Segmental blood flow and hemodynamic state of lymphedematous and nonlymphedematous arms

Use of the Cephalic Vein in DIEP Breast Reconstruction Does Not Increase Risk of Lymphedema of the Ipsilateral Arm

SUMMARY

Flap failure is a rare but devastating complication in deep inferior epigastric perforator (DIEP) flap reconstructions. Common causes of partial or complete flap failure are related to venous congestion. Although the cephalic vein is usually a safe and reliable recipient vein for additional venous outflow, there is a hypothesized risk of donor-arm lymphedema secondary to lymphatic vessel damage in the vicinity of the cephalic vein or related to scarring and reduced venous backflow of the arm. The aim was to assess whether the cephalic vein as an additional recipient vessel, by means of the superficial inferior epigastric vein in DIEP flap breast reconstruction, was associated with long-term volume changes of the arm and/or symptoms of lymphedema. Arm volume was assessed preoperatively in patients scheduled to undergo unilateral delayed DIEP flap breast reconstruction at Uppsala University Hospital, Sweden, between 2001 and 2007. Long-term postoperative assessments were performed in 2015 to 2016. Water displacement and circumferential measurement were assessed preoperatively and postoperatively by the same lymphedema therapists. Patients were divided into two groups: DIEP reconstruction with the cephalic vein or without. Fifty-four patients fulfilled the inclusion criteria and completed the study, with a mean follow-up time of 136 months. There was no increased occurrence of lymphedema in the group undergoing DIEP flap reconstruction with the cephalic vein as extra venous drainage, based on an analysis of change from baseline in arm volume difference.This study shows that the cephalic vein can be used for secondary venous outflow in DIEP breast reconstruction without long-term risk of ipsilateral arm volume increase or symptoms of lymphedema.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, II.

Thoracic, Peripheral, and Cerebral Volume, Circulatory and Pressure Responses To PEEP During Simulated Hemorrhage in a Pig Model: a Case Study

Positive end-expiratory pressure (PEEP) is a respiratory/ventilation procedure that is used to maintain or improve breathing in clinical and experimental cases that exhibit impaired lung function. Body fluid shift movement is not monitored during PEEP application in intensive care units (ICU), which would be interesting specifically in hypotensive patients. Brain injured and hypotensive patients are known to have compromised cerebral blood flow (CBF) autoregulation (AR) but currently, there is no non-invasive way to assess the risk of implementing a hypotensive resuscitation strategy and PEEP use in these patients. The advantage of electrical bioimpedance measurement is that it is noninvasive, continuous, and convenient. Since it has good time resolution, it is ideal for monitoring in intensive care units (ICU). The basis of its future use is to establish physiological correlates. In this study, we demonstrate the use of electrical bioimpedance measurement during bleeding and the use of PEEP in pig measurement. In an anesthetized pig, we performed multimodal recording on the torso and head involving electrical bioimpedance spectroscopy (EIS), fixed frequency impedance plethysmography (IPG), and bipolar (rheoencephalography - REG) measurements and processed data offline. Challenges (n=16) were PEEP, bleeding, change of SAP, and CO2 inhalation. The total measurement time was 4.12 hours. Systemic circulatory results: Bleeding caused a continuous decrease of SAP, cardiac output (CO), and increase of heart rate, temperature, shock index (SI), vegetative - Kerdo index (KI). Pulse pressure (PP) decreased only after second bleeding which coincided with loss of CBF AR. Pulmonary arterial pressure (PAP) increased during PEEP challenges as a function of time and bleeding. EIS/IPG results: Body fluid shift change was characterized by EIS-related variables. Electrical Impedance Spectroscopy was used to quantify the intravascular, interstitial, and intracellular volume changes during the application of PEEP and simulated hemorrhage. The intravascular fluid compartment was the primary source of blood during hemorrhage. PEEP produced a large fluid shift out of the intravascular compartment during the first bleeding period and continued to lose more blood following the second and third bleeding. Fixed frequency IPG was used to quantify the circulatory responses of the calf during PEEP and simulated hemorrhage. PEEP reduced the arterial blood flow into the calf and venous outflow from the calf. Head results: CBF AR was evaluated as a function of SAP change. Before bleeding, and after moderate bleeding, intracranial pressure (ICP), REG, and carotid flow pulse amplitudes (CFa) increased. This change reflected vasodilatation and active CBF AR. After additional hemorrhaging during PEEP, SAP, ICP, REG, CFa signal amplitudes decreased, indicating passive CBF AR. 1) The indicators of active AR status by modalities was the following: REG (n=9, 56 %), CFa (n=7, 44 %), and ICP (n=6, 38 %); 2) CBF reactivity was better for REG than ICP; 3) REG and ICP correlation coefficient were high (R2 = 0.81) during CBF AR active status; 4) PRx and REGx reflected active CBF AR status. CBF AR monitoring with REG offers safety for patients by preventing decreased CBF and secondary brain injury. We used different types of bioimpedance instrumentation to identify physiologic responses in the different parts of the body (that have not been discussed before) and how the peripheral responses ultimately lead to decreased cardiac output and changes in the head. These bioimpedance methods can improve ICU monitoring, increase the adequacy of therapy, and decrease mortality and morbidity.

