Comparing caudal and intravenous ketamine for supplementation of analgesia after Salter innominate osteotomy
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- Amiri, H.R., Espandar, R. & Sanatkar, M. J Child Orthop (2012) 6: 479. doi:10.1007/s11832-012-0452-9
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Previous studies claim that caudal administration of ketamine causes effective analgesia. The aim of this study was to assess the clinical effectiveness of ketamine after caudal or intravascular administration in pediatric patients that underwent orthopedic surgery to distinguish between local and systemic analgesia.
After the induction of general anesthesia, 36 patients, aged 18 months to 10 years, assigned to undergo orthopedic surgery, received a caudal injection of bupivacaine and were randomly blinded into two groups: one group received 1 mg/kg S(+)-ketamine as the caudal group and the other group received 1 mg/kg S(+)-ketamine as the intravascular group. Postsurgical measurements included the effectiveness of postsurgical analgesia, which was assessed by using the observational pain scale (OPS), duration of analgesia, sedation score, and hemodynamic and respiratory monitoring.
The mean time to first analgesia was clearly longer in the caudal ketamine group (13.35 h) than in the intravenous ketamine (9.93 h) group (P < 0.01). During the 24-h observation time, fewer children asked for additional analgesic drugs in the caudal group (8 of 18, 44.4 %) than in the intravenous group (12 of 18, 66.6 %; P = 0.01). The times to first micturation and spontaneous leg movements and the incidence of nausea and vomiting were similar in the two groups. The OPS and sedation scores after operation showed no obvious differences between the groups at any time.
Although caudal ketamine provides good postsurgical analgesia due to its potential neurotoxicity and only small clinical differences with intravenous ketamine, the administration of intravenous ketamine might be a reasonable option to potentially extend the postsurgical analgesic effect of the caudal administration of local anesthetics in children undergoing Salter osteotomy.
KeywordsSalter innominate osteotomyCaudal analgesiaKetaminePediatrics
Caudal analgesia is widely used in pediatric operations where the surgical site is subumbilical . The most significant disadvantage of local anesthesia is its short duration due to single administration. To overcome this limitation, certain drugs are suggested in combination with the local anesthetic agent [2–4]. Caudal ketamine has been shown to prolong the duration of postsurgical analgesia in children . The analgesic effect and effectiveness of caudal epidural ketamine is probably due to its interaction with the glutamate N-methyl-d-aspartate (NMDA) receptors or opioid receptors  on the spinal cord. However, we cannot rule out the supraspinal effect of ketamine from systemic resorption. Subanesthetic intravenous doses of ketamine were used as an adjunct to systemic opioid analgesia without side effects [7, 8]. The aim of this study was to compare the postoperative analgesic efficacy of low-dose S(+)-ketamine administered either caudally or intravenously to supplement caudally administered plain bupivacaine in children undergoing Salter innominate osteotomy.
The modified observational pain/discomfort scale (OPS)
Suffering from pain, another complaint
Variable, taut, upright
Stretched, continuous movement
Wilson sedation scale
Degree of sedation
Fully awake and oriented
Eyes closed but rousable to command
Eyes closed but rousable to mild physical stimulation (earlobe tug)
Eyes closed but unrousable to mild physical stimulation
Patient characteristics in each group
12.2 ± 6.1
12 ± 4.8
88 ± 10.8
86 ± 13.6
Duration of surgery (min)
48.2 ± 12.2
45.4 ± 14.4
The intraoperative and postoperative characteristics of both groups
Average mean arterial blood pressure (mmHg)
68 ± 12
69 ± 18
Mean heart rate
95 ± 28
97 ± 24
Mean duration of analgesic effect (h)
13.35 ± 1.2
9.93 ± 1.6
Asked for additional analgesic drugs
8 (44.4 %)
12 (66.6 %)
Time to first micturation (h)
Time to spontaneous leg movement (h)
Nausea and vomiting
Adverse psychological effects
Caudal analgesia along with general anesthesia is a very popular regional technique for prolonged postoperative analgesia in different pediatric surgical procedures. Koinig et al.  showed that only 52 % of patients who underwent caudal block with ropivacaine maintained a sufficient level of analgesia for the first 24 h after operation. An attempt to overcome these problems was performed by combining local anesthetic agents with other drugs such as ketamine, opioids, and clonidine [14–16]. Ketamine added to bupivacaine in caudal analgesia as an adjuvant agent was shown to increase analgesia duration. Semple et al.  found that different doses of ketamine (0.25, 0.5, and 1 mg/kg) added to caudally applied bupivacaine (0.25 %) presented with analgesia durations of 7.9, 11, and 16.5 h, respectively. Previous studies showed that the postoperative analgesia duration of caudal ropivacaine (1 mg/kg 0.2 %) plus ketamine (0.25 mg/kg) was 12 h . De Negri et al. found an analgesia duration of 291 min with 2 mg/kg 0.2 % ropivacaine, which was increased to 701 min with 0.2 % ropivacaine combined with 0.5 mg/kg S-ketamine . The results of the present study indicate that S(+)-ketamine, when administered caudally, would prolong the duration of postsurgical analgesia and decrease the necessity for subsequent postsurgical analgesia more than intravenous S(+)-ketamine in children undergoing orthopedic operation. Ketamine may interact with antinociceptive spinal receptors. This effect might possibly be related to the drug concentration in the epidural tissue and not to that of the plasma. Ketamine, a derivative of phencyclidine, is an antagonist at NMDA receptors, which are found throughout the central nervous system, including the spinal cord, with a stereoselectivity regarding S(+)-ketamine . Ketamine also binds at μ opioid receptors and is apparently shown to be stereoselective for the S(+)-enantiomer . In our study, the hemodynamic variables were similar between the two groups. None of the patients in either group demonstrated hypotension or bradycardia. Ödeş et al.  also showed no hemodynamic changes after caudal 2 mg/kg 0.2 % ropivacaine plus 0.5 mg/kg ketamine. In our study, we did not encounter any respiratory depression. De Negri et al. reported no respiratory changes or depression after caudal 0.02 % ropivacaine and 0.2 % ropivacaine and S-ketamine mixture . Previous studies have shown that caudal ketamine reduced the incidence of motor block when added to the procedure after reducing the dosage of local anesthetic agent, but in our study, motor block scores revealed no significant differences in both groups. Similar to our results, none of the previous studies reported more sedation in patients who underwent caudal block with local anesthetic and ketamine compared to caudal block with only local anesthetic [21, 22].
The neurotoxic effects of ketamine after intrathecal administration were observed in animal studies  and after continuous intrathecal administration for the management of neuropathic cancer pain . Consequently, its administration in the epidural space has been seriously questioned recently .
The major limitation of our study was the lack of comparison with a control group without ketamine.
In conclusions, although fewer patients in the caudal ketamine group asked for additional analgesic drugs (P = 0.01) and more patients were pain free for a longer time postoperatively (P < 0.01), it did not result in any significant differences in OPS scores, sedation scores, hemodynamic change, respiratory depression, time to first micturation, and motor block scores in comparison to intravenous ketamine. In other words, according to the results, the use of caudal ketamine only resulted in a small clinical difference with intravenous ketamine. Due to the potential neurotoxic effects of the epidural administration of ketamine, the administration of intravenous ketamine might be a suitable alternative aiming to achieve a long-lasting analgesic effect after the caudal administration of bupivacaine.
Conflict of interest