Introduction
This is a critical analysis of two research articles that aims at evaluating the efficacy of propofol and ketamine as anesthetic drugs for children undergoing cardiac catheterization. This analysis will evaluate all the sections of the two research articles in comparison to the literature. There are different kinds of induction anesthesia drugs used in cardiac surgery or diagnostic and intervention catheterization. These medications can be used as a combination or in their pure singular form. For example, Propofol and ketamine are some of the drugs used to anesthetize pediatric Patients undergoing cardiac catheterization or cardiac surgery (Singh et al. 2000). A study by Sakai et al. (1998) found that using a mixture of ketamine and propofol is safe to be used in anesthesia for pediatric patients. According to Singh et al. (2000, p. 36), Anaesthesia drugs such as ketamine and propofol have been used as a mixture or single to maintain “hemodynamic stability” for pediatric cardiac catheterization.
Therefore, the first article to be examined is “Evaluation of Propofol-Ketamine Anaesthesia for Children Undergoing Cardiac Catheterization Procedures” by Gayatri et al. (2007). In this study, the researchers evaluated the safety and efficacy of the continuous intravenous use of ketamine and propofol mixed in one syringe. Gayatri et al.’s (2007) study relied on children patients undergoing either interventions or diagnostic procedures for cardiac catheterization. The second article for critical review is by Akin et al. (2005) and examines the effect of ketamine and propofol on sedative level, hemodynamic during cardiac catheterization, and recovery time. The article is titled “Propofol and Propofol–Ketamine in Paediatric Patients Undergoing cardiac catheterization” (Akin et al. 2005). This assignment will evaluate these two articles and critically analyze them using a critical appraisal framework for critiquing (Holland & Rees 2010). This will be done concerning the methodological approach used by the researchers and the validity and reliability of the data used will also be determined.
The Research Method used for the Review Articles
In this critical review of research, it was significant to develop a research question. In this case, the research question was developed using the Patient, Intervention, Comparison, Outcome (PICO) strategy (Gerrish & Lacey 2010). This step was important because an appropriate and well-built research question allows the correct definition of information. This is so because the evidence is required to resolve the clinical aspect of the investigation; it maximizes recovery in databases; focuses on the purpose of research and avoids unnecessary information (Gerrish & Lacey 2010).
In the research for the above two articles, therefore, the following keywords were used: paediatric patient, cardiac catheterization, ketamine and propofl -hemodynamic. In the search process, where (OR) is used to easily combine searches word with similar meaning, to focus on finding (AND) is used for limitation of years searched option (Gerrish & Lacey 2010).
The Procedure for Search the Article
In the search procedure, the library tab in the online health library of Cardiff University was used. When the database was accessed, the operating department practice was selected and the search was made using two search engines. First, the pudmed search engine was used with the key words “propofol AND ketamine OR paediatric OR cardiac catheterization OR hemodynamic was used where findings were limited to English language. The search was limited to the last ten years and out of the twelve articles that were found in the results, only one was related to the subject of this study. Secondly, Scopus search engine with keywords “propofol AND ketamine OR paediatric OR cardiac catheterization OR hemodynamic” was used where findings were limited to English language. The search was also limited to ten years and out of the results, which were over twenty articles, the abstracts of the articles were scanned and titles evaluated for relevance. Out of the five articles short listed with relevance in the topic, two were selected. The two selected articles were articled were in line with the methods targeted and addressed the clinical aspect of the investigation where a combination of ketamine and propofol are used for cardiac catheterization.
The First Article
The first article selected was “Evaluations of Propofol-Ketamine Anaesthesia for Children’s Undergoing Cardiac Catheterisation Procedures” by Gayatri et al. (2007). The Gayatri et al. (2007) article outlines how ketamine and propofol are administered to children who are about to undergo the procedure heart catheterization. The title of article is clear to draw the attention of interested reader in the study area (Parahoo 2006). The abstract stated in short the aim of the study, sample, method, results, and conclusion of research (Polit & Beck 2010). The provision of this information is necessary to define the prospective of study and helps one to have bird’s eye view of the study.
