Sympathectomy-mediated vasodilatation: a randomized concentration ranging study of epidural bupivacaine

Correlation of perfusion index change and analgesic efficacy in transforaminal steroid injection for lumbosacral pain, a prospective observational study

Background and Aims

Low back pain is a common problem and a major burden to society. Transforaminal epidural steroid injection is one of the most effective treatment modalities for back pain. We aim to objectively quantify pain relief of lumbosacral radicular pain post transforaminal steroid injection by correlating perfusion index (PI), reflecting real-time peripheral blood flow change at the site of monitoring, controlled by sympathetic system with Numerical rate score (NRS) and SLRT improvement.

Material and Methods

A prospective observational study, conducted at K.S Hegde Medical Academy, Mangaluru, from June 2021 to June 2022 as a time-bound study. After IEC clearance (IEC certificate number) for the procedure and study, patients undergoing transforaminal epidural steroid injection for lumbosacral radicular pain were enrolled, excluding those meeting the exclusion criteria. PI change and NRS score improvement were noted at 0, 5, 10, 15, and 30 minutes along with pre and post-procedure SLRT. Results were analyzed.

Results

A total of 40 patients were analyzed. PI change at 30 minutes was 2.113 from a baseline of 0.217. Median NRS of 5, improved to 0 and the mean SLRT of 45.17 to 61.45 at the end of 30 minutes. All changes are statistically significant with P (<0.01). correlation between the PI change with NRS is mild (-0.312).

Conclusion

PI change ratio shows an overall improvement in pain levels objectively, in a non-invasive, easy, and reliable way. Simultaneous improvement in both NRS and SLRT is clinically significant but cannot predict a correlated quantitative measure of pain relief.

Brachial Plexus Block for Removal of Retained Radial Artery Sheath

In this case, we present a lesser-known application of regional anesthesia, specifically, managing a patient with vasospasm and retained radial artery (RA) vascular sheath after coronary angiography. Providing an ultrasound-guided supraclavicular block, in combination with general anesthesia, allowed the proceduralist to remove the retained sheath after several hours of failed treatment and manipulation. Severe arterial spasm was alleviated by eliciting a sympathectomy, along with analgesia of the right upper extremity, and maintaining this post-procedure. The block optimized arterial flow through the RA post-intervention and helped manage the patients' pain from manipulation.

Pulse perfusion index for predicting intrapartum fever during epidural analgesia

STUDY OBJECTIVE

To assess whether pulse perfusion index (PI) values could be employed to predict intrapartum fever and to provide a cut-off PI value for predicting intrapartum fever occurrence.

DESIGN

We conducted a single-center, prospective, observational study.

SETTING

Delivery room at the Department of Obstetrics, Affiliated Hospital of Jiangsu University.

PATIENTS

117 parturients who intended to have a vaginal delivery.

INTERVENTIONS

Each parturient received epidural analgesia.

MEASUREMENTS

We checked each parturient's tympanic temperature before analgesia (T₀), at 1 h (T₁) and 2 h (T₂) after analgesia, immediately at the end of the second (T₃) and third (T₄) stages of labor, and at 1 h postpartum (T₅). A temperature of ≥38°C was defined as fever. PI, measured on the right second toe, was recorded before analgesia (PI₀) and at 10 min (PI₁₀), 20 min (PI₂₀), and 30 min (PI₃₀) after analgesia. The PI change rate was calculated as the incremental change in PI₃₀ from PI₀, divided by the PI₀. Receiver operating characteristic (ROC) curves were used to verify the utility of the PI₃₀ and PI change rate values for predicting intrapartum fever.

MAIN RESULTS

We found that peak temperature (T_P) occurred at the end of the second or the third stage of labor. Within 30 min after analgesia, the PI showed a significant increase over time and there was a linear correlation between PI₃₀ and T_P values (P < 0.001, r = 0.544). The PI₁₀, PI₂₀, PI₃₀ and PI change rate in febrile parturients were higher than those in afebrile parturients (P < 0.001). The area under the ROC (AUROC) for PI₃₀ was 0.818 (P < 0.001) with a cut-off of 9.30. The AUROC of the PI change rate was 0.738 (P < 0.001) with a cut-off of 3.45.

