Review article: Intravenous vs intramuscular ketamine for pediatric procedural sedation by emergency medicine specialists: a review

Ketamine is a general anesthetic agent widely used for pediatric procedural sedation outside the operating theater by nonanesthesiologists. In a setting where efficacy and safety of the agent are paramount, there are conflicting recommendations in terms of optimal mode of parenteral administration, as well as optimal dosage and need for the coadministration of adjunctive agents to decrease side effects. We investigated existing evidence to determine whether ketamine should be best administered intravenously or intramuscularly. This analysis was made difficult by limited direct comparisons of both modes of parenteral administration and a lack of consistent definitions for key outcomes such as ‘effectiveness,’‘adverse events,’‘hypoxia,’‘ease of completion of the procedure,’ and ‘satisfaction’ across studies that have evaluated ketamine. Based on large data sets, the safety and efficacy of both modes of administration are broadly similar. Although data on head to head comparisons of intravenous and intramuscular ketamine is limited, based on our analysis, we conclude that the trends indicate ketamine is ideally administered intravenously.     

Exploring the pharmacokinetics of oral ketamine in children undergoing burns procedures

Aims: The aim of this study was to describe ketamine pharmacokinetics when administered orally to children suffering from burn injury in >10% body surface area. Methods: Children (n = 20) were given ketamine 5 or 10 mg·kg^?1 orally 20 min prior to presentation for surgical procedures. Anesthesia during procedures was maintained with a volatile anesthetic agent. Additional intravenous ketamine was given as a bolus (0.5–1 mg·kg^?1) to nine children during the procedure while a further nine children were given an infusion (0.1 mg·kg^?1·h^?1) continued for 4–19 h after the procedure. Blood was assayed for ketamine and norketamine on six occasions over the study duration of 8–24 h. Data were pooled with those from an earlier analysis (621 observations from 70 subjects). An additional time–concentration profile from an adult given oral ketamine was gleaned from the literature (17 observations). A population analysis was undertaken using nonlinear mixed‐effects models. Results: The pooled analysis comprised 852 observations from 91 subjects. There were 20 children who presented for procedures related to burns management (age 3.5 sd 2.1 years, range 1–8 years; weight 14.7 sd 4.9 kg, range 7.9–25 kg), and these children contributed 214 ketamine and norketamine observations. A two‐compartment (central, peripheral) linear disposition model fitted data better than a one‐compartment model. Bioavailability of the oral formulation was 0.45 (90% CI 0.33, 0.58). Absorption half‐time was 59 (90% CI 29.4, 109.2) min and had high between‐subject variability (BSV 148%). Population parameter estimates, standardized to a 70‐kg person, were central volume 21.1 (BSV 47.1%) l·70 kg^?1, peripheral volume of distribution 109 (27.5%) l·70 kg^?1, clearance 81.3 (46.1%) l·h^?1·70 kg^?1, and inter‐compartment clearance 259 (50.1%) l·h^?1·70 kg^?1. Under the assumption that all ketamine was converted to norketamine, the volume of the metabolite was 151.9 (BSV 39.1%) l·70 kg^?1 with an elimination clearance of 64.4 (BSV 63.4%) l·h^?1·70 kg^?1 and a rate constant for intermediate compartments of 26.2 (BSV 52.1%) h^?1·70 kg^?1. Conclusions: The ketamine pharmacokinetics in children with minor burns are similar to those without burns. The peak ratio of norketamine/ketamine at 1 h is 2.8 after oral administration allowing an analgesic contribution from the metabolite at this time. There is low relative bioavailability (<0.5) and slow variable absorption. Dose simulation in a child (3.5 years, 15 kg) suggests a dose regimen of oral ketamine 10 mg·kg^?1 followed by intravenous ketamine 1 mg·kg^?1 i.v. with the advent of short‐duration surgical dressing change at 45 min.     