Venous hemodynamics assessed with air plethysmography in legs with lymphedema

This study was conducted to identify specific abnormalities using the results from air plethysmography in legs with lymphedema. A routine air plethysmography exercise protocol was performed in 31 patients with unilateral leg lymphedema, and the results were compared with those of 53 patients with unilateral great saphenous vein reflux and 15 normal subjects. The venous filling index in legs with lymphedema (2.1 ± 1.2 mL/sec) was smaller than in legs with great saphenous vein reflux (6.4 ± 4.1 mL/sec, p < 0.05), but was not different from that in normal legs (1.9 ± 1.2 mL/sec). The ejection fraction was similar in all groups. The residual volume fraction in legs with lymphedema (35 ± 32%) was larger than that in normal subjects (13 ± 23%, p < 0.05), but was not significantly different from that in the contralateral leg of the lymphedema patients (32 ± 27%). In conclusion, we found no specific air plethysmography findings in uncomplicated lymphedema.

Montgomery L, J. Pearce F, Armonda R. Measurement of Cerebral Blood Flow Autoregulation with Rheoencephalography: A Comparative Pig Study

Neuromonitoring is performed to prevent further (secondary) brain damage by detecting low brain blood flow following a head injury, stroke or neurosurgery. This comparative neuromonitoring study is part of an ongoing investigation of brain bioimpedance (rheoencephalography-REG) as a measuring modality for use in both civilian and military medical settings, such as patient transport, emergency care and neurosurgery intensive care. In a previous animal study, we validated that REG detects cerebral blood flow autoregulation (CBF AR), the body's physiological mechanism that protects the brain from adverse effects of low brain blood flow (hypoxia/ischemia). In the current descriptive pig study, the primary goal was to compare measurements of CBF AR made with REG to measurements made with other neuromonitoring modalities: laser Doppler flow (LDF); intracranial pressure (ICP); absolute CBF; carotid flow (CF); and systemic arterial pressure (SAP). Challenges administered to anesthetized pigs were severe induced hemorrhage (bleeding) and resuscitation; CO2 inhalation; and positive end expiratory pressure (PEEP). Data were stored on a computer and processed offline. After hemorrhage, the loss of CBF AR was detected by REG, ICP, and CF, all of which passively followed systemic arterial SAP after bleeding. Loss of CBF AR was the earliest indicator of low brain blood flow: loss of CBF AR occurred before a decrease in cardiac output, which is the cardiovascular response to hemorrhage. A secondary goal of this study was to validate the usefulness of new automated data processing software developed to detect the status of CBF AR. Both the new automated software and the traditional (observational) evaluation indicated the status of CBF AR. REG indicates the earliest breakdown of CBF AR; cessation of EEG for 2 seconds and respiration would be used as additional indicators of loss of CBF AR. The clinical significance of this animal study is that REG shows potential for use as a noninvasive, continuous and non-operator dependent neuromonitor of CBF AR in both civilian and military medical settings. Human validation studies of neuromonitoring with REG are currently in progress.

