Standardization in Quantitative Imaging: A Multicenter Comparison of Radiomic Features from Different Software Packages on Digital Reference Objects and Patient Data Sets

Radiomic features are being increasingly studied for clinical applications. We aimed to assess the agreement among radiomic features when computed by several groups by using different software packages under very tightly controlled conditions, which included standardized feature definitions and common image data sets. Ten sites (9 from the NCI's Quantitative Imaging Network] positron emission tomography–computed tomography working group plus one site from outside that group) participated in this project. Nine common quantitative imaging features were selected for comparison including features that describe morphology, intensity, shape, and texture. The common image data sets were: three 3D digital reference objects (DROs) and 10 patient image scans from the Lung Image Database Consortium data set using a specific lesion in each scan. Each object (DRO or lesion) was accompanied by an already-defined volume of interest, from which the features were calculated. Feature values for each object (DRO or lesion) were reported. The coefficient of variation (CV), expressed as a percentage, was calculated across software packages for each feature on each object. Thirteen sets of results were obtained for the DROs and patient data sets. Five of the 9 features showed excellent agreement with CV < 1%; 1 feature had moderate agreement (CV < 10%), and 3 features had larger variations (CV ≥ 10%) even after attempts at harmonization of feature calculations. This work highlights the value of feature definition standardization as well as the need to further clarify definitions for some features.

Multisite Concordance of DSC-MRI Analysis for Brain Tumors: Results of a National Cancer Institute Quantitative Imaging Network Collaborative Project

BACKGROUND AND PURPOSE

Standard assessment criteria for brain tumors that only include anatomic imaging continue to be insufficient. While numerous studies have demonstrated the value of DSC-MR imaging perfusion metrics for this purpose, they have not been incorporated due to a lack of confidence in the consistency of DSC-MR imaging metrics across sites and platforms. This study addresses this limitation with a comparison of multisite/multiplatform analyses of shared DSC-MR imaging datasets of patients with brain tumors.

MATERIALS AND METHODS

DSC-MR imaging data were collected after a preload and during a bolus injection of gadolinium contrast agent using a gradient recalled-echo-EPI sequence (TE/TR = 30/1200 ms; flip angle = 72°). Forty-nine low-grade (n = 13) and high-grade (n = 36) glioma datasets were uploaded to The Cancer Imaging Archive. Datasets included a predetermined arterial input function, enhancing tumor ROIs, and ROIs necessary to create normalized relative CBV and CBF maps. Seven sites computed 20 different perfusion metrics. Pair-wise agreement among sites was assessed with the Lin concordance correlation coefficient. Distinction of low- from high-grade tumors was evaluated with the Wilcoxon rank sum test followed by receiver operating characteristic analysis to identify the optimal thresholds based on sensitivity and specificity.

RESULTS

For normalized relative CBV and normalized CBF, 93% and 94% of entries showed good or excellent cross-site agreement (0.8 ≤ Lin concordance correlation coefficient ≤ 1.0). All metrics could distinguish low- from high-grade tumors. Optimum thresholds were determined for pooled data (normalized relative CBV = 1.4, sensitivity/specificity = 90%:77%; normalized CBF = 1.58, sensitivity/specificity = 86%:77%).

CONCLUSIONS

By means of DSC-MR imaging data obtained after a preload of contrast agent, substantial consistency resulted across sites for brain tumor perfusion metrics with a common threshold discoverable for distinguishing low- from high-grade tumors.

Abstract P4-02-05: Test-retest fidelity of FDG SUVmax in bone and non-boney metastatic breast cancer lesions in local area network PET/CT scanners

Background: Metabolic activity in lesions, measured by FDG-PET, is often used for assessing tumor aggressiveness and response to therapy. Patients may be scanned on different machines, so quantitative measurements should be reproducible. Reducing SUV variability in PET machines throughout a local network can aid in monitoring patient response to therapy and increase access to clinical trials.

Methods: Eighteen female patients with advanced or metastatic breast cancer underwent paired FDG PET/CT test-retest studies with 1-15 days between scans, and without interim change in treatment. Ten patients were studied in the same scanner and 8 patients were studied in 2 different scanners. Five different PET/CT scanners were used (2 GE DSTE, 2 Siemens (BioGraph 6 and mCT), 1 Philips Ingenuity TF). Each PET/CT scanner was calibrated using NIST-traceable reference sources to characterize and reduce variability. All of the images were interpreted by two separate reviewers. SUVmax values in lesions, corresponding normal tissue, and normal liver were collected. Linear mixed models with random intercept (patient effects) were fitted to compare differences in log(|SUVmax % difference|+.01) in multiple lesions per patient.

Results: SUVmax was assessed in a total of 130 lesions (75 bone). The median number of lesions per patient was 5 (range 1-17). Average SUVmax ranged from 1.0 to 18.2 (mean±SD = 6.0±3.2). The median SUVmax difference was 0.4 (8%) for 47 lesions imaged twice in the same scanner, and was 0.6 (13%) for 83 lesions imaged in two different scanners. In a multivariable linear mixed effects model, SUVmax for different scanners within the same institution did not differ more than for the same scanner (p=0.39), but repeat scans with different scanners and site personnel at had an average of 78% greater percentage difference in SUVmax than for the same scanner (p=0.009). In the same model, the average percent difference in SUVmax for bone lesions was estimated as 30% lower than for other sites (p=0.06, 95% confidence interval 0-50%). Examining normal liver uptake, the median SUVmean was 2.5 (range 1.9-3.1) with an median 6.5% difference between measurements (range 1.1%-23.7%) that did not appear to differ based on scanners used for repeat measurements (p=0.47).

Conclusions: The variability in quantitative FDG SUVmax between scans is modest, suggesting reliable reproducibility in appropriately calibrated settings. In our study, bone lesions had somewhat higher fidelity than other tumor sites. Additional studies will address variability in other cancer types. Careful calibration and monitoring of PET/CT scanners, and consistent imaging protocols are necessary in clinical trials that utilize quantitative PET/CT imaging in order to confidently interpret results.

Research Support: NIH grant U01-CA148131 and NCI-SAIC Contract 24XS036-004.

Citation Format: Linden HM, Peterson LM, Kurland B, Roberts T, Specht J, Shields AT, Novakova A, Christopfel R, Byrd D, Muzi M, Mankoff DA, Kinahan P. Test-retest fidelity of FDG SUVmax in bone and non-boney metastatic breast cancer lesions in local area network PET/CT scanners [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-02-05.

Applications of PET imaging with the proliferation marker [18F]-FLT

[18F]-3'-fluoro-3'-deoxythymidine (FLT) is a nucleoside-analog imaging agent for quantifying cellular proliferation that was first reported in 1998. It accumulates during the S-phase of the cell cycle through the action of cytosolic thymidine kinase, TK1. Since TK1 is primarily expressed in dividing cells, FLT uptake is essentially limited to dividing cells. Thus FLT is an effective measure of cell proliferation. FLT uptake has been shown to correlate with the more classic proliferation marker, the monoclonal antibody to Ki-67. Increased cellular proliferation is known to correlate with worse outcome in many cancers. However, the Ki-67 binding assay is performed on a sampled preparation, ex vivo, whereas FLT can be quantitatively measured in vivo using positron emission tomography (PET). FLT is an effective and quantitative marker of cell proliferation, and therefore a useful prognostic predictor in the setting of neoplastic disease. This review summarizes clinical studies from 2011 forward that used FLT-PET to assess tumor response to therapy. The paper focuses on our recommendations for a standardized clinical trial protocol and components of a report so multi center studies can be effectively conducted, and different studies can be compared. For example, since FLT is glucuronidated by the liver, and the metabolite is not transported into the cell, the plasma fraction of FLT can be significantly changed by treatment with particular drugs that deplete this enzyme, including some chemotherapy agents and pain medications. Therefore, the plasma level of metabolites should be measured to assure FLT uptake kinetics can be accurately calculated. This is important because the flux constant (KFLT) is a more accurate measure of proliferation and, by inference, a better discriminator of tumor recurrence than standardized uptake value (SUVFLT). This will allow FLT imaging to be a specific and clinically relevant prognostic predictor in the treatment of neoplastic disease.

