Changes in the Skin Conductance Monitor as an End Point for Sympathetic Nerve Blocks.

OBJECTIVE: There is a lack of objective methods for determining the achievement of sympathetic block. This study validates the skin conductance monitor (SCM) as an end point indicator of successful sympathetic blockade as compared with traditional monitors. METHODS: This interventional study included 13 patients undergoing 25 lumbar sympathetic blocks to compare time to indication of successful blockade between the SCM indices and traditional measures, clinically visible hyperemia, clinically visible engorgement of veins, subjective skin temperature difference, unilateral thermometry monitoring, bilateral comparative thermometry monitoring, and change in waveform amplitude in pulse oximetry plethysmography, within a 30-minute observation period. Differences in the SCM indices were studied pre- and postblock to validate the SCM. RESULTS: SCM showed substantially greater odds of indicating achievement of sympathetic block in the next moment (i.e., hazard rate) compared with all traditional measures (clinically visible hyperemia, clinically visible engorgement of veins, subjective temperature difference, unilateral thermometry monitoring, bilateral comparative thermometry monitoring, and change in waveform amplitude in pulse oximetry plethysmography; P ≤ 0.011). SCM indicated successful block for all (100%) procedures, while the traditional measures failed to indicate successful blocks in 16-84% of procedures. The SCM indices were significantly higher in preblock compared with postblock measurements (P < 0.005). CONCLUSIONS: This preliminary study suggests that SCM is a more reliable and rapid response indicator of a successful sympathetic blockade when compared with traditional monitors.

A prospective, randomized, controlled trial comparing ultrasound versus nerve stimulator guidance for interscalene block for ambulatory shoulder surgery for postoperative neurological symptoms.

BACKGROUND: Visualization with ultrasound during regional anesthesia may reduce the risk of intraneural injection and subsequent neurological symptoms but has not been formally assessed. Thus, we performed this randomized clinical trial comparing ultrasound versus nerve stimulator-guided interscalene blocks for shoulder arthroscopy to determine whether ultrasound could reduce the incidence of postoperative neurological symptoms. METHODS: Two hundred thirty patients were randomized to a standardized interscalene block with either ultrasound or nerve stimulator with a 5 cm, 22 g Stimuplex insulated needle with 1.5% mepivacaine with 1:300,000 epinephrine and NaCO3 (1 meq/10 mL). A standardized neurological assessment tool (questionnaire and physical examination) designed by a neurologist was administered before surgery (both components), at approximately 1 wk after surgery (questionnaire), and at approximately 4-6 weeks after surgery (both components). Diagnosis of postoperative neurological symptoms was determined by a neurologist blinded to block technique. RESULTS: Two hundred nineteen patients were evaluated. Use of ultrasound decreased the number of needle passes for block performance (1 vs 3, median, P < 0.001), enhanced motor block at the 5-min assessment (P = 0.04) but did not decrease block performance time (5 min for both). No patient required conversion to general anesthesia for failed block, and patient satisfaction was similar in both groups (96% nerve stimulator and 92% ultrasound). The incidence of postoperative neurological symptoms was similar at 1 wk follow-up with 11% (95% CI of 5%-17%) for nerve stimulator and 8% (95% CI of 3%-13%) for ultrasound and was similar at late follow-up with 7% (95% CI of 3%-12%) for nerve stimulator and 6% (95% CI of 2%-11%) for ultrasound. The severity of postoperative neurological symptoms was similar between groups with a median patient rating of moderate. Symptoms were primarily sensory and consisted of pain, tingling, or paresthesias. CONCLUSIONS: Ultrasound reduced the number of needle passes needed to perform interscalene block and enhanced motor block at the 5 min assessment; however, we did not observe significant differences in block failures, patient satisfaction or incidence, and severity of postoperative neurological symptoms.

Nerve localization techniques for interscalene brachial plexus blockade: a prospective, randomized comparison of mechanical paresthesia versus electrical stimulation.

