The Changes in Relative Blood Volume during Dialysis Are Characterized by Ultrafiltration Rate and Predialysis Blood Test Values.

INTRODUCTION: Continuous monitoring of relative blood volume (percentage BV) in hemodialysis (HD) is critical for determining dry weight and preventing intradialytic hypotension. However, the cause of the BV variation remains unknown. This research aimed to examine factors that influence the percentage BV. METHODS: We devised a formula based on coefficients ("a," "τ," and "b") to predict changes in percentage BV. "a" denotes a significant decrease in percentage BV in the early stages of HD. "τ" represents the transition from early to late phase of HD. "b" denotes the slope of the decrease in percentage BV in the late phase of HD. We measured the percentage BV in 18 patients with end-stage renal disease. The coefficients were estimated by fitting experimental data from patients using a least squares optimization algorithm. A correlation analysis of these parameters and patient predialysis data was performed. RESULTS: Ultrafiltration rate (UFR) was found to be negatively correlated with "b" (r = -0.851, p < 0.01). However, UFR was not significantly related to "a." Predialysis serum total protein level was negatively correlated with "a" (r = -0.531, p = 0.042). Predialysis serum albumin and predialysis sodium were not significantly correlated with "a" and "τ." Plasma osmolarity did not have a significant relationship with "a" and "τ." DISCUSSION/CONCLUSION: UFR influenced the decrease in percentage BV in the late phase but did not influence the decrease of percentage BV in the early phase. "a" was associated with predialysis serum total protein level but not with plasma osmolality or predialysis sodium. This implies that colloid oncotic pressure is important for plasma refilling immediately after dialysis begins. During the change of percentage BV, the decrease in the early phase of dialysis was not related to UFR, but related to other parameters, especially predialysis total protein level. A decrease in the late phase of dialysis is related to UFR.

The influence of electrocardiogram (ECG) filters on the heights of R and T waves in children.

Anesthesiologists often compare intraoperative and preoperative electrocardiogram (ECG) waveforms in patients undergoing general anesthesia. In addition, many intraoperative ECG monitors have filters for removing electrocautery noise. In pediatric anesthesiology practice, we often note the appearance of elevated T waves-specifically, an increase in their height-with the use of such filters, even though no actual clinical change has occurred, which possibly leads to misdiagnosis. We investigated changes in R and T wave heights and in the T/R ratio according to the use of the strong (S) versus the diagnostic (D) filtering mode during pediatric anesthesiology. Primary outcomes were the dependence of the heights of the R and T waves on the filter mode and the correlation between rates of change in the R- and T-wave heights and heart rate (HR). In the S mode, the height of the R wave was lower (p = 0.013, η2 = 0.28) and the T/R ratio was higher than the corresponding values in the D mode (χ2 = 20.46, p < 0.001). The T/R ratios were also higher in the S mode than in the D mode, and when the D mode was changed to the S mode during tachycardia, there was a strong correlation between the rate of reduction in the R wave and HR (r = 0. 573, p = 0.041). Significant differences in the heights of the R wave and in the T/R ratio occur when using different intraoperative ECG filtering modes. Specifically, in S mode, a greater relative increase in T wave height may occur due to a significant decrease in R wave height. To avoid spurious diagnoses, anesthesiologists should be familiar with these potentially purely filter-driven changes whenever ECG is intraoperatively monitored.

Quantification and Visualization of Reliable Hemodynamics Evaluation Based on Non-Contact Arteriovenous Fistula Measurement.

The condition of arteriovenous fistula (AVF) blood flow is typically checked by using auscultation; however, auscultation should require a qualitative judgment dependent on the skills of doctors, and further attention to contact infection is required. For these reasons, this study developed a non-contact and non-invasive medical device to measure the pulse wave of AVFs by applying optical imaging technology. As a first step toward realization of the quantification judgment based on non-contact AVF measurement, we experimentally validated the developed system, whereby the hemodynamics of 168 subjects were visually and quantitatively evaluated based on clinical tests. Based on the evaluation results, the fundamental statistical characteristics of the non-contact measurement, including the average and median values, and distribution of measured signal-to-noise power ratio, were demonstrated. The clinical test results contributed to the future construction of quantified criteria for the AVF condition with the non-contact measurement.

