Nam Sik Woo

Radiation Exposure of the Hand and Chest during C-arm Fluoroscopy-Guided Procedures

Background The C-arm fluoroscope is an essential tool for the intervention of pain. The aim of this study was to investigate the radiation exposure experienced by the hand and chest of pain physicians during C-arm fluoroscopy-guided procedures. Methods This is a prospective study about radiation exposure to physicians during transforaminal epidural steroid injection (TFESI) and medial branch block (MBB). Four pain physicians were involved in this study. Data about effective dose (ED) at each physicians right hand and left side of the chest, exposure time, radiation absorbed dose (RAD), and the distance from the center of the X-ray field to the physician during X-ray scanning were collected. Results Three hundred and fifteen cases were included for this study. Demographic data showed no significant differences among the physicians in the TFESIs and MBBs. In the TFESI group, there was a significant difference between the ED at the hand and chest in all the physicians. In physician A, B and C, the ED at the chest was more than the ED at the hand. The distance from the center of the X-ray field to physician A was more than that of the other physicians, and for the exposure time, the ED and RAD in physician A was less than that of the other physicians. In the MBB group, there was no difference in the ED at the hand and chest, except for physician D. The distance from the center of the X-ray field to physician A was more than that of the other physicians and the exposure time in physician A was less than that of the other physicians. Conclusions In conclusion, the distance from the radiation source, position of the hand, experience and technique can correlate with the radiation dose.

A Randomized Controlled Trial about the Levels of Radiation Exposure Depends on the Use of Collimation C-arm Fluoroscopic-guided Medial Branch Block

Background C-arm fluoroscope has been widely used to promote more effective pain management; however, unwanted radiation exposure for operators is inevitable. We prospectively investigated the differences in radiation exposure related to collimation in Medial Branch Block (MBB). Methods This study was a randomized controlled trial of 62 MBBs at L3, 4 and 5. After the patient was laid in the prone position on the operating table, MBB was conducted and only AP projections of the fluoroscope were used. Based on a concealed random number table, MBB was performed with (collimation group) and without (control group) collimation. The data on the patients age, height, gender, laterality (right/left), radiation absorbed dose (RAD), exposure time, distance from the center of the field to the operator, and effective dose (ED) at the side of the table and at the operators chest were collected. The brightness of the fluoroscopic image was evaluated with histogram in Photoshop. Results There were no significant differences in age, height, weight, male to female ratio, laterality, time, distance and brightness of fluoroscopic image. The area of the fluoroscopic image with collimation was 67% of the conventional image. The RAD (29.9 ± 13.0, P = 0.001) and the ED at the left chest of the operators (0.53 ± 0.71, P = 0.042) and beside the table (5.69 ± 4.6, P = 0.025) in collimation group were lower than that of the control group (44.6 ± 19.0, 0.97 ± 0.92, and 9.53 ± 8.16), resepectively. Conclusions Collimation reduced radiation exposure and maintained the image quality. Therefore, the proper use of collimation will be beneficial to both patients and operators.

Spectral entropy for assessing the depth of propofol sedation

Background For patients in the intensive care unit (ICU) or under monitored anesthetic care (MAC), the precise monitoring of sedation depth facilitates the optimization of dosage and prevents adverse complications from underor over-sedation. For this purpose, conventional subjective sedation scales, such as the Observers Assessment of Alertness/Sedation (OAA/S) or the Ramsay scale, have been widely utilized. Current procedures frequently disturb the patients comfort and compromise the already well-established sedation. Therefore, reliable objective sedation scales that do not cause disturbances would be beneficial. We aimed to determine whether spectral entropy can be used as a sedation monitor as well as determine its ability to discriminate all levels of propofol-induced sedation during gradual increments of propofol dosage. Methods In 25 healthy volunteers undergoing general anesthesia, the values of response entropy (RE) and state entropy (SE) corresponding to each OAA/S (5 to 1) were determined. The scores were then analyzed during each 0.5 mcg/ml- incremental increase of a propofol dose. Results We observed a reduction of both RE and SE values that correlated with the OAA/S (correlation coefficient of 0.819 in RE-OAA/S and 0.753 in SE-OAA/S). The RE and SE values corresponding to awake (OAA/S score 5), light sedation (OAA/S 3-4) and deep sedation (OAA/S 1-2) displayed differences (P < 0.05). Conclusions The results indicate that spectral entropy can be utilized as a reliable objective monitor to determine the depth of propofol-induced sedation.