Procedural sedation for insertion of central venous catheters in children: comparison of midazolam/fentanyl with midazolam/ketamine

Background: There is a lack of studies evaluating procedural sedation for insertion of central venous catheters (CVC) in pediatric patients in emergency departments or pediatric intensive care units (PICU). This study was designed to evaluate whether there is a difference in the total sedation time for CVC insertion in nonintubated children receiving two sedation regimens. Methods: Patients were prospectively randomized to receive either midazolam/fentanyl (M/F) or midazolam/ketamine (M/K) i.v. The Children's Hospital of Wiscosin Sedation Scale was used to score the sedation level. Results: Fifty seven patients were studied (28 M/F and 29 M/K). Group M/F received midazolam (0.24 ± 0.11 mg·kg⁻¹) and fentanyl (1.68 ± 0.83 μg·kg⁻¹) and group M/K received midazolam (0.26 ± 0.09 mg·kg⁻¹) and ketamine (1.40 ± 0.72 mg·kg⁻¹). The groups were similar in age, weight, risk classification time and sedation level. Median total sedation times for M/F and M/K were 97 vs 105 min, respectively (P = 0.67). Minor complications occurred in 3.5% (M/F) vs 20.7% (M/K) (P = 0.03). M/F promoted a greater reduction in respiratory rate (P = 0.005). Conclusions: In this study of nonventilated children in PICU undergoing central line placement, M/F and M/K provided a clinically comparable total sedation time. However, the M/K sedation regimen was associated with a higher rate of minor complications. A longer period of study is required to assess the efficacy and safety of these sedative agents for PICU procedures in nonintubated children.     

Investigating the pharmacodynamics of ketamine in children

BACKGROUND: The aim of this study was to describe ketamine pharmacodynamics (PD) in children. Adult ketamine concentrations during recovery are reported as 0.74 mg.l(-1) (sd 0.24 mg.l(-1)) with an EC(50) for anesthesia of 2 mg.l(-1) (sd 0.5 mg.l(-1)), but pediatric data are few. METHODS: Children presenting for painful procedures in an Emergency Department were given ketamine 1-1.5 mg.kg(-1) i.v. Blood was assayed for ketamine on three to six occasions (median 3) over the subsequent 14-152 min (median 28.5). Procedures were videotaped. Level of sedation (0-5; unresponsive - spontaneously awake without stimulus) and a test of memory were recorded. PD was investigated using a variable slope E(max) model (sedation) or logistic regression (arousal time, memory) with nonlinear mixed effects models. RESULTS: In total 60 children were enrolled. Pharmacokinetic data were collected in 54 of these children and there were 43 children available for PD study. The mean age was 8.15 years (sd 3.5 years) and weight was 34.9 kg (sd 15.8 kg). The half-time describing equilibration between the effect compartment and central compartment was 11 s (95% CI 0.07-20 s). The EC(50) for arousal was 0.52 (90% CI 0.22-1.17) mg.l(-1). The E(max) model with a baseline (E(0)) of five (spontaneously awake without stimulus) yielded a fractional E(max) 0.939 [coefficient of variability (CV) 24%], an EC(50) 0.56 (CV 136%) mg.l(-1) and a Hill coefficient 3.71. The EC(50) for recall memory was 0.44 (90% CI 0.09-1.70) mg.l(-1). The EC(50) for remembering was 0.38 (90% CI 0.12-1.75) mg.l(-1). CONCLUSIONS: Concentrations associated with arousal in children are analogous to adults. The ability to recall and remember occurs at similar concentrations to those associated with arousal. A concentration of 1 mg.l(-1) was associated with a sedation level of three or less (arouses to consciousness with moderate tactile or loud verbal stimulus) in 95% of children while 1.5 mg.l(-1) was associated with a sedation level of two or less (rouses slowly to consciousness with sustained painful stimulus) in 95% of children. These concentrations can be attained for 3-4 min after 1 mg.kg(-1) and 1.5 mg.kg(-1) ketamine IV bolus, respectively. The mean arousal time can be anticipated at approximately 10 min (1 mg.kg(-1)) and 15 min (1.5 mg.kg(-1)).     

