Early autonomic dysfunction in patients with diabetes mellitus assessed by spectral analysis of heart rate and blood pressure variability

Intraoperative alteration in the vital signs of diabetic patients during cataract surgery with local anesthesia

Purpose

Diabetic patients often have systemic circulation diseases which may cause serious systemic complications during ophthalmic surgeries with local anesthesia. The purpose of this study is to evaluate the intraoperative alteration of the vital signs in diabetic patients during cataract surgery with local anesthesia.

Methods

Clinical records of 428 patients who underwent cataract surgeries with local anesthesia were reviewed. The parameters measured were systolic/diastolic blood pressures and pulse rates at pre-operation, 5, 10 and 15 minutes during the surgeries. The factors were compared between non-diabetic patients (n = 325) and diabetic patients (n = 103).

Results

Diabetic patients had significantly higher fasting blood sugar and preoperative pulse rate. Diabetic patients showed significantly higher systolic blood pressure compared to non-diabetic patients at 5 and 10 minutes from the beginning of surgery (p = 0.0093 and 0.0075, respectively). In the non-diabetic patients, the pulse rate was significantly decreased at 5 minutes from the beginning of surgery (p = 4.74 x 10⁻⁸) which was maintained during the surgery, but no change was observed in the pulse rate of the diabetic patients.

Conclusions

Diabetic patients showed higher systolic blood pressure and pulse rate during cataract surgeries with local anesthesia, which should be monitored carefully by the physicians to avoid possible systemic complications.

Baroreflex Sensitivity in Children and Adolescents: Physiology, Hypertension, Obesity, Diabetes Mellitus

The increased prevalence of obesity in children and its complications have led to a greater interest in studying baroreflex sensitivity (BRS) in children. This review of BRS in children and adolescents includes subtopics on: 1. Resting values of BRS and their reproducibility, 2. Genetics of BRS, 3. The role of a primarily low BRS and obesity in the development of hypertension, and 4. Association of diabetes mellitus, BRS, and obesity. The conclusions specific to this age follow from this review: 1. The mean heart rate (HR) influences the measurement of BRS. Since the mean HR decreases during adolescence, HR should be taken into account. 2. A genetic dependency of BRS was found. 3. Low BRS values may precede pathological blood-pressure elevation in children with white-coat hypertension. We hypothesize that low BRS plays an active role in the emergence of hypertension in youth. A contribution of obesity to the development of hypertension was also found. We hypothesize that both factors, a primarily low BRS and obesity, are partially independent risk factors for hypertension in youths. 4. In diabetics, a low BRS compared to healthy children can be associated with insulin resistance. A reversibility of the BRS values could be possible after weight loss.

Prognostic Value of Heart Rate Variability in Patients With Cancer

INTRODUCTION

Previous studies have shown that autonomic dysfunction is associated with shorter survival in patients with advanced cancer. We examined the association between heart rate variability, a measure of autonomic function, and survival in a large cohort of patients with cancer.

METHODS

We retrospectively examined the records of 651 patients with cancer who had undergone ambulatory electrocardiogram monitoring for 20 to 24 hours. Time domain heart rate variability (SD of normal-to-normal beat interval [SDNN]) was calculated using power spectral analysis. Survival data were compared between patients with SDNN ≥ 70 milliseconds (Group 1, n = 520) and SDNN < 70 milliseconds (Group 2, n = 131).

RESULTS

Two groups were similar in most variables, except that patients in group 2 had a significantly higher percentage of male patients (P = 0.03), hematological malignancies (P = 0.04), and use of non-selective serotonin reuptake inhibitor antidepressants (P = 0.04). Patients in group 2 had a significantly shorter survival rate (25% of patients in group 2 died by 18.7 weeks vs. 78.9 weeks in group 1 patients; P < 0.0001). Multivariate analysis showed that SDNN < 70 milliseconds remained significant for survival (hazard ratio 1.9 [95% confidence interval: 1.4-2.5]) independent of age, cancer stage, and performance status.

