Shoulder pain is a well-recognized complaint following laparoscopic surgery. It is underlying mechanism has various causes, therefore, modalities in management and prevention of this sort of pain are numerous with different success rates. In the light of this, the investigators aim to compare an anesthetic management plan involving using ketamine (which is a known intraoperative anesthetic agent) to another not involving it for participants undergoing gastric sleeve, and compare the incidence and intensity of shoulder pain afterwards.

Obesity is a worldwide problem impairing health and quality of life, therefore , gastric sleeve surgery is considered an efficacious way in managing high body mass index with an excellent outcomes. Patients typically suffer pain following surgery along the incision port sites and in the abdominal cavity, but a significant subset of patients experience shoulder pain, typically in the left shoulder, which is often under-recognized and poorly managed and can be more worrisome to the patient. Shoulder pain following laparoscopy was first noticed by gynecologist in 1976. it is very common as it has an incidence in the range of 34.1%-82.4% . with varying rates among different types of surgery as:57.1%-65.5% after laparoscopic appendectomy, 66% following laparoscopic gastrectomy and 80% after gynecological laparoscopy. The nature of pain is mainly mild to moderate that appears as dull pain lasting 2-3 days but can remain a long time as 5 weeks postoperatively.

The mechanism of post laparoscopic shoulder pain(PLSP) is not fully understood but the most accepted explanation is referred pain via the phrenic nerve, which shares nerve roots with the C3-C5 cervical nerves that innervate the shoulder area The pneumoperitoneum created during laparoscopy causes diaphragmatic irritation, leading to phrenic nerve stimulation and referred pain. Moreover, there were other factors implemented such as malposition intraoperatively, inappropriate shoulder abduction, and early postoperative activity. In addition, the effect of Co2 by itself.

Several management strategies were introduced to combat this phenomena such as: evacuating residual gas(Co2) as active gas aspiration, inserting a drain and pouring saline interperitoneally at end o surgery showed decrement in shoulder pain intensity and frequency. Pulmonary recruitment maneuvers by transiently applying higher positive pressure to the airways and alveoli. Lastly, low pressure pneumoperitoneum which implies 7-10mmgh pressure application reduced the severity and incidence of PLSP.

The hypothesis is that intraoperative ketamine infusion (as part of well-known anesthetic management) will lead to a reduction in the incidence and severity of PLSP. It is known that ketamine is a well-established anesthetic drug for over half a century in clinical practice. In certain doses which is called sub anesthetic doses, ketamine acts as a pain medication. It has the ability to alleviate both acute and chronic pain by just one injection in analgesic dose. A consensus guidelines done in 2018, in managing acute pain by intravenous ketamine resulted that subanesthetic dose have to be considered adjunct in operations which postoperative expected to be withering. The primary aim of the study is to examine the effect of including ketamine in the anesthetic management intraoperatively on the incidence and severity of PLSP compared to standard anesthesia and surgery techniques without it, in addition, outcomes such as duration of recovery, overall hospital stay, post-op analgesic requirements, side effects of ketamine and postoperative nausea and vomiting incidence.

Inclusion Criteria:

• patients aged 18-60
• American society of anesthesiologist grade 1,2
• BMI > 40
• BMI > 35 with obesity-related comorbidities

Exclusion Criteria:

• mentally incapacitated
• patients received any type of analgesia 24hr preoperatively except paracetamol
• history of drug abuse
• patients with low ejection fraction