he assessment of adequate levels of anaesthesia traditionally relies not only on a patient's movement but also on the hemodynamic response (or both) to a surgical stimulus

Currently a derivative of MAC namely, end tidal partial pressure (FET) displayed on the work station as concentration , maybe an alternative useful measure of the anaesthetic effect of an inhaled anaesthetic agent

. Many pharmacological factors have been associated with alterations in MAC and Mac derivatives such as nonsteroidal anti-inflammatory drugs (NSAIDs), analgesics, and anesthetics.

However, few studies have focused on physiological factors, such as hypercarbia or hypocarbia. A correlation has been found between Paco2 and Etco2 in ventilated patients with healthy lungs. Some authors have suggested that Etco2 could be considered appropriate for estimating Paco2 even in critical patients. Knowledge of the effects of Paco2 on end tidal concentration of sevoflurane among patients undergoing laparoscopic cholecystectomy may help anaesthesiologists titrate sevoflurane carefully and precisely during different mechanical ventilation settings to avoid dose-dependent hypotension, impaired cardiac contractility, and hypothermia caused by excessive anaesthetic depth of sevoflurane.

Inclusion Criteria:

• American Society of anaesthesiologist ASA physical status I, II
• admitted for laparoscopic cholecystectomy

Exclusion Criteria:

• Refusal of patients.

  • Patients with renal or liver dysfunction.
  • Patients with chronic pain other than cholelithiasis.
  • Cardiac disorders as uncontrolled hypertension, arrhythmia, Ischaemic heart disease, valvular heart disease and pulmonary hypertension.
  • Patient with haematological disorder as Sickle cell disease.
  • Chest patient as asthma, COPD.
  • Combined surgery .
  • History of allergy to any of the study drugs.
  • Patients with communication problems, cognitive dysfunction, or psychological disorders.
  • Patients who received analgesics or sedatives 24 h before a scheduled surgery.
  • Alcohol or drug abuse.