The incidence of postoperative pain is highly prevalent among surgical patients. Inadequate postoperative pain control can slow the recovery and it increases the risk of postoperative complications, namely lung collapse and chronic pain. Although morphine is the one of the gold standard analgesia option for postoperative pain, it comes with many unwanted adverse effects, such as severe nausea and vomiting, low blood pressure and dizziness. Thus, multimodal analgesia regime, including local anaesthetic (lignocaine) is strongly advocated for postoperative analgesia.

The normal route of lignocaine is injected into vein for the properties of analgesia and anti-inflammatory. It exerts its effect via the systemic absorption of drugs to block the central neuronal pain transmission. In recent years, studies have demonstrated that instillation of lignocaine inside abdominal cavity can reduce internal organ pain by blocking free nerve ending inside abdomen with minimal systemic absorption of drug and lower complications of systemic toxicity of local anaesthesia as compared to the intravenous route of lignocaine.

Several RCTs showed the beneficial effect of intraperitoneal lignocaine for the reduction of postoperative visceral pain after laparoscopic surgery. However, gynaecological open surgery (cystectomy, hysterectomy) involves greater degree of manipulation and trauma on the internal organs with greater visceral pain, resulting in longer duration of hospitalisation and delayed functional mobility recovery. It is believed that the intraperitoneal lignocaine reduces inflammatory response after surgery and exert analgesia effect by blocking the neural signal transmission at site of tissue injury. Therefore, it is important to conduct this study to examine the analgesic effect of intraperitoneal lignocaine in women undergoing gynaecological open surgery.

Postoperative pain impedes the progress of recovery and increases the risk of postoperative complications, namely lung atelectasis, incidence of desaturation, pulmonary dysfunction and chronic pain. Although opioid is the one of the gold standard analgesia for postoperative pain, it comes with many unwanted adverse effects, such as respiratory depression, hypotension and incidence of nausea and vomiting. Thus, multimodal analgesia regime, including local anaesthetic is strongly advocated for postoperative analgesia.

Lignocaine is a local anaesthetic agent, which has the properties of analgesia, anti-inflammatory and anti-arrhythmia effect via the blockade of sodium channel receptor in the spinal cord and dorsal root ganglia. The intravenous lignocaine exerts its effect via the systemic absorption of drugs to block the central neuronal transmission. In recent years, studies have demonstrated that intraperitoneal route of lignocaine can reduce visceral pain by inhibiting peritoneal free nerve ending and reduce peripheral neuronal hyper-excitatory of pain signal transmission. It is also believed that intraperitoneal lignocaine is associated with minimal systemic absorption of drug and lower incidence of systemic toxicity local anaesthesia as compared to the intravenous route of lignocaine.

Several randomised controlled trials (RCTs) showed the beneficial effect of intraperitoneal lignocaine for the reduction of postoperative visceral pain after laparoscopic surgery. However, gynaecological open surgery has greater degree of organ manipulation and tissue injury with greater visceral pain, resulting in longer duration of hospitalisation and delayed functional mobility recovery. It is believed that the intraperitoneal lignocaine reduces inflammatory response after surgery and exert analgesia effect by blocking the neural pain signal transmission at site of tissue injury. The dosage of intraperitoneal lignocaine used in the literature ranged from 200-400mg. The serum concentration of intraperitoneal lignocaine was measured, which was associated with a relatively safe serum concentration of lignocaine. Pharmacological studies have showed that the adjuvant dose of adrenaline reduced the systematic absorption of intraperitoneal lignocaine. Therefore, this study is designed to examine the analgesic effect of intraperitoneal lignocaine in gynaecological open surgery. The investigators hypothesised that intraperitoneal lignocaine reduces postoperative pain score at rest and movement in women undergoing gynaecological open surgery.

Inclusion Criteria:

• all adult women (American Society of Anesthesiologists (ASA) who >18 years old and <60 years old
• gynaecological open surgery with midline or transverse laparotomy incision (below or above umbilicus)

Exclusion Criteria:

• laparoscopic surgery
• allergic to lignocaine
• history of cardiac, vascular or liver disease
• ASA 3-5 or
• body mass index <18/ or >40