per airway obstruction (UA O) in children with enlarged ton- sils during inhalation of nitrous oxide (N2 0). Methods: Following premedication with oral midazolam,.
Upperairwayobstruction duringmidazolam/nitrous oxidesedation in childrenwithenlarged tonsils Ronald S. Litman, DOJennifer A. Kottra,DORobert J. Berkowitz, DDS Denham S. Ward, MD,PhD
Abstract
Fishbaughet al., confirmedthe potential for airwayobstruction in sedatedchildrenwith enlargedtonsils during Purpose."Thepurposeof this nonrandomized, case-con- a neckflexion maneuver.* Furthermore,the pediatric littrol study wasto examinethe incidenceandseverity of up- erature contains a report of a child with hypertrophic per airwayobstruction(UAO) in childrenwith enlargedton- tonsils whodevelopedsignificant upper airwayobstrucsils duringinhalationof nitrousoxide(N20). 7tion associated with chloral hydrate sedation. Methods:Followingpremedicationwith oral midazolam, In this study, wesoughtto determineif children with 0.5 mg/kg, measurements werecollected duringa 3-minute enlargedtonsils wereat an increased risk of developing controlperiod followedby 3 minutesof breathing50% N20 significant UAOduring sedation with orally adminisin oxygen.Anunblindedanesthesiologisthelda facemask over tered midazolam and 50% N20 inhalation. We the child’s mouthand nose withoutsupportingthe heador comparedthe incidence of UAO in a group of children neck, or a~tempting to maintainairwaypatency.Every20 sec- with enlarged tonsils (presenting for tonsillectomy) and onds,the degreeof airwayobstructionwasgradedas none,par- a control groupconsisting of children without enlarged tial, or complete.Twenty-five childrenpresentingfor tonsil- tonsils presentingfor other types of elective surgery. lectomyand25 controlswithoutenlargedtonsils participated. Methods Results: During50% N~Oinhalation, 14children (56%) The Research Subject’s Review Board of the Uniin the tonsillectomygroup,and four children (16%)in the versity of Rochester approved this study. The control groupdemonstrated partial UAO. Onechild in the procedures, possible discomforts or risks, as well as tonsillectomygroupwith partial UA0 developedhypoxemia possible benefits wereexplainedfully to the parents of (SpO~72%).Onechild in the tonsil groupdevelopedcom- the children involved, and their verbal and written conplete UAOduring inhalation of 50%N~O. sent wasobtained prior to the investigation. Thestudy Conclusion:Children whoreceive sedation with oral group consisted of children about to undergoelective midazolamand 50%N~Oinhalation mayexhibit signifitonsillectomy for hypertrophic tonsils and a control cant UAO,especially in the presenceof enlargedtonsils. group consisted of healthy children, without a history Presedationphysical examsshouldevaluate the presenceof of enlarged tonsils or nighttime snoring, undergoing tonsil size during examinationof the mouthand airway. other types of elective surgical procedures.Therewasno (Pediatr Dent 20:5 318-320, 1998) attempt to verify the absenceof enlargedtonsils in the control groupother than history. Exclusioncriteria inn pediatric dentistry, it is common practice to use cludedthe presenceof congenitalfacial anomaliesor the presenceof an upper respiratory infection. All children a combinationof inhaled N20with systemic sedatives to achieve anxiolysis and/or analgesia.2-4 The were premedicatedwith oral midazolam,0.5 mg/kg, 15effects of N20on ventilatory parameters has been de30 rain prior to induction of anesthesia. Uponentering scribed in intubated pediatric patients 5 but little is the operating room the usual monitors (precordial knownabout its effects on upper airway patency stethoscope, electrocardiograph, pulse oximeter, autoduring sedation or general anesthesia in nonintubated mated blood pressure device) were attached, and the patients. In a previous publication, wedemonstrated child wasplaced supinewith the headresting on a small that children who inhaled 15-60% N20 following folded blanket in the neutral position. midazolam premedication had no evidence of Study protocol UAO despite progressing beyond "conscious" sedation The study protocol consisted of two consecutive 6at 30%. stages of measurements:1) 3-min control period (F102 Pediatric anesthesiologists commonly find that chil100%) and 2) 3 min of 50%N20/50% 02 inhalation dren with hypertrophic tonsils have an increased (determined by end-tidal monitoring) after whichhaincidence of UAOduring induction of general aneslothane was added to completethe induction of general thesia for tonsillectomy. A recent publication by
I
318 AmericanAcademyof Pediatric Dentistry
Pediatric Dentistry- 20.’5, 1998
