Resistive index: an experimental study of acute complete unilateral ureteral obstruction

RATIONALE AND OBJECTIVES: To study the effects of acute complete unilateral ureteral obstruction (UUO) and release on porcine renal resistive index (RI). METHODS: Under general anesthesia, UUO was induced in six pigs. RI was measured bilaterally at predetermined intervals for 4 hours of UUO and 1 hour of release. Additionally, measures of renal blood flow (RBF), glomerular filtration rate (GFR), arterial blood pressure, renal vascular resistance (RVR), and ipsilateral renal intrapelvic pressure (IPP) were obtained. RESULTS: UUO and resultant progressive IPP increase caused prompt and significant ipsilateral RI elevation, and contralateral RI decrease. Concomitantly, ipsilateral RVR increased significantly while RBF and GFR declined, both significantly. Release of obstruction saw an almost immediate normalization of ipsilateral RI, RVR and RBF while ipsilateral GFR assumed 80% of baseline value 15 minutes postobstruction. Throughout the experiment, ipsilateral RI correlated significantly with changes in IPP, GFR, RBF, and RVR with correlation coefficients of 0.844, -0.851, -0.898, and 0.836 respectively ( < 0.001). CONCLUSIONS: UUO causes a divergent RI response that is instantly reversed upon release. IPP seems to be the principal effector of these changes in the early phases of UUO.     

Renal blood flow in pigs: changes depicted with contrast-enhanced harmonic US imaging during acute urinary obstruction.

PURPOSE: To evaluate contrast agent-enhanced harmonic ultrasonographic (US) imaging and Doppler hemodynamics during acute urinary obstruction. MATERIALS AND METHODS: In 12 piglets, the distal ureter was obstructed for 60 minutes, followed by intravenous injection of furosemide. In six piglets, ureteral pressure was further elevated to mean arterial pressure, and in six other piglets ureteral obstruction was released. Contrast-enhanced harmonic imaging was performed, and interlobar resistive index (RI) and renal blood flow were determined at baseline and during each experimental condition. A bolus injection curve was constructed by plotting mean pixel intensity versus time, and the area under this normalized curve was compared with renal blood flow values. RESULTS: Ureteral obstruction and high ureteral pressure reduced cortical renal blood flow to 88% and 66%, respectively, of baseline values. Administration of contrast agent resulted in marked homogeneous enhancement of the renal cortex. The area under the curve diminished during ureteral obstruction and correlated well with mean cortical blood flow. RI correlated well with renal perfusion pressure but poorly with changes in renal blood flow. CONCLUSION: Contrast-enhanced harmonic US imaging depicts changes in renal blood flow during acute obstruction. Interlobar RI is a good predictor of renal perfusion pressure but not of changes in renal blood flow.     

Renal allografts: prospective analysis of Doppler sonography

Fifty-six consecutively transplanted renal allografts were prospectively evaluated with serial Doppler sonographic examinations. Thirty-eight episodes of transplant rejection in 32 patients (63% proved pathologically) and 24 episodes of acute tubular necrosis (ATN) in 24 patients were encountered. The Doppler spectral waveform was characterized by means of the pulsatility index (PI), systolic/diastolic ratio (SDR), diastolic/systolic ratio (SDR), diastolic/systolic ratio (DSR), and resistive index (RI). Accuracy was optimized with use of top normal values as follows: PI = 1.8, SDR = 4.0, DSR = 0.25, RI = 0.75. There were no significant differences in the indices for those patients undergoing rejection versus those with ATN. The sensitivity for predicting transplant rejection was adversely affected by the history of either ATN or a previous rejection episode in the same allograft. Comparison with concurrent radionuclide examinations revealed similar sensitivities for rejection with scintigraphy and sonography. Differentiation of ATN from rejection was more reliable with scintigraphy than with sonography.     

