Brief Communications
Intrathecal catheterisation for accidental dural puncture: A successful strategy for reducing post‑dural puncture headache INTRODUCTION The incidence of accidental dural puncture (ADP) varies from 0.19% to 3.6%[1] during epidural space identification and warrants a prompt response. The possible options include; conversion to spinal anaesthesia by injection of hyperbaric drug through the same epidural needle, placement of the epidural catheter in another interspace, intrathecal catheterisation through the dural hole or less commonly abandoning the procedure.[2,3] Although the first two options may help to tide over the immediate anaesthetic/analgesic requirements, post‑dural puncture headache (PDPH) remains a major concern.[1,2] We report case series of 11 adult patients suggesting short term intrathecal catheterisation of dural puncture along with a single dose of intrathecal morphine to be a suitable strategy for PDPH prophylaxis following ADP.
CASE REPORT Of the 686 adult patients who were scheduled for pelvic/lower limb nonobstetric surgery under combined spinal epidural anaesthesia from June 2009 to May 2011 at a Tertiary Care Public Hospital, 11 patients had circumstantial intrathecal placement of lumbar epidural catheter after an ADP. In seven patients, ADP was caused by relatively junior anaesthesiologists with 3-5 years of experience, while in the other four by senior anaesthesiologists with >15 years of experience. In all except one patient, the sitting position with midline approach
was used. The consent for intrathecal catheterisation in case of an ADP was taken pre‑operatively in all the patients. After ADP, the epidural needle was left in situ and a 20G multi‑orifice epidural catheter was threaded through the same 18G epidural needle (both from the BD Perisafe™ epidural mini‑kit,(Becton Dickinson Medical Devices Co. Limited, Suzhov, China) up to a depth of 3-4 cm into the subarachnoid space. The catheter with bacterial filter was taped to the skin. After check aspiration for clear cerebrospinal fluid (CSF), bupivacaine 0.5% (hyperbaric) was injected through the catheter to achieve an appropriate sensory level for surgery [Table 1]. Continuous spinal anaesthesia was maintained intraoperatively with intermittent top ups of 2.5 mg hyperbaric bupivacaine, to maintain an appropriate sensory level of block. Post‑operative analgesia was accomplished with 50 μg morphine supplemented with 2.5-5 mg hyperbaric bupivacaine (as per sensory level at the end of surgery) [Table 1] through the intrathecally placed catheter with the patient maintained in the sitting position for 10 min to reduce rostral spread. The catheter and filter were sealed aseptically and labelled clearly as “Intrathecal catheter: No drug to be given” and the medical staff on duty were duly informed. Standard prophylactic care in terms of patient positioning and fluid supplementation was advised. The catheters were left in situ for ≤24 h. None of the cases reported prolonged motor block, hemodynamic instability, desaturation and need for rescue analgesics. The patients were followed‑up daily for 7-10 days and evaluated for common side effects of intrathecal morphine (nausea, vomiting, respiratory depression, pruritis and urinary retention), symptoms of PDPH (throbbing occipito‑frontal headache worsening on sitting and relieved on lying down; any aggravation with light), paraesthesia, fever and any signs of infection. None of these were observed in any of the patients. Subsequently, patients were evaluated on further visits by surgeon concerned/by personal
Table 1: Continuous spinal anaesthesia: Drug requirements and block characteristics of patients who had intrathecal catheterisation following accidental dural puncture Variables Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 Case 9 Case 10 Case 11 Initial drug (mg) 15+2.5 12.5+5 10 15 15+2.5 12.5 15 15 12.5 12.5 15 Initial block level T8 T6 T10 T4 T10 T6 T6 T8 T6 T6 T8 Duration of surgery (min) 220 85 150 180 120 180 120 100 120 95 120 Post‑operative hyperbaric bupivacaine (mg) 5 2.5 5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
473
Brief Communications
communication until 2-4 weeks. The patients gave written consent for the publication of data.
