E
LETTERS TO THE EDITOR
Transversus Abdominis Plane Blocks and Systemic Absorption To the Editor
D
e Oliveira Jr et al.1 recently performed a meta-analysis on the effectiveness of transversus abdominis plane (TAP) blocks in patients undergoing laparoscopic surgery and concluded that these blocks were effective, worked best when performed preoperatively, and had greater opioidsparing effects at 24 hours with larger injected doses. Although these conclusions might be true, the reviewed studies also support the hypothesis that systemic local anesthetics can decrease postoperative pain. None of the reviewed studies controlled for systemic absorption of the local anesthetic. Therefore, whether these benefits are a result of where the amide anesthetics are deposited or a result of their systemic absorptions remains unanswered. Large doses of amide anesthetics have significant systemic effects.2 Lidocaine2 and ropivacaine3 in addition to their anesthetic action both share antiinflammatory properties. Latzke et al.4 demonstrated in healthy volunteers that a TAP block with 150 mg ropivacaine can result in significant concentrations of plasma ropivacaine. Additionally, tissue concentrations remote from the injection site in some subjects were comparable with the tissue concentrations near the injection site, suggesting that a reverse distribution from plasma to remote tissue occurred. Others have demonstrated significant serum concentrations of ropivacaine lasting >12 hours postblock.5 The systemic effects would be greater with a larger absorbed dose, and this meta-analysis demonstrated an increased dose effect at 24 hours. Lidocaine given only during the perioperative period has opioid-sparing effects and is associated with earlier hospital discharge even days after the infusion is stopped.2,6 Serum lidocaine levels in patients benefitting from lidocaine in 1 trial ranged between 1.3 and 3.7 μg/mL.2 Because ropivacaine has 3.6 to 4 times the anesthetic potency of lidocaine,7 these concentrations are significantly less potent than the mean serum ropivacaine concentrations seen in healthy volunteers after a TAP block (Cmax, 1.88 μg/mL mean).4 De Oliveira Jr et al.1 demonstrated an opioid-sparing effect of ropivacaine administered during laparoscopy. This meta-analysis and the included studies do not provide evidence that this dose of amide anesthetic has to be given in the form of a TAP block. Controlled studies demonstrating that the benefits seen are indeed from the block and not systemic absorption have yet to be performed. Scott Groudine, MD Department of Anesthesiology Albany Medical College Albany, New York [email protected] REFERENCES 1. De Oliveira GS Jr, Castro-Alves LJ, Nader A, Kendall MC, McCarthy RJ. Transversus abdominis plane block to ameliorate postoperative pain outcomes after laparoscopic surgery: a meta-analysis of randomized controlled trials. Anesth Analg 2014;118:454–63 Copyright © 2014 International Anesthesia Research Society DOI: 10.1213/ANE.0000000000000327
1002 www.anesthesia-analgesia.org
2. Groudine SB, Fisher HA, Kaufman RP Jr, Patel MK, Wilkins LJ, Mehta SA, Lumb PD. Intravenous lidocaine speeds the return of bowel function, decreases postoperative pain, and shortens hospital stay in patients undergoing radical retropubic prostatectomy. Anesth Analg 1998;86:235–9 3. Blumenthal S, Borgeat A, Pasch T, Reyes L, Booy C, Lambert M, Schimmer RC, Beck-Schimmer B. Ropivacaine decreases inflammation in experimental endotoxin-induced lung injury. Anesthesiology 2006;104:961–9 4. Latzke D, Marhofer P, Kettner SC, Koppatz K, Turnheim K, Lackner E, Sauermann R, Müller M, Zeitlinger M. Pharmacokinetics of the local anesthetic ropivacaine after transversus abdominis plane block in healthy volunteers. Eur J Clin Pharmacol 2012;68:419–25 5. Griffiths JD, Barron FA, Grant S, Bjorksten AR, Hebbard P, Royse CF. Plasma ropivacaine concentrations after ultrasoundguided transversus abdominis plane block. Br J Anaesth 2010;105:853–6 6. Marret E, Rolin M, Beaussier M, Bonnet F. Meta-analysis of intravenous lidocaine and postoperative recovery after abdominal surgery. Br J Surg 2008;95:1331–8 7. Lin Y, Liu SS. Local anesthetics. In: Barash PG, ed. Clinical Anesthesia. 7th ed. Philadelphia, PA: Wolters Kluwer/ Lippincott Williams & Wilkins, 2013:567 DOI: 10.1213/ANE.0000000000000327
