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Carbon Dioxide Absorption During Laparoscopic Donor Nephrectomy: A Comparison Between Retroperitoneal and Transperitoneal Approaches
Carbon Dioxide Absorption During Laparoscopic Donor Nephrectomy: A Comparison Between Retroperitoneal and Transperitoneal Approaches P.G. Kadam, M. Marda, and V.R. Shah
ABSTRACT Aim. Previous studies have suggested that retroperitoneal and transperitoneal approaches for laparoscopic donor nephrectomy are associated with variable carbon dioxide (CO2) absorption, which can cause significant morbidity. The approach that results in greater CO2 absorption is a matter of debate. We studied patients undergoing transperitoneal/retroperitoneal donor nephrectomy to determine relative CO2 absorption, incidence of subcutaneous emphysema, pneumothorax, and pneumomediastinum, seeking to establish a correlation between the incidence of subcutaneous emphysema and CO2 elimination. Materials and methods. This was a prospective nonrandomized, single-center, two-arm clinical study of 60 kidney donors undergoing laparoscopic nephrectomy by transperitoneal (n ⫽ 30) or retroperitoneal (n ⫽ 30) approach. CO2 elimination was calculated using end tidal CO2, tidal volume, respiratory rate, and weight of the donor. We studied intraoperative CO2 elimination and CO2 retention-related morbidities. Results. There was a significant increase in CO2 elimination in the first 30 minutes of insufflation followed by a plateau for the remainder of procedure. There was no difference in CO2 elimination in either procedure at any time interval. Patients with subcutaneous emphysema showed significantly greater CO2 elimination, which decreased with desufflation. Conclusion. CO2 absorption during laparoscopy did not depend on the route of surgery. Subcutaneous emphysema was strongly and independently associated with a greater degree of CO2 absorption during laparoscopic surgery.
L
APAROSCOPIC DONOR NEPHRECTOMY has replaced conventional open surgery due to several advantages to the donor. There are two approaches for these procedures: transperitoneal and retroperitoneal. It is a matter of debate as to which approach results in greater carbon dioxide (CO2) absorption. Some reports have suggested that patients show greater CO2 absorption with the retroperitoneal as compared to the transperitoneal approach, leading to morbidities like hemodynamic changes, subcutaneous emphysema, pneumomediastinum, and pneumothorax.1 We performed a prospective, nonrandomized, single-center clinical study with two equal arms of 60 kidney donors undergoing laparoscopic nephrectomy by the transperitoneal versus the retroperitoneal approach to determine relative CO2 absorption and to compare the incidence
of subcutaneous emphysema, pneumothorax, and pneumomediastinum, seeking to establish a correlation between the incidence of subcutaneous emphysema and CO2 elimination.
From the Department of Anaesthesia and Critical Care, G.R. Doshi and K.M. Mehta Institute of Kidney Diseases and Research Centre and Dr H.L. Trivedi Institute of Transplantation Sciences, Ahmedabad, Gujarat, India. Address reprint requests to Dr Prachi G. Kadam, Tutor, Department of Anesthesia and Critical Care, G.R. Doshi and K.M. Mehta Institute of Kidney Diseases and Research Centre (IKDRC)–Dr H.L. Trivedi Institute of Transplantation Sciences (ITS), Civil Hospital Campus, Asarwa, Ahmedabad–380016, Gujarat, India. E-mail: [email protected]
© 2008 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/08/$–see front matter doi:10.1016/j.transproceed.2008.03.024
Transplantation Proceedings, 40, 1119 –1121 (2008)
1119
1120
KADAM, MARDA, AND SHAH
MATERIALS AND METHODS Sixty ASA I/II patients between 18 and 70 years of age undergoing laparoscopic donor nephrectomy under general anesthesia were enrolled in the study. We excluded patients with body mass index ⬎30, patient with cardiac/respiratory disorder, and cases that were later converted to open surgery. This study and informed consent forms were approved by institutional Ethics Committee. Standardized balanced general anaesthesia was administered to all patients. Ventilation was controlled with a ventilator equipped to monitor expiratory volumes and airway pressures (Fabius, Drager Medical, Germany). Peritoneal insufflation was performed with a CO2 Storz insufflator. Abdominal pressure was maintained at 12 mm Hg during surgery. Heart rate, noninvasive blood pressure, electrocardiogram, O2 saturation, and end tidal CO2 (sidestream analyzer BCI) were monitored throughout surgery. Controlled ventilation was continuously adjusted to maintain end tidal CO2 (ETCO2) between 35 ⫾ 5 mm Hg. Respiratory rate (RR), tidal volume and ETCO2, were recorded before and after insufflation at 0-, 5-, 15-, 30-, and 60-minute intervals and then hourly postinsufflation until extubation. We also noted the duration of insufflation and surgery. CO2 absorption per se cannot be measured directly during the course of surgery; instead, CO2 elimination (mL/kg/min) was calculated using the equation as described by Wolf et al1 and Christopher et al.2 CO2 elimination ⫽
ETCO2 ⫻ TV ⫻ RR (PB ⫺ PH2O) ⫻ Wt
where ETCO2 is end tidal CO2 pressure in mm Hg; TV is expired tidal volume in mL; RR is the respiratory rate/min; PB is the barometric pressure (760 mm Hg); PH2O is the partial pressure of water vapor (13 mm Hg), and Wt is the weight of patient in kilograms.1,2 Chest radiographs obtained postoperatively in all patients were evaluated for subcutaneous emphysema, pneumothorax, and pneumomediastinum. Statistical analysis was performed using Student t test and a two-way analysis of variance test with P ⬍ .05 considered significant.