Duplex Doppler ultrasonography of intra-renal arteries. Normal and pathological aspects]

Duplex Doppler ultrasonography may explore renal perfusion in frequent diseases such as renal obstruction, reno-vascular hypertension, acute or chronic renal failure or diabetic renal complications by measuring Pourcelot's resistive index (RI) of renal parenchyma arteries for each kidney. A statistical and prospective study was performed on 574 patients. In healthy patients, the RI values, equal for each kidney were included in 0.45 and 0.7 (mean RI = 0.59). For other values, there was a renal pathology. Patients with idiopathic hypertension (mean RI = 0.59) or non obstructive dilatation (mean RI = 0.61) did not have an RI significantly different from healthy patients. In cases of renal obstruction, there was a significant increase in the RI for the pathological kidney (mean RI of 0.73). The sensitivity and the specificity was 100% for acute obstructions examined during the first 48 hours. In contrast, in case of renal artery stenosis greater than 70% there was a significant decrease in the RI for pathological kidney. So the RI increased significantly in both kidneys: when there was renal failure with active disease within the tubulo-interstitial compartment (mean RI of 0.77); in all cases of diabetic nephropathy (mean RI of 0.74) where the RI increased early before laboratory signs. Duplex Doppler ultrasonography may be an original method for renal explorations by providing not only morphological data but also physiological data with the perfusion study.     

运用经颅多普勒超声对脑损伤血流动力学变化与脑顺应性关系的研究

目的：探讨脑血流动力学变化与脑顺应性的关系。方法：制作中、重度脑损伤动物模型，分别于伤后不同时相点用经颅多普勒超声（ＴＣＤ）仪探测猫大脑中动脉（ＭＣＡ）血流速度，计算搏动指数（ＰＩ），阻力系数（ＲＩ）及收缩峰与舒张期末血流速度比值（Ｓ／Ｄ），同时测量颅内压（ＩＣＰ）、容积压力反应（ＶＰＲ）及压力容积指数（ＰＶＩ），比较各指标间的关系。结果：脑损伤早期，ＭＣＡ血流速度增快，６小时后达高峰，以后逐渐减慢，２４小时后血流速度显著低于伤前；ＰＩ、ＲＩ及Ｓ／Ｄ值逐渐增大，２４小时后明显高于伤前（Ｐ＜０．０５）；损伤越重，变化越明显。ＩＣＰ、ＶＰＲ逐渐增大，ＰＶＩ降低。ＩＣＰ与收缩峰血流速度（Ｖｓ）、平均血流速度（Ｖｍ）、搏动指数（ＰＩ）及Ｓ／Ｄ值间有良好线性关系（Ｐ＜０．０１）；ＰＶＩ与Ｖｓ、舒张期末血流速度（Ｖｄ）、Ｖｍ及ＰＩ间有良好线性关系（Ｐ＜０．０１），但ＶＰＲ与ＭＣＡ各测量值间关系不明显。结论：ＴＣＤ仪能较好地反映脑损伤后血流动力学变化，以此可推测ＩＣＰ及脑顺应性的改变。     

Duplex Doppler analysis of interlobular arteries in transplanted kidneys

The aim of our study was to analyze changes in spectral Doppler waveforms between interlobar and interlobular arteries in renal transplants and to determine whether sampling location at interlobular level can be suitable for intrarenal resistive index (RI) measurements. Paired series of spectral tracings from interlobar arteries and respective interlobular branches were obtained in 62 consecutive renal transplants at 6.5-MHz Doppler frequency. The values of peak systolic velocity (PSV), end diastolic velocity (EDV) and RI were significantly (P < 0.01) reduced when calculated at interlobular level. In 38 % of cases, an interlobar RI higher than 0.70 corresponded to a normal interlobular RI. The values of PSV, EDV, and RI did not differ significantly at interlobular level between allograft subsets with normal and elevated serum creatinine level. Both intra- and interobserver variation were higher at interlobular than at interlobar level when performing the RI. During a conventional study of renal vasculature, an underestimation of abnormal RI findings can be expected from the incidental evaluation of interlobular tracings. We recommend sonologists to pay attention in accurately locating the sample volume at interlobar–arcuate level when evaluating intrarenal RI. Received 30 December 1996; Revision received 16 May 1997; Accepted 3 September 1997     

