- Email: [email protected]
Conventional pneumoperitoneum compared with abdominal wall lift for laparoscopic cholecystectomy
British Journal of Anaesthesia 1995; 75: 567–572
Conventional pneumoperitoneum compared with abdominal wall lift for laparoscopic cholecystectomy L. LINDGREN, A.-M. KOIVUSALO AND I. KELLOKUMPU
Summary We have compared, in a randomized study, conventional carbon dioxide pneumoperitoneum with abdominal wall lift in 25 patients undergoing laparoscopic cholecystectomy. Intra-abdominal pressure (IAP) (11 (SD 2) mm Hg vs 2.7 (9) mm Hg) (P 0.01) and total amount of carbon dioxide used (40 (23) litre vs 9 (7) litre) (P 0.001) were significantly less with abdominal wall lift. Pulmonary compliance was significantly greater (P 0.01) in the abdominal wall lift group throughout operation. During the first 15 min of insufflation, arterial pressures were lower with abdominal wall lift (P 0.05). In the conventional pneumoperitoneum group, femoral vein pressure increased (P 0.01) and remained elevated for 3 h in the recovery room. Postoperative drowsiness was of significantly longer duration in the conventional pneumoperitoneum group than in the abdominal wall lift group (98 (46) min vs 13 (34) min) (P 0.01). Postoperative nausea and vomiting and right shoulder pain occurred more often in patients with conventional pneumoperitoneum (P 0.05). We conclude that the benefits of abdominal wall lift may be attributed to avoiding excessive carbon dioxide and high IAP. (Br. J. Anaesth. 1995; 75: 567–572) Key words Surgery, laparoscopy. Carbon dioxide, insufflation. Carbon dioxide, pneumoperitoneum.
Laparoscopic cholecystectomy has rapidly gained wide acceptance for removal of gallstones as it has several advantages over the conventional open laparotomy technique, including shorter duration of hospitalization [1, 2]. The induction and maintenance of a pneumoperitoneum, however, has several adverse respiratory and haemodynamic consequences. Carbon dioxide is absorbed from the peritoneal cavity resulting in hypercapnia. Insufflation causes intra-abdominal distension and has significant effects on mechanical ventilation, causing an increase in peak inspiratory pressures increasing the need for increased minute volume of ventilation [3], and a decrease in pulmonary compliance [4]. Pneumoperitoneum with increased intraabdominal pressure (12–15 mm Hg) increases heart rate, systemic vascular resistance, arterial and central venous pressures and decreases cardiac output [5]. These changes may be deleterious to patients with
compromised cardiorespiratory function. Abdominal insufflation also causes an increase in femoral venous pressure (FVP) which may predispose to deep venous thrombosis [6]. Furthermore, 30–40 % of patients complain of right shoulder pain after conventional carbon dioxide insufflation [7]. Abdominal wall lift has been introduced to laparoscopic cholecystectomy in order to reduce some of the adverse effects caused by carbon dioxide and high intra-abdominal pressure (IAP). With this method, IAP can be maintained at 1–4 mm Hg and insufflation with low volumes of carbon dioxide of only 2–6 litre is required [8]. Rademaker and coworkers [9] compared abdominal wall retraction with conventional pneumoperitoneum in pigs. During retraction, changes in gas exchange and haemodynamic state were minimal. The aim of the present study was to compare conventional carbon dioxide pneumoperitoneum (IAP 12–15 mm Hg) with abdominal wall lift using a mechanical device and minimal carbon dioxide insufflation during laparoscopic cholecystectomy.
Patients and methods After obtaining Ethics Committee approval and informed consent, we studied 26 ASA I–II patients undergoing elective laparoscopic cholecystectomy. Patients were allocated randomly to one of two groups. Patients in group 1 underwent standard laparoscopic cholecystectomy with carbon dioxide insufflation to achieve conventional pressure pneumoperitoneum (IAP 12–15 mm Hg) (conventional pneumoperitoneum group). In group 2 an abdominal wall lift method was used (AWL group). A small amount of carbon dioxide (1.5–3.8 litre) was insufflated with the Hasson technique to see the peritoneal cavity. A Hoffman’s trocar was then introduced into the abdominal cavity through a small incision in the upper left abdomen. The trocar was then brought across and beneath the rectus abdominus muscles and falciform ligament under direct vision and then left the abdomen through a small incision in the upper right abdomen. Both ends of the trocar were attached to a horizontal bar placed at the level of the xiphoid process, 30 cm above the L. LINDGREN, MD, PHD, A.-M. KOIVUSALO, MD (Department of Anaesthesia); I. KELLOKUMPU, MD, PHD (Department of Surgery); IV Department of Surgery, Helsinki University Hospital, Kasarmikatu 11–13, FIN-00130 Helsinki, Finland. Accepted for publication: June 2, 1995. Correspondence to A.-M.K.
568
British Journal of Anaesthesia
Figure 1 Schematic illustration of the abdominal wall lift method. Dotted line represents the contour of the abdomen with conventional carbon dioxide insufflation.
chest. With this technique, the anterior abdominal wall could be elevated 10–15 cm upwards to create the necessary operating space (fig. 1). Thereafter carbon dioxide insufflation was kept at a minimum. All operations were performed by the same experienced surgeon (I.K.). The severity of biliary symptoms was graded according to McSherry and colleagues [10] on a scale from 0 to 3; 0 gastrointestinal symptoms not caused by gallstones; 1 infrequent episodes of biliary colic without cholecystitis; 2 frequent episodes of biliary colic, at intervals of about 1 month; 3 acute cholecystectomy or obstructive jaundice without acute cholecystitis. Before operation patients received a s.c. injection of low-molecular-weight heparin and antithrombotic stockings were applied. Patients were premedicated with oral diazepam 0.2 mg kg1 approximately 60 min before arrival in the operation theatre, and glycopyrronium 3 g kg1 was given to all patients. Before induction of anaesthesia, volume loading was performed using Ringer’s lactate 8 ml kg1 and during operation 10 ml kg1 h1 together with 6 % hydroxyethyl starch (Plasmafusin, Pharmacia AB, Sweden) 500 ml. Anaesthesia was induced with fentanyl 2 g kg1 followed by thiopentone 3–6 mg kg1. Neuromuscular block was produced using vecuronium, and anaesthesia was maintained with isoflurane at an end-tidal concentration of about 1.2 %, 1 MAC, and oxygen in air (FIO2 0.40). The concentration of isoflurane was increased by 0.1 % if required for increases in heart rate and arterial pressure of greater than 30 % persisting for more than 5 min. The concentrations of isoflurane were recorded. Peroperative analgesia was produced with fentanyl 0.1 mg h1. Patients’ lungs were ventilated mechanically at a frequency of 10 b.p.m. (Servo 900, Siemens Elema, Sweden) and end-tidal carbon dioxide concentration was maintained within the normal range (4.5–5.1 %). Inspiratory time was set at 25 % and pause time at 10 % of the respiratory cycle.