RESULTS
Baseline demographics and surgical data of both groups were comparable. Mean donor age in transperitoneal group was 42.5 ⫾ 10.1 years; weight, 62.2 ⫾ 15.2 kg; duration of surgery, 214 ⫾ 25.2 minutes; and mean insufflation time, 185 ⫾ 14.3 minutes. Among the retroperitoneal group, the
Fig 1. Mean CO2 elimination (VCO2) versus time in patients with transperitoneal and retroperitoneal approaches.
Fig 2. Mean Co2 elimination in patients with and without subcutaneous emphysema (t test; P ⬍ .05).
values were 39.2 ⫾ 13.5 years; 64.6 ⫾ 14.2 kg; 234 ⫾ 32.5 minutes; and 196.2 ⫾ 25.2 minutes, respectively. Mean CO2 elimination in both groups was plotted against time (Fig 1). Irrespective of the approach, CO2 elimination increased with time during the first hour of insufflation and then remained at a plateau for the remainder of the procedure. There was a significant increase during the first 30 minutes of insufflation. Subcutaneous emphysema was noted in 3 (10%) patients in the transperitoneal and 10 (33%) patients in the retroperitoneal cohort (P ⬍ .05). Pneumothorax was seen in one patient in each group. Radiographically detected but clinically asymptomatic pneumomediastinum was noted in one patient who required no treatment. CO2 elimination curves in patients with and without subcutaneous emphysema irrespective of the approach are compared in Fig 2. Mean CO2 elimination was significantly greater among patients with subcutaneous emphysema compared to those without subcutaneous emphysema, starting from 3 minutes to 3 hours of insufflation. However, this effect rapidly tapered to control levels after desufflation. DISCUSSION
The principal findings of our study were an early increase in CO2 absorption after insufflation, which subsequently remained a plateau. There was no significant difference in CO2 elimination between either approach. We observed a strong correlation between CO2 absorption and development of subcutaneous emphysema. CO2 absorption was increased early after insufflation, leveling off toward the end of insufflation, confirming other studies.1 Gas absorption from a cavity depends on its diffusibility and perfusion of walls of that cavity.3 Increased CO2 elimination over the first 30 minutes in the transperitoneal group may be explained by the greater absorptive area and better perfusion of the peritoneum.4 However, increased intra-abdominal pressure may reduce peritoneal perfusion, leading to a decrease in CO2 absorption and a steady state after 60 minutes. In the retroperitoneal group, the disruption of microvascular and lymphatic channels
CARBON DIOXIDE ABSORPTION
during creation of the working place results in a large gas exchange area, leading to increased CO2 elimination in the first 30 minutes. However, it has been hypothesized that retroperitoneal insufflation may potentially cause greater CO2 absorption, because the retroperitoneal space is highly vascular, contains areolar tissue, and is not as limited as the peritoneum. Previous studies comparing CO2 absorption between transperitoneal and retroperitoneal insufflation differ in their results. Mullet et al reported that CO2 absorption was more marked during retroperitoneal compared to transperitoneal CO2 insufflation.5 Wolf et al reported that the retroperitoneal approach and development of subcutaneous emphysema were independently associated with greater increases in CO2 elimination,2 whereas Christopher et al did not observe greater absorption of CO2 among the retroperitoneal compared to the transperitoneal group.2 In our study, although CO2 elimination was higher in the retroperitoneal group compared to the transperitoneal group, it did not achieve statistical significance. Subcutaneous emphysema remains a common complication of retroperitoneal laparoscopy with a reported incidence of 45%. A strong relationship between CO2 elimination and development of subcutaneous emphysema irrespective of the approach is supported by earlier publications.1,2,5–7 The resorptive surface can increase with time as subcutaneous emphysema develops and spreads, which would explain why one observes a steady increase in CO2 absorption with development of subcutaneous emphysema. We also believe that higher levels of CO2 elimination in the retroperitoneal group during the intraoperative period were related to a higher incidence of subcutaneous emphysema (33%) compared with the transperitoneal group