The vasodilatory effect of ketamine is independent of the N-methyl-D-aspartate receptor: lack of functional N-methyl-D-aspartate receptors in rat mesenteric artery smooth muscle.

Background and objective Ketamine, which is a general anaesthetic that induces a dissociative anaesthesia, acts by blocking the N-methyl-D-aspartate receptor (NMDAr) in the brain. Although ketamine elevates blood pressure under the clinical setting, the in-vitro effect of ketamine is vasodilatory. However, it is not clear yet whether the vasodilation by ketamine involves functions of the NMDAr. Therefore, we examined whether the NMDAr is functional in vascular smooth muscle and whether the vasodilatory effect of ketamine is associated with the NMDAr. Methods We measured isometric tension of endothelium-denuded arterial rings from rat mesentery. The relaxing effects of ketamine, after rings were precontracted with noradrenaline (10 μmol l−1) or high KCl (70 mmol l−1), were examined. The effects of DL-2-amino-5-phosphonopentanoic acid (AP-5), a competitive NMDAr blocker that is structurally distinct from ketamine, were also examined. The relaxing effects of ketamine in the presence of AP-5 were compared with those in the absence of AP-5. The effects of NMDAr agonists N-methyl-D-aspartate and glutamate were analysed in order to examine the existence of a functional NMDAr. Results Both S(+)-ketamine and racemic(±)-ketamine, with similar potencies and efficacies and in a concentration-dependent manner, relaxed the precontracted arterial rings. However, AP-5 neither relaxed the arteries nor affected the vasodilatory actions of ketamine. N-methyl-D-aspartate and glutamate (0.01–1 mmol l−1) had negligible effects on isometric tension under the resting or precontracted condition. Conclusion These results suggest that the NMDAr is not functional in vascular smooth muscle, and the vasodilatory action of ketamine is independent of the NMDAr in the rat mesenteric artery.

Facilitation of serotonin-induced contraction of rat mesenteric artery by ketamine

Ketamine is an anesthetic with hypertensive effects, which make it useful for patients at risk of shock. However, previous ex vivo studies reported vasodilatory actions of ketamine in isolated arteries. In this study, we reexamined the effects of ketamine on arterial tones in the presence and absence of physiological concentrations of 5-hydroxytryptamine (5-HT) and norepinephrine (NE) by measuring the isometric tension of endothelium-denuded rat mesenteric arterial rings. Ketamine little affected the resting tone of control mesenteric arterial rings, but, in the presence of 5-HT (100~200 nM), ketamine (10~100 µM) markedly contracted the arterial rings. Ketamine did not contract arterial rings in the presence of NE (10 nM), indicating that the vasoconstrictive action of ketamine is 5-HT-dependent. The concentration-response curves (CRCs) of 5-HT were clearly shifted to the left in the presence of ketamine (30 µM), whereas the CRCs of NE were little affected by ketamine. The left shift of the 5-HT CRCs caused by ketamine was reversed with ketanserin, a competitive 5-HT2A receptor inhibitor, indicating that ketamine facilitated the activation of 5-HT2A receptors. Anpirtoline and BW723C86, selective agonists of 5-HT1B and 5-HT2B receptors, respectively, did not contract arterial rings in the absence or presence of ketamine. These results indicate that ketamine specifically enhances 5-HT2A receptor-mediated vasoconstriction and that it is vasoconstrictive in a clinical setting. The facilitative action of ketamine on 5-HT2A receptors should be considered in ketamine-induced hypertension as well as in the pathogenesis of diseases such as schizophrenia, wherein experimental animal models are frequently generated using ketamine.

