Tehran University Medical Journal

Background: Remifentanil is known to produce side-effects of hypotension and bradycardia. In this study, we examine the effect of low-dose ketamine infusion on the heart rate and blood pressure of patients anesthetized with remifentanil.

Methods: In a randomized clinical trial, 54 patients aged 20-50 years old, with ASA physical status Ι, were studied in two groups (n=27), Ketamine- Remifentanil (K-R group) and Placebo- Remifentanil (P-R group). Exclusion criteria were ASA physical status >1, gastroesophageal reflux, tachycardia, bradycardia, systemic diseases, use of antihypertensive drugs, difficult intubations, risk of aspiration and contraindications of ketamine. Remifentanil was started at a rate of 0.5 µg. kg^-1. min^-1 and anesthesia was induced with thiopental sodium 2 mg.kg^-1. Maintenance of anesthesia included halothane and nitrous oxide/oxygen mixture. Remifentanil infusion was continued in both groups at a rate of 0.5 µg.kg^-1.min^-1. In the K-R group, ketamine was started with an infusion rate of 10 µg.kg^-1. min^-1, 10 minutes after intubation, while in the P-R group, normal saline was started with the same dose of remifentanil. Heart rate, systolic, diastolic and mean arterial blood pressure were measured and compared at 1, 3, 5, 10, 15, 20, 25 and 30 minutes.

Results: No significant differences were found between basic patient characteristics of mean of age, sex, weight, systolic, diastolic and mean arterial blood pressure and heart rate (p>0.2) in the two groups. However, the rate of systolic, diastolic and mean arterial blood pressure changes in the P-R group was significantly greater than that of the K-R group (p<0.006). Heart rate changes were similar between the two groups (p=0.6). Incident of severe hypotension (a decrease of more than 25% of the basic value) was less in the K-R group than that of the P-R group (11% vs. 89% p=0.000).

Conclusion: Low-dose ketamine infusion modulates the effect of remifentanil-induced hypotension and provides better hemodynamic stability during general anesthesia.

Background: Premedication is widely used in pediatric anesthesia to reduce emotional trauma and ensure smooth induction. The rectal route is one of the most commonly accepted means of drug administration. The aim of our study was to investigate and compare the efficacy of rectally administered midazolam versus that of ketamine as a premedication in pediatric patients.

Methods: We performed a prospective randomized double-blinded clinical trial in 64 children, 1 to 10 years of age, randomly allocated into two groups. The midazolam group received 0.5 mg/kg rectal midazolam and the ketamine group received 5 mg/kg rectal ketamine. The preoperative sedation scores were evaluated on a three-point scale. The anxiolysis and mask acceptance scores were evaluated separately on a four-point scale, with ease of parental separation, based on the presence or lack of crying, evaluated on a two-point scale.

Results: Neither medication showed acceptable sedation (>75%), with no significant difference in sedation score between the two groups (P=0.725). Anxiolysis and mask acceptance using either midazolam or ketamine were acceptable, with  midazolam performing significantly better than ketamine (P=0.00 and P=0.042, respectively). Ease of parental separation was seen in both groups without significant difference (P=0.288) and no major adverse effects, such as apnea, occurred in either group.

Conclusions: Rectal midazolam is more effective than ketamine in anxiolysis and mask acceptance. Although they both can ease separation anxiety in children before surgery, we found neither drug to be acceptable for sedation.

Background: Post-tonsillectomy pain is often severe and usually prevents patients from routine eating and drinking. A new option for reducing postoperative pain is "preemptive analgesia", the pre-, intra- or post-operative administration of analgesic agents. Ketamine, an N-methyl D-aspartate receptor antagonist, has recently received attention for this aim. Herein, we study the effect of submucosal injection of ketamine in the tonsillar bed for the reduction of post-tonsillectomy pain.

Methods: In this double-blind clinical trial, three groups of patients underwent infiltration of 0.5mg/kg ketamine, 1mg/kg ketamine or normal saline in their tonsillar bed. Age, sex and weight of patients, duration of surgery, systolic and diastolic blood pressure (before and after surgery), volume of blood loss, reoccurrence of bleeding, time to initiation of oral intake, nausea, vomiting, pain score and dysphasia were recorded in information sheet. Data analysis was performed by one-way ANOVA and chi squared tests, with significance at a P value of <0.5.

Results: There is no significant difference between the three groups with regard to age, sex, weight, duration of surgery, blood pressure (before surgery), volume of blood loss, nausea and vomiting. However, for the ketamine groups, pain score, dysphasia, need for opioid administration and time to initiation of oral intake is significantly lower (P<0.00). Reoccurrence of bleeding was observed in one patient in the lower-dose ketamine group, which is not statistically significant. The effectiveness of the two doses of ketamine is similar, with no statistical difference between the two groups (P=0.84).

Conclusions: This study demonstrated that a submucosal injection of ketamine into the tonsillar bed preoperatively is a safe option for reducing post-tonsillectomy pain, dysphasia, need for opioid and time to initiation of oral intake, without increasing the risk of excessive bleeding, reoccurrence of bleeding, nausea and vomiting.

Background: Emergence agitation (EA) is a post-anesthetic problem which interferes with a child's recovery and presents a challenge in terms of assessment and management. In this study, we compared the effects of midazolam and ketamine as premedication in the management of EA in children aged 1-6 years.

Methods: In this prospective, randomized clinical trial study, 58 children aged 1-6 years who were undergoing general anesthesia for elective surgery in Alzahra Hospital in Isfahan during 2008 until 2009. The patients were randomly assigned to receive 0.1 mg/kg midozolam (28) or 0.5 mg/kg ketamine (29) by IV route in the premedication room. All patients received a standardized anesthetic regimen and isoflurane was used for the maintenance of anesthesia. The incidence and severity of agitation (agitation score), severity of pain (pain score), anesthesia, recovery and extubation durations were recorded postoperatively.

Results: The prevalence of agitation in midazolam (21.4%) was lower than ketamine group (34.5% P<0.05). In addition, the duration of agitation in ketamine group (21±16.67 min) was significantly higher than midazolam group (6.83±6.55 min), (P<0.05). However, no significant differences were seen in agitation score, pain score, anesthesia, recovery or extubation durations in the two groups (P>0.05).

Conclusion: The study showed that midazolam could reduce the frequency of agitation better than ketamine but both drugs were able to reduce the severity of agitation after short-time surgeries in young children.