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National Patient Safety Agency

Clinicians to check patient’s weight before treating clots

05 August 2010

The National Patient Safety Agency (NPSA) has issued guidance to NHS organisations across England and Wales to ensure that a patient’s weight is known and documented before medication is given to treat blood clots.


Doses of the injectable medicines, known as low molecular weight heparins (LMWH), are used to thin the blood to aid circulation. An underdosing carries an increased risk of further clotting of the blood, while an overdose can increase the risk of bleeding, both internally and externally. Calculating the correct treatment dose for the patient requires knowledge of a patient’s weight and renal function. 


This Rapid Response Report (RRR), issued today, follows 2,716 patient safety incidents reported to the NPSA between January 2005 and September 2009. These include one incident reported to have led to death and three reports of severe harm.


 The RRR calls on NHS organisations to ensure that:


• a patient’s weight is used as the basis for calculating the required treatment dose of LMWH. The patient’s weight must be accurately recorded and patients should be weighed at the start of therapy and where applicable during treatment;

• dosing checks based on patient information are made by healthcare professionals who review, dispense or administer LMWH when this information is readily available to them.


The guidance also suggests a patient’s renal function should be considered when prescribing treatment doses of LMWH, as a patient with poor functioning kidneys may accumulate excessive amounts of the drug in the body. This could lead to potentially severe side effects such as renal failure.


NHS organisations have also been advised on how to ensure that consistent and efficient written and verbal communication is in place to ensure the needs of the patient are met when they are transferred.


Professor David Cousins, NPSA’s Head of Patient Safety for Medication and Medical Devices, said: “LMWH is widely used throughout the NHS to treat thromboembolic events. Thousands of patients are treated safely and effectively each year with no complications or incidents that could cause harm.

“Due to the complexities around the calculation of the correct dosing, the NPSA feels that this guidance is vital. It is essential that each patient is given safe treatment and this guidance will assist clinicians and reduce the likelihood of harm.”


The guidance is available from the NPSA website: http://www.nrls.npsa.nhs.uk/resources/?entryid45=75208

Notes to editors


1. Media enquiries to the NPSA Press Office:

Simon Morgan – 020 7927 9580 / simon.morgan@npsa.nhs.uk

Dominic Stevenson – 020 7927 9351 / dominic.stevenson@npsa.nhs.uk


Out of hours – 0788 411 5956


2. Following the announcement of the arms length body review on July 26 2010, the National Patient Safety Agency (NPSA) would like to reinforce the importance of NHS organisations continuing to report patient safety incidents in the usual way through the National Reporting and Learning System. This is so that trends in safety incidents can be identified and acted upon as early as possible. 

This aspect of our work will continue within the new proposed structure of the NHS Commissioning Board and we will continue to work together in partnership with NHS organisations to make services even safer for patients


We will continue to monitor the implementation of all patient safety alerts and guidance.