Facilitating Lung Collapse During One Lung Ventilation Can Be Rational To the Editor
I
n reporting the results of their study showing the benefit of including nitrous oxide in the ventilating gas mixture before the onset of one-lung ventilation (OLV), Yoshimura et al.1 are to be commended for including bar graphs to present the relevant key findings in all 50 patients studied. The demonstrated “scatter” of lung deflation scores at 1, 5, and 10 minutes very likely reflects the considerable variation in the physiology and pathophysiology of patients undergoing thoracic surgery. Their use of a suction pressure of 10 cm H2O applied to the blocker lumen for 1 minute during surgical opening of the pleura highlights an issue for future risk–benefit studies. These will be complicated by the markedly varying volumes of alveolar gas which might be suctioned in this group of patients before the onset of small airways closure.2 Where prompt collapse of the nonventilated lung is especially advantageous, as in thoracoscopic surgery, consideration should be given to momentarily ceasing mechanical ventilation at the time OLV is initiated. This is relevant with the use of both bronchial blockers and double-lumen tubes (DLTs). With blockers, it will enable OLV to be initiated predictably at end expiration rather than possibly during the inspiratory phase of mechanical ventilation. A delay in balloon inflation will result in an additional degree of elastic recoil lung collapse,3 albeit in both lungs, before the onset of the subsequent absorption atelectasis.1 With DLTs, an oxygen source such as a commercially available, nonpressurized oxygen continuous positive airway pressure system should be attached to the airway of the nonventilated lung October 2014 • Volume 119 • Number 4
Letters to the Editor
when the DLT connector is clamped off as a precursor to initiating OLV. This action will ensure that a potentially large volume of ambient air, with slowly diffusing nitrogen,4 will be prevented from “washing” into the nonventilated lung with each ongoing respiratory excursion of the ventilated lung before the pleura is opened.5 The airway should NOT be left “open to air”! John Pfitzner, FRCA Department of Anaesthesia The Queen Elizabeth Hospital Woodville, South Australia, Australia [email protected] REFERENCES 1. Yoshimura T, Ueda K, Kakinuma A, Sawai J, Nakata Y. Bronchial blocker lung collapse technique: nitrous oxide for facilitating lung collapse during one-lung ventilation with a bronchial blocker. Anesth Analg 2014;118:666–70 2. Pfitzner J, Peacock MJ, Harris RJ. Speed of collapse of the nonventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung. Anaesthesia 2001;56:940–6 3. Young Yoo J, Hee Kim D, Choi H, Kim K, Jeong Chae Y, Yong Park S. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a doublelumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth [Epub ahead of print] 4. Ko R, McRae K, Darling G, Waddell TK, McGlade D, Cheung K, Katz J, Slinger P. The use of air in the inspired gas mixture during two-lung ventilation delays lung collapse during one-lung ventilation. Anesth Analg 2009;108:1092–6 5. Pfitzner J, Peacock MJ, McAleer PT. Gas movement in the nonventilated lung at the onset of single-lung ventilation for videoassisted thoracoscopy. Anaesthesia 1999;54:437–43 DOI: 10.1213/ANE.0000000000000336
