Viewpoint Dehydration in acute gastroenteritis by zez16524


									J. Paediatr. Child Health (2002) 38, 219–222


                          Dehydration in acute gastroenteritis
                                                              DR BREWSTER
                     Clinical Dean, NT Clinical School, Flinders University, Darwin, Northern Territory, Australia

ASSESSMENT                                                                  degree of dehydration with ongoing stool losses and could
                                                                            potentially overestimate the degree of dehydration if the child
Three ways of assessing the degree of dehydration in children               were given excessive IV fluids (e.g. developed puffy eyes).
with diarrhoeal disease are clinical assessment, weight gain                Urinary output and specific gravity are helpful to confirm that
with rehydration and laboratory tests. The study by Yilmaz                  a child has been adequately rehydrated and is passing frequent
et al. in this issue attempts to improve the reliability of assess-         dilute urine.
ing dehydration by using laboratory tests.1 This study did not
use clinical assessment on admission, but laboratory tests are
compared to percentage weight change after recovery. How-                   Aboriginal children with dehydration
ever, the latter is an imperfect gold standard in our experience,
and the rehydration period was extended beyond 24 h in this                 In our studies at Royal Darwin Hospital,7 we have compared
study so the degree of dehydration ranged up to 19% [sic]. In               clinical assessment (using the World Health Organization pro-
spite of these limitations, the authors found that urea and                 tocol) with per cent weight change after 24 h rehydration in 324
bicarbonate were useful in assessing the degree of dehydration              acute gastroenteritis admissions of whom 91% were Aboriginal
in acute gastroenteritis.                                                   children. The mean per cent dehydration (95% confidence inter-
                                                                            vals) by clinical assessment on admission for the 268 Abori-
                                                                            ginal children from remote communities was 5.0% (4.6–5.3),
Clinical versus weight change assessment of dehydration                     compared to 3.9% (3.6–4.2) for weight change after 24 h
                                                                            rehydration. Although these two different measures of dehydra-
Clinical assessment of dehydration has low sensitivity because              tion appeared to correlate well (Fig. 1), the kappa agreement
clinical signs only become present with moderate to severe                  was only 0.30 and the Pearson correlation 0.56. On multiple
dehydration (≥5%), and the actual degree of dehydration may                 linear regression, clinical assessment correlated better than
be underestimated with obesity and overestimated with wasting               weight change with bicarbonate (P < 0.001 vs. P = 0.62) or
or sepsis. An American study found the four signs which best                venous blood pH (P = 0.001 vs. P = 0.33) and also with urea
predicted dehydration were a capillary refill time > 2 s, absent            (P = 0.04 vs. P = 0.55), on adjusting for age and the other
tears, dry mucous membranes and ill general appearance.2 A                  measures of dehydration. This model with four degrees of
Melbourne study found that poor capillary return was the most               freedom explained 33.9% of the variability in clinical dehydra-
reliable clinical sign of dehydration.3 Although capillary refill           tion whereas only 22.7% was explained in the comparable
time is a useful sign of dehydration, it can be affected by                 weight change dehydration model.
factors such as fever, ambient temperature and age.4 Other                     Not surprisingly, the degree of clinical dehydration tended to
studies have found laboratory tests to be generally insensitive             reflect how sick the child appeared. A low serum bicarbonate
in assessing hydration, but bicarbonate, urea, creatinine and               on admission was the best predictor of dehydration, correlating
uric acid have tended to be the most helpful tests.5,6 The                  strongly (P < 0.001) with worse clinical dehydration, higher
percentage weight gain with rehydration seems a relatively                  urea, greater diarrhoea severity (as a score) and younger age,
objective measure of dehydration which can be used to verify                but not with weight change assessment of dehydration
the clinical assessment after therapy, but it is obviously no help          (P = 0.48), and these five factors explained 43.2% of the
in assessing the degree of dehydration on presentation. It does             variability in bicarbonate. The same regression model but with
require two accurate measurements, preferably on the same                   venous blood pH on admission replacing bicarbonate had
scale with the child undressed and taken at the same time of day            similar findings. Creatinine was significantly less sensitive than
(24 h apart) as longer periods are affected by weight changes               urea as a measure of dehydration. From our results, we con-
from loss of subcutaneous tissues due to the catabolic state or             clude that weight change after rapid rehydration is not a reliable
from refeeding. The initial weight is subtracted from the                   measure of dehydration, and that plasma bicarbonate (or
rehydration weight and taken as a per cent of the rehydration               venous pH) is a better laboratory indicator of significant
weight. The per cent weight change tends to underestimate the               dehydration than urea.

