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PubMed1992

Effect of sevoflurane on intracranial pressure, sagittal sinus pressure, and the intracranial volume-pressure relation in cats.

The effect of sevoflurane on intracranial pressure (ICP), sagittal sinus pressure (SSP), and the intracranial volume-pressure (V-P) relation was examined in cats. In experiment 1, on nine cats, changes in ICP and SSP were studied for 180 min during anesthesia with 1 MAC sevoflurane (2.6%, inspired) and 50% nitrous oxide (N2O) in oxygen (O2). ICP significantly (p <0.01) increased from 8.4 +/- 3.8 cm H2O (mean +/- SD), the control level to 10.6 +/- 5.1 cm H2O immediately after the administration of sevoflurane. ICP was unchanged for the subsequent 120 min but then increased significantly (p <0.05) 140 min after administration, being 15.5 +/- 9.0 cm H2O at 180 min. There were no changes in SSP or blood gases. In experiment 2, the rapid injection technique of mock cerebrospinal fluid was used to determine the intracranial V-P relation in ten cats. Measures of V-P relationships included (a) ICP before volume injection (Po), (b) peak ICP caused by volume injection (Pp), (c) intracranial compliance (C) calculated as the ratio of change of intracranial volume Delta V) to change of ICP (Delta P), and (d) the pressure volume index (PVI) calculated as the ratio of Delta V to log Pp/Po. The subjects were divided into two groups, one administered 2.6% sevoflurane and 50% N2O in O2 (n = 6) and the other 50% N2O in O2 (n = 4). Each cat in both groups was given two bolus injections into the lateral ventricle at 180 min after the start of anesthesia. Then, C and PVI were calculated. C and PVI in the group treated with sevoflurane were significantly (p <0.05) lower than in the other group. These findings suggest that prolonged use of sevoflurane increases the intracranial elastance.

Journal Article↗
PubMed2001

Partial pressure of oxygen and partial pressure of carbon dioxide of perfluorocarbon liquid during partial liquid ventilation: their regional difference and their dependence on tidal volume and positive end-expiratory pressure level.

OBJECTIVE: To investigate the regional partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2) of the perfluorocarbon liquid (PpfcO2, PpfcCO2) during partial liquid ventilation (PLV). DESIGN: Prospective, controlled study. SETTING: A research laboratory at a university medical center. SUBJECTS: Thirteen Japanese white rabbits. INTERVENTIONS: After the tracheostomy, PLV was started with perflubron (15 ml/kg) following saline lung lavage. Fractional inspired oxygen (FIO2) was 1.0, respiratory rate was 30 bpm and tidal volume (VT) was 30 ml. Two epidural catheters (18 gauge) were inserted from the rubber diaphragm interposed in the respiratory circuit to sample perflubron. One catheter was inserted into the left lower lobe bronchus and placed at 5-6 cm distal from the carina (DISTAL). The other one was inserted at the tip of the endotracheal tube (PROXIMAL). Then the effect of the larger VT (50 ml) or positive end-expiratory pressure (PEEP; 10 cmH2O) to the gas tension in perflubron was examined. MEASUREMENTS AND MAIN RESULTS: (1) In the lower VT (30 ml) with 0 cmH20 PEEP, DISTAL PpfcO2 was significantly lower than PROXIMAL PpfcO2 (265 72 vs 386 +/- 47 mmHg, p < 0.0001), and DISTAL PpfcCO2 was significantly higher than PROXIMAL PpfcCO2 (51.1 +/- 14.4 vs 42.4 +/- 11.8 mmHg (p = 0.0007)), (2) the higher VT setting increased PpfcO2 (p = 0.0001) and decreased PpfcCO2 (p < 0.0001), although the gas tension gradient was significant, (3) 10 cmH2O PEEP increased PpfcO2 (p = 0.0004) and decreased PpfcCO2 (p = 0.0089) in the DISTAL sample. CONCLUSION: There was a difference in gas tension in perflubron between the central airway and the peripheral dependent lung region, and gas tension in perflubron was affected by the VT and the PEEP level.

Analysis of Variance↗
PubMed2004

Obstructive sleep apnea and blood pressure. Interaction between the blood pressure-lowering effects of positive airway pressure therapy and antihypertensive drugs.

