Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
and may have received sedative medication. Hence, for reasons related to safety and practicality, assessments were performed in a hospital stretcher in the 30degree head-up position—both before and after brachial plexus blockade. Dr Johnston is correct that we did not pursue formal pulmonary function testing for patients enrolled in our trial. Although the latter would have raised obvious feasibility issues given our trial’s “real-world” context, conditions associated with abnormal spirometry represented exclusion criteria, including any history of obstructive or restrictive pulmonary disease, neuromuscular disease, body mass index greater than 35 kg/m2, and any known or suspected phrenic nerve palsy or diaphragmatic dysfunction.1 As stated, our analysis was based on an intention-to-treat approach in that preblock diaphragmatic ultrasonography was performed and baseline measurements were taken; were a patient found to have undiagnosed diaphragmatic dysfunction during the preblock scan, such a patient was to be included in the analysis. However, in our cohort of 64 patients, there were no such instances. Regarding ultrasound probe positioning, all ultrasonographic diaphragm scans in our randomized controlled trial were performed by a single investigator (S.D.P.) using the same approach for all patients in both groups, and all reasonable efforts were taken to diligently maintain consistent ultrasound windows preblock and postblock to extract the highest-quality data. In brief, patients were maintained in a constant position for all preblock and postblock assessments. Stretchers were not readjusted, and, whenever possible, the probe was positioned in the same location and at the same approximate angle for all assessments. As Dr Johnston would be aware, in any event of a real-time ultrasound examination of a live patient, the process is dynamic. This inherently requires ongoing small adjustments of probe position and beam angulation to capture the optimal image for measurement. When hemidiaphragmatic paralysis caused by phrenic nerve blockade occurs, there is a resultant cephalad migration of the hemidiaphragm as the muscle loses tone and the abdominal contents exert cephalad pressure from below. In such instances, careful probe repositioning and adjustment of beam angle are expected to be required to regain visualization of the diaphragm. In our experience, this in fact is another “soft sign” of diaphragmatic dysfunction. Simply placing the probe at the exact same (and fixed) position and angle after the study intervention (brachial plexus block) as was used before would
not take into account the dynamic nature of the process in question as the relevant organs move in 3 dimensions of space. Like any ultrasound technique, constant subtle adjustments of the probe are required to ensure optimal imaging of the structure of interest. In the context of a randomized trial, the inherent assumption is that such subtleties are equally distributed in both groups. Lastly, with regard to other physical parameters that may influence diaphragmatic excursion during respiration when measured by M-mode ultrasound, specifically height and FEV1/FVC ratio, we fully agree that these are important for diaphragmatic function. However, the aim of our trial was not to compare study subjects with population norms for diaphragmatic excursion; rather, the modality of M-mode ultrasound was used to readily assess diaphragmatic dysfunction postblock by comparing each patient with their own preblock baseline measurements. This distinction is important for the understanding of the methodology chosen to ascertain if there had been a significant change after the study intervention. Potential outliers in absolute diaphragmatic excursion such as may be observed in extremely tall men,3 for example, would be expected to be accounted for by this approach. Notwithstanding these considerations, baseline demographic data, including sex, weight, and body mass index (cf Table 1)1, were comparable between both groups; furthermore, although the primary end point was based on normalized “voluntary sniff ” (VS) test results, there were no differences between the groups in baseline raw VS test parameters (cf Fig. 3A; P = 0.62 [value not shown in the article]).
Steven D. Petrar, MD, FRCPC Department of Anesthesia St. Paul’s Hospital Department of Anesthesiology, Pharmacology & Therapeutics The University of British Columbia Vancouver, British Columbia, Canada
Michael E. Seltenrich, MD, FRCPC Department of Anesthesia Nanaimo Regional General Hospital Nanaimo, British Columbia, Canada
Stephen J. Head, MD, FRCPC Stephan K. W. Schwarz, MD, PhD, FRCPC Division of Regional Anesthesia St. Paul’s Hospital Department of Anesthesiology, Pharmacology & Therapeutics The University of British Columbia Vancouver, British Columbia, Canada
The authors declare no conflict of interest.