anesthesia. Duringthis sequence,all children had continuous airway managementby the same experienced pediatric anesthesiologist whoheld the facemaskwith an effective tight seal over the child’s mouthand nose. The facemaskwas held in place such that there was no direct physical contact with the patient which could havealtered the shape or patency of the airway. Children were allowedto movetheir heads freely from side to side with the facemaskpresent if they desired. Every 20 s the anesthesiologist managingthe airway graded the degree of UAO as either none, partial, or complete, based on clinical signs and capnography. Clinical signs includedvisualization of chest rise, hearing stridor, and feeling movementof the ventilation bag. Capnographicsigns included loss or diminution of the normal waveform.A research assistant whowas present continuously recorded these assessments. Maneuvers to improve the patency of the upper airway (e.g., changing neck position) were attempted only whenthe patient’s oxygensaturation decreased to less than 92%or if completeairway obstruction occurred. Studies were performed with children breathing through the smallest appropriate facemask connected to a pediatric circle system(Vital Signs, Totowa,NJ) attached to an anesthesia machine(Ohmeda,Madison, WI). During data analysis, UAO assessments were confirmed by respiratory impedance plethysmography (RIP) (Respi-Trace®, Ambulatory Monitoring Inc., Ardsley, NY).TheRIP consists of two coils of Tefloninsulated wire sewnonto elastic bandsthat encircle the rib cage and abdomen.Changesin cross-sectional areas of the rib cage and abdominalcompartmentsalter the self-inductance of the coils and are displayed graphically as waveform patterns. During normal breathing, the chest wall and abdominalcavity expand and contract simultaneouslyand the patterns obtained with the RIP are synchronous, or "in phase". When UAOoccurs, the normal outward movementof the rib cage and abdomenduring inspiration is then replaced by asynchronousor even paradoxical motion, in which the rib cage movesinward during inspiration. This phenomenon is referred to as thoracoabdominal asynchrony (TAA). The degree of TAAhas been demonstrated to be quantitatively related to the severity of airflow obstruction.8 The RIPtracings were not available to the anesthesiologist during the study sequence. The presence of abdominal movementsbut absence of end-tidal CO2 confirmed complete UAO.Continuous recordings of SpO PEvN20,respiratory rate, 2, PEvCO2, (Nellcor N-1000, Hayward,CA)and RIP tracings were stored by a computerizeddata collection system? The Nellcor N-1000wasinternally calibrated with each use. Quantitative calibration of the RIPwas not performed. Statistical analysis The Wilcoxon’s rank-sum test for continuous nonparametric data, and chi-square analysis and Fisher’s Pediatric Dentistry-20:5, 1998
exact test for nominaldata statistically assessedsignificant differences betweenthe study and control groups. To determine sample size, we used data from a previous study6 which indicated that no children in the control group would have partial UAOduring inhalation of N20(following midazolampremedication) and, based on our ownclinical experience, weexpected approximately 50%of children with enlarged tonsils to have partial UAO during N_Oinhalation. Noother data exists in this area with whic~ato base a samplesize analysis. Usingan alpha(TypeI) error of 5%and a beta (Type II) error of 20%(power= 0.8), the required samplesize was calculated to be 23 patients per group. Statistical calculations were performedby SigmaStatTM for WindowsTM (Jandel, San Rafael, CA). Results The study population consisted of 25 children presenting for tonsillectomy and 25 presenting for other types of elective surgery whoserved as controls. Their characteristics are listed in Table1. Theages, weights, and sex distribution of the groupsdid not differ. Occurrences of partial and complete UAOare detailed in Table 2. Followingmidazolampremedication and prior to inhalation of N20,two children in the tonsillectomy group demonstrated partial UAO(both had SpO 2 values > 98%)comparedto none in the control group (P= NS). During 50%N20 inhalation, 14 children (56%)in the tonsillectomygroup and four children (16%)in the control group demonstrated partial UAO (P = 0.005). Onechild in the tonsillectomy group who had partial UAOdeveloped hypoxemia (SpO 2 72%). Onechild in the tonsil group developedcomplete UAO during inhalation of 50%N20. Discussion The results of our study extend the observations of Fishbaughet al.1 and further emphasizethat children with enlargedtonsils are at increased risk for developing airwayobstructionafter receivingsedation with oral midazolamand N20. As a conservative measure, one would have to assume that similar results would be found whenusing midazolamby other routes of administration(e.g., nasal, rectal). Ourresults underscore l TAB!E!pAT!EN~_ARACTER!$!,~$ Study Group Tonsils Controls >a
25
25
Sex (M/F)
20/5
16/9
5.0 + 2.3
6.2 + 2.3
Age(yrs) (mean_+
Weight (kg) (mean + SD) 24.4 + 10.9
23.6 +7.6
AmericanAcademyof Pediatric Dentistry 319
