Kenneth W. Dodd

Diagnosis of ST-Elevation Myocardial Infarction in the Presence of Left Bundle Branch Block With the ST-Elevation to S-Wave Ratio in a Modified Sgarbossa Rule

STUDY OBJECTIVE Sgarbossas rule, proposed for the diagnosis of acute myocardial infarction in the presence of left bundle branch block, has had suboptimal diagnostic utility. We hypothesize that a revised rule, in which the third Sgarbossa component (excessively discordant ST-segment elevation as defined by ≥5 mm of ST-segment elevation in the setting of a negative QRS) is replaced by one defined proportionally by ST-segment elevation to S-wave depth (ST/S ratio), will have better diagnostic utility for ST-segment elevation myocardial infarction (STEMI) equivalent, using documented coronary occlusion on angiography as reference standard. METHODS We collected admission ECGs for all patients with an acutely occluded coronary artery and left bundle branch block at 3 institutions. The ECGs of emergency department patients with chest pain or dyspnea and left bundle branch block, but without coronary occlusion, were used as controls. The R or S wave, whichever was most prominent, and ST segments, relative to the PR segment, were measured to the nearest 0.5 mm. The ST/S ratio was calculated for each lead that has both discordant ST deviation of greater than or equal to 1 mm and an R or S wave of opposite polarity; others were set to 0. The cut point for the most negative ST/S ratio with at least 90% specificity was determined. The revised rule is unweighted, requiring just 1 of 3 criteria. Diagnostic utilities of the original and revised Sgarbossa rules were computed and compared. McNemars test was used to compare sensitivities and specificities. RESULTS The study and control groups included 33 and 129 ECGs, respectively. The cut point selected for relative discordant ST-segment elevation was -0.25. Excessive absolute discordant ST-segment elevation of 5 mm was present in at least one lead in 30% of ECGs in patients with confirmed coronary occlusion versus 9% of the control group, whereas excessive relative discordant ST-segment elevation less than -0.25 was present in 79% vs. 9% [corrected].Sensitivity of the revised rule in which ST-segment elevation with an ST/S ratio less than or equal to -0.25 replaces ST-segment elevation greater than or equal to 5 mm was significantly greater than either the weighted (P<.001) or unweighted (P=.008) Sgarbossa rule: 91% (95% confidence interval [CI] 76% to 98%) versus 52% (95% CI 34% to 69%) versus 67% (95% CI 48% to 82%). Specificity of the revised rule was lower than that of the weighted rule (P=.002) and similar to that of the unweighted rule (P=1.0): 90% (95% CI 83% to 95%) versus 98% (95% CI 93% to 100%) versus 90% (95% CI 83% to 95%). Positive and negative likelihood ratios for the revised rule were 9.0 (95% CI 8.0 to 10) and 0.1 (95% CI 0.03 to 0.3). The revised rule was significantly more accurate than both the weighted (16% difference; 95% CI 5% to 27%) and unweighted (12% difference; 95% CI 2% to 22%) Sgarbossa rules. CONCLUSION Replacement of the absolute ST-elevation measurement of greater than or equal to 5 mm in the third component of the Sgarbossa rule with an ST/S ratio less than -0.25 greatly improves diagnostic utility of the rule for STEMI. An unweighted rule using this criterion resulted in excellent prediction for acute coronary occlusion.

Clinical decision rules for diagnostic imaging in the emergency department: A research agenda

BACKGROUND Major gaps persist in the development, validation, and implementation of clinical decision rules (CDRs) for diagnostic imaging. OBJECTIVES The objective of this working group and article was to generate a consensus-based research agenda for the development and implementation of CDRs for diagnostic imaging in the emergency department (ED). METHODS The authors followed consensus methodology, as outlined by the journal Academic Emergency Medicine (AEM), combining literature review, electronic surveys, telephonic communications, and a modified nominal group technique. Final discussions occurred in person at the 2015 AEM consensus conference. RESULTS A research agenda was developed, prioritizing the following questions: 1) what are the optimal methods to justify the derivation and validation of diagnostic imaging CDRs, 2) what level of evidence is required before disseminating CDRs for widespread implementation, 3) what defines a successful CDR, 4) how should investigators best compare CDRs to clinical judgment, and 5) what disease states are amenable (and highest priority) to development of CDRs for diagnostic imaging in the ED? CONCLUSIONS The concepts discussed herein demonstrate the need for further research on CDR development and implementation regarding diagnostic imaging in the ED. Addressing this research agenda should have direct applicability to patients, clinicians, and health care systems.

