Original Investigation
Lack of seasonal variation in blood pressure in patients on hemodialysis in a North American center*,**

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Abstract

Seasonal variation in blood pressure in patients undergoing hemodialysis in Europe has recently been described. If confirmed, this has important therapeutic, research, and epidemiological implications. All normotensive patients not administered antihypertensive drugs in our unit were studied. Predialysis blood pressures were measured before each dialysis treatment over two 2-month periods, January through February and July through August, in Winnipeg, Canada, a city with one of the most extreme seasonal temperature variations in North America. No difference in blood pressures was found between summer and winter (141 ± 5/75 ± 2 versus 140 ± 4/74 ± 2 mm Hg; P = not significant). Average daily temperatures were –16°C in winter and 23°C in summer. Interdialytic weight gain was the same in both groups. In conclusion, season has no effect on blood pressure in hemodialysis patients in a North American center. Reported seasonal changes in blood pressure in Europe may be related to nonclimatic factors.

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Methods

We studied the records of our entire population of 120 patients on thrice-weekly hemodialysis therapy. Seventeen patients were identified who were not hypertensive during December 1, 1998, to September 1, 1999, and who were not administered antihypertensive drugs during that period. Nonhypertensive patients were chosen to be similar to the patients of Argiles et al,9 85% of whom were normotensive. None of the patients had clinically apparent autonomic neuropathy. Eleven patients had

Results

There was no significant difference between winter and summer blood pressures (Fig 1).

. Seasonal blood pressures. Mean ± SEM predialysis blood pressures in 17 patients in January and February (months 1 and 2) and July and August (months 7 and 8). (•–•), Systolic blood pressure; (–), diastolic blood pressure.

January through February blood pressures were 141 ± 5/75 ± 2 mm Hg compared with 140 ± 4/74 ± 2 mm Hg (P = 0.44, not significant [NS]). Similarly, individual single winter months were no

Discussion

These results show that, at least in a Canadian center, ambient temperature has no effect on predialysis blood pressures. The results contrast with a previous study from France in which blood pressure increased in winter, with a correlation between maximum ambient temperature and predialysis blood pressure.9 That winters are extreme in Winnipeg, contrary to the French center, strongly suggests that climatic temperature per se is not the cause of predialysis variations in blood pressures.

Certain

Acknowledgements

Acknowledgment: The author thanks Bunny Fontaine for assistance.

References (12)

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*

Supported in part by Baxter Corp, Mississauga, Ontario, Canada.

**

Address reprint requests to Adrian Fine, MD, Section of Nephrology, St Boniface General Hospital, 409 Tache Ave, Winnipeg, Manitoba, Canada R2H 2A6. E-mail: [email protected]

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