DISCUSSION Post‑dural puncture headache is observed in >50% patients following an ADP.[4] It may hinder ambulation and increase hospital stay.[5] Immediate placement of an intrathecal catheter for long‑term use (>24 h) or a prophylactic epidural blood patch (EBP) before catheter removal have been suggested to be among the most beneficial methods for preventing PDPH after ADP.[1] However, attempting a repeat epidural for EBP or drug/saline administration itself carries a risk of ADP, which may further increase the potential for PDPH. The intrathecal placement of the epidural catheter was postulated to initially “plug” the dural tear and cease the efflux of CSF from the subarachnoid space.[5] When removed after being in situ for long term, the oedema and fibrinous exudates resulting from an inflammatory reaction were thought to seal the dural hole and prevent further CSF leakage.[6] However, the use of neuraxial opioids rather than the physical presence of the catheter or additional neural fluid have recently been hypothesised[7] to be the probable factors accounting for a decrease in the incidence of PDPH and need for EBP after ADP associated with intrathecal catheterisation. We used short term intrathecal catheterisation along with a single dose of intrathecal morphine. The absence of PDPH despite short term (≤24 h) intrathecal catheterisation in this report may support a likely role of neuraxial opioids in decreasing the incidence of PDPH. Whether the effect was due to opioids entirely or due to intrathecal catheterisation is difficult to ascertain; however in our opinion immediate catheterisation prevented further leak by sealing the hole initially, and the intrathecal opioids subsequently provided analgesia, thus preventing PDPH from developing. The absence of PDPH even with short term intrathecal catheterization (≤24 h) and without the use of any prophylactic analgesics is the strength of this report, as only long‑term intrathecal catheterisation[1,8] for 3-5 days has been tested and correlated to a decreased likelihood of PDPH. Furthermore, none of the patients needed any analgesic top up in the post‑operative period in contrast to the need for 4-5 top ups during 474
the 36-40 h catheter in situ period by Jadon and Sinha.[9] The long duration of action of intrathecal morphine may account for its effectiveness with a single dose. Although, short‑acting intrathecal opioids (fentanyl and buprenorphine) have been shown to decrease the incidence of PDPH,[9,10] there is a paucity of literature regarding the use of intrathecal morphine and its optimal dose for PDPH prophylaxis. Intrathecal 50 μg morphine has been associated with good perioperative analgesia and patient satisfaction in previous studies.[11,12] The use of this small dose in the present series resulted in the prevention of PDPH without any opioid‑related complications. The present report has limitations such as a small sample size, lack of data on the incidence of PDPH after ADP without intrathecal catheterisation and/or intrathecal morphine, a shorter follow‑up time and lack of power analysis; however, the preliminary findings here highlight the potential of the described strategy to provide PDPH prophylaxis following ADP.
CONCLUSION Short term intrathecal catheterisation following ADP when used along with intrathecal morphine as described, may be a safe and useful method for preventing the occurrence of PDPH in the population described. Further, large multi‑centric studies are required before its validation for routine use in clinical practice.
Kapil Chaudhary, Kirti N Saxena, Bharti Taneja, Prachi Gaba, Raktima Anand Department of Anaesthesia and Intensive Care, Maulana Azad Medical College and Associated Hospitals, New Delhi, India Address for correspondence: Dr. Kapil Chaudhary, Department of Anaesthesia and Intensive Care, Maulana Azad Medical College and Associated Hospitals, New Delhi, India. E‑mail: [email protected]
REFERENCES 1.
Apfel CC, Saxena A, Cakmakkaya OS, Gaiser R, George E, Radke O. Prevention of postdural puncture headache after accidental dural puncture: A quantitative systematic review. Br J Anaesth 2010;105:255‑63. 2. Eldrige J. Obstetric anaesthesia and analgesia. In: Allman KG, Wilson IH, editors. Oxford Handbook of Anaesthesia. 2nd ed. New York: Oxford University Press Inc.; 2006. p. 706‑8. 3. Denny NM, Selander DE. Continuous spinal anaesthesia. Br J Anaesth 1998;81:590‑7. 4. Choi PT, Galinski SE, Takeuchi L, Lucas S, Tamayo C, Jadad AR. PDPH is a common complication of neuraxial blockade in parturients: A meta‑analysis of obstetrical studies. Can J Anaesth 2003;50:460‑9. Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
Brief Communications 5.