Efficacy and tolerability of fitostimoline (vaginal cream, ovules, and vaginal washing) and of benzydamine hydrochloride (tantum rosa vaginal cream and vaginal washing) in the topical treatment of symptoms of bacterial vaginosis

Two hundred and 91 patients showing signs and symptoms of bacterial vaginosis (BV) were randomized to receive topical treatment with Fitostimoline (vaginal cream and vaginal ovules + vaginal washing) or benzydamine hydrochloride (vaginal cream + vaginal washing) for 7 days. Signs (leucorrhoea, erythema, oedema, and erosion) and symptoms (burning, pain, itching, vaginal dryness, dyspareunia, and dysuria) (scored 0–3) were evaluated at baseline and at the end of treatment; the total symptoms score (TSS) was also calculated. In 125 patients, a bacterial vaginosis was confirmed by vaginal swab test. The primary efficacy variable analysis, that is, the percentage of patients with therapeutic success (almost complete disappearance of signs and symptoms), demonstrated that Fitostimoline ovules and vaginal cream were therapeutically equivalent and that pooled Fitostimoline treatment was not inferior to benzydamine hydrochloride. All the treatments were well tolerated, with only minor local adverse events infrequently reported. The results of this study confirmed that gynaecological Fitostimoline is a safe and effective topical treatment for BV.

Kinetic quantitation of cerebral PET-FDG studies without concurrent blood sampling: statistical recovery of the arterial input function

Kinetic quantitation of dynamic positron emission tomography (PET) studies via compartmental modeling usually requires the time-course of the radio-tracer concentration in the arterial blood as an arterial input function (AIF). For human and animal imaging applications, significant practical difficulties are associated with direct arterial sampling and as a result there is substantial interest in alternative methods that require no blood sampling at the time of the study. A fixed population template input function derived from prior experience with directly sampled arterial curves is one possibility. Image-based extraction, including requisite adjustment for spillover and recovery, is another approach. The present work considers a hybrid statistical approach based on a penalty formulation in which the information derived from a priori studies is combined in a Bayesian manner with information contained in the sampled image data in order to obtain an input function estimate. The absolute scaling of the input is achieved by an empirical calibration equation involving the injected dose together with the subject's weight, height and gender. The technique is illustrated in the context of (18)F -Fluorodeoxyglucose (FDG) PET studies in humans. A collection of 79 arterially sampled FDG blood curves are used as a basis for a priori characterization of input function variability, including scaling characteristics. Data from a series of 12 dynamic cerebral FDG PET studies in normal subjects are used to evaluate the performance of the penalty-based AIF estimation technique. The focus of evaluations is on quantitation of FDG kinetics over a set of 10 regional brain structures. As well as the new method, a fixed population template AIF and a direct AIF estimate based on segmentation are also considered. Kinetics analyses resulting from these three AIFs are compared with those resulting from radially sampled AIFs. The proposed penalty-based AIF extraction method is found to achieve significant improvements over the fixed template and the segmentation methods. As well as achieving acceptable kinetic parameter accuracy, the quality of fit of the region of interest (ROI) time-course data based on the extracted AIF, matches results based on arterially sampled AIFs. In comparison, significant deviation in the estimation of FDG flux and degradation in ROI data fit are found with the template and segmentation methods. The proposed AIF extraction method is recommended for practical use.

Positron emission tomography imaging of tissue P-glycoprotein activity during pregnancy in the non-human primate

BACKGROUND AND PURPOSE

Changes in tissue P-glycoprotein (P-gp) activity during pregnancy could affect the pharmacokinetics and thus the efficacy and toxicity of many drugs. Therefore, using positron emission tomography (PET) imaging, we tested whether gestational age affects tissue P-gp activity in the pregnant non-human primate, Macaca nemestrina.

EXPERIMENTAL APPROACH

Mid-gestational (day 75 +/- 13, n= 7) and late-gestational (day 150 +/- 10, n= 5) age macaques were imaged after administration of a prototypic P-gp substrate, (11)C-verapamil (13.7-75.4 MBq.kg(-1)), before and during intravenous infusion of a P-gp inhibitor, cyclosporin A (CsA) (12 or 24 mg.kg(-1).h(-1)). Accumulation of radioactivity in the fetal liver served as a reporter of placental P-gp activity. P-gp activity was expressed as CsA-induced percent change in the ratio of the area (0-9 min) under the (11)C-radioactivity concentration-time curve in the tissue (AUC(tissue)) to that in the maternal plasma (AUC(plasma)).

KEY RESULTS

The CsA-induced change in AUC(fetal liver)/AUC(maternal)(plasma) of (11)C-radioactivity significantly increased from mid- (35 +/- 25%) to late gestation (125 +/- 66%). Likewise, the CsA-induced change in AUC(maternal brain)/AUC(plasma) increased from mid- (172 +/- 80%) to late gestation (337 +/- 148%). The AUC ratio for the other maternal tissues was not significantly affected. Neither the CsA blood concentrations nor the level of circulating (11)C-verapamil metabolites were significantly affected by gestational age.

CONCLUSIONS AND IMPLICATIONS

P-gp activity at the blood-brain barrier and the placental barrier in the macaque increased with gestational age. If replicated in humans, the exposure of the fetus and maternal brain to P-gp substrate drugs, and therefore their efficacy and toxicity, will change during pregnancy.

Hypoxia imaging-directed radiation treatment planning

Increasing evidence supports the role of the tumor microenvironment in modulating cancer behavior. Tissue hypoxia, an important and common condition affecting the tumor microenvironment, is well established as a resistance factor in radiotherapy. Increasing evidence points to the ability of hypoxia to induce the expression of gene products, which confer aggressive tumor behavior and promote broad resistance to therapy. These factors suggest that determining the presence or absence of tumor hypoxia is important in planning cancer therapy. Recent advances in PET hypoxia imaging, conformal radiotherapy, and imaging-directed radiotherapy treatment planning now make it possible to perform hypoxia-directed radiotherapy. We review the biological aspects of tumor hypoxia and PET imaging approaches for measuring tumor hypoxia, along with methods for conformal radiotherapy and image-guided treatment, all of which provide the underpinnings for hypoxia-directed therapy. As a case example, we review emerging data on PET imaging of hypoxia to direct radiotherapy.

Molecular imaging of regional brain tumor biology

Energy metabolism measurements in gliomas in vivo are now performed widely with positron emission tomography (PET). This capability has developed from a large number of basic and clinical science investigations that have cross fertilized one another. This article presents several areas that exemplify questions that have been explored over the last two decades. While the application of PET with [(18)F]-2-fluoro-2-deoxyglucose (FDG-PET) has proven useful for grading and prognosis assessments, this approach is less clinically suitable for assessing response to therapy, even though results to date raise very intriguing biological questions. Integration of metabolic imaging results into glioma therapy protocols is a recent and only preliminarily tapped method that may prove useful in additional trials that target DNA or membrane biosynthesis, or resistance mechanisms such as hypoxia. There are exciting future directions for molecular imaging that will undoubtedly be fruitful to explore, especially apoptosis, angiogenesis and expression of mutations of genes, e.g., epidermal growth factor receptor, that promote or suppress cellular malignant behavior.

Correlation of Tc-99m-red blood cell phleboscintigraphy with clinical severity of chronic venous disease

Equilibrium red blood cell phleboscintigraphy of the lower limbs for the diagnostic management of chronic venous disease has been proposed. The aim of this study was to verify the correlation of the phleboscintigraphic assessment of chronic venous disease with the clinical grading of the severity of the disease, since other diagnostic modalities have been recently demonstrated a poor and only partial correlation. Equilibrium Tc-99m-red blood cell phleboscintigraphy was performed in 27 patients with chronic venous disease. Scintigraphic images of 52 limbs were classified according to a four-class qualitative grading of the severity of the venous disease, and a quantitative scintigraphic index (saphena /femoral ratio) was assigned to each limb. The scintigraphic qualitative grading showed a highly significant correlation with the clinical grading (Rs=0.82, p<0.01), a good interobserver and intraobserver agreement (86.5% and 92.3%, respectively) and more than 90% sensitivity and specificity to identify the categories "minimal or no chronic venous disease" or "more significant disease" (assessed according to the Bayes theorem). Sensitivity and specificity results for the quantitative assessment were not as good. Phleboscintigraphy correlates well with the clinical grading of the severity of chronic venous disease of the lower limbs and may have potential as a valuable diagnostic tool for the noninvasive assessment of chronic venous disease.

Kinetic characterization of hexokinase isoenzymes from glioma cells: implications for FDG imaging of human brain tumors

Quantitative imaging of glucose metabolism of human brain tumors with PET utilizes 2-[(18)F]-fluorodeoxy-D-glucose (FDG) and a conversion factor called the lumped constant (LC), which relates the metabolic rate of FDG to glucose. Since tumors have greater uptake of FDG than would be predicted by the metabolism of native glucose, the characteristic of tumors that governs the uptake of FDG must be part of the LC. The LC is chiefly determined by the phosphorylation ratio (PR), which is comprised of the kinetic parameters (Km and Vmax) of hexokinase (HK) for glucose as well as for FDG (LC proportional to (Km(glc) x Vmax(FDG))/(Km(FDG) x Vmax(glc)). The value of the LC has been estimated from imaging studies, but not validated in vitro from HK kinetic parameters. In this study we measured the kinetic constants of bovine and 36B-10 rat glioma HK I (predominant in normal brain) and 36B-10 glioma HK II (increased in brain tumors) for the hexose substrates glucose, 2-deoxy-D-glucose (2DG) and FDG. Our principal results show that the KmGlc < KmFDG << Km2DG and that PR2DG < PRFDG. The FDG LC calculated from our kinetic parameters for normal brain, possessing predominantly HK I, would be higher than the normal brain LC predicted from animal studies using 2DG or human PET studies using FDG or 2DG. These results also suggest that a shift from HK I to HK II, which has been observed to increase in brain tumors, would have little effect on the value of the tumor LC.

