Friday, 23 November 2012

Evidence based practice to support a pain free labour - Two

It has been recognised for decades that there are adrenergic receptor sites on cervical smooth muscle membranes for catecholamines. There appear to be two main receptor sites, alpha-adrenergic and beta-adrenergic. The alpha-adrenergic sites, when stimulated by adrenalin in a person's blood stream, are responsible for cervical smooth muscle contracting. The evidence to guide our practice with reference to adrenergic receptor sites is freely available on the Internet and:-

Identification of alpha-Adrenergic Receptors in Uterine Smooth
Muscle Membranes by [3H]Dihydroergocryptine Binding* 
 is one such piece of research.

Another is the research conducted to compare different local analgesia given during large loop incision to the uterine cervix by Howells et al (2000).
Lignocaine with adrenalin was found to have more side effects such as shaking but caused less blood loss. These results can be attributed to the adrenalin diffusing into the woman's general circulation and causing her blood vessels to send extra blood and energy to her arms and legs which would cause shaking. If you have ever had to stand up in front of an audience and give a speech you will know all about adrenalin and shaking! The reduced blood loss can be put down to alpha-adrenergic receptors binding with the adrenalin and causing the cervical smooth muscle to contract strongly and so cut off any damaged blood vessels and so reduce blood loss. 

So, what on earth does all that mean to a labouring pregnant woman? It means that telling women about receptor sites on the uterine cervix is evidence based and so should be allowed when offering evidence based care within midwifery services.

Society repeatedly informs women that labour contractions are meant to be painful. When women go into labour they are naturally anxious. This anxiety causes the release of adrenalin by the autonomic nervous system. The adrenalin circulates in the blood and attaches itself to receptor sites on the uterine cervix causing the smooth muscle there to contract and become rigid. The cervix should be relaxed in labour so that the uterine smooth muscle can pull it up over the baby's head. If it is being held rigid by adrenalin then it is more difficult to pull up and a longer labour can be experienced causing more stress and more release of adrenalin.

Various posts within this blog describing relaxation techniques in labour striving to stop women being anxious when going into labour and so stop the release of adrenalin. The relaxation technique I generally teach to pregnant women is called Progressive Muscle Relaxation. A relaxed person does not secrete adrenalin, which is only needed in times of stress to prevent you giving birth when there is a massive tiger at the cave door looking for a quick snack.

Practicing one of the relaxation techniques is vital in pregnancy so that when labour day arrives, you can slip easily into a relaxed frame of mind. Bliss.

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