Clinical Drug Experience Knowledgebase

Randomised Controlled Trial Comparing the Effect of Intravenous Dexamethasone vs. Placebo on the Duration of Analgesia of Spinal Anaesthesia for Caesarean Sections at the Victoria Jubilee Hospital in Jamaica

This study is being conducted in accordance with the Good Clinical Practice guidelines as enunciated in the international Conference on Harmonization (ICP/GCP) of 2016 and the Declaration of Helsinki, 2013.

Sample Size:

The sample size calculated based on a study done by Shahraki et al who studied the efficacy of intravenous Dexamethasone in prolonging the duration of Spinal Anesthesia in elective Caesarean Section in an Indian population (36).

The following values were used for the calculation of the sample size: the required value of α was 5%, β was 10%, a clinically significant difference in Visual Analogue Scale (VAS) score at 1-hour post-surgery was considered 2 and the expected standard deviation was 2.5 (36). The equation used was:

n = (Zα/2+Zβ)2 *2*σ2 / d2,

where Zα/2 is the critical value of the normal distribution at α/2 (α is 0.05), Zβ is the critical value of the normal distribution at β of 0.10. σ2 is the population variance (2.52), and d is the difference to be detected (2). The calculated sample size is 14 patients in each group. In order allow for a potential loss of data up to 10% the target sample size required would be 16 in each group.

Assumptions:

The population size is limited by:

patient's age,
gestational age,
the type of birth - only Caesarian births,
use of a single hospital - VJH
the duration of the research of approximately 2 to 3 months.
As a result of item 1, when the Finite Population model is used to determine the sample size -

S = Z2 * p(p-1) / E2

1 + (Z2 * p(p-1) / E2N)

Other parameters include:

95% Confidence level
Margin of error 5%
Number of live births at VJH in 2016 estimated at 8140 live births
Number of Caesarian births same period = 1652
Percent of Caesarian births (with access to in 2 to 3 months) = 3.6 to 5%

The computed sample size ranges from 53 (2 months) to 72 (3 months) The decision was made to include 30 patients in each group totaling 60 persons for the sample size for this study.

Research assistants received training in the study protocol. Presentations were made to the registration clerks, obstetricians, midwives and other nursing staff to introduce them to the study.

Recruitment The registration clerk informs the patients of the study being carried out from admission to hospital. The ward nurse, upon admitting the patient, determine if they meet the criteria and indicates same to a member of the research team. Written informed consent is obtained by an independent research assistant, once it is confirmed that the patient meets the criteria, to avoid any perception of coercion on the night before or the morning of their procedure. The patient's autonomy is respected and quality medical care will is provided for those who participate in the study as well as those who decline.

Conceptual Definition of Variables Duration of analgesia: the time from intrathecal injection to the time of the first request for analgesia or Visual Analogue Pain Scale score > 4.

Duration of motor blockade: the time from intrathecal injection to the time when the patient is able to flex their knees with free movement of their feet in any plane.

Data Collection/ Storage The data collected for research is stored in a secured area in the Anesthetic Office at the Kingston Public Hospital with access limited to the research team only. Back-up of the data is stored off-site in a locked room in the Anesthetic Office of the University Hospital of the West Indies. Each patient is assigned a study number, and strict security measures are employed to ensure maximum protection of data and the privacy of the research subjects such as password protection and anonymity of data.

If a participant decides to withdraw from the study, the data collected prior to withdrawal may be used in data analysis and the same anonymity applies. Withdrawal from the study will not affect the participant's access to quality health care.

Source Data Verification This is done by cross-referencing the data entered on the data collection forms with the patients' dockets.

Statistical Analysis The data will be managed and analyzed using Statistical Package for the Social Sciences [SPSS] version 26.0 (2019). Uni-variate, bi-variate and multi-variate analysis of the data will be done. Uni-variate analysis will include means ± standard deviation. Bi-variate analysis will include will include independent/ paired t-tests for quantitative data; Chi square test and Mann-Whitney's U test where applicable. Multi-variate analysis will include regression and other measurements where necessary. A p value of less than 0.05 will be deemed statistically significant.