Determining hypoxic fraction in a rat glioma by uptake of radiolabeled fluoromisonidazole

The usefulness of radiolabeled nitroimidazoles for measuring hypoxia will be clarified by defining the relationship between tracer uptake and radiobiologically hypoxic fraction. We determined the radiobiologically hypoxic fraction from radiation response data in 36B10 rat gliomas using the paired cell survival curve technique and compared the values to the radiobiologically hypoxic fraction inferred from mathematical modeling of time-activity data acquired by PET imaging of [(18)F]FMISO uptake. Rats breathed either air or 10% oxygen during imaging, and timed blood samples were taken. The uptake of [(3)H]FMISO by 36B10 cells in vitro provided cellular binding characteristics of this radiopharmaceutical as a function of oxygen concentration. The radiobiologically hypoxic fraction determined for tumors in air-breathing rats using the paired survival curve technique was 6.1% (95% CL = 4.3- 8.6%), which agreed well with that determined by modeling FMISO time-activity data (7. 4%; 95% CL = 2.5-17.3%). These results are consistent with the agreement between the two techniques for measuring radiobiologically hypoxic fraction in Chinese hamster V79 cell spheroids. In contrast, the FMISO-derived radiobiologically hypoxic fraction in rats breathing 10% oxygen was 13.1% (95% CL 7.9-8.3%), much lower than the radiobiologically hypoxic fraction of 43% determined from the radiation response data. This discrepancy may be due to the failure of FMISO to identify hypoxic cells residing at or above an oxygen level of 2-3 mmHg that will still confer substantial protection against radiation. The presence of transiently hypoxic cells in rats breathing reduced oxygen may also be under-reported by nitroimidazole binding, which is strongly dependent on time and concentration.

Propofol, but not etomidate, reduces desflurane-mediated sympathetic activation in humans

PURPOSE

The administration of desflurane to humans can lead to substantial activation of the neurohumoral axis. Propofol can inhibit the sympathetic response to stress. This study compared the neurocirculatory effects of induction of anesthesia with propofol with those of etomidate on desflurane-mediated sympathetic activation.

METHODS

After informed consent, awake baseline recordings of heart rate (HR), mean arterial blood pressure (MAP), and efferent sympathetic nerve activity (SNA, peroneal nerve) were obtained from healthy volunteers randomly assigned to receive either 2.5 mg x kg(-1) propofol (n=8) or 0.3 mg x kg(-1) etomidate (n=7). Two minutes after i.v. induction, desflurane 3.6% was added to the inspired gas, and increased in consecutive minutes to 7% and 10.9%. Ventilation via mask was continued for an additional seven minutes. Normocarbia was maintained while neurocirculatory parameters were continuously recorded.

RESULTS

There were no differences between groups at baseline. The administration of desflurane via mask after etomidate led to increases in HR, MAP and SNA. Propofol significantly reduced the MAP response and delayed and attenuated the sympatho-excitation.

CONCLUSION

Propofol induction reduced the sympathetic activation and hypertension associated with desflurane.

Kinetic analysis of 2-[11C]thymidine PET imaging studies: validation studies

2-[11C]thymidine has been tested as a PET tracer of cellular proliferation. We have previously described a model of thymidine and labeled metabolite kinetics for use in quantifying the flux of thymidine into DNA as a measure of tumor proliferation. We describe here the results of studies to validate some of the model's assumptions and to test the model's ability to predict the time course of tracer incorporation into DNA in tumors.

METHODS

Three sets of studies were conducted: (a) The uptake of tracers in proliferative tissues of normal mice was measured early after injection to assess the relative delivery of thymidine and metabolites of thymidine catabolism (thymine and CO2) and calculate relative blood-tissue transfer rates (relative K1s). (b) By using sequential injections of [11C]thymidine and [11C]thymine in normal human volunteers, the kinetics of the first labeled metabolite were measured to determine whether it was trapped in proliferating tissue such as the bone marrow. (c) In a multitumor rat model, 2-[14C]thymidine injection, tumor sampling and quantitative DNA extraction were performed to measure the time course of label uptake into DNA for comparison with model predictions.

RESULTS

Studies in mice showed consistent relative delivery of thymidine and metabolites in somatic tissue but, as expected, showed reduced delivery of thymidine and thymine in the normal brain compared to CO2. Thymine studies in volunteers showed only minimal trapping of label in bone marrow in comparison to thymidine. This quantity of trapping could be explained by a small amount of fixation of labeled CO2 in tissue, a process that is included as part of the model. Uptake experiments in rats showed early incorporation of label into DNA, and the model was able to fit the time course of uptake.

CONCLUSION

These initial studies support the assumptions of the compartmental model and demonstrate its ability to quantify thymidine flux into DNA by using 2-[11C]thymidine and PET. Results suggest that further work will be necessary to investigate the effects of tumor heterogeneity and to compare PET measures of tumor proliferation to in vitro measures of proliferation and to clinical tumor behavior in patients undergoing therapy.

1-[Carbon-11]-glucose radiation dosimetry and distribution in human imaging studies

1-[Carbon-11]-D-glucose ([11C]-glucose) is an important imaging agent for PET studies that have been used to study the normal brain, encephalitis, epilepsy, manic-depressive disorder, schizophrenia and brain tumors.

METHODS

Dosimetry estimates were calculated in subjects undergoing imaging studies to help define the radiation risk of [11C]-glucose PET imaging. Time-dependent radioactivity concentrations in normal tissues in 33 subjects after intravenous injection of [11C]-glucose were obtained by PET imaging. Radiation absorbed doses were calculated according to the procedures of the Medical Internal Radiation Dose (MIRD) committee along with the variation in dose based on the calculated standard deviation of activity distribution seen in the individual patients.

RESULTS

Total body exposure was a median of 3.0 microGy/MBq in men and 3.8 microGy/MBq in women. The effective dose equivalent was 3.8 microGy/ MBq in men and 4.8 microGy/MBq in women. The critical organs were those that typically take up the most glucose (brain, heart wall and liver).

CONCLUSION

The organ doses reported here are small and comparable to those associated with other commonly performed nuclear medicine tests and indicate that potential radiation risks associated with this radiotracer are within generally accepted limits.

From Bassini to tension-free mesh hernia repair. Review of 1409 consecutive cases

The short and long-term results of traditional and tension-free inguinal hernia repairs have been assessed in three surgical units. In order to standardise the results, hernias were classified according with Nyhus. There were 109 type I, 311 type II, 854 type III, and 125 type IV hernias. Follow-up was possible in 1201 patients (1249 hernia repairs). Postoperative course, postoperative pain, and recurrences were analysed. Recurrences ranged from 0.7% up to 9.3%. The tension-free methods of repair provided the most important advantages in term of low recurrence rate and early return to work even if, in our series, recurrences resulted mainly related to the type of hernia than to the type of repair. The Authors conclude that any hernia repair should be sized to the type of hernia defect in order to avoid over-treatment and abusive placing of a foreign body such as polypropylene mesh.

Prevalence of thyroid cancer in hyperthyroid patients treated by surgery

A retrospective study has been carried out to evaluate the prevalence of malignant thyroid tumors in 202 patients submitted to surgery for hyperthyroidism. Thyroid cancer was diagnosed in 12 cases (5.9%); the final histologic examination revealed nine papillary carcinomas, one follicular carcinoma, and two Hürthle cell carcinomas. Concurrence of hyperthyroidism and thyroid cancer was more frequent in patients with single toxic adenomas than in those with toxic diffuse or multinodular goiters. In five cases thyroid malignancy was detected in the context of the hyperthyroid lesion (three toxic adenomas and two diffuse goiters). In eight patients the malignant lesion showed a maximum diameter of less than 1 cm, although in five of these cases unfavorable histologic features, such as minimal capsular invasion or multifocality, were present. All patients presenting with thyroid cancer are currently alive and apparently free of residual disease. It is concluded that hyperthyroid patients, particularly those with single toxic adenomas, should be carefully evaluated to exclude the presence of an associated malignancy and to plan the most appropriate therapeutic options.