CONCLUSION

The presence of cancer in combination with decreased heart rate variability (SDNN < 70 milliseconds) is associated with shorter survival time.

Elevated HbA1c Levels Are Associated with the Blunted Autonomic Response Assessed by Heart Rate Variability during Blood Volume Reduction

A high glycemic status increases the risk for autonomic dysfunction and cardiovascular failure. The aim of this study was to investigate time-dependent changes in the autonomic response and cardiovascular dynamics and the association between the level of hemoglobin A1c (HbA1c) and autonomic response during blood volume reduction. The study population consisted of 26 preoperative participants who were scheduled for autologous blood donation (200-400 mL of whole blood) for intraoperative or postoperative use. These participants without circulatory, respiratory, or brain disease and diabetes mellitus were grouped according to their HbA1c levels: < 6.5% (n = 18) and ≥ 6.5% (n = 8). We measured blood pressure (BP) and analyzed heart rate variability (HRV) to quantify cardiac autonomic regulation throughout blood donation. During blood volume reduction, which was about 10% of the circulating blood volume, the BP and heart rate varied within normal ranges in both groups. The high-frequency (HF) component, an index of parasympathetic nerve activity, and the ratio of low-frequency (LF) to HF components (LF/HF), an index of sympathetic nerve activity, significantly decreased and increased with the progression of blood volume reduction, respectively, in the HbA1c < 6.5% group. In contrast, in the HbA1c ≥ 6.5% group, the HF component did not significantly change, and the increase in the LF/HF ratio was delayed. Time-dependent changes in HRV were related to blood volume reduction only in the HbA1c < 6.5% group. Thus, elevated HbA1c levels are associated with the decrease in the autonomic response induced by blood volume reduction.

Two separable mechanisms are responsible for mental stress effects on high frequency heart rate variability: an intra-individual approach in a healthy and a diabetic sample

Central withdrawal of parasympathetic cardiac control and increased respiratory frequency represent two important determinants of reduced respiratory-related heart rate variability (HRV). However, studies are missing to disentangle their relative contribution during mental stress. Healthy subjects (n=10) and type 2 diabetic patients (n=8), the latter with evidence of cardiac autonomic neuropathy, participated in this study. Using an intra-individual approach, high-frequency (hf) HRV was assessed for spontaneous (during rest and mental stress) and paced breathing (0.15, 0.2, 0.25, 0.3, 0.35, 0.4 and 0.45 Hz; randomized sequence). Mental stress was induced by a challenging reaction time task. Effects of respiratory frequency on hf HRV were individually predicted by paced breathing data. Mental stress decreased hf HRV (p<.001), and increased respiratory frequency (p=.01). Individual prediction of hf HRV by stress respiratory frequency resulted in lower values (p=.02) than observed during rest, indicating that respiratory stress effects were sufficient to reduce hf HRV. However, observed hf HRV values during stress were even lower (p<.001). These results indicate that hf HRV reductions during stress can only partly be explained by concomitant respiratory frequency changes. This effect is detectable in healthy subjects and in patients with evidence of diabetic cardiac autonomic neuropathy.

Diabetic cardiovascular autonomic neuropathy: clinical implications

Diabetic cardiovascular autonomic neuropathy (DCAN), the impairment of the autonomic balance of the cardiovascular system in the setting of diabetes mellitus (DM), is frequently observed in both Type 1 and 2 DM, has detrimental effects on the quality of life and portends increased mortality. Clinical manifestations include: resting heart rate disorders, exercise intolerance, intraoperative cardiovascular lability, orthostatic alterations in heart rate and blood pressure, QT-interval prolongation, abnormal diurnal and nocturnal blood pressure variation, silent myocardial ischemia and diabetic cardiomyopathy. Clinical tests for autonomic nervous system evaluation, heart rate variability analysis, autonomic innervation imaging techniques, microneurography and baroreflex analysis are the main diagnostic tools for DCAN detection. Aldose reductase inhibitors and antioxidants may be helpful in DCAN therapy, but a regular, more generalized and multifactorial approach should be adopted with inclusion of lifestyle modifications, strict glycemic control and treatment of concomitant traditional cardiovascular risk factors, in order to achieve the best therapeutic results. In the present review, the authors provide aspects of DCAN pathophysiology, clinical presentation, diagnosis and an algorithm regarding the evaluation and management of DCAN in DM patients.