Intubation of Profoundly Agitated Patients Treated with Prehospital Ketamine

BACKGROUND Profound agitation in the prehospital setting confers substantial risk to patients and providers. Optimal chemical sedation in this setting remains unclear. OBJECTIVE The goal of this study was to describe intubation rates among profoundly agitated patients treated with prehospital ketamine and to characterize clinically significant outcomes of a prehospital ketamine protocol. METHODS This was a retrospective cohort study of all patients who received prehospital ketamine, per a predefined protocol, for control of profound agitation and who subsequently were transported to an urban Level 1 trauma center from May 1, 2010 through August 31, 2013. Identified records were reviewed for basic ambulance run information, subject characteristics, ketamine dosing, and rate of intubation. Emergency Medical Services (EMS) ambulance run data were matched to hospital-based electronic medical records. Clinically significant outcomes are characterized, including unadjusted and adjusted rates of intubation. RESULTS Overall, ketamine was administered 227 times in the prehospital setting with 135 cases meeting study criteria of use of ketamine for treatment of agitation. Endotracheal intubation was undertaken for 63% (85/135) of patients, including attempted prehospital intubation in four cases. Male gender and late night arrival were associated with intubation in univariate analyses (χ2=12.02; P=.001 and χ2=5.34; P=.021, respectively). Neither ketamine dose, co-administration of additional sedating medications, nor evidence of ethanol (ETOH) or sympathomimetic ingestion was associated with intubation. The association between intubation and both male gender and late night emergency department (ED) arrival persisted in multivariate analysis. Neither higher dose (>5mg/kg) ketamine nor co-administration of midazolam or haloperidol was associated with intubation in logistic regression modeling of the 120 subjects with weights recorded. Two deaths were observed. Post-hoc analysis of intubation rates suggested a high degree of provider-dependent variability. CONCLUSIONS Prehospital ketamine is associated with a high rate of endotracheal intubation in profoundly agitated patients; however, ketamine dosing is not associated with intubation rate when adjusted for potential confounders. It is likely that factors not included in this analysis, including both provider comfort with post-ketamine patients and anticipated clinical course, play a role in the decision to intubate patients who receive prehospital ketamine. Olives TD , Nystrom PC , Cole JB , Dodd KW , Ho JD . Intubation of profoundly agitated patients treated with prehospital ketamine. Prehosp Disaster Med. 2016;31(6):593-602.

Diagnostic Performance of High Sensitivity Compared with Contemporary Cardiac Troponin I for the Diagnosis of Acute Myocardial Infarction

BACKGROUND We examined the diagnostic performance of high-sensitivity cardiac troponin I (hs-cTnI) vs contemporary cTnI with use of the 99th percentile alone and with a normal electrocardiogram (ECG) to rule out acute myocardial infarction (MI) and serial changes (deltas) to rule in MI. METHODS We included consecutive patients presenting to a US emergency department with serial cTnI onclinical indication. Diagnostic performance for acute MI, including MI subtypes, and 30-day outcomes were examined. RESULTS Among 1631 patients, MI was diagnosed in 12.9% using the contemporary cTnI assay and in 10.4% using the hs-cTnI assay. For ruling out MI, contemporary cTnI ≤99th percentile at 0, 3, and 6 h and a normal ECG had a negative predictive value (NPV) of 99.5% (95% CI, 98.6-100) and a sensitivity of 99.1% (95% CI, 97.4-100) for diagnostic and safety outcomes. Serial hs-cTnI measurements ≤99th percentile at 0 and 3 h and a normal ECG had an NPV and sensitivity of 100% (95% CI, 100-100) for diagnostic and safety outcomes. For ruling in MI, contemporary cTnI measurements had specificities of 84.4% (95% CI, 82.5-86.3) at presentation and 78.7% (95% CI, 75.4-82.0) with serial testing at 0, 3, and 6 h, improving to 89.2% (95% CI, 87.1-91.3) by using serial cTnI changes (delta, 0 and 6 h) >150%. hs-cTnI had specificities of 86.9% (95% CI, 85.1-88.6) at presentation and 85.7% (95% CI, 83.5-87.9) with serial testing at 0 and 3 h, improving to 89.3% (95% CI, 87.3-91.2) using a delta hs-cTnI (0 and 3 h) >5 ng/L. CONCLUSIONS hs-cTnI and contemporary cTnI assays are excellent in ruling out MI following recommendations predicated on serial testing and the 99th percentile with a normal ECG. For ruling in MI, deltas improve the specificity. ClinicalTrials.gov Identifier: NCT02060760.

Definitive airway management in emergency department patients with a King laryngeal tube™ in place: a simple and safe approach.

