The Ulster Medical Journal, Volume 72, No. 2, pp. 69-72, November 2003.

EditorialPrevention of hyponatraemia in children receiving fluid therapy

Severe hyponatraemia (serum sodium <130 mmol/1)has become increasingly recognised in recentyears as a potential complication of fluid therapyin children,' and at least two children in NorthernIreland have died in recent years as a result.Worldwide, death or neurological morbidityrelated to this condition has recently been reportedin more than 50 children.2 Hyponatraemia hasalso been reported in as many as 5% of adultsundergoing elective surgery3 and in 25% ofchildren following spinal fusion.4 It has beensuggested that menstruant women and prepubertalchildren are particularly at risk of brain damagein this situation.5 Although risk factors includevomiting, pain, anxiety, disturbances ofthe centralnervous system and metabolic and endocrinedisorders, it has become recognised that anychild receiving intravenous fluids or oralrehydration is potentially at risk. The particularrisks associated with the post-operative periodwere highlighted by Arieff who pointed out thatplasma levels of vasopressin (antidiuretichormone, ADH) are elevated in virtually everychild in the post-operative period.5 Ifsuch childrenare given fluids containing less than 140 mmol/lofsodium there will always be a tendency towardspost-operative hyponatraemia.The complex inter-relationships between multiplefactors influencing decisions regarding fluid andelectrolyte management in children are describedin standard texts. These result in difficulty inestablishing simple guidelines for fluidadministration in children. A solution containing0.18% sodium chloride in 4% glucose hascommonly been used in paediatric practice and isgenerally held to be isotonic. However, in thecatabolic child the glucose is metabolised rapidlycausing the fluid to become hypotonic in vivo,with the potential for significant fluid shifts. Ifthe child is in the post-operative period or in anyother situation where there is a high level ofcirculating vasopressin a situation can arise whereexcess free water is retained within the circulation.This can be compounded by water effectivelyadministered in the intravenous fluids. Thiscondition has been called 'dilutionalhyponatraemia" because the free" water

component of the serum has increased, causingdilution of the major cation, sodium. This free"water will pass rapidly and unhindered acrosscell membranes with the particular risk ofdevelopment of cerebral oedema. Children maybe at particular risk of brain damage due toincrease in intracranial pressure in this situation.2

GUIDANCE AND ADVICE

A Working Group in Northern Ireland hasdeveloped guidelines (figure), which have beenpublished by the Department of Health, SocialServices and Public Safety, and can bedownloaded from the internet.6 These guidelinesemphasise that every child receiving intravenousfluids requires a thorough baseline assessment,that fluid requirements should be assessed by adoctor competent in determining a child's fluidrequirement, and fluid balance be rigorouslymonitored. They emphasise the value of accuratemeasurement of body weight and monitoring ofserum urea and electrolytes in any child requiringprescribed fluids after 12 hours, together with theimportance of assessment of fluid balance andprescription at least every 12 hours by anexperienced member of clinical staff. Thisassessment needs to take account of all oral andintravenous intake, together with the measurementand recording of all losses (including urine,vomiting, diarrhoea, etc.) as accurately aspossible.

While general guidance can be given regardingmaintenance fluid requirements in children ofdifferent weights, these must be assessed in theclinical context of each individual child.Requirements for water and electrolytes shouldbe considered separately and an appropriatesolution chosen. Although the baselinemaintenance requirement for 2 to 3 mmol/kg/dayof sodium can be applied to children of all ages,the amount of water needed varies with weight. Itwill readily be apparent that this means that theconcentration of sodium in the maintenance fluidhas to be different for children of different agesand weights. For example, an infant of 5 kgrequires 150 ml/kg/day of water, so the dailysodium requirement will be provided by a fluid

C The Ulster Medical Society, 2003.

70 The Ulster Medical Journal

rVA WI--g o 0 !g

0 trIo ra 22,:3 CL C> EE'S 4F 0

0 Cc 0 e to -.1-- 'r-C CL. r -0 0

'A 0 0c LU: d)t0 0

IA4 >

in 0 UI.O.: crA

-0 MvS &. -a M -1 a I., E0 C U E -c -0

(A

La r=0 0 LUVs M .0

0-cr L. go- I (A' $A CL's

tra M: 00

u44 u

M0 .oc0 'A P 10E 2 v u

u 0 w s EWA 0 IA19o M ou E

0 U

>1, Ad )R% 4i c75 a AM' s 0 LUc CaPlill 0 .5; E

0 CL 8E if jj E -C

0 00 C - E M 2u C

MC

CL cL, .0 0S;AA =-U CLCL.2 0:. M

c la0> SC S

M

TC

E Em MOMA- cC) Z:M Lp 0 te

tio %-X14Jr 0 0

c 0 - CL 0 ;ojU. EV z 0 V v -0 = M E C

Mw = .3 W u 2% loW6 0=4-m La li tw mA T C0 :0 C cv.0'wc c It0 oAu E .2 ci.0 E 0

CL., E 04-P u .0C

E .4 12"E. CL 0

MO C.;Ln C

0 0

EVA

DO 4'IA 0Ul

0 0 2: 12 otv P -

0 .0U,5 G.L.- #AC CL d

t: 00 -2E

0.0C

0tg -C -qA Li ON 0 0 100 0 0

C ul0 C C C Z EG,-:. - 0 = 04) MOu tq u96 xtA10 Ci Ca 0 0u .9 =

4o 0, 415E

C0

V 0tg .E > 0Li In#A -- E .12 EO 0.9 E-8 CL CL U A C >u 2-0 CL 4) 4)

v E > LUL 0 0 0 00 0 'rA CLI- z

.'ACA 0 E

4-P0

g.= 40 10 LUE cn cL'W v COL Ca0 0co in 0 U -D, CA

i) The Ulster Medical Society, 2003.