  Correspondence: Professor DR Brewster, Clinical Dean, Northern Territory Clinical School, Flinders University, PO Box 41326, Casuarina, NT 0811,
Australia. Fax: 61 8 8922 8248; email:
  Accepted for publication 21 February 2002.
220                                                                                                                     DR Brewster

                                                                       The European Society of Pediatric Gastroenterology, Hepa-
                                                                    tology and Nutrition (ESPGHAN) has recently published new
                                                                    guidelines for the management of gastroenteritis,16 which include
                                                                    the following ‘6 pillars of good practice’:
                                                                    1 Use of ORS to correct estimated dehydration in 3–4 h
                                                                    2 Use of hypo-osmolar solutions (ORS as in 1)
                                                                    3 Continuation of breastfeeding
                                                                    4 Commencement of early refeeding after 4 h rehydration
                                                                    5 Prevention of further dehydration by giving additional ORS
                                                                       (10 mL/kg/watery stool)
                                                                    6 No administration of unnecessary medication
                                                                       The duration of diarrhoea can be reduced by 0.43
                                                                    (0.12–0.74) days by early feeding of children with acute
                                                                    gastroenteritis,17 which also has added nutritional benefits.
                                                                    Small frequent feeds (12 per day) also appear to speed up
                                                                    recovery from diarrhoea.18 The best foods to be introduced in
                                                                    the treatment of acute gastroenteritis are complex carbo-
                                                                    hydrates (e.g. rice, wheat, bread, and cereals), yoghurt, fruit and
Fig. 1 Assessment of dehydration: clinical versus weight change     vegetables. The so-called BRAT diet (banana, rice, apple and
(means and 95% confidence intervals).
                                                                    black unsweetened tea) was a progenitor to this approach. Fatty
                                                                    foods or high sugar foods such as sweetened tea, juices or soft
                                                                    drinks should be avoided.9 Soft drinks, juices and similar
                                                                    solutions tend to be too hypertonic and low in electrolytes.

