19th July – Does Bedside US Measurement of the IVC Diameter Correlate with CVP in the Assessment of Intravascular Volume in Children?

190713 Paper

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23426248

What is this paper about (what is the research question)?

Can we use bedside ultrasound measurement of IVC diameter as a proxy for fluid status (as determined by CVP measurement) in children?

Summary of the Paper

Design: prospective observational study

Objective: to compare bedside US assessment of volume status with CVP measurement in critically ill paediatric patients

Outcomes: correlation of US assessment of volume depletion with CVP assessment

Test of interest: beside US measurement of IVC diameter and calculation of IVC/aorta ratio, defining dehydration as “collapsability index of 50% or greater and an IVC/Ao ratio of 0.8 or less.” Diameter measured in subxiphoid sagittal and subxiphoid transverse views.

Reference Standard: invasive CVP measurement by digital transduction at distal port of previously sited CVC

Participants: convenience sample of patients aged <21y admitted to the Paediatric Critical Care Unit (Intensive Care) at a single centre between July 2010 and June 2011

  • Inclusions: patients requiring invasive haemodynamic monitoring
  • Exclusions: patients in whom US measurement of IVC could not be performed due to technical limitations

Results: 

72 eligible patients of whom 51 enrolled to the study. Sagittal view was obtained in 100%, transverse view in 84% of subjects.

Correlation of collapsibility index and CVP: -0.23 (P=0.11)

Correlation of IVC/Ao ratio and CVP: -0.19 (P=0.22)

Authors’  conclusions

We did not find a correlation between the 1-point measurement of either the collapsibility index or the IVC/Ao ratio and CVP measurements in critically ill paediatric patients.

On the study design

This paper is an interesting one; the use of ultrasound to determine the need for and response to fluid resuscitation is controversial in adult patients, so it is not surprising to see that the uncertainty about clinical usefulness translates to paediatric practice. In addition, assessment of hydration/dehydration in children is notoriously difficult and the search for objective measures which reflect clinical endpoints is clearly relevant.

This paper is an observational study which means that there was no change made to the patient’s care in response to the measured data. The population may or may not reflect our ED patients; by definition, patients already admitted to PICU (at least in the UK) have usually a) been unwell for some time and b) had some level of resuscitation – so it is difficult to know how their volume status might be affected by preceding use of fluid boluses (particularly if hypertonic solutions were used). That said, the vast majority of critically ill paediatric patients in the ED do not have central access amenable to CVP monitoring and there are obvious issues with designing a study which necessitates insertion of CVCs which might not be necessary (unethical) or are going to be inserted in the ED (impractical – numbers likely to be very small). The fact that the recruitment was a convenience sample also reflects the otherwise small numbers and unpredictable nature of critical illness in children and while a more robust sampling method would be preferable, convenience sampling is often seen in studies where a single investigator has a particular skill set necessary for the collection of study data.

A bigger problem is the use of CVP as a marker of haemodynamic status; although it is frequently measured in the ICU and PICU, it is notoriously poor at reflecting volume status as a single measure and demonstrating clinically relevant response to fluid bolus when measured continuously, as raised in this review paper from 2008. So the study is comparing a questionable method of determining fluid status with one which is equally questionable – not exactly a great starting point. Perhaps a longer term outcome – such as fluid balance over the subsequent 24-48h, urine output, need for fluid boluses – might have given a clearer and more reliable picture.

There was also little consistency between the patients; CVC measurement occurred at a variety of anatomical sites and there was no correction or account taken for other variables which might affect CVC readings (such as abdominal surgery or positive pressure ventilation).

What were the results and what does this mean?

This is a great opportunity to revise correlation!

There’s a great wikipedia article on Spearman’s rank correlation coefficient here, but essentially correlation measures the level of interdependence between two non-parametric variables. It tells us whether as one variable increases, the other increases, and the strength of this relationship.

In the paper, both correlation co-efficients quoted in the results section were negative, suggesting that as CVP increases the IVC variable (IVC/Ao ratio or collapsibility index) decreases, and vice versa. The small numbers (-0.11 and -0.23) imply a near random relationship (remember, the nearer the correlation coefficient is to zero the less related the two variables appear to be; the nearer to 1 or -1, the stronger the relationship and the more predictive one variable is of the other). The performance characteristics (sensitivity, specificity, NPV and PPV) for both US-calculated variables were poor.