CONCLUSIONS

PI₃₀ and PI change rate values could be used to predict intrapartum fever in parturients after epidural analgesia.

Infrared thermographic assessment of spinal anaesthesia-related cutaneous temperature changes during caesarean section

INTRODUCTION

Assessment of adequacy of spinal anaesthesia prior to obstetric surgery is extremely important but can be problematic because currently available clinical assessment methods are indirect and subjective. As the sympathectomy associated with spinal anaesthesia is known to cause vasodilation and heat redistribution, we sought to assess whether spinal anaesthesia led to significant and consistent cutaneous temperature changes as measured by infrared thermography.

METHODS

Following ethics committee approval, this observational study was conducted in a tertiary level obstetric centre. Participants included women undergoing elective caesarean section under spinal anaesthesia. Following consent, a Flir T540 infrared camera captured thermographic images over the feet, patella, buttock, iliac crests, xiphisternum and axilla. Temperature was measured prior to spinal needle insertion (T0) and following clinical assessment when the block was deemed adequate.

RESULTS

Thirty patients were included. Baseline temperature varied considerable by site. Spinal anaesthesia altered skin temperature in all areas of interest: right and left hallux (mean of differences (MD) +4.0°C and 5.2°C respectively, P <0.0001), right and left plantar (MD +6.1°C and 6.8°C respectively, P <0.0001), patella (MD -0.33°C, P=0.0445), buttock (MD -0.5°C, P=0.009), iliac crest (MD -0.7°C, P=0.0004), xiphisternum (MD -0.95°C, P <0.0001) and axilla (MD -0.71°C, P=0.0002).

CONCLUSIONS

Following spinal anaesthesia thermographic imaging identified different patterns of skin temperature changes, with pronounced temperature increases measured in the feet and cooling of a lesser amplitude in the thoracic and lumbar dermatomes. Infrared thermography has the potential to provide objective measurement of sympathectomy.

Use of high-resolution thermography as a validation measure to confirm epidural anesthesia in mice: a cross-over study

BACKGROUND

Effective epidural anesthesia is confirmed in humans by sensory assessments but these tests are not feasible in mice. We hypothesized that, in mice, infrared thermography would demonstrate selective segmental warming of lower extremities following epidural anesthesia.

METHODS

We anesthetized 10 C57BL/6 mice with isoflurane and then inserted a PU-10 epidural catheter under direct surgical microscopy at T11-12. A thermal camera (thermal sensitivity ±0.05°C, pixel resolution 320x240 pixels, and spatial resolution 200 μm) recorded baseline temperature of front and rear paws, tail and ears. Thermography was assessed at baseline and 2, 5, 10, and 15 min after an epidural bolus dose of 50 μL bupivacaine 0.25% or 50 μL saline (control) using a cross-over design with dose order randomized and investigators blinded to study drug. Thermal images were recorded from video and analyzed using FLIR software. Effect over time and maximal effect (E_max) were assessed by repeated measures ANOVA and paired t-tests. Comparisons were between bupivacaine and control, and between lower vs upper extremities.

RESULTS

Epidural bupivacaine caused progressive warming of lower compared with upper extremities (P <0.001), typically returning to baseline by 15 min after administration. Mean (±SD) E_max was +3.73 (±1.56) °C for lower extremities compared with 0.56 (±0.68) °C (P=0.03) for upper extremities. Following epidural saline, there was no effect over time (E_max for lower extremities -0.88 (±0.28) °C compared with the upper extremities -0.88 (±0.19) °C (P >0.99).

CONCLUSIONS

Thermography is a useful tool to confirm epidural catheter placement in animals for which subjective, non-noxious, sensory measures are impossible.

Photoplethysmographic evaluation of sympathectomy during lumbar epidural analgesia: A randomized comparison of 0.125% ropivacaine and 0.125% levobupivacaine

BACKGROUND

There are no data on the difference between the impact of ropivacaine and levobupivacaine on sympathetic nerve fibers during central neuraxial blocks. We hypothesized that there is no difference in the degree of sympathectomy between the two drugs during lumbar epidural analgesia for labor pain.