© 2015 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
REFERENCES 1. Petrar SD, Seltenrich ME, Head SJ, Schwarz SKW. Hemidiaphragmatic paralysis following ultrasound-guided supraclavicular versus infraclavicular brachial plexus blockade: a randomized clinical trial. Reg Anesth Pain Med. 2015;40:133–138. 2. Johnston D. Considerations during M-mode hemidiaphragm scanning. Reg Anesth Pain Med. 2015;40:394. 3. Boussuges A, Gole Y, Blanc P. Diaphragmatic motion studied by M-mode ultrasonography: methods, reproducibility, and normal values. Chest. 2009;135:391–400.
Is Prevention Better Than Cure? Local Anesthetics in Brugada Syndrome Accepted for publication: April 20, 2015. To the Editor: e read with extreme interest the letter of Soberón and colleagues1 on the performance of a peripheral nerve block in a patient with propionic acidemia. Like mitochondrial disorders, patients with cardiac channelopathies may have a lower threshold for systemic toxicity after local anesthetic (LA) administration. We recently preemptively administered 20% lipid emulsion (ILE) in a patient with Brugada syndrome (BrS) undergoing a peripheral nerve block for orthopedic surgery at the University Hospital of Padua. The patient consented to the publication of her case. A 53-year-old, 54-kg woman with hypertension, hypercholesterolemia, smoking habit, and BrS was scheduled for excision of an elbow neoformation. Brugada syndrome was diagnosed years earlier, but she had never suffered cardiac symptoms or arrest. Her medical therapy included cardiac aspirin, olmesartan, and pravastatin. The physical examination and laboratory tests were unremarkable, and there was no family history of sudden cardiac death. We provided a thorough explanation of potential risks, and the patient eventually consented for peripheral nerve block. In the operating room, noninvasive monitoring was begun, a large peripheral venous access was secured, and the patient was premedicated with midazolam 2 mg and fentanyl 100 μg. External defibrillator pads were placed as well, given the risk of cardiac arrhythmias during anesthesia. We performed an ultrasound-guided brachial plexus block through the axillary approach with 18 mL of ropivacaine 0.375%.
W
395
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
Letters to the Editor
Concomitantly, we started the infusion of ILE (Lipovenos; Fresenius Kabl, San Joaquin, Santiago, Chile) at 0.25 mL kg−1 min. Lipid infusion was continued for 40 minutes with an overall administration of 540 mL (10 mL/kg). Surgery was uneventful, and the patient was pain-free in the postoperative period. Cardiac monitoring was extended to the day after surgery without incident. Brugada syndrome is a hereditable cardiac arrhythmia determined by mutations of the cardiac sodium channel’s gene. It affects 5 to 66 in 10,000 worldwide and is an important cause of sudden death in relatively young population. Its electrocardiographic aspects are still debated.2,3 Pathogenic mechanisms are still undetermined, but exposure to several drugs, especially sodium-channel blockers such as LA, may trigger electrocardiographic abnormalities, life-threatening arrhythmias, and sudden death in affected patients.2 Indeed, despite little clinical evidence, LAs are potentially arrhythmogenic in BrS, and severe arrhythmias have been described with ropivacaine, as well.4 Therefore, these patients might be particularly prone to develop LA systemic toxicity (LAST). Ultrasound guidance, aspiration before injection, the use of a low dose of LA, and the prompt availability of resuscitation facilities are probably the most important tools for minimizing the risk of adverse events in BrS patients undergoing peripheral nerve blocks. To our knowledge, this is the first report proposing the preemptive use of ILE in LAST high-risk patients. We empirically started ILE infusion immediately before the nerve block was performed at the speed currently recommended for the treatment of LAST.5 Lipid emulsion has been proven to accelerate the unbinding of LA from crucial ionotropic cardiac channels and to have an inotropic effect even in the absence of toxicity.6 This may be beneficial in those patients, and we ponder whether it is reasonable to administer ILE only in case of overt LA toxicity or if its preemptive administration may reduce the risk of LA toxicity in BrS and in other LAST high-risk patients. Francesco Vasques, MD Department of Medicine (DIMED) Anesthesia and Intensive Care Unit Padua University Hospital Padova, Italy
Guido Di Gregorio, MD, PhD Astrid Ursula Behr, MD Istituto di Anestesia e Rianimazione Azienda Ospedaliera di Padova Padova, Italy
The authors declare no conflict of interest.