BACKGROUND: There is increasing evidence that obstructive sleep apnea is an independent risk factor for arterial hypertension. Previous studies on the antihypertensive effects of positive airway pressure therapy on daytime blood pressure (BP) revealed inconsistent results. METHODS: The relations between the apnea/hypopnea index (AHI) and BP or heart rate (HR) were investigated in a cohort of 540 consecutive patients (age, 55.4 +/-11.1 years) with moderate or severe obstructive sleep apnea (OSA). The mean AHI was 28.2 +/- 22.0 events/h before OSA therapy. A group of 196 patients in whom antihypertensive medication was kept unchanged was followed for 6 months during bilevel or continuous positive airway pressure (Bi-/CPAP) therapy. RESULTS: Significant associations were found between AHI and systolic BP (beta = 0.078, P = .014), diastolic BP (beta = 0.056, P = .003), HR (beta = 0.096, P < .001), and the prevalence of arterial hypertension (odds ratio = 0.015, P = .003), independent of age, body mass index, and gender. During the follow-up period with effective Bi-/CPAP therapy, the mean daytime systolic BP decreased from 130.7 +/- 15.5 mm Hg to 128.6 +/- 15.9 mm Hg (P = .051), diastolic BP from 80.2 +/- 9.3 mm Hg to 77.5 +/- 9.5 mm Hg (P = .001), and HR from 77.7 +/- 8.8 to 75.7 +/- 8.1 beats/min (P = .001). Multiple linear regression analysis revealed that the absence of antihypertensive drugs and the level of the initial BP are significant and independent predictors for the lowering effect of Bi-/CPAP therapy on systolic and diastolic BP. CONCLUSIONS: This study confirms an independent relationship between the severity of OSA and BP/HR. Absence of BP-lowering medication and BP values before treatment are independent predictors for the reduction of BP with Bi-/CPAP therapy.

Adult↗
PubMed1999

Intracranial pressure B-waves precede corresponding arterial blood pressure oscillations in patients with suspected normal pressure hydrocephalus.

B-waves are rhythmic oscillations of intracranial pressure (ICP) with a wavelength of 0.5-2 min. These oscillations are accompanied by corresponding fluctuations of arterial blood pressure (BP). There is controversy in the literature whether the ICP oscillations precede or follow the BP oscillations. This relationship, however, is important for the understanding of the origin and the interactions of ICP B-waves with other parameters. ICP and BP were monitored continuously for one night in nine patients with suspected symptomatic normal pressure hydrocephalus (NPH). Forty-five B-waves were identified and the time delays between the peaks and the onsets of B-waves and their BP-equivalents were measured. The mean (+/- standard deviation) of the time delays between the peaks of ICP B-waves and corresponding BP-oscillations was 4.2 +/- 2.4 sec and between the onsets of the oscillations 10.3 +/- 6.6 sec. In all but two B-waves, the ICP peak preceded the BP peak, in all the 45 B-waves the onset of the ICP increase preceded the BP increase (p < 0.004). Our study demonstrates that ICP B-waves precede concomitant changes in BP by several seconds.

Aged↗
PubMed2002

Phenylephrine increases cerebral perfusion pressure without increasing intracranial pressure in rabbits with balloon-elevated intracranial pressure.

Using a rabbit model of intracranial hypertension, we studied the effects of infusion of phenylephrine on intracranial pressure (ICP) and cerebral perfusion pressure (CPP). Seven New Zealand white rabbits were anesthetized with isoflurane and normocapnia was maintained. An extradural balloon was used to raise ICP to 25 +/- 1 mm Hg. Infusion of phenylephrine increased mean arterial blood pressure (MAP) (77 +/- 6 --> 95 +/- 8 mm Hg) and CPP (52 +/- 7 --> 70 +/- 7 mm Hg). ICP was unchanged during infusion of phenylephrine (25 +/- 1 vs. 25 +/- 2 mm Hg). The phenylephrine infusion was stopped after 45 minutes and MAP returned to baseline (76 +/- 8 mm Hg). We conclude that phenylephrine increased CPP because of its effect on MAP, but did not alter ICP. Phenylephrine may be used to increase CPP without raising ICP when autoregulation is intact.

Animals↗
PubMed2006

Relationship between the frequency of blood pressure self-measurement and blood pressure reduction with antihypertensive therapy : results of the OLMETEL (OLMEsartan TELemonitoring blood pressure) study.

