The utility of quantitative calf muscle near-infrared spectroscopy in the follow-up of acute deep vein thrombosis

Online Noninvasive Assessment of Human Brain Death by Near-Infrared Spectroscopy with Protocol of O2 Inspiration

Brain death is the irreversible loss of all the functions of the brain and brainstem. Compared to traditional diagnostic methods of brain death, near-infrared spectroscopy (NIRS) is a noninvasive, objective, cost-effective, and safe way of assessment of brain death. Eighteen brain dead patients and 20 healthy subjects were studied by NIRS, with a multiple-phase protocol at varied fractions of inspired O₂ (FIO₂). We found that the changes in the concentration ratios of oxyhemoglobin to deoxyhemoglobin (Δ[HbO₂]/Δ[Hb]) in the cerebral cortex of brain dead patients were significantly higher than those of healthy subjects, and its low-to-high FIO₂ phase was most sensitive, with a recommended threshold in the range 1.40-1.50. Our study indicated that NIRS is a promising technology for assessing brain death. The success of this application potentially offers a supplementary technique for the assessment of brain death in real time in order to be able to promptly offer quality-assured donor organs.

Time taken to the maximum increase in the oxygenated hemoglobin level in calf muscle as a predictor of mild and moderate post-thrombotic syndrome

BACKGROUND

Near-infrared spectroscopy (NIRS) allows continuous noninvasive monitoring of changes in the tissue levels of oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) and can identify the severity of chronic venous diseases. Here we investigated the predictors of post-thrombotic syndrome (PTS) using NIRS in patients with a first episode of deep venous thrombosis (DVT).

METHODS

The study enrolled 129 patients with DVT. Risk factors in each patient were assessed at presentation. Venous abnormalities confirmed by ultrasound and parameters derived from NIRS were evaluated at 6 months after DVT. On standing, increases in O2Hb and HHb (ΔO2Hbst and ΔHHbst) and the times taken for each concentration to become maximal (TO2Hbst, and THHbst) were measured. During 10 tiptoe movements, O2Hb showed a continuous decrease (ΔO2Hbex), whereas venous expulsion (ΔHHbEex) and subsequent retention (ΔHHbRex) were observed. The oxygenation index (HbD; HbD = O2Hb - HHb) was also calculated at the end of standing and at the end of 10 tiptoe movements (ΔHbDst and ΔHbDex). Final clinical manifestations were evaluated at 6 years, and PTS was considered to be present if the Villalta score was ≥5.

RESULTS

Thirteen patients were excluded and 116 patients were finally included. Of these, 19 (16%) developed PTS. Among various NIRS-derived parameters, TO2Hbst had the highest area under the curve (0.88; 95% confidence interval [CI], 0.80-0.93; P < .01) with the best cutoff value (TO2Hbst ≤48 seconds). On univariate analysis, variables associated with greater risk for development of PTS were stroke (odds ratio [OR], 5.59; 95% CI, 0.74-42.41; P = .06), idiopathic DVT (OR, 4.13; 95% CI, 1.36-12.55; P < .01) and iliofemoral DVT (OR, 4.31; 95% CI, 1.48-12.60; P < .01) at initial presentation, venous occlusion combined with reflux (OR, 4.24; 95% CI, 1.50-12.00; P < .01), and NIRS-derived TO2Hbst ≤48 seconds (OR, 43.03; 95% CI, 9.04-204.81; P < .01) at 6 months. Multivariate logistic regression analysis finally revealed venous occlusion combined with reflux (OR, 4.80; 95% CI, 1.03-22.36; P < .05) and NIRS-derived TO2Hbst ≤48 seconds (OR, 53.73; 95% CI, 8.43-342.41; P < .01) to be independently associated with PTS progression.

CONCLUSIONS

NIRS-derived TO2Hbst ≤48 seconds is a promising time-course predictor of PTS progression.