Dennehy KC, Rosaeg OP. Intrathecal catheter insertion during labour reduces the risk of post‑dural puncture headache. Can J Anaesth 1998;45:42‑5. 6. Denny N, Masters R, Pearson D, Read J, Sihota M, Selander D. Postdural puncture headache after continuous spinal anesthesia. Anesth Analg 1987;66:791‑4. 7. Russell IF. A prospective controlled study of continuous spinal analgesia versus repeat epidural analgesia after accidental dural puncture in labour. Int J Obstet Anesth 2012;21:7‑16. 8. Cohen S, Amar D, Pantuck EJ, Singer N, Divon M. Decreased incidence of headache after accidental dural puncture in caesarean delivery patients receiving continuous postoperative intrathecal analgesia. Acta Anaesthesiol Scand 1994;38:716‑8. 9. Jadon A, Sinha N. Intrathecal catheterization by epidural catheter: Management of accidental dural puncture and prophylaxis of PDPH. Internet J Anesthesiol 2008;16. Available from http://ispub.com/IJA/16/2/11928. 10. Jadon A, Chakraborty S, Sinha N, Agrawal R. Intrathecal catheterization by epidural catheter: Management of accidental dural puncture and prophylaxis of PDPH. Indian J Anaesth 2009;53:30‑4. 11. Eandi JA, de Vere White RW, Tunuguntla HS, Bohringer CH, Evans CP. Can single dose preoperative intrathecal morphine sulfate provide cost‑effective postoperative analgesia and patient satisfaction during radical prostatectomy in the current era of cost containment? Prostate Cancer Prostatic Dis 2002;5:226‑30. 12. Duman A, Apiliogullari S, Balasar M, Gürbüz R, Karcioglu M. Comparison of 50 µg and 25 µg doses of intrathecal morphine on postoperative analgesic requirements in patients undergoing transurethral resection of the prostate with intrathecal anesthesia. J Clin Anesth 2010;22:329‑33. Access this article online Quick response code Website: www.ijaweb.org
DOI: 10.4103/0019-5049.139016
Use of filters in anaesthesia: Is it warranted? INTRODUCTION Anaesthesia machine check is an integral part of the anaesthesiologists’ daily routine. The use of filters in anaesthesia breathing circuit is recommended to reduce the risk of cross‑infections and to prevent the contamination of those parts of the machine which are difficult to clean or sterilise.[1] Cases of filter obstructions have been reported, generally due to excessive secretions, blood in trauma patients or excessive water condensation.[2] This can lead to high‑airway pressures and inadequate ventilation. We report a case of high efficiency particulate air (HEPA‑) Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
filter causing obstruction of anaesthesia circuit despite a normal pre anaesthesia machine check.
CASE REPORT A 15‑year‑old boy, weighing 38 kg, American Society of Anaesthesiologists physical status I, was posted for tonsillectomy under general anaesthesia. Routine monitors including non‑invasive blood pressure, electrocardiogram and pulseoximeter were attached. After premedication, general anaesthesia was induced. The endotracheal tube position was confirmed by auscultation and capnography. Isoflurane 0.81.0% and 60% nitrous oxide in oxygen was started using circle system. Patient was put on IPPV mode on Drager Primus anaesthesia machine with tidal volume = 300 ml, respiratory rate = 14/min, PEEP =5, P max = 25 cm of H2O and I: E ratio 1:2. Immediately, the ventilator alarm sounded for failure to attain tidal volume which was 100 ml only. Manual mode was selected for ventilation which confirmed tightness of the bag and reduced chest excursions with high‑airway pressures. EtCO2 monitor showed obtunded tracings. On auscultation, air entry was severely reduced bilaterally with no evidence of bronchospasm or any foreign sounds. Patient was then ventilated with an AMBU non rebreathing bag. Immediately, chest excursion was evident without any resistance in ventilation. A conclusion of apparatus malfunction was made, and anaesthesia was continued with a fresh anaesthesia machine, uneventfully. Later, on examining the malfunctioning anaesthesia machine, obstruction to ventilation was found to be the HEPA filter at the inlet of the soda lime canister of the circle system. After removal of the HEPA filter and on re‑checking the machine with a test lung, there was no problem in the ventilation.
