Reevaluation of Rectal Ketamine Premedication in Children: Comparison with Rectal Midazolam

Background: Results of previous studies of rectal ketamine as a pediatric premedication are clouded because of lack of dose-response relation, inappropriate time of assessing sedative effects, and previous administration or coadministration of benzodiazepines. Therefore, the authors reevaluated the efficacy of rectally administered ketamine in comparison with 1 mg/kg rectal midazolam.

Methods: Sixty-six infants and children (age, 7-61 months) who were American Society of Anesthesiologists physical status I and who were undergoing minor surgeries as in-patients were randomized to receive 5 mg/kg ketamine (n = 16), 7 mg/kg ketamine (n = 16), 10 mg/kg ketamine (n = 17), or 1 mg/kg midazolam (n = 17) via rectum. A blinded observer scored sedation 45 min and 15 min after administration of ketamine and midazolam, respectively, when children were separated from parent(s) for inhalational induction. All children underwent standardized general anesthesia with sevoflurane, nitrous oxide, and oxygen with endotracheal intubation. Blood pressure, heart rate, and oxyhemoglobin saturation were determined before, during, and after anesthesia. Postoperative recovery characteristics and incidence of adverse reactions were also assessed.

Results: Most children (88%) who received rectally 10 mg/kg ketamine or 1 mg/kg midazolam separated easily from their parents compared with those (31%) who received 7 or 5 mg/kg rectal ketamine (P < 0.05). Similarly, more children who received 10 mg/kg ketamine or 1 mg/kg midazolam underwent mask induction without struggling or crying compared with those who received 7 or 5 mg/kg ketamine (P < 0.05). There were no clinically significant changes in blood pressure, heart rate, and oxyhemoglobin saturation after administration of either drug. Immediately after surgery, more children receiving midazolam or 5 mg/kg ketamine were agitated compared with 7 or 10 mg/kg ketamine. Ketamine, 7 and 10 mg/kg, provided postoperative analgesia, but the largest dose of ketamine was associated with delayed emergence from general anesthesia.     

Midazolam and ketamine for rectal premedication and induction of anesthesia in children

Fifteen healthy children 2-10 years old and scheduled for elective surgery, received midazolam 0.35 mg/kg body weight and atropine 0.025 mg/kg as rectal premedication about 35 min before the induction of anesthesia. The induction itself was carried out in a separate and quiet room next to the operating theatre by rectal administration of ketamine 10 mg/kg and midazolam 0.2 mg/kg. With the children breathing spontaneously, anesthesia was maintained by repetitive i.v. bolus injections of ketamine. The sedative and anticholinergic effects of the premedication were satisfactory. Induction of anesthesia was smooth. Consciousness was lost after 9-15 (mean 13) min. No significant adverse effects on hemodynamics or respiration were noted. Recovery from anesthesia was uneventful. No cases of rectal irritation or unpleasant dreams were reported. Post-operative analgesia was good. In conclusion, rectal administration of midazolam and atropine for premedication, followed by ketamine and midazolam for the induction of anesthesia, proved to be a pleasant, safe, and reliable method in pediatric anesthesia.     

Pharmacokinetic studies following intravenous and rectal administration of midazolam in children

In children, rectal midazolam is being used increasingly for premedication, as this substance is reported to have a short half-life and rapid action. Above all it is the only known diazepam derivative with a good correlation of plasma concentration and clinical action despite its receptor binding capacity. As pharmacokinetic data in children are lacking and different dose regimens for rectal premedication exist, we studied plasma concentrations in 3 groups of children. METHODS. After obtaining informed parental consent we studied children aged 3-7 years (15-30 kg body weight) ASA I status scheduled for minor elective surgery. Group 1 (n = 6) received 0.1 mg/kg midazolam i.v. for induction of anesthesia. Group 2 (n = 10) was premedicated with 0.35 mg/kg midazolam, instilled just behind the anal sphincter; group 3 (n = 5) received 0.5 mg/kg midazolam rectally. Blood samples were drawn up to 120 min after application. The anesthesia technique consisted of N2O/O2, enflurane, intubation and the use of muscle relaxants, if necessary. Midazolam plasma levels were measured by HPLC. RESULTS. There were no differences with respect to age or body weight. Group 1: half-life in children was shorter than in adults, Vdss was smaller and clearance identical. Group 2: Rectal midazolam 0.35 mg/kg has a remarkably short onset of action with peak plasma concentrations (71 ng/ml) in the range of sedative levels in adults occurring in 7.5 min. After 2 h they reached levels of 30 ng/ml. Group 3 patients had peak levels of midazolam of 246 ng/ml after 12.5 min, falling to an average concentration of 120 ng/ml after 2 h. The bioavailability of rectal midazolam, comparing the area under the median curves, is 4.7% in group 2 and 16.1% in group 3. CONCLUSIONS: The pharmacokinetics of midazolam in our patients showed a shorter half-life, probably due to the higher hepatic clearance based on the high CI in children, as midazolam is known to have a first-pass effect of 30-70%. The increased metabolic transformation and the smaller amount of fatty tissue accounts for the smaller Vdss in children compared to adults. Rectal midazolam has a remarkably short onset and especially in a dose of 0.5 mg/kg prolonged action due to ongoing resorption from the rectum as demonstrated by the clinically relevant plasma concentrations. This fact must be taken into consideration in the overall anesthesia management.(ABSTRACT TRUNCATED AT 400 WORDS)     