End-expiratory positive pressure was not used. A urinary bladder catheter and nasogastric tube were inserted. After induction of anaesthesia, the right subclavian and right femoral veins were cannulated for measurement of central venous (CVP) and femoral venous (FVP) pressures. The pressure transducers were positioned at the midthoracic level near the left shoulder. To compensate for any error induced by the head-up tilt position, FVP was measured separately at a horizontal and then at 20° head-up tilt position before carbon dioxide insufflation in each patient. The shift between the two positions was added to FVP recordings when measured with headup tilt during the study. Heart rate (HR), indirect systolic, diastolic and mean arterial pressures (SAP, DAP, MAP), peripheral arterial oxygen saturation (SpO2 ), CVP, FVP, tympanic membrane temperature (Cardiocap Ultima, Datex Ltd, Finland) and IAP (Laparoflator Electronic 3509, Wiest Medizintechnik GmbH, Germany) were recorded before skin incision and 5, 15, 25, 35, 45 and 55 min after carbon dioxide insufflation and before extubation. Minute volume, end-tidal carbon dioxide concentration, pulmonary dynamic compliance [11] and end-tidal isoflurane concentration were monitored continuously using the sidestream sensor connected to the anaesthetic monitor (Side Stream Spirometry, Datex Ultima, Finland). If HR exceeded 100 beat min1, patients received metoprolol l–3 mg i.v. Surgery was undertaken with the patient in a 20° head-up tilt position. Data before insufflation and before extubation were obtained with the patient in the horizontal position but during surgery in the 20° head-up body tilt position. Residual neuromuscular block was antagonized using neostigmine and glycopyrronium. The trachea was extubated at an endtidal isoflurane concentration of 0.2 %. The amount of intraoperative fluids and drugs, duration of operation and total amount of carbon dioxide insufflation were recorded.
Abdominal wall lift for laparoscopy
569
Haemodynamic variables were recorded during the 3-h recovery room period. Pain was measured using a visual analogue scale (VAS 0–10). If the pain score was greater than 5, patients received oxycodone 0.07 mg kg1 i.v. If the pain score remained greater than 5 for more than 15 min, the dose of oxycodone was repeated and thereafter ketorolac 30 mg i.v. was given. Drowsiness was scored as follows: fully awake 0; sedated, responding to commands 1; and drowsy, hardly responding to commands 2. Postoperative nausea and vomiting (PONV retching, nausea or vomiting) were recorded in the recovery room. Vomiting was treated with droperidol 1.25 mg i.m. if necessary. Patients were interviewed on the first postoperative day with special reference to pain and its location, and also PONV. Drug administration was also recorded. STATISTICAL ANALYSIS
Within-group changes were analysed using one-way ANOVA with PLSD correction factor (least significant test). The differences between the study groups were analysed using a two-way ANOVA with PLSD correction or with Fisher’s exact test for small groups [12]. The calculations were performed using Stat View 512TM software (Brain Power Inc., Calabasas, CA, USA). Data are expressed as mean (SD). P 0.05 was considered statistically significant.
Table 2 Surgical and anaesthetic data (mean (SD) or number). ERCP Endoscopic retrograde cholangiopancreatography, EST endoscopic sphincterotomy. Degree of morbidity (McSherry score 0–3). *P 0.05, **P 0.001 between groups Pneumoperitoneum group AWL group (n 13) (n ⫽ 12) Previous operations 4 McSherry score 1.6 (0.8) Preoperative ERCP/EST 2/1 Difficult anatomy 3 5.9 (2.6)** Initial CO2 (1) 40 (23)** Total CO2(1) Intraoperative cholangiography 10 Intraoperative complications 0 Operation time (min) 103 (54) Hospital stay (days) 2.0 (0.6) Total amount of 1 6 (1) Fentanyl (g kg ) 0.17 (0.03) Vecuronium (mg kg1) End-tidal isoflurane at 25 min of pneumoperitoneum for 10 min 1.25 (0.12)*
4 1.6 (0.6) 4/2 3 2.5 (0.8) 8.6 (7.4) 8 0 86 (20) 1.8 (0.6) 5.5 (1) 0.15 (0.03)
1.11 (0.12)
Results The two groups were comparable in age, weight, height, sex, ASA physical status and duration of operation (tables 1, 2). One patient in the AWL group was excluded because insertion of the nasogastric tube caused massive epistaxis. In the conventional pneumoperitoneum group, one patient was receiving pindolol and one ramipril. In the AWL group, two patients were receiving enalapril for hypertension. These patients received their regular medication 1 h before operation together with premedication. There were no perioperative complications. The morbidity of the biliary disease, as assessed according to McSherry and colleagues [10], was comparable in the two groups. Chronic cholecystitis with adhesions and scarring was encountered in three patients in both groups (table 2). In the conventional pneumoperitoneum group, pulmonary compliance decreased 5 min after insufflation and remained at a significantly lower level (P 0.01) during operation compared with the Table 1 Patient data for those undergoing elective laparoscopic cholecystectomy (mean (SD or range) or number). AWL Abdominal wall lift group
Age (yr) Sex (F/M) Weight (kg) Height (cm) ASA I/II
Pneumoperitoneum group (n 13)
AWL group (n 12)
49 (31–69) 11/2 77 (12) 168 (8) 9/4
49 (28–63) 11/1 71 (13) 163 (8) 6/6
Figure 2 Pulmonary compliance during laparoscopic cholecystectomy in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (control) (mean, SD). Pre Immediately before carbon dioxide insufflation, ext after deflation of carbon dioxide before extubation. ***P 0.001 from baseline (one-way ANOVA). ††P 0.01, †††P 0.001 between groups (two-way ANOVA).
AWL group (fig. 2) A higher concentration of isoflurane was required in the conventional pneumoperitoneum group 25 min after insufflation for about 10 min (P 0.05) (table 2). Minute ventilation increased from 6.7 (0.9) to 7.3 (1.1) litre towards the end of operation in the conventional pneumoperitoneum group (P 0.001). In the AWL group, these values were 6.1 (0.7) and 6.4 (1.1) litre (P 0.05), respectively. There were no differences in end-tidal carbon dioxide concentrations between the two groups. Tympanic membrane temperature did not change significantly in each group. Mean baseline HR in both groups was comparable. Five minutes after insufflation, HR increased significantly (P 0.001) in the conventional pneumoperitoneum group and remained at that level for 45 min. In the AWL group, HR increased 15 min after insufflation (P 0.01) but returned to baseline values at 35 min. In one patient in the conventional pneumoperitoneum
570
British Journal of Anaesthesia
Figure 3 Heart rate (HR), systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures during the study in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (mean, SD). Pre Immediately before carbon dioxide insufflation. Ext After deflation of carbon dioxide before extubation. *P 0.05, **P 0.01, ***P 0.001 from baseline. †P 0.05, ††P 0.01 between groups. The differences in response during the first 15 min of insufflation are presented.
