NOCTURNAL HYPERTENSION

L. Grote
Medizinische Poliklinik, Philipps-University, Marburg, Germany, Baldingerstrasse,
35033 Marburg

The physiological drop in arterial blood pressure during the night has been known since the beginning of this century. The so called 20% "dipping" in systolic and diastolic blood pressure occurs in healthy subjects and also in the majority of hypertensives. Since longterm blood pressure recordings have been performed, it has been seen that some patients have a lack in this physiological drop. This pattern of 24 hour blood pressure is known as nocturnal hypertension or "non-dipping" and is frequently seen in secondary hypetension. Therefore, it is taken as an important diagnostic marker in this disease of low incidence.

In the last decade new insights have ben given in this field. The use of ambulatory 24 hour blood pressure monitoring in general practice and clinical settings have shown that "non dipping" is more frequent than before and it is related to an increase in cardiovascular risk. Stroke und left ventricular hypertrophy are linked more to Non-Dipping and females are more often susceptible than males. Also, it has been shown, that 24 hour blood pressure is altered by sleep related autonomic dysfunction for example sleep apnea and snoring.

In this lecture, the main methodological problems are discussed. Blood pressure monitoring during sleep can disturb sleep architecture. Therefore, blood pressure increases are induced. Also, insomnia and dysomnia can alter blood pressure. Study results from the comparison of continuous and discontinuous blood pressure monitoring are presented. It has been shown, that they can not follow the high blood pressure variability in autonomic dysfunction during sleep. The method of continuous non-invasive blood pressure recordings by Penaz has problems with calibration procedures and also disturbs sleep.

In Conclusion: The knowledge about blood pressure during the night and during sleep has improved. The clinical relevance of 24 hour blood pressure monitoring has been demonstrated. Methodological problems and limitations in some techniques have to be taken into consideration to distinguish between artefacts and haemodynamically significant and therapeutically important blood pressure elevations during the night and during sleep.