                                                                    Rapid IV rehydration
Oral rehydration
                                                                    An important advance in the treatment of dehydration in acute
Oral rehydration with an appropriate solution is a highly           gastroenteritis has been the change to rapid rehydration over
effective means of rehydration which uses the principle of          4 h. This was introduced as best practice by WHO in the 1980s
glucose-facilitated sodium transport.8–10 The optimal concen-       and has been used by the author in the developing world since
tration of an oral rehydration solution (ORS) is approximately      then, where it proved safe and effective with limited nursing
60mmol/L of sodium, 20 mmol/L of potassium, 110 mmol/L              care (since the only IV flow rates without pumps tend to be
(2.5%) of glucose and an osmolality of about 220.11,12 This         wide open and blocked). Rapid rehydration has only been
hypo-osmolar ORS has also been used safely in malnourished          accepted in developed countries in more recent years.8,9,16,19
children without developing hyponatraemia.13 Cereal-based           Rapid intravenous rehydration with Ringer’s lactate (Hart-
oral rehydration solutions (e.g. rice) have not been shown to       mann’s solution) is now best practice for moderate to severe
have a definite benefit in non-cholera diarrhoea compared to        dehydration or when oral rehydration is inappropriate or fails.
glucose-based oral rehydration solution,12 but there is anecdotal   The only contraindications to a trial of oral rehydration therapy
evidence that it may be more palatable.                             are shock, coma, ileus and severe hypokalaemia. Rapid re-
   Many studies in industrialized countries have shown that         hydration aims to correct the child’s deficit over 4 h. Thus, a
oral rehydration is under-utilized in children with diarrhoea,      10-kg child who is 10% dehydrated would receive one litre of
with excessive reliance on IV fluids in well hydrated chil-         Ringer’s lactate over 4 h.
dren.14,15 The most likely reason for a child refusing to drink        Hypernatraemic dehydration is a relative contraindication to
ORS because of the taste is that he/she is not dehydrated as        rapid rehydration, although a bolus of Ringer’s lactate or
dehydrated children will not refuse to drink ORS because of         normal saline is unlikely to drop the serum sodium fast enough
taste. Oral rehydration may be time consuming for caregivers,       to induce seizures. Rapid rehydration is highly successful in
particularly with vomiting. Vomiting can be managed with            children with failure to thrive or moderate malnutrition, so it
small, frequent amounts of oral rehydration solution (e.g. 5 mL     is only in severe malnutrition (marasmus or especially kwash-
every 2 min),8 but this requires a compliant and motivated          iorkor) that there is a risk of heart failure.20 Intraosseus
caretaker. Paediatric wards in developing countries often           infusions can be life-saving in an emergency, but are not
supply a large central container of ORS so that mothers can         without risks (e.g. osteomyelitis).21
serve themselves with a ladle and rehydrate their children using       There is no evidence of a short-term benefit from the
a cup and spoon. Vomiting is often an early symptom of gastro-      addition of bicarbonate to rehydration solutions,22–24 but this
enteritis before there is dehydration, so a short history of        may not be true in Top End Aboriginal children who have
vomiting and refusal to drink ORS because of taste are not          extremely high rates of acidosis with acute gastroenteritis. Note
good indications for IV therapy. Some clinicians promote the        that oral rehydration solutions have 10 mmol/L of citrate, and
use of nasogastric tubes for rehydration, but these are unpleas-    Ringer’s lactate contains 40 mmol/L of lactate as base. A relative
antly invasive, and if admission investigations require a vene-     contraindication to the use of Ringer’s lactate is alkalosis (e.g.
section, why not use this IV route if invasive rehydration is       pyloric stenosis) when normal saline is more appropriate for
required? Reducing unnecessary IV rehydration by resorting to       rehydration.
nasogastric tubes seems pointless, unless there are difficulties       No study has compared Ringer’s lactate to normal saline for
with IV access.                                                     rehydration, but most paediatric recommendations prefer Ringer’s
Dehydration in acute gastroenteritis                                                                                                    221

lactate, although the Advanced Paediatric Life Support and           CONCLUSION
ICU guidelines tend to favour normal saline,25 and ESPGHAN
favours 20 mL/kg of 0.8% saline for shock followed by 0.45%          The accurate assessment of dehydration in childhood diarrhoeal
saline in 5% dextrose.16 There is a potential danger of rapid IV     disease remains a difficult challenge for clinicians. Experience
rehydration if maintenance solutions (Na+ 30–60 mmol/L) are          in the developing world and with Top End Aboriginal children
used instead of rehydration solutions (Na+ 130–155 mmol/L),          suggests that clinical assessment supplemented by plasma
particularly in a severely dehydrated child in whom severe           bicarbonate or venous blood gases are the most useful tools and
hyponatraemia with seizures and death could be induced. Many         that weight gain with rehydration is not a ‘gold standard’.
clinicians treating dehydration are aware of the recent change       Rapid IV rehydration with Ringer’s lactate over 4 h is safe and
to rapid rehydration protocols but are not aware of the need to      effective, but maintenance solutions must not be used for rapid
use Ringer’s lactate nor the danger of using maintenance             IV rehydration. For moderate to severe dehydration, the combi-
solutions for rapid rehydration. One cannot help wondering           nation of rapid IV rehydration and early feeding has reduced
whether some unexpected deaths in gastroenteritis might have         our use of ORS in Aboriginal children. But hypo-osmolar ORS
been related to this misunderstanding.                               remains the key therapy for the prevention and treatment of
   There is a continuing controversy about the use of colloid        milder degrees of dehydration in acute gastroenteritis.
(e.g. albumin) versus crystalloid (e.g. Ringer’s lactate) solu-
tions for volume replacement in critically ill patients. A system-
atic review26,27 did not support the use of colloids for volume
replacement and this issue is now the subject of an Australian       REFERENCES
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222                                                                                                                                DR Brewster

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