In Response We agree with Dr. Pfitzner1 that the “scatter” of lung deflation scores likely reflects the variation in the physiology and pathophysiology of patients in our study2 even though lung function tests showed that there was no difference between the 2 study groups. We understand the concern that markedly varying volumes of alveolar gas were suctioned before the onset of small airway closure, which might have confounded lung deflation scores. However, the level of suction used in our study was low and the Arndt® bronchial blocker (Cook® Critical Care, Bloomington, IN) suction channel had high flow resistance due to a small caliber size and diameter; therefore, it is unlikely that a significant amount of air was suctioned. The study by Narayanaswamy et al.3 showed that application of suction failed to improve lung collapse with the Arndt bronchial blocker. Thus, difference in volumes of alveolar gas suctioned should not be a major cause of the observed differences in lung deflation scores. We also agree that a delay in balloon inflation can facilitate elastic recoil lung collapse and improve lung deflation.4 However, we focused on the effect of nitrous oxide for facilitating absorption atelectasis in our study. Therefore, the balloon was kept inflated at the initiation of one-lung ventilation in our study. Finally, Dr. Pfitzner et al.5 commented on the potential ambient air “washing” into the nonventilated lung before
October 2014 • Volume 119 • Number 4
the pleura was open. According to his study, influx of air could be up to 320 mL when a double-lumen tube (DLT) was used. However, considering the radius and length of each device (6 mm and 42 cm in 35 F DLT and 1.4 mm and 78 cm in Arndt bronchial blocker, respectively), volumetric flow rate in the bronchial blocker’s suction channel is 0.15% of the DLT flow rate when the Hagen-Poiseuille equation6 is applied. Therefore, the effect of gas influx through the suction channel should be negligible on lung collapse when the bronchial blocker is used for lung isolation. Tatsuya Yoshimura, MD Department of Anesthesiology Shin-yurigaoka General Hospital Tokyo, Japan Kenichi Ueda, MD Department of Anesthesia University of Iowa Hospitals and Clinics Iowa City, Iowa [email protected] REFERENCES 1. Pfitzner J. Facilitating lung collapse during one lung ventilation can be rational. Anesth Analg 2014;119:1002 2. Yoshimura T, Ueda K, Kakinuma A, Sawai J, Nakata Y. Bronchial blocker lung collapse technique: nitrous oxide for facilitating lung collapse during one-lung ventilation with a bronchial blocker. Anesth Analg 2014;118:666–70 3. Narayanaswamy M, McRae K, Slinger P, Dugas G, Kanellakos GW, Roscoe A, Lacroix M. Choosing a lung isolation device for thoracic surgery: a randomized trial of three bronchial blockers versus double-lumen tubes. Anesth Analg 2009;108:1097–101 4. Young Yoo J, Hee Kim D, Choi H, Kim K, Jeong Chae Y, Yong Park S. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a doublelumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth 2013; [Epub ahead of print] 5. Pfitzner J, Peacock MJ, Harris RJ. Speed of collapse of the nonventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung. Anaesthesia 2001;56:940–6 6. Mujica-Lopez KI, Pearce MA, Narron KA, Perez J, Rubin BK. In vitro evaluation of endotracheal tubes with intrinsic suction. Chest 2010;138:863–9 DOI: 10.1213/ANE.0000000000000349
Prevention of Postoperative Nausea and Vomiting: A Thought on Ondansetron To the Editor
I
n a recent article, Gan et al.1 stated ondansetron to be the standard for antiemesis with regard to postoperative nausea and vomiting and recommended 4 mg IV as suggested by the quantitative systematic review performed by Tramèr et al.2 While I agree that 4 mg may be the optimal IV dose for early outcomes within the first 6 hours according to the original article by Tramèr, it is also perhaps worth considering that 8 mg IV was concluded to be the optimal IV dose
www.anesthesia-analgesia.org 1003
LETTERS TO THE EDITOR
Transversus Abdominis Plane Blocks and Systemic Absorption To the Editor
