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14: The Relationship Between the Capnogram Waveform and Clinical Signs of Respiratory Depression During Procedural Sedation
Research Forum Abstracts (5.4%). Of the rescue strategies performed, 24 were through the use of the bougie (mostly by anaesthetists), three by cricothyriodotomy, four by tracheostomies, six with the glidescope and three with the laryngeal mask airway. The rest the airways were secured by tracheal intubation using the laryngoscope. Conclusions: Emergency physicians manage most of the difficult airways successfully (68.8%). However, the success rate can be further improved through the more frequent use of the bougie or other rescue device. A possible suggestion would be for the emergency physician to use the bougie after the second or third attempt of direct oral tracheal intubation while awaiting the anaesthetist’s arrival.
12
The Use of the Laryngeal Tube is Preferred to Endotracheal Intubation in Manikin-Simulated Cardiac Arrest Resuscitations
Wong E, Lim E, Gan H/Singapore General Hospital, Singapore, Singapore
Study Objective: Current thinking on cardiopulmonary resuscitations and recent ACLS recommendations on cardiac arrest advise continuous chest compressions which should be minimally disrupted by procedures like ventilation and airway intervention. Previous studies have shown that the Laryngeal Tube (LT) can be used in mechanical ventilation with airway leak pressures of over 26 cmH2O. We propose that the LT is faster to insert and less interruptive to chest compressions than endotracheal intubation (ETI) and can replace ETI in CPR of patients in cardiac arrest in the emergency department. Methods: Using a manikin model, 20 physician participants of an ACLS-provider course were recruited and taught to perform LT intubation and ETI on an ALS manikin. They were later tested on their independent insertion of both tubes separately. Data collected included (1) apnea times (time when bag-mask ventilation stopped until reinitiation of bagging through either the LT or ET tube), (2) duration of interruption of chest compressions, (3) no. of interruptions to chest compressions, (4) no. of attempts, (5) success rate. The data was analysed using the paired samples T-test. Results: The mean apnea time for the use of the LT was 17.35s versus 22.25 sec for ETI. The mean duration of interruption of chest compression was 0 s for the LT and 11.75s for ETI. The mean no. of interruptions to chest compressions was 0 for LT and 0.85 for ETI. The mean no. of attempts at intubation was 1 for LT and 1.4 for ETI. All the above results were statistically significant with p⬍ 0.002. The success rate for the insertion of both tubes was 100%. Conclusion: The LT is faster to insert with a higher first attempt success rate; it can be inserted without interruptions to chest compressions compared to ETI. It deserves to be studied in real-life resuscitations in RCTs. It is may be shown to be preferred to ETI in resuscitations of patients in cardiac arrest.
13
NEAR Misses: An Analysis of Unreported Intubations
Myers D, Bair AE/UC Davis Medical Center, Sacramento, CA
Study Objectives: Data registries are valuable research tools but have certain inherent limitations. Reporting bias, especially when analyzing technical performance, is a potential concern. We searched for any evidence of unreported complications among patients from our center who were eligible, but went unreported, to the National Emergency Airway Registry (NEAR) II. Methods: We performed a retrospective review, based on medical and billing records, of all patients who were intubated in the ED during a 3 year period (July ’99 to June ’02). We then identified all patients who had not been reported to the NEAR database. The records of the unreported patients were analyzed for any evidence of technical events or complications. Three independent reviewers analyzed the records if there was any suggestion of a complication. An a priori defined list of “complications” and lesser technical issues, “events,” was used for categorization. Descriptive statistics and 95% confidence intervals (CI) were used to analyze the data. Results: A total of 1,629 patients were intubated during this period. We identified 326 (20%) charts that were not reported to the registry. Among these, 310 (95%), (95% CI 92% to 97%) were entirely without complication or event. There were 3 major events (eg, prolonged hypoxia) and 13 minor events (eg, immediately recognized esophageal or main stem intubation). We did not encounter any complications among the group that went unreported to the registry. Conclusion: We found no clinically significant complications among those patients who were not reported to the NEAR database. While this review was limited to one center and focused on readily identifiable events and complications, it may suggest that self-reported complications are well represented in the National Emergency Airway Registry.