Glucose metabolism in human malignant gliomas measured quantitatively with PET, 1-[C-11]glucose and FDG: analysis of the FDG lumped constant

Calculation of the glucose metabolic rate (MRGlc) in brain with PET and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) requires knowing the rate of uptake of FDG relative to glucose from plasma into metabolite pools in the tissue. The proportionality factor for this is the FDG lumped constant (LC[FDG]), the ratio of the volumes of distribution of FDG and glucose multiplied by the hexokinase phosphorylation ratio for the two hexoses, Km(Glc) x Vm(FDG)/Km(FDG) x Vm(Glc) x MRGlc equals the FDG metabolic rate (MRFDG) divided by the LC(FDG), i.e., MRGlc = MRFDG/LC(FDG) and LC(FDG) = MRFDG/MRGlc. This investigation tested the hypothesis that LC(FDG) is significantly higher in gliomas than it is in brain uninvolved with tumor.

METHODS

We imaged 40 patients with malignant gliomas with 1-[11C]glucose followed by FDG. The metabolic rates MRGlc and MRFDG were estimated for glioma and contralateral brain regions of interest by an optimization program based on three-compartment, four-rate constant models for the two hexoses.

RESULTS

The LC(FDG), estimated as MRFDG/MRGlc, in gliomas was 1.40 +/- 0.46 (mean +/- s.d.; range = 0.72-3.10), whereas in non-tumor-bearing contralateral brain, it was 0.86 +/- 0.14 (range = 0.61-1.21) (p < 0.001, glioma versus contralateral brain).

CONCLUSION

These data strongly suggest that the glioma LC(FDG) exceeds that of contralateral brain, that quantitation of the glioma MRGlc with FDG requires knowing the LC(FDG) specific for the glioma and that the LC(FDG) of normal brain is higher than previously reported estimates of about 0.50. 2-Fluoro-2-deoxy-D-glucose/PET studies in which glioma glucose metabolism is calculated by the autoradiographic approach with normal brain rate constants and LC(FDG) will overestimate glioma MRGlc, to the extent that the glioma LC(FDG) exceeds the normal brain LC(FDG). "Hot spots" visualized in FDG/PET studies of gliomas represent regions where MRGlc, LC(FDG) or their product is higher in glioma than it is in uninvolved brain tissue.

Myocardial ischemia and adverse cardiac outcomes in cardiac patients undergoing noncardiac surgery with sevoflurane and isoflurane. Sevoflurane Ischemia Study Group

Sevoflurane is associated with less tachycardia and coronary vasodilation than isoflurane and thus might be associated with less myocardial ischemia. This multicenter study examined the incidence of myocardial ischemia and adverse cardiac outcomes in adults (40-87 yr) with cardiac disease having elective noncardiac surgery. Patients were randomized to receive either sevoflurane (S) (n = 106) or isoflurane (I) (n = 108) in conjunction with sodium thiopental, vecuronium, fentanyl, and 50%-70% N2O. Intraoperative hemodynamics were maintained within 20% of awake baseline with standard drugs. A Holter monitor was applied 3-24 h before surgery and maintained until 48 h after surgery. Electrocardiograms and blood samples for analysis of the MB isoenzyme fraction of creatine phosphokinase were obtained preoperatively and daily for 48 h postoperatively. Anesthetic exposure (1.79 +/- 0.15 [mean +/- SE] minimum alveolar concentration-hour) and duration of surgery (219 +/- 13 min) did not differ between groups. The incidence of ischemia in the pre-, intra- and postoperative periods, adverse cardiac outcomes (18% occurrence), intraoperative hemodynamic variations (+/-20% change from ward baseline), and administration of adjunct cardiovascular medications were similar between groups. In cardiac patients having noncardiac surgery, sevoflurane was comparable to isoflurane with respect to the incidence of intra- and postoperative myocardial ischemia and in the frequency of adverse cardiac outcomes.

IMPLICATIONS

Surgical patients with heart disease are at risk of heart complications, some of which could be induced by an anesthetic. We compared the incidence of cardiac complications between patients receiving sevoflurane and isoflurane. We found that the frequency of additional heart problems in cardiac patients receiving sevoflurane was not different from that associated with isoflurane.

The effects of premedication on inhaled induction of anesthesia with sevoflurane

The effects of premedication with midazolam (M), fentanyl (F), or both (B) on induction of anesthesia via a mask with sevoflurane (S) were assessed in 24 healthy volunteers who participated on three occasions, receiving either intravenous (IV) F (2.4 microg/kg), M (36 microg/kg), or B (0.6 microg/kg F, 9 microg/kg M) 5 min before three vital capacity breaths of 8% S, 66% N2O, and O2. At loss of lid-lash reflex (LLR), ventilation was manually assisted until a randomly assigned time of administration was attained, at which time laryngoscopy and tracheal intubation were attempted. The effective times for 50% of subjects (ET50) to loss of LLR were 64 s for M and B and 54 s for F (P < 0.05). The ET50 to acceptable intubating conditions were 4.3, 3.1 and 2.5 min for F, M, and B, respectively. F resulted in more airway management difficulties than M or B. Heart rate was slightly increased before intubation in M. Heart rate increases after intubation were least in F, intermediate in B, and greatest in M. The time to achieve good intubating and airway conditions up to intubation was lowest with M or B. Anesthetic adjuvants did not improve the time to achieve loss of consciousness with anesthetic induction via the face mask with sevoflurane, but they significantly decreased the time to acceptable tracheal intubating conditions.

IMPLICATIONS

Adults can be anesthetized with very few side effects by breathing themselves to sleep with sevoflurane. Giving patients small doses of sedatives intravenously before they inhale an anesthetic can improve the speed and quality of the process of falling asleep.

Feasibility of imaging pentose cycle glucose metabolism in gliomas with PET: studies in rat brain tumor models

The feasibility of imaging pentose cycle (PC) glucose utilization in human gliomas with PET was explored in two rat glioma models by means of glucose radiolabeled in either the carbon-1 (C-1) or carbon-6 (C-6) position.

METHODS

In vitro, monolayers of T-36B-10 glioma, tissue slices of intracerebral glioma grafts or slices of normal brain were fed [1-14C]glucose or [6-14C]glucose, and the generated [14C]CO2 was trapped to quantitate the ratio of [14C]CO2 from 14C-1 versus 14C-6. In vivo, rats bearing grafts of either T-36B-10 or T-C6 rat gliomas at six subcutaneous sites received simultaneous intravenous injections of either [1-11C]glucose and [6-14C]glucose, or [1-14C]glucose and [6-11C]glucose. Tumors were excised between 5 and 55 min postinjection to quantify tracer uptake while arterial plasma was collected to derive time-activity input curves.

RESULTS

In vitro, the C-1/C-6 ratio for CO2 production from T-36B-10 monolayers was 8.8 +/- 0.4 (s.d.), in glioma slices it was 6.1 +/- 2.1 and in normal brain slices it was 1.1 +/- 0.7. PC metabolism in T-36B-10 was 1.8% +/- 0.5 of total glucose utilization. In vivo, tumor radioactivity levels normalized by plasma isotopic glucose levels showed that retained C-1 relative to C-6 radiolabeled glucose was significantly lower in both gliomas, 4.9% lower in T-36B-10 (p < 0.01) and 4.7% lower in T-C6 (p < 0.01). In an additional group of rats bearing T-36B-10 gliomas and exposed to 10 Gy of 137Cs irradiation 4 hr before isotope injection, the C-1 level was 5.6% lower than that for C-6 (p < 0.05). These results were analyzed with a model of glucose metabolism that simultaneously optimized parameters for C-1 and C-6 glucose kinetics by simulating the C-1 and C-6 tumor time-activity curves. The rate constant for loss of radiolabeled carbon from the tumors, k4, was higher for C-1 than for C-6 in all groups of rats (19% higher for T-36B-10 unirradiated, 32% for T-36B-10 irradiated and 32% for T-C6 unirradiated).

CONCLUSION

Mathematical modeling, Monte Carlo simulations and construction of receiver-operator-characteristic curves show that if human gliomas have a similar fractional use of the PC, it should be measurable with PET using sequential studies with [1-11C]glucose and [6-11C]glucose.

Radionuclide venography and the surgical treatment of chronic venous disease of the lower extremity

PURPOSE

The purpose of this study was to describe the use of radionuclide venography in detecting the site and the functional value of blood reflux through incompetent perforating veins of the leg of patients with chronic venous disease.

METHODS

In this study we evaluated the management of 29 patients (34 lower limbs) who were admitted with chronic venous disease of the lower limbs (in 7 with ulcers refractory to conservative management), surgically treated between 1991 and 1994 on the basis of physical examination and scintigraphic detection of pathological venous refluxes.