METHODS

Sixty healthy parturients were randomized to the type of local anesthetic-opiod solution administered in the epidural space: 10 mL of 0.125% ropivacaine + 100 mcg of fentanyl or 10 mL of 0.125% levobupivacaine + 100 mcg of fentanyl. After the baseline measurement, photoplethysmography signal from the first toe of the leg was recorded 5, 10 and 20 minutes after administration of epidural analgesia.

RESULTS

Area under the curve and the pulse transit time of the toe photoplethysmography increased in both groups during the first 20 minutes after administration of epidural analgesia (P < 0.001 for both parameters in both groups). No difference in the degree of sympathectomy was found between the groups for the area under the curve. The difference in the change of the pulse transit time suggests that the two local anesthetics might differ in the degree of sympathectomy (P = 0.024).

CONCLUSION

0.125% ropivacaine and 0.125% levobupivacaine do not differ in the terms of sympathectomy-mediated side effects of the epidural block for labor analgesia. However, the photoplethysmography findings suggest a certain difference in the degree of sympathectomy between the two local anesthetics.

Assessment of skin temperature during regional anaesthesia-What the anaesthesiologist should know

Body temperature homeostasis is accurately regulated by complex feedback-driven neuronal mechanisms, which involve a multitude of thermoregulatory pathways. Thus, core temperature is constantly maintained within a narrow range. As one of the most effective regulatory systems skin temperature is dependent on skin blood flow. Skin blood flow in turn is highly dependent on sympathetic activity. Regional anaesthesia leads to blockade not only of somatosensory and motor nerve fibres but also of sympathetic fibres. As a consequence, vasoconstrictor tonic activity is abrogated and a vasodilation leads to an increase in skin blood flow and temperature. The aim of this review was to summarize the general physiology of thermoregulation and skin temperature as well as the alterations during regional anaesthesia. The main focus was the usefulness of measuring skin temperature as an indicator of regional anaesthesia success. According to the available literature, assessment of skin temperature can indeed serve to predict success of regional anaesthesia. Hence, it is important to realize that relevant and reliable temperature increase is only seen in the most distal body parts, ie fingers and toes. More proximally, temperature changes are frequently small and inconsistent, which means that assessment of block levels is not possible by temperature measurement. Furthermore, relevant skin temperature increases will only be observed in patients, which are initially vasoconstricted. In conclusion, measurement of skin temperature represents a reliable and feasible diagnostic tool to assess and predict the success or failure of regional anaesthesia procedures, especially in patients in which sensory testing is impossible.

Bolus administration of ephedrine and etilefrine induces transient vasodilation just after injection in combined epidural and general anesthesia patients: A randomized clinical study

Hypotension commonly accompanies combined epidural and general anesthesia, and intravenous bolus ephedrine and etilefrine are widely used to correct hypotension. We have noticed that systemic vascular resistance (SVR) transiently decreases just after intravenous bolus administration of these drugs. The goal of the present study was to investigate whether bolus administration of these drugs decrease SVR just after intravenous administration in combined epidural and general anesthesia patients. We investigated 40 patients who were scheduled for elective abdominal surgery. Patients were chosen as subjects if their systolic arterial pressure decreased by 20% or to <100 mmHg at 30 min after the induction of general anesthesia. Baseline hemodynamic values were recorded, and after ephedrine 10 mg injection or etilefrine 2 mg injection (equipotent), the parameters were recorded again at 0.5 min and once each min for the next 5 min thereafter. The 40 patients were enrolled into the ephedrine (n = 20) or etilefrine (n = 20) treatment groups. Patient characteristics were comparable in both groups. After ephedrine injection, SVR decreased significantly at the 1-min time point, whereas after etilefrine injection, SVR decreased significantly at the 0.5- to 2-min time points compared with baseline values. SVR at the 0.5- to 1-min time points was lower in the etilefrine versus the ephedrine group. Both drugs transiently decreased SVR after intravenous injection, but etilefrine decreased SVR much more than ephedrine, indicating that more vasodilation occurred after the injection of etilefrine than after ephedrine. It is thus important to recognize the different characteristics of these drugs.

