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Cochrane Database of Systematic Reviews Protocol - Intervention

Use of platelet transfusions prior to lumbar punctures or epidural anaesthesia for the prevention of complications in people with thrombocytopenia

Authors' declarations of interest

Version published: 02 December 2015 Version history

https://doi.org/10.1002/14651858.CD011980

This is not the most recent version

view the current version 30 April 2018
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Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effects of different platelet transfusion thresholds prior to the insertion of a lumbar puncture or epidural anaesthesia in people with thrombocytopenia (low platelet count).

Background

Please see Published notes for an explanation of some technical terms.

Description of the condition

Thrombocytopenia

Thrombocytopenia is defined as a platelet count less than 150 x 109/L (BCSH 2003), and severe thrombocytopenia as a platelet count less than 50 x 109/L. Thrombocytopenia can occur due to: reduced platelet production in the bone marrow as a result of chemotherapy or a haematological malignancy (blood cancer) (Leguit 2010; Weinzierl 2013); increased platelet consumption, for example due to bleeding or disseminated intravascular coagulation (DIC) (Levi 2009); or increased platelet destruction, for example due to immune thrombocytopenia or neonatal alloimmune thrombocytopenia (Neunert 2013; Pacheco 2011; Provan 2010). Platelets are an essential component in the formation of a blood clot (BCSH 2003). A low platelet count can lead to a range of bleeding symptoms such as bruising, nosebleeds and rarely life‐threatening or fatal bleeding.

Lumbar puncture

Diagnostic

A diagnostic lumbar puncture (LP) is an invasive procedure to obtain samples of cerebrospinal fluid (CSF) (Doherty 2014). CSF is the fluid that bathes and protects the brain and spinal cord. An LP is usually performed by inserting a needle into the lower back (underneath the spinal L4 bony process) (Williams 2008). The CSF obtained can then be used for the investigation of haematological malignancies (Vavricka 2003), subarachnoid haemorrhages, meningitis (Riordan 2002), or neurological disorders. LPs are performed by doctors or specially trained nurses.

Therapeutic

Therapeutic LPs administer drugs into the CSF. This can be for the administration of therapeutics such as intrathecal chemotherapy or antibiotics, or administration of local anaesthetic to the nerves of the lower spine when a spinal anaesthetic is administered (Doherty 2014). This usually involves inserting a fine needle into the lower back, administration of the therapeutic agent and then removal of the needle (Ng 2004).

Diagnostic or therapeutic LPs are relatively common hospital procedures in people with haematological disorders who are thrombocytopenic (up to 10% of all procedures) (Estcourt 2012).

Epidural anaesthesia

The most common indication for epidural anaesthesia is in pregnant women to aid in pain relief during labour (Venn 2015). However, epidural anaesthesia can also be used in postoperative pain management especially for people with lower limb ischaemia (Venn 2015), and people undergoing thoracic surgery (Mendola 2009), as alternatives to general anaesthesia. Epidural anaesthesia typically involves inserting a larger diameter needle than a spinal needle. The epidural needle passes through the same tissues as a spinal needle but stops short of penetrating the dura (tissue sac that contains CSF). An epidural catheter is often passed through the needle and left in position so that additional local anaesthetic medications can be administered (Ng 2004).

Spinal haematoma

In the general population, the risk of a spinal haematoma is very low (1 in 200,000 epidural anaesthetic procedures during labour to 1 in 3600 epidural anaesthetic procedures in older women having knee surgery) (Li 2010; Moen 2004; Ruppen 2006; Vandermeulen 1994). Risk factors for major bleeding are multifactorial and include: increasing age (the procedure is more difficult in older people due to changes to the spine that occur with age), low platelet count, abnormal coagulation (including anticoagulant medication) and traumatic needle or catheter insertion (Erbay 2014; Li 2010; Moen 2004; Vandermeulen 1994). Performing an LP or administration of epidural anaesthesia is a relative contraindication in people with thrombocytopenia due to this perceived higher risk of complications (van Veen 2010). However, overall, there are no current reliable estimates of the risks of adverse effects such as spinal haematomas in people with thrombocytopenia (van Veen 2010).