肾脏肿瘤患者肾动脉血流的彩色多普勒研究

目的；探讨肾脏肿瘤肾动脉血流的改变，为肿瘤的定性诊断提供一项有价值的指标。方法：运用彩色多普勒超声对32例肾肿瘤患者及30正常人的肾运用血流进行研究。结果：肾脏恶性肿瘤组肾动脉收缩期峰值流速高于肾脏良性肿瘤组及正常组（P＜0．01），阻力指数（RI）低于肾奶性肿瘤组及正常组（P＜0．01）。而肾脏奶性肿瘤组与正常组之间肾动脉的峰值血流速度及阻力指数均无明显差异。结论：肾脏恶性肿瘤患者肾动脉血流的收缩期峰值流速增高和阻力指数降低可作为其定性诊断的 一项有价值指标。     

Intrarenal Doppler ultrasound studies in normal and acutely obstructed kidneys.

Renal ultrasound examinations and intrarenal arterial Doppler studies were performed on 48 patients with normal renal tracts and 20 patients presenting with acute renal colic resulting from ureteric calculus, 14 of whom had urographic evidence of renal obstruction. The mean resistance index (RI) of the Doppler waveforms obtained on the 14 obstructed kidneys (70.4 +/- 6.22) was significantly higher than the mean RI of the 96 normal kidneys (62.4 +/- 6.43). The mean difference between the RIs of the obstructed kidneys and their contralateral non-obstructed kidneys (8.37 +/- 4.43) was also significantly higher than the differences in RI seen between pairs of normal kidneys (2.70 +/- 1.71). Five out of 14 obstructed kidneys showed no pelvicalyceal dilatation and could not have been shown to be obstructed on conventional sonography. Four of these five had RI changes suggestive of obstruction and thus 13 of 14 obstructed kidneys would have been identified as obstructed by a combination of Doppler and conventional sonographic findings. 10 of the 14 obstructed kidneys were re-examined after passage of a urinary calculus and nine showed a reduction in the RI of the previously obstructed kidneys. The 10th subsequently required ureterolithotomy.     

Acute obstruction of the renal collecting system: the intrarenal resistive index is a useful yet time-dependent parameter for diagnosis

The aim of this study was to determine whether the intrarenal resistive index (RI) can be used for the diagnosis of acute obstruction in patients with renal colic and to determine whether the index is time-related. Seventy patients referred to the Emergency Department with acute renal colic and without known associated renal disease underwent duplex Doppler ultrasonography to determine the intrarenal RI at the symptomatic and asymptomatic side. The age range of the patients was 18–72 years. An RI greater than 0.68 and/or an interrenal difference in RI greater than 0.06 and/or an increase in RI of more than 11 % compared with the normal side proved reliable cut-off values to diagnose acute renal obstruction. In addition, time dependency of the increase in RI was noted. No significant differences were observed within the first 6 h after the onset of symptoms. From 6 to 48 h, however, the mean RI in the affected kidney (0.70 ± 0.06; mean ± SD) was significantly different from that in the normal kidney (0.59 ± 0.04) (P < 0.001). In the same period the mean difference in RI was 0.08–0.13 (P < 0.001). After 48 h the sensitivity of RI dropped substantially. It is concluded that renal duplex Doppler ultrasonography is useful for diagnosing acute renal obstruction between 6 and 48 h after the onset of symptoms. Received 3 April 1997; Revision received 8 October 1997; Accepted 5 November 1997     

Pyramidal appearance and resistive index: insensitive and nonspecific sonographic indicators of renal transplant rejection