Area Under the Curve of Finger Photoplethysmography as an Evaluation Measure for Sympathetic Activity During Lumbar Epidural Anaesthesia

Objective

To detect changes in finger photoplethysmography after administration of epidural anaesthesia as a surrogate method for evaluating autonomic nervous system activity.

Methods

We included a total of 46 patients scheduled for elective surgical procedures under lumbar epidural anaesthesia. A Biopac SS4LA pulse plethysmograph transducer was used for photoplethysmography recording, and the device was placed on the first toe of the right leg. The first standard lead of the electrocardiogram was simultaneously measured with the finger photoplethysmography. First measurement was done before the administration of epidural anaesthesia, and second measurement was done 25 minutes post administration of epidural anaesthesia.

Results

The area under the curve of the finger photoplethysmography statistically significantly increased 25 minutes after administration of epidural anaesthesia compared with the first measurement (p=0.0001). The amplitude of the finger photoplethysmography as well as the pulse transit time also statistically significantly increased after administration of epidural anaesthesia.

Conclusion

The area under the curve reflects the changes in sympathetic activity after epidural anaesthesia below the block level. It can be used for the detection of the degree of sympathetic block and, respectively, for epidural block success. Future prospects include detection of sympathetic block cessation as an indicator for discharge from the awakening room and beginning of patient verticalisation.

Observations on significant hemodynamic changes caused by a high concentration of epidurally administered ropivacaine: correlation and prediction study of stroke volume variation and central venous pressure in thoracic epidural anesthesia

Background

Thoracic epidural anesthesia (TEA) exacerbates hypotension due to peripheral vasodilator effects following the use of general anesthetics. This study aimed to compare the hemodynamic changes caused by three different concentrations of epidural ropivacaine and to evaluate the performance of the stroke-volume variation (SVV) and central venous pressure (CVP) during TEA with general anesthesia.

Methods

A total of 120 patients were administered 8 mL of ropivacaine solution via epidural injection, following randomization into one of three groups based on the concentration of ropivacaine in the study solution: 0.75%, 0.375%, or 0.2%. Hemodynamics were monitored for 30 min after loading. We analyzed the hemodynamic changes in the subgroups according to an age cutoff of 60 years. Receiver operating characteristic (ROC) analysis was performed to characterize the relationship of the SVV, CVP, and a 20% decrease in the mean arterial pressure (MAP) following TEA.

Results

Data from 109 patients were analyzed. MAP and systemic vascular resistance index were significantly decreased, and SVV was significantly increased after epidural loading only in the 0.75% ropivacaine group. There was a significant difference in hemodynamics between young and elderly subgroups in the 0.75% ropivacaine group. SVV showed a negative correlation with MAP, whereas CVP showed no correlation. The ROC analysis of SVV demonstrated a weak predictive ability of a 20% decrease in MAP at 10 min after the loading dose, with an area-under-the-curve of 0.687 and a 9.5% optimal cutoff value (sensitivity, 60.6%; specificity, 68.9%).

Conclusions

A high concentration of ropivacaine through TEA caused a significant decrease in the systemic vascular resistance and blood pressure. More significant decreases were shown in the elderly patients. Though the change of SVV showed a negative correlation with hypotension and indicated functional hypovolemia after TEA, the predictability was limited.

Clinical trials registration

Number: NCT01559285, date: January 24, 2013.