fromthe conditionsused in this study. Ourpatients were TABLE 2. OCCURRENCES OFUPPER AIRWAY OBSTRUCTIONsupine, with only voice stimulation and facemaskappliMidazolamPremedication Study Group UAO None Partial
Complete
Tonsillectomy
23
2
0
Controls
25
0
0
50%X2O Study Group
UAO None Partial Complete
Tonsillectomy
10 21
Controls
14 4
1 0
i ,
the importance of a thorough presedation history and physical exam, with particular emphasison questioning for nighttime snoring, and examination of the airway for tonsillar hypertrophy. In a previous study, wereported that although the combination of oral midazolamand 30-60%N~Oresulted in a progressionfromconsciousto deepsec~ation, noneof the children studied demonstratedclinically sig6 In that study, however,children with a nificant UAO. history of nighttime airway obstruction were purposely excluded.Theresults of the present study differ in that four children without enlarged tonsils (control group) developed partial UAO.Although it is possible that methodological differences between the studies accountedfor this discrepancy,it is morelikely that the numbersof patients in each groupweresufficiendysmall, causing small differences to seemmoresignificant. There are several limitations the reader mustkeepin mindwheninterpreting the results of this study. First, the investigator whoheld the facemaskand assessed the degree of airway obstruction knewthe group to which the patient belongedand was, therefore, not blinded. Althoughthe degree of bias was minimizedby confirmationof UAO during data analysis (using the RIP), is theoretically possible that this investigator mayhave unconsciouslyand subtly altered the position or shape of the child’s airwayduring the study. Blindingthe investigator wouldhave been extremelydifficult. In our institution, tonsillectomies are routinely performedin a particular operating roomand the presence of the surgeon would have unblinded the study. Second, we studied combination therapy. Our results may have occurred because of an additive effect ofmidazolamand N~Oand maynot be applicable to N20alone. Finally, an~d perhaps most important, the conditions under which children receive N20and other sedatives during a typical pediatric dental procedureordinarily differ 320 American Academy of PediatricDentistry
cation. Duringa typical dental procedure,the child may lie semirecumbent and mightbe stimulated by insertion of a mouthprop or injections of local anesthesia. External stimuli will ultimately determinethe child’s level of consciousness and breathing patterns during sedation and must be continuously assessed by the practitioner with the appropriate monitors and attendant personnel.
Conclusions 1. Children who receive sedation with oral midazolamand 50%N20inhalation mayexhibit clinically significant airwayobstruction,especially in the presenceof enlargedtonsils. 2. Presedation evaluations should routinely include questions concerning the presence of nighttime snoring and tonsil size should be assessed during examination of the mouth and airway. Dr. Litmanis associate professor of Anesthesiology and Pediatrics and Chief of the Divisionof Pediatric Anesthesia,Dr. Kottra is a resident in the Departmentof Pediatrics, and Dr. Wardis professor and Chairmanof the Departmentof Anesthesiologyat the University of Rochester.Dr. Berkowitzis professorof Pediatric Dentistry at Eastman DentalCenterandChief of the Divisionof Pediatric Dentistry in the Departmentsof Clinical Dentistry and Pediatrics at the Universityof Rochester,all in Rochester, NewYork. This study was supported by a grant from the Foundationfor Anesthesia Educationand Researchwith a grant fromthe Society of Pediatric Anesthesia.
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175-81,1994. 3. FukutaO, Braham RL,YanaseH, AtsumiN, KurosuK: The sedativeeffectof intranasalmidazolam administration in the dentaltreatment of patientswithmental disabilities.PartI. The effectof a 0.2mg/kg dose.J ClinPediatrDent17:231-37, 1993. 4. FuksAB,Kaufman E, Ram D, Hovav S, ShapiraJ: Assessment of twodosesof intranasalmidazolam for sedation of young pediatric dentalpatients.PediatrDent16:301-305, 1994. 5. MuratI, Saint-Maurice JP, Beydon L, MacGee K: Respiratory effectsof nitrousoxideduring isoflurane anaesthesia in children. BrJ Anaesth 58:1122-29, 1986. 6. Litman RS, Berkowitz RJ, WardDS: Levels of consciousness and ventilatory parameters in youngchildren during sedation with oral midazolamand nitrous oxide. ArchPediatr Adolesc Med150:671-75, 1996. 7. Biban P, Baraldi E, PettennazzoA, Filippone M,Zacchello F: Adverseeffect of chloral hydrate in two youngchildren with obstructive sleep apnea. Pediatrics 92:461-63,1993. 8. Alien JL, Wolfson MR, McDowell K, Shaffer TH: Thoracoabdominal asynchronyin infants with airflow obstruction. AmRev Respir Dis 141:337-42, 1990. 9. Jenkins JS, Valcke CP, WardDS: A programmablesystem for acquisition and reductionof respiratory physiologicaldata. Ann BiomedEng 17:93-108, 1989. PediatricDentistry-20:5,1998