Sedation with ketamine and low-dose midazolam for short-term procedures requiring pharyngeal manipulation in young children

BACKGROUND: Pediatric intestinal biopsy procedures including considerable transpharyngeal manipulation of a wire-guided metal capsule require adequate sedation or anesthesia. This retrospective cohort study was designed to evaluate intravenous sedation with ketamine and low-dose midazolam in young children undergoing these procedures before and also after discharge from the hospital. METHODS: A total of 244 biopsy procedures in 217 children under the age of 16 years were evaluated. All anesthesia records were reviewed according to a defined study protocol and in 145 cases the parents were also interviewed by telephone to obtain further information on possible adverse effects before and after discharge. RESULTS: Ketamine and low-dose midazolam were carefully titrated by an experienced anesthesia team at an approximate dose ratio of 40 : 1 (total doses 2.3 and 0.05 mg.kg(-1)) in continuously monitored spontaneously breathing children. Possibly associated problems before discharge were salivation (5.7%), vomiting (4.9%), oxygen desaturation (3.3%), laryngospasm (2.5%) and rash (1.2%) according to the patient records and blurred vision (27%), nausea and vomiting (19%), vertigo (13%) and hallucinations or nightmares (3.5%) according to telephone interviews. Few, mild and transient problems remained after discharge from the hospital. CONCLUSIONS: Careful titration of ketamine and low-dose midazolam provides adequate sedation for nonsurgical pediatric short-term procedures also requiring considerable pharyngeal manipulation, particularly considering the low number of serious airway problems such as laryngospasm. The high incidence of late postoperative problems suggests that prospective studies should be designed for long-term follow-up of young children subjected to sedation or anesthesia.     

Ketamine disposition in children presenting for procedural sedation and analgesia in a children's emergency department

BACKGROUND: The aim of this study was to describe ketamine pharmacokinetics in children to simulate time-concentration profiles to predict duration of concentrations associated with anesthesia, arousal and analgesia. METHODS: Children presenting for painful procedures in the Emergency Dept were given ketamine 1-1.5 mgxkg(-1) i.v. Blood was assayed for ketamine on 3-6 occasions (median 3) over the subsequent 14-152 min (median 28.5). A population pharmacokinetic analysis was undertaken by using nonlinear mixed effects models (NONMEM). Simulation was used to predict time-concentration profiles in this cohort RESULTS: There were 188 observations from 54 children (age 8.3 sd 3.5 years, weight 32.5 sd 15.6 kg). A two-compartment (central, peripheral) linear disposition model fitted data better than a one-compartment model. Population parameter estimates and their between subject variability (BSV), standardized to a 70-kg person using allometric models, were central volume (V1) 38.7 (BSV 64%) l.70 kg(-1), peripheral volume of distribution (V2) 102 (51.7%) l.70 kg(-1), clearance (CL) 90 (38.1%) l.h(-1) 70 kg(-1) and intercompartment clearance (Q) 215 (19%) l.h(-1) 70 kg(-1). At 10 min half of the children given 1 mgxkg(-1) will have a serum concentration below 0.75 mgxl(-1). This is a concentration associated with 'awakening' in adults. However, almost all the children will still have a serum concentration above 0.1 mgxl(-1), a level associated with analgesia in adults. CONCLUSIONS: Ketamine 1 mgxkg(-1) i.v. provides satisfactory serum concentrations for children undergoing sedation for painful procedures of <5-min duration and produces concentrations associated with analgesic effect for more than 10 min. Clearance increases with decreasing age in children. The relationship between serum concentration and effect is poorly defined in children.     