Background
In the background, the researchers identified that intravenous anaesthesia with mixture of ketamine and propofol are used in a variety of paediatric patients going to do short surgery as illustrated in the study by Kogan et al. (2003). In their analysis, therefore, they held that cardiac catheterization procedures need anaesthesia practise that make sure “stability” of patient hemodynamic as supported by Singh et al. (2000). This background evaluation is significant because it caters for the gaps that medication leaves as side effects after patient’s treatment. Based on the above background Gayatri et al. (2007) advances that searching for better anaesthesia induction medication is progressing because no mixture or alone drugs had received wide acceptance. On the other hand, Sakai et al. (1998) analyses that Ketamine and propofol “pharmacokinetics” side effect is safe to be used in anaesthesia for paediatric patients.
The authors have begun by showing the research studies that have been conducted with regard to various anaesthetic drugs, which ketamine and propofol are part. Various gaps have been put forth in the background and this fulfils the requirements of a sound background as dictated by (Woodall, 2012). Regardless of the fact that propofol and ketamine when used in combination has been shown to yield positive impact on hemodynamic stability, the dosage of propofol-ketamine combination (PKC) in relation to complications is not clear. Regardless of the fact that the authors have used existing knowledge to show inadequacy, they have not given the justification for carrying out the study as is the case in a study by Anna, Alina, Lilit & Haykanush (2008). Therefore, even though there is a clear research question, the importance of this study is not known. This is something that mainly lacks in peer research articles yet very is very imperative because it shows the beneficiaries of the study. Also, the research article fails to introduce some of the complex terms that may not be familiar to a layman like coronary artery bypass surgery, cardiac catheterization and anaesthesia (Northeast Florida Regional Science and Engineering Fair, 2005).
Objective
The research objective in Gayatri et al. (2007) study was to examine safety and efficacy that two different concentration doses from ketamine mixed with propofol given as continuous intravenous administration, will have for paediatric population patient for cardiac catheterization. Objectives of any research study should be related to the topic (Woodall, 2012). They should also be SMART (Fisher & Foreit, 2002). The objective of the first article is to evaluate the efficacy and safety of PKC in cardiac catheterization procedures in children. The objective is not very specific because the variables mentioned (efficacy and safety) are too broad and other more specific variables such as resulting side effects and duration of time taken for the drug to take effect should be used. It is Measureable because it will evaluate these two dimensions of PKC: efficacy and safety. It is achievable because it is realistic; other research studies have investigated different dimensions of the PKC. This study aims at achieving results for dimensions that have not been articulately pointed out: dosage in particular. However, the objective is not time-bound because it does not include a time duration during which the study will be carried out.
Methodology or Broad Approach
The researchers adopted non-blind approach with a randomised allocation to group 1 or 2. Initially, in a controlled clinical trial the main benefit of the blind is to reduce the risk of occurrence of information bias that may arise under the influence of physical or psychological knowledge of the allocated interventions among participants (Hwang et al. 2005). The research study adopted a randomized clinical trial. Clinical trials are like pilot studies that are meant to explore and evaluate the most effective and safe intervention in medical treatment (U. S. Institute of Health, 2012). This is evident in the study because there has not been a universally accepted effective and safe anaesthetic treatment during cardiac catheterization for children.
This was an experimental study and in such a study, there should be no discrimination. All subjects should receive an intervention because they are all on the catheterization procedure and it would be inhumane not to administer anaesthesia to the either one group. The reason why the two groups should receive the intervention is to avoid psychological distress among the subjects. However, this was not the case and this ethical principle seems to have been shrugged off. Dosage levels might lead to the belief that lower levels are not effective and may not work well hence inflicting psychological harm on different subjects. In addition, electronic random tables were used in the randomization process. This is a more accurate and less time consuming sampling procedure. Nonetheless, the research methodology was inadequate and need more justification in terms of sample size determination. In addition, the ethical principle of double/triple blinding ought to have been given attention regardless lack of use of a placebo.