Measurement of calf muscle oxygenation during light-intensity exercise in patients with post-thrombotic syndrome

BACKGROUND

Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in the levels of oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) in tissues. The purpose of this study was to investigate changes in calf muscle O2Hb and HHb levels during standing and exercise in the follow-up of deep venous thrombosis (DVT).

METHODS

Forty-three patients with a first episode of unilateral proximal DVT were included. Final clinical manifestations were evaluated at a mean follow-up point of 53 months after diagnosis of DVT, and post-thrombotic syndrome (PTS) was considered to be present if the Villalta score was >5. Moreover, to assess the severity of PTS, the revised Venous Clinical Severity Score (VCSS) was employed. NIRS was used to measure changes in the levels of O2Hb and HHb in calf muscle. On standing, increases in O2Hb and HHb were calculated by subtracting the baseline value from the maximum value (ΔO2Hbst and ΔHHbst). The times taken for the O2Hb and HHb concentrations to become maximal (TO2Hbst, and THHbst) were also measured. During 10 tiptoe movements, the relative change in O2Hb was calculated by subtracting the value measured at the end of exercise from the value measured at the beginning of exercise (ΔO2Hbex). On the other hand, 10 tiptoe movements produced venous expulsion (ΔHHbEex) and a subsequent retention (ΔHHbRex). The oxygenation index (HbD; HbD = O2Hb - HHb) was also calculated at the end of standing and at the end of 10 tiptoe movements (ΔHbDst and ΔHbDex).

RESULTS

Among the 43 limbs evaluated, 21 had PTS. On standing, the ΔHbDst was significantly decreased in patients with PTS relative to the patients without PTS (12 ± 8, 22 ± 11 μmol/L; P = .001). The TO2Hbst was also significantly reduced in patients with PTS relative to those without (43 ± 41, 107 ± 58 seconds; P = .001). During 10 tiptoe movements, the ΔHHbEex was significantly reduced in patients with PTS relative to those without (-2 ± 1, -3 ± 3 μmol/L; P = .016). Similarly, the ΔHHbRex was significantly increased in patients with PTS relative to those without (8 ± 7, 3 ± 2 μmol/L; P = .001). Furthermore, falls in ΔHbDex were more pronounced in patients with PTS (-10 ± 16, 10 ± 10 μmol/L; P < .001). NIRS-derived TO2Hbst (r = -0.568; P < .001) and ΔHbDex (r = -0.645; P < .001) showed strong inverse correlations with VCSS. Similarly, NIRS-derived ΔHHbEex (r = 0.409; P < .01) and ΔHHbRex (r = 0.476; P < .01) showed moderate positive correlations and ΔHbDst (r = -0.422; P < .01) had a moderate inverse correlation with VCSS.

CONCLUSIONS

Changes in O2Hb and HHb concentrations differ between patients with and without PTS. The reduced TO2Hbst may indicate impairment of the venoarteriolar reflex in patients who have PTS. Furthermore, severe falls in HbD in patients with PTS might reflect the pain of venous claudication. These findings may have implications for investigations of the microcirculation in the context of post-thrombotic sequelae.

Measurements of calf muscle oxygenation during standing and exercise in patients with primary valvular insufficiency

OBJECTIVE

Despite the established role of the calf muscle pump for preventing chronic venous disorders, hemoglobin flow in the calf muscle is poorly understood. Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in tissue-oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) levels. The purpose of this study was to investigate the changes in calf muscle O2Hb and HHb levels during standing and exercise in patients with primary valvular insufficiency (PVI).