Volume , . : September
14
The Relationship Between the Capnogram Waveform and Clinical Signs of Respiratory Depression During Procedural Sedation
Hubbard D, Mayerle J, Miner JR/Hennepin County Medical Center, Minneapolis, MN
Study Objectives: To evaluate the relationship between capnogram waveform and clinical signs of respiratory depression (RD) during procedural sedation and analgesia (PSA) in the emergency department (ED). Methods: This was a prospective observational study of a convenience sample of adult patients undergoing PSA with propofol in the ED between July and December, 2006. Investigators noted clinical signs of RD and recorded capnogram waveform data at baseline and at 30-second intervals. Clinical signs of RD included: O2 saturation ⬍ 92%, addition of supplemental O2, increase in supplemental O2, use of bag-valve-mask, patient repositioning for respiration, physical or verbal stimulus for respiration, reversal agent use, oral airway use, vomiting, and intubation. Capnogram waveform consists of four distinct phases: an ascending, steep sloped Phase I representing the initial part of exhalation and equilibration of the sampling line with alveolar air; a flat, elevated Phase II representing the second part of exhalation; a descending, steep sloped Phase III representing inhalation and re-equilibration of the sampling line with room air; and a flat Phase IV associated with the second part of inhalation. In addition to noting normal patterns the following patterns were also recorded: long Phase I, long Phase II, short Phase II, long Phase III, and absence of waveform. The researcher collecting data recorded the predominant waveform over the 30-second intervals. Data were analyzed using descriptive statistics and Chi-square analysis. Results: 52 patients were enrolled, 6 were excluded for protocol violations. The mean patient age was 35.9 ⫾ 12.1 years (range 18 to 72). Of the 1,073 recorded 30second intervals, 125 were associated with a clinical sign of RD. Chi-square analysis indicated that a difference existed between intervals with clinical signs of RD and intervals without clinical signs of RD (p⬍0.001). Normal waveform was the most commonly observed pattern and very few signs of clinical RD were associated with it (4.5%, n⫽601). Likewise, long Phase II was also infrequently associated with a clinical sign of RD (1.8%, n⫽57) as was short Phase II (2.8%, n⫽214). Absent waveform was associated with the greatest incidence of RD (56%, n⫽137). Furthermore, it was the waveform most frequently associated with all signs of RD except for addition of supplemental O2 (which was most frequently associated with long Phase III). Long Phase I (26%, n⫽23) and long Phase III (19.5%, n⫽41) were both frequently associated with RD. Conclusion: Absent waveform was strongly associated with clinical signs of RD. Long Phase I and long Phase III were somewhat less strongly associated with RD. Any of these three signs would appear to be indicators that a patient is at risk of developing RD during PSA. Given its low rate of association with clinical signs of RD, a normal waveform may be an indicator of low risk for RD. However, the association of normal waveform with instances of clinical signs of RD indicates that capnography waveform is not a perfect reflection of the clinical reality.