S(+)-ketamine for rectal premedication in children

Our purpose for this prospective, randomized, and double-blinded study was to evaluate the anesthetic efficacy of S(+)-ketamine, an enantiomer of racemic ketamine, compared with a combination of S(+)-ketamine and midazolam, and plain midazolam for rectal premedication in pediatric anesthesia. Sixty-two children, ASA physical status I and II, scheduled for minor surgery, were randomly assigned to be given rectally one of the following: 1.5 mg/kg preservative-free S(+)-ketamine, a combination of 0.75 mg/kg preservative-free S(+)-ketamine and 0.75 mg/kg midazolam, or 0.75 mg/kg midazolam. Preoperative anesthetic efficacy was graded during a period of 20 min by using a five-point scale from 1 = awake to 5 = asleep. Tolerance during anesthesia induction via face mask was graded by using a four-point scale from 1 = very good to 4 = bad. A sufficient anesthetic level (> or = 3) after rectal premedication was reached in 86% in midazolam/S(+)-ketamine premedicated children, in 75% in midazolam premedicated children, but only in 30% in S(+)-ketamine premedicated children (P < 0.05 S(+)-ketamine versus midazolam/S(+)-ketamine and midazolam groups). The incidence of side effects after rectal premedication was rare. Whereas the mask acceptance score was comparable in the three study groups, a 25% rate of complications during anesthesia induction via face was observed in the S(+)-ketamine study group (P < 0.05 versus other study groups). Our conclusions are that S(+)-ketamine for rectal premedication in the dose we chose shows a poor anesthetic effect and a frequent incidence of side effects during induction of anesthesia via face mask compared with the combination of midazolam/S(+)-ketamine and plain midazolam. Dose-response studies of S(+)-ketamine for rectal premedication in pediatric anesthesia may be warranted.     

Preinduction of anesthesia in children with rectally administered midazolam

The authors evaluated the efficacy of rectally administered midazolam for preinduction (i.e., premedication/induction) of anesthesia in 67 pediatric patients, ASA physical status 1 or 2, undergoing a variety of elective surgical procedures. In phase 1, 41 children weighing 12 +/- 3 kg (range 7-20 kg) and 31 +/- 16 months (range 8-67 months) of age (mean +/- SD) received midazolam, 0.4-5.0 mg.kg-1, in an attempt to produce unconsciousness. Only one child lost consciousness (4.5 mg.kg-1). However, at all doses, inhalational induction of anesthesia was facilitated because children were tranquil and calmly separated from their parent(s). There were no clinically significant changes in arterial blood pressure, heart rate, oxyhemoglobin saturation, and end-tidal carbon dioxide concentration, 10 min after drug administration. In phase 2, 26 children weighing 17 +/- 4 kg (range 10-26 kg) and 44 +/- 19 months (range 17-84 months) months of age undergoing tonsil and/or adenoid surgery were studied to determine the optimal sedative dose of rectally administered midazolam. Patients received 0.3, 1.0, 2.0, or 3.0 mg.kg-1 of midazolam in a randomized, double-blind fashion. One third (3 of 9) of patients receiving 0.3 mg.kg-1 struggled during mask induction. All patients receiving greater than or equal to 1.0 mg.kg-1 were adequately sedated (P less than 0.008). Discharge from the postanesthesia care unit (PACU), however, was delayed (greater than 60 min) in children receiving greater than or equal to 2.0 mg.kg-1 (P less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum potassium after enflurane-succinylcholine induction of anesthesia in children receiving rectal midazolam as premedication.