Spectral Peak Frequency in Low-Frequency Band in Cross Spectra of Blood Pressure and Heart Rate Fluctuations in Young Type 1 Diabetic Patients

In this study we tested whether joint evaluation of the frequency (fcs) at which maxima of power in the cross-spectra between the variability in systolic blood pressure and inter-beat intervals in the range of 0.06-0.12 Hz occur together with the quantification of baroreflex sensitivity (BRS) may improve early detection of autonomic dysfunction in type 1 diabetes mellitus (T1DM). We measured 14 T1DM patients (age 20.3-24.2 years, DM duration 10.4-14.2 years, without any signs of autonomic neuropathy) and 14 age-matched controls (Co). Finger arterial blood pressure was continuously recorded by Finapres for one hour. BRS and fcs were determined by the spectral method. Receiver-operating curves (ROC) were calculated for fcs, BRS, and a combination of both factors determined as F(z)=1/(1+exp(-z)), z=3.09–0.013*BRS–0.027*fcs. T1DM had significantly lower fcs than Co (T1DM: 88.8±6.7 vs. Co: 93.7±3.8 mHz; p<0.05), and a tendency towards lower BRS compared to Co (T1DM: 10.3±4.4 vs. Co: 14.6±7.1 ms/mm Hg; p=0.06). The ROC for Fz showed the highest sensitivity and specificity (71.4 % and 71.4 %) in comparison with BRS (64.3 % and 71.4 %) or fcs (64.3 % and 64.3 %). The presented method of evaluation of BRS and fcs forming an integrated factor Fz could provide further improvement in the risk stratification of diabetic patients.

Association between cardiac autonomic function, oxidative stress and inflammatory response in impaired fasting glucose subjects: cross-sectional study

Background

The worldwide burden of diabetes in 2030 is projected around 552 million. Diabetes leads to higher risk for cardiovascular diseases (CVD). Altered cardiac autonomic function (CAF) measured by heart rate variability (HRV) is observed in early stages of diabetes but the relationship between impaired fasting glucose (IFG) and HRV is still debatable. The aim of the study was to evaluate the association between CAF, oxidative stress, insulin resistance (IR), and inflammatory response in IFG subjects.

Subjects and Methods

Cross-sectional blinded study. Volunteers recruited from health awareness camps underwent CAF and biochemical tests. Based on fasting plasma glucose (FPG) participants (n = 123) were divided into two groups, normal fasting glucose (n = 76) and IFG (n = 47). The comparison of parameters between the groups was carried out using student t test and Mann-Whitney U test for parametric and non-parametric data respectively. The correlation between the parameters was analyzed by Spearman’s rank correlation using SPSS 13.0.

Results

The resting cardiovagal modulation parameters, heart rate response to forced timed breathing, and orthostatic stress were reduced in IFG subjects. Fasting plasma lipid profile, coronary atherogenic lipid risk factors, IR, thiobarbituric acid reactive substance (TBARS), high sensitive C-reactive protein, and tumor necrosis factor alpha were increased and total antioxidant capacity (TAC) was decreased significantly in IFG group but no significant alteration was observed in high-density lipoprotein (HDL-c). Cardiovagal modulation parameters were negatively correlated with triglycerides, FPG, insulin, IR, TBARS, and inflammatory markers and positively with TAC.

Conclusion

There is a continuous interplay between the altered CAF, hyperinsulinemia, IR, oxidative stress parameters, inflammatory response, and IFG in which one factor perpetuates another leading to the progression of disease.

