Related Conditions: Secondary Condition

Supine Nocturnal Hypertension (SNH)

One of the downsides of taking medication to increase blood pressure and blood flow when you stand up is that it can also increase blood pressure when you lie down.

Blood pressure usually follows a day-night time rhythm. It tends to dip or go down about 10% from daytime to night. If it doesn't go down at night, it is called "nondipping". It is more common to "nondip" when a person has high blood pressure and with disorders affecting the autonomic nervous system.

The clinical relevance of this phenomenon lies in the fact that nondipping has been associated with increased frequency
of hypertensive target organ damage (brain, heart, and kidney), as well as cerebrovascular and cardiovascular events in hypertensive patients

What is Supine Nocturnal Hypertension?

Supine Nocturnal Hypertension is high blood pressure that comes with lying down at night. In some people with autonomic nervous system failure (primary autonomic failure), it is more common especially in older people.⁴ Medications used to treat the orthostatic problem can make it worse. In younger people, it is less common but may be a side effect of treatment for orthostatic intolerance.

The increased blood pressure when lying down is usually more obvious right after going to bed at night. The blood pressure would go down as the body moves the fluid and salt from the blood vessels through the kidney to the bladder.

The benefits of treating orthostatic intolerance need to be weighted against the long term risks.

 

Non-Drug Treatments for Supine Nocturnal Hypertension

1. Re-evaluate daytime medications.
   • Do not take pressor medication after 6 pm² or within 4 hours of bedtime.
2. Try a bedtime snack, including wine or alcohol. Eating causes shift of blood to the abdomen, alcohol causes dilation (increased size) of veins and pooling, which lowers BP.²
3. Be sure to remove any compression garments²
4. Raise the head of the bed to lower intracranial blood pressure²

 

Medication for Supine Nocturnal Hypertension

High blood pressure medication may be needed in people who have severe high blood pressure that is sustained (continues for hours) and does not respond to the other approahes.³

People with autonomic failure have difficulty creating compensatory reflexes with changes in position.³ Even light treatment with short-acting drugs for high blood pressure might increase the chance of fainting (syncope) and falls. The benefits need to be weighed against the risks and the medication and BP effects monitored closely.

• Nitropaste⁴ at bedtime and removed in am. Controls the BP but does not decrease nighttime diuresis and does not improve the orthostatic intolerance in the morning.
• Clonidine at bedtime

 

Effects of Supine Hypertension

Short Term Effect: In the short run, each day, increased BP at night can decrease the blood flow to the brain. There is an automatic mechanism in the brain to regulate blood flow, to protect the brain. The increased blood pressure and change in blood flow can reset the automatic regulation.That could cause more problems with regulation during the day when you stand up.⁴

Long Term: The long term effects on the brain and its blood circulation, the kidneys and the heart have not been fully studied or determined how often they occur in people with orthostatic intolerance. However, in people with primary autonomic failure, they have reported ( cardiac hypertrophy (increase in the heart muscle).⁵ There is also potential damage to the small vessels of the brain (subcortical cerebral vessels).⁴

 

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References

1. Medow MS, Stewart JM, Sanyal S, Mumtaz A, Stca D and Frishman WH. Pathophysiology, Diagnosis, and Treatment of Orthostatic Hypotension and Vasovagal Syncope. Cardiology in Review 2008;16(1):4-20. Abstract.
2. Figueroa JJ, Basford JR, Low PA. Preventing and treating orthostatic hypotension: As easy as A, B, C. Cleve Clin J Med. 2010 May;77(5):298-306.  Abstract.  Article PDF.
3. Freeman, Roy. Neurogenic orthostatic hypotension.NEJM 2008;358(6):615-624. Abstract
4. Mathias CJ. Autonomic diseases: management. J Neurol Neurosurg Psychiatry. 2003 Sep;74 Suppl 3:iii42-7.  Abstract.   Article.
5. Vagaonescu TD, Saadia D, Tuhrim S, Phillips RA, Kaufmann H. Hypertensive cardiovascular damage in patients with primary autonomic failure. Lancet 2000; 355:725-6. Abstract.
6. Okamoto LE, Gamboa A, Shibao C, Black BK, Diedrich A, Raj SR, Robertson D, Biaggioni I.  Nocturnal blood pressure dipping in the hypertension of autonomic failure. Hypertension. 2009 Feb;53(2):363-9. Epub 2008 Dec 1. Abstract. Article PDF.
7. Jordan J, Shannon JR, Pohar B, Paranjape SY, Robertson D, Robertson RM, Biaggioni I. Contrasting effects of vasodilators on blood pressure and sodium balance in the hypertension of autonomic failure. J Am Soc
   Nephrol. 1999;10:35– 42
8. Shannon J, Jordan J, Costa F, Robertson RM, Biaggioni I. The hypertension of autonomic failure and its treatment. Hypertension. 1997;30: 1062–1067.
9. Shibao C, Gamboa A, Abraham R, Raj SR, Diedrich A, Black B, Robertson D, Biaggioni I. Clonidine for the treatment of supine hypertension and pressure natriuresis in autonomic failure. Hypertension. 2006;47:522–526.

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