The administration of succinylcholine causes an increase in serum potassium (K+) concentrations in healthy patients. The purpose of this study was to investigate serum K+ changes following intravenous succinylcholine in children and to evaluate the effect of rectal midazolam pretreatment on these changes. Forty healthy children between the ages of 2 and 7 yr, and who were to undergo oral surgical procedures under general anesthesia were randomly assigned to receive either placebo (saline) or 0.25, 0.35, or 0.45 mg/kg midazolam administered rectally as premedication 30 min before induction of inhalational anesthesia. Blood was drawn after induction with enflurane and at 1, 2, 3, 4, and 5 min after administration of 1 mg/kg succinylcholine to determine changes in serum K+. Although the results indicate a significant increase in serum K+ after succinylcholine in all groups, midazolam pretreatment failed to cause any observable attenuation in the hyperkalemic response.     

Effectiveness of preoperative sedation with rectal midazolam, ketamine, or their combination in young children.

To determine which of three types of rectal sedation was most effective preoperatively in facilitating parental separation and intravenous cannulation in young children, 100 children 3.0 +/- 1.7 (mean +/- SD) yr of age were randomly assigned to four equal groups. One group (M-K-A) received rectal midazolam (0.5 mg/kg), ketamine (3 mg/kg), and atropine (0.02 mg/kg). The other sedation groups received the same doses of midazolam and atropine (M-A) or ketamine and atropine (K-A) alone, and the control group (A) received only rectal atropine. Most children in either the M-K-A (100%) or M-A (92%) groups separated easily from their parents without struggling or crying, significantly more than in the K-A (60%) or A (64%) groups. However, more children in the M-K-A group (44%) were asleep during separation than in the M-A group (8%; P < 0.05). Only 20% of the children in the M-A or M-K-A groups cried during intravenous catheter placement, significantly less than in the K-A (56%) or A (92%) groups. Intravenous catheter placement was also successful significantly more often in the M-A (80%) and M-K-A (84%) groups than in the K-A (48%) or A (40%) groups. Complications were similar among the groups, but there was evidence that midazolam prolonged recovery time in some patients. Rectal midazolam with or without ketamine is a useful technique when intravenous catheter placement before induction of anesthesia is desired.     

Rectal premedication in children

Two hundred and eight healthy children who were to undergo minor elective surgery during halothane, nitrous oxide, oxygen anaesthesia were studied in a double blind investigation to evaluate the sedative and anticholinergic effects of two rectal premedications. Group I received diazepam 0.75 mg/kg rectally; Group II received a mixture of diazepam 0.5 mg/kg, morphine 0.15 mg/kg and hyoscine 0.01 mg/kg rectally. No significant difference was found between the two groups in sedative or anticholinergic effects during induction of anaesthesia or in the postoperative period. No adverse effects were seen.     

A comparison of ketamine and lidocaine spray with propofol for the insertion of laryngeal mask airway in children: a double-blinded randomized trial

The laryngeal mask airway (LMA) has been used successfully as both a ventilatory device and a conduit for tracheal intubation. In this double-blinded, randomized study, we examined whether pretreatment with lidocaine spray, ketamine anesthesia, and LMA insertion could be used as airway management that could maintain spontaneous breathing in children. After IV premedication with midazolam 0.05 mg/kg and glycopyrrolate 0.005 mg/kg, 90 patients were randomly allocated to 1 of 2 main groups for the administration of either propofol or ketamine: 40 patients received 2.5, 3.0, 3.5, or 4.0 mg/kg of propofol IV (n = 10 each), whereas 50 patients received 2.0, 2.5, 3.0, 3.5, or 4.0 mg/kg of ketamine IV (n = 10 each). Only in the ketamine group was lidocaine spray applied to the oropharynx 1 min before anesthesia induction. After injection of the designated drug, self-respiration, airway obstruction, and jaw relaxation were checked. Self-respiration, laryngospasm coughing, gagging, swallowing, biting or tongue movements, secretions, and head or limb movements after LMA insertion were graded. All variables were graded as satisfactory, acceptable, or unsatisfactory. The overall result was considered satisfactory if all criteria were satisfactory; acceptable if all were better than acceptable, but at least one acceptable criterion was included; and unsatisfactory if at least one criterion was unsatisfactory. Overall satisfactory or acceptable results in every patient were achieved only in the ketamine 3.0 or 3.5 mg/kg subgroups. No propofol dose was completely satisfactory; most cases involved apnea or airway obstruction. Ketamine and lidocaine spray were appropriate for LMA insertion, which may be a safe method for management of difficult airway in children. IMPLICATIONS: Ketamine and lidocaine spray appear to be appropriate for laryngeal mask airway (LMA) insertion in children. Thus, apnea and airway obstruction, the two most serious and frequent complications of propofol, can be avoided during LMA insertion.     