Description of the intervention

Current practice in many countries is to correct thrombocytopenia with platelet transfusions prior to an LP or epidural anaesthesia, in order to mitigate the risk of serious peri‐ or post‐procedural bleeding. Up to 4% of all platelet components issued in the UK prior to a procedure are given to people with thrombocytopenia who need an LP (Qureshi 2007). The safe platelet count threshold recommended prior to a LP or epidural anaesthesia varies significantly from country to country.

For example the platelet count threshold for LP in the US is 50 x 109/L (Kaufman 2015); in the UK it is 50 x 109/L in adults (BCSH 2003), but 20 to 40 x 109/L in children (BCSH 2004); and in Germany it is 20 x 109/L unless it is an urgent procedure (e.g. diagnosing bacterial meningitis) when an LP should be performed irrespective of the platelet count (GMA 2009).

The platelet count threshold for epidural anaesthesia also varies. In Italy and the UK, a platelet count of at least 50 x 109/L is recommended (BCSH 2003; Liumbruno 2011), while in France a platelet count of at least 80 x 109/L is recommended (Samama 2005).

As there is currently no consensus on the standard platelet count threshold prior to an LP or epidural anaesthesia, we will compare the most commonly recommended platelet count threshold in national guidelines (50 x 109/L) against other recommended thresholds (10 x 109/L, 20 x 109/L, 30 x 109/L, 40 x 109/L, 80 x 109/L).

If guidelines recommend a platelet count threshold higher than is necessary to perform an LP or epidural anaesthesia safely then this will mean that people are exposed to the risks of a platelet transfusion unnecessarily. In 2014, 34% of all transfusion‐related adverse events reported to the UK national reporting system (Serious Hazards of Transfusion (SHOT)) were due to platelet components. The most common adverse events due to platelet components were febrile and allergic reactions (Birchall 2015). Most of these reactions are not life‐threatening but can be extremely distressing for the person. Rarer, but more serious sequelae include: anaphylaxis (life‐threatening allergic reaction), transfusion‐transmitted infections (TTI) and transfusion‐related acute lung injury (TRALI) (Blumberg 2010; Chapman 2015; Kaufman 2015; Slichter 2007; Vlaar 2013).

If guidelines recommend a platelet count threshold higher than is necessary to perform an LP safely, it may delay the start of life‐saving treatments, which can be time‐critical in conditions such as bacterial meningitis or subarachnoid haemorrhage.

Epidural anaesthesia allows for a safer and more controlled, localised anaesthesia to be administered, reducing the complications associated with general anaesthesia and reducing patient time in hospital. If guidelines recommend a platelet count threshold higher than is necessary to administer an epidural anaesthetic it may mean that a person is not offered an epidural anaesthetic and instead receives a general anaesthetic.

If guidelines recommend a platelet count threshold lower than is necessary to perform an LP or epidural anaesthesia safely, then this is putting people with thrombocytopenia at a higher risk of serious or life‐threatening bleeding such as a spinal haematoma.

How the intervention might work

Platelet transfusions are given to people with low platelet counts to increase the platelet count and, therefore, reduce the risk of bleeding during invasive procedures.

However, the risk of bleeding during or after an LP may be low in people with a low platelet count. One systematic review of platelet transfusion indications showed that bleeding events were rare in people who had thrombocytopenia undergoing diagnostic LPs; however, the quality of the evidence was low (Kumar 2015). In the review, there were five case series in children who needed an LP, nearly all the children had acute lymphocytic leukaemia. In three of these studies, children were grouped by platelet count, 243 LPs were performed at a count less than 20 x 109/L and 817 at a platelet count between 21 x 109/L and 50 x 109/L and no bleeding complications occurred (van Veen 2010). Therefore, people may be exposed to the risks of a platelet transfusion without any obvious clinical benefit.

Why it is important to do this review

The platelet count threshold recommended prior to an LP or epidural anaesthesia varies significantly from country to country (BCSH 2003; BCSH 2004; GMA 2009; Kaufman 2015). This indicates significant uncertainty by clinicians of the correct management for safely performing an LP or administering an epidural anaesthetic.

Avoiding the need for unnecessary platelet transfusions in people with thrombocytopenia will have significant logistical and financial implications for national health services as well as decreasing people's exposure to the risks of transfusion. These factors are perhaps even more important in the development of platelet transfusion strategies in low‐income countries, where access to blood components is much more limited than in high‐income countries (Verma 2009).

