.
  3. Through abnormal metabolism, leading to increased acid levels, for example lactate.

The regulation of acid base balance involves

  1. Body buffers,
  2. Respiratory function,
  3. Renal function.

The equation below demonstrates acid base balance.
CO2 + H2O <---> H2CO3<---> H+ +HCO3

Sodium bicarbonate often used to treat metabolic acidosis has been found to have possible adverse side effects. It is hyperosmolar, causing fluctuation in cerebral blood flow, leading to cerebral haemorrhage, especially when given rapidly or in large quantities. It may also cause hypernatraemia, and hypercarbia (also causing cerebral vasodilatation and increased cerebral blood flow).

Causes of Metabolic acidosis

  1. Hypoxia /cold stress leading to lactic acidosis.
  2. Sepsis.
  3. Hypovolaemia/ anaemia
  4. Prematurity, leading to immature renal function with inadequate hydrogen excretion, low bicarbonate reabsorption.
  5. Renal failure
  6. Inborn errors of metabolism.
  7. Dehydration
  8. Patent ductus arteriosus.

Prevention
Rather than treating metabolic acidosis the priority should always be to treat the underlying cause. (Aschner and Poland 2008)

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Diagnosis

Confirm the metabolic acidosis by an accurate recording of a blood gas, preferably arterial.

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Investigation

  1. Assess tissue perfusion should be < 2 seconds.
  2. Assess hydration - review intake vs. output.
  3. Assess electrolyte balance on recent urea and electrolyte levels. May need repeat U/Es. This will help assess renal function. Fluid bolus not to be used unless there is hypovolaemia, for example gut loses- gastroschisis.
  4. Review the cardiovascular status - blood pressure/ full blood count. May need blood transfusion (follow blood transfusion guideline).
  5. Assess risk factors for sepsis.
    1. Colour /perfusion
    2. Temperature instability
    3. Maternal risk factors
    4. Iatrogenic risk factors for example umbilical lines/ broviac/longlines etc.
    5. CRP, FBC, blood cultures.
  6. Treat underlying sepsis.
  7. Assess temperature control, if cold re warm slowly.
  8. Exclude inborn errors of metabolism.

If all of the above have been evaluated, and the infant continues to have a persistent metabolic acidosis, discuss with a senior member of the medical team: Consultant, SPR, ANNP.

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Treatment / Management

Commence a slow sodium bicarbonate infusion using the equation documented on the E formulary.

Half correction of acidosis = 0.3 x base deficit (mmol/L) x weight (kg)

In some cases of severe acidosis a full correction may be indicated. Please discuss with consultant.

Repeat blood 1 hour after completion of infusion to monitor response.

Once the Ph is> 7.25 or the base deficit <-10 discontinue the use of further infusions.

A continuous infusion should be considered if an infant has required more than x2 infusions daily. This can be calculated from the total dose given over the previous 24 hour period.

THAM (trometamol) is an organic buffer that may be used in pace of sodium bicarbonate. It should be used when serum sodium is above 150mmol/L or if the PCO2 is greater than 8kpa. It should also be considered in renal disease. See BNF for Cildren for further information.

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Definitions

THAM

Trometamol

U/Es

Urea and electrolytes

CRP

C reactive protein

ANNP

advanced neonatal nurse practitioner

SpR

specialist registrar

FBC

full blood count

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Provenance

Record: 3605
Objective:

Aims

To improve the diagnosis and management of metabolic acidosis in the newborn infant

Objectives

To provide evidence-based recommendations for appropriate diagnosis, investigation and management of metabolic acidosis to improve and streamline the management of babies with the condition.
To prevent the overuse of sodium bicarbonate infusions and subsequent complications.

Clinical condition:

Metabolic acidosis

Target patient group: Newborn infants on the neonatal unit
Target professional group(s): Secondary Care Doctors
Secondary Care Nurses
Adapted from:

Evidence base

  1. Ashner J, L, Poland R, L. Sodium Bicarbonate: Basically useless therapy.
    Pediatrics 2008 831-835
  2. Lawn C, L, Weir F, J, McGuire W. Base administration or fluid bolus for preventing morbidity and mortality in preterm infants with metabolic acidosis.
    Cochrane database assessed as up to date 25 August 2010.
  3. Lokesh L, Kumar P, Murki S, Narang A. A randomized controlled trail of sodium bicarbonate in neonatal resuscitation-effect on outcome. Resuscitation 60 (2004) 219-223
  4. Rennie J,M, Robertson’s Textbook of Neonatology Fourth Edition 2005 Elsevier Churchill Livingstone Philadelphia USA.

Approved By

Trust Clinical Guidelines Group

Document history

LHP version 1.0

Related information

Not supplied

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