In the meta-analysis performed by Gao L et al, ten randomized clinical studies were reviewed to determine the effect of ondansetron in the prevention of hypotension after spinal anesthesia was initiated. The researchers used relative risk with a 95% confidence interval to analyze their outcomes. The meta-analysis suggests that spinal-induced hypotension, bradycardia, and amount of vasopressors needed were reduced with prophylactic ondansetron. However, Gao L et al recommends that further, stricter studies with larger sample size should be performed with a focus in obstetric patients.
A meta-analysis is considered a systematic review, which provides the highest level of evidence. The systematic review is relevant to the PICOT question in that helped determine that the administration of ondansetron can help decrease spinal-induced hypotension. The article had many strengths including the extensive method used to obtain the research studies, careful review of the quality of the clinical trials, and thorough statistical analysis to help determine significance of an outcome.
Some weaknesses include no definitive definition of hypotension. Also, outside variables were not taken into consideration such as different doses of ondansetron, fluid type and volume. Researchers limited the meta-analysis to only English published clinical studies. The randomized, double-blind, placebo-controlled trial by Khalifa OSM determines if the prophylactic administration of granisetron, ondansetron, and ephedrine in cesarean sections undergoing spinal anesthesia can help decrease hypotension and their effect on motor/sensory block.
Eighty parturients were randomly placed into four groups, with group 1 to receive normal saline 10 milliliters and groups 2, 3 and 4 to receive granisetron, ondansetron, and ephedrine, respectively. The medications were diluted in normal saline to total 10 milliliters and injected prior to spinal anesthesia. The trial showed that prophylactic administration of the three studied drugs decreased spinal-induced hypotension, nausea, and the amount of vasopressors needed. Granisetron was the only drug shown to improve recovery time of the sensory block.
This study provides strong evidence since the design was a double-blind, randomized control trial. Strengths include a thorough literature review, adequate sample size, and unbiased methodology in obtaining participants. Limitations include validity of the statistical tests used as they were not discussed in details as to why they were chosen and that only healthy parturients were included as opposed to emergent, complicated cases. Despite the limitations, this study helps to provide background research for future studies.
Marashi SM et al performed a randomized double-blind clinical trial comparing two doses of intravenous ondansetron with a placebo and how each reduces the effect of spinal-induced hypotension and shivering. The study consisted of 210 participants scheduled for procedures undergoing spinal anesthesia, randomly divided into three equal groups; group 1 received normal saline 20 milliliters and groups 2 and 3 received ondansetron 6 milligrams or 12 milligrams, respectively. Reliable statistical tests were used to analyze the results.
The study showed that administration of intravenous ondansetron significantly decreases spinal-induced hypotension, bradycardia, and shivering in comparison to normal saline; however, there was no significance in the difference of dosages. A double-blind, randomized control trial was used for the design indicating strong evidence to support the results. Strengths include a large sample size, high level of control, and unbiased recruitment of participants through computer generated code. Limitations include different surgical procedures, length of surgeries, blood loss and amount of fluid volume given during the procedure.
Although this study does not include parturients scheduled for cesarean section, it focuses on spinal-induced hypotension and how ondansetron can help attenuate this adverse effect. This information can be utilized in patients undergoing spinal anesthesia regardless of the procedure. The authors conducted a study to evaluate the effect of three different doses of intravenous ondansetron and placebo on the hemodynamic response and side effects following spinal anesthesia with bupivacaine and fentanyl for cesarean section.
The study included 128 ASA I pregnant women randomly allocated into four groups to receive 2, 4, or 8 milligrams intravenous ondansetron or placebo five minutes prior to induction. There were no differences in the number of patients with hypotension or other adverse effects in any of the four groups. There was a significant dose-dependent trend in ephedrine dosing with the dose of ondansetron. This prospective randomized, double-blind, placebo-controlled study presents a high level of evidence.
They studied the effects of multiple doses, recruited more participants than other related studies, individualized bupivacaine doses based on patient height, and defined hypotension. Detailed and consistent methodology and anesthetic technique were utilized. While each patient received 20 micrograms intrathecal fentanyl to improve the quality of anesthesia and prevent perioperative nausea, this may have altered a central mechanism of action of ondansetron. This study directly provides evidence for the PICOT question and is the only study that does not show a benefit of ondansetron with hypotension.
