Informed and written consent will be taken from 98 parturients of American Society of Anaesthesiologists Physical status (ASA) class II undergoing elective lower segment caesarean section under spinal anaesthesia. Randomization of parturients will be done by shuffled sealed opaque envelope technique.

A thorough pre- anaesthetic evaluation will be done 24 hours prior to the procedure. Standard monitoring with electrocardiography (ECG), automated non-invasive blood pressure (NIBP) and pulse oximetry (saturation- SpO₂) will be done for baseline values and intraoperative monitoring using a multipara meter Philips IntelliVue MP20/MP30 monitor. 

Parturients will be divided into two groups:-

GROUP K:- Those who will receive 15 mg of intravenous Ketamine in 3 ml of normal saline. 

GROUP C:- Those who will receive 3 ml of normal saline.

This will be a double-blind study. The study drugs will be prepared by the same anaesthesiologist who does the randomization and administered by the observer. Hence, the observer and parturient will be blinded to the study drugs. The baseline hemodynamic values will be recorded in the supine position (with wedge under the right buttock to prevent aortocaval obstruction). 

Intravenous (IV) access will be established in the upper limb. Each parturient will be started on IV infusion of Ringer lactate at 5- 7 ml/kg prior to the subarachnoid block (SAB) in the operating room. The baseline values of SBP (systolic blood pressure), DBP (diastolic blood pressure), MAP (mean arterial pressure), HR (heart rate), ECG and saturation will be recorded. The parturients will then be turned to lateral position. The study drugs will be administered by the observer immediately before the injection of the spinal agent. Spinal anaesthesia will be performed using Quincke’s 25 gauge spinal needle in lateral position with 10 mg of injection bupivacaine 0.5% (hyperbaric) at the L3–L4 interspace with midline approach. The parturient will return to the supine position immediately with a wedge under the right buttock to prevent aortocaval obstruction. Oxygen will be supplemented through face mask at 4L/min. Ringer lactate will be administered at a rate of 100 ml/10 min. The onset and level of sensory block will be checked 5 minutes after the spinal injection and the surgery will be allowed to start after the confirmation of sensory block to T6 level. Maximum level of sensory and motor blockade will be recoded. If a T6 sensory block level is not achieved, these parturients will be excluded from the study and managed according to the institutional protocol. NIBP, HR, respiratory rate (RR) and SpO₂ will be recorded at 2 minutes intervals after the SAB up to 20 minutes and then at 5 minutes intervals till the end of surgery. Hypotension defined as a decrease in SBP <20% of baseline or <90mmHg will be recorded and treated with IV bolus of 6mg injection ephedrine. The number of incidences of hypotension, total amount of ephedrine required and number of doses of ephedrine required will be recorded. The first 60 minutes following spinal anaesthesia will be considered for anaesthesia-induced hypotension. Following extraction of the baby, APGAR score will be recorded at 1 and 5 minutes. Injection oxytocin 10 units will be given as uterotonic following baby extraction intramuscularly. Parturients requiring any additional oxytocin and/or additional surgical interventions will be excluded from the study.

 Postoperative monitoring of SBP, DBP, MAP, HR, ECG and SPO2 will be done every hourly for first 6 hours. Post-operative pain will be assessed using the visual analogue scale (VAS). VAS consists of a 10 cm line with 0 equaling “no pain at all” and 10 being the “worst possible pain” ¹¹. The pain will be monitored every 2 hours for first 6 hours and then every 6^th hourly for next 18 hours or until first complaint of pain called the “time to first breakthrough pain” which will be considered as the pain requiring treatment (VAS>/= 4 ). Rescue analgesic injection diclofenac 75mg will be given intramuscularly. The number of doses given will be recorded. Ramsay sedation scale will be used to evaluate the sedative effect at baseline, then at 5, 10, 15, 30, 45 minutes after intrathecal injection and then at the end of the operation ¹.