According to Gayatri et al. (2007), no power analysis was conducted before this study. A power analysis was necessary because it is more sensitive to significant changes hence is likely to show that a statistical difference occurs (Mehmet, 2005). It is also used in studies that require two study groups to determine a sample size of replicates that is likely to yield a significant difference (Mehmet, 2005). This is important because it avoid wrongfully accepting the null hypothesis. However, the methodology leaves a gap for the anaesthetists to be biased unless the anaesthetists were blind too. If the anaesthetists were not blind, in this case, then as they drew and give the anaesthetics then one can presume that they knew which child was in which group, and therefore the procedure exposes the study to a significant degree of bias.
Tool of Data Collection
The data was collected through clinical trials (Gayatri et al. 2007). The primary consideration is that patients, who participated in a study of this nature, are confident that the study did not continue once there is reasonable evidence of unacceptable toxicity (Cederblom & Paulsen 2006). The difference between the effectiveness of treatments has been established beyond variations due to the product of chance (Van den Brink-Budgen 2010) or if evidence of an endpoint without conclusive findings clear (Bazin et al. 1997; Badrinath 2000). In catheterization laboratory, standard monitoring equipment is applied for processes like the respiration rate, pules oximetry, the cuff of blood pressure and the ECG of the child among others. In the study by Gayatri et al. (2007) as soon as the paediatric cardiologist performed the procedure, the sedative drugs the anaesthetists managed the vital sign and airway. hthis was significant in ensuring the procedure succeeds in its outcome and without exposing participants to danger during the experiment.
Moreover, the infusion pump prepared with amixture of propofo l25 micriogram per kg per minutes and ketamine 25microgram per kg per minute was connected to patent for group one. As well as propofol 25 microgram per kg per minute of ketamine and 12.5micrigram per kgper minute used for group two (Gayatri et al. 2007). Researcher, in this case, must create an environment in which researchers can produce quickly and efficiently to support research findings underlying biological (Paul 2006). The data collection was done in a catheterisation laboratory with appropriate instrumentation so as to ensure the results of the laboratory are reproducible (Cederblom & Paulsen 2006; Paul 2006). Further, the laboratory equipment with appropriate instrumentation is highly recommended to research team to enable them spend time with the real issues at hand. In this case, the tedious and repetitive procedures can easily have errors when crafted, but with appropriate instrumentation in a laboratory less error was expected (Friedman, Furberg & Demets 1998; Piantadosi 2005). Contemporary and high technological tools such as electrocardiography, pulse oximetry and precordial stethoscope were used in the evaluation. Such tools are important in giving accurate and reliable data. In addition, they are appropriate tools because they measure parameters relevant to the objectives of the study such as pulse rate. Even though lack of blinding may lead to biasness, the use of anaesthesiologists and cardiologists was important for the study because they would address the issues of complications in a professional manner in case need arose. For example, harm on the subjects due to severe complications would lead to a change in dosage or results hence enhance the validity and reliability of the results.
Method of Data Analysis and Presentation
All data’s analysed within student package statistic test to comparing mean with other group for continuous variability “version 11.0.1, SPSS Inc., Chicago, IL” (Gayatri et al. 2007). This test was appropriate given the fact that the statistics generated fulfilled the study objectives. The researchers clearly explained the result in tabular form, and this was appropriate because tables present details of results and give information about different “variables” in a simple understandable way (Gerrish & Lacey 2010).
Sample
According to Gayatri et al. (2007) thirty- two (32) paediatric patents were involved in the prospective randomised study in health education centre and the sample was divided into two groups. However, one loop hole in the study is that it did not mention the population size and it follows that it is not clear whether the sample of thirty two (32) was a representative of the population (Bazin et al. 1997).
Ethics
The Institute ethical team agreed the study and confirmed that every paediatric patient listed for CCP study was consented by parents (Gayatri et al. 2007). No consent was obtained from participants and their caregivers. No one can question the privacy and confidentiality of personal data because the patients’ names were kept anonymous (Botero et al. 2000).
Main Results
The study demonstrated that the use of two doses from ketamine on concentration of 25 microgram and 12.5 microgram perkilogram in one minute with propofol concentration of 25 microgram per kg per minute for paediatric patient is safe and effective. The results showed that the combination works without hemodynamic instability or tract system, and the recovery process is very quick as expected. Time consciousness in this study was more in group 1 with about “60.54.87” minutes while in second group was maintained at “20.13.17.08” minutes (Gayatri et al. 2007). Therefore, the results of the study were in line with the researcher’s objective and they tested the efficacy and safety of the drugs. However, more studies have to be carried out in order to establish whether the results can be applied at different population with different demographics.