However, there are very small numbers here; of the 52 children included, only 21 actually had a CVP <8mmHg (the cutoff used by the authors to determine intravascular volume depletion). In any study where such a small number of patient have the target condition we have to wonder whether different patterns might be seen in a larger sample – the probability of a type II error is high.

What can we take from this paper into clinical practice?

So, assessment of paediatric intravascular volume status remains a mystery for now. Previously published studies have suggested that IVC/Ao ratio is lower in children who are otherwise clinically assessed as being dehydrated and that the value rises following fluid boluses, but we cannot be sure from this current paper that US measurement reflects CVP. Should we use ultrasound to assess intravascular status? This paper finds it a poor proxy for CVP – which again is a poor proxy for volume status. So on the basis of this study – no, but there is clearly more work to be done here.

More questions to ask

  • Do serial IVC measurements reflect response to fluid bolus in a clinically meaningful way?
  • Would we see better correlation using a single CVC line site, or excluding “less central” central lines such as femoral CVC?
  • Should we be aggressively fluid-resuscitating children anyway?! – see this interesting FOAM paper on new insights from the FEAST trial

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5th July 2013: Comparison of cosmetic outcomes of absorbable versus nonabsorbable sutures in pediatric facial lacerations

5th July 2013

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23714755

What is this paper about (what is the research question)?

Do non-absorbable and absorbable sutures give comparable cosmetic results for repair of simple facial wounds in kids?

Summary of the Paper

Design: multicentre, randomised controlled, single blinded trial with allocation concealment

Objective: to compare long-term cosmetic outcomes of absorbable versus non-absorbable sutures based on physician scoring of facial lacerations in the paediatric population

Outcomes: primary – visual analogue scale assessment of wound acceptability made by physicians, blinded to suture material, at 3 months. Secondary – caregiver completion of same visual analogue scale plus completion of satisfaction questionnaire

Intervention: closure of wound by standard approach using 5.0 fast-absorbing surgical gut (FAC) without removal of sutures

Reference Standard: closure of wound by standard approach using 5.0 non-absorbable suture (NYL) with removal of sutures at 4-7 days

Participants: patients presenting to two urban paediatric EDs in Philadelphia April 2008-April 2010

Inclusion – English speaking patients aged 1-18 years with isolated, non-contaminated linear facial wounds between 1-5cm in length assessed by clinicians as requiring closure by suture

Exclusion – irregular or contaminated wounds/bites, wounds>8h old, patients with complex wounds, immunodeficiency, bleeding/clotting disorder, pregnancy, diabetes, renal dysfunction, or allergy to local anaesthetic

Results: 98 patients were recruited of whom 49 had closure with FAC and 49 with NYL. 85 were followed-up at 4-7 days (42 FAC,43 NYL) and 76 at 3months in person or by telephone (FAC 37, NYL 39). Telephone follow up did not include VAS score.

61 patients had completed VAS scores at 3/12 (FAC 29, NYL 32)

Mean VAS scores by physicians:

FAC 57.6, NYL 67.6

Difference in means -10 (95% CI for difference in means -19.6 to -0.4) 

Authors’  conclusions

We are not yet able to conclude that absorbable sutures are equivalent to nonabsorbable sutures with respect to cosmetic outcomes of facial lacerations in children.

On the study design

There is little information on how patients were recruited, but other than the restriction of English-speaking patients inclusion and exclusion criteria seem sensible.

The allocation concealment and blinding is helpful in reducing bias, but I would question whether leaving absorbable sutures until completely absorbed is standard practice – it isn’t mine, and therefore this impacts the external validity of the study.

The plan for follow-up at 3/12 seems sensible and is rationalised by the authors but this seems early to fully assess the “long-term” impact of wound closure.

While the exact suture material does not necessarily replicate standard UK practice it is reasonable to assume little difference between non-absorbable and absorbable suture material around the globe.

What were the results and what does this mean?

