الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 107 |  |  |
| | | from | 107 | | |
Abstract
This randomized controlled trial included 90 patients who completed the study, 30 patients in each group.
The study compared the effect of metoclopramide versus granisetron as prokinetic drugs on the gastric volume guided by ultrasound measurement of the gastric antrum dimensions. The results showed that metoclopramide has more prokinetic effect than granisetron as it appeared in gastric CSA post treatment measurements and gastric volume measurements. The results showed high statistically significant difference between the baseline (pre treatment) mean CSA dimension and post-treatment dimension; (5.1 ±2.1 vs. 3.7 ± 1.5) in metoclopramide group, and in granisetron group results were (6±1.7 vs. 5±1.6) , while no statistical significance was found between the baseline and post-treatment gastric dimensions in control group (5.9±2.5 vs. 5.7±2.4; P value 0.9).
Granisetron selectively block serotonin 5-HT 3 receptors, with little or no effect on dopamine receptors. 5-HT 3 receptors, which are located peripherally (abdominal vagal afferents) and centrally (chemoreceptor trigger zone of the area postrema and the nucleus tractus solitarius), appear to play an important role in the initiation of the vomiting reflex. The 5-HT 3 receptors of the chemoreceptor trigger zone in the area postrema reside outside the blood–brain barrier. The trigger zone is activated by substances such as anesthetics and opioids and signals the nucleus tractus solitarius, resulting in PONV. Emetogenic stimuli from the GI tract similarly stimulate the development of PONV [101].
Metoclopramide acts peripherally as a cholinomimetic (ie, facilitates acetylcholine transmission at selective muscarinic receptors) and centrally as a dopamine receptor antagonist[102].
Its action as a prokinetic agent in the upper gastrointestinal (GI) tract is not dependent on vagal innervation but is abolished by anticholinergic agents. It does not stimulate secretions [103].
Perioperative pulmonary aspiration of gastric content can lead to prolonged tracheal intubation, hospitalisation, aspiration pneumonitis and pneumonia [9].
As usual, fasting time is often used for estimation of the risk of aspiration, not accounting for comorbidities that affect gastric emptying, such as pregnancy and labour. Bedside point-of-care ultrasound (POCUS) of gastric content is used by the anaesthetist to assess the qualitative and quantitative content of the stomach[104].
This technique has been used and validated in pregnant women to define the cut-off values for the risk of aspiration [105].
The first studies examining the gastric content of the stomach were initiated in the late 1980s and further studied in pregnant patients in the 1990s. Studies have shown that ultrasonographers have correctly identified content 87.5% of the time when blindly evaluating pregnant patients [105].
The success of these diagnoses was related to how far into the pregnancy the patient was, with decreasing rates later in pregnancy, attributable to the increased difficulty of the larger gravid uterus. Before the third trimester, nearly 100% were successful, whereas results were closer to 88% when the patient was >36 weeks’ gestation [106].
In 2018, Roukhomovsky and colleagues studied the Perlas score in the pregnant patient and revealed that the grade designations also correlated well in pregnancy. Numerous studies since the late 1980s have evaluated the volume of the fluid content in the gastric antrum. These studies were based on non-obese, non-pregnant adults, and thus further research was necessary to validate a model for the pregnant population Ultrasound assessment of the stomach has been validated in the perioperative period. It may be a useful tool to assess risk of aspiration when there is uncertainty about the duration of fasting or when encountering comorbidities that may prolong gastric emptying beyond recommended guidelines[107].
Although it is possible to proceed with a plan for anaesthesia that assumes aspiration risk, such as inducing anaesthesia with a rapid-sequence technique or awake intubation,but these plans have their own risks. Being able to assess the patient’s aspiration risk may affect the anaesthetic plan in the pregnant or non-pregnant patient. When procedures cannot be performed with neuraxial blockade, the decision between general anaesthesia with tracheal intubation and conscious sedation could be guided by this information [108]. Pregnancy can predispose to aspiration because of increased intra-abdominal pressure from the gravid uterus, and from gastroparesis during labour and the progesterone induced relaxation of the lower oesophageal sphincter. Gastric ultrasound is a noninvasive tool that can be used to determine the nature and volume of the gastric content, and whether the volume presents a high or low risk for aspiration, thereby informing the anaesthetic plan for the pregnant patient [109]. Performing a gastric ultrasound on the parturient poses technical challenges. The gravid uterus displaces visceral organs cephalad and to the right, which makes antral identification more difficult. Tachypnoea of pregnancy and hyperdynamic circulatory changes might make obtaining adequate sonographic windows more challenging. Finally, the position and placement of the transducer can be more testing because of the limited space between the xiphisternum and the gravid abdomen[110]. Despite these challenges, consistency has been shown with gastric ultrasound assessment in third trimester parturients with good feasibility and reproducibility for the detection of gastric contents. The antrum remains at a similar depth, or may be found deeper than that of the non-pregnant patient. Gastric sonography may be aided in pregnant patients by sitting in a semirecumbent position, manually displacing the uterus, and asking the patient to hold their breath in end expiration for optimal sonographic windows. Based on ultrasonographic measurement metoclopramide has more prokinetic effect than granisetron. However, granisetron show that it has less postoperative nausea and vomiting in comparison with metoclopramide (one case undergoes PONV with granisetron, 4 cases undergoes PONV with Metoclopramide while 8 cases with normal saline).
That makes us need more research to establish gastric ultrasound as a bed side tool in perioperative evaluation including evaluation of the perioperative drugs used as a prokinetics or antiemetics.