Objectives

To assess the effects of different platelet transfusion thresholds prior to the insertion of a lumbar puncture or epidural anaesthesia in people with thrombocytopenia (low platelet count).

Methods

Criteria for considering studies for this review

Types of studies

We will include only randomised controlled trials (RCTs), irrespective of publication status.

Types of participants

We will include people of any age with thrombocytopenia (as defined by the studies) requiring an LP or epidural anaesthesia. We will exclude people who are experiencing clinically significant bleeding at the time of the procedure because such people are routinely given platelet transfusions to treat the bleeding.

Types of interventions

We will include RCTs comparing the following two types of procedure: LP needle insertion or epidural catheter insertion.

We will compare platelet transfusion prior to the procedure when the platelet count is less than 50 x 109/L versus platelet transfusion prior to the procedure when:

  • platelet count is less than 10 x 109/L;

  • platelet count is less than 20 x 109/L;

  • platelet count is less than 30 x 109/L;

  • platelet count is less than 40 x 109/L;

  • platelet count is less than 80 x 109/L.

We will report each analysis separately, as subgroups within the main comparisons.

Types of outcome measures

Primary outcomes

  • Major procedure‐related bleeding within 24 hours of the procedure.

For example: spinal haematoma; intraventricular, intracerebral, or subarachnoid haemorrhage; or major bleeding (not further defined) as reported by individual studies.

  • All‐cause mortality up to 30 days after the procedure.

  • Serious adverse events

    • Transfusion‐related complications within 24 hours of the procedure (including transfusion‐related acute lung injury (TRALI), transfusion‐transmitted infection (TTI), transfusion‐associated circulatory overload (TACO), transfusion‐associated dyspnoea (TAD), acute transfusion reactions);

    • LP‐related complications within seven days of the procedure (infection, headache, cerebral herniation, neurological symptoms such as radicular pain or numbness, back pain).

Secondary outcomes

  • Minor LP‐related bleeding within 24 hours of the procedure (defined as prolonged bleeding at the insertion site that only requires treatment with a pressure bandage) or minor bleeding (not further defined) as reported by individual studies.

  • Duration of hospital stay (total number of days in hospital).

  • Proportion of people receiving platelet transfusions.

  • Quality of life, as defined by the individual studies

Search methods for identification of studies

The Systematic Review Initiative's Information Specialist (CD) will formulate the search strategies in collaboration with the Cochrane Haematological Malignancies Group.

Electronic searches

We will limit our searches to five main electronic databases and two ongoing trial databases.

We will combine searches in MEDLINE with the Cochrane RCT search filter, as detailed in the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2011). We will combine searches in EMBASE with the relevant Scottish Intercollegiate Guidelines Network (SIGN) RCT studies filter (www.sign.ac.uk/methodology/filters.html). We will exclude studies published in languages other than English. We will not limit searches by year of publication or publication type.

Searching other resources

We will handsearch reference lists of included studies in order to identify further relevant studies. We will contact lead authors of the included studies to identify any unpublished material, missing data or information regarding ongoing studies.

Data collection and analysis

Selection of studies

We will select studies according to Chapter 7 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a). The Systematic Review Initiative's Information Specialist (CD) will initially screen all search hits for relevance against the eligibility criteria and discard all those that are clearly irrelevant. Thereafter, two review authors (CI, LE) will independently screen all the remaining references for relevance against the full eligibility criteria using DistillerSR software. We will retrieve full‐text articles for all references for which a decision on eligibility cannot be made from title and abstract alone. We will request additional information from study authors as necessary to assess the eligibility for inclusion of individual studies. The two review authors will discuss the results of study selection and try to resolve any discrepancies between themselves. In the event that this is not possible, we will refer the decision of eligibility to a third review author (SS). We will report the results of study selection using a PRISMA flow diagram (Moher 2009).

Data extraction and management

As recommended in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a), two review authors (CI, LE) will independently extract data onto standardised forms using DistillerSR software. The data extraction form will be piloted on two included RCTs. The review authors will try to come to a consensus; if an agreement cannot be reached, they will consult a third review author (SS). The review authors will not be blinded to names of authors, institutions, journals or the study outcomes. They will extract the following information for each study.