Heart rate variability and length of survival in hospice cancer patients

We examined the association between heart rate variability (HRV) and survival duration to evaluate the usefulness of HRV as a prognostic factor for hospice cancer patients. In terminally ill cancer patients who visited the Hospice clinic, we checked demographic data, Karnofsky performance scale (KPS), HRV, dyspnea, anorexia, as well as fasting blood glucose and total cholesterol. After following up their duration of survival, we examined meaningful prognostic factors for predicting life expectancy through the survival analysis. A total of 68 patients were included in final analysis. As KPS was lower, or when combined with dyspnea or anorexia, the survival duration was much shorter. HRV parameters except heart rate were all impaired in most patients. In particular, the group with mean heart rate of 100 or more beats per minute and the group with standard deviations of normal-to-normal R-R intervals (SDNN) of 21.3 ms (75 percentile) or less showed significantly shorter survival duration. The final multivariate analysis adjusting for age, gender, fasting blood glucose, and total cholesterol showed that KPS, dyspnea, anorexia, and SDNN were significant prognostic factors in survival duration. For the first time, we report that SDNN is a prognostic factor in terminal cancer patients.

Population-based study on the prevalence and risk factors of orthostatic hypotension in subjects with pre-diabetes and diabetes

OBJECTIVE

The aim of this study was to investigate the relationship between pre-diabetes and orthostatic hypotension and to examine the prevalence and correlates of orthostatic hypotension in community dwellers with normal glucose tolerance (NGT), pre-diabetes, and diabetes.

RESEARCH DESIGN AND METHODS

All participants were classified as having NGT (n = 1,069), pre-diabetes (n = 412), or diabetes (n = 157). Orthostatic hypotension was defined as a decline in systolic/diastolic blood pressure of > or =20/10 mmHg when an individual changed from a supine to a standing position. The cardiovagal response to standing was the ratio between the longest RR interval around beat 30 and the shortest RR interval around beat 15 after standing (30 max-to-15 min ratio).

RESULTS

The prevalences of orthostatic hypotension were 13.8, 17.7, and 25.5% in subjects with NGT, pre-diabetes, and diabetes, respectively. For all subjects, age, diabetes, hypertension, and a decreased 30 max-to-15 min ratio, but not pre-diabetes, were independently associated with orthostatic hypotension. Age, hypertension, and 30 max-to-15 min ratio were the correlates of orthostatic hypotension in NGT subjects. Age and hypertension were related to orthostatic hypotension in pre-diabetic subjects. A1C and hypertension were the determinants of orthostatic hypotension in diabetic subjects. Supine blood pressure was related to orthostatic hypotension in all subjects and subgroups.

CONCLUSIONS

Pre-diabetic subjects do not have a higher risk of orthostatic hypotension than subjects with NGT, although the risk of orthostatic hypotension is higher in diabetic subjects. Hypertension and supine blood pressure were risk factors for orthostatic hypotension in both pre-diabetic and diabetic subjects. Age and A1C were the correlates of orthostatic hypotension in pre-diabetic and diabetic subjects, respectively. The cardiovagal response to standing is an important determinant of orthostatic hypotension in subjects with NGT but not in pre-diabetic and diabetic subjects.

Pathological baroreceptor sensitivity in patients suffering from somatization disorders: do they correlate with symptoms?

AIM

We conducted a study to investigate whether patients with somatization disorders (ICD-10, F45.0) show abnormal values in autonomic testing.

METHOD

35 patients with a diagnosis of somatization disorder (SP) were matched to 35 healthy volunteers (HV). International standardized autonomic testing based on heart rate variation and continuously measured blood pressure signals was used to assess autonomic activity and establish baroreceptor sensitivity (BRS). Three different statistical procedures were used to confirm the reliability of the findings.