D
e Oliveira Jr et al.1 recently performed a meta-analysis on the effectiveness of transversus abdominis plane (TAP) blocks in patients undergoing laparoscopic surgery and concluded that these blocks were effective, worked best when performed preoperatively, and had greater opioidsparing effects at 24 hours with larger injected doses. Although these conclusions might be true, the reviewed studies also support the hypothesis that systemic local anesthetics can decrease postoperative pain. None of the reviewed studies controlled for systemic absorption of the local anesthetic. Therefore, whether these benefits are a result of where the amide anesthetics are deposited or a result of their systemic absorptions remains unanswered. Large doses of amide anesthetics have significant systemic effects.2 Lidocaine2 and ropivacaine3 in addition to their anesthetic action both share antiinflammatory properties. Latzke et al.4 demonstrated in healthy volunteers that a TAP block with 150 mg ropivacaine can result in significant concentrations of plasma ropivacaine. Additionally, tissue concentrations remote from the injection site in some subjects were comparable with the tissue concentrations near the injection site, suggesting that a reverse distribution from plasma to remote tissue occurred. Others have demonstrated significant serum concentrations of ropivacaine lasting >12 hours postblock.5 The systemic effects would be greater with a larger absorbed dose, and this meta-analysis demonstrated an increased dose effect at 24 hours. Lidocaine given only during the perioperative period has opioid-sparing effects and is associated with earlier hospital discharge even days after the infusion is stopped.2,6 Serum lidocaine levels in patients benefitting from lidocaine in 1 trial ranged between 1.3 and 3.7 μg/mL.2 Because ropivacaine has 3.6 to 4 times the anesthetic potency of lidocaine,7 these concentrations are significantly less potent than the mean serum ropivacaine concentrations seen in healthy volunteers after a TAP block (Cmax, 1.88 μg/mL mean).4 De Oliveira Jr et al.1 demonstrated an opioid-sparing effect of ropivacaine administered during laparoscopy. This meta-analysis and the included studies do not provide evidence that this dose of amide anesthetic has to be given in the form of a TAP block. Controlled studies demonstrating that the benefits seen are indeed from the block and not systemic absorption have yet to be performed. Scott Groudine, MD Department of Anesthesiology Albany Medical College Albany, New York [email protected] REFERENCES 1. De Oliveira GS Jr, Castro-Alves LJ, Nader A, Kendall MC, McCarthy RJ. Transversus abdominis plane block to ameliorate postoperative pain outcomes after laparoscopic surgery: a meta-analysis of randomized controlled trials. Anesth Analg 2014;118:454–63 Copyright © 2014 International Anesthesia Research Society DOI: 10.1213/ANE.0000000000000327
1002 www.anesthesia-analgesia.org
2. Groudine SB, Fisher HA, Kaufman RP Jr, Patel MK, Wilkins LJ, Mehta SA, Lumb PD. Intravenous lidocaine speeds the return of bowel function, decreases postoperative pain, and shortens hospital stay in patients undergoing radical retropubic prostatectomy. Anesth Analg 1998;86:235–9 3. Blumenthal S, Borgeat A, Pasch T, Reyes L, Booy C, Lambert M, Schimmer RC, Beck-Schimmer B. Ropivacaine decreases inflammation in experimental endotoxin-induced lung injury. Anesthesiology 2006;104:961–9 4. Latzke D, Marhofer P, Kettner SC, Koppatz K, Turnheim K, Lackner E, Sauermann R, Müller M, Zeitlinger M. Pharmacokinetics of the local anesthetic ropivacaine after transversus abdominis plane block in healthy volunteers. Eur J Clin Pharmacol 2012;68:419–25 5. Griffiths JD, Barron FA, Grant S, Bjorksten AR, Hebbard P, Royse CF. Plasma ropivacaine concentrations after ultrasoundguided transversus abdominis plane block. Br J Anaesth 2010;105:853–6 6. Marret E, Rolin M, Beaussier M, Bonnet F. Meta-analysis of intravenous lidocaine and postoperative recovery after abdominal surgery. Br J Surg 2008;95:1331–8 7. Lin Y, Liu SS. Local anesthetics. In: Barash PG, ed. Clinical Anesthesia. 7th ed. Philadelphia, PA: Wolters Kluwer/ Lippincott Williams & Wilkins, 2013:567 DOI: 10.1213/ANE.0000000000000327