Figure 4 Femoral (FVP) and central (CVP) vein pressures during operation and in the recovery room (RR) in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (mean, SD). Pre Immediately before carbon dioxide insufflation. *P 0.05, **P 0.001 from baseline, †P 0.05, ††P 0.01, †††P 0.001 between groups. The differences in response during the first 15 min of insufflation are presented.
group, HR exceeded 100 beat min1 15 min after insufflation. She received metoprolol 2 mg. In the AWL group, no metoprolol was needed. HR responses did not differ statistically between the two
groups. In both groups MAP increased significantly (P 0.001) 5 min after completing the insufflation and remained elevated throughout operation. In the conventional pneumoperitoneum group, the increase in MAP was significantly greater during the first 15 min than in the AWL group (P 0.05). Similar changes were noted also in SAP (P 0.05) and DAP (P 0.01) (fig. 3). In the conventional pneumoperitoneum group, CVP increased from 7.5 (3.6) mm Hg during 45 min of insufflation to 10.4 (5.6) mm Hg. In the AWL group, these values were 8 (2.6) and 4.1 (3.5) mm Hg, respectively. At 45 min of insufflation there was a significant difference (P 0.01) between the two groups. On arrival in the recovery room, CVP was significantly higher in the conventional pneumoperitoneum group than in the AWL group (9.3 (3.6) vs 5.2 (3.0) mm Hg (P 0.01) (fig. 4). FVP increased by approximately 134 % (P 0.01) after carbon dioxide insufflation in the conventional pneumoperitoneum group but remained at baseline levels in the AWL group. FVP remained significantly higher (P 0.01) in the conventional pneumoperitoneum group than in the AWL group during the recovery room period (fig. 4). In the conventional pneumoperitoneum group, IAP was 10.4 (3) mm Hg at 5 min and 11 (2) mm Hg at 15 min after insufflation. In the AWL group, these values were 4 (6) and 2.7 (9) mm Hg, respectively (P 0.01). In the AWL group, IAP could not be measured after 15 min because the insufflation port was closed. The total amount of carbon dioxide used was 40 (23) litre in the conventional pneumoperitoneum group and 8.6 (7.4) litre in the AWL group (P 0.001) (table 2). The total amount of fluids administered to both groups was not significantly different. The total amount of Ringer’s lactate solution used was
Abdominal wall lift for laparoscopy
571
Table 3 Postoperative characteristics in the study groups. Consumption number of doses per group. *P 0.05, **P 0.01 between groups Pneumoperitoneum group AWL group (n 13) (n 12) Consumption of oxycodone in the recovery room Consumption of oxycodone during 24 h Consumption of ketorolac during 24 h (30 mg dose⫺1) No. of patients with no pain in recovery room No. of patients with no pain during 24 h Duration of drowsiness (min) No. of patients needing droperidol for vomiting No. of patients with right shoulder pain during 24 h
25
22
28
16
21
9
5*
1
1
3
98 (46)**
13 (34)
6*
1
6*
1
1891 (822) ml in the conventional pneumoperitoneum group and 1754 (482) ml in the AWL group (ns). The values for hydroxyethyl starch were 579 (227) ml and 554 (121) ml, respectively (ns). Postoperative pain scores did not differ between the two groups during the 3-h recovery room period. Postoperative drowsiness (score 2) lasted 98 (46) min in the conventional pneumoperitoneum group and 13 (34) min in the AWL group (P 0.001) On the first postoperative day, six patients (46 %) in the conventional pneumoperitoneum group and one patient (8 %) in the AWL group complained of pain in the right shoulder (P 0.05). During the first 24 h, six patients in the conventional pneumoperitoneum group and one patient in the AWL group suffered from PONV which required treatment with droperidol (P 0.05). During the first 24 h, one patient in the conventional pneumoperitoneum group and three patients in the AWL group did not need any pain relief. In the conventional pneumoperitoneum group 21 doses of ketorolac and in the AWL group nine doses were given. The values for oxycodone were 28 and 16, respectively (ns) (table 3).
Discussion Our results demonstrated that the abdominal wall lift method using minimal carbon dioxide insufflation for laparoscopic cholecystectomy was associated with fewer peroperative pulmonary events and a reduction in haemodynamic changes. It also appeared to provide a faster and more uneventful postoperative recovery compared with conventional pneumoperitoneum. Pulmonary compliance was significantly greater using the abdominal wall lift method than with conventional carbon dioxide insufflation. The decrease in pulmonary compliance caused by conventional carbon dioxide pneumoperitoneum was
similar to that reported by Bardoczky and co-workers [4]. Abdominal distension is known to elevate the diaphragm and abdominal part of the chest wall, restricting lung expansion. This leads to increased airway pressures associated with decreased pulmonary compliance. To maintain minute ventilation constant, increased peak and plateau airway pressures are needed with possible haemodynamic impairment, especially in obese patients [4]. Carbon dioxide is absorbed rapidly into the circulation through the peritoneum, resulting in respiratory acidosis. Because of the carbon dioxide load, increased ventilatory drive persists during the recovery phase. By avoiding excessive carbon dioxide with the abdominal wall lift method, less ventilatory work is required during and after the procedure. Carbon dioxide produces direct and indirect haemodynamic effects, causing peripheral vasodilatation and depressing myocardial contractility. Carbon dioxide activates the central nervous system and evokes sympathoadrenal responses, increasing myocardial contractility and causing tachycardia and hypertension. During mechanical ventilation, venous return is impaired resulting in increased peripheral vascular resistance and reduced cardiac output [13]. Carbon dioxide insufflation has been reported to have caused serious gas emboli which may lead to life threatening cardiac arrhythmias [14]. The risk of gas embolism is lower with the abdominal wall lift method as the amount of carbon dioxide used is significantly less. We have demonstrated that increases in arterial pressures are more marked with conventional pneumoperitoneum; this may lead to increased myocardial work. High IAP results in an increase in cardiac afterload and elevated systemic vascular resistance [5], which are also known to be risk factors in patients with myocardial ischaemia causing an increase in myocardial oxygen consumption. High preload also diminishes coronary flow by decreasing coronary artery perfusion pressure. Cunningham and co-workers [15] found that carbon dioxide insufflation increased left ventricular end-systolic wall stress, and left ventricular end-diastolic area decreased after head-up tilt while left ventricular ejection fraction was unaffected. These changes in left ventricular performance may be especially deleterious in patients with compromised cardiac function. The abdominal wall lift method, enabling minimal carbon dioxide insufflation and lower IAP, may confer some benefit to patients with pre-existing myocardial disease. In our conventional pneumoperitoneum group, CVP increased, as has been demonstrated previously by Odeberg and colleagues [16]. The increase in CVP and its slow return to preanaesthetic values may be the result of increased IAP, forcing blood from the abdominal organs into the central venous reservoir; this blood then slowly returns to the splanchnic region [17]. Also, elevated vasopressin concentrations seen in an earlier study [18] can cause elevation in CVP. In our study CVP remained at a significantly lower level with the abdominal wall lift method compared with conventional pneumoperitoneum.