Conclusions and Recommendations
The researcher concluded that consciousness recovery period depends on the whole injection of ketamine given in the study, which depends on long procedure. In this case, Hwang et al. (2005) argue that there is no prove that lipid solubility of ketamine and propofol when mixtures made can accrue of a “variable bioavailability.”
In this case, the conclusion by the researchers that the propofol mixture dose of 25 microgram per kilogram per minuteswith 25microgramor,12.5 microgram per kilogram per minutes of ketamine together, is “safe and efficacious” when used for heart catheterization for paediatric patient (Gayatri et al. 2007) might not be appropriate until more study is carried out in this areas. It is significant to note that for any research to be valid, it must be objective in application.
Overall Strengthes and Limitations
According to Gayatri et al. (2007), there is only one study which has been done on this subject at the time of the publication of the article. This is a limitation, although they did not mention it because the study lacks precedence and enough literature for its background. The researchers identified that the small limited number of children listed for research is not enough and concludes that a larger numbers of patient are needed in further study (Smith, White, Nathanson & Gouldson 1994). The article assesses the safe use of the mixture of ketamine and propofol in Cardiac catheterization by Koogan et al. (2003). This calls for more study in the area and makes this study more significant than if it were on another subject. However, the researchers identified that the time to awaken was more in the patients who were receiving 25 µg/kg per minute of ketamine compared to the other group that received a ketamine of 12.5 µg/kg per minute. The researcher assured that the limitation was well within the acceptable laboratory limits.
Application to Practice
This new technique can be a good and safe option in a child for cardiac catheterization, if it is identified that it can function without causing cardiovascular depression or hemodynamic, and maintenance of spontaneous ventilation (Piantadosi 2005; Gozal, Rein, Nir & Gozal 2001). Moreover, new research is needed with higher number of patent in future to assess this type of infusion in cardiac surgery and other diseases, as well as other procedures in catheterization laboratory (Gayatri et al. 2007). These assignments enhance the writer confidence and skill of critiquing in anaesthesia and surgery research.
The Second Article
The second article selected was “Propofol with Ketamine and propofol for cardiac catheterization in Paediatrics Patient” by Akin et al. (2005). The article clearly focused on paediatric Patient listed to heart catheterisations. In this study, it is especially useful to determine whether a new treatment has an advantage compared to the former one. For statistical reasons this study alone may not be enough in determining whether the treatment is effective to objectively applied (Piantadosi 2005).
Abstract
The abstract lacks an introduction that indicates the gap leading to the study (Koopman, 1997). It kicks off by stating the objective of the study. It has summarized the methodology section by giving the number of subjects, research design, and procedure. The procedure makes up for most part of the abstract while other aspects like statistical analysis have not been included. The conclusion given is not clear because it only states that the combination of propofol and ketamine (in low dosage) does not interfere with recover. It is unlike as to whether the other variables: sedation level and hemodynamics, were affected by the drugs or not.
Background
The background to this study and the reason as to why the researchers chose to carry out the study is clear from the abstract and the introduction (Crombie 1996). In this case, ketamine and propofol combination is preverbal for cardiac catheterization in paediatric patients (Akin et al. 2005). The aim of the research is to examine the “effect” of propofol used alone and propofol mixed with ketamine on vital sign, “sedation” score and time of “recovery” “on paediatric patients undergoing cardiac catheterization” (Akin et al. 2005). The second article, just as the first one begins by presenting existing knowledge and stating a position based on this knowledge. In this second article, the goals for anaesthetic management have been outlined which is a good start for a reader who is not knowledgeable on this process. However, this article does not describe the process. The background is very brief and precise. It gives the pros and cons of ketamine and propofol singly as anaesthetic drugs. Then it shows the benefits derived from used ketamine and propofol in combination. This article seeks to fill in the gaps associated with propofol verses propofol-ketamine treatment on those effects that had not been reported on at the time of the research: hemodynamics, sedation level and recovery period. The background however fails to recognize the essence of this research study. Therefore, there is no clarity on how the study is going to benefit the subjects or society at large (Anna, Alina, Lilit & Haykanush, 2008).