396
REFERENCES 1. Soberón JR1, Elliott CE, Bland KS, Weinberg GL. Peripheral nerve block in a patient with propionic acidemia. Reg Anesth Pain Med. 2014;39:560–561. 2. Wilde AA, Antzelevitch C, Borggrefe M, et al. Proposed diagnostic criteria for the Brugada syndrome: consensus report. Circulation. 2002;106:2514–2519. 3. Brugada P. On the intriguing phenotypic manifestations of Brugada syndrome and the diagnostic value of the electrocardiogram. J Am Coll Cardiol. 2011;58:2299–2300. 4. Fujiwara Y, Shibata Y, Kurokawa S, et al. Ventricular tachycardia in a patient with Brugada syndrome during general anesthesia combined with thoracic paravertebral block. Anesth Analg. 2006;102:1590–1591. 5. Neal JM, Bernards CM, Butterworth JF, et al. ASRA practice advisory on local anesthetic systemic toxicity. Reg Anesth Pain Med. 2010;35:152–161. 6. Fettiplace MR, Lis K, Ripper R, et al. Multi-modal contributions to detoxification of acute pharmacotoxicity by a triglyceride micro-emulsion. J Control Release. 2014;198:62–70.
Risk of Bleeding Associated With the Combination of Thromboprophylaxis and Peripheral Nerve Blocks Role of the Technique Accepted for publication: December 9, 2014. To the Editor: e read with interest the article by Idestrup et al1 on the safety of the combination of rivaroxaban use for thromboprophylaxis and continuous femoral nerve block. We would like to congratulate the authors for documenting that this combination appears to be safe. Although no major bleeding episodes were recorded, the authors reported a 26% incidence of local oozing on postoperative day 2, a 12.1% incidence of local ecchymosis on postoperative day 3, and a 0.03% incidence of “palpable mass” attributed to local bleeding. We are in the process of reporting similar data and can confirm that no major bleeding should be expected from such a combination. In our experience, using a smaller and less traumatic technique (ultrasound alone or combined with a 18-gauge stimulating needle), we have observed that minor bleeding at the site was the result of the performance of the nerve block alone rather than the combination, as the bleeding developed before initiation of the
W
thromboprophylaxis. Under these conditions, we would like to suggest that trauma associated with the performance of the block is the most important cause of the resulting minor bleeding reported in this article. Idestrup et al used a StimuCath continuous nerve block catheter from Arrow, which includes a 17-gauge introducing stimulating needle. This, combined with the fact that placement of a stimulating catheter requires more time/trauma for catheter positioning compared with placement of a nonstimulating catheter such as the one we use (B.Braun), less local bleeding should be expected when a continuous femoral nerve block is performed using ultrasound alone and/or ultrasound combined with a stimulating 18-gauge introducing needle. Trauma is a well-established possible cause of major bleeding following the placement of block alone or in combination with anticoagulation.2,3 According to the authors’ protocol, only 1 dose of rivaroxaban was administered before the perineural catheter was removed, whereas at least 2 to 3 days are required to achieve “a steady state.” We have absolutely no doubt that the authors developed their protocol to mimic recommendations from previously published guidelines, but as reported by Benzon et al,4 the inhibition of factor Xa is only between 22% to 68% following the administration of 1 dose. Does the amount of factor Xa allow a clot to develop? Do we not accept that at least an 80% decrease is required to alter coagulation?5 Until now, the assumption was that a decrease of at least 80% is required to prevent a normal clot from developing. Again, what is the rationale for a 20-hour drugfree interval between the administration of rivaroxaban and the removal of the perineural catheter? Is an interval of 2 half-lives or more really required?6,7 Jacques E. Chelly, MD, PhD, MBA Department of Anesthesiology University of Pittsburgh Medical Center Pittsburgh, Pennsylvania
The author declares no conflict of interest. REFERENCES 1. Idestrup C, Sawhney M, Nix C, Kiss A. The incidence of hematoma formation in patients with continuous femoral catheters following total knee arthroplasty while receiving rivaroxaban as thromboprophylaxis: an observational study. Reg Anesth Pain Med. 2014;39:414–417. 2. Weller RS, Gerancher JC, Crews JC, Wade KL. Extensive retroperitoneal hematoma without neurologic deficit in two patients who underwent lumbar plexus block and were later anticoagulated. Anesthesiology. 2003;98:581–585.