Postoperative neurologic symptoms (PONS) are relatively common after upper extremity orthopedic surgery performed under peripheral neural blockade. In this study, we prospectively compared the incidence of PONS after shoulder surgery under interscalene (IS) block using the electrical stimulation (ES) or mechanical paresthesia (MP) techniques of nerve localization. For patients randomized to the MP group, a 1-in, 23-g long-beveled needle was placed into the IS groove to elicit a paresthesia to the shoulder, arm, elbow, wrist, or hand. For patients randomized to the ES group, a 5-cm, 22-g short-beveled insulated needle was placed into the IS groove to elicit a motor response including flexion or extension of the elbow, wrist, or fingers or deltoid muscle stimulation at a current between 0.2 and 0.5 mA. Each IS block was performed with 50-60 mL of 1.5% mepivacaine containing 1:300,000 epinephrine and 0.1meq/L sodium bicarbonate. Two-hundred-eighteen patients were randomized between the two groups. One patient was lost to follow-up. Twenty-five patients (23%) in the ES group experienced paresthesia during needle insertion. The incidence of PONS using the ES technique was 10.1% (11/109), whereas the incidence with the MP technique was 9.3% (10/108) (not significant). The PONS lasted a median duration of 2 mo, and symptoms in all patients resolved within 12 mo. The success rate, onset time, and patient satisfaction were also comparable between groups. We conclude that the choice of nerve localization technique can be made based on the patient's and anesthesiologist's comfort and preferences and not on concern for the development of PONS.

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.

Effects of steroids on thrombogenic markers in patients undergoing unilateral total knee arthroplasty: a prospective, double-blind, randomized controlled trial.

Venous thromboembolism (VTE) remains an important complication after total knee arthroplasty (TKA). Systemic thrombin generation starts perioperatively. Inflammation, characterized by a rise in interleukin-6 (IL6), initiates the coagulation cascade, but low-dose steroids can reduce post-TKA IL6 levels. This double-blinded, randomized, placebo-controlled study enrolled 30 patients undergoing unilateral TKA to assess the effect of perioperative steroids on serum prothrombin fragment (PF1.2), a marker of thrombin generation, and plasmin-alpha-2-antiplasmin complex (PAP), a marker of fibrinolysis. Study patients received 100 mg of intravenous hydrocortisone 2 h prior to surgery, and controls received normal saline. Blood samples, drawn pre-incision and at 4 h post tourniquet release, were assayed for PF1.2 and PAP. The study group had significantly lower mean PF1.2 at 4 h compared to controls (616 ± 358 pMol/L vs. 936 ± 332 pMol/L, p = 0.037). The mean rise in PF1.2 in the control group was significantly greater compared to the study group (672 ± 173 pMol/L vs. 350 ± 211 pMol/L, p < 0.001). Mean PAP was higher in the study group at 4 h (1639 ± 823 µg/L vs. 1087 ± 536 µg/L), but did not reach statistical significance (p = 0.07). These results may have clinical implications in terms of postoperative VTE risk and management.

Addition of pregabalin to multimodal analgesic therapy following ankle surgery: a randomized double-blind, placebo-controlled trial.

BACKGROUND AND OBJECTIVES: Pregabalin is often used as a perioperative analgesic adjunct; some studies show benefit, but others do not. Adverse effects, such as confusion and sedation, have been attributed to perioperative use of pregabalin. We tested the hypothesis that pregabalin, when used as part of a multimodal analgesic regimen, reduces the duration of moderate to severe pain in the first 24 hrs following foot or ankle surgery. Secondary outcomes included measures of opioid and pregabalin adverse effects. METHODS: Sixty patients scheduled for hospital admission after foot or ankle surgery entered this randomized, double-blind, placebo-controlled trial. Patients received a neuraxial anesthetic, a popliteal fossa sciatic nerve block using 30 mL 0.375% bupivacaine with clonidine 100 µg and epinephrine, a saphenous nerve block, postoperative hydromorphone intravenous patient-controlled analgesia, and oral analgesics (oxycodone/acetaminophen). Patients were randomized to receive pregabalin (100 mg preoperatively, then 50 mg every 12 hrs) or a placebo for 3 days. The primary outcome was the number of hours that patients reported moderate to severe pain. RESULTS: Both groups reported a similar number of hours of moderate to severe pain during the first 24 hrs: 4.1 (SD, 4.1) hrs (pregabalin) versus 4.5 (SD, 3.5) hrs (placebo). Pain scores, opioid use, and adverse effects were also similar in both groups. CONCLUSIONS: No clinical benefit was obtained from perioperative administration of pregabalin (100 mg preoperative, then 50 mg every 12 hrs) as part of a multimodal postoperative analgesic regimen following foot and ankle surgery.