RESULTS

In 26/29 patients (31/34 legs = 91%) there was a good result with no recurrence and complete alleviation of symptoms. All the ulcers healed but in two cases recurred after 2 and 6 months respectively. Amelioration of leg tropism was achieved in all patients with a good "cosmetic" result in 27/34 legs (79%). A complete deconnection of the incompetent perforating veins was confirmed with radionuclide venography in 31/34 legs (91%).

CONCLUSIONS

The authors conclude that radionuclide venography is useful in the pre-operative evaluation of patients with chronic venous disease of lower extremity.

Mechanisms whereby propofol mediates peripheral vasodilation in humans. Sympathoinhibition or direct vascular relaxation?

BACKGROUND

Anesthetic induction and maintenance with propofol are associated with decreased blood pressure that is, in part, due to decreased peripheral resistance. Several possible mechanisms whereby propofol could reduce peripheral resistance include a direct action of propofol on vascular smooth muscle, an inhibition of sympathetic activity to the vasculature, or both. This study examined these two possibilities in humans by measuring the forearm vascular responses to infusions of propofol into the brachial artery (study 1) and by determining the forearm arterial and venous responses to systemic (intravenous) infusions of propofol after sympathetic denervation of the forearm by stellate blockade (study 2).

METHODS

Bilateral forearm venous occlusion plethysmography was used to examine forearm vascular resistance (FVR) and forearm vein compliance (FVC). Study 1 used infusion of intralipid (time control) and propofol at rates between 83 and 664 micrograms/min into the brachial artery of 11 conscious persons and compared responses to arterial infusions of sodium nitroprusside (SNP) at 0.3, 3.0, and 10 micrograms/min. Venous blood from the infusion arm was assayed for plasma propofol concentrations. In study 2, after left stellate block (12 ml 0.25% bupivacaine + 1% lidocaine), six participants were anesthetized and maintained with propofol infusions of 125 and 200 micrograms.kg-1.min-1. Simultaneous right forearm (unblocked) blood flow dynamics served as the time control. In three additional conscious participants, intrabrachial artery infusions of SNP and nitroglycerin, both at 10 micrograms/min, were performed before and after stellate blockade of the left forearm to determine whether the sympathetically denervated forearm vessels could dilate beyond the level produced by denervation alone.

RESULTS

In study 1, infusion of intralipid or propofol into the brachial artery did not change FVR or FVC. Sodium nitroprusside significantly decreased FVR in a dose-dependent manner by 22 +/- 5%, 65 +/- 3%, and 78 +/- 2% (mean +/- SEM) but did not change FVC. During the incremental propofol infusions, plasma propofol concentrations increased from 0.2 to 10.1 micrograms/ml and averaged 7.4 +/- 1.1 micrograms/ml during the highest infusion rate. In study 2, stellate ganglion blockade decreased FVR by 50 +/- 6% and increased FVC by 58 +/- 10%. Propofol anesthesia at 125 and 200 micrograms.kg-1.min-1 progressively reduced mean arterial pressure. In the arm with sympathetic denervation, FVR and FVC showed no further changes during propofol anesthesia, whereas in the control arm FVR significantly decreased by 41 +/- 9% and 42 +/- 7%, and FVC increased significantly by 89 +/- 27% and 85 +/- 32% during 125 and 200 micrograms.kg-1.min-1 infusions of propofol, respectively. In the three additional conscious participants, intraarterial infusion of SNP and nitroglycerin (TNG) after the stellate blockade resulted in a further decrease of FVR and a further increase of FVC.

CONCLUSIONS

In contrast to SNP infusions, propofol infusions into the brachial artery of conscious persons caused no significant vascular responses, despite the presence of therapeutic plasma concentrations of propofol within the forearm. The effects of propofol anesthesia on FVR and FVC are similar to the effects of sympathetic denervation by stellate ganglion blockade. Thus the peripheral vascular actions of propofol appear to be due primarily to an inhibition of sympathetic vasoconstrictor nerve activity.

Site(s) mediating sympathetic activation with desflurane

BACKGROUND

Three strategies were employed to better define the afferent site(s) at which desflurane initiates its neurocirculatory activation.

METHODS

Young (aged 19-28 yr) healthy volunteers were employed in three separate studies. Monitoring included electrocardiography, radial artery blood pressure, and direct recordings of sympathetic outflow to skeletal muscle blood vessels by microneurography. In each study, anesthesia was established with 2.5 mg/kg propofol, and in studies 1 and 2 was maintained with 5.4% desflurane via a double-lumen tube. In study 1 (n = 7) a double-lumen tube was placed with the bronchial cuff just below the vocal cords to selectively give 14.5% desflurane or 2.4% isoflurane to the upper airway (via the tracheal lumen) or lower airway (via the bronchial lumen). Study 2 (n = 14) consisted of standard placement of a left side double-lumen tube to selectively increase the inspired desflurane concentration of either right or left lung to 11% while decreasing the inspired concentration in the opposite lung to 0%, thereby maintaining constant systemic concentrations of desflurane (gas chromatography). Study 3 consisted of lidocaine or placebo airway treatment before anesthetic induction and administration of 11% inspired desflurane by mask: group A-n = 9, topical and nebulized lidocaine, glossopharyngeal and superior laryngeal nerve blocks, and transtracheal administration of lidocaine; group B-n = 7, similar treatment as group A with placebo (saline); and group C-n = 8, systemic infusions of 2% lidocaine to match plasma concentrations of lidocaine in group A.

RESULTS

In study 1, significant increases in heart rate, mean arterial pressure, and sympathetic neural activity (26%, 23%, and 62%, respectively) occurred when desflurane was directed to the upper airway. These responses were approximately twofold to sixfold larger when desflurane was given to the lower airway (lungs). There were no significant increases in these variables when isoflurane was administered to the upper airways, and a significant increase in heart rate occurred only when isoflurane was delivered to the lower airways. In study 2, separate right or left lung increases in desflurane did not change the blood concentration of desflurane or sympathetic neural activity but led to significant increases in heart rate (44%) and mean arterial pressure (32%). The simultaneous administration of desflurane to both lungs increased the millimolar (mM) concentration of desflurane in the blood from 1.17 to 2.39 mM and led to increases in sympathetic neural activity (750%), heart rate (90%), and mean arterial pressure (63%). In study 3, neither regional nor systemic administration of lidocaine reduced the significant neurocirculatory activation caused by the rapid increase in the inspired concentration of desflurane by mask.

CONCLUSIONS

There are sites in the upper airway (larynx and above) that respond with sympathetic activation during rapid increases in desflurane concentration independent of systemic anesthetic changes. These responses, while lesser than those seen with rapid increases to the lung, may represent direct irritation of airway mucosa. Heart rate and mean arterial pressure responses to desflurane can be initiated by selectively increasing concentrations to either right or left lung without altering systemic levels of desflurane. From this it is inferred that there are sites within the lungs, separate from systemic sites, that mediate this response. Neither systemic lidocaine nor attempted blockade of upper airway sites with cranial nerve blocks combined with topical lidocaine was effective in attenuating the neurocirculatory activation associated with desflurane.

Induction of anesthesia and tracheal intubation with sevoflurane in adults

BACKGROUND

The speed, quality, and cost of mask induction of anesthesia and laryngeal mask airway insertion or tracheal intubation were studied in young non-premedicated volunteers given high inspired concentrations of sevoflurane (6 to 7%).

METHODS

Twenty healthy persons who were 19 to 32 years old participated three times, received 6 l/min fresh gas flow, and were randomized to receive 6 to 7% sevoflurane in 66% nitrous oxide/28% oxygen by face mask until tracheal intubation (treatment 1) or until laryngeal mask airway insertion (treatment 3), or 6 to 7% sevoflurane without nitrous oxide to tracheal intubation (treatment 2). Participants exhaled to residual volume and took three vital capacity breaths of the gas mixture; thereafter ventilation was manually assisted. The time of exposure to the inhaled gas was varied for consecutive participants. It was either increased or decreased by 30-sec increments based on the failure or success of the preceding volunteer's response to laryngoscopy and intubation after a preselected exposure time. Failure was defined as poor jaw relaxation, coughing or bucking, or inadequate vocal cord relaxation.

RESULTS

Loss of the lid-lash reflex in unpremedicated young volunteers was achieved in 1 min and did not differ among groups. Average time (and 95% confidence interval) for acceptable conditions for LMA insertion was achieved in 1.7 (0.7 to 2.7) min, and all participants had an immediate return of spontaneous ventilation. The time for acceptable tracheal intubating conditions after manual hyperventilation by mask was 4.7 (3.7 to 5.7) min and 6.4 (5.1 to 7.7) min in treatments 1 and 2, respectively. There were no cases of increased secretions or laryngospasm. The incidence of breath holding and expiratory stridor ("crowing") was 7.5% and 25%, respectively, during treatment 1 and 15% and 40%, respectively, during treatment 2.