RESULTS

There were no statistical differences between the 2 groups in age, BMI, systolic and diastolic blood pressures, and spectral values (total power, low, and high frequency power). However, heart rate was higher (p=0.044) and baroreceptor sensitivity was lower (p=0.002) in the patients compared to the healthy volunteers. Median BRS (+/-S.E.M.) of patients was 9.09+/-0.65 compared to 12.04+/-0.94 ms/mmHg in healthy volunteers. Twenty-two of the 35 patients had a BRS of -1.0S.D. below the mean of HV. SP with lower values differed from SP with normal BRS in values of total power, low-, mid-, and high-frequency bands (p<0.01 to <0.0001). No differences in psychometric testing were found between patients with lower or higher BRS. In addition, no correlation whatsoever was found in relation to autonomic variables between HV and SP, except for a higher LF/HF quotient in the latter (p<0.05).

CONCLUSION

Autonomic regulation was impaired in 62% of patients with a somatization disorder. Severity of clinical symptoms measured by psychometric instruments did not preclude autonomic function impairment. Accordingly, autonomic dysfunction may constitute an independent somatic factor in this patient group.

Female children and adolescents with type 1 diabetes have more pronounced early echocardiographic signs of diabetic cardiomyopathy

OBJECTIVE

This study was designed to assess whether children and adolescents with type 1 diabetes have early echocardiographic signs of subclinical cardiac dysfunction and whether sex, state of metabolic control, and diabetes duration are of influence.

RESEARCH DESIGN AND METHODS

Systolic and diastolic blood pressure in supine and upright positions and echocardiographic parameters, including tissue Doppler measurements of the septal mitral annulus, were evaluated in 80 children and adolescents with stable type 1 diabetes and 52 age- and sex-matched control subjects. A possible correlation was examined for age, sex, HbA(1c), and diabetes duration with univariate and multivariate regression analysis.

RESULTS

Female diabetic patients showed significantly larger left ventricular wall dimensions (left ventricular posterior wall in diastole 0.54 +/- 0.08 vs. 0.48 +/- 0.11 cm) and signs of significant diastolic filling abnormalities on conventional and tissue Doppler echocardiography (mitral valve-atrial contraction velocity 0.47 +/- 0.12 vs. 0.40 +/- 0.09 m/s; tricuspid valve-atrial contraction velocity 0.35 +/- 0.09 vs. 0.30 +/- 0.07 m/s; early filling velocity/myocardial velocity during early filling 7.15 +/- 1.47 vs. 6.17 +/- 1.07; isovolumetric relaxation time [IVRT] 66 +/- 8 vs. 58 +/- 8 ms) compared with female control subjects, suggesting delayed myocardial relaxation. Male diabetic patients only differed significantly from their control subjects for IVRT (66 +/- 9 vs. 59 +/- 8 ms). The measured parameters showed an expected correlation with age and BMI standard deviation scores in the control group. This correlation was significantly weaker in the diabetic population; only a weak influence was found for diabetes duration and glycosylated hemoglobin levels.

CONCLUSIONS

Young diabetic patients already have significant changes in left ventricular dimensions and myocardial relaxation, with the girls clearly being more affected. Tissue Doppler proved to have additional value in the evaluation of ventricular filling in this population. Almost no correlation was found for diabetes duration and HbA(1c) with the cardiovascular changes.

Diagnosis of diabetic autonomic neuropathy: a multivariate approach

AIM/HYPOTHESIS

In the diagnosis of diabetic autonomic neuropathy (DAN) various autonomic tests are used. We took a novel statistical approach to find a combination of autonomic tests that best separates normal controls from patients with DAN.

METHODS

Twenty-four patients with Type-1 diabetes mellitus considered as having mild to moderate DAN as well as 10 normal, nondiabetic control subjects were analysed, searching for a test or a combination of tests that would optimally discriminate Type-1 diabetes mellitus from controls. Variations of heart rate during deep breathing (deltaR6) and during a Valsalva manoeuvre (VR), the number of reactive sweat glands on the foot (testing sympathetic sudomotor function), and the response of human pancreatic polypeptide to hypoglycaemia [ln(deltahPP+1)] were evaluated.