1121
(10%). If the port site air leak and the resultant subcutaneous air trapping during retroperitoneoscopy are minimized, CO2 absorption during retroperitoneal surgery should logically be no greater than that during a comparable transperitoneal laparoscopic procedure. In conclusion this prospective nonrandomized study suggested that CO2 elimination during laparoscopy does not depend on the route of surgery. Subcutaneous emphysema was strongly and independently associated with a greater degree of CO2 absorption during laparoscopic surgery. Adequate ventilation with continuous monitoring of ETCO2 is recommended to prevent clinical sequela of hypercapnia. REFERENCES 1. Wolf JS Jr, Monk TG, Mc Dougall, et al: The extraperitoneal approach and subcutaneous emphysema are associated with greater absorption of carbon dioxide during laparoscopic renal surgery. J Urol 154:959, 1995 2. Christopher SNG, Inderbir SG, Gyung TS, et al: Retroperitoneoscopic surgery is not associated with increased CO2 absorption. J Urol 162:1268, 1999 3. Joris JL: Anaesthetic management of laparoscopy. In Miller RD (ed): Anaesthesia. 4th ed. New York: Churchill Livingstone; 1994, p 2 4. Collins JM: Inert gas exchange of subcutaneous and intraperitoneal gas pockets in piglets. Respir Physiol 46:391, 1981 5. Mullet CE, Vaile JP, Saguard PE, et al: Pulmonary CO2 elimination during surgical procedures using intraperitoneal or extraperitoneal insufflation. Anesth Anal 76:622, 1993 6. Atallah F, Bastide-Heulin T, Soulie M, et al: Haemodynamic changes during retroperitoneoscopic adrenalectomy for pheochromocytoma. Br J Anaesth 86:731, 2001 7. Harkin CP, Sommerhaug EW, Mayer KL: An unexpected complication during laparoscopic herniorrhaphy. Anesth Anal 89: 1576, 1999
ABSTRACT Aim. Previous studies have suggested that retroperitoneal and transperitoneal approaches for laparoscopic donor nephrectomy are associated with variable carbon dioxide (CO2) absorption, which can cause significant morbidity. The approach that results in greater CO2 absorption is a matter of debate. We studied patients undergoing transperitoneal/retroperitoneal donor nephrectomy to determine relative CO2 absorption, incidence of subcutaneous emphysema, pneumothorax, and pneumomediastinum, seeking to establish a correlation between the incidence of subcutaneous emphysema and CO2 elimination. Materials and methods. This was a prospective nonrandomized, single-center, two-arm clinical study of 60 kidney donors undergoing laparoscopic nephrectomy by transperitoneal (n ⫽ 30) or retroperitoneal (n ⫽ 30) approach. CO2 elimination was calculated using end tidal CO2, tidal volume, respiratory rate, and weight of the donor. We studied intraoperative CO2 elimination and CO2 retention-related morbidities. Results. There was a significant increase in CO2 elimination in the first 30 minutes of insufflation followed by a plateau for the remainder of procedure. There was no difference in CO2 elimination in either procedure at any time interval. Patients with subcutaneous emphysema showed significantly greater CO2 elimination, which decreased with desufflation. Conclusion. CO2 absorption during laparoscopy did not depend on the route of surgery. Subcutaneous emphysema was strongly and independently associated with a greater degree of CO2 absorption during laparoscopic surgery.
L
APAROSCOPIC DONOR NEPHRECTOMY has replaced conventional open surgery due to several advantages to the donor. There are two approaches for these procedures: transperitoneal and retroperitoneal. It is a matter of debate as to which approach results in greater carbon dioxide (CO2) absorption. Some reports have suggested that patients show greater CO2 absorption with the retroperitoneal as compared to the transperitoneal approach, leading to morbidities like hemodynamic changes, subcutaneous emphysema, pneumomediastinum, and pneumothorax.1 We performed a prospective, nonrandomized, single-center clinical study with two equal arms of 60 kidney donors undergoing laparoscopic nephrectomy by the transperitoneal versus the retroperitoneal approach to determine relative CO2 absorption and to compare the incidence
of subcutaneous emphysema, pneumothorax, and pneumomediastinum, seeking to establish a correlation between the incidence of subcutaneous emphysema and CO2 elimination.