Influence of measurement principle on total hemoglobin value.

BACKGROUND: Total hemoglobin (tHb) measurement is indispensable for determining the patient's condition (hemorrhagic vs. ischemic) and need for blood transfusion. Conductivity- and absorbance-based measurement methods are used for blood gas analysis of tHb. For conductivity-based measurement, tHb is calculated after converting blood conductivity into a hematocrit value, whereas absorbance measurement is based on light absorbance after red blood cell hemolysis. Due to changes in plasma electrolytes and hemolysis, there is a possibility that conductivity- and absorbance-based measurement methods may cause a difference in tHb. METHODS: In this study, test samples with controlled electrolyte changes and hemolysis were created by adding sodium chloride, distilled water or hemolytic blood to blood samples collected from healthy volunteers, and tHb values were compared between both methods. RESULTS: Conductivity-based measurement revealed reduced tHb value (from 15.49 to 13.05 g/dl) following the addition of 10% sodium chloride, which was also reduced by the addition of hemolysate. Conversely, the addition of distilled water significantly increased tHb value than the expected value. In the absorbance method, there was no significant change in tHb value due to electrolyte change or hemolysis. CONCLUSIONS: We have to recognize unexpected conductivity changes occur at all times when tHb is measured via conductivity- and absorbance-based measurement methods. The absorbance method should be used when measuring tHb in patients with expected blood conductivity changes. However, when using this method, the added contribution of hemoglobin from hemolytic erythrocytes lacking oxygen carrying capacity must be considered. We recognize that discrepancy can occur between conductivity- and absorbance-based measurement methods when tHb is measured.

The measurement of blood pressure by the linear method compared to the deflation methods differently modifies the pulse oximeter alarm frequency.

BACKGROUND: Noninvasive blood-pressure measurement device and pulse oximeter are important for patient monitoring. When these are placed on the same side, cuff inflation sometimes causes measurement failure by pulse oximeter. OBJECTIVE: The present study aimed to compare the pulse oximeter alarm frequency and pulse-wave disappearance duration between noninvasive blood-pressure measurement using the deflation method and that using the linear inflation method. METHODS: The study included 10 healthy subjects. The cuff for automatic sphygmomanometer was wrapped on one side of the upper arm and for pulse oximeter was attached to the thumb of the same side of upper limbs. RESULTS: The alarm frequency was 0 and 26% using the linear inflation and the deflation methods, respectively. Additionally, the pulse-wave disappearance duration was significantly longer using the deflation method than that using the linear inflation method (10.0 ± 1.5 vs 1.7 ± 0.8 s). With the linear inflation method, this duration was or less 3 s. In the deflation method, an excess pressure of 40 mmHg was used, which caused the alarm to turn on. Additionally, the heart rate was found to influence the alarm occurrence during measurement using the deflation method. CONCLUSION: Heart rate may influence alarm occurrence during blood-pressure measurement using the step deflation method. Using the linear inflation method, the risks of alarm occurrence and measurement failure are low, even when the pulse oximeter and blood-pressure measurement cuffs are installed on the same side, suggesting that this method is suitable for clinical use.

Age-related effects of three inhalational anesthetics at one minimum alveolar concentration on electroencephalogram waveform.