Evaluation of perfusion index as a tool for pain assessment in critically ill patients

Pain is a common and undertreated problem in critically ill patients. Pain assessment in critically ill patients is challenging and relies on complex scoring systems. The aim of this work was to find out the possible role of the perfusion index (PI) measured by a pulse oximeter (Masimo Radical 7; Masimo Corp., Irvine, CA, USA) in pain assessment in critically ill patients. A prospective observational study was carried out on 87 sedated non-intubated patients in a surgical intensive care unit. In addition to routine monitoring, a Masimo pulse oximeter probe was used for PI measurement. The sedation level of the patients was assessed by using the Richmond Agitation-Sedation Scale (RASS). The pain intensity was determined by applying the behavioral pain scale for non-intubated (BPS-NI) patients. The PI, arterial blood pressure, heart rate, RASS, and BPS-NI values before and after the application of a standard painful stimulus (changing the patient position) were reported. Correlation between the PI and other variables was carried out at the two measurements. Correlation between changes in the PI (delta PI) and in the hemodynamic variables, RASS, and BPS-NI was also done. Changing the patient position resulted in a significant increase in SBP (128 ± 20 vs 120.4 ± 20.6, P = 0.009), DBP (71.3 ± 11.2 vs 68.7 ± 11.3, P = 0.021), heart rate (99.5 ± 19 vs 92.7 ± 18.2, P = 0.013), and BPS-NI (7[6-8] vs 3[3-3], P < 0.001) values and a significant decrease in the PI (1[0.5-1.9] vs 2.2[0.97-3.6], P < 0.001) value compared to the baseline readings. There was no correlation between the values of the PI and the ABP, BPS-NI, and RASS at the two measurements. A good correlation was found between the delta PI and delta BPS-NI (r = -0.616, P < 0.001). A weak correlation was observed between the PI and heart rate after the patient positioning (r = -0.249, P < 0.02). In surgical critically ill non-intubated patients, the application of a painful stimulus was associated with decreased PI. There was a good correlation between the change in the PI and the change in BPS-NI values after the application of painful stimulus.

The Effect of Regional Analgesia on Vascular Tone in Hip Arthroplasty Patients

BACKGROUND

While it is assumed that neuraxial analgesia and pain management may beneficially influence perioperative hemodynamics, few studies provided data quantifying such effects and none have assessed the potential contribution of the addition of a nerve block.

QUESTIONS/PURPOSES

This clinical trial compared the visual analog scale (VAS) scores and measurement of arterial tone using augmentation index of patients who received combined spinal-epidural (CSE) only to patients who received both CSE and lumbar plexus block.

METHODS

After obtaining written consent, 92 patients undergoing total hip arthroplasty were randomized to receive either CSE or CSE with lumbar plexus block (LPB). Perioperative pain and arterial tone were measured using VAS scores and augmentation index (AI) respectively, at baseline and at various times postoperatively.

RESULTS

After the exclusion of 2 patients, 44 patients received CSE alone and 46 patients received CSE and LPB. Patient demographics and perioperative characteristics were similar in both groups. AI continuously decreased after placement of a CSE with or without LBP, beyond full resolution of neuraxial and peripheral blockade. Although the LPB group demonstrated a statistically significant reduction of VAS pain scores in the postanesthesia care unit (PACU; P < 0.05), overall, the addition of a LPB did not significantly reduce the AI when compared to the control group.

CONCLUSION

The addition of a LPB provided better pain control in the PACU but did not reduce the AI, compared to the control group. We conclude that the addition of a LPB may have limited ability to affect arterial tone in the presence of a continuous infusion of epidural analgesics. In summary, the addition of a LPB in patients undergoing total hip arthroplasty is clinically effective and provided better pain control, especially in the immediate postoperative period. The continuous decrease on the AI in both groups beyond the full resolution of the neuroaxial and LPB will require further studies.

Lateral Fasciectomy Sparing the Superficial Peroneal Nerve with Simultaneous Mesh Graft in Non-healing Lateral Leg Ulcers of Diverse Vascular Origins: Surgical Technique, Short- and Long-term Results from 44 Legs

OBJECTIVES

The technique of lateral fasciectomy (LF) sparing the superficial peroneal nerve with mesh graft coverage is a novel treatment of non-healing lateral leg ulcers of various vascular origin affecting the fascia. We report short- and long-term results of LF for recalcitrant lateral leg ulcers.

DESIGN

This study is a single center, retrospective case series of consecutive patients treated by LF.