Facilitating Lung Collapse During One Lung Ventilation Can Be Rational To the Editor
I
n reporting the results of their study showing the benefit of including nitrous oxide in the ventilating gas mixture before the onset of one-lung ventilation (OLV), Yoshimura et al.1 are to be commended for including bar graphs to present the relevant key findings in all 50 patients studied. The demonstrated “scatter” of lung deflation scores at 1, 5, and 10 minutes very likely reflects the considerable variation in the physiology and pathophysiology of patients undergoing thoracic surgery. Their use of a suction pressure of 10 cm H2O applied to the blocker lumen for 1 minute during surgical opening of the pleura highlights an issue for future risk–benefit studies. These will be complicated by the markedly varying volumes of alveolar gas which might be suctioned in this group of patients before the onset of small airways closure.2 Where prompt collapse of the nonventilated lung is especially advantageous, as in thoracoscopic surgery, consideration should be given to momentarily ceasing mechanical ventilation at the time OLV is initiated. This is relevant with the use of both bronchial blockers and double-lumen tubes (DLTs). With blockers, it will enable OLV to be initiated predictably at end expiration rather than possibly during the inspiratory phase of mechanical ventilation. A delay in balloon inflation will result in an additional degree of elastic recoil lung collapse,3 albeit in both lungs, before the onset of the subsequent absorption atelectasis.1 With DLTs, an oxygen source such as a commercially available, nonpressurized oxygen continuous positive airway pressure system should be attached to the airway of the nonventilated lung October 2014 • Volume 119 • Number 4
Letters to the Editor
when the DLT connector is clamped off as a precursor to initiating OLV. This action will ensure that a potentially large volume of ambient air, with slowly diffusing nitrogen,4 will be prevented from “washing” into the nonventilated lung with each ongoing respiratory excursion of the ventilated lung before the pleura is opened.5 The airway should NOT be left “open to air”! John Pfitzner, FRCA Department of Anaesthesia The Queen Elizabeth Hospital Woodville, South Australia, Australia [email protected] REFERENCES 1. Yoshimura T, Ueda K, Kakinuma A, Sawai J, Nakata Y. Bronchial blocker lung collapse technique: nitrous oxide for facilitating lung collapse during one-lung ventilation with a bronchial blocker. Anesth Analg 2014;118:666–70 2. Pfitzner J, Peacock MJ, Harris RJ. Speed of collapse of the nonventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung. Anaesthesia 2001;56:940–6 3. Young Yoo J, Hee Kim D, Choi H, Kim K, Jeong Chae Y, Yong Park S. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a doublelumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth [Epub ahead of print] 4. Ko R, McRae K, Darling G, Waddell TK, McGlade D, Cheung K, Katz J, Slinger P. The use of air in the inspired gas mixture during two-lung ventilation delays lung collapse during one-lung ventilation. Anesth Analg 2009;108:1092–6 5. Pfitzner J, Peacock MJ, McAleer PT. Gas movement in the nonventilated lung at the onset of single-lung ventilation for videoassisted thoracoscopy. Anaesthesia 1999;54:437–43 DOI: 10.1213/ANE.0000000000000336