CONCLUSIONS

The induction of anesthesia to loss of lid reflex in young non-premedicated adults approaches the speed of intravenous induction techniques. No untoward airway responses were noted during mask induction of anesthesia with a three-breath technique. In response to intubation, no adverse airway responses, including jaw tightness, laryngospasm, and excessive coughing or bucking, occurred in participants whose duration of mask administration of sevoflurane met the appropriate times (as determined in this study).

Comparison of sevoflurane/fentanyl and isoflurane/fentanyl during elective coronary artery bypass surgery. Sevoflurane Venture Group

PURPOSE

Due to the progressive aging of the surgical population, the proportion of patients with coronary artery disease (CAD) is likely to increase. The effects of the new inhalational anaesthetic sevoflurane must be determined in patients with known CAD.

METHODS

This multicentre, randomized, open-label study compared the haemodynamic and cardiovascular effects of sevoflurane and isoflurane with fentanyl in 284 ASA physical status II-IV patients undergoing elective coronary artery bypass graft (CABG).

RESULTS

Satisfactory records were available in 272 patients, 139 sevoflurane (Group S) and 133 isoflurane (Group I). There were no differences between groups for demographic data except that more patients in Group S were taking preoperative beta-blockers (P = 0.03). The mean end-tidal MAC and MAC.hr requirements between groups were not different (Group S received 0.63 +/- 0.02 MAC and 1.00 +/- 0.05 MAC. hr while Group I received 0.58 +/- 0.02 MAC and 0.92 +/- 0.05 MAC. hr P = NS). The preCPB use of intravenous fentanyl was not different between groups. There was a similar decrease in haemodynamic variables in both groups after induction that persisted throughout the preCPB period. The incidence of preCPB myocardial ischaemia, adverse haemodynamic events and use of vasoactive drugs did not differ between groups. The incidence of postoperative myocardial infarction was 2.2% for Group S and Group I was 4.5% (P = NS). There were five postoperative deaths, one of which was attributed to a cardiac cause (Group I).

CONCLUSION

In patients undergoing elective CABG with low risk factors, either sevoflurane or isoflurane, combined with fentanyl, provided an acceptable preCPB haemodynamic profile and cardiac outcomes.

Unilateral carotid sinus stimulation and muscle sympathetic nerve activity in man

The carotid baroreflex influences sympathetic outflow to the peripheral circulation, yet this net response is the result of information received from both right and left carotid sinuses. To assess their individual contributions on sympathetic activity, direct measurements of muscle sympathetic nerve activity (SNA) from the peroneal nerve of the right leg were made during unilateral carotid sinus stimulation. A sustained neck pressure (approximately 25 +/- 2 mm Hg) was applied to right and left carotid sinuses, as well as bilaterally, for 5 s in 10 healthy subjects using a customized neck collar device partitioned to allow for stimulation of only one side of the neck. In addition to muscle SNA, blood pressures (radial artery) and R-R interval (RRI) changes were recorded. Muscle SNA was greater for left side neck pressure with respect to burst amplitude (left = 4.07 +/- 0.67 vs right = 2.48 +/- 0.46 microV; P < 0.05), normalized burst amplitude (388 +/- 63 vs 269 +/- 37 units; P < 0.05), burst ratio (0.64 +/- 0.05 vs 0.46 +/- 0.04; P < 0.05), and a SNA index of normalized amplitude and ratio (24832 +/- 3455 vs 6566 +/- 3259 units; P < 0.05). The combined values of the muscle SNA index for right and left sides (25590 +/- 4531 units) did not differ from the bilateral value (21906 +/- 3855 units; P > 0.05). These findings suggest that afferent input from the left carotid sinus may have a greater influence on efferent muscle sympathetic outflow (as measured in the right leg) and that the bilateral response may represent the summed right and left carotid inputs.

[Assessment of the therapeutic effectiveness of alcohol administration in hepatocarcinoma: comparison of spiral computerized tomography and Doppler color ultrasonography]

PURPOSE

To investigate the comparative adequacy of spiral CT and color-Doppler US versus biopsy in assessing the efficacy of percutaneous ethanol injection (PEI) in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Fifteen patients with 30 known HCCs, 2-5 cm in diameter, underwent PEI. Arterial phase spiral CT and color-Doppler US were performed before treatment in all patients. Treatment efficacy was established on the basis of color-Doppler, spiral CT and percutaneous biopsy findings; biopsy was the gold standard.

RESULTS

After PEI, 22 of 30 lesions which were negative for malignant cells at biopsy were completely necrotic at spiral CT and avascular at color-Doppler US. In the extant 8 lesions, which exhibited residual tumor tissue at biopsy, spiral CT detected early enhancement of the viable tumor portion in all cases. Color-Doppler US showed residual tumor vascularization in 4 of 8 lesions.

CONCLUSIONS

Our results demonstrate that spiral CT, performed in the arterial phase, can improve the depiction of residual viable tumor tissue in HCCs treated with PEI, overcoming color-Doppler limitations.

The hemodynamic and renal effects of sevoflurane and isoflurane in patients with coronary artery disease and chronic hypertension. Sevoflurane Ischemia Study Group

In patients without significant cardiovascular disease, the hemodynamic effects of sevoflurane and isoflurane are similar; however, the hemodynamic effects of sevoflurane in patients with hypertension and ischemic heart disease are unknown. To examine the effects of sevoflurane in comparison to isoflurane in this high-risk population, 214 patients scheduled for elective surgery were enrolled if they had evidence of ischemic heart disease or multiple risk factors for ischemic heart disease. Patients were randomly assigned to receive sevoflurane (n = 106) or isoflurane (n = 108) for anesthetic maintenance in conjunction with fentanyl and nitrous oxide in oxygen. Deviations in arterial blood pressure or heart rate of more than 20% from preinduction values that persisted after adjustment of the volatile anesthetic concentration were treated with intravenous phenylephrine, ephedrine, nitroglycerin, atropine, or esmolol as needed. Creatinine, blood urea nitrogen (BUN), and urine protein were measured before surgery, immediately after surgery, and 24 and 48 h postoperatively. For analysis, patients were divided into those with and those without the diagnosis of chronic hypertension. Heart rate and arterial blood pressure responses to sevoflurane and isoflurane were not different for the patients with or without chronic hypertension. Neither anesthetic was associated with a more frequent treatment for hemodynamic deviation. After surgery, creatinine and BUN decreased in both the sevoflurane and isoflurane groups without significant differences between groups. The incidence of post-operative proteinuria was similar in the sevoflurane and isoflurane groups. We conclude that hemodynamic stability in patients with hypertension and ischemic heart disease is similar with sevoflurane and isoflurane. No differences in renal function were observed between the sevoflurane and isoflurane groups.

Desflurane-mediated neurocirculatory activation in humans. Effects of concentration and rate of change on responses

BACKGROUND

Rapid increases in the inspired concentration of desflurane have been associated with sympathetic activation, tachycardia, hypertension, and in select cases, myocardial ischemia. The current study examined the effects of the rate of change of the desflurane concentration on the sympathetic and hemodynamic responses to desflurane and sought to determine whether a finite concentration (end-tidal) of desflurane consistently initiated these responses.

METHODS

After Institutional Review Board approval, 23 healthy male volunteers were instrumented for electrocardiogram (heart rate (HR)), intraarterial blood pressure, and peroneal nerve microneurography (sympathetic nerve activity (SNA)). Subjects were given propofol (2.5 mg/kg) and vecuronium (0.15 mg/kg), and their lungs were mechanically ventilated for 30 min at a minimum alveolar concentration of 0.5 MAC with either desflurane or isoflurane (random assignment). The end-tidal concentration was increased at either 1% per min (n = 7) or 0.5% per min (n = 7) for desflurane or 0.16% per min (n = 9) for isoflurane (MAC-multiple comparable to 1% per min desflurane group) until 1.5 MAC was reached. HR, blood pressure, and SNA were averaged over 1-min segments from 0.5 to 1.5 MAC levels.

RESULTS

Awake neurocirculatory variables did not differ among the three groups. At 0.5 MAC, blood pressure had decreased (12-15%) and HR increased (12-20%) similarly in both groups. SNA decreased 77% in the isoflurane group but was not significantly changed in the desflurane groups. In the desflurane groups, the threshold (end-tidal concentration associated with a 10% increase in the measured variable) ranged between 4% and 10% for HR and between 4% and 7.7% for SNA. In the isoflurane group, the threshold occurred between 1.0% and 1.6% for HR and between 0.7% and 1.3% for SNA. The rate of change did not affect the threshold concentration or the peak HR increase in the desflurane groups. In contrast, SNA responses to desflurane were directly proportional to the rate of change.