MATERIALS

From 827 ulcers treated at our institution, 44 recalcitrant lateral leg ulcers affecting the fascia (41 patients) underwent lateral fasciectomy between 2006 and 2013.

METHODS

Preoperative indications, step-by-step surgical procedures, and perioperative care methodologies are presented. Long-term effects of healing and recurrence were clinically investigated or obtained through telephone interviews with relatives and local practitioners.

RESULTS

Three discrete etiologies were identified: venous ulcers (n = 24), arterial-venous/mixed ulcers (n = 11), and arteriolar Martorell hypertensive leg ulcers (n = 9). Complete healing was achieved in 40 legs (91%) after 3 months, and in 43 of the affected legs (98%) in total. The median duration to complete healing was 64 days. There was no difference between the healing times of different etiologies. No local recurrence was observed during the follow-up period, which ranged from 1.8 to 8.7 years (median: 5.11, mean: 5.12). Twelve patients (27%) died within this period due to multimorbidity.

CONCLUSIONS

Following lateral fasciectomy and mesh graft coverage, 43 legs (98%) healed in previously treatment resistant lateral leg ulcers.

Pulse perfusion value predicts eye opening after sevoflurane anaesthesia: an explorative study

The variables measured in modern pulse oximetry apparatuses include a graphical pulse curve and a specified perfusion value (PV) that could be a sensitive marker for detecting differences in sympathetic activity. We hypothesized that there is a correlation between a reduction of PV and the time to eye opening after general anaesthesia. The objective was to investigate whether PV can predict eye opening after sevoflurane anaesthesia. Prospective, explorative clinical study included 20 patients, ASA physical status 1 or 2, at Skåne University Hospital, Lund, Sweden, from November 2012 to January 2013 scheduled for elective breast tumour surgery. A general anaesthesia was delivered with inhalation of oxygen, nitrous oxide and sevoflurane anaesthesia to a depth of 1.2 minimal alveolar concentration. Sevoflurane inspiratory and expiratory concentrations were measured. Bispectral index monitoring, PV as measured by pulse oximeter, heart rate and carbon dioxide were registered at before anaesthesia, 15 min after induction (at 1.2 minimal alveolar concentration), at end of surgery and at eye opening at the end of anaesthesia. PV values were lower before anaesthesia and at eye opening compared to at 15 min after induction and at end of surgery (P < 0.05). The reduction of PV between end of surgery and eye opening was 0.76. We conclude that the pulse oximeter PV could be a useful variable to assess the timing of recovery, in terms of eye opening after a general anaesthesia.

A Review of Current Analgesic Techniques in Cardiac Surgery. Is Epidural Worth it?

In this review we addressed the various analgesic techniques in cardiac surgery, especially regional methods such as thoracic epidural anesthesia (TEA). There are many techniques available for management of postoperative pain after cardiac operation including intravenous administration of analgesic drugs, infiltration of local anesthetics, nerve blocks, and neuroaxial techniques. Although there are many evidences declaring the benefits of neuroaxial blockade in improving postoperative well-being and quality of care in these patients, some studies have revealed limited effect of TEA on overall morbidity and mortality after cardiac surgery. On the other hand, some investigators have raised the concern about epidural hematoma in altered coagulation and risks of infection and local anesthetics toxicity during and after cardiac procedures. In present review, we tried to discuss the most recent arguments in the field of this controversial issue. The final conclusion about either using regional anesthesia in cardiac surgery or not has been assigned to the readers.

Perioperative management of a patient scheduled for bilateral hand transplant

The perioperative management of a patient receiving a bilateral hand transplant is presented. The anesthetic management required careful fluid administration, homeothermic temperature maintenance, and postoperative analgesia. The role of different anesthesia subspecialties is highlighted.