OBJECTIVES: This subanalysis of the OLMETEL (OLMEsartan TELemonitoring blood pressure) study in patients with essential hypertension assessed the relationship between the frequency of blood pressure self-measurement (BPSM) and the response to blood pressure (BP)-lowering therapy with olmesartan medoxomil, and the number of BP readings per week necessary to detect a mean systolic or diastolic BP reduction > or =5mm Hg. METHODS: A total of 53 patients with essential hypertension received treatment with olmesartan medoxomil 10, 20 or 40 mg daily for 12 weeks. BPSM was performed for the first 9 weeks using a TensioPhone TP2 device. Patients were instructed to measure BP at least twice daily (morning and evening). RESULTS: After the first 9 weeks of the 12-week treatment period, the extent of BP reduction correlated with the number of BPSMs. Systolic/diastolic BP reductions in patients with a 100% adherence to at least two BP measurements daily were -16.6/-8.0mm Hg compared with -0.2/-3.3mm Hg in patients with only a 75% adherence to at least one BP measurement daily. Obtaining five home BP readings per week resulted in a sensitivity of 94.8% and a specificity of 90.0% to detect a BP reduction of > or =5mm Hg. CONCLUSION: Patients adhering to the instructions for BPSM (at least two measurements daily) had a better response to antihypertensive treatment with olmesartan medoxomil. Whether BPSM per se resulted in an improved adherence to therapy or whether the number of recordings was an indicator of already existing adherence remains to be determined. Obtaining at least five home BP readings per week was identified as the threshold for correctly predicting response to olmesartan medoxomil treatment.

Adult↗
PubMed1996

Update on the 1987 Task Force Report on High Blood Pressure in Children and Adolescents: a working group report from the National High Blood Pressure Education Program. National High Blood Pressure Education Program Working Group on Hypertension Control in Children and Adolescents.

BACKGROUND: The "Report of the Second Task Force on Blood Pressure Control in Children-1987" developed normative blood pressure (BP) data for children and adolescents. These normative data are used to classify BP levels. Since 1987, additional BP data in children and adolescents, the use of newer classes of drugs, and the role of primary prevention of hypertension have expanded the body of knowledge regarding the classification and treatment of hypertension in the young. OBJECTIVE: To report new normative BP data in children and adolescents and to provide additional information regarding the diagnosis, treatment, and prevention of hypertension in children. METHODS: A working group was appointed by the director of the National Heart, Lung, and Blood Institute as chair of the National High Blood Pressure Education Program (NHBPEP) Coordinating Committee. Data on children from the 1988 through 1991 National Health and Nutrition Examination Survey III and nine additional national data sets were combined to develop normative BP tables. The working group members produced initial draft documents that were reviewed by NHBPEP Coordinating Committee representatives as well as experts in pediatrics, cardiology, and hypertension. This reiterative process occurred for 12 draft documents. The NHBPEP Coordinating Committee discussed the report, and additional comments were received. Differences of opinion were adjudicated by the chair of the working group. The final report was sent to representatives of the 44 organizations on the NHBPEP Coordinating Committee for vote. It was approved unanimously by the NHBPEP Coordinating Committee on October 2, 1995. CONCLUSIONS: This report provides new normative BP tables for children and adolescents, which now include height percentiles, age, and gender. The fifth Korotkoff sound is now used to define diastolic BP in children and adolescents. New charts have been developed to guide practicing clinicians in antihypertensive drug therapy selection. The primary prevention of hypertension in these age groups is discussed. A statement on public health considerations in the treatment of children and adolescents is provided.

Adolescent↗
PubMed2000

Diastolic pressure, systolic pressure, or pulse pressure?

Diastolic pressure, systolic pressure, and pulse pressure have all been assigned the role of the best predictor of cardiovascular events during the 20th century. At the dawn of the new millennium, concepts that draw attention to vascular mechanics reconcile the seemingly conflicting results of epidemiologic studies, better define the hypertensive patient, evaluate more accurately the risk and set its markers, and ultimately optimize treatment through a logical approach that aims at the mechanism and not at the manifestation. Pulse wave analysis and measurement of arterial stiffness are valuable tools in the assessment and management of the hypertensive patient.

Age Factors↗
PubMed2003

Repeated measures of blood pressure and correlations between systolic pressure, pulse pressure and LV mass: a circular debate?

This month's edition of the Journal contains an interesting contribution from Mule and colleagues from Palermo. The structure of the piece is very simple relating ambulatory blood pressure (ABP) measures for systolic, diastolic and pulse pressure to LV mass in hypertensive patients. The technique employed is linear correlation analysis. Pulse pressure is an area of interest of many of the readers, contributors and editorial board of the Journal. This is not a new area nor is this a new approach. The strategy of deriving biological inference from such data relevant to the individual by correlation analysis from a population sample deserves a closer and broader comment.

Blood Pressure↗
PubMedDate not supplied

Calculation of mean airway pressure during neonatal intermittent positive pressure ventilation and high frequency positive pressure ventilation.

Because mean airway pressure (MAP) is extensively used to quantify ventilation administered during the neonatal period, the accuracy and reproducibility of the techniques currently used to define MAP were assessed. All techniques were found to compare closely with MAP measured by integration of the pressure wave form even at ventilator rates in excess of 100 breaths per minute. It was therefore concluded that all methods currently used are satisfactory for clinical use.