To the Editor, We read with interest the article by Subramanian et al. describing their experience with definitive airway management in 48 patients arriving at the emergency department (ED) with a King LT(S)-D laryngeal tube (KingLT) placed by pre-hospital personnel. We agree that there are potential complications associated with removing the KingLT in such patients. We were surprised, however, at the proportion of patients requiring surgical airway management [14 (29%) patients] and airway techniques [i.e., tube exchange catheter or flexible bronchoscopy, 14 (29%)] beyond direct (DL) or video (VL) laryngoscopy. We therefore offer a summary of our own experience with such patients and suggest a simple, non-surgical technique for exchanging the KingLT for an endotracheal tube (ETT). Over a similar five-year period (2010-2015), a total of 454 patients arrived at our Level 1 trauma centre ED with a KingLT in situ. A survey of our faculty revealed that 453 (99.8%) patients had a definitive airway secured by emergency physicians with non-surgical techniques (Table). The most common definitive airway technique for patients with the KingLT in place was VL-guided endotracheal intubation without removing the device. We recently described this technique in detail, and we summarize it here. We believe that the simplest way to intubate with the KingLT (King Systems; Noblesville, IN, USA) in situ is to use VL and a bougie. During the first portion of the procedure, the KingLT balloons remain inflated, and ventilation through the device is ongoing. The first step is to place the VL blade anterior to the KingLT, advancing it along the tongue until the oropharyngeal balloon is well visualized (Figure A). The KingLT balloons are then deflated, allowing visualization of the glottic structures on the VL monitor. A bougie can then be advanced into the trachea followed by an ETT (Figure B-D). Unlike DL, VL consistently allows good visualization of the glottis with the KingLT in situ. Also, in rare cases of failed intubation, the KingLT remains in a functional position, and the balloons can be immediately re-inflated and ventilation resumed. In summary, our experience is that conventional nonsurgical techniques (most often VL) can be used to secure a definitive airway in nearly every patient arriving at the ED with a KingLT in place. We believe that the safest technique for managing such patients is to intubate endotracheally using VL and then place a bougie while the KingLT remains in position. This technique is simple, intuitive, and utilizes airway equipment that is readily available in most EDs and operating suites. This letter is accompanied by a reply. Please see Can J Anesth 2016; 63: this issue.

Evaluation of the Boussignac Cardiac arrest device (B-card) during cardiopulmonary resuscitation in an animal model

AIM OF THE STUDY The purpose of this study was to examine continuous oxygen insufflation (COI) in a swine model of cardiac arrest. The primary hypothesis was COI during standard CPR (S-CPR) should result in higher intrathoracic pressure (ITP) during chest compression and lower ITP during decompression versus S-CPR alone. These changes with COI were hypothesized to improve hemodynamics. The second hypothesis was that changes in ITP with S-CPR+COI would result in superior hemodynamics compared with active compression decompression (ACD) + impedance threshold device (ITD) CPR, as this method primarily lowers ITP during chest decompression. METHODS After 6min of untreated ventricular fibrillation, S-CPR was initiated in 8 female swine for 4min, then 3min of S-CPR+COI, then 3min of ACD+ITD CPR, then 3min of S-CPR+COI. ITP and hemodynamics were continuously monitored. RESULTS During S-CPR+COI, ITP was always positive during the CPR compression and decompression phases. ITP compression values with S-CPR+COI versus S-CPR alone were 5.5±3 versus 0.2±2 (p<0.001) and decompression values were 2.8±2 versus -1.3±2 (p<0.001), respectively. With S-CPR+COI versus ACD+ITD the ITP compression values were 5.5±3 versus 1.5±2 (p<0.01) and decompression values were 2.8±2 versus -4.7±3 (p<0.001), respectively. CONCLUSION COI during S-CPR created a continuous positive pressure in the airway during both the compression and decompression phase of CPR. At no point in time did COI generate a negative intrathoracic pressures during CPR in this swine model of cardiac arrest.

Head and thorax elevation during active compression decompression cardiopulmonary resuscitation with an impedance threshold device improves cerebral perfusion in a swine model of prolonged cardiac arrest

AIM OF THE STUDY As most cardiopulmonary resuscitation (CPR) efforts last longer than 15min, the aim of this study was to compare brain blood flow between the Head Up (HUP) and supine (SUP) body positions during a prolonged CPR effort of 15min, using active compression-decompression (ACD) CPR and impedance threshold device (ITD) in a swine model of cardiac arrest. METHODS Ventricular fibrillation (VF) was induced in anesthetized pigs. After 8min of untreated VF followed by 2min of ACD-CPR+ITD in the SUP position, pigs were randomized to 18min of continuous ACD-CPR+ITD in either a 30° HUP or SUP position. Microspheres were injected before VF and then 5 and 15min after start of CPR. RESULTS The mean blood flow (ml/min/g, mean±SD) to the brain after 15min of CPR was 0.42±0.05 in the HUP group (n=8) and 0.21±0.04 SUP (n=10), respectively, (p<0.01). The HUP group also had statistically significantly lower intracranial pressures and higher calculated cerebral perfusion pressures after 5, 15, 19 (before adrenaline) and 20 (after adrenaline) minutes of HUT versus SUP CPR. CONCLUSIONS After prolonged ACD-CPR+ITD in the HUP position, brain blood flow was 2-fold higher versus the SUP position. These positive findings provide strong pre-clinical support to proceed with a clinical evaluation of elevation of the head and thorax during ACD-CPR+ITD in humans in cardiac arrest.

