Patterns Of Blood Pressure Change Research Articles

UNDERSTANDING THE MORNING RISE IN BLOOD PRESSURE

1. The morning period has been recognized as the highest risk period of the day for cardiovascular events, particularly stroke and is also associated with a rapid surge in blood pressure. 2. Evidence now exists to show that the morning surge in blood pressure is an independent risk factor in some elderly hypertensive subjects. 3. However, methods to assess the contribution of the morning blood pressure surge from ambulatory recordings or home recordings, using clock times or times of waking, do not take into consideration the individual patterns of blood pressure change which can range from a rapid rise prior to or following waking to a slow increase over several hours. 4. In the present review we describe a novel method for determining the individual changes using a double logistic equation fitted to the individual pattern of blood pressure change. 5. Methods are presented to determine the rate of rise function over the morning period as well as predicting the change over a fixed time window which may be useful in refining the contribution of the blood pressure surge to cardiovascular risk. 6. Hypertensive people have an exaggerated rise in morning blood pressure as well as a greater rate of rise. 7. Antihypertensive drugs and dosing regimes are being developed which may be useful adjuncts to standard therapy for preventing morning hypertension and hopefully also reducing cardiovascular damage or events.

Hyperthermic effects of Durio zibethinus and its interaction with paracetamol

Because durian (Durio zibethinus), which is known in Southeast Asia as "the king of fruits", is thought to have special body-warming properties, it should not be consumed with paracetamol due to a risk of toxic effects. The claim of warming properties, however, has not been scientifically proven. This study was conducted to investigate durian's hyperthermic effect and its toxicity when consumed together with paracetamol in rats. Five groups of rats (n=6) were fed with: 1) distilled water (4 ml/250 g), 2) homogenized durian (4 g/250 g), 3) paracetamol solution (2400 mg/kg), 4) durian (4 g/250 g) followed by paracetamol solution (2400 mg/kg), or 5) prazosin solution (15 mg/kg, pregavaged) followed 1 h later by durian (4 g/250 g) and paracetamol solution (2400 mg/kg). Rectal temperature, systolic blood pressure and serum alanine aminotransferase (ALT) levels were taken from each rat at baseline and after the various administrations at 1, 2 and 5 h. Our results showed that the body temperature of rats in the durian-treated group was not significantly elevated when compared to the control. However, there was a significant decrease in body temperature over time in animals from groups 4 and 5. We did not, however, observe a consistent pattern of blood pressure change. Serum chemical analysis for ALT also did not show any significant change in any of the groups. In conclusion, contrary to what some believe, even though durian was found to increase body temperature in some rats, this increment was not significant. Rats receiving the durian-paracetamol combination showed a significant drop in body temperature, which may explain the belief that the two mixtures are toxic. However, the exact mechanism of toxicity is still unknown.

Blood Pressure Morning Surge and Hostility

This study examined the effects of hostility on blood pressure (BP) during the early morning hours before awakening and several hours afterward. Our objective was to determine whether the pattern of BP change and the slope of the morning BP surge were related to hostility. The subjects were 32 patients with a history of Stage 1 hypertension. The morning surge in BP was derived from ambulatory BP monitoring of sleeping and waking hours, which were averaged per subject and centered around the wake-up hour. The periods used were 3 h before and 3 h after awakening. Only systolic blood pressure (SBP) is being reported on in this paper as this is the primary measure found relevant to the morning surge phenomenon. Hostility was assessed by the Buss-Durkee Hostility Inventory (total score). The results revealed significant differences between low and high hostility subjects for overall levels of sleep SBP: 120 ± 11.4 mm Hg for low hostility and 131.3 ± 14.9 mm Hg for high hostility subjects ( P = .02). Low hostility subjects showed a steep rise in SBP from sleeping to waking while high hostility subjects had almost reached their post-sleep level of SBP in the hours immediately before waking up ( P = .03). These data indicate that individual differences in hostility are related to different patterns of BP during sleep and the early morning hours, a period of the day that has been associated with an increased risk of cardiovascular incidents. The data also suggest the need for further study of the significance of hostility and other personality traits and the relationship of these traits to the mechanisms of the morning surge and the risk of cardiovascular events.

