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530 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

Research vignette
Juve-Udina M-E, Valls-Miro C, Carreno-Granero A, Maria-Estalella G, to critical care nursing there are omissions and discrepancies in
Monterde-Prat D et al. To return or to discard? Randomised trial on both the conduct of the study and the analysis that undermine the
gastric residual volume management. Intensive Critical Care Nursing credibility of the findings.
2009; 25 (5): 258–67.
The value for maintaining GRV within safe limits, i.e. below
Abstract 5 mL/kg was cited by Horn and colleagues in their secondary
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Objectives analysis of intermittent versus continuous feeding in a paediatric
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The study aimed to determine the effect of returning or discarding ICU. Horn and colleagues used the value recommended by
the gastric residual volume (GRV) on gastric emptying delays and Taylor and Baker (the primary reference) in their paper published
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feeding, electrolyte balance and patient outcomes among critically on paediatric enteral nutrition. There was no information on how
ill patients. Gastric emptying delay (GED) was defined as the dif- this value was derived and it may not be appropriate for adults.
ficulty in maintaining GRV within safe limits, i.e. below 5 ml/kg. The GED was categorised into three groups but the rationale for
The GED was categorised as light GED (151–250 mL/6 hours), mod- using these categories was not provided. Other important out-
erate GED (251–350 mL/6 hours) or severe GED (>350 mL/ comes of interest are not well defined. For example testing glucose
6 hours). 353 values in pulmonary secretions is not an acceptable method to
define pulmonary aspiration. The report does not explicitly define
Methods the ‘discard’ group.
The prospective, randomised clinical trial was conducted in a single
medical-surgical intensive care unit (ICU) of a public university hos- In conducting the study, randomisation procedures are explained
pital. Patients admitted to the ICU for longer than 48 hours, aged but it is unclear who controlled allocation of patients to the return
18 or older, who had haemodynamic monitoring and were fed or discard group, thereby opening the study to selection bias if the
enterally or parenterally were recruited to the study over one year. allocation was inconsistent. The study is unblinded as expected but
Participants were excluded if connected to an intermittent gastric mention of why it was not possible to blind should be included in
aspiration system. Computer-generated randomisation was used the report. All patients were accounted for but ‘intention to treat’
to randomise participants to the return (intervention) or discard principles were not used. The type of ICU, but not its location, is
(control) group. The estimated sample size (59 participants in each reported as mixed medical-surgical (general) ICU which are the
group) was informed by sample size calculations. The study most common ICUs in Australia. The selection criteria were listed
finished for a participant if: (1) there was no need for further GRV and recruitment was described as continuous over a year. It is
monitoring, (2) occurrence of adverse event associated with the revealed later in the paper that recruitment did not occur for 2
procedure (pulmonary aspiration or cardio-respiratory arrest months over summer although no reason for not recruiting during
during or immediately after the procedure), (3) faecal aspirates, (4) this period was provided. This may have been an important omis-
major protocol error or (5) death. Gastric residual volumes were sion as acknowledged by the authors.
checked every 6 hours and an algorithm was used to guide man- An algorithm was used to guide management of GRV but it is
agement of GRV. Data were collected by the investigators or by the unclear and two standard volumes were prescribed for enteral
trained registered nurses from the ICU and included the incidence feeds. While feeding was administered continuously the algorithm
of (1) blocked NGT; (2) pulmonary aspiration episodes; (3) intoler- indicates different administration and cessation times which are
ance episodes (nausea, vomiting, diarrhoea and abdominal disten- quite confusing.
sion); (4) enteral feeding delays; (5) hyperkalaemia episodes; (6)
hyperglycaemia episodes and (7) discomfort episodes, identified The data collected on factors that may be potentially affected by
by significant changes in vital signs and also from the Ramsay seda- the return or discard of GRV were impressive. The lack of signifi-
tion score. 354 cance between groups is disappointing but not unexpected. Even
though sample size calculations were performed, the estimates for
Results and Conclusion
No significant differences were found in participant demographics the effect size may not be realistic and subgroup analysis was not
or outcome measures between the groups. The exceptions were decided a priori.
participants in the intervention group had a lower incidence and While the limitations of the study were discussed, important issues
severity of delayed gastric emptying episodes (P = 0.001) and more such as conduct of the study in a single centre, use of subgroup
episodes of hyperglycaemia. The investigators concluded that analyses and not using intention to treat analysis were omitted. A
returning gastric aspirates improved GRV management without major limitation in our opinion was to include patients who
increasing the risk for potential complications. received parenteral nutrition. It would be more informative to
study only those patients receiving enteral feeding in a sufficiently
Critique large sample using a strict standardised feeding regimen to assess
Gastric residual volume (GRV) is routinely measured in many ICUs the effect of administering enteral nutrition and the effect of GED.
to monitor gastric tolerance to enteral feeding and abdominal Patients who receive parenteral nutrition are likely to have impaired
decompression and drainage for patients not fed enterally. This gut function and their inclusion only confuses the results. Perform-
study compared two methods of managing gastric aspirate after it ing some statistical modelling may have enhanced understanding
was removed from the stomach, i.e. return or discard. Gastric aspi- of the outcomes of the study.
rates were returned in the ‘intervention’ group if the GRV was not
greater than 250 mL, if so then the return volume was limited to There is a wide variation in the management of GRV and little avail-
250 mL. Whilst using a robust study design in an area of relevance able evidence to guide practice. The volume of GRV considered
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