[Are high risk patients candidates for minimally invasive surgery with CO2 pneumoperitoneum? Viewpoint from anesthesiology]. / Sind Risikopatienten zur minimal-invasiven Operation mit CO2-Pneumoperitoneum geeignet? Betrachtung aus anaesthesiologischer Sicht.

As laparoscopic techniques show definite advantages in terms of pain and postoperative pulmonary function, high-risk patients especially benefit from such procedures. Pathophysiological changes caused by the pneumoperitoneum can be managed with invasive monitoring and resulting therapy. The increase in systemic vascular resistance with reduction in cardiac output can be kept to a minimum using low intraabdominal pressures (8-10 mmHg) under adequate muscular relaxation. Additional peripheral vasodilators and positive inotropic medication may be necessary. As the adverse hemodynamic effects end almost instantaneously with the reduction of the intraabdominal pressure, it is allways possible to revert to an open procedure after a laparoscopic try. If ventilation can not be increased adequately to maintain isocapnia in a patient suffering from pulmonary disease, the resulting increase in paCO2 will usually be moderate. In some instances it may be necessary to prolong artificial ventilation postoperatively, until isocapnia is reached with minuteventilation as at the beginning of anaesthesia.

Intraperitoneal versus interpleural morphine or bupivacaine for pain after laparoscopic cholecystectomy.

BACKGROUND: Opioids can produce peripheral analgesic effects by activation of opioid receptors on sensory nerves. This study was designed (1) to examine a novel route of opioid administration, the intraperitoneal injection; (2) to compare this to interpleural application, and (3) to compare opioid with local anesthetic effects under both conditions. METHODS: At the end of laparoscopic cholecystectomy, 110 patients received the following injections in a double-blind, randomized manner: Group 1 (n = 18) was given intraperitoneal morphine (1 mg in 20 ml saline) and 20 ml intravenous saline. Group 2 (n = 17) received intraperitoneal saline and 1 mg intravenous morphine. Group 3 (n = 15) received 20 ml 0.25% intraperitoneal bupivacaine and intravenous saline. Group 4 (n = 20) received interpleural morphine (1.5 mg in 30 ml saline) and 30 ml intravenous saline. Group 5 (n = 20) received interpleural saline and 1.5 mg intravenous morphine. Group 6 (n = 20) received 30 ml 0.25% interpleural bupivacaine and intravenous saline. Postoperative pain was assessed using a visual analog scale, a numeric rating scale, and the McGill pain questionnaire. Pain localization, supplemental analgesic consumption, vital signs, and side effects were recorded for 24 h. RESULTS: Neither intraperitoneal nor interpleural morphine produced significant analgesia after laparoscopic cholecystectomy (P > 0.05, Kruskal-Wallis test), whereas interpleural bupivacaine was effective (P < 0.05, Kruskal-Wallis test, up to 6 h postoperatively) but not intraperitoneal bupivacaine (P > 0.05, Kruskal-Wallis test). Shoulder pain was not prevalent in the majority of patients during the first 6 h. By 24 h, about half of the patients complained of shoulder pain, which was rated "low" by about one-third of all patients. No significant side effects occurred. CONCLUSIONS: Interpleural bupivacaine (0.25%) produces analgesia after laparoscopic cholecystectomy. We attribute the lack of effect of intraperitoneal injections to the small dose and to a rapid dilution within the peritoneal cavity. The fact that interpleural morphine (0.005%) is ineffective may be due to an intact perineurial barrier in the noninflamed pleural cavity, which restricts the transperineurial passage of morphine to opioid receptors on intercostal nerves.

[CO2 stores in laparoscopic cholecystectomy with CO2 pneumoperitoneum]. / Zur Frage der CO2-Speicherung bei laparoskopischer Cholezystektomie mit CO2-Pneumoperitoneum.