15
Minimum Ischemic Time to Produce Mitochondriopathy in an Acute Murine Hind Limb Ischemia/Reperfusion
Tran TP, Muelleman RL, Pipinos II/University of Nebraska Medical Center, Omaha, NE
Study Objectives: A tourniquet is often used to control severe extremity hemorrhage in battlefield, but its use can also lead to ischemic mitochondriopathy, which is suspected to play a crucial role in the ischemia/reperfusion (I/R) syndrome. We investigated the minimum tourniquet time that causes mitochondriopathy in a tourniquet-induced I/R model. Methods: Three groups of mice (C57/BL6) underwent an I/R protocol. The first group (N⫽12) was submitted to 1 hour of unilateral hind limb ischemia using a tourniquet, followed by 4 hours of reperfusion (1/4 I/R), the second group (N⫽10) 2 hours of ischemia and 4 hours of reperfusion (2/4 I/R), with the third group (N⫽16) serving as time controls (1 and 2 hours of sham ischemia, followed by 4 hours of reperfusion). Complete ischemia of the ischemic limb was verified with a laser Doppler. At the end of the reperfusion period, flexor muscles from ischemic limbs and controls were immediately harvested, frozen, and subsequently analyzed via spectrophotometry. Citrate Synthase (CS) activity, which serves as standard index of mitochondrial content, was measured and normalized to total protein content (CS/ prot). Similarly, complexes I and IV activities, representative of the electron transport chain (ETC) in mitochondria, were measured and normalized to CS. Mann-Whitney
Annals of Emergency Medicine S5
12
The Use of the Laryngeal Tube is Preferred to Endotracheal Intubation in Manikin-Simulated Cardiac Arrest Resuscitations
Wong E, Lim E, Gan H/Singapore General Hospital, Singapore, Singapore
Study Objective: Current thinking on cardiopulmonary resuscitations and recent ACLS recommendations on cardiac arrest advise continuous chest compressions which should be minimally disrupted by procedures like ventilation and airway intervention. Previous studies have shown that the Laryngeal Tube (LT) can be used in mechanical ventilation with airway leak pressures of over 26 cmH2O. We propose that the LT is faster to insert and less interruptive to chest compressions than endotracheal intubation (ETI) and can replace ETI in CPR of patients in cardiac arrest in the emergency department. Methods: Using a manikin model, 20 physician participants of an ACLS-provider course were recruited and taught to perform LT intubation and ETI on an ALS manikin. They were later tested on their independent insertion of both tubes separately. Data collected included (1) apnea times (time when bag-mask ventilation stopped until reinitiation of bagging through either the LT or ET tube), (2) duration of interruption of chest compressions, (3) no. of interruptions to chest compressions, (4) no. of attempts, (5) success rate. The data was analysed using the paired samples T-test. Results: The mean apnea time for the use of the LT was 17.35s versus 22.25 sec for ETI. The mean duration of interruption of chest compression was 0 s for the LT and 11.75s for ETI. The mean no. of interruptions to chest compressions was 0 for LT and 0.85 for ETI. The mean no. of attempts at intubation was 1 for LT and 1.4 for ETI. All the above results were statistically significant with p⬍ 0.002. The success rate for the insertion of both tubes was 100%. Conclusion: The LT is faster to insert with a higher first attempt success rate; it can be inserted without interruptions to chest compressions compared to ETI. It deserves to be studied in real-life resuscitations in RCTs. It is may be shown to be preferred to ETI in resuscitations of patients in cardiac arrest.
13
NEAR Misses: An Analysis of Unreported Intubations
Myers D, Bair AE/UC Davis Medical Center, Sacramento, CA
Study Objectives: Data registries are valuable research tools but have certain inherent limitations. Reporting bias, especially when analyzing technical performance, is a potential concern. We searched for any evidence of unreported complications among patients from our center who were eligible, but went unreported, to the National Emergency Airway Registry (NEAR) II. Methods: We performed a retrospective review, based on medical and billing records, of all patients who were intubated in the ED during a 3 year period (July ’99 to June ’02). We then identified all patients who had not been reported to the NEAR database. The records of the unreported patients were analyzed for any evidence of technical events or complications. Three independent reviewers analyzed the records if there was any suggestion of a complication. An a priori defined list of “complications” and lesser technical issues, “events,” was used for categorization. Descriptive statistics and 95% confidence intervals (CI) were used to analyze the data. Results: A total of 1,629 patients were intubated during this period. We identified 326 (20%) charts that were not reported to the registry. Among these, 310 (95%), (95% CI 92% to 97%) were entirely without complication or event. There were 3 major events (eg, prolonged hypoxia) and 13 minor events (eg, immediately recognized esophageal or main stem intubation). We did not encounter any complications among the group that went unreported to the registry. Conclusion: We found no clinically significant complications among those patients who were not reported to the NEAR database. While this review was limited to one center and focused on readily identifiable events and complications, it may suggest that self-reported complications are well represented in the National Emergency Airway Registry.