The trial is a non-inferiority trial – the aim is to show that using absorbable suture material does not give a perceptibly inferior cosmetic result. The visual analogue scoring undertaken by blinded physicians (and averaged between three scorers) showed not only lower VAS satisfaction scores for the absorbable suture group but a 95% confidence interval which did not cross zero, suggesting the study was unable to demonstrate non-inferiority. The validity of the VAS has been assessed elsewhere but there is a considerable difference between physician and caregiver scores.

It is also important to remember that despite sample size calculations which predicted attrition of 40%, only 61/98 recruited patients actually completed the full study protocol and had photographs for assessment by VAS – so the study was insufficiently powered.

What can we take from this paper into clinical practice?

It appears that if we use absorbable sutures and don’t remove them, there are noticable differences in wound healing at 3/12; there’s insufficient evidence in this paper to convince us that not removing sutures provides a comparable cosmetic result in the first three months.

More questions to ask

  • Are there benefits to using absorbable sutures and then removing them (in the same timeframe as we would normally remove non-absorbable sutures)?
  • Would we see non-inferiority at a later review – 18 months after closure perhaps?
  • Would we see non-inferiority in an appropriately powered study?

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12th April 2013: Electrolyte Profile of Paediatric Patients with Hypertrophic Pyloric Stenosis

120413 title

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23528507

What is this paper about (what is the research question)?

In paediatric patients with hypertrophic pyloric stenosis (HPS), what is the prevalence of abnormal laboratory results?  Are these results related to the duration of illness (by duration of vomiting), and is there any time trend in these results?

Summary of the Paper

Design: Retrospective chart review

Objective: To investigate the incidence and prevalence of abnormal laboratory results in patients with a radiological and operative diagnosis of HPS

Outcomes:

Primary – prevalence of high, low and normal CO2, K and Cl in HPS cases

Secondary – trend in prevalence of metabolic alkalosis and acidosis in HPS cases over the study period

Tertiary – association between days of vomiting and abnormal CO2, K and Cl

Reference Standard: Normal range laboratory results for the facility

Participants: Patients younger than 6 months, with HPS confirmed on ultrasound or Upper GI series, who underwent pyloromyotomy at a tertiary regional paediatric centre from 2000-2009.

Results:

205 patients were included in the study.  Their age varied from 1.4 to 13.9 weeks (SD 2.2), with a weight range of 2.1 to 4.9kg (SD 0.5).  88.3% were male.  74.3% were of non-Hispanic ethnicity.  80.5% white race, 1.5% African-American, 1.5% Asian and 16.5% other.

The proportion of HPS cases with normal serum CO2 was 62%, low 20%, and high CO2 18%.  Potassium was normal in 57%, low in 8% and high in 35% of cases.  Chloride was normal in 69%, low in 25% and high in 6% of cases.

Logistic regression analysis of the proportion of normal, low and high CO2 over the study period showed an increased in the prevalence of metabolic alkalosis (p=0.009) and a decreased in metabolic acidosis (p=0.002).

Advancing age was associated with presence of metabolic alkalosis on presentation with HPS (data not provided).

There was no correlation between the number of days of vomiting and abnormalities in electrolytes in this study population.

Authors’  conclusions

We observed that normal laboratory values are the most common finding in HPS and that metabolic alkalosis was found more commonly in the latter part of the decade and in older infants.

On the study design

This was a retrospective chart review for a 10 year period from 2000-2009.  Data from 2000-2002 was combined to increase power because the case numbers in single years were “small and unstable.”  It’s not clear what they mean by “unstable” as the raw data is not provided.

The authors do not comment on the total number of presentations over the study period, so it’s unclear if any cases were excluded, and reasons for any such exclusions.

There is demographic data missing with respect to birth weight (138/205), days of vomiting (196/205), heart rate at presentation (203/205) and weight at presentation (204/205).  The latter categories are unlikely to have been affected by this, and it is unclear whether additional data on duration of vomiting would have changed the analysis.

Prospective studies have the advantage of more complete data sets, and potential for further variables to be included, however can introduce observation/measurement bias.

What were the results and what does this mean?

Normal laboratory values are the most common finding in HPS and therefore  serum electrolytes are a poor marker for the presence or absence of HPS.