Pretreatment with intravenous ketamine reduces propofol injection pain

BACKGROUND: Paediatric procedural sedation using propofol has been shown to be safe and effective and is widely used. Pain at the injection site is a frequent complaint and can be particularly distressing for children, especially for those undergoing repeated procedures. Ketamine has analgesic properties and can diminish the incidence of propofol infusion pain in adults. The aim of the study was to investigate whether pretreatment with ketamine would reduce infusion line pain in propofol sedation in children. METHODS: We performed a prospective, randomized, double-blind trial in a paediatric sedation unit of a tertiary referral teaching hospital. A total of 122 children admitted for gastroscopy were randomly allocated into two groups. Group 1 received atropine and ketamine before propofol infusion. Group 2 received atropine, normal saline solution, and a mixture of propofol with lidocaine. The main outcome measure evaluated was pain associated with the infusion and secondary outcome measures were mean medium arterial pressure decrease and desaturation. RESULTS: The incidence of pain of the infusion was significantly lower in patients pretreated with ketamine (8% vs 37%, P = 0.0001). CONCLUSIONS: Pretreatment with ketamine (0.5 mg.kg-1) is very effective in preventing propofol infusion pain.     

The evolution of ketamine applications in children

Ketamine has found many applications in pediatric anesthetic practice. Insights into the mechanism of action and the pharmacokinetics and pharmacodynamics of its isomers have led to a re‐evaluation of this drug, expanding the range of applications in children. Ketamine is a remarkably versatile drug that can be administered through almost any route. It can also be used for different purposes. The aim of this review is to look at the possible applications of this drug in children.     

Nasal midazolam and ketamine for paediatric sedation during computerised tomography

We have studied the sedation achieved with a mixture of midazolam (0.56 mg–kg^-1) and ketamine (5 mg kg^-1) administered nasally in 30 children weighing less than 16 kg undergoing computerised tomography. Assessment was two fold using a visual analogue scale; the radiologist/radiographer rated the exam from "failed examination" to "perfect working conditions" while the anesthetist's assessment ranged from "poor sedation" to "perfect sedation with clinical well being". This new method proved to be effective alone in 83% of the cases and there were no complications. The rapid onset obtained after intranasal midazolam and ketamine offers advantages over orally or rectally administered drugs. The absence of respiratory depression and oxygen desaturation suggests that this technique is safe and efficient in the CT room with its particular working conditions.     

Comparison of propofol versus propofol‐ketamine combination for sedation during spinal anesthesia in children: randomized clinical trial of efficacy and safety

Objectives: This study was designed to compare the efficacy and safety of propofol vs propofol‐ketamine combination for sedation during pediatric spinal anesthesia. Methods: Forty children, aged 3–8 undergoing spinal anesthesia for lower abdominal surgeries were included. Participants were randomly assigned into two groups. Group 1 received propofol bolus of 2 mg·kg^?1 followed by an infusion of 4 mg·kg^?1·h^?1. Group 2 received a combination of 1.6 mg·kg^?1 propofol and 0.4 mg·kg^?1 ketamine followed by an infusion of 3.2 mg·kg^?1·h^?1 and 0.8 mg·kg^?1·h^?1, respectively. The infusion rate was titrated to keep the child sedated at University of Michigan Sedation Score of 3. The heart rate, blood pressure, respiratory rate and oxygen saturation were recorded every 5 min. The episodes of spontaneous body movements and requirement of supplemental sedation were recorded. The postoperative recovery was assessed by modified Aldrette score. Results: Seventeen patients in group 1 and four patients in group 2 (P < 0.001) required extra boluses of study drug to prevent movements during lumbar puncture. Four patients experienced respiratory depression and three airway obstruction in group 1 when compared to one patient each in group 2 (P < 0.05). The recovery time was similar in both groups. None of the patient had postoperative nausea/vomiting or psychomimetic reactions. Conclusions: Propofol‐ketamine combination provided better quality of sedation with lesser complications than propofol alone and thus can be a good option for sedation during spinal anesthesia in children.     

