Laparoscopy – capnography gas 0095


Prolonged intra-abdominal insufflation with CO 2 in anesthetized and mechanically ventilated patients during upper abdominal laparoscopic surgery does not significantly affect the reliability of PETCO 2 monitoring in predicting PaCO 2 in healthy ASA I and II subjects and elderly patients.1-3 However, in ASA III and IV patients, PETCO 2 may not reflect changes in PaCO 2 during insufflation due to changes in alveolar dead space consequent to reduced cardiac output, increased ventilation-perfusion mismatching, or both.4,5 Therefore, direct arterial PaCO 2 monitoring is recommended in patients with significant cardiorespiratory diseases. electricity diagram flow An arterial line is reasonable to monitor PaCO 2 in ASA III and IV patients for three reasons: (1) end-tidal PCO 2 is not a reliable index of PaCO 2, (2) the normal gradient of 3 to 5 mm Hg between PaCO 2 and PETCO 2 is increased, and (3) even with normal PETCO 2, achieved by increasing minute volume, PaCO 2 may be as high as 50 mm Hg resulting in respiratory acidosis.

The Society of American Gastrointestinal Endoscopic surgeons (SAGES) published guidelines for laparoscopic surgery during pregnancy that include perioperative monitoring of arterial blood gases as well as perioperative fetal and uterine monitoring.6 This belief has been echoed by other authorities.7-9 Amos etal,7 documented four fetal deaths in seven pregnant women who underwent laparoscopic cholecystectomy or appendectomy (in these patients the ventilation was adjusted to maintain PETCO 2 in low-to mid-30’s). Although Amos et al, did not perform arterial blood gases, respiratory acidosis was stated as a possible factor contributing to fetal loss.10 Based on studies in pregnant ewes, 12,13 these concerns stem from previous studies indicating that elevation in maternal PaCO 2 could impair fetal CO 2 excretion across the placenta and could exacerbate fetal acidosis. la gas prices 2016 Other risk factors were present for fetal loss in this series, including perforated appendix and pancreatitis.7

The pregnant sheep model gives further credence to these concerns. Hunter et al9 and Cruz et al8 both observed that CO 2 pneumoperitoneum resulted in a PaCO 2-PETCO 2 gradient of 16 to 25 mm Hg. The resulting fetal hypercarbia correspondeds to to fetal hypertension, acidosis, and tachycardia. world j gastrointestinal oncol impact factor Hunter’s group also demonstrated that the PETCO 2 lagged behind the PaCO 2 by approximately 60 minutes, and hyperventilation was not able to prevent hypercarbia and acidosis. Because of the large changes in PaCO 2 levels, these two groups reported that capnography might underestimate and is therefore not a reliable indicator of respiratory acid-base status during CO 2 insufflation. youtube gas pedal They recommended arterial blood gas monitoring for all parturients undergoing laparoscopic surgery; however, Bhavani-Shankar and Mushlin10 challenged the appropriateness of the ewe model for this purpose. gas key staking Subsequently, Bhavani-Shankar et al11 prospectively evaluated the PaCO 2-PETCO 2 difference in eight parturients undergoing laparoscopic cholecystectomy with CO 2 pneumoperitoneum. The intra-abdominal pressures were maintained around 15 mm Hg. These women underwent surgery with general anesthesia during the second and third trimester of their pregnancies. electricity and magnetism review Adjusting minute ventilation to maintain PETCO 2 at 32 mm Hg, the arterial blood gases were measured at fixed surgical phases: preinsufflation, during insufflation, postinsufflation, and after completion of anesthesia. tropico 5 power plant The authors found no significant difference in either mean PaCO 2-PETCO 2 gradient or PaCO 2 and pH during the various phases of laparoscopy as shown below.

This is in contrast to results obtained by Cruz et al (9 pregnant ewes) and Hunter et al (4 pregnant ewes) where the difference increased by a mean of 10 mmHg during insufflation.12,13 Among the twenty-eight observations obtained in 8 patients during CO 2 insufflation in our study, the highest PaCO 2-PETCO 2 observed was 5.1 mmHg as against 16 and 25 mmHg observed by Cruez et al and Hunter et al in ewes.8.9 The results observed in our study are consistent with our earlier observations of derived PaCO 2-PETCO 2 of 6-7 mmHg from tcPCO 2 monitoring in laparoscopic surgery in a parturient.12 Therefore, the physiologic consequences of pneumoperitoneum are different in humans from those in pregnant ewes as seen by a lowered PaCO 2-PETCO 2 during insufflation in pregnant patients.

Although the sheep model is used for obstetric research, there could be physiological differences between the two species. For example, the preinsufflation PaCO 2-PETCO 2 in pregnant ewes range from 6 to 15 mmHg,8,9 whereas they are lower in pregnant humans (0.6 mmHg, range -2.5-5.1 mmHg; occasionally PETCO 2 exceeds PaCO 2).13-15 In our study, they varied from 0 to 5 mmHg. These values are similar to the values reported by the author in pregnant subjects undergoing cesarean section and in women during postpartum sterilization.13,14 The smaller pre-insufflation arterial to end-tidal PCO 2 difference in humans translates into a lower preinflation alveolar deadspace in pregnant patients than in pregnant ewes.15 A lower preinsufflation alveolar deadspace in pregnant patients probably results in a smaller subsequent changes in alveolar deadspace during CO 2 insufflation, and thus to a smaller PaCO 2-PETCO 2 in pregnant patients than in pregnant ewes.

Rosinoso-Barbero et al concluded that capnography proved to be an excellent guide to adjust ventilation during CO 2 insufflation in infants and children.18 However, Laffon et al concluded that PETCO 2 monitoring may overestimate PaCO 2 and consequently can result in hyperventilation during laparoscopic surgery.19 Arterial to end-tidal carbon dioxide differences were studied in sixty-one children undergoing pneumoperitoneum under general anesthesia.19 At a steady state, before pneumoperitoneum, the mean (a-ET)PCO 2 was -1.2 (SD)2.2, (confidence interval -5.6 to +3.4) Hg. At a steady state during CO 2 insufflation, the mean difference was -2.0(SD),(confidence interval -8.8 to +4.8) mm Hg although PaCO 2 and PETCO 2 increased by about 14% from baseline values. The incidence of negative gradients increased from 54% at pre-insufflation to 67% during CO 2 insufflation. The authors concluded that PETCO 2 often overestimates PaCO 2 during laparoscopy in children, by up to 8.8 mm Hg and therefore concluded that arterial blood gas analysis should be performed during long procedures to avoid hyperventilation. A limited data presented in a study by Bozkurt et al shows no changes in (a-ET)PCO 2 at 30 during CO 2 insufflation compared to baseline levels.20

Occasionally, during the course of laparoscopic surgery, the gradient may be negative in adults, in which case PETCO 2 overestimates PaCO 2.1 The incidence of negative gradients is higher in infants and children undergoing laparoscopic surgery.19 Low frequency, high tidal volume ventilation will open hitherto closed alveoli, whose CO 2 will now be seen as an increase in the slope of phase III of the capnogram and PETCO 2 will be close or exceed the PaCO 2 line. la gas Low FRC coupled with increased CO 2 delivery to the alveoli can exacerbate this response thereby increasing the frequency of occurrences of negative (a-ET)PCO 2 values during laparoscopic surgery.13-15