CO2 normal 62% low 20% high 18%

K normal 57% low 8% high 35%

Cl normal 69%  low 25%  high 6%

The incidence of metabolic alkalosis increased over the study period, and its prevalence is higher in older infants. 

They have no explanation for the increase in metabolic alkalosis over the decade of the study.

The authors postulate that the latter finding may demonstrate that advanced age at diagnosis serves as a marker for the duration and severity of stenosis.

What can we take from this paper into clinical practice?

This paper agrees with previous studies that the “typical metabolic picture” of hypochloraemic hypokalaemic metabolic alkalosis in paediatric HPS is no longer seen in the majority of presentations.

For us this means that we cannot rely on laboratory results as a marker for hypertrophic pyloric stenosis in infants.  We must continue to have a high index of suspicion for this condition in infants presenting with persistent vomiting and proceed to ultrasound for diagnosis.

Although laboratory results don’t help us decide which children need ultrasound, it is important to look for metabolic derangements and correct them as indicated.

What this study adds is that contrary to previous beliefs, there is no relationship between the duration of illness, and particularly vomiting, on the severity of metabolic derangements in these children.  This seems counter-intuitive, and perhaps the more important factor is not the duration of vomiting, but whether the infants are able to keep down an adequate amount of fluids – i.e. The severity of dehydration.

Unfortunately there was insufficient data in the patient charts to enable analysis of trends between dehydration, vomiting and abnormal laboratory results.  Only 43/205 (21%) charts mentioned hydration status, however 42% of the patients whose charts noted dehydration (36/205) had metabolic alkalosis at presentation, compared to 44% with normal CO2.

More questions to ask

  • Were there a higher proportion of males in this group than other populations?
  • Why was delayed presentation (60days vomiting in one case) not associated with more severe illness??
  • An insufficient number of charts contained information about hydration status – is this more relevant for laboratory abnormalities than days of vomiting?

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5th April 2013: Prospective Pilot Derivation of a Decision Tool for Children at Low Risk for Testicular Torsion

050413

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23517259

What is this paper about (what is the research question)?

Is it possible to exclude a diagnosis of testicular torsion on the basis of history and examination alone?

Summary of the Paper

Design: prospective cohort study for derivation of a clinical decision rule

Objective: to derive a pilot clinical decision tool with 100% NPV for testicular torsion

Outcome: Proposed low-risk decision tree determined by recursive partitioning based on historical and examination variables recorded prior to ultrasonographic or specialist assessment

Reference Standard: presence of testicular torsion defined by: diminished blood flow on testicular doppler US (read by paediatric radiologist), or ischaemic/infarcted testicle at operative assessment (by paediatric surgeon or urologist), or presence of testicular atrophy at 1- to 3-month follow-up (contralateral difference in testicular size as measured by orchidometer)

Participants: Convenience sample of male patients aged 0-21 years with acute (<72h) testicular pain presenting to a tertiary children’s ED between July 2005-February 2008

Results: 228 patients (of 552 eligible patients) were enrolled. 55 (10% of eligible patients) were diagnosed with testicular torsion, of whom 21 (9.2%) were among those recruited into the study.

Odds ratios:

  • Horizontal/inguinal testicular lie OR=18.17 (95%CI 6.2-53.2)
  • Unilaterally or bilaterally absent cremasteric reflect OR=11.01 (95%CI 3.14-38.64)
  • Nausea or vomiting OR=5.63 (95%CI 2.08-15.22)
  • Age 11-21 years OR=3.9 (95%CI 1.27-11.97)
  • Scrotal oedema OR=3.42 (95%CI 1.21-9.69)

Authors’ Conclusions:

Patients with normal testicular lie, without nausea or vomiting, and between the ages of 0-10 years are at low risk for having testicular torsion despite the presence of acute testicular pain. Thus, patients who do not meet all three of these criteria should be considered at risk for possible testicular torsion and should undergo subsequent emergent evaluation.

On the study design

The inclusion and exclusion criteria seem sensible too; patients were included in the age 0-21 group with testicular pain of <72h duration, and subsequently excluded if they had prior ipsilateral inguinal or  urological surgery, definite hydrocoele or inguinal hernia or known diagnosis at initial evaluation. The authors have tried to maximise their awareness of the patient population by using database searches during the study period to identify “missed” participants.