CONCLUSION

There was no consistent threshold for the neurocirculatory activation associated with desflurane, and the HR and SNA thresholds generally were less than 1 MAC. The HR increase associated with desflurane was not rate- or concentration-dependent. In contrast, SNA responses were proportional to the rate of change and the concentration of desflurane.

Neurocirculatory responses to intubation with either an endotracheal tube or laryngeal mask airway in humans

STUDY OBJECTIVE

To compare the sympathetic and hemodynamic responses to intubation with either an endotracheal tube (ETT) or laryngeal mask airway (LMA).

DESIGN

Prospective, randomized, single-blinded study.

SETTING

The in vivo study was carried out in an experimental laboratory.

PATIENTS

16 healthy male consenting volunteers, ages 20 to 31 years, were studied.

INTERVENTIONS

After placement of a radial artery catheter, ECG electrodes, and a recording needle in the peroneal nerve, subjects were anesthetized with propofol 2.5 mg/kg, paralyzed with vecuronium 0.15 mg/kg, and ventilated via mask for 5 minutes with oxygen and 0.5 MAC desflurane or 0.5 MAC isoflurane. A LMA or ETT was inserted and neurocirculatory responses were continuously recorded.

MEASUREMENTS AND MAIN RESULTS

Measurements of heart rate (HR), mean arterial pressure (MAP), and sympathetic nerve activity (SNA) were made at preintubation baseline and at the peak response after airway manipulation. The time to recovery to 20% and 10% of baseline MAP and HR also was measured. Neurocirculatory variables did not differ in either the LMA (n = 7) or ETT (n = 9) groups immediately prior to intubation. The ETT group demonstrated a 27% HR increase and a 42% MAP increase compared with a 12% HR increase and a 23% MAP increase in the LMA group. Muscle SNA increased 600% in the ETT group versus 66% in the LMA group (p < 0.01). The time to return MAP and HR to 20% and 10% of perintubation baseline was significantly longer in the ETT than the LMA group (p < 0.01).

CONCLUSIONS

Because of the substantial reduction in the neurocirculatory responses to the LMA versus ETT, the LMA may prove advantageous in patients in whom HR and MAP increases may predispose to adverse cardiac or cerebrovascular events.

Alfentanil modifies the neurocirculatory responses to desflurane

Activation of the sympathetic nervous system occurs in response to desflurane, causing tachycardia and hypertension. Fentanyl partially blunts the hemodynamic effects of desflurane but fails to attenuate the sympathetic response. This study determined the clinical effectiveness and dose response of alfentanil on the neurocirculatory responses to desflurane. Twenty-five healthy, male volunteers were randomized into one of three groups to receive either placebo (n = 9), 10 micrograms/kg intravenous (IV) bolus alfentanil (n = 9), or 20 micrograms/kg IV bolus alfentanil (n = 7) in conjunction with anesthetic induction by propofol, 2.5 mg/kg. Mean arterial pressure (MAP, radial artery), heart rate (HR), and efferent muscle sympathetic nerve activity (SNA, peroneal nerve) were recorded. After conscious baseline measurements, anesthesia was induced by propofol and alfentanil/placebo. One minute later, the desflurane vaporizer was activated at 11%. Neurocirculatory measurements were recorded for 11 min. There were no differences between the groups at conscious baseline. Induction of anesthesia was associated with significantly decreased MAP in the placebo and the 10 micrograms/kg alfentanil groups and increased HR in all groups with little change in SNA. In placebo subjects, desflurane administration increased HR and MAP above baseline. In both alfentanil groups, during desflurane administration HR and MAP never increased significantly above baseline. However, SNA was significantly increased in both groups. Alfentanil effectively blunts the hemodynamic changes but not the sympathetic responses associated with rapid increases in the inspired concentration of desflurane.

Cardiovascular responses to sevoflurane: a review

In conclusion, sevoflurane appears to be similar to isoflurane and desflurane with a few exceptions. Sevoflurane was not associated with increases in heart rate in adult patients and volunteers, whereas higher MACs of isoflurane and desflurane and rapid increases in the inspired concentrations of these two anesthetics have been associated with tachycardia. Increasing concentrations of sevoflurane progressively decrease blood pressure in a manner similar to the other volatile anesthetics, and in unstimulated volunteers this decrease may be slightly less than with isoflurane at a higher MAC. Sevoflurane appears similar to isoflurane in its effect on regional blood flows, including the hepatic, renal, and cerebral circulation. In animals, sevoflurane appears to be a slightly less potent coronary vasodilator than isoflurane, and in a dog model, sevoflurane has not been associated with coronary flow redistribution ("steal"). Sevoflurane decreases myocardial contractility in a manner similar to equianesthetic concentrations of isoflurane and desflurane, and does not potentiate epinephrine-induced cardiac arrhythmias. Sevoflurane reduces baroreflex function in a manner similar to other volatile anesthetics. In several multicenter studies where patients with CAD or patients at high risk for CAD were randomized to receive either sevoflurane or isoflurane for cardiac or noncardiac surgery, the incidence of myocardial ischemia, infarction, and cardiac outcomes did not differ between treatment groups. Thus, sevoflurane has not been associated with untoward cardiovascular changes in volunteers and patients undergoing elective surgery compared with other volatile anesthetics, and it appears to offer a more stable heart rate profile than either isoflurane or desflurane.

Ruptured aneurysm of the superficial femoral artery

OBJECTIVE

True isolated "arteriosclerotic" aneurysms of the superficial femoral artery are rare. One case of isolated superficial femoral artery aneurysm and review of literature is reported.

DESIGN

Case report and review of the literature.

SETTING

Hospitalized care.

PATIENT

An 80-year old man presenting with rupture of superficial femoral artery aneurysm was observed and treated with graft interposition, which resulted in limb salvage.

INTERVENTION

Removal of the aneurysm and replacing of the arterial aneurysmatic segment by interposition of a polytetrafluoroethylene prosthetic graft.

MEASURES

Patency of the graft with no evidence of ischemic or embolic complication assessed with a follow-up period of 6 months.

RESULTS

From the review of the literature we collected 21 isolated true arteriosclerotic superficial femoral artery aneurysms in 17 patients. These aneurysms may be discovered after the onset of complications such as rupture (33%) or thrombosis and limb ischemia (19%). Other aneurysms are frequently concomitant (69%), mostly represented by abdominal aortic aneurysms (40%).

CONCLUSIONS

Ruptured arteriosclerotic aneurysm of the superficial femoral artery is very uncommon and the treatment of choice is based on replacing of the aneurysmal segment with a prosthetic graft interposition or proximal and distal artery ligation and bypass. Early diagnosis and surgical reconstruction is recommended for patients with aneurysms of the superficial femoral artery that are 2.5 cm or greater in maximum diameter and for complicated aneurysms of any size.

Neurocirculatory responses to sevoflurane in humans. A comparison to desflurane

BACKGROUND

Sevoflurane and desflurane are new volatile anesthetics with low blood solubilities that confer properties of rapid anesthetic induction and emergence. Desflurane has been associated with neurocirculatory excitation after the rapid increase in inspired concentrations. The current study evaluated and compared the sympathetic and hemodynamic responses associated with the administration of sevoflurane to those associated with administration of desflurane in humans.

METHODS

After Institutional Review Board approval, 21 healthy, young (19-32 yr) volunteers were randomly selected for participation. Arterial and central venous pressures were measured directly, and heart rate, forearm blood flow, and plasma norepinephrine concentrations were determined indirectly. Efferent muscle sympathetic nerve activity was recorded by microneurography. After neurocirculatory recordings at conscious baseline, measurements were repeated beginning 2 min after 2 mg/kg propofol while the anesthetic was increased incrementally by mask over a 10-min period at 1%, 2%, and 3% sevoflurane (n = 12) or 3%, 6%, and 9% desflurane (n = 9). Responses to intubation were recorded and, 20 min later, recordings were evaluated during steady-state periods of 0.41, 0.83, and 1.24 MAC. Data also were obtained after steady-state 0.83 MAC measurements when the inspired gas concentration was rapidly increased to either 3% sevoflurane or 9% desflurane ("transition" to 1.24 MAC).

RESULTS

Neurocirculatory variables did not differ between the two groups at conscious baseline. During the period of administration via mask and during the "transition" period, the significant increases in sympathetic nerve activity, heart rate, mean arterial pressure, and central venous pressure associated with desflurane were not observed with sevoflurane. Ten minutes after induction, mean arterial pressure and heart rate responses to intubation did not differ between groups. With increasing anesthetic concentration, there were progressive and similar decreases in mean arterial pressure in both groups and no changes in heart rate. Central venous pressure, sympathetic nerve activity, and plasma norepinephrine increased with the greater minimum alveolar concentration multiple of desflurane but not with that of sevoflurane.

