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May 1997
Efficacy and safety of intravenous midazolam and ketamine as sedation for a therapeutic and diagnostic procedures in children.
Parker RI, Mahan RA, Giugliano D, Parker MM; Pediatrics 1997; 99:427-431.
[ see abstract below ]
Clinicians in many specialties are faced with the challenges of providing safe and cost-effective sedation for children undergoing painful and non-painful diagnostic and therapeutic procedures. The JCAHO has charged anesthesiologists with the responsibility of setting uniform standards of care for sedation performed throughout a given institution.
In this study, Parker and colleagues from the Department of Pediatrics at the State University of New York at Stony Brook describe the efficacy and safety of a protocol for using intravenous midazolam and ketamine to sedate children undergoing a variety of therapeutic and diagnostic procedures. The authors are to be congratulated for attempting to address the sedation process for children. However, a number of serious concerns are raised by this paper.
According to the Committee on Drugs of the American Academy of Pediatrics, the definition of "conscious sedation" is a medically controlled state of depressed consciousness that permits appropriate response by the patient to physical stimulation or verbal command, e.g. 'open your eyes.' The drugs and techniques used should carry a margin of safety wide enough to render unintended loss of consciousness highly unlikely. This does not mean reflex withdrawal to pain, but rather a response to a painful stimulus such as saying "ouch" or pushing a practitioner's hand away from the site of discomfort.*
Once consciousness is lost, the patient is somewhere between deep sedation and general anesthesia, with all their attendant risks. In the abstract, the authors of this paper state that their midazolam ketamine combination was used to provide "conscious sedation," whereas in the body of the paper, they acknowledge that only "two-thirds to three-quarters of the children sedated with this regime are able to respond to verbal stimuli or are talking during the procedure." This is because the patients have received 1-2 mg/kg ketamine intravenously after 0.05 to 0.1 mg/kg of midazolam. This dose of ketamine is recommended for induction of general anesthesia!
Thus, it is not adequate to have a second individual trained only in "bag/mask ventilation," but this person should be experienced with endotracheal intubation as well. Also, the authors also need to be more emphatic that this technique IS NOT (not "may not be") be suitable for patients at increased risk of developing problems with ketamine. Also, no mention is made of age-related dosing requirements.
The dietary precautions the AAP recommends before elective sedation in patients without increased risk of aspiration of gastric contents are:
Age |
No Milk or Solids (hrs)
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No more Clear Liquids (hr)
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0 - 5 months
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4
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2
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6 - 36 months
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6
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2
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> 36 months
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8
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2
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The deep sedation/general anesthesia described in a substantial number of the patients in this paper is of particular concern because their NPO guidelines were 4 hours for patients of all ages.
Ketamine can produce copious secretions, particularly in children who have (or are recovering from) an upper respiratory tract infection. The authors did observe that "all patients developed some degree of increased oral secretions with some patients requiring oral suctioning during or after the procedure". It has been the experience of many anesthesiologists that if an anti-sialagogue is not administered, there is an increased incidence of laryngospasm and airway obstruction.
In summary, it is important to be aware that deep sedation/general anesthesia can be induced by intravenous (or intramuscular, transmucosal, rectal or even oral) administration of ketamine and a variety of other drugs. Unexpectedly deep levels of sedation are particularly likely to occur when sedative and/or analgesic drugs are administered in combination.
* Committee on Drugs, American Academy of Pediatrics. Guidelines for monitoring and management of pediatric patients during and after sedation for diagnostic and therapeutic procedures. Pediatrics 1992; 89:1110-1114.
Return to the Current Literature Review Front Page, or read the abstract:
ABSTRACT
Objective: We have used the combination of midazolam, a short-acting benzodiazepine, and ketamine, a "dissociative anesthetic," to provide conscious sedation for invasive or lengthy procedures.
Methods: A total of 350 procedures (74 lumbar punctures, 97 bone marrow aspirations or biopsies, 84 radiotherapy sessions, and 95 imaging studies) were performed on 68 children, 4 months to 17 years of age, in both inpatient and ambulatory settings. All patients had an intravenous line in place and were monitored for heart rate and 02 saturation by pulse oximetry for the duration of the procedure and recovery time. Blood pressure was monitored periodically (every 5 to 30 minutes).
Oxygen and suction equipment was available during the procedure. In addition to the individual performing the procedure, a second staff member trained in airway management (e.g., physician, nurse practitioner, or registered nurse) was present to monitor vital signs and respiratory status. Patients were sedated initially with midazolam (0.05 to 0.1 mg/kg intravenously; maximum single dose of 2mg, maximum total dose of 4mg), followed by ketamine (1 to 2 mg/kg intravenously). During lengthy procedures, additional doses of ketamine (0.5 to 1mg/kg) were given as necessary. Effectiveness of the sedation, recovery time, and adverse events associated with the sedative regimen were documented.
Results: All patients were effectively sedated with this regimen. Four patients experienced transient decrease in O2 saturation (less than 85%) requiring temporary interruption of the procedure and oxygen by blow-by; the procedure was subsequently completed without incident in each case. Two patients experienced significant agitation during recovery from sedation.
This side effect resolved spontaneously after 5 to 10 minutes in one patient and was effectively treated with diphenhydramine hydrochloride in the other. Twenty-four lumbar punctures were associated with transient decrease in O2 saturation (88% to 92%), which improved by relief of neck flexion and/or blow-by oxygen. No hypotension, bradycardia, or respiratory depression requiring respiratory support or reversal of sedation was noted.
Anesthesia recovery time ranged from less than15 minutes to 120 minutes with more than 70% of patients recovering within 30 minutes. Most patients demonstrated an increase in oral secretions requiring occasional suctioning. Transient sleep disturbances were reported in only two patients.
Conclusions: This sedative regimen of intravenous midazolam and ketamine was found to be safe and effective. Its use has greatly reduced patient and parent anxiety for diagnostic and therapeutic procedures.
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