  • Source: study ID, report ID, review author ID, date of extraction, ID of author checking extracted data, citation of paper, contact authors details.

  • General study information: publication type, study objectives, funding source, conflict of interest declared, other relevant study publication reviewed.

  • Study details and methods: location, country, setting, number of centres, total study duration, recruitment dates, length of follow‐up, power calculation, primary analysis (and definition), stopping rules, method of sequence generation, allocation concealment, blinding (of clinicians, participants and outcome assessors) and any concerns regarding bias.

  • Characteristics of interventions: number of study arms, description of experimental arm, description of control arm, type of platelet component (e.g. apheresis or pooled), dose of platelet component, type of LP needle used.

  • Characteristics of participants: age, gender, primary diagnosis, type procedure (diagnostic LP, therapeutic LP, epidural anaesthesia), platelet count, coagulation abnormalities, anticoagulant medications, antiplatelet medications.

  • Participant flow: total number screened for inclusion, total number recruited, total number excluded, total number allocated to each study arm, total number analysed (for review outcomes), number of allocated participants who received planned treatment, number of drop‐outs with reasons (percentage in each arm), protocol violations, missing data.

  • Outcomes: major procedure‐related bleeding within 24 hours of the procedure, minor procedure‐related bleeding within 24 hours of the procedure, transfusion‐related complications within 24 hours of the procedure, procedure‐related complications within seven days of the procedure, duration of hospital stay, proportion of participants receiving platelet transfusions within 24 hours of the procedure, all‐cause mortality up to 30 days from the procedure, quality of life (as defined by the individual studies).

Assessment of risk of bias in included studies

We will perform an assessment of all RCTs using the Cochrane 'Risk of bias' tool according to Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b). Two review authors (CI, LE) will work independently to assess each element of potential bias listed below as 'high', 'low' or 'unclear' risk of bias. We will report a brief description of the judgement statements upon which the authors have assessed potential bias in the 'Characteristics of included studies' table. We will ensure that a consensus on the degree of risk of bias is met through comparison of the review authors' statements and, where necessary, through consultation with a third review author (SS). We will use Cochrane's tool for assessing risk of bias, which will include the following domains.

  • Selection bias: random sequence generation and allocation concealment.

  • Performance bias: blinding of participants and personnel.

  • Detection bias: blinding of outcome assessment.

  • Attrition bias: incomplete outcome data.

  • Reporting bias: selective reporting.

  • Other bias.

Measures of treatment effect

For continuous outcomes, we will record the mean, standard deviation and total number of participants in both the treatment and control groups. For dichotomous outcomes, we will record the number of events and the total number of participants in both the treatment and control groups.

For continuous outcomes using the same scale, we will perform analyses using the mean difference (MD) with 95% confidence intervals (CIs). For continuous outcomes measured with different scales, we will present the standardised mean difference (SMD) with 95% CIs. If available, we will extract and report hazard ratios (HRs) with 95% CIs for mortality data. If HRs are not available, we will make every effort to estimate as accurately as possible the HR using the available data and a purpose built method based on the Parmar and Tierney approach (Parmar 1998; Tierney 2007).

For dichotomous outcomes, we will report the pooled risk ratio (RR) with 95% CIs. Where the number of observed events is small (less than 5% of sample per group), and where trials have balanced treatment groups, we will report the Peto's odds ratio (OR) with 95% CIs (Deeks 2011).

If data allow, we will undertake quantitative assessments using Review Manager 5 (RevMan 2014).

Where appropriate, we will report the number needed to treat for an additional beneficial outcome (NNTB) and for an additional harmful outcome (NNTH) with 95% CIs.

If we cannot report the available data in any of the formats described above, we will perform a narrative report, and, if appropriate, we will present the data in tables.

Unit of analysis issues

We do not expect to encounter unit of analysis issues as cluster‐randomised trials, cross‐over studies and multiple observations for the same outcome are unlikely to be included in this review. Should any studies of these designs arise, we will treat these in accordance with the advice given in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011c). If participants are randomised more than once, we will contact the authors of the study to provide us with data on the LP or epidural anaesthesia associated with the initial randomisation. For studies with multiple treatment groups, two review authors (CI and LE) will exclude subgroups that are considered irrelevant to the analysis. We will tabulate all subgroups in the 'Characteristics of included studies' table. When appropriate, we will combine groups to create a single pair‐wise comparison. If this is not possible, we will select the most appropriate pair of interventions and exclude the others (Higgins 2011c).