CONCLUSIONS

The neurocirculatory excitation seen with rapid increases in desflurane did not occur with sevoflurane. At steady-state, increasing the concentration of sevoflurane was associated with lower sympathetic nerve activity and central venous pressure and similar mean arterial pressure and heart rate with that of desflurane.

The effects of clonidine on desflurane-mediated sympathoexcitation in humans

This study explored the effectiveness of oral clonidine premedication in attenuating sympathetic activation, tachycardia, and hypertension triggered by desflurane. After institutional review board approval, informed consent was obtained from 15 young, healthy male volunteers. Heart rate (HR, electrocardiogram), mean arterial pressure (MAP, radial artery catheter), and central venous pressure (CVP, jugular vein) were monitored. Recordings of sympathetic nerve activity (SNA) were obtained from the peroneal nerve via percutaneously placed tungsten needles. After baseline recordings, subjects were randomized to receive either a placebo (n = 10) or 0.3 mg of clonidine (n = 9) per os (PO). One hour later, repeat recordings were obtained. Propofol (2.5 mg/kg) and vecuronium (0.15 mg/kg) were given intravenously. Ventilation via a mask (100% O2) was used to maintain normocarbia. Two minutes after propofol administration, the desflurane vaporizer was set at 3.6% (0.5 minimum alveolar anesthetic concentration [MAC]) and increased at 1-min intervals to 7.2% and 11% (1.0 and 1.5 MAC). After 10 min, the trachea was intubated and 20 min later steady-state neurocirculatory recordings were obtained at 5.4%, during the first 5 min after advancing the vaporizer from 5.4% to 11% ("transition"), and at 11%. Resting HR, MAP, and SNA were similar between the two groups. PO clonidine reduced SNA, CVP, and MAP but did not change HR. In both groups propofol decreased SNA and MAP, and increased HR. The administration of desflurane via a mask resulted in significant increases in SNA, HR, and MAP. Clonidine reduced the HR and MAP responses by approximately 30%-40% during induction and transition periods.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of baroreflex sensitivity during isoflurane and desflurane anesthesia in humans

BACKGROUND

Desflurane anesthesia has been associated with heart rate (HR) and sympathetic nerve activity (SNA) responses that differ from those during isoflurane anesthesia. Whether these differences might be due to better preservation by desflurane of the baroreceptor reflex control of HR or SNA in humans was examined.

METHODS

Baroreflex sensitivity was assessed in 18 volunteers anesthetized with either desflurane or isoflurane. Measurements of HR, blood pressure (BP), and efferent SNA (percutaneous recordings from the peroneal nerve) were made, and baroreflex sensitivity was evaluated at conscious baseline and during 0.5, 1.0, and 1.5 MAC anesthesia. Baroreflex responses were triggered by bolus intravenous injections of nitroprusside (100 micrograms) and phenylephrine (150 micrograms). The linear portions of the baroreflex curves relating HR to mean arterial pressure and relating SNA to diastolic pressure were determined to obtain cardiac and sympathetic baroslopes, respectively.

RESULTS

Cardiac (HR) baroslopes were equally diminished at increasing MAC of both anesthetics. Sympathetic baroslopes were preserved at 0.5 MAC isoflurane but diminished at 0.5 MAC desflurane. Higher MAC produced equal depression of sympathetic baroslopes with both anesthetics.

CONCLUSIONS

Increasing MAC of desflurane and isoflurane anesthesia results in similar and progressive decreases in BP but dissimilar SNA and HR responses. These differences are not explained by disparate effects of these anesthetics on the baroreceptor reflex control of SNA or HR.

Effects of fentanyl on sympathetic activation associated with the administration of desflurane

BACKGROUND

Activation of the sympathetic nervous system occurs when desflurane is inspired shortly after anesthetic induction and when the inspired concentration of desflurane is rapidly increased during steady-state periods of anesthesia. The purpose of this study was to determine the effectiveness and dose response of fentanyl pretreatment in attenuating the neurocirculatory responses to desflurane in healthy human volunteers.

METHODS

After Institutional Research Review Board approval, three study groups were selected and, in random order, received either placebo (n = 10), a 2.5-micrograms.kg-1 intravenous bolus of fentanyl citrate followed by a continuous infusion of 1 microgram.kg-1.h-1 (n = 9), or a 5.0-micrograms.kg-1 intravenous bolus followed by an infusion of 2 micrograms.kg-1.h-1 (n = 11) before the administration of desflurane. Arterial (MAP) and central venous (CVP) pressures were measured directly, and heart rate (HR) was determined indirectly. Efferent muscle sympathetic nerve activity (SNA) was recorded from the peroneal nerve by microneurography. After neurocirculatory recordings at conscious unmedicated baseline and 12 min after fentanyl administration, anesthetic induction was carried out with 2.0 mg.kg-1 propofol and 0.2 mg.kg-1 vecuronium. Neurocirculatory measurements were repeated beginning 2 min after induction when desflurane was given via mask (semiclosed circle system, 61/min fresh gas flow, 100% O2) in three incremental 1-min steps (3.6%, 7.2%, and 11%). Intubation occurred 10 min after propofol administration. Twenty minutes after intubation, recordings were obtained during two steady-state periods during which end-tidal concentrations had achieved 5.4% (0.75 MAC) and 11% (1.5 MAC) desflurane for at least 10 min. Data also were obtained during the rapid increase in the inspired gas concentration from 5.4% to 11% ("transition").

RESULTS

Neurocirculatory variables did not differ between the three groups at conscious baseline, after fentanyl, and during steady-state periods of anesthesia. Propofol administration significantly reduced SNA and MAP. The MAP reduction was enhanced in the fentanyl-treated groups. After induction, the increases in SNA and MAP associated with the administration of desflurane by mask were not significantly reduced by fentanyl. The transition from 5.4% to 11% desflurane resulted in increases in SNA, HR, MAP, and fentanyl administration significantly attenuated the HR and MAP components. At the 11% steady-state measurement period, CVP was increased and MAP was decreased from conscious baseline, and these changes were not modified by fentanyl.

CONCLUSIONS

The administration of desflurane was associated with increases in SNA, HR, MAP, and CVP. Maximum sympathetic activation and hemodynamic responses occurred 4-5 min after initiating desflurane during induction and 2-3 min after increasing the inspired concentration of desflurane during the "transition" period. Although fentanyl partially attenuated the hemodynamic component in a dose-dependent fashion during the "transition" period, it did not significantly diminish the response during induction.

Color Doppler flow imaging of renal disease. Value of a new intravenous contrast agent: SH U 508 A (Levovist)

This study was aimed at assessing the diagnostic value of a new intravenous contrast agent SH U 508 A (Levovist) in improving color Doppler detection of renal mass vascularity. The study included 30 patients with renal masses: 22 adenocarcinomas, 1 sarcoma, 1 leiomyosarcoma, 1 urothelioma, 1 hemorrhagic cyst and 4 angiomyolipomas. The vascularization of the renal masses was investigated by means of color Doppler US, before and after the intravenous injection of SH U 508 A (Levovist), on the basis of blood flow patterns within and around the lesions. At precontrast scanning, low color Doppler signal at the periphery or within the lesions was observed in 13/30 patients only. After contrast administration, the signal-to-noise ratio increased, which allowed the visualization of tumor vessels in 26/30 patients. In 4/30 patients only no major enhancement of tumor vessels was observed. Our experience suggests that SH U 508 A (Levovist) improves color Doppler sensitivity in depicting the tumor vessels which were missed at baseline exams and in evaluating renal vein and inferior vena cava involvement.

[Reproducibility of Doppler ultrasonography in the study of hepatic blood flow]

The reproducibility of hepatic blood flow measurement with pulsed Doppler US was assessed in 6 healthy volunteers. All subjects underwent two different study sessions and were examined by three different operators after overnight fasting. Each operator was blind to his measurements. Hepatic arterial and portal venous blood flow and hepatic arterial maximum velocity were measured; resistive index (RI), pulsatility index (PI) and hepatic perfusion index (HPI) were calculated. Each measurement was repeated three times per session. The data from repeated measurements were analyzed with the analysis of variance (ANOVA) method to assess the intra- and intersubject variations for each variable. The Scheffe test was used to evaluate intra- and interobserver variations. Significant differences among the 6 examined subjects were found for all the variables measured, except for hepatic arterial maximum velocity. The same subject exhibited significant differences in mean velocity of the main portal vein trunk and of its right branch, in maximum hepatic arterial velocity, RI, portal vein section area and blood flow. No significant interobserver variation was observed in the same session and no intraobserver variation detected for all the measurements performed in different sessions. Thus, we conclude that pulsed Doppler US is a repeatable method for measuring hepatic blood flow and may therefore be useful to detect changes in hepatic perfusion.