METHODS

Eighty-three limbs in 81 patients with PVI were enrolled. The clinical manifestations of these patients were categorized according to the CEAP (Clinical, Etiologic, Anatomical, and Pathophysiologic) classification, and patients were divided into group I (C1-3S,Ep,As,d,p,Pr) and group II (C4-6S,Ep,As,d,p,Pr). Moreover, to assess the severity of PVI, the revised Venous Clinical Severity Score (VCSS) was employed. NIRS was used to measure changes in the calf muscle O2Hb and HHb levels. On standing, increases in O2Hb and HHb were calculated by subtracting the baseline value from the maximum value (ΔO2Hbst and ΔHHbst). The time elapsed until the maximum increases in O2Hb and HHb concentrations (TO2Hbst, and THHbst) were also measured. During 10 tiptoe movements, the relative change in O2Hb was calculated by subtracting the value measured at the end of exercise from the value measured at the beginning of exercise (ΔO2Hbex). On the other hand, 10 tiptoe movements produced venous expulsion (ΔHHbEex) and a subsequent retention (ΔHHbRex). The oxygenation index (HbD; HbD = O2Hb - HHb) was also calculated at the end of standing and 10 tiptoe movements (ΔHbDst and ΔHbDex).

RESULTS

Among the 83 limbs evaluated, 48 were classified as group I and 35 as group II. Standing caused increases in the levels of both ΔO2Hbst and ΔHHbst. However, there were no significant differences in these increases between the two groups. In contrast, the TO2Hbst was significantly reduced in group II in comparison with group I (55 ± 29 vs 36 ± 30 seconds; P = .007). During 10 tiptoe movements, a decrease in O2Hb concentration was observed, and there was no significant difference in ΔO2Hbex between group I and group II. In contrast, the ΔHHbRex was significantly increased in group II compared with group I (6 ± 7 vs 9 ± 6 μmol/L; P = .013). Furthermore, falls in ΔHbDex were more pronounced in group II (7 ± 16 vs -7 ± 16 μmol/L; P = .001). A statistically significant correlation was found between C of CEAP and the VCSS (r = 0.778; P < .001). Moreover, NIRS-derived TO2Hbst (r = -0.312; P < .01) and ΔHbDex (r = -0.332; P < .01) showed moderate inverse correlations with C of CEAP. Similarly, NIRS-derived ΔHbDex (r = -0.501; P < .001) had a strong inverse correlation, and ΔHbDst (r = -0.383; P < .001) and TO2Hbst (r = -0.378; P < .001) had moderate inverse correlations with VCSS.

CONCLUSIONS

Changes in O2Hb and HHb concentrations differ according to CEAP manifestation and VCSS. These data offer new insights into calf muscle hemodynamics at the microcirculation level in patients with PVI.

Changes in calf muscle deoxygenation after foam sclerotherapy in patients with superficial venous insufficiency

OBJECTIVE

This study assessed changes in the calf muscle deoxygenated hemoglobin (HHb) level during light-intensity exercise after ultrasound-guided foam sclerotherapy (UGFS) for superficial venous insufficiency.

METHODS

UGFS with 1% or 3% polidocanol foam (POL-F) was used to treat unilateral great saphenous vein reflux in 84 patients. Near-infrared spectroscopy (NIRS) was used to measure calf muscle HHb levels before and 3 months after UGFS. The calf venous HHb blood-filling index was calculated on standing, the calf venous HHb ejection index was obtained after one tiptoe movement, and the venous HHb retention index was obtained after 10 tiptoe movements. The primary end point was an evident improvement in calf muscle deoxygenation after UGFS. The secondary end point was obliteration of the great saphenous vein.

RESULTS

Treatment consisted of 1% POL-F in 48 limbs and 3% POL-F in the remaining 36. Ultrasound imaging at the 3-month follow-up demonstrated complete occlusion in 56.3% of the patients who received injections of 1% POL-F and in 66.7% of those who received injections of 3% POL-F. The difference in treatment outcome between the groups was not significant (P=.333). Reflux was absent in 39 limbs (81.3%) treated with 1% POL-F and in 34 limbs (94.4%) treated with 3% POL-F, and no significant difference was observed between the two groups (P=.076). Postsclerotherapy NIRS demonstrated significant reductions in the levels of the HHb filling index in both treatment groups (P=.039, P=.0001, respectively) and significant reductions in the levels of the HHb retention index (P<.0001, P=.008, respectively). However, the differences in the levels of the HHb ejection index before and after UGFS were not significant (P=.250, P=.084, respectively).