Renal transplantation patients undergoing biopsy were examined with duplex Doppler sonography to establish the sensitivity and specificity of this technique in the detection of rejection. The study population consisted of 89 consecutive patients, who received renal transplants 1 week to 17 years before our examination and underwent 96 core needle biopsies within 24 hr of sonography. The resistive index (RI), defined as the difference between the peak systolic and end diastolic flow velocities divided by the peak systolic velocity (expressed as a percentage), was measured in the main, segmental, interlobar, and arcuate renal arteries. Furthermore, the prominence of the renal pyramids, as determined by their size and echogenicity, was prospectively evaluated. Biopsy was used to establish diagnosis, but in cases of equivocal results, hospital course was the final arbiter. The most frequent diagnoses in the patients were acute rejection (41 patients) and chronic rejection (19 patients). Receiver-operating-characteristic curve analysis established that, regardless of the vessel in which it was measured, the use of RI to assign a diagnosis of acute rejection was no better than establishing this in a random manner. We did note, however, that patients with chronic rejection or cyclosporine toxicity were unlikely to have RIs greater than 80%. We further found that prominent pyramids were neither sensitive nor specific in the detection of acute rejection and that prominent pyramids were not correlated with elevated RI.     

Changes of renal blood flow after ESWL: Assessment by ASL MR imaging, contrast enhanced MR imaging, and renal resistive index

The annual incidence of stone formation is increased in the industrialised world. Extracorporeal shockwave lithotripsy is a non-invasive effective treatment of upper urinary tract stones. This study is aimed to evaluate changes of renal blood flow in patients undergoing extracorporeal shock wave lithotripsy (ESWL) by arterial spin labeling (ASL) MR imaging, contrast enhanced dynamic MR imaging, and renal resistive index (RI). Thirteen patients with nephrolithiasis were examined using MR imaging and Doppler ultrasound 12 h before and 12 h after ESWL. ASL sequence was done for both kidneys and followed by contrast enhanced MR imaging. In addition RI Doppler ultrasound measurements were performed. A significant increase in RI (p < 0.001) was found in both treated and untreated kidneys. ASL MR imaging also showed significant changes in both kidneys (p < 0.001). Contrast enhanced dynamic MR imaging did not show significant changes in the kidneys. ESWL causes changes in RI and ASL MR imaging, which seem to reflect changes in renal blood flow.     

Renal vein renin analysis: Limitations of its use in predicting benefit from percutaneous angioplasty

Two hundred forty-four consecutive patients (mean age 61 years), including 123 who had technically valid renal vein renin (RVR) analysis and 121 without RVR data, underwent technically successful percutaneous renal artery angioplasty (PTRA). They were retrospectively examined to evaluate the utility of RVR analysis in identifying renal hypertension (RVH), predicting benefit from PTRA, and determining if the lack of knowledge of renin levels significantly affected clinical outcome after PTRA. Abnormal RVR values were associated with clinical benefit after PTRA in 62 of 93 patients (67% sensitivity, 20% specificity, 72% positive predictive value). Clinical improvement following PTRA occurred in 31 of 37 patients with normal pre-PTRA RVR values (16% negative predictive value). RVR analysis correctly identified 86 of 117 patients with renovascular hypertension (74% sensitivity, 16% negative predictive value). Improved blood pressure (BP) control occurred in 72% with abnormal RVR analysis and 66% of the 121 patients without RVR data (p>0.1). We conclude that the very low negative predictive value significantly limited the use of RVR analysis in this elderly (mean age 60 years) patient population with a high incidence of mild renal functional impairment (mean serum creatinine 1.4 mg/dl) and bilateral renal artery stenosis (38%). The lack of pre-PTRA renin data did not significantly affect clinical outcome. If RVR data were relied upon as the exclusive selection criterion in patients of this type, many would be prevented from having the benefit of cure or improvement by PTRA.     