Unfortunately the convenience sample meant that more than half of patients presenting during the study period who were diagnosed with testicular torsion were not included in the data collection. This means the study was underpowered for the question it intended to ask. Convenience sampling is often significantly cheaper and easier than a 24-hr recruiting presence in the ED but as this paper demonstrates it can have a profound effect on the numbers recruited, particularly in conditions which are relatively rare.

Various measures have been utilised to minimise the effect of bias; standardised data collection forms are always helpful in this regard. The initial ED assessments were made prior to ultrasound or speciality assessment which acts as a blind assessment, although surgeons and radiologists determining the outcome were not blinded. The authors argue that clinical information is essential in patient care, but many studies use blinded radiological assessment after the event and this could certainly have been undertaken in this case even if the surgeons could not be blinded.

In the UK, it is likely that testicular tissue would be sent for histological diagnosis; arguably, this is a more definitive outcome and could certainly be blinded.

The decision to follow-up at 1- 3 months with orchidometer measurements when baseline measurements were not taken is an odd one; surely this invites all manner of confounders? Thankfully this did not actually involve any subjects but it seems a strange choice – perhaps an afterthought?

What were the results and what does this mean?

Odds ratios for the various examination and historical findings were given in table 2. These variables were formulated into a decision rule using recursive partitioning.

050413 Table 2

The most strongly predictive finding was abnormal testicular lie, with an odds ratio of 18.17 but a very wide confidence interval (95%CI 6.2-53.2) reflecting the small study numbers.

The decision rule in itself had the following test characteristics:

  • NPV 100% (95%CI 98-100%)
  • Sensitivity 100% (95%CI 98-100%)
  • Specificity 44% (95%CI 38-50%)
  • PPV 15% (95%CI 11-21%)

Obviously an NPV of 100% and sensitivity of 100% is impressive and important in a rule-out tool such as this, but the specificity and positive predictive value are very low. This would ordinarily expose a large number of patients to further examination and assessment, but as these patients have not yet had doppler examination it may not be unworkable.

However, this rather raises the question – if I saw a 7-year-old patient with testicular pain and vomiting, would I really need this decision rule to tell me that he needed further assessment to exclude testicular torsion?

What can we take from this paper into clinical practice?

I don’t think that at this stage we can rely fully on the absence of abnormal lie, nausea/vomiting and age <10 years to exclude testicular torsion as a diagnosis in patients with acute testicular pain in the ED, but it will be interesting to see how the proposed decision tool performs in external validation.

However, taking a step back, we are able to see that what this paper is  trying to do is formalise the process of diagnostic suspicion of testicular torsion. We have little information about the skill and experience levels of the ED physicians performing the initial assessment. Does this paper tell us anything we don’t already know as clinicians?

Well, maybe yes – it looks as though we can be a little reassured by the group of patients aged <10 without abnormal lie or nausea/vomiting. The use of sensitivity analysis adds to this – the authors have included  patients lost to follow-up and assumed that they had torsion, finding that the decision rule performed just as well.

However, we really need to see how the rule performs in a fresh setting when applied to all patients rather than a convenience sample.

More questions to ask

  • How would this rule perform in a different setting – an external ED or even in general practice?
  • Does this decision process reduce our referrals for expert assessment/doppler US or does the low specificity/PPV represent a potential increase in referral, time and cost?

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22nd February 2013: Identifying Children at Low Risk of Blunt Abdominal Injury

22 feb 13

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23375510

What is this paper about (what is the research question)?

In children with blunt torso trauma, which clinical features predict low risk of associated intra-abdominal trauma requiring intervention (IAI) and potentially obviate need for abdominal computerised tomography (CT)?

Summary of the Paper

Design: Multi-centre prospective observational chart study

Objective:  To derive a clinical prediction rule to identify children with blunt torso who are at a very low risk for intra-abdominal injury requiring acute intervention.

Outcome: Radiographically or surgically apparent intra-abdominal injury necessitating acute intervention.