Efficacy and safety of premedication with oral ketamine for day-case adenoidectomy compared with rectal diazepam/diclofenac and EMLA

BACKGROUND: Because of its pain-attenuating and sedative properties oral ketamine has been used as premedication in children and adults. We wanted to compare in children scheduled for adenoidectomy safety and efficacy of oral ketamine with a premedication that causes similar preoperative sedation and relief of pain at the venepuncture site. We also evaluated the effect of i.v. glycopyrrolate added to these combinations. METHODS: One hundred children between 10 and 15 kg of body weight scheduled for day-case adenoidectomy were randomly assigned to one of four groups: groups DG and DS received diclofenac 12.5 mg and diazepam 0.5 mg/kg rectally, EMLA cream at the venepuncture site, and placebo orally; groups KG and KS received ketamine 6.0 mg/kg orally, placebo cream at the puncture site, and placebo rectally; additionally, groups DG and KG received glycopyrrolate 5 microg/kg, and groups DS and KS received placebo intravenously. We recorded perioperatively scores (open scale 1-9) for stridor, sedation, bleeding, nausea, pain, heart rate, the need for analgesics and registered psychotomimesis and well-being at home. RESULTS: The children of the K-groups became more tearful during separation from their parents (P=0.0072). No other differences were found between the ketamine and diazepam/diclofenac groups before and after premedication until induction of anaesthesia. Oral ketamine produced unpleasant psychotomimesis in four out of 59 children. During the first 10 min postoperatively, the score for stridor was significantly higher in group KS than in the D-groups; stridor scores > or = 6 were seen in one child of the D-groups (DS) and in six children of the K-groups (n.s.), of whom three developed laryngospasm (one reintubation). Glycopyrrolate diminished salivation in all groups, but had no effect on stridor scores. Additionally, glycopyrrolate delayed the onset of eating at home. CONCLUSION: Premedication with racemic oral ketamine 6 mg/kg does not seem to be suitable for upper airway procedures. Addition of i.v. glycopyrrolate before the induction of anaesthesia significantly reduced the scores for salivation.     

Intranasal sufentanil/midazolam versus ketamine/midazolam for analgesia/sedation in the pediatric population prior to undergoing multiple dental extractions under general anesthesia: a prospective, double-blind, randomized comparison

This article details a double-blind, randomized study evaluating the efficacy and safety of intranasal sufentanil and intranasal midazolam (S/M) when compared with intranasal ketamine and intranasal midazolam (K/M) for sedation and analgesia in pediatric patients undergoing dental surgery. Fifty healthy ASA status 1 children aged 5-7 years, weighing 15-20 kg, and having 6 or more teeth extracted, were randomly allocated to 2 groups of 25 patients each (n = 50). In the S/M group, 25 children received intranasal sufentanil 20 microg, and intranasal midazolam 0.3 mg/kg 20 minutes before the induction of anesthesia. In the K/M group, 25 children received intranasal ketamine 5 mg/kg and intranasal midazolam 0.3 mg/kg 20 minutes before the induction of anesthesia. Sevoflurane in nitrous oxide and oxygen was used for induction and maintenance of anesthesia. This study demonstrated the safety and efficacy of both methods with ease of administration, combined with a rapid onset of action. Both groups were equally sedated. A smooth mask induction of anesthesia was experienced in the majority of children. Effective postoperative analgesia for multiple dental extractions was provided. The intranasal administration of drugs for sedation and analgesia has some promising features in preschool children undergoing multiple dental extractions.     