DISCUSSION Heat and moisture exchangers (HMEs) in combination with bacterial and viral filter (heat and moisture exchanger filters [HMEFs]) are widely used during general anaesthesia. The moisture exchange component passively humidifies the inspired air, and the filter component reduces the risk of viral and bacterial cross contamination between patients.[1] Typically, filters are positioned at the expiratory port 475
Copyright of Indian Journal of Anaesthesia is the property of Medknow Publications & Media Pvt. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Intrathecal catheterisation for accidental dural puncture: A successful strategy for reducing post‑dural puncture headache INTRODUCTION The incidence of accidental dural puncture (ADP) varies from 0.19% to 3.6%[1] during epidural space identification and warrants a prompt response. The possible options include; conversion to spinal anaesthesia by injection of hyperbaric drug through the same epidural needle, placement of the epidural catheter in another interspace, intrathecal catheterisation through the dural hole or less commonly abandoning the procedure.[2,3] Although the first two options may help to tide over the immediate anaesthetic/analgesic requirements, post‑dural puncture headache (PDPH) remains a major concern.[1,2] We report case series of 11 adult patients suggesting short term intrathecal catheterisation of dural puncture along with a single dose of intrathecal morphine to be a suitable strategy for PDPH prophylaxis following ADP.
CASE REPORT Of the 686 adult patients who were scheduled for pelvic/lower limb nonobstetric surgery under combined spinal epidural anaesthesia from June 2009 to May 2011 at a Tertiary Care Public Hospital, 11 patients had circumstantial intrathecal placement of lumbar epidural catheter after an ADP. In seven patients, ADP was caused by relatively junior anaesthesiologists with 3-5 years of experience, while in the other four by senior anaesthesiologists with >15 years of experience. In all except one patient, the sitting position with midline approach
was used. The consent for intrathecal catheterisation in case of an ADP was taken pre‑operatively in all the patients. After ADP, the epidural needle was left in situ and a 20G multi‑orifice epidural catheter was threaded through the same 18G epidural needle (both from the BD Perisafe™ epidural mini‑kit,(Becton Dickinson Medical Devices Co. Limited, Suzhov, China) up to a depth of 3-4 cm into the subarachnoid space. The catheter with bacterial filter was taped to the skin. After check aspiration for clear cerebrospinal fluid (CSF), bupivacaine 0.5% (hyperbaric) was injected through the catheter to achieve an appropriate sensory level for surgery [Table 1]. Continuous spinal anaesthesia was maintained intraoperatively with intermittent top ups of 2.5 mg hyperbaric bupivacaine, to maintain an appropriate sensory level of block. Post‑operative analgesia was accomplished with 50 μg morphine supplemented with 2.5-5 mg hyperbaric bupivacaine (as per sensory level at the end of surgery) [Table 1] through the intrathecally placed catheter with the patient maintained in the sitting position for 10 min to reduce rostral spread. The catheter and filter were sealed aseptically and labelled clearly as “Intrathecal catheter: No drug to be given” and the medical staff on duty were duly informed. Standard prophylactic care in terms of patient positioning and fluid supplementation was advised. The catheters were left in situ for ≤24 h. None of the cases reported prolonged motor block, hemodynamic instability, desaturation and need for rescue analgesics. The patients were followed‑up daily for 7-10 days and evaluated for common side effects of intrathecal morphine (nausea, vomiting, respiratory depression, pruritis and urinary retention), symptoms of PDPH (throbbing occipito‑frontal headache worsening on sitting and relieved on lying down; any aggravation with light), paraesthesia, fever and any signs of infection. None of these were observed in any of the patients. Subsequently, patients were evaluated on further visits by surgeon concerned/by personal
Table 1: Continuous spinal anaesthesia: Drug requirements and block characteristics of patients who had intrathecal catheterisation following accidental dural puncture Variables Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 Case 9 Case 10 Case 11 Initial drug (mg) 15+2.5 12.5+5 10 15 15+2.5 12.5 15 15 12.5 12.5 15 Initial block level T8 T6 T10 T4 T10 T6 T6 T8 T6 T6 T8 Duration of surgery (min) 220 85 150 180 120 180 120 100 120 95 120 Post‑operative hyperbaric bupivacaine (mg) 5 2.5 5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
473
Brief Communications
communication until 2-4 weeks. The patients gave written consent for the publication of data.