Population:  Children with blunt torso (thorax and abdomen) trauma evaluated in the emergency department of one of the 20 participating centres from May 2007 – January 2011

Inclusion:

  • Decreased level of consciousness in association with blunt torso trauma (but not isolated head injury)
  • Blunt traumatic event with paralysis and/or multiple non-adjacent long bone fractures
  • Blunt torso trauma due to: Motor vehicle crash: high speed (>40mph), ejection or rollover, Automobile versus pedestrian/ bicycle: automobile moderate to high speed (>5mph), Falls >20ft, Crush injury to torso, Physical assault involving the abdomen
  • Physician concern for abdominal trauma resulting in any of the following diagnostic or screening tests: Abdominal CT or ultrasound (FAST), Laboratory testing to screen for intra-abdominal injury, Chest or pelvic radiography

Exclusion:

  • Injury occurring >24hrs before presentation
  • Penetrating trauma
  • Pre-existing neurologic disorders impeding reliable examination
  • Known pregnancy
  • Transfer from another hospital with prior abdominal CT or diagnostic peritoneal lavage

Results:

12044 children were enrolled (81% of those eligible) with a median age of 11.1 years. 5514 patients underwent abdominal CT scan. 761 patients were identified with intra-abdominal injuries of which 203 underwent acute intervention.  The derived prediction rule identified 7 variables with good interrater reliability.

Combining the variables in a prediction rule gave the following test characteristics for the primary outcome

Prediction rule sensitivity:            97.0%    (95% CI 93.7-98.9)

Prediction rule specificity:            42.5%    (95% CI 41.6-43.4)

Negative predictive value:           99.9%    (95% CI 99.7-1.0)

Positive predictive value:             2.8%      (95% CI 2.4-3.2)

Negative Likelihood ratio:            0.07        (95% CI 0.03-0.15)

23% of all the CTs performed represented patients in the very low risk category and with use of the clinical decision tree would therefore have been potentially avoidable.

Authors’ Conclusions:

A prediction rule consisting of 7 patient history and physical examination findings, and without laboratory or ultrasonographic information, identifies children with blunt torso trauma who are at very low risk for intra-abdominal injury undergoing acute intervention. These findings require external validation before implementation.

On the study design

The study techniques all adhered to accepted best practice for the derivation of a prediction rule.  The authors selected variables for potential inclusion into the decision making rule based on previous literature and biological/physiological plausibility.

The group used variables based on history and examination which would be immediately accessible to all ensuring generalisability across departments and excluding FAST scan and laboratory investigations which may not be universally available.

Standardised data collection of patient history and examination findings were collected prior to CT scanning and then CTs performed at the discretion of the treating physicians according to local protocols.

15 initial variables were proposed, all with at least moderate interrater agreement and then binary recursive partitioning was used to develop a clinical decision rule consisting of seven of these.

The agreed outcome of intra-abdominal injury requiring intervention was then identified by immediate follow-up and then later telephone contact/ mail contact and review of hospital and morgue data to account for cases which may have been initially missed and they achieved impressive follow-up rates.

They were also rigorous in comparing those eligible but not enrolled with those enrolled and no enrollment bias was identified.

What were the results and what does this mean?

Whilst the recruitment into the study was good with large initial numbers (12044 patients) the final outcome of those with intra-abdominal injury requiring acute intervention (203 patients) resulted in inevitability small numbers and it is from this group that the decision rule has been derived essentially.

The final decision rule shows high sensitivity but low specificity in keeping with the intended use as a “rule-out” tool.

22 feb 13 fig523% of all the CTs performed represented patients in the very low risk category and with use of the clinical decision tree would therefore have been potentially avoidable. 

22 feb 13 fig4

There were 6 children however, who were not identified by the clinical prediction rule but required acute intervention for their intra-abdominal injuries. The authors suggest that these children all had clinical features such as haematuria or alcohol intoxication which are likely to have been recognised as an additional risk factor by the treating physician and therefore more caution was used in applying the decision making tool. This fits with the decision rule identifying patients with “low risk”

What can we take from this paper into clinical practice?

Reconfiguration of trauma services within the UK gives opportunities for improved pathways of care; optimizing management whilst minimizing unnecessary investigations and interventions particularly in light of the longstanding concerns about radiation risk from CT scanning in the paediatric population.