Experience with a propofol-ketamine mixture for sedation during pediatric orthopedic surgery

Background: Various combinations of propofol and ketofol have been described for the provision of procedural sedation in both adults and children. Utilization of ‘ketofol’ for deep sedation during prolonged pediatric orthopedic procedures has not previously been described. Methods: During an orthopedic aid trip, a 1:1 mixture of propofol and ketamine (200 mg of each drawn up to 22 ml) was utilized to provide deep sedation or general anesthesia as an adjunct to regional analgesia for lower limb surgery. Details for 18 patients having a total of 19 procedures were recorded with a record of intraoperative and postoperative parameters including initial bolus doses and infusion rates of ketofol required to produce deep sedation. Results: Mean operating time was 153.7 min (range 64–241 min). The mean initial bolus dose of ketofol was 0.19 ml·kg^?1 (range 0.1–0.5 ml·kg^?1) or 1.7 mg·kg^?1 each of propofol and ketamine (range 0.9–4.5 mg·kg^?1). The mean upper limit of the infusion rate required to maintain deep sedation was 0.19 ml·kg^?1·h^?1 (range 0.07–0.26 ml·kg^?1·h^?1) or 1.7 mg·kg^?1·h^?1 (range 0.6–2.4 mg·kg^?1·h^?1) and the mean lower limit of the infusion rate was 0.08 ml·kg^?1·h^?1 (range 0.02–0.13 ml·kg^?1·h^?1) or 0.7 mg·kg^?1·h^?1 (range 0.2–1.2 mg·kg^?1·h^?1). The mean initial bolus dose of ketofol was 0.19 ml·kg^?1 (range 0.1–0.5 ml·kg^?1). There were no episodes of hypo‐ or hypertension or of desaturation. Mean time to eye opening after infusion cessation was 5.1 min (median 2 min; range 0–17 min). Conclusion: Ketofol successfully produced deep sedation for prolonged pediatric orthopedic procedures in conjunction with regional analgesia. Further research to confirm its safety and applicability to a wider range of settings is required.     

盐酸氯胺酮与异丙酚复合应用的研究进展

介绍氯胺酮与异丙酚复合应用于镇静、麻醉诱导与维持,对血液动力学、脑血流以及对缺氧性肺血管收缩的影响。     

Propofol-ketamine vs propofol-fentanyl for sedation during pediatric upper gastrointestinal endoscopy

BACKGROUND: The aim of this study was to compare the clinical efficacy and safety of propofol-ketamine with propofol-fentanyl in pediatric patients undergoing diagnostic upper gastrointestinal endoscopy (UGIE). METHODS: This was a prospective, randomized, double blinded comparison of propofol-ketamine with propofol-fentanyl for sedation in patients undergoing elective UGIE. Ninety ASA I-II, aged 1 to 16-year-old patients were included in the study. Heart rate (HR), systolic arterial pressure, peripheral oxygen saturation, respiratory rate (RR) and Ramsey sedation scores of all patients were recorded perioperatively. Patients were randomly assigned to receive either propofol-ketamine (PK; n = 46) or propofol-fentanyl (PF; n = 44). PK group received 1 mg x kg(-1) ketamine + 1.2 mg x kg(-1) propofol, and PF group received 1 microg x kg(-1) fentanyl + 1.2 mg x kg(-1) propofol for sedation induction. Additional propofol (0.5-1 mg x kg(-1)) was administered when a patient showed discomfort in either group. RESULTS: The number of patients who needed additional propofol in the first minute after sedation induction was eight in Group PK (17%), and 22 in Group PF (50%) (P < 0.01) and those who did not need additional propofol throughout the endoscopy were 14 in Group PK (30%) and three in Group PF (7%) (P < 0.01). HR and RR values after induction in Group PF were significantly lower than Group PK (P < 0.01). CONCLUSIONS: Both PK and PF combinations provided effective sedation in pediatric patients undergoing UGIE, but the PK combination resulted in stable hemodynamics and deeper sedation though more side effects.     