DISCUSSION Post‑dural puncture headache is observed in >50% patients following an ADP.[4] It may hinder ambulation and increase hospital stay.[5] Immediate placement of an intrathecal catheter for long‑term use (>24 h) or a prophylactic epidural blood patch (EBP) before catheter removal have been suggested to be among the most beneficial methods for preventing PDPH after ADP.[1] However, attempting a repeat epidural for EBP or drug/saline administration itself carries a risk of ADP, which may further increase the potential for PDPH. The intrathecal placement of the epidural catheter was postulated to initially “plug” the dural tear and cease the efflux of CSF from the subarachnoid space.[5] When removed after being in situ for long term, the oedema and fibrinous exudates resulting from an inflammatory reaction were thought to seal the dural hole and prevent further CSF leakage.[6] However, the use of neuraxial opioids rather than the physical presence of the catheter or additional neural fluid have recently been hypothesised[7] to be the probable factors accounting for a decrease in the incidence of PDPH and need for EBP after ADP associated with intrathecal catheterisation. We used short term intrathecal catheterisation along with a single dose of intrathecal morphine. The absence of PDPH despite short term (≤24 h) intrathecal catheterisation in this report may support a likely role of neuraxial opioids in decreasing the incidence of PDPH. Whether the effect was due to opioids entirely or due to intrathecal catheterisation is difficult to ascertain; however in our opinion immediate catheterisation prevented further leak by sealing the hole initially, and the intrathecal opioids subsequently provided analgesia, thus preventing PDPH from developing. The absence of PDPH even with short term intrathecal catheterization (≤24 h) and without the use of any prophylactic analgesics is the strength of this report, as only long‑term intrathecal catheterisation[1,8] for 3-5 days has been tested and correlated to a decreased likelihood of PDPH. Furthermore, none of the patients needed any analgesic top up in the post‑operative period in contrast to the need for 4-5 top ups during 474
the 36-40 h catheter in situ period by Jadon and Sinha.[9] The long duration of action of intrathecal morphine may account for its effectiveness with a single dose. Although, short‑acting intrathecal opioids (fentanyl and buprenorphine) have been shown to decrease the incidence of PDPH,[9,10] there is a paucity of literature regarding the use of intrathecal morphine and its optimal dose for PDPH prophylaxis. Intrathecal 50 μg morphine has been associated with good perioperative analgesia and patient satisfaction in previous studies.[11,12] The use of this small dose in the present series resulted in the prevention of PDPH without any opioid‑related complications. The present report has limitations such as a small sample size, lack of data on the incidence of PDPH after ADP without intrathecal catheterisation and/or intrathecal morphine, a shorter follow‑up time and lack of power analysis; however, the preliminary findings here highlight the potential of the described strategy to provide PDPH prophylaxis following ADP.
CONCLUSION Short term intrathecal catheterisation following ADP when used along with intrathecal morphine as described, may be a safe and useful method for preventing the occurrence of PDPH in the population described. Further, large multi‑centric studies are required before its validation for routine use in clinical practice.
Kapil Chaudhary, Kirti N Saxena, Bharti Taneja, Prachi Gaba, Raktima Anand Department of Anaesthesia and Intensive Care, Maulana Azad Medical College and Associated Hospitals, New Delhi, India Address for correspondence: Dr. Kapil Chaudhary, Department of Anaesthesia and Intensive Care, Maulana Azad Medical College and Associated Hospitals, New Delhi, India. E‑mail: [email protected]
REFERENCES 1.
Apfel CC, Saxena A, Cakmakkaya OS, Gaiser R, George E, Radke O. Prevention of postdural puncture headache after accidental dural puncture: A quantitative systematic review. Br J Anaesth 2010;105:255‑63. 2. Eldrige J. Obstetric anaesthesia and analgesia. In: Allman KG, Wilson IH, editors. Oxford Handbook of Anaesthesia. 2nd ed. New York: Oxford University Press Inc.; 2006. p. 706‑8. 3. Denny NM, Selander DE. Continuous spinal anaesthesia. Br J Anaesth 1998;81:590‑7. 4. Choi PT, Galinski SE, Takeuchi L, Lucas S, Tamayo C, Jadad AR. PDPH is a common complication of neuraxial blockade in parturients: A meta‑analysis of obstetrical studies. Can J Anaesth 2003;50:460‑9. Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
Brief Communications 5.