The objective of the research study is specific because it highlights the actual parameters that will be studied: hemodynamics, sedation level and recovery period. It is also measurable because it seeks to measure the effects of anaesthetic drugs on the aforementioned parameters. It is achievable because it is based on some underlying knowledge. It is also realistic since these drugs have been previously used by the patients. However, it does not give the duration of time that the study will take.
Methodology or Broad Approach
The research approach was a prospective, randomised; double-blind study (Akin et al., 2005). In double-blind study, both patients and searchers team are not supposed to know the treatment given (Parahoo 2006). The benefit of this type of research methodology approach is to reduce power of suggestions (Parahoo 2006). It is unbelievable that human kind will receive fake “placebo” treatments (Gerrish & Lacey 2010). In a study involving a double-blind approach, the researchers should enrol a large number of people. Dramatically effective treatments studies can prove themselves effective in small studies, but research involving 30 people or less are usually less effective (Gozal, Rein, Nir & Gozal 2001). In the understanding of this topic, the critique of quantitative research used in this study is not directed against the method in general but against single application thereof to investigate social reality (Machin, Day & Green 2006; Friedman, Furberg & Demets 1998). The also model generalises and assumes that in order to achieve greater validity; a condition is often left out of account in the practice of quantitative research (Richard & Elder 2006).
The research was also a randomized prospective study. This entails studying research parameters progressively while focusing on the future. But it was a wrong selection of research design because it does not include the use of two groups (de Vaus, 2001). The double blinded approach used is ethically fit because subjects will not get quizzical about the difference in type of medication given. This study does not factor in some confounding factors that may interfere with results like the nutritional status of the patients. The only baseline characteristics that were taken into account were those related to the objectives of the study. This study just gives the number of subjects included in the study but the criterion used to get this number is not clear. Therefore, attainment of external validity by the study raises eyebrows because it is difficult to generalize data obtained from this study to the larger population. This is because the size of the larger population from where the sample was obtained is not known.
Tool of Data Collection
In this study, the data was collected through clinical trial (Akin et al. 2005). A clinical trial is an experimental study designed to assess the “efficacy” of treatment in humans through the comparison of the results in a group of patients undergoing an experimental treatment with another group of patients receiving a control treatment (Parahoo 2006; Polit & Beck 2010). In general, a clinical trial design considers ethical issues related to the patient and, therefore, involves interim analysis prior to expiration of the total collection of data defined for the study (Parahoo 2006). This data collection method is appropriate for the research because data is analysed as the research continues and the expiry date does not beat the researchers. However, the results obtained are not accurate because they are not a representative of the whole population and, therefore, may not be highly reliable. The interim analysis performed on the accumulated data at a given time is performed in order to determine the existence of significant differences between treatments so as to compare and determine the possibility of stopping the study early (Senn 2008).
Method of Data Analysis and Presentation
The data obtained in the study was analysed by evaluating the hemodynamic data by conducting “unpaired Student’s t-test—gender, adverse effects, and the number of patients requiring additional fentanyl, the number of patients showing larger than 20% variation of hemodynamic data was determined by chi-square, Fisher’s exact test” (Akin et al. 2005, p.554). These tests statistics were significant because it tested the efficacy of the procedure in the target population. The researchers also relied on the Mann– Whitney test in analysing the “number of additional propofol doses” (Akin et al. 2005, p.554). In the presentation of the analysed data, the researchers clearly defined the results tabular form, and this is scholarly because tables present details of results and give information about different variables in a way that results can be interpreted and understood easily (Gerrish & Lacey 2010).
Unpaired t-test is used to compare two population means (Shier, 2004). Therefore, this test was appropriate because the study comprises of two study populations. T-test is used to test difference in continuous type of data, which comprise of hemodynamic parameters. Chi-square is used to test for significant difference of categorical variables, just as the study has done. Since the additions are not normally distributed a nonparametric test is ideal. In this case, Mann Whitney is used because there are two population means and the variable under testing is continuous.
