OAA Large Project Grant
Oxford Persisting Post-Operative Pain Study, OxPPOPS: the incidence and predictive factors of persisting pain one year after caesarean section
Dr Nicola Beale
Most patients experience pain in the days following surgery. This can usually be effectively managed with simple painkillers. It is now appreciated, however, that some patients continue to have severe pain for many months or even years after the operation. Pain is a complicated process and numerous factors can affect how much pain is experienced and for how long for. These factors include those inherently related to the patient, the type of anaesthetic and surgical techniques used, and the way that the patient's pain relief is managed by medication in the days following surgery.
Nearly one in four women gives birth by caesarean section and it is now one of the most frequently performed operations in the UK. It has been suggested that as many as 15% of these women suffer from long-term pain after caesarean section that is intense enough to disrupt their normal daily activities. This represents tens of thousands of women in the UK experiencing problems at an important time in their lives.
Oxford's Persisting Post-Operative Pain Study (OxPPOPS) is a long-term project studying pain after surgery. In particular we are interested in how many women are affected by pain one year after planned caesarean section. We are collecting data on all of the factors that may be important in the development of long-term post-operative pain. This information is gathered before, during and after caesarean section, in order to identify those factors that predict whether a woman is more likely to develop chronic pain.
We collect information pre-operatively on the psychology of the patient (for example how anxious, depressed, optimistic they are) and their sleep patterns, as well as their previous experiences and attitudes towards pain. On the day of surgery, we get the anaesthetists and surgeons to tell us what
drugs they used and how they performed the operation. We also take a blood sample so we can assess hormone levels at the time of surgery, and to store some blood for genetic analysis as early evidence suggests that some patients are genetically more vulnerable to pain than others. Immediately after the operation and throughout the first month we check the patient's pain and sleep levels and ask what medication they are taking. Longer term we follow up the patient's at four months and one year to see if they are still in pain and what affect this is having on their quality of life, psychology and sleep.
This comprehensive investigation aims to identify the factors involved in the transition from the expected acute (and healthy) pain after caesarean section to long-term chronic pain that really serves no purpose. If we can identify the women who are at greatest risk of developing chronic post-operative pain, we can introduce interventions to stop this from happening and reduce the number of women who are affected by long-term pain after caesarean section.
Is cell salvage of vaginal blood loss suitable for re-infusion?
Dr Catherine Ralph
Background
After childbirth woman can bleed and may require a blood transfusion. Donor blood transfusions are generally safe, but it is recommended that alternatives should be considered whenever possible. The supply of donated blood is limited, each unit costs £125, and following a blood transfusion you are unable to donate blood.
About 1 in 4 women will have a caesarean section to deliver their baby. Any blood lost during the operation can be collected and recycled using a cell salvage machine. Recycled blood is an alternative to donor blood. It is warm and supplies oxygen to the cells better than cold donated blood.
At The Royal Cornwall Hospital (RCH) we offer almost all women having a C section the opportunity to have recycled blood. Women who have received recycled blood usually avoid having a donor blood transfusion.
Unfortunately only blood collected at the time of a sterile operation is considered suitable for recycling. Women who bleed after a vaginal delivery, do not have the chance to use this recycling technique. We do not know if blood lost through the vagina is suitable for recycling. Many women lose more than 500mls of blood following a vaginal delivery. For most of these
women this blood loss does not affect their recovery, however some lose a lot and will go on to get donor blood.
Aim
To recycle blood lost vaginally and use it like blood recycled from an operation.
Using recycled vaginal blood to reduce the amount of donor blood used.
Methodology
To check the safety of using recycled vaginal blood we will collect blood following vaginal deliveries.
After the baby is born some women will start to bleed. As soon as this is recognised, an adhesive drape will be placed around the perineum (vaginal area). Any blood lost will drip into a sterile bucket in which there will be saline (salty water) and an anti-clotting agent (heparin). If more than 200mls of blood is collected, it can be taken from the delivery area for recycling. Once the blood has been processed and recycled by the cell salvage machine, samples will be taken for testing.
There are special tests routinely done, in the laboratory, to check the quality and safety of recycled blood. The tests include looking at the blood count, the red blood cells and for any contamination of baby cells .We will do these same tests for the samples of recycled vaginal blood. The samples will be taken before the blood is washed and also repeated after washing and recycling. In addition to the normal tests we will do a test to check for contamination or infection.
Expected outcomes
We will look at the quality of 50 samples. Depending on the quality we may be able to safely use recycled vaginal blood in the future, but we do not intend using it during this project.
Implications
If we are able to recycle blood lost vaginally, we can offer cell salvage to all women following childbirth and not just those who have a caesarean section. This will reduce the number of donor blood transfusions used and improve recovery after childbirth.
Quantification of the pressures generated during insertion of an epidural needle and subsequent imaging of the epidural space in labouring women of varying body mass
Professor Michael Wee
a) Background:
Epidurals can result in serious complications. Incidence of permanent harm from obstetric epidurals range from 0.2 in 100,000 to 1.24 in 100,000 and include spinal infections and direct nerve injury. Approximately 1% of patients who have an epidural suffer post-dural puncture headache (PDPH), a specific complication which can be extremely disabling. The risks of injury in obese women are increased due to technical difficulties. Changes to the training structure of trainee anaesthetists and the need for compliance with the European Working Time Directive (reduced training opportunities) further compound this situation.
b) Aims:
The primary aim is to measure the pressure required to reach the epidural space when inserting an epidural needle into pregnant women of varying body mass indices. Correlation will then be made with ultrasound and Magnetic Resonance Imaging (MRI) scans of their lumbar spine. The scans will permit the creation of accurate 3D computer graphics. The secondary aim is to create a novel epidural simulator utilising specific patient data with computer graphics modelling of the lumbar spine. This simulator will be used by anaesthetists to practice the epidural technique in a controlled environment. The computer-based simulator will be able to give realistic feedback to the user. This force-feedback should mimic as far as possible the real life situation.
c) Methodology:
Four groups of pregnant women with body mass indices (BMIs) between 18-24.9; 25-34.9; 35-44.9 and over 45 will be recruited following the provision of study information and informed consent. The women will be recruited antenatally and also in early labour if they have expressed a desire to have an epidural at some point during their pregnancy and early labour. An ultrasound scan of the lower back will be performed before insertion of the epidural. The pressure applied to the epidural needle will be measured using a pressure transducer attached to the needle. As the anaesthetist inserts the epidural into the lumbar tissues and ligaments, the change in pressures will be recorded via the transducer and transmitted wirelessly to a remote receiver. We have validated the pressure measuring system in a porcine trial. Following the epidural, an MRI scan of the lower spine will be performed within 72hrs of giving birth and these images will be utilised for computer graphics modelling together with the ultrasound images.
d) Expected outcomes:
We expect to find that as BMI increases, the depth of the epidural space will increase. It is unknown however whether there is any difference in the make-up of the ligaments between women of different BMIs and whether this influences the resultant pressure in the ligaments.
e) Implications of study:
The challenge is to develop a novel simulator to assist anaesthetic training to reduce harm to patients. This study will generate a model that can reproduce the actual 'feel' of an epidural based on in vivo measurements. Much of what is learnt evolves from sensing subtle changes in pressure as the needle travels through different ligaments. Knowing these pressures allows for more realistic modelling. Addition of data from ultrasound and MRI serve to enhance simulation. The advantage of this study is the integration of resultant ligamental pressures and images between women with varying BMIs to develop a novel simulator based on patient-specific data. The utility of the novel simulator will be tested in a further clinical trial of trainee anaesthetists.