Arterial oxygen saturation in children receiving rectal midazolam as premedication for oral surgical procedures

Eighty healthy children, between the ages of 2 and 7 years, undergoing dental procedures were monitored with a pulse oximeter for changes in arterial oxygen saturation. The children were randomly allocated into 4 groups in this double-blind study. Three groups received rectal midazolam, and the other group a placebo (saline) as premedication 30 min prior to induction of anesthesia. Group A children received midazolam 0.25 mg/kg, Group B 0.35 mg/kg and Group C 0.45 mg/kg. The results from this trial show no statistical significant difference between the treatment groups as to the effect on either systolic or diastolic blood pressure, respiration, or pulse rates at either pre- or post-sedation levels. However, the oxygen saturation levels for groups B and C differed significantly from those of the placebo groups 30 minutes after premedication (P = 0.0259).     

Rectal administration of midazolam versus diazepam for preanesthetic sedation in children

Sixty children were included in the trial. Each subject received midazolam 0.4 mg/kg body weight of diazepam 0.75 mg/kg body weight rectally in a double-blind randomized order. The degree of sedation of the children was assessed on arrival in the operating unit and during the induction of anesthesia. Adequate sedation on arrival in the operating unit and during induction of anesthesia was obtained in 84% and 67%, respectively, following administration of midazolam compared with 80% and 70% in the diazepam group. No side effects were noted. It is concluded that rectally administered midazolam 0.4 mg/kg is comparable to diazepam 0.75 mg/kg with respect to preanesthetic sedation in children.     

Oral midazolam in children: effect of time and adjunctive therapy.

The purpose of this study was to determine the influence of timing and concomitant administration of atropine and/or meperidine on the perioperative effects of oral midazolam in children. In 154 healthy children, 1-8 yr old, we studied six oral preanesthetic medication regimens according to a randomized, double-blind protocol. Group A (placebo) received 5 mL of apple juice. The other five groups received medication with apple juice to a total volume of 5 mL, 20-60 min before induction of anesthesia. Group B received atropine (0.02 mg/kg); group C received midazolam (0.5 mg/kg); group D received midazolam (0.5 mg/kg) and atropine (0.02 mg/kg); group E received meperidine (1.5 mg/kg) and atropine (0.02 mg/kg); and group F received meperidine (1.5 mg/kg), atropine (0.02 mg/kg), and midazolam (0.5 mg/kg). The sedative effect of midazolam was maximal 30 min after oral administration. Ninety-five percent of the children who were separated from their parents within 45 min after oral midazolam administration (with or without atropine) had satisfactory separation scores (vs 66% of those separated after 45 min; P less than 0.02). Midazolam-treated patients were more cooperative with a mask induction of anesthesia compared with non-midazolam-treated children (83% vs 56%). Neither atropine nor meperidine appeared to significantly improve the effectiveness of oral midazolam. No preoperative changes in heart rate, respiratory rate, or hemoglobin oxygen saturation were noted in any of the treatment groups. Finally, oral midazolam did not prolong recovery even after outpatient procedures lasting less than 30 min. In conclusion, midazolam (0.5 mg/kg) given orally 30-45 min before induction of anesthesia is safe and effective without delaying recovery after ambulatory surgery.     

Pre-hospital use of ketamine in paediatric trauma

Objectives: To describe the use of ketamine in children by a pre-hospital physician-based service.
Methods: A five and a half year retrospective database review of all patients aged <16 years who were attended by London's Helicopter Emergency Medical Service and given ketamine.
Results: One hundred and sixty-four children met the inclusion criteria. The median age was 10 years (range 0–15 years). One hundred and four (63%) had a Glasgow Coma Scale (GCS) of 15 and 153 (93%) had a GCS>8 before administration of ketamine. Patients received from 2 to 150 mg ketamine IV (mean=1.0 mg/kg) and 112 (68%) received concomitant midazolam (0.5–18 mg, mean=0.1 mg/kg). One hundred and forty-one (86%) received ketamine intravenously and 23 (14%) intramuscularly. Only 12 patients (7%) were trapped. The most common mechanisms of injury in those who received ketamine were road traffic collisions, burns and falls.
Conclusion: The safe delivery of adequate analgesia and appropriate sedation is a priority in paediatric pre-hospital care. Ketamine was predominantly used in awake non-trapped patients with blunt trauma for procedural sedation and analgesia. Detailed database searches did not demonstrate loss of airway, oxygen desaturation or clinically significant emergence reactions after ketamine administration. This study failed to demonstrate any major side effects of the drug and reassured us that the safety profile of the drug in this environment is likely to be satisfactory. The use of ketamine in trapped children was rare.     