Sample
The sample used in this study included 60 paediatric patients; aged between one month and thirteen years on the Society of American Anaesthesiologists status. All participants were selected on the basis that they were scheduled for elective “cardiac catheterization for the evaluation of congenial heart disease” (Akin et al. 2005, p.554). The sample population characteristic is appropriate for this study, but it is significant to note that the researchers did not define the total population. Therefore, it is not clear whether the sample of 60 was a representative of the undefined population.
Ethical Considerations
Ethical criteria are essential in any clinical trial. As in this study, participants were informed and patient participants consented to their taking part in the trial (Akin et al. 2005). In such a procedure, patients should be warned of potential risks in a comprehensive way and the researchers should have participant’s religious and cultural consideration (Gerrish & Lacey 2010). This means that all clinical trials must go through and be approved by an ethics committee (Botero et al. 2000). This committee verifies the scientific and medical interest of the study, the risk, benefit, and ensure that the study trial is carried out in line with good methodological practices. This is important especially those trials concerning the sponsor and the principal investigator of the study and the presence of insurance to indemnify so as to allow participants in the study in case of damage (Senn 2008). All these considerations were made and fulfilled before this trial was carried out, and this helped in avoiding conflicts of interests among all interested parties (Bazin et al. 1997).
Main Findings
The article presented the main findings in a way that any reader can understand because the results are in table form. The tables are simple and well illustrated so that one can understand the measurements against variables whore results are being represented. There are also explanations and simple descriptions of each result in the tables.
Overall Strengths and Limitations
The main strength of this study is that its topic was not much researched and the methodology of a prospective, randomised, double-blind is known to be very strong in giving objective results (Van 2010). However, the study remained limited to children interviewed and so the research done is mainly clinical study, which requires deferent specialist and advanced centre to do a more comprehensive trial with larger population to test the wide applicability of the study results (Akin et al. 2005).
Conclusion
The two studies are significant in their findings because they give a starting point in the study of the use of different kinds of induction anaesthesia drugs for cardiac patients before they have cardiac surgery or diagnostic and intervention catheterization. They, therefore, contribute substantially to knowledge and research skill especially the material subject related to cardiac anaesthesia. Both articles have outlined the benefits of more research on the topic and have increased confidence in the operating department team to seek more knowledge regarding the method of anaesthesia used in cardiac surgery and catheterization paediatric. The impact of these studies is significant because the researchers are members of staff in internationally recognised research groups (Cato 1988). Lastly, it is vital to note that many researchers argue that the side effect of propofol on heart and respiration can discourage its use in paediatric patients’ proceeding of cardiac catheterization (Piantadosi 2005). However, these researchers have proved that when a small dose of ketamine is added to propofol, it will leave the main arterial blood pressure in good conditions without extending recover time. This way, the mixtures will remain the only better option for paediatric patient in cardiac catheterizations (Piantadosi 2005). The studies have called for more researches on this area so as to determine and authenticate their findings from different settings and populations.
Reference List
Akin, A, Esmaoglu, A, Guler, G, Demircioglu, R, Narin, N & Boyaci, A 2005, “Propofol and Propofol-Ketamine in Paediatric Patient Undergoing Cardiac Catheterization”, Paediatric cardiology, vol. 26, no.5, pp. 553-557.
Anna, M., Alina, P., Lilit, G., & Haykanush, C. (2008). Return Migration to Armenia in 2002-2008. Yerevan: OSCE.
Badrinath, S, Avramov, MN, Shadrick, M et al. 2000 ‚“The Use Of Ketamine And Propofol Combinations During, Monitored, Anaesthesia Cares”, Anaesthesia Analogies, vol. 90, pp. 858-862.
Bazin, JE, Giannelloni, C, Dauphin, C et al. 1997 “Evaluationof Sevoflurane, New Anaesthetic Agents during Paediatric Cardiac Catheterization”, Arch Mal Coeur Vaiss, vol. 90, pp. 657-660.
Botero, CA, Smith, CE, Holbrook, C et al. 2000, “Total Intravenous Anaesthesia With A-Ketamine-Orpopofol Combination During Coronary Artery Surgery”, J Cardiothoracic, Vasc, Anesth, vol. 14, pp. 409-415.
