Effects of Dextrose Versus Saline Infusion on Intrathecal Morphine-Induced Postoperative Nausea and Vomiting During Gynecological Abdominal Surgeries: Randomized Controlled Double-blind Study

The use of intrathecal opioids for postoperative analgesia was introduced in 1979. There have been many pharmacodynamic and pharmacokinetic studies of intrathecal opioids and the mechanism of action-producing analgesic effects by direct action at the spinal cord level. The addition of intrathecal opioids to bupivacaine for spinal anesthesia may provide clinical advantages such as improved intraoperative conditions and postoperative analgesia. Adverse effects range from nausea and vomiting that, although not life-threatening, are major nuisances to the patient, to more severe effects, including sedation and life-threatening respiratory depression.

Nausea is an unpleasant sensation causing discomfort in the stomach area which gives the feeling of the impending need to vomit or retch. It is often a transient sensation which is frequently followed by active retching or tachycardia and increased salivation. Vomiting is the involuntary, forceful expulsion of the contents of the stomach through the mouth and/or nose. The incidence of these side effects varies from 30-80 % after elective surgery depending on the type of anesthesia and surgery as well as predisposing patient risk factors.

Postoperative nausea and vomiting (PONV) describes nausea and/or vomiting or retching occurring in the post-anesthesia care unit (PACU) or during the first 24-48 hours after surgery. Post-discharge nausea and vomiting (PDNV) refers to symptoms that occur after discharge from the hospital or surgical care facility. Not only is PONV a distressing complication from the patient's perspective but also it can result in dehydration, electrolyte imbalance, acid base imbalance, pulmonary aspiration, pneumothorax, hypoxia, esophageal rupture, increased intracranial pressure, suture rupture, wound dehiscence, bleeding, delay in the ability to resume oral intake, prolonged PACU and/or hospital stay, fatigue, anxiety, unanticipated hospital admission or readmission, and increased medical costs. The distressing symptoms of PONV/PDNV also contribute to patient dissatisfaction with their surgical experience. PONV prophylaxis is economically beneficial for the hospital when a rational multimodal program is implemented based on patient and procedural risk factors.

Enhanced recovery programs in surgical patients and the promotion of day case surgery both require and include adequate prophylaxis of PONV. There are dozens of different anti-emetic drugs, mostly within the drug classes of 5- hydroxytryptamine-3 (5HT3), dopamine-2 (D2) and neurokinin-1 (NK1) receptor antagonists, corticosteroids, antihistamines and anticholinergics. Varying adverse effects have been attributed to the six different substance classes, such as headache and constipation (5-HT3 receptor antagonists); extrapyramidal symptoms, sedation, arrhythmia and QT prolongation (D2 receptor antagonists); hyperglycemia, immunosuppression and poor wound healing (corticosteroids); drowsiness, dry mouth and urinary difficulties (antihistamines); and dry mouth and visual disturbances (anticholinergics).

In addition to pharmacological therapy, recent studies are assessing the impact of fluid therapy in the prevention of PONV, finding that the use of crystalloids in ASA I and II patients receiving general anesthesia reduces the risk of postoperative nausea. and a preventive effect of vomiting during the first 24 hrs post-surgery[15]. Another fluid therapy strategy for PONV is the administration of colloids, which has had a superior effect in preventing PONV than the administration of crystalloids in patients undergoing lower abdominal surgery who received general anesthesia for 3 hours or more[16]; however, these results are not the same in patients who received general anesthesia for less than 3 hours. On the other hand, the administration of bolus glucose solution is still very controversial, since some results show that it does not reduce PONV [17], while Chisaki et al. (2020) reported its usefulness in reducing postoperative nausea, but not vomiting.

These last fluid therapy recommendations should be handled with caution, since the risk of serious adverse events resulting from the supplementary administration of intravenous crystalloids and colloids is unknown, and it is not clear whether patients are at risk of being readmitted to the hospital postoperatively due to these interventional measures.