© 2015 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
and may have received sedative medication. Hence, for reasons related to safety and practicality, assessments were performed in a hospital stretcher in the 30degree head-up position—both before and after brachial plexus blockade. Dr Johnston is correct that we did not pursue formal pulmonary function testing for patients enrolled in our trial. Although the latter would have raised obvious feasibility issues given our trial’s “real-world” context, conditions associated with abnormal spirometry represented exclusion criteria, including any history of obstructive or restrictive pulmonary disease, neuromuscular disease, body mass index greater than 35 kg/m2, and any known or suspected phrenic nerve palsy or diaphragmatic dysfunction.1 As stated, our analysis was based on an intention-to-treat approach in that preblock diaphragmatic ultrasonography was performed and baseline measurements were taken; were a patient found to have undiagnosed diaphragmatic dysfunction during the preblock scan, such a patient was to be included in the analysis. However, in our cohort of 64 patients, there were no such instances. Regarding ultrasound probe positioning, all ultrasonographic diaphragm scans in our randomized controlled trial were performed by a single investigator (S.D.P.) using the same approach for all patients in both groups, and all reasonable efforts were taken to diligently maintain consistent ultrasound windows preblock and postblock to extract the highest-quality data. In brief, patients were maintained in a constant position for all preblock and postblock assessments. Stretchers were not readjusted, and, whenever possible, the probe was positioned in the same location and at the same approximate angle for all assessments. As Dr Johnston would be aware, in any event of a real-time ultrasound examination of a live patient, the process is dynamic. This inherently requires ongoing small adjustments of probe position and beam angulation to capture the optimal image for measurement. When hemidiaphragmatic paralysis caused by phrenic nerve blockade occurs, there is a resultant cephalad migration of the hemidiaphragm as the muscle loses tone and the abdominal contents exert cephalad pressure from below. In such instances, careful probe repositioning and adjustment of beam angle are expected to be required to regain visualization of the diaphragm. In our experience, this in fact is another “soft sign” of diaphragmatic dysfunction. Simply placing the probe at the exact same (and fixed) position and angle after the study intervention (brachial plexus block) as was used before would
not take into account the dynamic nature of the process in question as the relevant organs move in 3 dimensions of space. Like any ultrasound technique, constant subtle adjustments of the probe are required to ensure optimal imaging of the structure of interest. In the context of a randomized trial, the inherent assumption is that such subtleties are equally distributed in both groups. Lastly, with regard to other physical parameters that may influence diaphragmatic excursion during respiration when measured by M-mode ultrasound, specifically height and FEV1/FVC ratio, we fully agree that these are important for diaphragmatic function. However, the aim of our trial was not to compare study subjects with population norms for diaphragmatic excursion; rather, the modality of M-mode ultrasound was used to readily assess diaphragmatic dysfunction postblock by comparing each patient with their own preblock baseline measurements. This distinction is important for the understanding of the methodology chosen to ascertain if there had been a significant change after the study intervention. Potential outliers in absolute diaphragmatic excursion such as may be observed in extremely tall men,3 for example, would be expected to be accounted for by this approach. Notwithstanding these considerations, baseline demographic data, including sex, weight, and body mass index (cf Table 1)1, were comparable between both groups; furthermore, although the primary end point was based on normalized “voluntary sniff ” (VS) test results, there were no differences between the groups in baseline raw VS test parameters (cf Fig. 3A; P = 0.62 [value not shown in the article]).
Steven D. Petrar, MD, FRCPC Department of Anesthesia St. Paul’s Hospital Department of Anesthesiology, Pharmacology & Therapeutics The University of British Columbia Vancouver, British Columbia, Canada
Michael E. Seltenrich, MD, FRCPC Department of Anesthesia Nanaimo Regional General Hospital Nanaimo, British Columbia, Canada
Stephen J. Head, MD, FRCPC Stephan K. W. Schwarz, MD, PhD, FRCPC Division of Regional Anesthesia St. Paul’s Hospital Department of Anesthesiology, Pharmacology & Therapeutics The University of British Columbia Vancouver, British Columbia, Canada
The authors declare no conflict of interest.