Humans↗
PubMed2005

[Reinvestigation of CSF outflow resistance value in idiopathic normal pressure hydrocephalus--comparing epidural pressure monitoring with lumbar subarachnoid cerebrospinal fluid pressure monitoring].

PURPOSE: To compare the cerebrospinal fluid (CSF) outflow resistance values (Ro) with epidural pressure (EDP) monitoring and lumbar subarachnoid CSF pressure (L-CSFP) monitoring. SUBJECTS AND METHODS: The subjects were 14 patients with possible iNPH (age: 59-74 years old, ratio of male and female 8:6). All the patients were subjected to an infusion test by a single bolus injection method (1 ml/sec., deltaV: 5 ml, t2: 2 min) as prescribed in the Standard of SINPHONI. EDP was monitored by continuous monitoring and the L-CSFP values By intermittent simple glass tube method (SINPHONI) were measured simultaneously. The Ro (RoEDP, RoL-CSFP) calculated from both methods, (1) the correlation of Ro and (2) the Ro threshold in a shunt effective group (E: nine cases) and a non effective group (NE, five cases) were compared. RESULTS: (1) Although a favorable correlation was found between both Ro measurements (r=0.784), the RoEDP was always higher than the RoL-CSFP. (2) The mean Ro values in the E and NE groups were 36.8 +/- 15.7 mmHg/ml/min, and 10 +/- 2.05 mmHg/ml/min for Ro-EDP, 22.1 +/- 13.95 mmg/ml/min and 6.4 +/- 1.7 mmHg/ml/min for RoL-CSFP, respectively. The approximate thresholds in the E and NE groups were 15 mmHg/ml/min for RoEDP and 10 mmHg/ml/min for RoL-CSFP. CONCLUSION: (1) Although the RoEDP is always higher than the RoL-CSFP, a favorable correlation is found between the RoEDP and RoL-CSFP, (2) The Ro thresholds of the E and NE groups in the infusion test are about 15 mmHg/ml/min for RoEDP and 10 mmHg/ml/min for RoL-CSFP. (3) After this, Ro calculation ought to execute by standard of SINPHONI and the Ro threshold of the E and NE groups is about 10 mmHg/ml/min.

Aged↗
PubMed1992

Effect of torasemide on intracranial pressure, mean systemic arterial pressure and cerebral perfusion pressure in experimental brain edema of the rat.

The study was performed to establish whether a lipophilic loop diuretic, torasemide could modify intracranial pressure and cytotoxic brain edema. Brain edema was induced by water intoxication in nephrectomized rats. Following intravenous injection of 100 mg torasemide/kg body weight at 50, 60, 70, 90 and 120 min, a significant decrease of intracranial pressure was observed.

Animals↗
PubMed1992

Effect of home blood pressure and gender on estimates of the familial aggregation of blood pressure. The Tecumseh Blood Pressure Study.

Blood pressure (BP) readings from a single clinic visit are often used in population studies investigating the genetic basis of BP. We examined first-degree relatives in the Tecumseh Blood Pressure study to compare heritability estimates of BP readings obtained in the clinic-office setting (the average of two seated readings) with self-reported home BP readings (the average of 14 readings) taken over a 1-week period. The hypothesis tested was that repeated BP readings obtained in the home over the 1-week period would have fewer artifacts (i.e., environmentally induced variability in BP) and thus would better estimate the true "basal" BP that, in turn, would improve heritability estimates. We and others assume that the true basal BP level is heritable. We therefore expected that this "true" BP, by reducing BP variability of offspring, would show a stronger between-sibling correlation and that it would correlate better to parental BP as measured in a clinic setting. Correlation coefficients were calculated between siblings in the present Tecumseh study using self-reported home BP and clinic BP readings. Among 380 siblings (average age, 31.4 years), correlation coefficients for the home readings were of the same magnitude as for office readings (home, r = 0.23, p less than 0.01; office, r = 0.24, p less than 0.01). When offspring clinic BP readings were compared with archived BP data on parents, the correlation between offspring clinic and parental clinic BP readings was stronger (r = 0.24, p less than 0.05) than the correlation of offspring home BP readings to parental clinic BP readings (r = 0.17, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Pressure-volume index as a function of cerebral perfusion pressure. Part 1: The effects of cerebral perfusion pressure changes and anesthesia.

