Increased carbon dioxide absorption during retroperitoneal laparoscopy

B. Streich, F. Decailliot, C. Perney and P. Duvaldestin*

Department of Anesthesiology and Intensive Care Unit, Henri Mondor Hospital, 51 avenue Marechal de Lattre de Tassigny, 94010 Creteil, France

*Corresponding author. E-mail: philippe.duvaldestin@hmn.ap-hop-paris.fr

Accepted for publication: July 9, 2003


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Background. Retroperitoneoscopy for renal surgery is now a common procedure. We compared carbon dioxide absorption in patients undergoing retroperitoneoscopy for adrenal or renal surgery with that of patients undergoing laparoscopic cholecystectomy.

Methods. We measured carbon dioxide elimination with a metabolic monitor in 30 anaesthetized patients with controlled ventilation, undergoing retroperitoneoscopy (n=10), laparoscopy (n=10) or orthopaedic surgery (n=10).

Results. Carbon dioxide production increased by 38, 46 and 63% at 30, 60 and 90 min after insufflation (P<0.01) in patients having retroperitoneoscopy. Carbon dioxide production (mean (SD)) increased from 92 (21) to 150 (43) ml min–1 m–2 60–90 min after insufflation and remained increased after the end of insufflation. During laparoscopy, V·CO2 increased less (by 15%) (P<0.05 compared with retroperitoneoscopy) and remained steady throughout the procedure.

Conclusion. Retroperitoneal carbon dioxide insufflation causes more carbon dioxide absorption than intraperitoneal insufflation, and controlled ventilation should be increased if hypercapnia should be avoided.

Br J Anaesth 2003; 91: 793–6

Keywords: carbon dioxide, measurement; surgery, renal; surgery, retroperitoneoscopy


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Carbon dioxide insufflation during laparoscopic surgery may cause respiratory acidosis from systemic absorption of carbon dioxide.1 2 Diffusion of carbon dioxide into the body depends on the site of insufflation. Technical advances in laparoscopic instruments have led to the development of new laparoscopic procedures, especially involving extraperitoneal sites. Retroperitoneal insufflation of carbon dioxide is used for several urological procedures and may potentially cause carbon dioxide accumulation because the retroperitoneal space offers less of a barrier to carbon dioxide diffusion than the peritoneum. The retroperitoneal space is very vascular, contains areolar tissue and is not as limited as the peritoneum, so that absorption of carbon dioxide may be greater during retroperitoneal than intraperi toneal laparoscopy. Previous studies differed concerning the extent of carbon dioxide absorption during retroperitoneoscopy compared with intraperitoneal laparoscopy. In pigs, PaCO2 increased to the same extent whether carbon dioxide was insufflated intra- or retroperitoneally.3 In dogs, extraperitoneal insufflation led to less carbon dioxide absorption than intraperitoneal insufflation.4 In humans undergoing retroperitoneoscopy for renal surgery, Ng et al.5 did not observe greater absorption of carbon dioxide in comparison with transperitoneal laparoscopy, but Wolf et al. 6 found that carbon dioxide absorption was greater in patients when the retroperitoneal approach was used for renal surgery than when the transperitoneal approach was used. In the present study we measured carbon dioxide absorption in patients undergoing retroperitoneal renal surgery using a metabolic monitor. Carbon dioxide absorption was compared with absorption in a group of patients undergoing intraperitoneal laparoscopy for cholecystectomy.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
After ethics committee approval and informed consent (Henri Mondor hospital ethical committee), 30 patients undergoing elective surgery under general anaesthesia were studied. We studied three groups of patients: the first (n=10) had retroperitoneoscopy for renal (n=7) or adrenal surgery (n=3), the second (n=10) had laparoscopic cholecystectomy and the third (n=10) had orthopaedic surgery. Standardized anaesthesia was used in all patients, consisting of propofol for induction (2.5–3.0 mg kg–1) and maintenance of general anaesthesia together with repeated doses of fentanyl (1.5–2.0 µg kg–1). Atracurium (0.5 mg kg–1) was given to facilitate tracheal intubation and when required during peritoneal and retroperitoneal surgery. All patients breathed oxygen 40% and nitrogen 60%, delivered by continuous positive pressure ventilation through a non-rebreathing circuit (Bird 8400S, Bilthoven, The Netherlands). End-tidal carbon dioxide was measured continuously using a mainstream infrared analyser (N1000; Nellcor Puritan Bennett, Courtaboeuf, France). Controlled ventilation was adjusted continuously throughout anaesthesia to maintain end-tidal carbon dioxide between 4.2 and 4.5%. In patients undergoing retroperitoneoscopy, PaCO2 was measured before and every 30 min after carbon dioxide insufflation from a radial artery catheter and the arterial to end-tidal carbon dioxide difference was calculated. In all patients, central body temperature (oesophageal probe) was maintained within the normal range (36–37°C) with an air-pulsed warming blanket (Bair Hugger; Augustine Medical, Eden Prairie, MN, USA). Whole-body oxygen consumption and carbon dioxide production were measured continuously with a Deltatrac metabolic monitor connected to the ventilator (Datex, Limonest, France). To prevent fluctuations in inspired oxygen concentration, which are a source of error of measurement of oxygen consumption,7 a 5-litre stainless steel tank was connected between the oxygen–air blender and the ventilator. Measurements made during mechanical ventilation have a precision of 6%.8 Oxygen consumption and carbon dioxide production, standardized to body surface area, were calculated and averaged for periods of time of at least 20 min before carbon dioxide insufflation or surgery (T0) and for 30-min periods during insufflation. Carbon dioxide production was also measured for 10–20 min after exsufflation or at the end of surgery. In all patients undergoing retroperitoneal surgery, a chest x-ray was performed 30 min after recovery.