Use of a remifentanil-propofol mixture for pediatric flexible fiberoptic bronchoscopy sedation

BACKGROUND: Flexible fiberoptic bronchoscopy is an important diagnostic tool for pediatric pulmonologists. Because of its favorable respiratory profile, ketamine has become a popular sedative for this procedure, but may be associated with unpleasant emergence reactions in the older child. Remifentanil is a newer, ultra-short acting opioid that has been shown to provide effective sedation and cough suppression for fiberoptic bronchoscopy when combined with intermittent propofol boluses. However, delivery of these agents as a combined, single infusion has not been described. METHODS: Children > or =2 years of age undergoing fiberoptic bronchoscopy were enrolled. Remifentanil was mixed in a single syringe with undiluted propofol giving final drug concentrations of 10 mg x ml(-1) of propofol and 15-20 microg x ml(-1) of remifentanil. Sedation was induced with a bolus of approximately 0.1 ml x kg(-1) of this mixture and maintained by titrating the drip throughout the procedure. Vital signs, sedative effectiveness, recovery patterns, and complications were prospectively recorded. RESULTS: Fifteen patients aged 9.0 +/- 5.3 years were sedated. Sedation was induced with 1.2 +/- 0.4 mg x kg(-1) propofol (2.4 +/- 0.8 microg x kg(-1) remifentanil) and maintained with 4.1 +/- 1.8 mg x kg(-1) x h(-1) propofol (0.13 +/- 0.06 microg x kg(-1) x min(-1) remifentanil). Five patients received low-dose ketamine to augment sedation. The maximal decrease in respiratory rate was 6.1 +/- 5.3 b x min(-1) (27.6 +/- 21%) and no patient became hypoxemic. All procedures were completed easily without significant complication. Patients recovered to baseline 13.3 +/- 8.5 min following infusion discontinuation. CONCLUSIONS: A remifentanil/propofol mixture provided effective sedation and rapid recovery in pediatric patients undergoing fiberoptic bronchoscopy.     

Electroencephalographic Narcotrend Index monitoring during procedural sedation and analgesia in children

Background:  The electroencephalographic Narcotrend Index (NI) may potentially help to titrate sedative medication during diagnostic and therapeutic procedures in children.
Methods:  With local ethics committee approval and informed parental consent, 31 patients, aged 8.9 ± 4.3 years, scheduled for elective upper gastrointestinal endoscopy were enrolled in this prospective, double-blinded observational study. Initially, patients received a single dose of intravenous piritramide 0.1 mg·kg⁻¹, followed by propofol 2 mg·kg⁻¹ and, if necessary, additional propofol doses (0.5 mg·kg⁻¹) to achieve and maintain a level of deep sedation throughout the procedure. Sedation was assessed by the University of Michigan Sedation Scale (UMSS). We investigated the relationship between depth of sedation, and the NI, and the classical EEG parameters (cEEG), total EEG power (Power), spectral edge (SEF) and median frequency, and relative power in the beta, alpha, theta and delta bands. The performance of the NI and cEEG parameters was evaluated by prediction probability ( P _K), receiver operating characteristic (ROC) and Spearman rank order correlation analysis.
Results:  Mean P _K values for NI (0.88) vs UMSS were higher than for the other cEEG parameters, except for Power (0.82) and SEF(0.81). Spearman correlation analysis revealed superiority of the NI over all cEEG parameters. The area under the curve for the NI was 0.93, which was superior to all other EEG parameters beside Power (0.86) and relative power in alpha (0.82).
Conclusions:  The results of this study suggest that the NI may be an objective nondisruptive tool for assessment of hypnotic depth in children under propofol-induced procedural sedation.     

Appropriate method of administration of propofol, fentanyl, and ketamine for patient-controlled sedation and analgesia during extracorporeal shock-wave lithotripsy