From donor to recipient. Doppler US, power US and scintigraphy of kidney perfusion before and after transplantation

PURPOSE: To follow kidneys from the donor to the recipient by assessing whether perfusion changes occur by using duplex Doppler US, power Doppler US and scintigraphy. MATERIAL AND METHODS: The prospective study included 12 donors and their corresponding 12 recipients. For each donor, both donor kidneys were evaluated by duplex Doppler US, power Doppler US and scintigraphy 1 day before surgery. The same procedure was carried out on the renal allografts at days 1, 3, 5 and months 1 and 3 post-transplantation. Power Doppler findings were classified according to a grading system of 1 to 4. Resistive indices (RIs) were determined based on interlobar and segmental arterial flow. Peak systolic velocity and RIs of the main renal artery were also measured. A perfusion parameter named the peak-to-plateau ratio was calculated. Statistical analysis was performed using the paired-samples t-test. RESULTS: Intrarenal RI elevation and decreased renal artery peak systolic velocity was observed in normally functioning recipient kidneys. CONCLUSION: Duplex Doppler sonography demonstrated that transplanted kidneys had an increase in intrarenal vascular resistance at 1 month and a decrease in renal artery peak systolic velocity at 3 months post-transplantation. Scintigraphy and power Doppler US did not reveal any statistically significant perfusion change in normally functioning kidneys from donor to recipient.     

Intrarenal arterial Doppler sonography in patients with nonobstructive renal disease: correlation of resistive index with biopsy findings

The resistive index (RI), calculated from the duplex Doppler waveform, was compared with clinical and laboratory findings and the results of renal biopsy in 41 patients with nonobstructive (medical) renal disease. Kidneys with active disease in the tubulointerstitial compartment had a mean RI of 0.75 +/- 0.07. This was statistically significantly different (p less than .01) from the RI in kidneys with disease limited to the glomeruli (mean RI of 0.58 +/- 0.05). Acute tubular necrosis resulted in an elevated RI (mean RI = 0.78 +/- 0.03) as did vasculitis/vasculopathy (mean RI = 0.82 +/- 0.05). Patients with hypertension, proteinuria, or hematuria did not have kidneys with a significantly higher RI than did patients without these clinical factors. Kidneys found to be abnormally echogenic did not have an RI significantly different from kidneys of normal echogenicity. There was a weak correlation between creatinine level and RI value, reflected by a linear correlation coefficient of 0.34. In patients with normal renal RIs, the mean creatinine level was 1.7 +/- 1.7, whereas in those with abnormal RI values (greater than or equal to 0.70), the mean creatinine level was 3.7 +/- 3.6. We conclude that some forms of nonobstructive renal disease can produce changes in the Doppler waveform detectable by RI measurement. The production of Doppler waveform changes is strongly influenced by the site of the main disease within the kidneys. Active disease within the tubulointerstitial compartment (acute tubular necrosis, interstitial nephritis) or vasculitis/vasculopathy generally resulted in an elevated RI, whereas disease limited to the glomeruli, no matter how severe, did not significantly elevate the RI. Degree of renal dysfunction as indicated by serum creatinine level probably affects the Doppler waveform to some degree, but the relationship is weak.     

胎儿肾血管彩色多普勒检测

本文报道了应用彩色多普勒超声显像仪对４６例胎儿肾动脉血流的测定结果。胎儿肾动脉血流在发育不同阶段呈规律的变化：Ｖｓ、Ｖｄ、Ｔａｍｘ、ＣＴＩ随胎龄的增加呈递增趋势，Ｖｓ／Ｖｄ随胎龄增加呈递减趋势，Ｖｓ反映肾动脉血流量，Ｖｄ反映肾动脉血管阻力，ＰＩ、ＲＩ在各胎龄期无明显差异。结果表明：应用多普勒超声检测胎儿肾动脉血流来评价胎儿周围循环状态，预测胎儿的发育情况是可行的，并且是可靠的。     