Dexmedetomidine Premedication Attenuates Ketamine-induced Cardiostimulatory Effects and Postanesthetic Delirium

Background: Dexmedetomidine is a new potent and highly selective alpha2 -adrenoceptor agonist with sedative-hypnotic and anesthetic sparing properties. Because of its sympathoinhibitory activity, it may prove useful in balancing the cardiostimulalory effects and attenuating the adverse central nervous system effects of ketamine.

Methods: A double-blind, randomized and comparative parallel-group study design was employed in 40 volunteers with ASA physical status 1 who were scheduled for elective superficial surgery under ketamine anesthesia. Dexmedetomidine (2.5 micro gram/kg, n = 20) or midazolam (0.07 mg/kg, n = 20) was administered intramuscularly 45 min before induction of anesthesia. Anesthesia was induced with 2 mg/kg ketamine intravenously, and muscle relaxation was achieved with vecuronium. After tracheal intubation, anesthesia was maintained with nitrous oxide/oxygen (2:1) and additional 1 mg/kg intravenous ketamine boluses according t clinical and cardiovascular criteria. Hypotension and bradycardia were treated by increasing the intravenous infusion rate of crystalloids and intravenous atropine, respectively. Sedative and anxiolytic properties, intra- and postoperative drug requirements, psychomotor and cognitive impairments, and cardiovascular effects were compared between the two groups.

Results: Dexmedetomidine and midazolam proved to have equal sedative and anxiolytic effects after intramuscular administration, but dexmedetomidine induced significantly less preoperative psychomotor impairment and less anterograde amnesia than did midazolam. Compared to midazolam, dexmedetomidine decreased the need for intraoperative ketamine and was more effective in reducing ketamine-induced adverse central nervous system effects. Dexmedetomidine also was superior to midazolam in attenuating the hemodynamic responses to intubation and the cardiostimulatory effects of ketamine in general, but it increased the incidence of intra and postoperative bradycardia.     

Better acceptance of measures for induction of anesthesia after rectal premedication with midazolam in children. Comparison of results of an open and placebo-controlled study

The rectal administration of midazolam for premedication of children before induction of anesthesia by mask was investigated in two clinical studies. In 62 children aged between 2 and 10 years, midazolam was given by open design at various dosages (0.15 mg.kg-1, 0.25 mg.kg-1, 0.30 mg.kg-1, 0.35 mg.kg-1, 0.40 mg.kg-1) to evaluate the most effective dose for optimal acceptance of the mask and gas mixture. An additional 40 children between 3 and 9 years received 0.2 mg midazolam.kg-1 body weight or placebo in a double-blind design to estimate the lower limit of efficacy of midazolam. All children were classified as ASA I and had to undergo a surgical procedure. Within the two studies the children were not different with respect to their general data, age, weight, and sex. In both studies more boys than girls were included. Parameters of efficacy were the degree of sedation before and at 10, 20, and 30 min after midazolam as well as acceptance of the mask and the gas mixture at induction of anesthesia. In all groups, including placebo, a sedative and tranquilizing effect of the premedication was found. The rectal administration of 0.35-0.4 mg midazolam.kg-1 is most suitable for the preoperative medication of children between 2 and 10 years. Due to the degree of sedation and the relief of anxiety toward the surroundings and the operation, the induction of anesthesia is optimally accepted by the child. In contrast, the effect of a dose around 0.2 mg midazolam.kg-1 body weight is not much different from that of placebo and is not sufficient for effective premedication.     

Critical aspects of an outside evaluation of postoperative pain in infants. A placebo-controlled double-blind study of the question of the reliability and validity of the measurement system