572 Increased IAP related to carbon dioxide pneumoperitoneum with head-up tilt decreases venous return from the lower extremities and increases FVP [19], thereby increasing the risk of deep venous thrombosis [6] or pulmonary embolism [19]. For these reasons every effort should be made to reduce venous stasis by the use of antiembolic stockings and low-molecular-weight heparin. Patients with a history of thromboembolic disease are at increased risk of developing thromboembolic complications. It is interesting that FVP remained elevated during the whole 3-h recovery period in the conventional pneumoperitoneum group. When the abdominal wall lift method was used, FVP remained at baseline levels during operation and recovery. The incidence of right shoulder pain in the conventional group was similar to that reported by Scheinin and colleagues [7]. In the AWL group, right shoulder pain was virtually absent. It has been suggested that insufflated carbon dioxide, diaphragmatic distention, or both, may be the cause of irritation at the phrenic nerve distribution area. Fredman and colleagues [20] noted the removal of the remaining exogenous carbon dioxide at the end of operation reduced the incidence and severity of referred shoulder pain. The use of the abdominal wall lift method with a smaller amount of insufflated carbon dioxide may have protected the patients against right shoulder pain. A reduction in PONV was observed in the AWL group. This may confer some benefits in patients undergoing this procedure on a day-case basis.
British Journal of Anaesthesia
4. 5. 6.
7.
8. 9.
10.
11. 12. 13. 14. 15.
16.
Acknowledgements The authors are indebted to Professor Markku Nurminen, PhD, for statistical advice. 17.
References 1. Joris J, Cigarini I, Legrand M, Jacquet N, De Groote D, Franchimont P, Lamy M. Metabolic and respiratory changes after cholecystectomy performed via laparotomy or laparoscopy. British Journal of Anaesthesia 1992; 69: 341–345. 2. Berggren U, Gordh T, Grama D, Haglund U, Rastad J, Arvidsson D. Laparoscopic versus open cholecystectomy: hospitalization, sick leave, analgesia and trauma responses. British Journal of Surgery 1994; 81: 1362–1365. 3. Baraka A, Jabbour S, Hammoud R, Aouad M, Najjar F, Khoury G, Sibai A. End-tidal carbon dioxide tension during
18. 19. 20.
laparoscopic cholecystectomy. Anaesthesia 1994; 49: 304–306. Bardoczky GI, Engelman E, Levarlet M, Simon P. Ventilatory effects of pneumoperitoneum monitored with continuous spirometry. Anaesthesia 1993; 48: 309–311. Noirot D, Joris J, Legrand M, Lamy M. Hemodynamic changes during pneumoperitoneum for laparoscopic cholecystectomy. Anesthesiology 1992; 77: A69. Beebe D, McNevin M, Belani K, Letourneau J, Crain M, Goodale R. Evidence of venous stasis after abdominal insufflation for laparoscopic cholecystectomy. Anesthesiology 1992; 77: A148. Scheinin B, Kellokumpu I, Lindgren L, Haglund C, Rosenberg PH. Effect of intraperitoneal bupivacaine on pain after laparoscopic cholecystectomy. Acta Anaesthesiologica Scandinavica 1995; 39: 195–198. Banting S, Shimi S, Van der Velpen G, Cushieri A. Abdominal wall lift. Surgical Endoscopy 1993; 7: 57–59. Rademaker B, Meyer D, Bannenberg J, Kalkman C. Laparoscopy using abdominal wall retraction versus pneumoperitoneum: effects on hemodynamics and gas exchange. Anesthesiology 1994; 81: A763. McSherry C, Ferstenberg H, Calhoun F, Lahman E, Virshup M. The natural history of diagnosed gallstone disease in symptomatic and asymptomatic patients. Annals of Surgery 1985; 202: 59–63. Meriläinen P, Hänninen H, Tuomaala L. A novel sensor for routine continuous spirometry of intubated patients. Journal of Clinical Monitoring 1993; 9: 374–380. Miettinen O. Comment. Journal of the American Statistical Association 1974; 69: 380–382. Cullen D, Eger E. Cardiovascular effects of carbon dioxide in man. Anesthesiology 1974; 41: 345–349. Shanta T, Harden J. Laparoscopic cholecystectomy: anesthesia-related complications and guidelines. Surgical Laparoscopy and Endoscopy 1991; 1: 173–178. Cunningham A, Turner J, Rosenbaum S, Rafferty T. Transoesophageal echocardiographic assessment of haemodynamic function during laparoscopic cholecystectomy. British Journal of Anaesthesia 1993; 70: 621–625. Odeberg S, Ljungqvist O, Svenberg T, Gannedahl P, Bäckdahl M, von Rosen A, Sollevi A. Haemodynamic effects of pneumoperitoneum and the influence of posture during anaesthesia for laparoscopic surgery. Acta Anaesthesiologica Scandinavica 1994; 38: 276–283. Kelman G, Swapp G, Smith I, Benzie R, Gordon N. Cardiac output and arterial blood-gas tensions during laparoscopy. British Journal of Anaesthesia 1972; 44: 1155–1162. Joris J, Lamy M. Neuroendocrine changes during pneumoperitoneum for laparoscopic cholecystectomy. British Journal of Anaesthesia 1993; 70: A.33. Jorgensen J, Gillies R, Lalak N, Hunt D. Lower limb venous hemodynamics during laparoscopy: an animal study. Surgical Laparoscopy and Endoscopy 1994; 4: 32–35. Fredman B, Jedeikin R, Olsfanger D, Flor P, Gruzman A. Residual pneumoperitoneum: a cause of postoperative pain after laparoscopic cholecystectomy. Anesthesia and Analgesia 1994; 79: 152–154.