Prevention of hyponatraemia in children receiving fluid therapy

containing 15 to 20 mmol/1 of sodium. Thestandard 0. 18% saline solution contains 30 mmol/1 and so will adequately provide for thisrequirement. On the other hand, a child of 40 kgrequires 50ml/kg/day, so a solution containing 3times as much sodium will be needed to provideadequate maintenance sodium. A solutioncontaining 0.18% saline will thus not provideadequate sodium to maintain the normal plasmalevel in the older child unless there are clinicalreasons to limit sodium intake. This would requireinstead a solution containing 40 to 60 mmol/1.Halfnormal saline contains 75 mmol/1 of sodium.

Replacement fluids must reflect fluid loss, and inmost situations this will imply a minimum sodiumcontent of 130 mmol/1. This must be consideredand prescribed separately, reflecting the fluidloss in both volume and composition. In somesituations laboratory analysis of the electrolytecontent of the fluid lost may be helpful.

It is important to remember that, while childrenreceiving intravenous fluids are at particular risk,children receiving oral rehydrating fluids mayalso be at risk as these are invariably hypotonic.Vigilance is therefore required for all childrenreceiving fluids. Medical and nursing staff needto be aware of risks in this situation, and of earlysigns of developing cerebral oedema such asvomiting, deteriorating level of consciousness orheadache before more serious symptoms such asseizures occur, as deterioration to this extent isassociated with significant morbidity andmortality.

Particular attention needs to be given to fluidmanagement in specific situations such as diabeticketoacidosis, renal failure and in the newborn,but attention to detail in assessment andmanagement of intravenous and oral fluids in allchildren where these are required for medical orsurgical reasons is essential to minimise the risksassociated with hyponatraemia. It must be clearlyrecognized that prevention is quite different fromtreatment of hyponatraemia. All those workingwith children must be familiar with good practicetoprevent hyponatraemia but not all will have thenecessary expertise in treating a child withhyponatraemia which can be extremely complex.Ifconcern is raised regarding clinical deteriorationor biochemical abnormality then advice and

Consultant Chemical Pathologist.

We recommend that complications and criticalincidents related to intravenous fluids are reportedto the Medicines Control Agency (MCA) in thesame way as drug side-effects, by using theyellow card'"ystem. Fluids are included in theBritish National Formulary and are under theregulatory authority of theMCA. This will permita nationwide analysis of the problem and alsodirect information to clinicians. When one of thedeaths locally was reported to the MCA theAgency was asked to consider issuing a hazardwarning"about the use of a solution containing0. 18% sodium chloride in 4% glucose in childrenfollowing surgery. After due consideration theMCA replied that electrolyte imbalance is a riskwith the use of all intravenous solutions. TheMCA Working Group on Paediatric Medicinesadvised that there should be no amendments toproduct information (personal communication).CONCLUSION

It is important that all doctors caring for childrenare aware of current literature and advice inrelation to the rare but serious condition knownas Dilutional Hyponatraemia'A complex neuro-endocrine response in susceptible children canoccur where the free" water component ofintravenous fluids can cause a sudden andunheralded decrease in the serum sodiumconcentration. Preventative measures to avoidthis potentially fatal condition need to be institutedin all units caring for children.7

JG Jenkins, B Taylor, M McCarthy

J G Jenkins, MD, FRCP, FRCPCH, FRCPI, Senior Lecturerin Child Health, The Queen's University of Belfast.Consultant Paediatrician, Antrim Hospital, Antrim,BT41 2RL.

B Taylor, MB, MA, FFARCSI, Consultant PaediatricIntensivist, Royal Belfast Hospital for Sick Children,Belfast BT12 6BE.

M McCarthy, MB, BCH, BAO, MRCGP, MPH, SeniorMedical Officer, Department of Health, Social Servicesand Public Safety, Castle Buildings, Belfast BT4 3SJ.

Correspondence to Dr Jenkins.

clinical input should be obtained from a seniormember ofmedical staff, for example a ConsultantPaediatrician, Consultant Anaesthetist or

C The Ulster Medical Society, 2003.

71

72 The Ulster Medical Journal

REFERENCES

1. Halberthal M, Halperin M L, Bohn D. Lesson of theweek. Acute hyponatraemia in children admitted tohospital: retrospective analysis of factors contributingto its development and resolution. Brit Med J 2001;322(7289): 780-2.

2. MoritzM L, Ayus J C. Prevention ofhospital-acquiredhyponatremia: a case for using isotonic saline.Pediatrics 2003; 111(2): 227-30.

3. Chung H M, Kluge R, Schrier R W, Anderson R J.Postoperative hyponatraemia. A prospective study.Arch Intern Med 1986; 146(2): 333-6.

4. Burrows F A, Shutack J G, Crone R K. Inappropriatesecretion of antidiuretic hormone in a postsurgicalpopulation. Crit Care Med 1983; 11(7): 527-31.

5. Arieff A I. Postoperative hyponatraemicencephalopathy following elective surgery in children.Paediatric Anaesth 1998; 8(1): 1-4.

6. DHSSPS. Published information: hyponatraemia wallchart. 2002. Available from URL:http://www.dhsspsni.gov.uk/publications/2002/Hypno%2OWallChart.pdf

7. Jenkins J, Taylor B. Prevention of hyponatraemia.Arch Dis Child 2003. In Press.

C The Ulster Medical Society, 2003.