© 2015 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
REFERENCES 1. Petrar SD, Seltenrich ME, Head SJ, Schwarz SKW. Hemidiaphragmatic paralysis following ultrasound-guided supraclavicular versus infraclavicular brachial plexus blockade: a randomized clinical trial. Reg Anesth Pain Med. 2015;40:133–138. 2. Johnston D. Considerations during M-mode hemidiaphragm scanning. Reg Anesth Pain Med. 2015;40:394. 3. Boussuges A, Gole Y, Blanc P. Diaphragmatic motion studied by M-mode ultrasonography: methods, reproducibility, and normal values. Chest. 2009;135:391–400.
Is Prevention Better Than Cure? Local Anesthetics in Brugada Syndrome Accepted for publication: April 20, 2015. To the Editor: e read with extreme interest the letter of Soberón and colleagues1 on the performance of a peripheral nerve block in a patient with propionic acidemia. Like mitochondrial disorders, patients with cardiac channelopathies may have a lower threshold for systemic toxicity after local anesthetic (LA) administration. We recently preemptively administered 20% lipid emulsion (ILE) in a patient with Brugada syndrome (BrS) undergoing a peripheral nerve block for orthopedic surgery at the University Hospital of Padua. The patient consented to the publication of her case. A 53-year-old, 54-kg woman with hypertension, hypercholesterolemia, smoking habit, and BrS was scheduled for excision of an elbow neoformation. Brugada syndrome was diagnosed years earlier, but she had never suffered cardiac symptoms or arrest. Her medical therapy included cardiac aspirin, olmesartan, and pravastatin. The physical examination and laboratory tests were unremarkable, and there was no family history of sudden cardiac death. We provided a thorough explanation of potential risks, and the patient eventually consented for peripheral nerve block. In the operating room, noninvasive monitoring was begun, a large peripheral venous access was secured, and the patient was premedicated with midazolam 2 mg and fentanyl 100 μg. External defibrillator pads were placed as well, given the risk of cardiac arrhythmias during anesthesia. We performed an ultrasound-guided brachial plexus block through the axillary approach with 18 mL of ropivacaine 0.375%.
W
395
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
Letters to the Editor
Concomitantly, we started the infusion of ILE (Lipovenos; Fresenius Kabl, San Joaquin, Santiago, Chile) at 0.25 mL kg−1 min. Lipid infusion was continued for 40 minutes with an overall administration of 540 mL (10 mL/kg). Surgery was uneventful, and the patient was pain-free in the postoperative period. Cardiac monitoring was extended to the day after surgery without incident. Brugada syndrome is a hereditable cardiac arrhythmia determined by mutations of the cardiac sodium channel’s gene. It affects 5 to 66 in 10,000 worldwide and is an important cause of sudden death in relatively young population. Its electrocardiographic aspects are still debated.2,3 Pathogenic mechanisms are still undetermined, but exposure to several drugs, especially sodium-channel blockers such as LA, may trigger electrocardiographic abnormalities, life-threatening arrhythmias, and sudden death in affected patients.2 Indeed, despite little clinical evidence, LAs are potentially arrhythmogenic in BrS, and severe arrhythmias have been described with ropivacaine, as well.4 Therefore, these patients might be particularly prone to develop LA systemic toxicity (LAST). Ultrasound guidance, aspiration before injection, the use of a low dose of LA, and the prompt availability of resuscitation facilities are probably the most important tools for minimizing the risk of adverse events in BrS patients undergoing peripheral nerve blocks. To our knowledge, this is the first report proposing the preemptive use of ILE in LAST high-risk patients. We empirically started ILE infusion immediately before the nerve block was performed at the speed currently recommended for the treatment of LAST.5 Lipid emulsion has been proven to accelerate the unbinding of LA from crucial ionotropic cardiac channels and to have an inotropic effect even in the absence of toxicity.6 This may be beneficial in those patients, and we ponder whether it is reasonable to administer ILE only in case of overt LA toxicity or if its preemptive administration may reduce the risk of LA toxicity in BrS and in other LAST high-risk patients. Francesco Vasques, MD Department of Medicine (DIMED) Anesthesia and Intensive Care Unit Padua University Hospital Padova, Italy
Guido Di Gregorio, MD, PhD Astrid Ursula Behr, MD Istituto di Anestesia e Rianimazione Azienda Ospedaliera di Padova Padova, Italy
The authors declare no conflict of interest.