Statistical analysis
Data are expressed as mean (SD) for absolute values of V·O2, V·CO2 and also as percentage of the variation in V·CO2 at T0. Differences between the three groups were studied using two-way analysis of variance (ANOVA) with repeated measures (Statview 5.0 package, SAS Institute Inc., Cary, NC, USA). If there was a significant time x group interaction, a Scheffé ANOVA post hoc test was used to study differences between groups at each time of measurement. To compare data in each group, one-way ANOVA with repeated measures was performed. P<0.05 was considered significant. The sample size was calculated on the basis of carbon dioxide production between 30 and 60 min. We chose arbitrarily to detect a difference of 25 ml min–1 m–2 in carbon dioxide between retroperitoneal and intraperitoneal laparoscopy groups with a standard deviation of 18 ml min–1 m–2.9


    Results
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
Baseline characteristics of the patients are shown in Table 1. The groups were similar with regard to age and body weight. Durations of anaesthesia and carbon dioxide insufflation were longer in the patients having retroperitoneal laparoscopy than in those having intraperitoneal laparoscopy (P<0.05). In all patients, central body temperature was maintained within normal limits. No patient developed uncontrolled hypercapnia during surgery


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Table 1 Characteristics of the patients. Values are mean (range or SD). *P<0.05 vs intraperitoneal insufflation
 
Oxygen consumption before and during surgery did not differ from its preoperative value and remained similar between the three groups (Table 2). A significant increase in V·CO2 occurred after both intraperitoneal and extraperitoneal carbon dioxide insufflation. During the first 30 min of intraperitoneal insufflation, V·CO2 increased by 15%, from 108 (28) to 124 (30) ml min–1 m–2 (P<0.05) and remained at this value throughout the procedure. After retroperitoneal insufflation, V·CO2 increased by 38, 46 and 63% above baseline values during 0–30, 30–60 and 60–90 min of insufflation respectively (P<0.01). The percentage increase in V·CO2 above baseline values during the periods 0–30, 30–60 and 60–90 min was significantly greater after retroperitoneal than after intraperitoneal insufflation (Fig. 1). After exsufflation, carbon dioxide production returned to baseline values in the intraperitoneal group whereas it remained increased above baseline in the retroperitoneal group (P<0.01). The values of the respiratory coefficient reflected these changes in carbon dioxide production, as oxygen consumption remained constant in the three groups throughout the procedure. The arterial to end-tidal carbon dioxide difference did not increase after retroperitoneal insufflation (Fig. 2). In all patients undergoing retroperitoneal surgery a pneumomediastinum was seen on the chest x-ray performed in the recovery room.


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Table 2 End-tidal carbon dioxide, carbon dioxide and oxygen consumption and respiratory quotient before, during and after retroperitoneal and intraperitoneal laparoscopy. Mean values (SD) are shown as ml min–1 body surface area–1. *P<0.05 vs before intraperitoneal insufflation; **P<0.01 vs before retroperitoneal insufflation
 


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Fig 1 Percentage change in V·CO2 from baseline value in patients undergoing orthopaedic surgery, intraperitoneal laparoscopy and extraperitoneal coelioscopy. *P<0.05 comparing intraperitoneal and extraperitoneal procedures.

 


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Fig 2 Change in alveolo-arterial carbon dioxide difference in the patients undergoing retroperitoneoscopy for renal or adrenal surgery.

 

    Discussion
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
We found that retroperitoneal carbon dioxide insufflation causes more carbon dioxide absorption than peritoneal insufflation. In addition, absorption of carbon dioxide persists after the end of surgery.