Postoperative analgesia in infants and young children is a topic of growing interest in pediatric anesthesia. Two systems measuring postoperative pain in this group of patients have been offered recently: CHEOPS (Childrens Hospital of Eastern Ontario Pain Scale) by McGrath et al. and OPS (Objective Pain Scale) by Hannallah et al. and Broadman et al. [3, 7, 8]. Both systems are economical and not reactive, but their validity is not satisfying. The validity of CHEOPS is based on the statements of experienced nurses, using the method of convergent validation by an expert's assertion. Hannallah and Broadman et al. judged the validity of their objective pain scale for infants and young children by statements of juveniles between 13 and 18 years of age. McGrath et al. accepted the item of spontaneous verbal communication as useful in the CHEOPS, although no such verbal comment occurred in their study on interrater and inter-item correlations. The aim of the present study was to evaluate the statistical qualification of items for measurements of the intensity of postoperative pain in young children and to investigate some aspects of their validity. MATERIAL AND METHODS. The study was performed in 54 children of ASA groups I and II aged 29.2 +/- 10.7 months. They were included in the study if they were pain-free before the operation and had no signs and symptoms of neurologic disease. The following operations were accepted: herniorrhapy, orchidopexy, circumcision, and umbilical herniorrhaphy. Premedication and general anesthesia were standardized. The patients were premedicated with midazolam 0.5 mg/kg rectally and subsequent intramuscular injections of ketamine 2.0 mg/kg with atropine 0.01 mg/kg. Anesthesia was induced and maintained by inhalation of oxygen/nitrous oxide and halothane (FiO2 0.3). All children were intubated and ventilation was controlled during the operation. After the operation and under steady-state anesthesia with 0.5 vol.% halothane and spontaneous respiration, the children received either nalbuphine 0.1 mg/kg, piritramide 0.1 mg/kg, or placebo in a randomized and double-blind manner. Respiratory and circulatory parameters were recorded for 15 min before anesthesia was discontinued. Five minutes after halothane had been discontinued the first measurement of the childrens' behavior was started with four subsequent measurements at fixed time intervals of 15 min. The measuring system was based on the six items of CHEOPS complemented by five items related to the waking state because it was assumed that the waking state generally modulates the child's ability to demonstrate pain. The design of the study was accepted by the ethic committee with the provision that neither a sedative nor an analgesic drug should be withheld from any child if indicated. Therefore, all children who seemed to feel discomfort according to the subjective impression of the anesthetist received midazolam intraveneously to a maximal dose of 2 mg. All the behavioral data were included in a factor analysis (principal components)...     

Ketamine

Ketamine is an intravenous drug with special properties that make it the only agent that presently serves as anesthetic, sedative, amnesiac and analgesic. Although it is sometimes forgotten, ketamine is still considered a viable drug. Water soluble, stable and non-irritant when administered intravenously, ketamine has rapid onset after intravenous injection and provides acceptable anesthesia when administered in continuous infusion. There properties make ketamine useful for total intravenous anesthesia. Both propofol and midazolam are effective in reducing ketamine's adverse side effects. Administered in children by oral, nasal, rectal and intramuscular routes, ketamine allows for gentle anesthetic induction. It can also serve as an adjuvant in regional anesthesia to supplement analgesia. In adults ketamine is most often used for major surgery, particularly in the elderly or in high risk patients who are in shock, severely dehydrated or hemodynamically unstable, or in obstetric patients with hypovolemia or hemorrhage. It is probably the anesthetic of choice for patients with hyperreactive airways. Ketamine's strong analgesic effect at subanesthetic doses allows it to be used as an analgesic during postoperative intensive care or as an analgesic-plus-sedative for patients receiving mechanical ventilation. Interest in using ketamine at low doses for cancer and non-cancer patients with chronic pain has grown recently.     

Comparative evaluation of midazolam and ketamine with midazolam alone as oral premedication

BACKGROUND: Oral premedication with midazolam and ketamine is widely used in pediatric anesthesia to reduce emotional trauma and ensure smooth induction. However, various dosing regimens when used alone or in combination have variable efficacy and side effect profile. The aim of our study was to investigate and compare the efficacy of oral midazolam alone with a low-dose combination of oral midazolam and ketamine. METHODS: We performed a prospective randomized double-blind study in 100 children who were randomly allocated into two groups. Group M received 0.5 mg.kg(-1) oral midazolam and group MK received 0.25 mg.kg(-1) oral midazolam with 2.5 mg.kg(-1) oral ketamine. The preoperative sedation score, ease of parental separation and ease of mask acceptance were evaluated on a 4-point scale. The time to recovery from anesthesia and to achieve satisfactory Aldrete score was also noted. RESULTS: Uniform and acceptable sedation scores were seen in both the groups (group M 95.9%; group MK 97.96%), without any serious side effects. However, the combination offered significantly more children in an awake, calm and quiet state, who were easily separated from their parents (73.46% in MK vs 41% in group M). The induction scores were comparable between the groups. The recovery room characteristics and time to achieve satisfactory Aldrete score were also comparable between the two groups. CONCLUSIONS: Oral midazolam alone and a combination of midazolam with ketamine provide equally effective anxiolysis and separation characteristics. However, the combination provided more children in an awake, calm and quiet state who could be separated easily from parents.