Alteration of Blood Circulation in the Upper Limb Before and After Surgery for Breast Cancer Associated with Axillary Lymph Node Dissection or Sentinel Lymph Node Biopsy

BACKGROUND

This aim of this study was to assess and compare arterial and venous circulation in women with axillary lymph node dissection (ALND) and sentinel lymph node biopsy (SLNB) before and after breast cancer surgery.

METHODS AND RESULTS

Fifty-two women took part in the study, divided into three groups: those undergoing ALND at levels I, II, and III (ALNDG), with mean age of 56.29 ± 10.85 years old; those undergoing sentinel lymph node biopsy (SLNBG), with mean age of 57.7 ± 7.07 years old; and controls without diagnosis of breast cancer (CG), with mean age of 53.92 ± 8.85 years old. Maximum venous and arterial flow velocities in upper limbs were assessed before and after surgical treatment for breast cancer by means of Doppler ultrasonography (Nicolet Vascular Versalab SE^®). Data normality was assessed by using the Shapiro-Wilk's test, with normally distributed variables being analyzed with analysis of variance (ANOVA) and post hoc Tukey's test or t-test. For variables with non-normal distribution, Kruskal-Wallis' test and post hoc Dunn's test were used at p < 0.05. There was significant difference in the maximum blood flow velocities, both venous (ALNDG) and arterial (SLNBG).

CONCLUSION

The results suggest that ALND and SLNB can interfere with the upper limp blood circulation.

Monitoring intracellular, interstitial, and intravascular volume changes during fluid management procedures

The bioimpedance spectroscopic (BIS) analytical algorithm described in this report allows for the non-invasive measurement of intravascular, interstitial, and intracellular volume changes during various fluid management procedures. The purpose of this study was to test clinical use feasibility and to demonstrate the validity of the BIS algorithm in computing compartmental volume shifts in human subjects undergoing fluid management treatment. Validation was performed using volume changes recorded from 20 end stage renal disease patients. The validation procedure involved mathematically deriving post hoc hematocrit profiles from the BIS data-generated fluid redistribution time profiles. These derived hematocrit profiles were then compared to serial hematocrit values measured simultaneously by a CritLine(®) monitor during 60 routine hemodialysis sessions. Regression and Bland-Altman analyses confirm that the BIS algorithm can be used to reliably derive the continuous and real-time rates of change of the compartmental fluid volumes. Regression results yielded a R (2) > 0.99 between the two measures of hematocrit at different times during dialysis. The slopes of the regression equations at the different times were nearly identical, demonstrating an almost one-to-one correspondence between the BIS and CritLine(®) hematocrits. Bland-Altman analysis show that the BIS algorithm can be used interchangeably with the CritLine(®) monitor for the measurement of hematocrit. The present study demonstrates for the first time that BIS can provide real-time continuous measurements of compartmental intravascular, interstitial and intracellular fluid volume changes during fluid management procedures when used in conjunction with this new algorithm.

Resting blood flow in the skin: does it exist, and what is the influence of temperature, aging, and diabetes?

Measurement of resting blood flow to the skin and other organs is an important indicator of health and disease and a way to assess the reaction to various stimuli and pharmaceutical interventions. However, unlike plasma ions such as sodium or potassium, it is difficult to determine what the proper value for resting blood flow really is. Part of the problem is in the measurement of blood flow; various techniques yield very different measures of skin blood flow even in the same area. Even if there were common techniques, resting blood flow to tissue, such as the skin, is determined by the interaction of a plurality of factors, including the sympathetic nervous system, temperature, pressure, shear forces on blood vessels, tissue osmolality, and a variety of other stimuli. Compounding this variability, the blood flow response to any stressor is reduced by free radicals in the blood and diminished by aging and diabetes. Race also has an effect on resting blood flow to the skin. All these factors interact to make the exact resting blood flow difficult to determine in any one individual and at any one time. This review examines the main techniques to assess blood flow, the factors that alter blood flow in the skin, and how aging and diabetes affect blood flow. Recommendations for the measurement of resting blood flow are presented.