Conventional pneumoperitoneum compared with abdominal wall lift for laparoscopic cholecystectomy L. LINDGREN, A.-M. KOIVUSALO AND I. KELLOKUMPU
Summary We have compared, in a randomized study, conventional carbon dioxide pneumoperitoneum with abdominal wall lift in 25 patients undergoing laparoscopic cholecystectomy. Intra-abdominal pressure (IAP) (11 (SD 2) mm Hg vs 2.7 (9) mm Hg) (P 0.01) and total amount of carbon dioxide used (40 (23) litre vs 9 (7) litre) (P 0.001) were significantly less with abdominal wall lift. Pulmonary compliance was significantly greater (P 0.01) in the abdominal wall lift group throughout operation. During the first 15 min of insufflation, arterial pressures were lower with abdominal wall lift (P 0.05). In the conventional pneumoperitoneum group, femoral vein pressure increased (P 0.01) and remained elevated for 3 h in the recovery room. Postoperative drowsiness was of significantly longer duration in the conventional pneumoperitoneum group than in the abdominal wall lift group (98 (46) min vs 13 (34) min) (P 0.01). Postoperative nausea and vomiting and right shoulder pain occurred more often in patients with conventional pneumoperitoneum (P 0.05). We conclude that the benefits of abdominal wall lift may be attributed to avoiding excessive carbon dioxide and high IAP. (Br. J. Anaesth. 1995; 75: 567–572) Key words Surgery, laparoscopy. Carbon dioxide, insufflation. Carbon dioxide, pneumoperitoneum.
Laparoscopic cholecystectomy has rapidly gained wide acceptance for removal of gallstones as it has several advantages over the conventional open laparotomy technique, including shorter duration of hospitalization [1, 2]. The induction and maintenance of a pneumoperitoneum, however, has several adverse respiratory and haemodynamic consequences. Carbon dioxide is absorbed from the peritoneal cavity resulting in hypercapnia. Insufflation causes intra-abdominal distension and has significant effects on mechanical ventilation, causing an increase in peak inspiratory pressures increasing the need for increased minute volume of ventilation [3], and a decrease in pulmonary compliance [4]. Pneumoperitoneum with increased intraabdominal pressure (12–15 mm Hg) increases heart rate, systemic vascular resistance, arterial and central venous pressures and decreases cardiac output [5]. These changes may be deleterious to patients with
compromised cardiorespiratory function. Abdominal insufflation also causes an increase in femoral venous pressure (FVP) which may predispose to deep venous thrombosis [6]. Furthermore, 30–40 % of patients complain of right shoulder pain after conventional carbon dioxide insufflation [7]. Abdominal wall lift has been introduced to laparoscopic cholecystectomy in order to reduce some of the adverse effects caused by carbon dioxide and high intra-abdominal pressure (IAP). With this method, IAP can be maintained at 1–4 mm Hg and insufflation with low volumes of carbon dioxide of only 2–6 litre is required [8]. Rademaker and coworkers [9] compared abdominal wall retraction with conventional pneumoperitoneum in pigs. During retraction, changes in gas exchange and haemodynamic state were minimal. The aim of the present study was to compare conventional carbon dioxide pneumoperitoneum (IAP 12–15 mm Hg) with abdominal wall lift using a mechanical device and minimal carbon dioxide insufflation during laparoscopic cholecystectomy.
Patients and methods After obtaining Ethics Committee approval and informed consent, we studied 26 ASA I–II patients undergoing elective laparoscopic cholecystectomy. Patients were allocated randomly to one of two groups. Patients in group 1 underwent standard laparoscopic cholecystectomy with carbon dioxide insufflation to achieve conventional pressure pneumoperitoneum (IAP 12–15 mm Hg) (conventional pneumoperitoneum group). In group 2 an abdominal wall lift method was used (AWL group). A small amount of carbon dioxide (1.5–3.8 litre) was insufflated with the Hasson technique to see the peritoneal cavity. A Hoffman’s trocar was then introduced into the abdominal cavity through a small incision in the upper left abdomen. The trocar was then brought across and beneath the rectus abdominus muscles and falciform ligament under direct vision and then left the abdomen through a small incision in the upper right abdomen. Both ends of the trocar were attached to a horizontal bar placed at the level of the xiphoid process, 30 cm above the L. LINDGREN, MD, PHD, A.-M. KOIVUSALO, MD (Department of Anaesthesia); I. KELLOKUMPU, MD, PHD (Department of Surgery); IV Department of Surgery, Helsinki University Hospital, Kasarmikatu 11–13, FIN-00130 Helsinki, Finland. Accepted for publication: June 2, 1995. Correspondence to A.-M.K.
568
British Journal of Anaesthesia
Figure 1 Schematic illustration of the abdominal wall lift method. Dotted line represents the contour of the abdomen with conventional carbon dioxide insufflation.
chest. With this technique, the anterior abdominal wall could be elevated 10–15 cm upwards to create the necessary operating space (fig. 1). Thereafter carbon dioxide insufflation was kept at a minimum. All operations were performed by the same experienced surgeon (I.K.). The severity of biliary symptoms was graded according to McSherry and colleagues [10] on a scale from 0 to 3; 0 gastrointestinal symptoms not caused by gallstones; 1 infrequent episodes of biliary colic without cholecystitis; 2 frequent episodes of biliary colic, at intervals of about 1 month; 3 acute cholecystectomy or obstructive jaundice without acute cholecystitis. Before operation patients received a s.c. injection of low-molecular-weight heparin and antithrombotic stockings were applied. Patients were premedicated with oral diazepam 0.2 mg kg1 approximately 60 min before arrival in the operation theatre, and glycopyrronium 3 g kg1 was given to all patients. Before induction of anaesthesia, volume loading was performed using Ringer’s lactate 8 ml kg1 and during operation 10 ml kg1 h1 together with 6 % hydroxyethyl starch (Plasmafusin, Pharmacia AB, Sweden) 500 ml. Anaesthesia was induced with fentanyl 2 g kg1 followed by thiopentone 3–6 mg kg1. Neuromuscular block was produced using vecuronium, and anaesthesia was maintained with isoflurane at an end-tidal concentration of about 1.2 %, 1 MAC, and oxygen in air (FIO2 0.40). The concentration of isoflurane was increased by 0.1 % if required for increases in heart rate and arterial pressure of greater than 30 % persisting for more than 5 min. The concentrations of isoflurane were recorded. Peroperative analgesia was produced with fentanyl 0.1 mg h1. Patients’ lungs were ventilated mechanically at a frequency of 10 b.p.m. (Servo 900, Siemens Elema, Sweden) and end-tidal carbon dioxide concentration was maintained within the normal range (4.5–5.1 %). Inspiratory time was set at 25 % and pause time at 10 % of the respiratory cycle.