CONCLUSIONS

Our present findings suggest that changes in the values of these parameters may be of potential use for assessing the effects of foam sclerotherapy in patients with superficial venous insufficiency.

Factors predicting development of post-thrombotic syndrome in patients with a first episode of deep vein thrombosis: preliminary report

OBJECTIVE

To investigate the indicative parameters reflecting the progression of post-thrombotic syndrome (PTS) in patients with a first episode of deep vein thrombosis (DVT).

DESIGN AND METHODS

The patients' initial risk factors were assessed at presentation. Venous occlusion, and reflux and reflux parameters were evaluated at 6 months using venous duplex scanning. Near-infrared spectroscopy (NIRS) was also used to measure calf muscle deoxygenated haemoglobin levels at 6 months. Clinical manifestations were categorised using the clinical, etiologic, anatomic and pathophysiologic (CEAP) classification for chronic venous insufficiency (CVI), and the patients were divided into those having no PTS (C(0-3S),E(s),A(s,d,p),P(r,o)) and those having PTS (C(4-6S),E(s),A(s,d,p),P(r,o)).

RESULTS

Of the 121 patients evaluated, 25 (21%) developed PTS with a mean follow-up period of 66 months. At initial presentation, ilio-femoral DVT (odds ratio (OR) 3.4, 95% confidence interval (CI) 1.4-8.6) was associated with development of PTS. At 6 months, venous occlusion combined with reflux (OR 4.4, 95% CI 2.9-20.7), peak reflux velocity >29.7 cm s(-1) (OR 13.7, 95% CI 4.1-45.7) and mean reflux velocity >8.6 cm s(-1) (OR 4.4, 95% CI 1.5-12.9) in the popliteal vein detected by duplex scanning were strong predictors of PTS. NIRS-derived retention index >3.5 was the strongest predictor of PTS at 6 months (OR 67.4, 95% CI 14.3-318.1).

CONCLUSIONS

Ilio-femoral DVT is associated with the development of PTS at initial presentation. By contrast, occlusion and reflux, high reflux velocity in the popliteal vein and increased NIRS-derived retention index are important time-course predictors of PTS progression.

Prognostic impact of calf muscle near-infrared spectroscopy in patients with a first episode of deep vein thrombosis

BACKGROUND

The risk factors that affect the development of post-thrombotic syndrome (PTS) are not fully recognized, and it is difficult to reliably predict which patients are likely to develop PTS in acute phase of deep vein thrombosis (DVT).

AIMS

To investigate changes in calf muscle deoxygenated hemoglobin (HHb) levels after DVT, and to determine the indicative parameters reflecting the progression of PTS.

METHODS

Seventy-six consecutive patients with a first episode of unilateral DVT were prospectively enrolled. Clinical manifestations were categorized according to the CEAP (Clinical, Etiologic, Anatomical, and Pathophysiologic) classification, and the patients were divided into no-PTS (C(0-3)E(s),A(s,d,p),P(r,o)) and PTS (C(4-6)E(s),A(s,d,p),P(r,o)) groups. Near-infrared spectroscopy (NIRS) was used to measure calf muscle HHb levels at 6 months after diagnosis of DVT. The calf venous blood filling index (HHbFI) was calculated on standing, and the venous ejection index and the venous retention index (HHbRI) were then obtained after exercise. All patients were followed up for more than 24 months after the diagnosis of DVT.

RESULTS

Of 76 patients evaluated, 20 (26.3%) had PTS. The NIRS-derived HHbFI and HHbRI were significantly increased in patients who developed PTS in comparison with those who did not (P = 0.04 and P = 0.0001, respectively). HHbRI was significantly increased in patients with iliofemoral DVT in comparison with patients with calf DVT (P = 0.041). An optimal cut-off point of 2.9 for HHbRI showed the strongest ability to predict the development of PTS, with a sensitivity of 100% and a specificity of 82.1%.