RESULTS

Respective values for respective sensitivity and specificity values were: deltaR6, 96 and 70%; VR, 96 and 60%; sweat gland function, 71 and 90%; and ln(deltahPP+1), 71 and 90%. In a multivariate analysis approach a single discriminant function separating patients with Type-1 diabetes mellitus from nondiabetic controls was generated [Logit P=288.5-[14.7 deltaR6]-[26.6 ln(deltahPP+1)]]. This function allowed complete separation of patients with Type-1 diabetes mellitus from normal controls.

CONCLUSION/INTERPRETATION

We conclude that the combined determination of deltaR6 and of ln (deltahPP+1) optimally separates subjects with parasympathetic impairment from normal subjects. In addition, this combination of tests may serve as a sensitive method for the assessment of DAN.

Effects of fragrance inhalation on sympathetic activity in normal adults

We investigated the effects of fragrance inhalation on sympathetic activity in normal adult subjects using both power spectral analysis of blood pressure fluctuations and measurement of plasma catecholamine levels. Fragrance inhalation of essential oils, such as pepper oil, estragon oil, fennel oil or grapefruit oil, resulted in 1.5- to 2.5-fold increase in relative sympathetic activity, representing low frequency amplitude of systolic blood pressure (SBP-LF amplitude), compared with inhalation of an odorless solvent, triethyl citrate (P<0.05, each). In contrast, fragrance inhalation of rose oil or patchouli oil caused a 40% decrease in relative sympathetic activity (P<0.01, each). Fragrance inhalation of pepper oil induced a 1.7-fold increase in plasma adrenaline concentration compared with the resting state (P = 0.06), while fragrance inhalation of rose oil caused a 30% decrease in adrenaline concentration (P<0.01). Our results indicate that fragrance inhalation of essential oils may modulate sympathetic activity in normal adults.

QTc interval prolongation and QTc dispersion in children and adolescents with type 1 diabetes

OBJECTIVES

To evaluate whether QT interval, QT interval corrected for heart rate (QTc), and QTc dispersion changes are already present in children and adolescents with diabetes.

STUDY DESIGN

QT interval, QTc, and QTc dispersion were measured on a 12-lead surface electrocardiogram in 60 children and adolescents with stable type 1 diabetes and in 63 sex- and age-matched control subjects. Differences were evaluated by using the Kolmogorov-Smirnov Z test. The number of patients with QTc > 440 ms was compared in the two groups. The possible influence of age, sex, diabetes duration, and glycosylated hemoglobin (HbA(1c)) was examined by using Spearman correlation analysis.

RESULTS

Diabetic children had significantly longer QTc intervals and a significantly larger QTc dispersion. The number of individuals with a QTc >440 ms was significantly higher in the diabetic group (14/60) than in the control group (2/63). The effect of age on R-R interval and QTc dispersion in healthy children was less pronounced in children with diabetes. HbA(1C) values did not significantly correlate with any of the parameters.

CONCLUSIONS

QTc prolongation and a larger QTc dispersion are already present in a significant proportion of children and adolescents with diabetes.

Assessment of diabetic autonomic neuropathy using twenty-four-hour spectral analysis of heart rate variability: a comparison with the findings of the Ewing battery

A power spectral analysis of heart rate variability has been applied in order to assess diabetic autonomic neuropathy and high frequency spectra are thus considered to possibly reflect vagal nerve integrity in patients with diabetes mellitus. The purpose of this study was to investigate the relationship between the findings of high frequency spectra analysis and the results of the Ewing battery. We performed 24-hour power spectral analysis using an ambulatory ECG monitoring system and standard tests in order to assess diabetic autonomic neuropathy (Ewing battery) in 18 diabetic patients to compare their diagnostic values for diabetic autonomic neuropathy. We used the high frequency amplitude (high frequency spectra; 0.15-0.40 Hz) as a direct measure of vagal nerve integrity from each hourly spectral plot. All hourly high frequency spectra decreased along with the impaired assessment of the battery, especially during the night when the high frequency spectra showed a manifest increase in patients classified as normal according to the battery. High frequency spectra during the night while asleep (22:00-05:00) and during a 24-hour period significantly correlated with the results of the battery. These values markedly decreased even in patients classified as having early vagal damage when compared with those classified as normal. High frequency spectra during night closely reflected the intrinsic vagal nerve integrity in patients with diabetes mellitus. High frequency spectra during night or a 24-hour period is a simple and sensitive measure of diabetic autonomic neuropathy and is considered to be a useful modality for detecting even early changes in autonomic dysfunction.