End-expiratory positive pressure was not used. A urinary bladder catheter and nasogastric tube were inserted. After induction of anaesthesia, the right subclavian and right femoral veins were cannulated for measurement of central venous (CVP) and femoral venous (FVP) pressures. The pressure transducers were positioned at the midthoracic level near the left shoulder. To compensate for any error induced by the head-up tilt position, FVP was measured separately at a horizontal and then at 20° head-up tilt position before carbon dioxide insufflation in each patient. The shift between the two positions was added to FVP recordings when measured with headup tilt during the study. Heart rate (HR), indirect systolic, diastolic and mean arterial pressures (SAP, DAP, MAP), peripheral arterial oxygen saturation (SpO2 ), CVP, FVP, tympanic membrane temperature (Cardiocap Ultima, Datex Ltd, Finland) and IAP (Laparoflator Electronic 3509, Wiest Medizintechnik GmbH, Germany) were recorded before skin incision and 5, 15, 25, 35, 45 and 55 min after carbon dioxide insufflation and before extubation. Minute volume, end-tidal carbon dioxide concentration, pulmonary dynamic compliance [11] and end-tidal isoflurane concentration were monitored continuously using the sidestream sensor connected to the anaesthetic monitor (Side Stream Spirometry, Datex Ultima, Finland). If HR exceeded 100 beat min1, patients received metoprolol l–3 mg i.v. Surgery was undertaken with the patient in a 20° head-up tilt position. Data before insufflation and before extubation were obtained with the patient in the horizontal position but during surgery in the 20° head-up body tilt position. Residual neuromuscular block was antagonized using neostigmine and glycopyrronium. The trachea was extubated at an endtidal isoflurane concentration of 0.2 %. The amount of intraoperative fluids and drugs, duration of operation and total amount of carbon dioxide insufflation were recorded.
Abdominal wall lift for laparoscopy
569
Haemodynamic variables were recorded during the 3-h recovery room period. Pain was measured using a visual analogue scale (VAS 0–10). If the pain score was greater than 5, patients received oxycodone 0.07 mg kg1 i.v. If the pain score remained greater than 5 for more than 15 min, the dose of oxycodone was repeated and thereafter ketorolac 30 mg i.v. was given. Drowsiness was scored as follows: fully awake 0; sedated, responding to commands 1; and drowsy, hardly responding to commands 2. Postoperative nausea and vomiting (PONV retching, nausea or vomiting) were recorded in the recovery room. Vomiting was treated with droperidol 1.25 mg i.m. if necessary. Patients were interviewed on the first postoperative day with special reference to pain and its location, and also PONV. Drug administration was also recorded. STATISTICAL ANALYSIS
Within-group changes were analysed using one-way ANOVA with PLSD correction factor (least significant test). The differences between the study groups were analysed using a two-way ANOVA with PLSD correction or with Fisher’s exact test for small groups [12]. The calculations were performed using Stat View 512TM software (Brain Power Inc., Calabasas, CA, USA). Data are expressed as mean (SD). P 0.05 was considered statistically significant.
Table 2 Surgical and anaesthetic data (mean (SD) or number). ERCP Endoscopic retrograde cholangiopancreatography, EST endoscopic sphincterotomy. Degree of morbidity (McSherry score 0–3). *P 0.05, **P 0.001 between groups Pneumoperitoneum group AWL group (n 13) (n ⫽ 12) Previous operations 4 McSherry score 1.6 (0.8) Preoperative ERCP/EST 2/1 Difficult anatomy 3 5.9 (2.6)** Initial CO2 (1) 40 (23)** Total CO2(1) Intraoperative cholangiography 10 Intraoperative complications 0 Operation time (min) 103 (54) Hospital stay (days) 2.0 (0.6) Total amount of 1 6 (1) Fentanyl (g kg ) 0.17 (0.03) Vecuronium (mg kg1) End-tidal isoflurane at 25 min of pneumoperitoneum for 10 min 1.25 (0.12)*
4 1.6 (0.6) 4/2 3 2.5 (0.8) 8.6 (7.4) 8 0 86 (20) 1.8 (0.6) 5.5 (1) 0.15 (0.03)
1.11 (0.12)
Results The two groups were comparable in age, weight, height, sex, ASA physical status and duration of operation (tables 1, 2). One patient in the AWL group was excluded because insertion of the nasogastric tube caused massive epistaxis. In the conventional pneumoperitoneum group, one patient was receiving pindolol and one ramipril. In the AWL group, two patients were receiving enalapril for hypertension. These patients received their regular medication 1 h before operation together with premedication. There were no perioperative complications. The morbidity of the biliary disease, as assessed according to McSherry and colleagues [10], was comparable in the two groups. Chronic cholecystitis with adhesions and scarring was encountered in three patients in both groups (table 2). In the conventional pneumoperitoneum group, pulmonary compliance decreased 5 min after insufflation and remained at a significantly lower level (P 0.01) during operation compared with the Table 1 Patient data for those undergoing elective laparoscopic cholecystectomy (mean (SD or range) or number). AWL Abdominal wall lift group
Age (yr) Sex (F/M) Weight (kg) Height (cm) ASA I/II
Pneumoperitoneum group (n 13)
AWL group (n 12)
49 (31–69) 11/2 77 (12) 168 (8) 9/4
49 (28–63) 11/1 71 (13) 163 (8) 6/6
Figure 2 Pulmonary compliance during laparoscopic cholecystectomy in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (control) (mean, SD). Pre Immediately before carbon dioxide insufflation, ext after deflation of carbon dioxide before extubation. ***P 0.001 from baseline (one-way ANOVA). ††P 0.01, †††P 0.001 between groups (two-way ANOVA).
AWL group (fig. 2) A higher concentration of isoflurane was required in the conventional pneumoperitoneum group 25 min after insufflation for about 10 min (P 0.05) (table 2). Minute ventilation increased from 6.7 (0.9) to 7.3 (1.1) litre towards the end of operation in the conventional pneumoperitoneum group (P 0.001). In the AWL group, these values were 6.1 (0.7) and 6.4 (1.1) litre (P 0.05), respectively. There were no differences in end-tidal carbon dioxide concentrations between the two groups. Tympanic membrane temperature did not change significantly in each group. Mean baseline HR in both groups was comparable. Five minutes after insufflation, HR increased significantly (P 0.001) in the conventional pneumoperitoneum group and remained at that level for 45 min. In the AWL group, HR increased 15 min after insufflation (P 0.01) but returned to baseline values at 35 min. In one patient in the conventional pneumoperitoneum
570
British Journal of Anaesthesia
Figure 3 Heart rate (HR), systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures during the study in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (mean, SD). Pre Immediately before carbon dioxide insufflation. Ext After deflation of carbon dioxide before extubation. *P 0.05, **P 0.01, ***P 0.001 from baseline. †P 0.05, ††P 0.01 between groups. The differences in response during the first 15 min of insufflation are presented.