From the Department of Anaesthesia and Critical Care, G.R. Doshi and K.M. Mehta Institute of Kidney Diseases and Research Centre and Dr H.L. Trivedi Institute of Transplantation Sciences, Ahmedabad, Gujarat, India. Address reprint requests to Dr Prachi G. Kadam, Tutor, Department of Anesthesia and Critical Care, G.R. Doshi and K.M. Mehta Institute of Kidney Diseases and Research Centre (IKDRC)–Dr H.L. Trivedi Institute of Transplantation Sciences (ITS), Civil Hospital Campus, Asarwa, Ahmedabad–380016, Gujarat, India. E-mail: [email protected]
© 2008 by Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010-1710
0041-1345/08/$–see front matter doi:10.1016/j.transproceed.2008.03.024
Transplantation Proceedings, 40, 1119 –1121 (2008)
1119
1120
KADAM, MARDA, AND SHAH
MATERIALS AND METHODS Sixty ASA I/II patients between 18 and 70 years of age undergoing laparoscopic donor nephrectomy under general anesthesia were enrolled in the study. We excluded patients with body mass index ⬎30, patient with cardiac/respiratory disorder, and cases that were later converted to open surgery. This study and informed consent forms were approved by institutional Ethics Committee. Standardized balanced general anaesthesia was administered to all patients. Ventilation was controlled with a ventilator equipped to monitor expiratory volumes and airway pressures (Fabius, Drager Medical, Germany). Peritoneal insufflation was performed with a CO2 Storz insufflator. Abdominal pressure was maintained at 12 mm Hg during surgery. Heart rate, noninvasive blood pressure, electrocardiogram, O2 saturation, and end tidal CO2 (sidestream analyzer BCI) were monitored throughout surgery. Controlled ventilation was continuously adjusted to maintain end tidal CO2 (ETCO2) between 35 ⫾ 5 mm Hg. Respiratory rate (RR), tidal volume and ETCO2, were recorded before and after insufflation at 0-, 5-, 15-, 30-, and 60-minute intervals and then hourly postinsufflation until extubation. We also noted the duration of insufflation and surgery. CO2 absorption per se cannot be measured directly during the course of surgery; instead, CO2 elimination (mL/kg/min) was calculated using the equation as described by Wolf et al1 and Christopher et al.2 CO2 elimination ⫽
ETCO2 ⫻ TV ⫻ RR (PB ⫺ PH2O) ⫻ Wt
where ETCO2 is end tidal CO2 pressure in mm Hg; TV is expired tidal volume in mL; RR is the respiratory rate/min; PB is the barometric pressure (760 mm Hg); PH2O is the partial pressure of water vapor (13 mm Hg), and Wt is the weight of patient in kilograms.1,2 Chest radiographs obtained postoperatively in all patients were evaluated for subcutaneous emphysema, pneumothorax, and pneumomediastinum. Statistical analysis was performed using Student t test and a two-way analysis of variance test with P ⬍ .05 considered significant.
RESULTS
Baseline demographics and surgical data of both groups were comparable. Mean donor age in transperitoneal group was 42.5 ⫾ 10.1 years; weight, 62.2 ⫾ 15.2 kg; duration of surgery, 214 ⫾ 25.2 minutes; and mean insufflation time, 185 ⫾ 14.3 minutes. Among the retroperitoneal group, the
Fig 1. Mean CO2 elimination (VCO2) versus time in patients with transperitoneal and retroperitoneal approaches.
Fig 2. Mean Co2 elimination in patients with and without subcutaneous emphysema (t test; P ⬍ .05).