Dennehy KC, Rosaeg OP. Intrathecal catheter insertion during labour reduces the risk of post‑dural puncture headache. Can J Anaesth 1998;45:42‑5. 6. Denny N, Masters R, Pearson D, Read J, Sihota M, Selander D. Postdural puncture headache after continuous spinal anesthesia. Anesth Analg 1987;66:791‑4. 7. Russell IF. A prospective controlled study of continuous spinal analgesia versus repeat epidural analgesia after accidental dural puncture in labour. Int J Obstet Anesth 2012;21:7‑16. 8. Cohen S, Amar D, Pantuck EJ, Singer N, Divon M. Decreased incidence of headache after accidental dural puncture in caesarean delivery patients receiving continuous postoperative intrathecal analgesia. Acta Anaesthesiol Scand 1994;38:716‑8. 9. Jadon A, Sinha N. Intrathecal catheterization by epidural catheter: Management of accidental dural puncture and prophylaxis of PDPH. Internet J Anesthesiol 2008;16. Available from http://ispub.com/IJA/16/2/11928. 10. Jadon A, Chakraborty S, Sinha N, Agrawal R. Intrathecal catheterization by epidural catheter: Management of accidental dural puncture and prophylaxis of PDPH. Indian J Anaesth 2009;53:30‑4. 11. Eandi JA, de Vere White RW, Tunuguntla HS, Bohringer CH, Evans CP. Can single dose preoperative intrathecal morphine sulfate provide cost‑effective postoperative analgesia and patient satisfaction during radical prostatectomy in the current era of cost containment? Prostate Cancer Prostatic Dis 2002;5:226‑30. 12. Duman A, Apiliogullari S, Balasar M, Gürbüz R, Karcioglu M. Comparison of 50 µg and 25 µg doses of intrathecal morphine on postoperative analgesic requirements in patients undergoing transurethral resection of the prostate with intrathecal anesthesia. J Clin Anesth 2010;22:329‑33. Access this article online Quick response code Website: www.ijaweb.org
DOI: 10.4103/0019-5049.139016
Use of filters in anaesthesia: Is it warranted? INTRODUCTION Anaesthesia machine check is an integral part of the anaesthesiologists’ daily routine. The use of filters in anaesthesia breathing circuit is recommended to reduce the risk of cross‑infections and to prevent the contamination of those parts of the machine which are difficult to clean or sterilise.[1] Cases of filter obstructions have been reported, generally due to excessive secretions, blood in trauma patients or excessive water condensation.[2] This can lead to high‑airway pressures and inadequate ventilation. We report a case of high efficiency particulate air (HEPA‑) Indian Journal of Anaesthesia | Vol. 58 | Issue 4 | Jul-Aug 2014
filter causing obstruction of anaesthesia circuit despite a normal pre anaesthesia machine check.
CASE REPORT A 15‑year‑old boy, weighing 38 kg, American Society of Anaesthesiologists physical status I, was posted for tonsillectomy under general anaesthesia. Routine monitors including non‑invasive blood pressure, electrocardiogram and pulseoximeter were attached. After premedication, general anaesthesia was induced. The endotracheal tube position was confirmed by auscultation and capnography. Isoflurane 0.81.0% and 60% nitrous oxide in oxygen was started using circle system. Patient was put on IPPV mode on Drager Primus anaesthesia machine with tidal volume = 300 ml, respiratory rate = 14/min, PEEP =5, P max = 25 cm of H2O and I: E ratio 1:2. Immediately, the ventilator alarm sounded for failure to attain tidal volume which was 100 ml only. Manual mode was selected for ventilation which confirmed tightness of the bag and reduced chest excursions with high‑airway pressures. EtCO2 monitor showed obtunded tracings. On auscultation, air entry was severely reduced bilaterally with no evidence of bronchospasm or any foreign sounds. Patient was then ventilated with an AMBU non rebreathing bag. Immediately, chest excursion was evident without any resistance in ventilation. A conclusion of apparatus malfunction was made, and anaesthesia was continued with a fresh anaesthesia machine, uneventfully. Later, on examining the malfunctioning anaesthesia machine, obstruction to ventilation was found to be the HEPA filter at the inlet of the soda lime canister of the circle system. After removal of the HEPA filter and on re‑checking the machine with a test lung, there was no problem in the ventilation.
DISCUSSION Heat and moisture exchangers (HMEs) in combination with bacterial and viral filter (heat and moisture exchanger filters [HMEFs]) are widely used during general anaesthesia. The moisture exchange component passively humidifies the inspired air, and the filter component reduces the risk of viral and bacterial cross contamination between patients.[1] Typically, filters are positioned at the expiratory port 475
Copyright of Indian Journal of Anaesthesia is the property of Medknow Publications & Media Pvt. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
