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.