Isolated Systolic Hypertension: an Important Cardiovascular Risk Factor

Hypertension is an established risk factor for cardiovascular disease morbidity and mortality. Randomized trials of antihypertensive therapy have demonstrated the benefits of treating diastolic blood pressure, and recently the value of treating isolated systolic blood pressure has also been established. There is an excess risk of cardiovascular disease in subjects with borderline isolated systolic hypertension. In fact, data from men screened for the Multiple Risk Factor Intervention Trial show that the great majority of excess deaths are in those with high-normal systolic blood pressure or with stage 1 hypertension, i.e., systolic blood pressure 130 to 159 mmHg. Similarly, data from the Framingham Heart Study and the Physicians' Health Study emphasize the importance of mild elevations of systolic blood pressure. As age increases the hemodynamic patterns of blood pressure change due to an increase in large artery stiffness, and borderline isolated systolic hypertension becomes the dominant form of hypertension. These facts make the prevention and control of borderline isolated systolic hypertension a key strategic challenge in the effort to prevent excess mortality attributable to blood pressure levels above normal.

Age-associated changes in blood pressure in a longitudinal study of healthy men and women.

Current knowledge of age-associated increases in blood pressure is based primarily on unscreened population studies that may not be representative of healthy men and women. We examined longitudinal patterns of change in blood pressure in healthy male and female volunteers from the Baltimore Longitudinal Study of Aging (BLSA). Longitudinal mixed-effects regression models are used to estimate the age-associated changes in blood pressure in 1307 men (age 17-97) and 333 women (age 18-93) who have been followed for up to 32 years (mean: 8.4 years for men and 3.4 years for women) and who have been screened for health problems or medications that affect blood pressure. On average, systolic pressure is relatively stable in men and women until approximately age 45, increases at 5-8 mm Hg per decade in middle age, then accelerates in men and stabilizes in women. Diastolic pressure increases at 1 mm Hg per decade at all ages in men, whereas in women the rate of change in diastolic pressure increases in middle age and then plateaus and may decline after age 70. Additional findings include: (a) BLSA cross-sectional and longitudinal findings are more similar than has been observed in studies of unscreened samples; (b) there is no evidence of a gender cross-over in this group of healthy men and women; and (c) compared to previous studies of unscreened samples, healthy BLSA men and women show a weaker association between baseline blood pressure and subsequent rate of blood pressure change. These findings suggest that several previously described age-associated patterns of blood pressure change partially reflect the effects of hypertension and its treatment, rather than intrinsic age changes in the blood pressure of healthy individuals.

Siesta and Ambulatory Blood Pressure Monitoring Comparability of the Afternoon Nap and Night Sleep

A prospective analysis of consecutive ambulatory blood pressure monitorings over a 5 month period identified 50 subjects (35%) who took an afternoon nap during the monitoring. The average duration of daytime sleep, as reported by the patients, was 1.8 +/- 0.6 h compared with the reported 7 +/- 2 h for nighttime sleep. Ambulatory blood pressure values during daytime awake periods were significantly higher compared with daytime sleep and nighttime sleep. The blood pressure decline during daytime sleep and nighttime sleep was similar. The pattern of blood pressure changes during daytime sleep was comparable in normotensive (n = 16), untreated (n = 10), and treated hypertensives (n = 24), irrespective of age, gender, and the level of blood pressure. The marked decline in blood pressure during daytime sleep suggests that sleep itself, rather than an endogenous circadian rhythm, is responsible for the blood pressure dip observed during both daytime sleep and nighttime sleep. Ignoring actual sleeping time in people who sleep during the day may greatly distort the day-night ambulatory blood pressure difference, when the latter is calculated on the basis of arbitrarily defined "day" and "night" periods.

The Relation between Sleep Apnea and Intra-Arterially Measured Blood Pressure in Hyperternsive Patients with Sleep Apnea Syndrome.