兔肾缺血-再灌注损伤后叶间动脉血流动力学变化与肾小管上皮Bcl-2表达的相关性

目的 探讨兔肾缺血-再灌注损伤后叶间动脉血流动力学变化及其与肾小管上皮Bcl-2表达的相关性.材料与方法 建立兔肾缺血-再灌注损伤模型,采用彩色多普勒血流显像(CDFI)和脉冲多普勒(PW)检测缺血-再灌注组(I/R组,n=24)兔和假手术组(S组,n=24)兔恢复血流后2h、8h、24h肾叶间动脉血流参数,包括收缩期峰值流速(Vmax)、舒张末期流速(Vd)、时间平均峰值流速(Tamax)、搏动指数(PI)和阻力指数(RI);以HE染色分析肾组织病理损伤程度;采用免疫组化SABC法检测肾小管上皮细胞中Bcl-2蛋白表达水平.结果 I/R组在2h时较S组无明显血流动力学改变,随着缺血-再灌注时间J延长,Vmax、PI、RI逐渐增大,24h时达高峰,其中RI24h较8h差异有统计学意义(P＜0.05);病理切片显示I/R组24h时肾小管上皮细胞坏死脱落程度最重;S组Bcl-2蛋白呈弱阳性表达,随着缺血-再灌注时间推移而逐渐上升,24h达高峰;叶间动脉Vmax、PI、RI与Bcl-2表达呈显著正相关(r=0.572、0.416、0.647,P＜ 0.05).结论 在兔肾缺血-再灌注中,肾叶间动脉血流动力学变化与肾小管上皮Bcl-2表达呈明显正相关,彩色多普勒超声对评价兔肾缺血-再灌损伤程度有较高价值.     

Effect of heart rate on Doppler measurements of resistive index in renal arteries

The effect of heart rate on Doppler measurements of the resistive index (RI) in renal arteries was studied in eight patients by varying paced heart rate to eliminate intrinsic and extrinsic factors influencing renal vascular resistance. A Doppler spectrum was obtained in renal segmental arteries. The RI was calculated at increasing heart rates from 70 to 120 beats per minute. There was a statistically significant decrease in RI with increasing heart rate (heart rate of 70: RI = 0.7 +/- 0.06; heart rate of 120: RI = 0.57 +/- 0.06; P less than .001), while blood pressure and cardiac output remained constant. To overcome this source of variance, the observed RI can be corrected for heart rate by using the following regression equation. For a heart rate of 80 beats per minute, corrected RI = observed RI - 0.0026(80 - observed heart rate). In interpreting the RI in renal allograft examinations, the actual heart rate of a patient must be taken into account. However, the clinical significance of standardizing the RI for heart rate requires further investigation.     

Duplex Doppler sonography of renal transplants: lack of sensitivity and specificity in establishing pathologic diagnosis

Recent reports have suggested the value of duplex Doppler sonography in the assessment of renal transplant function. Accurate diagnosis of acute rejection and its distinction from acute tubular necrosis and cyclosporine A toxicity have been claimed. We undertook a combined retrospective and prospective analysis of duplex Doppler examinations performed over a 2-year period to assess the value of such studies in evaluating renal allograft dysfunction. Seventy-seven sonographic examinations were performed on 77 renal transplants. A mean resistive index was calculated from Doppler measurements within main, segmental, and interlobar renal arteries by using the following ratio. peak systolic blood-flow velocity--minimum end-diastolic blood-flow velocity/peak systolic blood-flow velocity Forty-eight Doppler results were correlated with transplant biopsies and 29 with clinical course. Twenty-three episodes of acute allograft rejection were confirmed. When a resistive index of greater than or equal to 0.9 was used to indicate acute rejection, sonography had a sensitivity of only 9% and a specificity of 91% for this diagnosis. In one of eight cases of cyclosporine A toxicity and in three of six examples of acute tubular necrosis, the resistive index was greater than 0.9. In all six instances of chronic rejection, the resistive index was less than 0.84. None of eight patients with evidence of infection had a resistive index greater than 0.9. The resistive index range of 12 normally functioning allografts was 0.57-0.69. Correlation between the resistive index and the severity of arterial and arteriolar changes on biopsy was poor. An increased resistive index of renal transplant blood flow, as measured by duplex Doppler sonography, usually signals pathologic changes in an allograft. However, our data indicate that this test is not as sensitive or specific in identifying the cause of transplant dysfunction as has been suggested previously.     