values were 39.2 ⫾ 13.5 years; 64.6 ⫾ 14.2 kg; 234 ⫾ 32.5 minutes; and 196.2 ⫾ 25.2 minutes, respectively. Mean CO2 elimination in both groups was plotted against time (Fig 1). Irrespective of the approach, CO2 elimination increased with time during the first hour of insufflation and then remained at a plateau for the remainder of the procedure. There was a significant increase during the first 30 minutes of insufflation. Subcutaneous emphysema was noted in 3 (10%) patients in the transperitoneal and 10 (33%) patients in the retroperitoneal cohort (P ⬍ .05). Pneumothorax was seen in one patient in each group. Radiographically detected but clinically asymptomatic pneumomediastinum was noted in one patient who required no treatment. CO2 elimination curves in patients with and without subcutaneous emphysema irrespective of the approach are compared in Fig 2. Mean CO2 elimination was significantly greater among patients with subcutaneous emphysema compared to those without subcutaneous emphysema, starting from 3 minutes to 3 hours of insufflation. However, this effect rapidly tapered to control levels after desufflation. DISCUSSION
The principal findings of our study were an early increase in CO2 absorption after insufflation, which subsequently remained a plateau. There was no significant difference in CO2 elimination between either approach. We observed a strong correlation between CO2 absorption and development of subcutaneous emphysema. CO2 absorption was increased early after insufflation, leveling off toward the end of insufflation, confirming other studies.1 Gas absorption from a cavity depends on its diffusibility and perfusion of walls of that cavity.3 Increased CO2 elimination over the first 30 minutes in the transperitoneal group may be explained by the greater absorptive area and better perfusion of the peritoneum.4 However, increased intra-abdominal pressure may reduce peritoneal perfusion, leading to a decrease in CO2 absorption and a steady state after 60 minutes. In the retroperitoneal group, the disruption of microvascular and lymphatic channels
CARBON DIOXIDE ABSORPTION
during creation of the working place results in a large gas exchange area, leading to increased CO2 elimination in the first 30 minutes. However, it has been hypothesized that retroperitoneal insufflation may potentially cause greater CO2 absorption, because the retroperitoneal space is highly vascular, contains areolar tissue, and is not as limited as the peritoneum. Previous studies comparing CO2 absorption between transperitoneal and retroperitoneal insufflation differ in their results. Mullet et al reported that CO2 absorption was more marked during retroperitoneal compared to transperitoneal CO2 insufflation.5 Wolf et al reported that the retroperitoneal approach and development of subcutaneous emphysema were independently associated with greater increases in CO2 elimination,2 whereas Christopher et al did not observe greater absorption of CO2 among the retroperitoneal compared to the transperitoneal group.2 In our study, although CO2 elimination was higher in the retroperitoneal group compared to the transperitoneal group, it did not achieve statistical significance. Subcutaneous emphysema remains a common complication of retroperitoneal laparoscopy with a reported incidence of 45%. A strong relationship between CO2 elimination and development of subcutaneous emphysema irrespective of the approach is supported by earlier publications.1,2,5–7 The resorptive surface can increase with time as subcutaneous emphysema develops and spreads, which would explain why one observes a steady increase in CO2 absorption with development of subcutaneous emphysema. We also believe that higher levels of CO2 elimination in the retroperitoneal group during the intraoperative period were related to a higher incidence of subcutaneous emphysema (33%) compared with the transperitoneal group
1121
(10%). If the port site air leak and the resultant subcutaneous air trapping during retroperitoneoscopy are minimized, CO2 absorption during retroperitoneal surgery should logically be no greater than that during a comparable transperitoneal laparoscopic procedure. In conclusion this prospective nonrandomized study suggested that CO2 elimination during laparoscopy does not depend on the route of surgery. Subcutaneous emphysema was strongly and independently associated with a greater degree of CO2 absorption during laparoscopic surgery. Adequate ventilation with continuous monitoring of ETCO2 is recommended to prevent clinical sequela of hypercapnia. REFERENCES 1. Wolf JS Jr, Monk TG, Mc Dougall, et al: The extraperitoneal approach and subcutaneous emphysema are associated with greater absorption of carbon dioxide during laparoscopic renal surgery. J Urol 154:959, 1995 2. Christopher SNG, Inderbir SG, Gyung TS, et al: Retroperitoneoscopic surgery is not associated with increased CO2 absorption. J Urol 162:1268, 1999 3. Joris JL: Anaesthetic management of laparoscopy. In Miller RD (ed): Anaesthesia. 4th ed. New York: Churchill Livingstone; 1994, p 2 4. Collins JM: Inert gas exchange of subcutaneous and intraperitoneal gas pockets in piglets. Respir Physiol 46:391, 1981 5. Mullet CE, Vaile JP, Saguard PE, et al: Pulmonary CO2 elimination during surgical procedures using intraperitoneal or extraperitoneal insufflation. Anesth Anal 76:622, 1993 6. Atallah F, Bastide-Heulin T, Soulie M, et al: Haemodynamic changes during retroperitoneoscopic adrenalectomy for pheochromocytoma. Br J Anaesth 86:731, 2001 7. Harkin CP, Sommerhaug EW, Mayer KL: An unexpected complication during laparoscopic herniorrhaphy. Anesth Anal 89: 1576, 1999