CONCLUSIONS

HHbRI as measured by NIRS is significantly increased in patients with iliofemoral DVT as compared with those with calf DVT. Furthermore, HHbRI > 2.9 is a strong predictor of the development of PTS at 6 months.

Near-infrared spectroscopy/imaging for monitoring muscle oxygenation and oxidative metabolism in healthy and diseased humans

Near-infrared spectroscopy (NIRS) was initiated in 1977 by Jobsis as a simple, noninvasive method for measuring the presence of oxygen in muscle and other tissues in vivo. This review honoring Jobsis highlights the progress that has been made in developing and adapting NIRS and NIR imaging (NIRI) technologies for evaluating skeletal muscle O(2) dynamics and oxidative energy metabolism. Development of NIRS/NIRI technologies has included novel approaches to quantification of the signal, as well as the addition of multiple source detector pairs for imaging. Adaptation of NIRS technology has focused on the validity and reliability of NIRS measurements. NIRS measurements have been extended to resting, ischemic, localized exercise, and whole body exercise conditions. In addition, NIRS technology has been applied to the study of a number of chronic health conditions, including patients with chronic heart failure, peripheral vascular disease, chronic obstructive pulmonary disease, varying muscle diseases, spinal cord injury, and renal failure. As NIRS technology continues to evolve, the study of skeletal muscle function with NIRS first illuminated by Jobsis continues to be bright.

Uses of different D-dimer levels can reduce the need for venous duplex scanning to rule out deep vein thrombosis in patients with symptomatic pulmonary embolism

OBJECTIVE

This study investigated the prevalence and distribution of deep vein thrombosis (DVT) in patients with symptomatic pulmonary embolism (PE) to establish a screening protocol to reduce unnecessary venous duplex scanning using different D-dimer level rather than single cutoff point of 0.5 microg/mL in patients with low and moderate pretest clinical probability (PTP).

METHODS

The PTP score and D-dimer testing were used to evaluate 85 consecutive patients with symptomatically proven PE before venous duplex scanning. After calculating the PTP score, patients were divided into low (<or=0 points), moderate (1 to 2 points), and high (>or=3 points) PTP groups. The receiver operating characteristic (ROC) curves analysis was used to determine the appropriate D-dimer cutoff point in low and moderate PTP, with a negative predictive value of >98%.

RESULTS

The study enrolled 81 patients. The prevalence of DVT was 63%, with 27 patients (33%) classified as low, 38 (47%) as moderate, and 16 (20%) as high PTP. DVT was detected in nine patients (33%) in the low PTP group, in 27 (71%) in the moderate group, and in 15 (94%) in the high group. In the low PTP patients, the difference in the value of D-dimer assay between positive-scan and negative-scan patients was statistically significant (9.99 +/- 7.33 vs 3.46 +/- 4.20, respectively; P = .008). Conversely, no significant difference in the D-dimer assay value between positive and negative scan results was found in the moderate PTP patients. ROC curves analysis were used to select D-dimer cutoff points of 2.0 microg/mL for the low PTP group and 0.7 microg/mL for the moderate PTP groups. For both groups, D-dimer testing provided 100% sensitivity and 100% negative predictive value in the diagnosis of DVT. In the low PTP group, specificity increased from 33% to 67% (P = .046). In the moderate PTP group, however, the determined D-dimer level did not improve the specificity. Overall, venous duplex scanning could have been reduced by 17% (14/81) by using different D-dimer cutoff points.

CONCLUSIONS

A combination of specific D-dimer level and clinical probability score is most effective in the low PTP patients in excluding DVT. In the moderate PTP group, however, the recommended cutoff point of 0.5 microg/mL may be preferable. These results show that a different D-dimer level is more useful than single cutoff point of 0.5 microg/mL in excluding DVT in established PE patients.