The authors conducted a study on the effects of intravenous ondansetron on reducing hypotension and bradycardia induced by spinal anesthesia. The study randomly allocated 71 patients into two equal groups. Group 1 received ondansetron 8 milligrams intravenously diluted in 10 milliliters normal saline, and group 2 received 10 milliliters normal saline five minutes prior to induction. Spinal anesthesia was consistent for each patient. Variables were recorded over 20 minutes and no surgical procedures were performed during that time. Group 1 had higher minimal systolic and mean blood pressure values than Group 2.
No significant differences in heart rate or diastolic blood pressure were observed. This randomized, double-blind, placebo-controlled study presents a high level of evidence. While the age range of patients was large, strong exclusion criteria were enforced. Standardized anesthesia management was utilized and controlled. Weaknesses include no definition for hypotension, a single dose of ondansetron, and small sample size. Each patient received 20 milligrams bupivacaine regardless of height, which may have led to over- or under-dosing of spinal anesthetic, affecting the extent of hypotension.
While this study observed the general surgical population, it supports the use of ondansetron and provides direct evidence for the PICOT question. The researchers also provided a thorough discussion of ondansetron and its possible central effect on hemodynamic changes useful for future background research. The clinical trial by Sahoo T et al was a randomized, double-blind, placebo-controlled study. It investigated if spinal-induced hypotension and bradycardia can be reduced with the administration of intravenous ondansetron.
Fifty-six patients were included in the study and randomly allocated into two equal groups. Group 1 received ondansetron 4 milligrams diluted in 10 milliliters of normal saline and group 2 received 10 milliliters of normal saline. Variables were recorded and results were analyzed using valid reliable statistical tests. Results of the study indicated that administration of ondansetron 4 milligrams prior to spinal anesthesia minimized a decrease in blood pressure. The study provides high level of evidence since it was a randomized, double-blind, placebo-controlled trial.
There were many strengths including extensive literature review, unbiased administration of medications via double-blinding, and adequate control of external factors such as volume of fluid administration, premedication, and spinal technique. Weaknesses include estimating the sample size, small sample size, and limiting the study to only 1 set dose of ondansetron. Although further study regarding this topic is warranted, the results of this study does apply to the PICOT question asked and helps to establish the practice of minimizing spinal-induced hypotension with prophylactic ondansetron.
Trabelsi W et al conducted a study with ASA I parturients by administering ondansetron 4 milligrams in 10 milliliters of normal saline or 10 milliliters of normal saline to decrease the incidence of hypotension. Hemodynamics were monitored, with results indicating that administration of ondansetron had a significant effect on hypotension (P <0. 05). This study was double-blinded and randomized, providing a strong level of evidence for clinical practice. A review of literature on the subject appeared thorough, noted in their discussion section. The two groups each had 40 participants.
Only 26 were needed based on a power analysis. Researchers used an arterial line, providing an accurate, continuous tool to measure blood pressure. However, there were weaknesses. This article did not have an abstract to summarize the study. They only tested one dose of ondansetron, as opposed to several articles in this area of study who looked at ranges. There was a discrepancy in their dose of ondansetron; in the discussion section they state five milligrams, while in the material and methods section, as well as the flowchart, four milligrams is noted.
The PICOT question is relevant because ondansetron was administered prior to spinal anesthesia with a decreased incidence of maternal hypotension, warranting use in the clinical setting. Wang M et al performed a double-blinded randomized study to determine the optimal dosage of ondansetron for preventing maternal hypotension during a cesarean delivery. Women were divided into five groups of 30 and given either 5 milliliters of normal saline, or ondansetron in 2, 4, 6, or 8 milligram doses five minutes prior to anesthesia.
The researchers also evaluated nausea, multiple labs, and neonatal outcome. Their results stated ondansetron 4 milligrams was the ideal dose to prevent hypotension and other adverse effects during cesarean delivery. Because the participants and anesthesiologists involved were blinded, the level of evidence presented is strong. Exclusion, recruitment criteria, and the results were listed in organized figures. The statistical testing used to evaluate the data was relevant to the research. There were limitations to this study.
Multiple variables were observed, leading to cluttered results. Neonatal outcome was an extraneous variable, as prenatal care is not mentioned. There were several mentions to a previous study the researchers performed, which is confusing to a reader who isn’t familiar with their first study. The study relates to the PICOT question because the main focus was finding a dose of ondansetron that reduced maternal hypotension after spinal anesthesia. This can be used as background information in future studies to find the optimal dose of ondansetron.