METHODS: Two groups of 22 patients each were studied in a prospective, randomised fashion during laparoscopic cholecystectomy (LCh) and CO2 pneumoperitoneum (PP) with regard to end-tidal and arterial PCO2 and pulmonary elimination of CO2 (ECO2, Servoventilator with integrated CO2-analyser 930, Siemens). In group 1 minute ventilation was kept constant, resulting in moderate hypercapnia during PP. paCO2 increased by about 10 mmHg during up to 50 min PP. In group 2 paCO2 was kept constant by a stepwise increase in minute ventilation (Fig. 1, Table 2). RESULTS: Compared to values just before PP, ECO2 increased in group 1 rather rapidly up to 20 min of PP and more slowly thereafter, reaching a mean value 35% above control at 45 min PP. In group 2 ECO2 was significantly higher than in group 1 between 15 and 35 min PP. At 45 min PP, however, ECO2 was identical in both observation groups (Fig. 2). CONCLUSIONS: Assuming a stable metabolic CO2 production rate during the observation period and no differences in CO2 absorption from the PP between the two study groups, differences in ECO2 between groups would be a measure of CO2 stored in group 1 patients during the increase in paCO2 with PP (Fig. 3, Table 3). CO2 storage rapidly increased between 0 and 15 min PP, more or less reached a plateau between 15 and 35 min PP, and ceased at 45 min PP. Storing capacity for CO2 during the first 45 min PP amounted to a mean value of 1.20 ml CO2/kg body weight and mmHg paCO2, which agrees favourably with data from the literature and a computer model from Fahri and Rahn published in 1960 (Fig. 4, Table 4). If during LCh with CO2-PP patients are ventilated with a constant minute ventilation, a moderate increase in paCO2 of about 10 mm Hg can be expected. In this case, during the first 45 min PP a 70-kg patient will retain about 1000 ml CO2 in blood and tissues, which must be eliminated after cessation of PP. If the paCO2 is to be held constant during PP, minute ventilation has to be progressively increased by about 40%.

[Pulmonary CO2 elimination in laparoscopic cholecystectomy. A clinical study]. / Pulmonale CO2-Elimination bei laparoskopischer Cholezystektomie. Eine klinische Untersuchung.

METHODS: We measured pulmonary elimination of carbon dioxide (VCO2), end-tidal and arterial CO2 tensions (PETCO2, PaCO2), deadspace ventilation (VD/VT), and arterial oxygen tension (PaO2) using a Siemens 930 CO2 analyzer incorporated into a servoventilator and arterial blood gas analyses, respectively, in 31 patients undergoing laparoscopic cholecystectomy with a median duration of pneumoperitoneum (PP) of 60 min. RESULTS: During the first 30 min of PP VCO2 increased significantly by a mean of 30% (Fig. 1). At the same time, with constant minute ventilation PETCO2 und PaCO2 increased by about 8 mm Hg each (Fig. 3, Table 1). In a subgroup of 10 patients who could be observed for up to 75 min of PP, we found a stepwise increase in minute ventilation with no further increase in PETCO2 and PaCO2 after 30 min PP, but a slowly rising VCO2 (Fig. 2). Arterial-to-end-tidal CO2 tension difference (Pa-PETCO2) remained constant at about 4 mm Hg with institution and during the course of PP (Fig. 4), as did VD/VT at a median value of 0.38-0.40 (Fig. 5). PaO2 (FIO2 = 0.5) did not change significantly with PP (Table 1). With desufflation we found a short-term increase in VCO2 (Table 2). CONCLUSIONS: During PP, CO2 is reabsorbed from the peritoneal cavity. During the initial unstable phase with rising PaCO2, reabsorption of CO2 is the sum of increased pulmonary elimination of CO2 above baseline and uptake of CO2 into gas stores of the body. We estimated CO2 reabsorption to be on the order of 70 ml/min during the first 30 min of PP. During the later, stable phase, reabsorption of CO2 equals increased pulmonary elimination of CO2 above baseline and was estimated to be in the order of 90 ml/min in 10 patients with 30-75 min of PP (hatched area in Fig. 2). PET-CO2 corresponded well with PaCO2 in these patients. VD/VT and arterial oxygenation did not change significantly with institution or during the course of PP. Monitoring VCO2 probably is a useful aid in the early detection of CO2 emphysema (Fig. 6).