The pressure-volume index (PVI) was measured as a function of cerebral perfusion pressure (CPP) in 12 adult cats. Anesthesia was induced with methohexital in six animals and with pentobarbital in six animals; all were maintained on an N2O:O2 (70%:30%) mixture. The CPP was either increased in 10-torr increments using norepinephrine or decreased by a combination of adenosine triphosphate and hemorrhage in subgroups. Three estimations of PVI were made at each level of CPP. The PaCO2, body temperature, and hematocrit were controlled at normal levels throughout. In both groups there was a linear relationship between PVI and CPP with increasing CPP being reflected by a rise in PVI. This relationship was more marked in the methohexital group: PVI = 0.37 ml + 0.0005 mm Hg CPP in the pentobarbital group, and PVI = 0.14 ml + 0.0019 mm Hg CPP in the methohexital group. These results indicate that the PVI is not independent of CPP but is a function of CPP and is profoundly influenced by anesthesia.

Animals↗
PubMed1987

Pressure-volume index as a function of cerebral perfusion pressure. Part 2: The effects of low cerebral perfusion pressure and autoregulation.

The pressure-volume index (PVI) was measured in six adult cats while cerebral perfusion pressure (CPP) was reduced from normal levels to below the autoregulatory range by a continuous infusion of adenosine triphosphate. Anesthesia was induced with methohexital and maintained with an N2O:O2 (70%:30%) mixture. Body temperature, hematocrit, and PaCO2 were held constant throughout each experiment. Cerebral blood flow (CBF) was measured by the hydrogen clearance method. At CPP levels over 50 mm Hg, CBF remained relatively constant despite changes in CPP. Within this range, the PVI varied directly with CPP (PVI = 0.24 ml + 0.0013 mm Hg CPP). Below the autoregulatory range, CBF fell progressively with further decreases in CPP; in this range, PVI was found to increase as CPP fell (PVI = 0.84 ml - 0.0071 mm Hg CPP). These results indicate that the PVI is a complex function of CPP, varying directly with CPP within the autoregulatory range and indirectly with CPP below the autoregulatory range.

Animals↗
PubMed1989

[Determination of the blood pressure level in mild hypertension. Significance of 20 minute resting blood pressure measurement comparing to 24 hour ambulatory blood pressure monitoring].

Determination of the blood pressure (BP) level in patients with mild hypertension (MHT) is quite difficult, since ulcerations of BP are tremendously exaggerated in the doctor's office. It has been well known that casual BP is less reliable to estimate LVH than BPs obtained at home or work-site. Although 24 hour ambulatory BP monitoring (ABPM) has been widely accepted to overcome this problems, it is still controversial whether this method is applicable to all hypertensive subjects with special regards to its cost and effect. Therefore, our study has dealt mainly with the development of more convenient and less expensive method to get reasonable BPs. Twenty two nonmedicated patients with MHT were selected for the study. After taking casual BP in the office, the resting 20 minute BP measurements at every 2 minute interval were performed with Dynamap 950. Ten BP values thus obtained were divided into two categorical phases; early and late. The mean systolic and diastolic pressures (Ps & Pd) in the early phase were significantly higher than those in the late phase. Beside mean Ps and Pd obtained from 24 hour ABPM, 4 categorical phases based on the time of a day were defined; morning (from awaking to noon), afternoon (from noon to 6 pm), evening (from 6 pm to bed time) and night (during sleeping). Mutual correlation coefficients of these categorical BPs were calculated and compared to identify reasonably high significant correlations. The results revealed the highest BP at the office and the lowest one during sleeping. The office BPs closely resembled to the ones during afternoon period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Evaluation of home blood pressure measurement by a correlation study between home blood pressure and ambulatory blood pressure].

To evaluate the self-measurement of blood pressure at home, a comparative study was performed among home (Home BP), ambulatory (24-hour BP) and office blood pressure in essential hypertensive patients. In all patients, Home BP was self measured by themselves twice a day for a month. 24-hour BP was measured once during the period of self-Home BP measurement. Office BP was measured twice a month. The average of Office BP (147/92 mmHg) and Home BP (145/89 mmHg) were higher than the average of 24 hour BP (131/82 mg). For systolic BP, about two weeks self-measurement of BP at home just after waking elicited a very high correlation between home and average 24-hour BP (r = 0.82), whereas for diastolic BP the r value was moderate (r = 0.61). In patients (n = 22) treated with antihypertensives, furthermore, the correlation coefficient between home and 24-hour BP for systolic BP reached 0.89, which is higher than in all patients (n = 28). The average value of BP measured just after waking at home elicited a higher correlation with the average value of 24-hour BP compared with that measured before going to bed. The results suggest that in essential hypertensive patients who are treated with antihypertensives, to measure BP just after waking for about two weeks at home could help clinicians to evaluate and predict the value of average 24-hour BP.

Adult↗