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From the Departments of
*Anesthesiology,
Pediatrics, and
Family and Community Medicine of the University of Louisville and Kosair Childrens Hospital, Louisville, Kentucky
Address correspondence and reprint requests to Steve M. Auden, MD, Pediatric Anesthesia, N-65, Kosair Childrens Hospital, 231 E. Chestnut St., Louisville, KY, 40202. Address e-mail to sauden{at}aol.com
| Abstract |
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0.02) and in larger doses (P < 0.05) after IM DPT. Parental satisfaction ratings were higher (P < 0.005) and amnesia was more reliably obtained (P = 0.007) with PO ketamine/midazolam. Two patients needed airway support after the PO medication, as did two other patients when PO ketamine/midazolam was supplemented with IV propofol. Although PO ketamine/midazolam provided superior sedation and amnesia compared to IM DPT, this regimen may require the supervision of an anesthesiologist for safe use. Implications: Oral medication can be superior to IM injections for sedating children with congenital heart disease; however, the safety of all medications remains an issue.
| Introduction |
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IM DPT continues to be widely used and, at least lately, widely reviled. Major shortcomings of DPT include its painful route of administration, slow onset, prolonged effect, lack of reliable amnesia, and frequent occurrence of restlessness. Respiratory depression is common and respiratory arrest can occur (2), with two prospective series putting the incidence of serious to life-threatening complications at 4% (2,3). Respiratory depression often reflects excess sedation; however, deep sedation is not reliably achieved with DPT. Terndrup et al. (4) reported a 29% failure rate for emergency department procedures. Prolonged duration of sedation from DPT was also reported in the same study, in which 19 ± 15 h passed before return to normal behavior (4). These and other problems have led to calls for "rational and safe alternatives" (5), and the American Academy of Pediatrics Committee on Drugs has issued a critical "reappraisal of lytic cocktail" (6).
For some time, we had been using an oral (PO) combination of ketamine/midazolam as premedication for cardiac surgery in children. We had found the combination of ketamine/midazolam to be free of the negative side effects of ketamine alone (79) and to provide rapid onset of deep sedation with minimal, if any, hemodynamic or respiratory compromise (1011). Both components confer amnesia. Accordingly, we evaluated PO ketamine/midazolam as an alternative to IM DPT as the primary sedative for pediatric cardiac cath.
| Methods |
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On the day of the scheduled procedure, children came to the preoperative area. Before any medication was given, vital sign measurements were made including heart rate (HR) by electrocardiogram, mean blood pressure (BPM) by oscillotonometry, and SpO2 by pulse oximetry. These measurements were made by using a portable Escort® monitor (Medical Data Electronics, Arleta, CA) which remained with the patient and was used throughout the study. Respiratory rate (RR) was counted for a minimum of 15 s. An observational sedation scale was assessed (and later repeated as noted) by using a scale of awake, drowsy, or asleep. Any patient assessed as drowsy or asleep after drug administration was considered sedated. When possible, an echocardiogram was obtained (33 of 51 patients, with two studies later excluded for inadequate quality). Ventricular shortening fraction (SF) was determined by measurements of recorded echoes at a later date. SF was measured from a standard parasternal long-axis view.
After these assessments, IM injection was given to all patients, with time of the IM injection defined for study purposes as time zero. Acyanotic patients in the IM group received IM DPT at a dose of 2 mg/kg of meperidine and 1 mg/kg each of promethazine and chlorpromazine. Patients in the PO group received IM saline at time zero. The IM medication dose (and the volume of the IM placebo) was one-half for cyanotic patients, which is our common practice and reflects the usual practice elsewhere (1,12).
All patients received PO fluid at time = 15 min (i.e., 15 min after IM injection, to blind for the slower onset of IM DPT). Whereas the IM dosage was adjusted based on cyanosis versus acyanosis, the PO dosage was adjusted to give younger patients a larger dose (13,14). Children in the PO group who were
3 yr old received ketamine 10 mg/kg and midazolam 1 mg/kg. Children
4 yr old received ketamine 6 mg/kg and midazolam 0.6 mg/kg (1519). Children in the IM group received a placebo of the flavored vehicle only, volume adjusted by age. All drugs and placebos were given in double-blinded fashion. All randomization and drug/placebo dispensing was performed in the pharmacy and all other personnel were completely blinded. Patient acceptance of the IM and PO medications was rated on a three-tier observational scale of marked response versus moderate response versus minimal or no response (See Table 1).