Research such as this is therefore highly relevant and yet often difficult to achieve due to relatively the low numbers of paediatric trauma cases so this large study has the potential to make a significant contribution to our future practice.

Caution must be taken though in assuming the impact would be comparable within our population groups and healthcare systems in the UK, where it is possible that there is a different baseline threshold for investigation.

This study also included young people up to the age of 18 which is not true of most paediatric units in the UK and may represent a subgroup with different mechanisms of injury and trauma patterns.

At present this is a derivation study and prior to implementation requires validation in an external setting, allowing for assessment of performance accuracy and refinement.

As the authors correctly identify there is potential risk that the tool may be over-utilised as a “rule-in” decision maker and therefore mean more CTs are undertaken rather than less. In the study population this could have meant a 33% increase in scans

There is likely to be added value from using this tool in assessing risk but not in isolation –  rather in combination with investigations as appropriate and most importantly clinical acumen.

More questions to ask

  • How can the use of FAST scans and laboratory results be incorporated into the use of this tool?
  • Will the surgical teams involved in these cases be happy to reduce the imaging or will it defer imaging to the inpatient rather than ED setting?
  • What is the most important outcome?  Is it identifying those injuries which require intervention, or knowing about all injuries?

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8th February 2013: Impact of Duration of CPR on Survival and Neurological Outcomes in Paediatric Cardiac Arrest

080213

Where can I find this paper?

http://www.ncbi.nlm.nih.gov/pubmed/23339874

What is this paper about (what is the research question)?

Does a longer duration of CPR in paediatric cardiac arrest have prognostic bearing on the likelihood of a positive ultimate outcome (i.e. survival to discharge with intact neurological function)?

Summary of the Paper

Design: analysis of data from prospective multicentre registry (cohort study)

Objective: to use the GWTG-R data to evaluate the relationship between CPR duration and intact survival to hospital discharge after paediatric in-hospital cardiac arrest according to illness category

Primary Outcome: survival to hospital discharge. Secondary outcomes included survival with favourable neurological outcome.

Population: patients <18 years of age suffering pulseless cardiac arrest in-hospital at one of 28 US and Canadian institutions between 1st Jan 2000 and 31st Dec 2009.

  • Inclusion: At least one minute chest compressions provided
  • Exclusion: Events beginning outside hospital or in NNU, delivery room or nursery, illness categories newborn, obstetric or other illness

Results: 3419 paediatric in-hospital cardiac arrests fulfilled the criteria.

Median (IQR) CPR duration was 10 minutes (4-25) for survivors and 25 minutes (12-45) for non-survivors. Survival to discharge was 27.9%; 19.0% of all cardiac arrest patients had a favourable outcome, representing 68.2% of the survivors of the initial insult.

Survival rate and favourable neurological outcome fell linearly in the first 15 minutes; neurological outcome decreased by 1.2% for each additional minute of chest compressions.

Authors’ Conclusions:

CPR duration was inversely associated with survival
to hospital discharge and neurological outcome, even after
adjustment for confounding factors. Surgical cardiac patients had
improved outcomes compared with patients in all other illness
categories. Importantly, this study suggests that a proportion of
children who would presumably die without CPR survive with a
favorable neurological outcome even after prolonged CPR.

Why was the study necessary?

This article was brought to my attention via twitter with the headline “among survivors favourable neurological outcome occurred in 60% undergoing CPR > 35 minutes”. On checking this was indeed word perfect from the abstract. This took me aback as this was not quite my experience, even with the non-survivor group excluded. A paper definitely worth a closer look then!

The article starts with the pretext of the (relatively) low cardiac arrest rate (0.7-3%) in children admitted to hospital with a note that, although still low, survival rates have improved in the last decade. The authors acknowledge a paediatric mantra that CPR beyond 20 minutes or 2 rounds of adrenaline is generally futile although it is interesting the evidence for this has never been robustly demonstrated. A large prospective cohort study then seems a very reasonable undertaking. The American Heart Associations “Get with the Guidelines-Resucitation” [AHA GWTG-R ]initiative providing a national registry for the relationship between in-hospital CPR duration and intact survival to be explored.

