Thursday, 16 September 2010

Hypertension, kidney disease and pregnancy

On my first day as a consultant I was called to the antenatal clinic. Pregnancy in young women with kidney disease wasn’t particularly well covered in training back then and I gained most of my understanding of the issues by experience and asking those who knew more. A nineteenth century approach, so I have been pleased to see greater emphasis on this in training and the growing literature which is now pretty big .The new NICE Guidelines on the management of hypertension in pregnancy are a milestone in that journey of how we train and deliver care. They provide a comprehensive review of the evidence base and systematic recommendations for the diagnosis and treatment of hypertensive disorders in pregnancy in the ante-natal, intra-partum and post natal periods from 277 references, scientific papers and publications in 296 pages.

Approaching half the population get pregnant at some time in their life and hypertensive disorders in pregnancy result in substantial maternal morbidity. Maternal death is the tip of the iceberg. The young lady I saw that first morning in the ANC is now a kidney transplant recipient. A UK study reported that a third of severe maternal morbidity was a consequence of hypertensive conditions, a study conducted in the USA found that over half of admissions for acute kidney injury, one quarter of admissions for coagulopathy and nearly one third of admissions for ventilation or cerebral vascular disorders occurred in women with hypertensive disorders. A study from one region in the UK reported that one in 20 women with severe pre-eclampsia or eclampsia was admitted to intensive care.

Hypertensive disorders during pregnancy carry risks for the woman and the baby; although the rate of eclampsia in the UK seems to have fallen, hypertension in pregnancy remains one of the leading causes of maternal death in the UK, Europe and elsewhere. Delays in detailed enquiries have examined standards of care and substandard care (where different management might have been expected to prevent death) have been identified in the majority of cases. These failures of care have not just occurred in the critical care environment and in many instances like my first patient’s problems could have been predicted and avoided long before disaster struck.

More recently, the long term consequences for women with a diagnosis of hypertension during pregnancy have become clear. In particular, chronic hypertension and an increase in both life time cardiovascular risk and progressive chronic kidney disease.

The reliable detection of significant proteinuria is most important in women with hypertension during pregnancy because it distinguishes between those pregnancies with pre-eclampsia and those with gestational hypertension and it sets the scene for future complications, monitoring and management. The NICE Guidance has moved away from the old fashioned approach to proteinuria of following dipstick with a cumbersome 24 hour urine collection to the use of spot urine for a protein creatinine ratio, mirroring the banishment of 24 hour collection containers from kidney clinics up and down the country. The Guideline Development Group flagged the need for further research to confirm how significant proteinuria should be defined, identified and monitored in pregnancy amongst a range of other key research priorities.

Hypertension in pregnancy increases the risk of future development of end stage kidney disease. Women who had pre-eclampsia have an increased risk of end stage kidney disease of nearly five times that compared to those who have not been hypertensive in pregnancy. The NICE Guidance emphasises the importance of telling women and their GPs about these risks although they recommend that those who have no proteinuria or hypertension at post natal review do not require long term follow up. It is important that such women however are aware of the future risks so they are able to appreciate and modify the whole range of their vascular risk factors. They should of course be encouraged to go for the NHS vascular check at the age of 40 where blood pressure and other vascular risk factors, including in some, kidney function and proteinuria, will be assessed.