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After securing IV access, patients were transported to the cardiac cath lab where the echocardiogram was repeated. Children were then separated from their parents and moved to the cardiac cath table where they were positioned, prepared, and draped. Local anesthetic was infiltrated over the femoral vessels to allow cannulation. At separation, positioning, and cannulation, patient response was once again assessed by using the three-tier observational scale described in Table 1. At positioning and cannulation and for the remainder of the procedure, the attending anesthesiologist administered additional sedative medication based on patient responses. In all cases, the additional medication was propofol 0.5 mg/kg given IV via pump over 30 s (21). The patient was observed for cardiorespiratory effects of propofol, and any 10% change in BPM or 6-point change in SpO2 was recorded. Doses of propofol were tracked, and when more than 10 boluses were used, it was at the anesthesiologists discretion to begin a propofol infusion at 100 mcg/kg/min. The infusion could be adjusted by 25 mcg/kg/min increments as needed.
Time spent in the recovery area was also noted. Our routine recovery discharge criteria were used to determine the stay.
After a minimum of 4 h on the floor, a final interview with patients and parents was conducted. Parents completed a visual analog scale as a measure of satisfaction with sedation. A 10-cm unmarked line labeled "failed sedation" at the left end [0] and "excellent sedation" at the right end [100] was presented. Parents marked their assessment, and these marks were later given a numeric value by ruler measurement. Children
4 yr old were questioned as to recall of IV placement or events in the cardiac cath lab. Any positive response was judged as failure to provide amnesia.
Statistical analysis was performed by using the Mann-Whitney U-test for non-Gaussian data and Students t-test or repeated measures analysis of variance for Gaussian data. Binomial data were analyzed by using the Pearson
2 or Fishers exact test, as appropriate. Statistical significance was defined as P
0.05.
| Results |
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2). Patients who received PO ketamine/midazolam tolerated IV placement, separation from parents, and femoral cannulation more readily than their counterparts in the IM group (Figure 1). Patients who had received IM DPT were more restless and tended to awaken and often became agitated with movement from stretcher, positioning, subcutaneous injection of local anesthetic, etc. Thirteen children in the IM group were noted to be agitated at one or more points as opposed to only two children in the PO group (P = 0.0048, Fishers exact test). There were no differences for onsets of sedation or sleep for cyanotic versus acyanotic children (P = 0.62 and 0.18, respectively, Mann-Whitney U-test).
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Supplemental analgesia and sedation with propofol were required by a higher percentage of patients in the IM group (See Table 2). This was true on transfer to the cardiac cath table (on arrival), on femoral cannulation, and throughout the procedure. The median number of doses of propofol in the IM group was one dose on arrival, two with cannulation, and six total. For the PO group, the median number of doses of propofol was zero both on arrival and cannulation, and one total (P = 0.046 arrival, 0.01 cannulation, 0.002 total; Mann-Whitney U-test). With bolus use of propofol, two patients (both in the IM group) had >10% decrease in BPM and two others (both in the PO group) had SpO2 decrease transiently, responding readily to jaw thrust.
Recovery data reflects 48 patients. Of the other three, one patient in the IM group went to the operating room, one patient in the PO group went to intensive care, and one patient received fentanyl in recovery for hypercyanotic episodes. Recovery room discharge was delayed in the IM group (See Table 2). Despite their longer stay in recovery, patients in the IM group were more sedated at time of discharge than those in the PO group (P = 0.001, Pearson
2).
Parental satisfaction was greater with the PO medication (See Table 2). In children
4 yr old, only one child in the PO group had recall (of IV placement). More than one-half of the patients in the IM group had recall of IV placement and/or the cardiac cath lab (See Table 2).
| Discussion |
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There are two interrelated problems with applying the results of this study to routine cardiac cath lab procedure: staffing and safety. Smith et al. (1) popularized their "ataractic mixture" for pediatric cardiologists who then monitored the patient, performed the procedure, and gave additional sedative medication as needed. This division of attention is no longer acceptable under modern sedation guidelines (24,25). In our study, each child had a pediatric anesthesiologist in attendance. Additional sedation, i.e., propofol, was given to maintain a level of sedation acceptable to both the cardiologist and the anesthesiologist. The quality of sedation, the supplemental use of propofol, and the ease of dealing with complications are all no doubt affected by the presence of an anesthesiologist. We found that supplemental use of propofol was less frequent in the PO group. This was true both as a percentage of patients requiring medication and as median number of doses required, and underscores the greater efficacy of PO ketamine/midazolam.