In Response We agree with Dr. Pfitzner1 that the “scatter” of lung deflation scores likely reflects the variation in the physiology and pathophysiology of patients in our study2 even though lung function tests showed that there was no difference between the 2 study groups. We understand the concern that markedly varying volumes of alveolar gas were suctioned before the onset of small airway closure, which might have confounded lung deflation scores. However, the level of suction used in our study was low and the Arndt® bronchial blocker (Cook® Critical Care, Bloomington, IN) suction channel had high flow resistance due to a small caliber size and diameter; therefore, it is unlikely that a significant amount of air was suctioned. The study by Narayanaswamy et al.3 showed that application of suction failed to improve lung collapse with the Arndt bronchial blocker. Thus, difference in volumes of alveolar gas suctioned should not be a major cause of the observed differences in lung deflation scores. We also agree that a delay in balloon inflation can facilitate elastic recoil lung collapse and improve lung deflation.4 However, we focused on the effect of nitrous oxide for facilitating absorption atelectasis in our study. Therefore, the balloon was kept inflated at the initiation of one-lung ventilation in our study. Finally, Dr. Pfitzner et al.5 commented on the potential ambient air “washing” into the nonventilated lung before
October 2014 • Volume 119 • Number 4
the pleura was open. According to his study, influx of air could be up to 320 mL when a double-lumen tube (DLT) was used. However, considering the radius and length of each device (6 mm and 42 cm in 35 F DLT and 1.4 mm and 78 cm in Arndt bronchial blocker, respectively), volumetric flow rate in the bronchial blocker’s suction channel is 0.15% of the DLT flow rate when the Hagen-Poiseuille equation6 is applied. Therefore, the effect of gas influx through the suction channel should be negligible on lung collapse when the bronchial blocker is used for lung isolation. Tatsuya Yoshimura, MD Department of Anesthesiology Shin-yurigaoka General Hospital Tokyo, Japan Kenichi Ueda, MD Department of Anesthesia University of Iowa Hospitals and Clinics Iowa City, Iowa [email protected] REFERENCES 1. Pfitzner J. Facilitating lung collapse during one lung ventilation can be rational. Anesth Analg 2014;119:1002 2. Yoshimura T, Ueda K, Kakinuma A, Sawai J, Nakata Y. Bronchial blocker lung collapse technique: nitrous oxide for facilitating lung collapse during one-lung ventilation with a bronchial blocker. Anesth Analg 2014;118:666–70 3. Narayanaswamy M, McRae K, Slinger P, Dugas G, Kanellakos GW, Roscoe A, Lacroix M. Choosing a lung isolation device for thoracic surgery: a randomized trial of three bronchial blockers versus double-lumen tubes. Anesth Analg 2009;108:1097–101 4. Young Yoo J, Hee Kim D, Choi H, Kim K, Jeong Chae Y, Yong Park S. Disconnection technique with a bronchial blocker for improving lung deflation: a comparison with a doublelumen tube and bronchial blocker without disconnection. J Cardiothorac Vasc Anesth 2013; [Epub ahead of print] 5. Pfitzner J, Peacock MJ, Harris RJ. Speed of collapse of the nonventilated lung during single-lung ventilation for thoracoscopic surgery: the effect of transient increases in pleural pressure on the venting of gas from the non-ventilated lung. Anaesthesia 2001;56:940–6 6. Mujica-Lopez KI, Pearce MA, Narron KA, Perez J, Rubin BK. In vitro evaluation of endotracheal tubes with intrinsic suction. Chest 2010;138:863–9 DOI: 10.1213/ANE.0000000000000349
Prevention of Postoperative Nausea and Vomiting: A Thought on Ondansetron To the Editor
I
n a recent article, Gan et al.1 stated ondansetron to be the standard for antiemesis with regard to postoperative nausea and vomiting and recommended 4 mg IV as suggested by the quantitative systematic review performed by Tramèr et al.2 While I agree that 4 mg may be the optimal IV dose for early outcomes within the first 6 hours according to the original article by Tramèr, it is also perhaps worth considering that 8 mg IV was concluded to be the optimal IV dose
www.anesthesia-analgesia.org 1003