On the study design

The AHA-GWTG-R is a prospective registry with data from 328 US and Canadian hospitals between 2000 and 2009. In order to categorise patients pre arrest the following categories were used with those with DNAR orders excluded:

  • Medical Illness (non-cardiovascular)
  • Medical Illness (cardiovascular)
  • Surgical Illness (non-cardiovascular)
  • Surgical Illness (cardiovascular)
  • Trauma

Patients must have had > 1min of CPR provided and it is worth noting that as well as inpatients those in outpatient clinics were included. Those in whom the event started out of the hospital were excluded. Anyone receiving >180 mins of CPR were defined as having 180mins maximum. The primary outcome measure was survival to hospital discharge and secondary measures included return of spontaneous circulation > 20 mins, 24 hour survival and discharge with favourable neurological outcome – this was defined as a Paediatric Cerebral Performance Category of 1, 2 or 3 on discharge. The PCPC is shown in table one.

080213Table1

The authors are open about the fact that as a multi-centre study classifications between hospitals may differ. They are even frank enough to state that as the users of the AHA-GWTG-R pay a fee to do so they may be more interested in outcomes that other hospitals (the AHA-GWTG-R is used by 10% of hospitals).

It could be argued that included ED patients with in hospital arrests are very different from patients who arrest on the wards but the differences between these two groups were not broken down. This would have been very useful information for the emergency care community.

What were the results and what does this mean?

The data collected included 5922 which were all accounted for in an Utstien diagram (figure 1).

080213Fig1

Key demographic details in the study were that the mean age was 4.9+/- 6 years, 8% of events were not witnessed but nearly all (90.5%) were monitored. The majority of patients were General Medical (43.2%). The median CPR duration was 10 minutes for survivors and 25 minutes for non-survivors. Survival to discharge was 27.9%, but only 19.0% of all cardiac arrest patients had a favourable outcome as per the PCPC. Both survival rate and favourable neurological outcome fell linearly in the first 15 minutes, with neurological outcome decreasing by 1.2% for each additional minute of chest compressions. However although only 19% had a favourable neurological outcome this represented 68.2% of the survivors of the initial insult.

080213Fig3B

The headline figure of 60.1% comes from the 95 out of 158 survivors who received CPR for 35 minutes and had a favourable outcome. Surgical cardiac patients had the highest adjusted probability of neurological outcome with medical, general surgical and general medical similar to the whole cohort. Traumatic arrest has the poorest outcome of 4.3%

The study confirms that generally the outcome after arrest is poor however it demonstrated there is variation in the outcome dependant on the type of patient. Interestingly there was an indication that continuing CPR for more than 20 minutes may be justified given the proportion of those who survived with a positive neurological outcome, using the PCPC classification system. It is important to note that overall surviving numbers were low and there was not a priori attempt to predict in which patient group prolonged CPR may be beneficial. 

The biggest challenge with this study is the use of the PCPC and the classification of 3 as a favourable outcome. Classification 3 is a moderate disability but is quite different from 4 (severe; dependant on others for daily support). The distinction is not always clear cut and an excess of grade 3 due to the strict classification may bias the results especially as this was done on discharge when a more favourable grade may be applied.

Finally although the break down into 0-15, 15-35 and >35 seems reasonable there were patients receiving up to and above of 180 minutes of resuscitation. It would be useful to distinguish resuscitation rates into standard, prolonged, very prolonged and unique for the purposes of evaluation as the patient groups, and potentially teams working on them are likely to be very different.

What can we take from this paper into clinical practice?

This study is the largest of its kind and is an extremely useful platform on which to base further research. It will be important the neurological outcome is clearly defined and followed up for a reasonable period of time. The distinction between medical groups needs to be taken into account and for the emergency care community it is validation of the extremely poor survival and outcome of traumatic cardiac arrest. Until further work is performed it will be difficult to extend the ’20 minute rule’ but it is vital this work is performed. To be working in an area as ethically challenging as resuscitation needs a clear evidence base and work both in and out of hospital.

More questions to ask

  •  Do rates differ between ward patients and those suffering cardiorespiratory arrest within the Emergency Department?
  • How would results change if we defined “favourable neurological outcome” more clearly?

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