Purpose. The aim of this study was to identify the appropriate method for administering propofol, fentanyl, and ketamine (PFK) for patient-controlled sedation and analgesia (PCSA) during extracorporeal shock-wave lithotripsy (ESWL). Methods. Twenty-one unpremedicated patients were randomly assigned to three groups that received different drug administration regimens. (group 1: low loading dose and high demand bolus, group 2: high loading dose and demand bolus, group 3: high loading dose and low demand bolus). Results. The patients in all groups were hemodynamically stable during ESWL. Oxygen desaturation was recognized in all groups, but was avoided by 2 l·min⁻¹ of oxygen supply via a nasal prong. The total administration dose of the drugs was significantly higher (P < 0.05) in group 2 than in groups 1 and 3. The median level of sedation was the same, but the episodes of oversedation were not recognized in group 3 (P < 0.05). A significant difference in the frequency of episodes of oversedation was found between groups 2 and 3 (P < 0.05). The results were good or excellent for almost all patients, and were assessed as fair by only one patient in group 2. Conclusion. We concluded that the method used for group 3 is the most appropriate for administering PFK for PCSA during ESWL. Received for publication on June 23, 1999; accepted on December 7, 1999     

Safe sedation of children for diagnostic and therapeutic procedures

There is an increasing use of sedation in children requiring imaging and other minor procedures. This article will discuss how sedation can be safely performed. The depth of sedation has been classified into minimal, moderate and deep according to the National Institute for Health and Care Excellence. Amongst others, benefits of sedation include increased parental and child satisfaction, increased cost ben- efits for the hospital and reduced adverse effects of general anaes- thesia such as emergence delirium and postoperative nausea and vomiting. Safe sedation can be used for a wide range of procedures, most commonly for CT and MRI. Others include removing drains, changing burns dressings, simple plastic surgery procedures and endoscopy. Drugs can be used as sole agents or in combination to produce the desired level of sedation appropriate for the procedure. The children must be monitored according to the depth of sedation and personnel should be trained in the management of potential complications.     

Rescue sedation with dexmedetomidine for diagnostic imaging: a preliminary report

BACKGROUND: Sedation is frequently required during noninvasive radiological imaging in children. Although commonly used agents such as chloral hydrate and midazolam are generally effective, failures may occur. The authors report their experience with dexmedetomidine for rescue sedation during magnetic resonance imaging. METHODS: A retrospective chart review was undertaken. RESULTS: The cohort included five patients ranging in age from 11 months to 16 years. Following the failure of other agents (chloral hydrate and/or midazolam), dexmedetomidine was administered as a loading dose of 0.3-1.0 microg x kg(-1) x min(-1) over 5-10 min followed by an infusion of 0.5-1.0 microg x kg(-1) x h(-1). The dexmedetomidine loading dose required to induce sedation was 0.78 +/- 0.42 microg x kg(-1) (range 0.3-1.2). The maintenance infusion rate was 0.57 +/- 0.06 microg x kg(-1) x h(-1) (range 0.48-0.69). The imaging procedures were completed without difficulty. No patient required additional bolus administrations or changes in the infusion rate. The duration of the dexmedetomidine infusion ranged from 30 to 50 min. The mean decrease in heart rate was 13.6 +/- 5.1 b x min(-1) (14.3 +/- 5.0% from baseline; P = 0.02), the mean decrease in systolic blood pressure was 26.4 +/- 15.2 mmHg (24.6 +/- 12.4% decrease from baseline; P = 0.004), and the mean decrease in respiratory rate was 1.4 +/- 1.5 min(-1) (7.5 +/- 7.9% decrease from baseline; P = NS). P(E)CO2 exceeded 6.5 kPa (50 mmHg) in one patient [maximum 6.6 kPa (51 mmHg)] with a maximum value of 6.0 +/- 0.4 kPa (46 +/- 3 mmHg). Oxygen saturation decreased from 98 +/- 1 to 95 +/- 1%; P = 0.001. No patient developed hypoxemia (oxygen saturation less than 90%). Mean time to recovery to baseline status was 112.5 +/- 50.6 min and time to discharge was 173.8 +/- 83.8 min. CONCLUSIONS: Our preliminary experience suggests that dexmedetomidine may be an effective agent for procedural sedation during radiological imaging. Its potential application in this setting is discussed and other reports regarding its use in pediatric patients are reviewed.     