Figure 4 Femoral (FVP) and central (CVP) vein pressures during operation and in the recovery room (RR) in the abdominal wall lift group ( ) and in the conventional pneumoperitoneum group ( ) (mean, SD). Pre Immediately before carbon dioxide insufflation. *P 0.05, **P 0.001 from baseline, †P 0.05, ††P 0.01, †††P 0.001 between groups. The differences in response during the first 15 min of insufflation are presented.
group, HR exceeded 100 beat min1 15 min after insufflation. She received metoprolol 2 mg. In the AWL group, no metoprolol was needed. HR responses did not differ statistically between the two
groups. In both groups MAP increased significantly (P 0.001) 5 min after completing the insufflation and remained elevated throughout operation. In the conventional pneumoperitoneum group, the increase in MAP was significantly greater during the first 15 min than in the AWL group (P 0.05). Similar changes were noted also in SAP (P 0.05) and DAP (P 0.01) (fig. 3). In the conventional pneumoperitoneum group, CVP increased from 7.5 (3.6) mm Hg during 45 min of insufflation to 10.4 (5.6) mm Hg. In the AWL group, these values were 8 (2.6) and 4.1 (3.5) mm Hg, respectively. At 45 min of insufflation there was a significant difference (P 0.01) between the two groups. On arrival in the recovery room, CVP was significantly higher in the conventional pneumoperitoneum group than in the AWL group (9.3 (3.6) vs 5.2 (3.0) mm Hg (P 0.01) (fig. 4). FVP increased by approximately 134 % (P 0.01) after carbon dioxide insufflation in the conventional pneumoperitoneum group but remained at baseline levels in the AWL group. FVP remained significantly higher (P 0.01) in the conventional pneumoperitoneum group than in the AWL group during the recovery room period (fig. 4). In the conventional pneumoperitoneum group, IAP was 10.4 (3) mm Hg at 5 min and 11 (2) mm Hg at 15 min after insufflation. In the AWL group, these values were 4 (6) and 2.7 (9) mm Hg, respectively (P 0.01). In the AWL group, IAP could not be measured after 15 min because the insufflation port was closed. The total amount of carbon dioxide used was 40 (23) litre in the conventional pneumoperitoneum group and 8.6 (7.4) litre in the AWL group (P 0.001) (table 2). The total amount of fluids administered to both groups was not significantly different. The total amount of Ringer’s lactate solution used was
Abdominal wall lift for laparoscopy
571
Table 3 Postoperative characteristics in the study groups. Consumption number of doses per group. *P 0.05, **P 0.01 between groups Pneumoperitoneum group AWL group (n 13) (n 12) Consumption of oxycodone in the recovery room Consumption of oxycodone during 24 h Consumption of ketorolac during 24 h (30 mg dose⫺1) No. of patients with no pain in recovery room No. of patients with no pain during 24 h Duration of drowsiness (min) No. of patients needing droperidol for vomiting No. of patients with right shoulder pain during 24 h
25
22
28
16
21
9
5*
1
1
3
98 (46)**
13 (34)
6*
1
6*
1
1891 (822) ml in the conventional pneumoperitoneum group and 1754 (482) ml in the AWL group (ns). The values for hydroxyethyl starch were 579 (227) ml and 554 (121) ml, respectively (ns). Postoperative pain scores did not differ between the two groups during the 3-h recovery room period. Postoperative drowsiness (score 2) lasted 98 (46) min in the conventional pneumoperitoneum group and 13 (34) min in the AWL group (P 0.001) On the first postoperative day, six patients (46 %) in the conventional pneumoperitoneum group and one patient (8 %) in the AWL group complained of pain in the right shoulder (P 0.05). During the first 24 h, six patients in the conventional pneumoperitoneum group and one patient in the AWL group suffered from PONV which required treatment with droperidol (P 0.05). During the first 24 h, one patient in the conventional pneumoperitoneum group and three patients in the AWL group did not need any pain relief. In the conventional pneumoperitoneum group 21 doses of ketorolac and in the AWL group nine doses were given. The values for oxycodone were 28 and 16, respectively (ns) (table 3).
Discussion Our results demonstrated that the abdominal wall lift method using minimal carbon dioxide insufflation for laparoscopic cholecystectomy was associated with fewer peroperative pulmonary events and a reduction in haemodynamic changes. It also appeared to provide a faster and more uneventful postoperative recovery compared with conventional pneumoperitoneum. Pulmonary compliance was significantly greater using the abdominal wall lift method than with conventional carbon dioxide insufflation. The decrease in pulmonary compliance caused by conventional carbon dioxide pneumoperitoneum was
similar to that reported by Bardoczky and co-workers [4]. Abdominal distension is known to elevate the diaphragm and abdominal part of the chest wall, restricting lung expansion. This leads to increased airway pressures associated with decreased pulmonary compliance. To maintain minute ventilation constant, increased peak and plateau airway pressures are needed with possible haemodynamic impairment, especially in obese patients [4]. Carbon dioxide is absorbed rapidly into the circulation through the peritoneum, resulting in respiratory acidosis. Because of the carbon dioxide load, increased ventilatory drive persists during the recovery phase. By avoiding excessive carbon dioxide with the abdominal wall lift method, less ventilatory work is required during and after the procedure. Carbon dioxide produces direct and indirect haemodynamic effects, causing peripheral vasodilatation and depressing myocardial contractility. Carbon dioxide activates the central nervous system and evokes sympathoadrenal responses, increasing myocardial contractility and causing tachycardia and hypertension. During mechanical ventilation, venous return is impaired resulting in increased peripheral vascular resistance and reduced cardiac output [13]. Carbon dioxide insufflation has been reported to have caused serious gas emboli which may lead to life threatening cardiac arrhythmias [14]. The risk of gas embolism is lower with the abdominal wall lift method as the amount of carbon dioxide used is significantly less. We have demonstrated that increases in arterial pressures are more marked with conventional pneumoperitoneum; this may lead to increased myocardial work. High IAP results in an increase in cardiac afterload and elevated systemic vascular resistance [5], which are also known to be risk factors in patients with myocardial ischaemia causing an increase in myocardial oxygen consumption. High preload also diminishes coronary flow by decreasing coronary artery perfusion pressure. Cunningham and co-workers [15] found that carbon dioxide insufflation increased left ventricular end-systolic wall stress, and left ventricular end-diastolic area decreased after head-up tilt while left ventricular ejection fraction was unaffected. These changes in left ventricular performance may be especially deleterious in patients with compromised cardiac function. The abdominal wall lift method, enabling minimal carbon dioxide insufflation and lower IAP, may confer some benefit to patients with pre-existing myocardial disease. In our conventional pneumoperitoneum group, CVP increased, as has been demonstrated previously by Odeberg and colleagues [16]. The increase in CVP and its slow return to preanaesthetic values may be the result of increased IAP, forcing blood from the abdominal organs into the central venous reservoir; this blood then slowly returns to the splanchnic region [17]. Also, elevated vasopressin concentrations seen in an earlier study [18] can cause elevation in CVP. In our study CVP remained at a significantly lower level with the abdominal wall lift method compared with conventional pneumoperitoneum.