The relationship between sleep apnea and blood pressure was examined in 7 patients with sleep apnea syndrome (SAS). In addition, whether or not SAS is a risk factor for cerebrovascular disease was assessed. Polysomnography, including measurements of arterial O2 saturation (SaO2), was performed in 7 patients during a 3-day hospitalization period; direct intra-arterial blood pressure was continuously recorded. The blood pressure data were analyzed at the beginning of apnea, the beginning of fall in SaO2, the end of apnea, the time of maximum blood pressure, and the time of SaO2 recovery. Analysis was also carried out for 30s at 30-min intervals to assess nocturnal blood pressure variability. Two urine specimens, one accumulated from 9 a.m. to 9 p.m. and the other from 9 p.m. to 9 a.m., were collected. The pattern of blood pressure changes did not reveal the nocturnal decrease observed in normal subjects. A transient elevation of blood pressure was observed at the end of each apneic period; the mean increase in blood pressure was 28.0mmHg in systole and 16.4mmHg in diastole, and the maximum increase in systolic blood pressure was over 100mmHg. There was no significant difference between diurnal and nocturnal concentrations of urinary catecholamines, suggesting that the sympathetic activity of patients with SAS is not decreased at night. Furthermore, the transient but considerable elevation of blood pressure observed at the end of each apneic period suggests that SAS may potentially trigger cerebrovascular disease. (Hypertens Res 1993;16: 209-213)

Respiratory modulation of sympathetic activity in neonatal swine

Spontaneous efferent sympathetic activity (cervical sympathetic and splanchnic nerves) was recorded simultaneously with efferent phrenic discharge, with aortic pressure, and with the electrocardiogram in less than 1- to 51-day-old neonatal swine anesthetized with Saffan (alfaxalone). Power spectral analyses of sympathetic discharge revealed a frequency range of 4-36 Hz, with peaks distributed in four regions of the spectrum (4-6 Hz, 8-15 Hz, 16-22 Hz, and 28-36 Hz). Inspiratory modulation was readily apparent since sympathetic power spectral energy was greatest during the time of phrenic activity. Alterations in pulmonary afferent inputs (e.g., lung inflation tests and/or vagotomy) altered both phrenic and sympathetic activity. Use of the respiratory-cardiac modulation ratio indicated that respiratory modulation of sympathetic activity was greater than cardiac modulation. Complex afferent inputs, i.e., fictive Valsalva maneuver, indicated an immaturity of integration within the cardiovascular regulatory system. The adult patterns of blood pressure changes and heart rate responses were delayed until approximately 1 mo of age. Calculations of Valsalva ratios (ratio of maximal R-R interval to minimal R-R interval) indicated delayed onset of heart rate responses, reflecting the maturation of cardiovascular reflexes during the neonatal period.

Blood pressure regulation after deprivation of rapid-eye-movement sleep in rats.

We have shown previously that both sino-aortic denervation and high-renin hypertension in the rat produce a pronounced alteration in the pattern of blood pressure change during sleep; namely from unchanged to an increase in pressure during synchronized sleep, and from a slight increase to a marked decrease during desynchronized sleep. Since rapid-eye-movement sleep deprivation alters the pattern of sleep, we investigated the pattern of arterial pressure changes during sleep in rats submitted to a 48-h period of rapid-eye-movement sleep deprivation (platform technique). The deprived rats showed an increase in the number and length of desynchronized sleep episodes. Unexpectedly, they showed a blood pressure pattern change during synchronized and desynchronized sleep similar to that previously observed in sino-aortic denervated rats and in rats with high-renin hypertension: an increase in arterial pressure during synchronized sleep (+3.16 +/- 0.4 versus +0.65 +/- 0.65 mmHg in controls) and a decrease during desynchronized sleep (-6.24 +/- 0.5 versus +4.22 +/- 0.4 mmHg). These data suggest that deprivation of rapid-eye-movement sleep impairs the baroreceptor reflex function during sleep in rats.

Contribution of isosorbide-5-mononitrate, a major metabolite of isosorbide dinitrate (ISDN), to the hemodynamic effect of ISDN administered orally in conscious dogs.