The influence of different mechanical ventilator settings of peak inspiratory pressure on stroke volume variation in pediatric cardiac surgery patients

Background The usefulness of dynamic parameters derived by heart-lung interaction for fluid responsiveness in pediatric patients has been revealed. However, the effects of peak inspiratory pressure (PIP) that could affect the absolute values and the accuracy in pediatric patients have not been well established. Methods Participants were 30 pediatric patients who underwent ventricular septal defect repair. After completion of surgical procedure and sternum closure, mean arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index and stroke volume variation (SVV) were measured at PIP 10 cmH2O (PIP10), at PIP 15 cmH2O (PIP15), at PIP 20 cmH2O (PIP20) and at PIP 25 cmH2O (PIP25). Results SVV at PIP15 was larger than that at PIP10 (13.7 ± 2.9% at PIP10 vs 14.7 ± 2.5% at PIP15, P < 0.001) and SVV at PIP20 was larger than that at PIP10 and PIP15 (13.7 ± 2.9% at PIP10 vs 15.4 ± 2.5% at PIP20, P < 0.001; 14.7 ± 2.5% at PIP15 vs 15.4 ± 2.5% at PIP20, P < 0.001) and SVV at PIP25 was larger than that at PIP10 and PIP15 and PIP20 (13.7 ± 2.9% at PIP10 vs 17.4 ± 2.4% at PIP25, P < 0.001; 14.7 ± 2.5% at PIP15 vs 17.4 ± 2.4% at PIP25, P < 0.001; 15.4 ± 2.5% at PIP20 vs 17.4 ± 2.4% at PIP25, P < 0.001). Conclusions SVV is affected by different levels of PIP in same patient and under same volume status. This finding must be taken into consideration when SVV is used to predict fluid responsiveness in mechanically ventilated pediatric patients.

The radiation safety education and the pain physicians' efforts to reduce radiation exposure

Background C-arm fluoroscopy equipment is important for interventional pain management and can cause radiation injury to physicians and patients. We compared radiation safety education and efforts to reduce the radiation exposure of pain specialists. Methods A survey of 49 pain specialists was conducted anonymously in 2016. The questionnaire had 16 questions. That questionnaire was about radiation safety knowledge and efforts to reduce exposure. We investigated the correlation between radiation safety education and efforts of radiation protection. We compared the results from 2016 and a published survey from 2011. Results According to the 2016 survey, all respondents used C-arm fluoroscopy in pain interventions. Nineteen respondents (39%) had received radiation safety education. Physicians had insufficient knowledge about radiation safety. When the radiation safety education group and the non-education group are compared, there was no significant difference in efforts to reduce radiation exposure and radiation safety knowledge. When the 2011 and 2016 surveys were compared, the use of low dose mode (P = 0.000) and pulsed mode had increased significantly (P = 0.001). The number checking for damage to radiation protective garments (P = 0.000) and use of the dosimeter had also increased significantly (P = 0.009). But there was no significant difference in other efforts to reduce radiation exposure. Conclusions Pain physicians seem to lack knowledge of radiation safety and the number of physicians receiving radiation safety education is low. According to this study, education does not lead to practice. Therefore, pain physicians should receive regular radiation safety education and the education should be mandatory.

Radiation safety: a focus on lead aprons and thyroid shields in interventional pain management

C-arm fluoroscopy is useful equipment in interventional pain management because it helps to guide correct needle targeting for the accurate injection and drug delivery. However, due to increased use of C-arm fluoroscopy in various pain procedures, the risk of radiation exposure is a significant concern for pain physicians. The harmful biological effects of ionizing radiation on the human body are well known. It is therefore necessary to strive to reduce radiation exposure. Lead aprons with thyroid shields are the most fundamental radiation protective devices for interventional procedures, and are very effective. However, the operators radiation safety cannot be guaranteed because pain physicians seem to lack sufficient interest, knowledge, and awareness about radiation safety. Also, inappropriate care and use of radiation protective devices may result in a higher risk of radiation exposure. The purpose of this article was to review the literature on radiation safety with a focus on lead aprons and thyroid shields and present recommendations related to those devices during C-arm fluoroscopic-guided interventions by pain physicians.

Anesthetic managements for correction of aortic valve regurgitation in a patient with Loeys-Dietz Syndrome - A case report -

Loeys-Dietz Syndrome (LDS) is a recently described autosomal dominant aortic aneurysm syndrome with widespread systemic involvement. It is characterized by the triad of 1) arterial tortuosity and aneurysms, 2) hypertelorism, and 3) bifid uvula or cleft palate. A 12-year-old boy with LDS was scheduled to undergo correction of aortic valve regurgitation due to aortic annuloectasia. We report our clinical experiences of a case of LDS patient with brief review of related literatures and relevant anesthetic problems.