Secondly, our study population was too small to estimate safety or complication rate of either ketamine/midazolam or of supplemental propofol, however, minor complications did occur. By power analysis, if we accept a DPT rate of serious complications as 4%, and seek to differentiate this from a 10% rate of problems with our PO combination, we would need to study 300 patients in each group. If the PO complication rate is 1%, 450 patients would be required in each group to define this difference. This issue of safety is inextricably entwined with the staffing issue previously mentioned, and with the issue of who should administer sedative medications. In many hospitals, both ketamine and propofol are classed as anesthetic drugs, with their use restricted to anesthesiologists. Acute airway obstruction in an 11-month-old infant may be a life threatening event for a cardiologist, however, it would be a routine and easily managed event for the anesthesiologist.
When this study was designed in 1994, an informal survey revealed that 60% of pediatric cardiac cath labs routinely used DPT. In 1995 the AAP Committee on Drugs (6) published its critique of DPT, stating in the conclusions that whereas "... DPT ... remains a widely used sedative and analgesic... . Neither the combination itself nor its dosage is based on sound pharmacologic data. There is a high rate of therapeutic failure as well as a high rate of serious adverse reaction, including ... death, associated with its use." Because of this critique and the reports of other complications (16), alternatives should be sought. Clearly, within the framework of this study, PO ketamine/midazolam was superior. The framework of this study, however, included the presence of a pediatric anesthesiologist in the cardiac cath lab. In our own hospital, we have seen more anesthesia involvement with cardiac caths. This is partly related to the increased number of interventional procedures, however, it also reflects recognition of superior patient sedation seen in this study. Superior patient safety may also be a benefit, albeit an unproved one.
A properly blinded study design was a major concern. First, IM DPT may be more painful than IM saline, and can leave a "knot" at the injection site. The cardiac cath lab nursing team noted one 2 x 2-cm knot; however, these differences were otherwise not apparent. Similarly, we were concerned that PO ketamine/midazolam would be poorly tolerated compared with the flavored vehicle only; however, this was also not apparent. Only 1 of the 51 patients expectorated a portion of the PO fluid. Finally, problems with oral secretions, dysphoric reactions, and cardiosympathetic stimulation can occur when ketamine is given alone, including in children (7,26,27). None of these problems occurred with the combination of ketamine/midazolam. The combination of these two drugs also yielded sleep rather than the eyes-open, dissociated state that can occur with ketamine alone. Interestingly, two patients noted under "comments" to be "dissociated but restless" were both in the IM group. The staggered time frame of dosing, along with these findings, allowed successful blinding.
In summary, we found that PO ketamine/midazolam is clearly superior to IM DPT for pediatric cardiac cath. This regimen must be delivered safely, and safety may require that anesthesiologists play a role in the pediatric cardiac cath lab.
| Acknowledgments |
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The authors wish to acknowledge the invaluable expertise of Victor Whalen, RPh, the assistance of David E. Miles, BS, and the administrative grace of Ms. Glynda Brooks. We would also like to thank Patty Welch, CCRN, who pushed us to begin and to pursue this investigation.
| References |
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This article has been cited by other articles:
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J. P. Cravero and G. T. Blike Review of Pediatric Sedation Anesth. Analg., November 1, 2004; 99(5): 1355 - 1364. [Abstract] [Full Text] [PDF] |
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R. Yumul, A. Emdadi, and N. Moradi Anesthesia for Noncardiac Surgery in Children with Congenital Heart Disease Seminars in Cardiothoracic and Vascular Anesthesia, June 1, 2003; 7(2): 153 - 165. [Abstract] [PDF] |
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M. E. McCann and Z. N. Kain The Management of Preoperative Anxiety in Children: An Update Anesth. Analg., July 1, 2001; 93(1): 98 - 105. [Full Text] [PDF] |
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