This study was designed to determine the extent, to which isosorbide-5-mononitrate (5-ISMN) contributes to the hemodynamic effect of isosorbide dinitrate (ISDN) in conscious dogs. Test drugs (ISDN or 5-ISMN) were given orally. Either ISDN or 5-ISMN produced a decrease in blood pressure dose-dependently, the decrease in pulse pressure being specific; the pattern of blood pressure change induced by ISDN or 5-ISMN was different from that induced by nifedipine or prazosin. The effect of ISDN (2 mg/kg) was almost equivalent to that of 5-ISMN (4 mg/kg) and the effect of ISDN (4 mg/kg) to that of 5-ISMN (8 mg/kg). After administration of ISDN, both ISDN and 5-ISMN appeared in the plasma, and the effect of ISDN well-correlated with the increase in the plasma concentration of 5-ISMN. Contribution of 5-ISMN to the effect of ISDN was estimated to be about 30% from the value of the plasma concentration of 5-ISMN at 3 to 4 hr after administration, when the maximal response to ISDN occurred. Based on the data of the area under the plasma concentration curve of 5-ISMN (from 0 to 10 hr after administration), the fraction of biotransformation to 5-ISMN from ISDN was calculated to be 73.6 to 76.6% (based on moles). Because the ability of 5-ISMN to decrease pulse pressure was about 1/2 (or 41% based on moles) of that of ISDN, the contribution of 5-ISMN to the effect of ISDN was estimated to be about 30% in total, the value being similar with that estimated at 3 to 4 hr after administration.

体位変換に伴う血圧変化パターンよりみた降圧薬の効果

体位変換に伴う血圧変化パターンよりみた降圧薬の効果

Relationships between time of stunning and time of throat cutting and their effect on blood pressure and blood splash in lambs

A study based on 84 electrically stunned lambs showed that those gash stuck (transverse incision of the extended neck which almost simultaneously severs the trachea, oesophagus, common carotid arteries and jugular veins and the spinal cord at the occipito-atlantal junction; Blackmore & Newhook, 1976) immediately after removal of the electrical applicator had a lower incidence of blood splash than lambs gash stuck 5–8 sec r stunning. Lambs whose throats were cut immediately before the application of the electrical current had the lowest incidence of blood splash. None of the splash observed was of commercial significance. Systolic blood pressure recordings were made on a further 12 lambs of a similar age, 10 of which were electrically stunned and two shot with a captive bolt pistol. Blood pressure changes observed were related to the blood splash results obtained in the first trial. Electrical stunning raised blood pressures to an average of 3·5 times normal in lambs allowed to recover from stunning. A further seven young unweaned lambs which were electrically or percussion stunned showed a similar pattern of blood pressure change to that reported for older lambs following stunning, except that lower maximum pressures were reached. The authors interpret the results of the present trials as indicating that the application of electrical current to the heads of lambs results in damage to small vessels prior to the elevation of blood pressure. This damage may become apparent in the dressed carcass and organs as small haemorrhages. The subsequent rise in blood pressure following stunning then exacerbates the leakage of blood into tissues and it becomes more apparent in the form of discrete haemorrhages or blood splash.

Carotid Blood Pressure in Normal and Tumor-Bearing Mice

Blood pressure was measured directly in mice after cannulation of the carotid artery. The anesthetic was urethan in a single intraperitoneal dose of 1.4–1.6 mg/gm. The apparatus was a Technitrol Lilly manometer, or a Statham physiological transducer (Model P 23 D) with a Brush ‘Universal analyzer.’ The blood pressure was continuously recorded in some 400 CAF1 mice, both normal and bearers of Sarcoma 37. In 166 mice without tumor, the mean blood pressure varied from 35–110 mm of mercury; the average was 71 with a S.E. of ± 1. In 233 mice bearing 6-day-old implants of Sarcoma 37, the pressure varied from 40–110 mm.; the average was 78 ± 1 mm. Under these conditions of continuous recording of arterial blood pressure, about 40% of the animals lived for 2 hours; a few survived as long as 6 hours. The various patterns of blood pressure changes are described and illustrated.