Risks and benefits of thoracic epidural anaesthesia

Thoracic epidural anaesthesia (TEA) reduces cardiac and splanchnic sympathetic activity and thereby influences perioperative function of vital organ systems. A recent meta-analysis suggested that TEA decreased postoperative cardiac morbidity and mortality. TEA appears to ameliorate gut injury in major surgery as long as the systemic haemodynamic effects of TEA are adequately controlled. The functional benefit in fast-track and laparoscopic surgery needs to be clarified. Better pain control with TEA is established in a wide range of surgical procedures. In a setting of advanced surgical techniques, fast-track regimens and a low overall event rate, the number needed to treat to prevent one death by TEA is high. The risk of harm by TEA is even lower, and other methods used to control perioperative pain and stress response also carry specific risks. To optimize the risk-benefit balance of TEA, safe time intervals regarding the use of concomitant anticoagulants and consideration of reduced renal function impairing their elimination must be observed. Infection is a rare complication and is associated with better prognosis. Close monitoring and a predefined algorithm for the diagnosis and treatment of spinal compression or infection are crucial to ensure patient safety with TEA. The risk-benefit balance of analgesia by TEA is favourable and should foster clinical use.

The effects of sympathectomy on finger photoplethysmography and temperature measurements in healthy subjects

BACKGROUND

Photoplethysmography uses light transmission to measure changes in tissue volume. The resulting photoplethysmogram is composed of AC and DC components. Limited data are available on the effects of vasodilation on the AC and the DC components of the photoplethysmograph signal. The aims of our study were (1) to investigate the effects of sympathectomy on different components of the photoplethysmogram, and (2) to compare sympathectomy-induced changes in the photoplethysmogram with changes in peripheral temperature.

METHODS

In 10 healthy subjects, sympathectomy-induced peripheral vasodilation was achieved using an axillary brachial plexus block. The nonblocked arm served as control. We obtained measurements of bilateral continuous measurements of finger blood volume (by photoplethysmography) and finger temperature. We separated the finger photoplethysmogram into its AC and DC components. In addition, we calculated the ratio of AC to DC (AC/DC). All data were recorded until 30 minutes after the end of brachial plexus block. Repeated-measures analysis of variance followed by the Dunnett post hoc test determined the effect of brachial plexus block on the finger photoplethysmogram and finger temperature.

RESULTS

The DC component of the finger photoplethysmogram decreased (vasodilation) significantly (P < 0.0001) after brachial plexus block in the blocked arm starting 2.7 minutes after the block. Average decrease in DC values was -51% ± 19% (95% confidence interval: -61% to -42%) at 30 minutes after the block. None of the other photoplethysmogram components changed significantly from preblock baseline values. On average, the finger temperature increased significantly (P < 0.0001) starting 5.7 minutes after brachial plexus block in the blocked arm. Average increase in temperature was 7.1°C ± 3.8°C (95% confidence interval: 5.1°C-9.0°C) 30 minutes after the block. The DC component of the photoplethysmogram had the highest sensitivity and specificity to predict a successful block.

CONCLUSIONS

This study characterizes sympathectomy-induced changes in the AC and DC components of the finger photoplethysmogram. In this experimental model, we found the DC component to be most sensitive in detecting peripheral vasodilation.

Intestinal effects of thoracic epidural anesthesia

PURPOSE OF REVIEW

Thoracic epidural anesthesia (TEA) is most frequently used after major surgery. However, despite ongoing research, the influence of TEA on the intestinal perioperative pathophysiology is not fully understood.

RECENT FINDINGS

According to recent results, the splanchnic sympathetic activity is reduced during TEA both in animal models and in clinical TEA. The splanchnic sympathetic activity during high TEA is still unknown. Intestinal perfusion effects of TEA are still unclear as the technique and extent of TEA, hemodynamic alteration and size of measurement result in--seemingly--conflicting reports. Postoperative ileus after laparotomy is ameliorated by TEA. Recent findings suggest beneficial effects also after major laparoscopic procedures. Finally, the impact of TEA on the intestinal pathophysiology in critical illness is an area of growing clinical and scientific interest, although this knowledge is just at its beginning.

SUMMARY

Further research concerning the use of TEA in major laparoscopic procedures and its potential to improve or endanger anastomotic healing is warranted. The experimental studies of TEA in critical illness should be expanded.