Dealing with missing data

Where data are identified to be missing or unclear in published literature, we will contact study authors directly. We will record the number of participants lost to follow‐up for each study. Where possible, we will analyse data on an intention‐to‐treat (ITT) basis, but if insufficient data are available, we will present per‐protocol analyses (Higgins 2011c).

Assessment of heterogeneity

If the clinical and methodological characteristics of individual studies are sufficiently homogeneous, we will combine the data to perform a meta‐analysis. We will assess statistical heterogeneity of treatment effects between studies using a Chi2 test with a significance level at P value < 0.1. We will use the I2 statistic to quantify the degree of potential heterogeneity and classify it as moderate if the I2 statistic is greater than 50%, or considerable if the I2 statistic is greater 80%. We perceive that we will identify at least moderate clinical and methodological heterogeneity within the studies selected for inclusion; in such cases, we will use the random‐effects model. If statistical heterogeneity is considerable, we will not report the overall summary statistic. We will assess potential causes of heterogeneity by sensitivity and subgroup analyses (Deeks 2011).

Assessment of reporting biases

Where we identify at least 10 studies for inclusion in a meta‐analysis, we will explore potential publication bias (small‐trial bias) by generating a funnel plot and using a linear regression test. We will consider a P value of less than 0.1 as significant for this test (Sterne 2011).

Data synthesis

We will perform analyses according to the recommendations of Chapter 9 of the Cochrane Handbook for Systematic Reviews of Interventions using aggregated data for analysis (Deeks 2011). For statistical analysis, we will enter data into the Review Manager 5 (RevMan 2014). One review author (CI) will enter the data and a second review author (LE) will check for accuracy.

Where meta‐analysis is feasible, we will use the random‐effects model for pooling the data. We will use the Mantel‐Haenszel method for dichotomous outcomes, and the inverse variance method (or SMDs as necessary) for continuous outcomes. In cases where event are rare, and appropriate conditions are satisfied, we will use the Peto's OR method under the fixed‐effect model. We will use the generic inverse variance method for time‐to‐event outcomes.

Summary of findings

We will use the GRADE approach to create a 'Summary of findings' table, as suggested in Chapters 11 and 12 of the Cochrane Handbook for Systematic Reviews of Interventions (Schünemann 2011a; Schünemann 2011b). We will use the GRADE approach to rate the quality of the evidence as 'high', 'moderate', 'low' or 'very low' using the five GRADE considerations.

  • Risk of bias: serious or very serious.

  • Inconsistency: serious or very serious.

  • Indirectness: serious or very serious.

  • Imprecision: serious or very serious.

  • Publication bias: likely or very likely.

We will report separate 'Summary of findings' tables for LPs and epidural anaesthesia. We will report the subgroup for each comparison that contains the largest number of studies.

The outcomes we will include are listed below.

  • Major procedure‐related bleeding within 24 hours of the procedure.

  • All‐cause mortality up to 30 days from the procedure.

  • Transfusion‐related complications within 24 hours of the procedure.

  • Procedure‐related complications within seven days of the procedure.

  • Quality of life (as defined by the individual studies).

Subgroup analysis and investigation of heterogeneity

If adequate data are available, we will perform subgroup analyses for each of the following outcomes in order to assess the effect on heterogeneity.

  • Type of procedure (diagnostic LP, therapeutic LP, epidural anaesthesia).

  • Type of participant (intensive care, liver disease, obstetric, leukaemia, other).

  • Age of participant (neonate, child (aged one to 15 years), adult (aged 16 years or older)).

  • Whether participants had associated clotting abnormalities, including DIC, or concomitant use of anticoagulant or antiplatelet agents.

If appropriate, we will also investigate heterogeneity between studies as follows.

  • Type of platelet component.

  • Dose of platelet component.

Sensitivity analysis

We will assess the robustness of our findings by performing the following sensitivity analyses where appropriate.

  • Including only studies with a 'low risk of bias' (e.g. RCTs with methods assessed as low risk for random sequence generation and concealment of treatment allocation).

  • Including only studies with less than a 20% drop‐out rate.

  • Including only studies that are published in full.