Cato, EC (ed.) 1988, Clinical Trials and Tribulations, Marcel Dekker, New York.
Cederblom, J & Paulsen, DW 2006, Critical Reasoning: Understanding and criticizing arguments and theories, 6th edn, Thomson Wadsworth, Belmont, CA.
Crombie, IK 1996, The Pocket Guide to Critical Appraisal: A Handbook for Health Care Professionals, BMJ, London.
de Vaus, D. (2001). Research Design in Social Research. London: Sage.
Fisher, A., & Foreit, J. (2002). Designing HIV/AIDS Intervention Studies: An Operations Research Handbook. Washington, DC: Population Council.
Friedman, LM, Furberg, CD & Demets, DL 1998, Fundamentals of Clinical Trials, 3rd edn, Springer Science, New York.
Gayatri, P, Puthussery, RS & Sinha, PK 2007, “Evaluations of Propofol-Ketamine Anaesthesia for Children’s Undergoing Cardiac Catheterisation Procedures”, Journal of Interven Cardiol, vol. 20, pp. 158–163.
Gerrish, K & Lacey, A 2010, The Research Process in Nursing, 5 edn, Blackwell publishing, New York.
Gozal, D, Rein, AJ, Nir, A & Gozal, Y 2001, “Propofol does not modify the hemodynamic status of children with intracardiac shunts undergoing cardiac catheterization”, Paediatric Cardio, vol. 22, pp.488–490.
Holland, K & Rees, C 2010, Frameworks for Critiquing Research Articles, Web.
Hwang, J, Jeon, J, Lim, YJ et al. 2005, “Comparison of alfentanil and ketamine in combination with propofol for patient-controlled sedation during fibre optic bronchoscopy”, Acta Anaesthesiology Scand, vol. 49, pp. 1334–1338.
Kogan, A, Efrat, R, Katz, J et al. 2003, “Propofol-Ketamine Mixture for Anaesthesia in Paediatric Patients Undergoing Cardiac Catheterization”, Cardiothoracic Vasc Anesth, vol.17, no.6, pp. 961-963.
Koopman, P. (1997). How to Write an Abstract. Web.
Machin, D, Day, S & Green, S 2006, Textbook of Clinical Trials, 2nd edn, Wiley, Hoboken NJ.
Mehmet, S. (2005). Retrospective Power Analysis: When? Radiology, 237, 743-744.
Northeast Florida Regional Science and Engineering Fair. (2005). Web.
Parahoo, K 2006, Nursing Research: Principles, Process and Issues, 2nd edn, Macmillan, Palgrave.
Piantadosi, S 2005, Clinical Trials: A Methodological Perspective, 2 edn, Wiley, Hoboken, NJ.
Polit, DF & Beck, CT 2010, Essentials of Nursing Research: Appraising Evidence For Nursing Practice, 7th edn, Wolters Kluwer Health/Lippincott Williams & Wilkins, Philadelphia.
Richard, P & Elder, L 2006, Critical Thinking Tools for Taking Charge of Your Learning and Your Life, Prentice Hall Publishing, New Jersey.
Sakai, T, Ebina, T et al. 1998, “Pharmacokinetic of Propofol and Ketamine during and After Total Intravenous Anaesthesia With Propofol, Fentanyl And Ketamine For Paediatric Patients”, Masui, vol. 47, pp. 277-280.
Senn, S 2008, Statistical Issues in Drug Development, 2nd edn, Wiley, Hoboken, NJ.
Shier, R. (2004). Statistics. Web.
Shier, R. (2004). The Mann Whitney U Test. Web.
Singh, A, Girotra, S, Mehta, Y et al. 2005, “Total Intravenous Anaesthesia with Ketamine for Paediatric Interventional Cardiac Procedures”, J Cardiothoracic VascAnesth, vol.14, pp. 36–39.
Smith, I, White, PF, Nathanson, M & Gouldson, R 1994, “Propofol”, Anaesthesiology, vol.81, pp. 1005–1043.
Van den Brink-Budgen, R 2010, Critical Thinking for Students, How to Books, Oxford.
Woodall, W. (2012). Writing the Background and Significance Section. Web.