The Bougie and First-Pass Success in the Emergency Department

Study objective: The bougie may improve first‐pass intubation success in operating room patients. We seek to determine whether bougie use is associated with emergency department (ED) first‐pass intubation success. Methods: We studied consecutive adult ED intubations at an urban, academic medical center during 2013. Intubation events were identified by motion‐activated video recording. We determined the association between bougie use and first‐pass intubation success, adjusting for neuromuscular blockade, video laryngoscopy, abnormal airway anatomy, and whether the patient was placed in the sniffing position or the head was lifted off the bed during intubation. Results: Intubation with a Macintosh blade was attempted in 543 cases; a bougie was used on the majority of initial attempts (80%; n=435). First‐pass success was greater with than without bougie use (95% versus 86%; absolute difference 9% [95% confidence interval {CI} 2% to 16%]). The median first‐attempt duration was higher with than without bougie (40 versus 27 seconds; difference 14 seconds [95% CI 11 to 16 seconds]). Bougie use was independently associated with greater first‐pass success (adjusted odds ratio 2.83 [95% CI 1.35 to 5.92]). Conclusion: Bougie was associated with increased first‐pass intubation success. Bougie use may be helpful in ED intubation.

Among patients with left bundle branch block, T-wave peak to T-wave end time is prolonged in the presence of acute coronary occlusion.

BACKGROUND Assessing the effect of myocardial ischemia on ventricular repolarization in the setting of left bundle branch block (LBBB) poses a challenge due to secondary prolongation of the QT interval inherent in LBBB. The T-wave peak to T-wave end (TpTe) interval has been noted to prolong during myocardial ischemia and correct after reperfusion in patients with normal conduction. Here we compare the TpTe intervals of patients with LBBB both with and without complete acute coronary occlusion (ACO). METHODS Retrospectively, emergency department patients with LBBB and symptoms of myocardial ischemia were identified both with angiographically-proven ACO and with No-ACO. The longest QT, JT, and TpTe intervals were analyzed. RESULTS The ACO and No-ACO groups consisted of 33 and 129 patients, respectively. The mean TpTe was longer in ACO (103.6ms [95%CI 98.5-108.7]) compared to No-ACO patients (88.6ms [95%CI 85.3-91.9]) (P<0.0001) and this held true after correction for heart rate. In ACO versus No-ACO, the TpTe also more frequently exceeded prolongation cutoffs of 85ms (30 [90%] versus 69 [54%]) and 100ms (25 [76%] versus 42 [33%]) (P<0.0001 for all). The mean QT, JT, QTc, and JTc intervals were not significantly different between the groups for either the Bazetts or Rautaharjus correction formulas. CONCLUSIONS In patients with LBBB on the ECG, the TpTe is longer and more frequently prolonged in patients with ACO compared to patients without ACO. Future studies of ventricular repolarization in patients with LBBB should include analyses of the TpTe interval.

In reply: Combined use of flexible bronchoscopy and video laryngoscopy for endotracheal intubation in patients with King laryngeal tube in situ.

To the Editor, We thank Drs El-Orbany and Schmid for describing an interesting and potentially valuable method for securing a definitive airway in patients presenting with a King laryngeal tube (King LT; King Systems; Noblesville, IN, USA) in situ when rapid intubation using video laryngoscopy (VL) with the use of a bougie is unsuccessful. Our department has a high rate of success with the VL method, which uses equipment that is standard in most emergency departments. However, if visualization is not possible using VL with the King LT in situ, the flexible bronchoscopic intubation technique described by Drs El-Orbany and Schmid would be an appropriate next step prior to a surgical airway, assuming that the patient can be well oxygenated with the King LT. Similar to our method, the method described by Drs ElOrbany and Schmid allows oxygenation and ventilation throughout most of the procedure. Flexible bronchoscopy, however, requires the use of advanced techniques, with which some emergency airway providers are not familiar, as well as specialized equipment that is not always readily available in emergency departments. Bronchoscopic methods also require a significant amount of time. These factors may limit the use of this method in patients with unstable respiratory or hemodynamic profiles and in those with competing resuscitation priorities, such as an emergent need for procedural or operative intervention. Funding sources None related to this work.