The effects of acute hypobaric hypoxia on arterial stiffness and endothelial function and its relationship to changes in pulmonary artery pressure and left ventricular diastolic function

This study investigated, for the first time, the effects of simulated high altitude, following acute hypobaric hypoxia (HH), on simultaneous assessment of large artery stiffness and endothelial function and its inter-relationship to left ventricular (LV) diastolic function, pulmonary artery systolic pressure (PASP), and estimated PA vascular resistance (PVR). Ten healthy subjects were studied at baseline pre and following acute HH to 4800?m for a total of 180 minutes. Assessments of LV diastolic function, mitral inflow, estimated LV filling pressure (E/e'), PVR, and PASP were undertaken using transthoracic echocardiography. Simultaneous assessments of arterial stiffness index (SI), systemic vascular resistance (SVR), vascular tone, and endothelial function (reflective index [RI]) were performed using pulse contour analysis of the digital arterial waveform. Acute hypoxia led to a fall in SpO? (98.1±0.7 vs. 71.8±7.1%; p=0.0002), SVR (1589.1±191.2 vs. 1187.8±248.7; p=0.004), and RI (50.8±10.3 vs. 33.0±6.5%; p=0.0008) with an increase in PASP (24.3±2.2 to 35.0±5.3?mmHg; p=0.0001) and estimated PVR (116.40±19.0 vs. 144.6±21.5; p<0.001). There was no rise in either SI (p=0.13), mitral early annular early e' filling velocity or E/e'. There was a significant inverse correlation between SpO? and PASP (r=-0.77; p<0.0001), PVR (r=-0.57; p=0.008) and between the fall in SpO? and change (Δ) in RI (baseline vs. 150?min, r=-0.52; p<0.001). There was a modest inverse correlation between ΔRI (lower ΔRI=worsening endothelial function) and ΔPAP (r=-0.55; p=0.10) and a strong inverse correlation between ΔRI and ΔPVR (r=-0.89; p=0.0007). Acute hypobaric hypoxia does not significantly alter large artery stiffness or cause overt LV diastolic function. However, the degree of hypoxia influences both the systemic endothelial and pulmonary vascular responses. This noted association is intriguing and requires further investigation.     

Acute creatine loading increases fat-free mass, but does not affect blood pressure, plasma creatinine, or CK activity in men and women

Creatine monohydrate (CrM) administration may enhance high intensity exercise performance and increase body mass, yet few studies have examined for potential adverse effects, and no studies have directly considered potential gender differences. PURPOSE: The purpose of this study was to examine the effect of acute creatine supplementation upon total and lean mass and to determine potential side effects in both men and women. METHODS: The effect of acute CrM (20 g x d(-1) x 5 d) administration upon systolic, diastolic, and mean BP, plasma creatinine, plasma CK activity, and body composition was examined in 15 men and 15 women in a randomized, double-blind experiment. Additionally, ischemic isometric handgrip strength was measured before and after CrM or placebo (PL). RESULTS: CrM did not affect blood pressure, plasma creatinine, estimated creatinine clearance, plasma CK activity, or handgrip strength (P > 0.05). In contrast, CrM significantly increased fat-free mass (FFM) and total body mass (P < 0.05) as compared with PL, with no changes in body fat. The observed mass changes were greater for men versus women. CONCLUSIONS: These findings suggest that acute CrM administration does not affect blood pressure, renal function, or plasma CK activity, but increases FFM. The effect of CrM upon FFM may be greater in men as compared with that in women.