Intrathecal clonidine decreases propofol sedation requirements during spinal anesthesia in infants

Background: Propofol is a popular agent for providing procedural sedation in pediatric population during lumbar puncture and spinal anesthesia. Adjuvants like clonidine and fentanyl are administered intrathecally to prolong the duration of spinal anesthesia and to provide postoperative analgesia. We studied the propofol requirement after intrathecal administration of clonidine or fentanyl in infants undergoing lower abdominal surgeries. Methods: Sixty‐five ASA I infants undergoing elective lower abdominal surgery under spinal anesthesia were assigned into four groups in this prospective randomized double‐blinded study. Group B received bupivacaine based on body weight (<5 kg = 0.5 mg·kg⁻¹; 5–10 kg = 0.4 mg·kg⁻¹). Group BC received 1 μg·kg⁻¹ of clonidine with bupivacaine, group BF received 1 μg·kg⁻¹ of fentanyl with bupivacaine, and patients in group BCF received 1 μg·kg⁻¹ each of clonidine and fentanyl with bupivacaine. A bolus of 2–3 mg·kg⁻¹ of propofol bolus was administered for lumbar puncture. Sedation was assessed using a six‐point sedation score (0–5) and a five‐point reactivity score (0–4) which was based on a behavioral score. After achieving a sedation and reactivity score of 3–4, the patients were placed lateral in knee chest position and lumbar puncture performed and test drug administered. Further intraoperative sedation was maintained with an infusion of 25–50 μg·kg⁻¹·min⁻¹ of propofol infusion. Results: The mean ± sd infusion requirement of propofol decreased from 35.5 ± 4.5 in group B to 33.4 ± 5.4 μg·kg⁻¹·min⁻¹ in group BF and further decreased to 16.7 ± 6.2 μg·kg⁻¹·min⁻¹ and 14.8 ± 4.9 μg·kg⁻¹·min⁻¹ in group BC and BCF, respectively. There were no statistically significant differences between BC and BCF groups. The mean sedation and reactivity scores were higher in groups BC and BCF when compared to groups B and BF. Conclusion: Our study show that the requirement of propofol sedation reduces with intrathecal adjuvants. The reduction was significant with the addition of clonidine and clonidine–fentanyl combination as opposed to bupivacaine alone or with fentanyl. There was no significant difference in propofol infusion requirement with the use of bupivacaine alone or with fentanyl.     

Intravenous ketamine for prevention of severe hypotension during spinal anaesthesia

Spinal block causes paralysis of preganglionic sympathetic fibres, while ketamine induces activation of the sympathetic nervous system. Hypotension is a frequent complication during spinal anaesthesia and is associated with an increased risk of postoperative mortality. The aim of our study was to compare circulatory changes in patients who received either fentanyl or ketamine during spinal anaesthesia. Thirty patients (ASA I-III) scheduled to undergo spinal anaesthesia for osteosynthesis of hip fractures were allocated to receive either ketamine or fentanyl intravenously during the procedure. Immediately before anaesthesia, 7 ml/kg BW of an isotonic NaCl solution was administered i.v. Patients received either fentanyl 1.5 mg/kg BW i.v. before anaesthesia, or ketamine 0.7 mg/kg BW i.v. before anaesthesia, and 0.35 mg/kg BW 15 and 30 min after the first dose. No prophylactic vasopressor was used. During the first 40 min of anaesthesia a fluid load of 14 ml/kg BW was given i.v. If the mean arterial pressure (MAP) fell more than 20%, the infusion rate was increased. If the reduction in MAP exceeded 33% or if the systolic pressure decreased to less than 80 mmHg, patients were registered as haemodynamically unstable. In both groups the spinal anaesthesia caused a reduction in MAP. The MAP was lower in the fentanyl group than in the ketamine group at all times. In the fentanyl group six subjects developed a haemodynamically unstable condition, while only one subject in the ketamine group was registered as such (P less than 0.05). There was no significant change in heart rate in either group. We conclude that during spinal anaesthesia patients can in part be kept haemodynamically stable by intravenous administration of ketamine.