396
REFERENCES 1. Soberón JR1, Elliott CE, Bland KS, Weinberg GL. Peripheral nerve block in a patient with propionic acidemia. Reg Anesth Pain Med. 2014;39:560–561. 2. Wilde AA, Antzelevitch C, Borggrefe M, et al. Proposed diagnostic criteria for the Brugada syndrome: consensus report. Circulation. 2002;106:2514–2519. 3. Brugada P. On the intriguing phenotypic manifestations of Brugada syndrome and the diagnostic value of the electrocardiogram. J Am Coll Cardiol. 2011;58:2299–2300. 4. Fujiwara Y, Shibata Y, Kurokawa S, et al. Ventricular tachycardia in a patient with Brugada syndrome during general anesthesia combined with thoracic paravertebral block. Anesth Analg. 2006;102:1590–1591. 5. Neal JM, Bernards CM, Butterworth JF, et al. ASRA practice advisory on local anesthetic systemic toxicity. Reg Anesth Pain Med. 2010;35:152–161. 6. Fettiplace MR, Lis K, Ripper R, et al. Multi-modal contributions to detoxification of acute pharmacotoxicity by a triglyceride micro-emulsion. J Control Release. 2014;198:62–70.
Risk of Bleeding Associated With the Combination of Thromboprophylaxis and Peripheral Nerve Blocks Role of the Technique Accepted for publication: December 9, 2014. To the Editor: e read with interest the article by Idestrup et al1 on the safety of the combination of rivaroxaban use for thromboprophylaxis and continuous femoral nerve block. We would like to congratulate the authors for documenting that this combination appears to be safe. Although no major bleeding episodes were recorded, the authors reported a 26% incidence of local oozing on postoperative day 2, a 12.1% incidence of local ecchymosis on postoperative day 3, and a 0.03% incidence of “palpable mass” attributed to local bleeding. We are in the process of reporting similar data and can confirm that no major bleeding should be expected from such a combination. In our experience, using a smaller and less traumatic technique (ultrasound alone or combined with a 18-gauge stimulating needle), we have observed that minor bleeding at the site was the result of the performance of the nerve block alone rather than the combination, as the bleeding developed before initiation of the
W
thromboprophylaxis. Under these conditions, we would like to suggest that trauma associated with the performance of the block is the most important cause of the resulting minor bleeding reported in this article. Idestrup et al used a StimuCath continuous nerve block catheter from Arrow, which includes a 17-gauge introducing stimulating needle. This, combined with the fact that placement of a stimulating catheter requires more time/trauma for catheter positioning compared with placement of a nonstimulating catheter such as the one we use (B.Braun), less local bleeding should be expected when a continuous femoral nerve block is performed using ultrasound alone and/or ultrasound combined with a stimulating 18-gauge introducing needle. Trauma is a well-established possible cause of major bleeding following the placement of block alone or in combination with anticoagulation.2,3 According to the authors’ protocol, only 1 dose of rivaroxaban was administered before the perineural catheter was removed, whereas at least 2 to 3 days are required to achieve “a steady state.” We have absolutely no doubt that the authors developed their protocol to mimic recommendations from previously published guidelines, but as reported by Benzon et al,4 the inhibition of factor Xa is only between 22% to 68% following the administration of 1 dose. Does the amount of factor Xa allow a clot to develop? Do we not accept that at least an 80% decrease is required to alter coagulation?5 Until now, the assumption was that a decrease of at least 80% is required to prevent a normal clot from developing. Again, what is the rationale for a 20-hour drugfree interval between the administration of rivaroxaban and the removal of the perineural catheter? Is an interval of 2 half-lives or more really required?6,7 Jacques E. Chelly, MD, PhD, MBA Department of Anesthesiology University of Pittsburgh Medical Center Pittsburgh, Pennsylvania
The author declares no conflict of interest. REFERENCES 1. Idestrup C, Sawhney M, Nix C, Kiss A. The incidence of hematoma formation in patients with continuous femoral catheters following total knee arthroplasty while receiving rivaroxaban as thromboprophylaxis: an observational study. Reg Anesth Pain Med. 2014;39:414–417. 2. Weller RS, Gerancher JC, Crews JC, Wade KL. Extensive retroperitoneal hematoma without neurologic deficit in two patients who underwent lumbar plexus block and were later anticoagulated. Anesthesiology. 2003;98:581–585.
© 2015 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