Time- and frequency-domain estimation of early diabetic cardiovascular autonomic neuropathy

The risk related to cardiovascular autonomic neuropathy dysautonomia should lead to a specific assessment of this complication of diabetes. The aim of this study was to estimate the accuracy of a battery of blood pressure (BP) and heart rate (HR) variability indexes obtained in different subgroups of diabetic subjects classified according to the conventional laboratory autonomic function tests (Ewing scores). Blood pressure was measured continuously at the finger level with a Finapres monitor while subjects were in the supine position and again while they were standing. Pulse intervals were derived from BP recordings and were taken as surrogates for R-R intervals. Subjects with borderline or definite cardiovascular autonomic neuropathy showed a similar degree of alterations of both HR and BP variability (spectral measures) and in the relationship between BP and HR (cross-spectral and sequence analysis). Subjects with no evidence of cardiovascular autonomic neuropathy on the basis of the conventional tests showed an altered relationship between BP and HR. This baroreceptor-HR reflex dysfunction could represent an early stage of cardiovascular autonomic neuropathy undetected by the conventional tests. The areas under the receiver operating characteristic plots indicated that the high-frequency peak of pulse interval was highly discriminant in the supine and standing positions. The cross-spectral analysis showed the best discrimination for the gain in the high-frequency range. For the sequence analysis, the slope was the best discriminant factor for any degree of cardiovascular autonomic neuropathy. In conclusion, these estimates of baroreceptor-HR function may provide a powerful tool for assessing cardiovascular autonomic neuropathy at any stage, including the early stage, which is not detected by the conventional tests.

Hypovolemia contributes to the pathogenesis of orthostatic hypotension in patients with diabetes mellitus

PURPOSE

To investigate whether body sodium content and blood volume contribute to the pathogenesis of orthostatic hypotension in patients with diabetes mellitus.

SUBJECTS AND METHODS

Exchangeable sodium, plasma and blood volumes, and catecholamine, renin, and aldosterone levels were assessed in 10 patients with Type II diabetes mellitus who had orthostatic hypotension and control groups of 40 diabetic patients without orthostatic hypotension and 40 normal subjects of similar age and sex. In subgroups, clinical tests of autonomic function and cardiovascular reactivity to norepinephrine and angiotensin II infusions were performed.

RESULTS

In diabetic patients with orthostatic hypotension, mean (+/- SD) supine blood pressure was 165/98 +/- 27/12 mm Hg (P <0.05 compared with other groups) and mean upright blood pressure was 90/60 +/- 38/18 mm Hg. Compared with controls, diabetic patients with orthostatic hypotension had a 10% lower blood volume. They also had less exchangeable sodium than patients with diabetes who did not have orthostatic hypotension (P <0.01). Compared with both groups of controls, diabetic patients with orthostatic hypotension had decreased 24-hour urinary norepinephrine excretion and a reduced diastolic blood pressure response to handgrip (P <0.05). Moreover, they displayed reduced products of exchangeable sodium or blood volume and sympathetic function indexes. Cardiovascular pressor reactivity to norepinephrine was enhanced (P <0.01) and beat-to-beat variation decreased (P <0.01) in both groups of diabetic patients. Microvascular complications were more prevalent in the diabetic patients with orthostatic hypotension (90% vs 35%).

CONCLUSIONS

Patients who have Type II diabetes mellitus and orthostatic hypotension are hypovolemic and have sympathoadrenal insufficiency; both factors contribute to the pathogenesis of orthostatic hypotension.