Volume , . : September
14
The Relationship Between the Capnogram Waveform and Clinical Signs of Respiratory Depression During Procedural Sedation
Hubbard D, Mayerle J, Miner JR/Hennepin County Medical Center, Minneapolis, MN
Study Objectives: To evaluate the relationship between capnogram waveform and clinical signs of respiratory depression (RD) during procedural sedation and analgesia (PSA) in the emergency department (ED). Methods: This was a prospective observational study of a convenience sample of adult patients undergoing PSA with propofol in the ED between July and December, 2006. Investigators noted clinical signs of RD and recorded capnogram waveform data at baseline and at 30-second intervals. Clinical signs of RD included: O2 saturation ⬍ 92%, addition of supplemental O2, increase in supplemental O2, use of bag-valve-mask, patient repositioning for respiration, physical or verbal stimulus for respiration, reversal agent use, oral airway use, vomiting, and intubation. Capnogram waveform consists of four distinct phases: an ascending, steep sloped Phase I representing the initial part of exhalation and equilibration of the sampling line with alveolar air; a flat, elevated Phase II representing the second part of exhalation; a descending, steep sloped Phase III representing inhalation and re-equilibration of the sampling line with room air; and a flat Phase IV associated with the second part of inhalation. In addition to noting normal patterns the following patterns were also recorded: long Phase I, long Phase II, short Phase II, long Phase III, and absence of waveform. The researcher collecting data recorded the predominant waveform over the 30-second intervals. Data were analyzed using descriptive statistics and Chi-square analysis. Results: 52 patients were enrolled, 6 were excluded for protocol violations. The mean patient age was 35.9 ⫾ 12.1 years (range 18 to 72). Of the 1,073 recorded 30second intervals, 125 were associated with a clinical sign of RD. Chi-square analysis indicated that a difference existed between intervals with clinical signs of RD and intervals without clinical signs of RD (p⬍0.001). Normal waveform was the most commonly observed pattern and very few signs of clinical RD were associated with it (4.5%, n⫽601). Likewise, long Phase II was also infrequently associated with a clinical sign of RD (1.8%, n⫽57) as was short Phase II (2.8%, n⫽214). Absent waveform was associated with the greatest incidence of RD (56%, n⫽137). Furthermore, it was the waveform most frequently associated with all signs of RD except for addition of supplemental O2 (which was most frequently associated with long Phase III). Long Phase I (26%, n⫽23) and long Phase III (19.5%, n⫽41) were both frequently associated with RD. Conclusion: Absent waveform was strongly associated with clinical signs of RD. Long Phase I and long Phase III were somewhat less strongly associated with RD. Any of these three signs would appear to be indicators that a patient is at risk of developing RD during PSA. Given its low rate of association with clinical signs of RD, a normal waveform may be an indicator of low risk for RD. However, the association of normal waveform with instances of clinical signs of RD indicates that capnography waveform is not a perfect reflection of the clinical reality.
15
Minimum Ischemic Time to Produce Mitochondriopathy in an Acute Murine Hind Limb Ischemia/Reperfusion
Tran TP, Muelleman RL, Pipinos II/University of Nebraska Medical Center, Omaha, NE
Study Objectives: A tourniquet is often used to control severe extremity hemorrhage in battlefield, but its use can also lead to ischemic mitochondriopathy, which is suspected to play a crucial role in the ischemia/reperfusion (I/R) syndrome. We investigated the minimum tourniquet time that causes mitochondriopathy in a tourniquet-induced I/R model. Methods: Three groups of mice (C57/BL6) underwent an I/R protocol. The first group (N⫽12) was submitted to 1 hour of unilateral hind limb ischemia using a tourniquet, followed by 4 hours of reperfusion (1/4 I/R), the second group (N⫽10) 2 hours of ischemia and 4 hours of reperfusion (2/4 I/R), with the third group (N⫽16) serving as time controls (1 and 2 hours of sham ischemia, followed by 4 hours of reperfusion). Complete ischemia of the ischemic limb was verified with a laser Doppler. At the end of the reperfusion period, flexor muscles from ischemic limbs and controls were immediately harvested, frozen, and subsequently analyzed via spectrophotometry. Citrate Synthase (CS) activity, which serves as standard index of mitochondrial content, was measured and normalized to total protein content (CS/ prot). Similarly, complexes I and IV activities, representative of the electron transport chain (ETC) in mitochondria, were measured and normalized to CS. Mann-Whitney
Annals of Emergency Medicine S5