We measured the systemic absorption of carbon dioxide with a metabolic monitor connected to the ventilator. This non-invasive equipment is designed to measure carbon dioxide production and oxygen consumption. In the study conditions, the amount of carbon dioxide recovered from the lungs comes from metabolism and from carbon dioxide absorbed from the site of insufflation. The simultaneous measurement of oxygen consumption indicates how much of the change in pulmonary carbon dioxide lung output is the result of metabolism and how much is due to carbon dioxide absorption. The respiratory quotient also indicates the fraction of carbon dioxide production that is from absorption of the insufflated gas. In previous studies of patients undergoing renal surgery under retroperitoneoscopy, carbon dioxide absorption was calculated from the values of the minute ventilation volume and measurements of end-tidal carbon dioxide concentration.5 6 This method is inherently flawed because the integral of exhaled flow multiplied by the instantaneous carbon dioxide concentration is needed for accurate measurement of the quantity of carbon dioxide expired. In addition, expiratory flows and volumes measured from anaesthesia apparatus are rather inaccurate.10 In the present study, whole-body oxygen consumption remained stable during the different periods of the anaesthetic and surgical procedures and was similar for each group of patients, suggesting that the part of carbon dioxide production related to whole-body metabolism remained stable throughout the study and between patient groups. In addition, end-tidal carbon dioxide was maintained at its physiological value throughout the study. Therefore the increase in carbon dioxide production or respiratory quotient could be directly related to the absorption of carbon dioxide from the site of insufflation. In the patients undergoing peritoneal laparoscopy, the increase in carbon dioxide production was small (about 10–15% of the basal value) and was similar in magnitude to the value reported in previous studies during laparoscopic cholecystectomy.9 11 At the end of exsufflation, carbon dioxide production returned to its basal value during peritoneal laparoscopy, suggesting that no persistence of carbon dioxide occurred. In the patients undergoing retroperitoneoscopy, carbon dioxide absorption accounted for 40–60% of the basal value, with a tendency to a steady increase throughout the period of insufflation. Similar findings were observed during retroperitoneal insufflation in the pelvis by Mullet et al.,9 who suggested that continued dissection of the retroperitoneal space could increase the area of contact with carbon dioxide. In patients undergoing retroperitoneoscopy, large interindividual variations in carbon dioxide production were observed: in some patients carbon dioxide production increased to 200% of the control value. In these patients end-tidal carbon dioxide could be maintained within normal values by adjustment of the ventilator; however, this could change lung volumes and dead space, and this could affect the alveolo-arterial carbon dioxide difference. This was not seen in the present study. This observation supports previous studies in which the alveolo-arterial gradient did not increase in patients undergoing laparoscopic cholecystectomy under general anaesthesia with controlled ventilation.11 12 In contrast to peritoneal insufflation, in which carbon dioxide output immediately fell at cessation of insufflation, the carbon dioxide output remained high after retroperitoneoscopy. Persistent accumulation of carbon dioxide during the early postoperative period should be considered in the postoperative care of such patients.

In conclusion, retroperitoneal carbon dioxide insufflation allows much greater absorption of carbon dioxide than during intraperitoneal insufflation. Carbon dioxide absorption increases with time during retroperitoneal insufflation and carbon dioxide absorption persists after exsufflation.


    References
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 Abstract
 Introduction
 Methods
 Results
 Discussion
 References
 
1 Wittgen CM, Andrus CH, Fitzgerald SD, et al. Analysis of the hemodynamic and ventilatory effects of laparoscopic cholecystectomy. Arch Surg 1991; 126: 997–1000[Abstract]

2 Joris J, Ledoux D, Honore P, Lamy M. Ventilatory effects of CO2 insufflation during laparoscopic cholecystectomy. Anesthesiology 1991; 75: A121

3 Baird JE, Granger R, Klein R, et al. The effects of peritoneal carbon dioxide insufflation on hemodynamics and arterial carbon dioxide. Am J Surg 1999; 177: 164–6[CrossRef][ISI][Medline]

4 Wolf JS, Carrier S, Stoller ML. Intraperitoneal versus extraperitoneal insufflation of carbon dioxide as for laparoscopy. J Endourol 1995; 9: 63–6[ISI][Medline]

5 Ng CS, Gill IS, Sung GT, Whalley DG, Graham R, Schweizer D. Retroperitoneoscopic surgery is not associated with increased carbon dioxide absorption. J Urol 1999; 162: 1268–72[ISI][Medline]

6 Wolf JS Jr, Monk TG, McDougall EM, et al. The extraperitoneal approach and subcutaneous emphysema are associated with greater absorption of carbon dioxide during laparoscopic renal surgery. J Urol 1995; 154: 959–63[ISI][Medline]

7 Bracco D,Chiolero R, Pasche O, Revelly JP. Failure in measuring gas exchange in the ICU. Chest 1995; 107: 1406–10[Abstract/Free Full Text]

8 Tissot S, Delafosse B, Bertrand O, Bouffard Y, Viale JP, Annat G. Clinical validation of the Deltatrac monitoring system in mechanically ventilated patients. Intensive Care Med 1995; 21: 149–53[ISI][Medline]

9 Mullet CE, Viale JP, Sagnard PE, et al. Pulmonary CO2 elimination during surgical procedures using intra- or extraperitoneal CO2 insufflation. Anesth Analg 1993; 76: 622–6[Abstract]

10 Liu N, Beydon L, Bach B, et al. A study of 11 ventilators for anesthesia: laboratory testing. Ann Fr Anesth Reanim 1992; 11: 502–8[ISI][Medline]

11 Bures E, Fusciardi J, Lanquetot H, et al. Ventilatory effects of laparoscopic cholecystectomy. Acta Anaesthesiol Scand 1996; 40: 566–73[ISI][Medline]

12 Girardis M, Da Broi U, Antoutto G, Pasetto A. The effect of laparoscopic cholecystectomy on cardiovascular function and pulmonary gas exchange. Anesth Analg 1996; 39: 617–32