572 Increased IAP related to carbon dioxide pneumoperitoneum with head-up tilt decreases venous return from the lower extremities and increases FVP [19], thereby increasing the risk of deep venous thrombosis [6] or pulmonary embolism [19]. For these reasons every effort should be made to reduce venous stasis by the use of antiembolic stockings and low-molecular-weight heparin. Patients with a history of thromboembolic disease are at increased risk of developing thromboembolic complications. It is interesting that FVP remained elevated during the whole 3-h recovery period in the conventional pneumoperitoneum group. When the abdominal wall lift method was used, FVP remained at baseline levels during operation and recovery. The incidence of right shoulder pain in the conventional group was similar to that reported by Scheinin and colleagues [7]. In the AWL group, right shoulder pain was virtually absent. It has been suggested that insufflated carbon dioxide, diaphragmatic distention, or both, may be the cause of irritation at the phrenic nerve distribution area. Fredman and colleagues [20] noted the removal of the remaining exogenous carbon dioxide at the end of operation reduced the incidence and severity of referred shoulder pain. The use of the abdominal wall lift method with a smaller amount of insufflated carbon dioxide may have protected the patients against right shoulder pain. A reduction in PONV was observed in the AWL group. This may confer some benefits in patients undergoing this procedure on a day-case basis.
British Journal of Anaesthesia
4. 5. 6.
7.
8. 9.
10.
11. 12. 13. 14. 15.
16.
Acknowledgements The authors are indebted to Professor Markku Nurminen, PhD, for statistical advice. 17.
References 1. Joris J, Cigarini I, Legrand M, Jacquet N, De Groote D, Franchimont P, Lamy M. Metabolic and respiratory changes after cholecystectomy performed via laparotomy or laparoscopy. British Journal of Anaesthesia 1992; 69: 341–345. 2. Berggren U, Gordh T, Grama D, Haglund U, Rastad J, Arvidsson D. Laparoscopic versus open cholecystectomy: hospitalization, sick leave, analgesia and trauma responses. British Journal of Surgery 1994; 81: 1362–1365. 3. Baraka A, Jabbour S, Hammoud R, Aouad M, Najjar F, Khoury G, Sibai A. End-tidal carbon dioxide tension during
18. 19. 20.
laparoscopic cholecystectomy. Anaesthesia 1994; 49: 304–306. Bardoczky GI, Engelman E, Levarlet M, Simon P. Ventilatory effects of pneumoperitoneum monitored with continuous spirometry. Anaesthesia 1993; 48: 309–311. Noirot D, Joris J, Legrand M, Lamy M. Hemodynamic changes during pneumoperitoneum for laparoscopic cholecystectomy. Anesthesiology 1992; 77: A69. Beebe D, McNevin M, Belani K, Letourneau J, Crain M, Goodale R. Evidence of venous stasis after abdominal insufflation for laparoscopic cholecystectomy. Anesthesiology 1992; 77: A148. Scheinin B, Kellokumpu I, Lindgren L, Haglund C, Rosenberg PH. Effect of intraperitoneal bupivacaine on pain after laparoscopic cholecystectomy. Acta Anaesthesiologica Scandinavica 1995; 39: 195–198. Banting S, Shimi S, Van der Velpen G, Cushieri A. Abdominal wall lift. Surgical Endoscopy 1993; 7: 57–59. Rademaker B, Meyer D, Bannenberg J, Kalkman C. Laparoscopy using abdominal wall retraction versus pneumoperitoneum: effects on hemodynamics and gas exchange. Anesthesiology 1994; 81: A763. McSherry C, Ferstenberg H, Calhoun F, Lahman E, Virshup M. The natural history of diagnosed gallstone disease in symptomatic and asymptomatic patients. Annals of Surgery 1985; 202: 59–63. Meriläinen P, Hänninen H, Tuomaala L. A novel sensor for routine continuous spirometry of intubated patients. Journal of Clinical Monitoring 1993; 9: 374–380. Miettinen O. Comment. Journal of the American Statistical Association 1974; 69: 380–382. Cullen D, Eger E. Cardiovascular effects of carbon dioxide in man. Anesthesiology 1974; 41: 345–349. Shanta T, Harden J. Laparoscopic cholecystectomy: anesthesia-related complications and guidelines. Surgical Laparoscopy and Endoscopy 1991; 1: 173–178. Cunningham A, Turner J, Rosenbaum S, Rafferty T. Transoesophageal echocardiographic assessment of haemodynamic function during laparoscopic cholecystectomy. British Journal of Anaesthesia 1993; 70: 621–625. Odeberg S, Ljungqvist O, Svenberg T, Gannedahl P, Bäckdahl M, von Rosen A, Sollevi A. Haemodynamic effects of pneumoperitoneum and the influence of posture during anaesthesia for laparoscopic surgery. Acta Anaesthesiologica Scandinavica 1994; 38: 276–283. Kelman G, Swapp G, Smith I, Benzie R, Gordon N. Cardiac output and arterial blood-gas tensions during laparoscopy. British Journal of Anaesthesia 1972; 44: 1155–1162. Joris J, Lamy M. Neuroendocrine changes during pneumoperitoneum for laparoscopic cholecystectomy. British Journal of Anaesthesia 1993; 70: A.33. Jorgensen J, Gillies R, Lalak N, Hunt D. Lower limb venous hemodynamics during laparoscopy: an animal study. Surgical Laparoscopy and Endoscopy 1994; 4: 32–35. Fredman B, Jedeikin R, Olsfanger D, Flor P, Gruzman A. Residual pneumoperitoneum: a cause of postoperative pain after laparoscopic cholecystectomy. Anesthesia and Analgesia 1994; 79: 152–154.