The utility of urine desmosine as a marker of lung injury in spine surgery.

The objective of this prospective observational study was to determine if urine desmosine levels, a marker of lung injury, increase in response to the periopreative insults of anterior and posterior spine surgery. Desmosine, a stable breakdown product of elastin, has been proposed as a surrogate marker of lung injury in patients with COPD, tobacco use, and ARDS. We recently evaluated this marker in patients undergoing knee surgery, but the utility of desmosine as a marker of lung injury in patients undergoing spine surgery remains unstudied. In this study, we enrolled ten consecutive patients, who underwent anterior/posterior spine surgery. Patient demographics and perioperative data were recorded. Urine samples were collected at baseline, 1 day, and 3 days postoperatively and analyzed for levels of desmosine using a previously validated radioimmunoassay. Desmosine levels were 35.9 ± 18.2 pmol/mg creatinine at baseline, 38.7 ± 11 pmol/mg creatinine on postoperative day 1, and 70.5 ± 49.1 pmol/mg creatinine on postoperative day 3, respectively. Desmosine/creatinine ratios measured on day 3 postoperatively were significantly elevated compared to levels at baseline, and represented a 96.3% increase. No difference was seen between levels at baseline and day 1 postoperatively. In conclusion, we were able to show a significant increase in urine desmosine levels associated with anterior/posterior spine surgery. In the context of previous studies, our findings suggest that desmosine may be a marker of lung injury in this setting. However, further research is warranted for validation and correlation of desmosine levels to clinical markers and various degrees of lung injury.

Correlation between centrally versus peripherally transduced venous pressure in prone patients undergoing posterior spine surgery.

STUDY DESIGN: Prospective clinical observational study. OBJECTIVE: To evaluate the correlation and agreement between peripherally and centrally transduced venous pressures in prone spine surgery patients. SUMMARY OF BACKGROUND DATA: In view of a variety of potential complications associated with the placement of central venous lines for the purpose of central venous pressure (CVP) monitoring, a number of authors have suggested that the use of peripherally transduced pressures (PVP) instead may yield similar results. Data confirming the validity of this technique for the purpose of intravascular fluid volume monitoring in prone patients undergoing spine surgery remain scarce. METHODS: After protocol approval by the internal review board, we enrolled 40 patients who underwent spine surgery in the prone position. CVP and PVP were recorded simultaneously. The data pairs were analyzed for correlation. Bland and Altman plots were created to evaluate the degree of agreement between the 2 modes of venous pressure monitoring. RESULTS: A total of 1275 data pairs were collected. The mean PVP was 17.55 mm Hg +/- 4.93 mm Hg and the mean CVP 15.52 mm Hg +/- 4.77 mm Hg (P < 0.001), thus yielding a mean difference of 2.04 mm Hg +/- 1.39 mm Hg. PVP and CVP correlated well over a wide range of pressures (r = 0.949, r = 0.920 [P < 0.001]). A high level of agreement was found between both methods of venous pressure measurement. CONCLUSION: CVP and PVP correlate well under conditions associated with prone spine surgery. With a high level of agreement found in this study, PVP may represent an attractive alternative to CVP monitoring to assess fluid volume trends intraoperatively.