BACKGROUND: The characteristics of electroencephalogram (EEG) profiles under general anesthesia may depend on age and type of anesthetic. AIM: This study investigated age-related differences in EEG waveforms between three inhalational anesthetics used at the same minimum alveolar concentration (MAC), which indicates the level of analgesia. METHODS: Patients with American Society of Anesthesiologists physical status I-II were divided into three groups according to age: pediatric (≦ 15 years); adult (16-64 years); and elderly (≧ 65 years). Each group was divided into three subgroups according to the inhalational anesthetic used: sevoflurane, isoflurane, and desflurane. Anesthesia was maintained at 1 MAC, followed by assessment of 95% spectral edge frequency (SEF95) values and amplitude of EEG waveform. RESULTS: The 3 age groups comprised a total of 180 patients. The mean (± SD) EEG waveform amplitude and SEF95 values for sevoflurane in the pediatric, adult, and elderly age groups, respectively, were: 32.9 ± 2.9 µV and 16.7 ± 2.4 Hz; 16.4 ± 3.6 µV and 12.2 ± 1.3 Hz; and 11.0 ± 2.1 µV and 13.6 ± 1.6 Hz. EEG waveform amplitude and SEF95 values were significantly higher in the pediatric group than in the other groups. SEF95 value was higher in the elderly group than in the adult group. Similar results were obtained for isoflurane and desflurane. CONCLUSION: The amplitude of the EEG waveform and SEF95 values varied with age, even at the same analgesic state in patients under general anesthesia. This age-dependent change in EEG waveform was observed for all three inhalational anesthetics, and should be considered in procedures requiring general anesthesia.

Usefulness of a stool to stabilize dental chairs for cardiopulmonary resuscitation (CPR).

BACKGROUND: Cardiopulmonary resuscitation (CPR) requires immediate start of manual chest compression (MCC) and defibrillation as soon as possible. During dental surgery, CPR could be started in the dental chair considering difficulty to move the patient from the dental chair to the floor. However, all types of dental chairs are not stable for MCC. We previously developed a procedure to stabilize a dental chair by using a stool. EUROPEAN RESUSCITATION COUNCIL (ERC) guideline 2015 adopted our procedure when cardiac arrest during dental surgery. The objective of this study was to verify the efficacy of a stool as a stabilizer in different types of dental chairs. METHODS: Three health care providers participated in this study, and 8 kinds of dental chairs were examined. MCC were performed on a manikin that was laid on the backrest of a dental chair. A stool was placed under the backrest to stabilize the dental chair. The vertical displacement of the backrest by MCC was recorded by a camcorder and measured by millimeter. Next, the vertical displacement of the backrest by MCC were compared between with and without a stool. RESULTS: In all 8 dental chairs, the method by using a stool significantly reduced the vertical displacements of the backrest by during MCC. The reduction ratio (mean [interquartile range]) varied between nearly 27 [20] and 87 [5] %. In the largest stabilization case, the displacement was 3.5 [0.5] mm with a stool versus 26 [5.5] mm without a stool (p <  0.001). CONCLUSIONS: Our procedure to stabilize dental chairs by using a stool reduced the displacement of a backrest against MCC in all chairs. CLINICAL RELEVANCE: Effective MCC could be performed in dental chairs by using a stool when sudden cardiac arrest occurs during dental surgery.

Effect of planecta and ROSE™ on the frequency characteristics of blood pressure-transducer kits.

Pressure-transducer kits have frequency characteristics such as natural frequency and damping coefficient, which affect the monitoring accuracy. The aim of the present study was to investigate the effect of planecta ports and a damping device (ROSE™, Argon Medical Devices, TX, USA) on the frequency characteristics of pressure-transducer kits. The FloTrac sensor kit (Edwards Lifesciences, CA, USA) and the DTXplus transducer kit (Argon Medical Devices) were prepared with planecta ports, and their frequency characteristics were tested with or without ROSE™. The natural frequency and damping coefficient of each kit were obtained using frequency characteristics analysis software and evaluated by plotting them on the Gardner's chart. By inserting a planecta port, the natural frequency markedly decreased in both the FloTrac sensor kit (from 40 to 22 Hz) and the DTXplus transducer kit (from 35 to 22 Hz). In both kits with one planecta port, the damping coefficient markedly increased by insertion of ROSE™ from 0.2 to 0.5, optimising frequency characteristics. In both kits with two planecta ports, however, the natural frequency decreased from 22 to 12 Hz. The damping coefficient increased from 0.2 to 0.8 by insertion of ROSE™; however, optimisation was not achieved even by ROSE™ insertion. Planecta ports decrease the natural frequency of the kit. ROSE™ is useful to optimise the frequency characteristics in the kits without or with one planecta port. However, optimisation is difficult with two or more planecta ports, even with the ROSE™ device.