Perioperative anaphylaxis: A five-year review in a tertiary paediatric hospital

Making a diagnosis of perioperative anaphylaxis and identifying culprit drugs are diagnostic challenges. The aim of this study is to describe the perioperative presentation of anaphylaxis and results of patients who underwent allergy evaluation. This is a retrospective review of perioperative anaphylaxis of severity Grade 2 and above based on the Australian and New Zealand Anaesthetic Allergy Group criteria from 2015 to 2019 in a tertiary paediatric hospital. Data collected were demographics, clinical features, investigations and management. Of the 35,361 cases of paediatric anaesthesia, there were 15 cases of perioperative anaphylaxis, giving an incidence of four in 10,000. The median age was seven years (interquartile range four–15 years) with a male predominance of 86.7% (13/15). The severity of anaphylaxis was Grade 2 in 33.3% (5/15) and Grade 3 in 66.7% (10/15). The commonest presenting feature was hypotension (13/15, 86.7%) while the earliest symptom was respiratory change (9/15, 60.0%). Dynamic tryptase was raised in 75% (6/8) of the patients with adequate tryptase samples. Eight patients (53.3%) completed allergy testing, of whom five patients (62.5%) had IgE-mediated anaphylaxis with skin test positive to cefazolin ( n = 3), atracurium ( n = 1) and rocuronium ( n = 1). Three patients (25.0%) had non–IgE-mediated reactions with negative skin tests. Although only half the patients completed allergy evaluation, a culprit drug could be identified in 62.5%, with antibiotics being the commonest. This emphasises the need for appropriate evaluation in cases of suspected perioperative anaphylaxis.

Impact of COVID-19 on pediatric emergencies and hospitalizations in Singapore

Background Coronavirus disease 2019 (COVID-19) has impacted the provision of health services in all specialties. We aim to study the impact of COVID-19 on the utilization of pediatric hospital services including emergency department (ED) attendances, hospitalizations, diagnostic categories and resource utilization in Singapore. Methods We performed a retrospective review of ED attendances and hospital admissions among children < 18 years old from January 1st to August 8th 2020 in a major pediatric hospital in Singapore. Data were analyzed in the following time periods: Pre-lockdown (divided by the change in Disease Outbreak Response System Condition (DORSCON) level), during-lockdown and post-lockdown. We presented the data using proportions and percentage change in mean counts per day with the corresponding 95% confidence intervals (CIs). Results We attended to 58,367 children with a mean age of 5.1 years (standard deviation, SD 4.6). The mean ED attendance decreased by 331 children/day during lockdown compared to baseline (p < 0.001), attributed largely to a drop in respiratory (% change − 87.9, 95% CI − 89.3 to − 86.3, p < 0.001) and gastrointestinal infections (% change − 72.4, 95%CI − 75.9 to − 68.4, p < 0.001). Trauma-related diagnoses decreased at a slower rate across the same periods (% change − 40.0, 95%CI − 44.3 to − 35.3, p < 0.001). We saw 226 children with child abuse, with a greater proportion of total attendance seen post-lockdown (79, 0.6%) compared to baseline (36, 0.2%) (p < 0.001). In terms of ED resource utilization, there was a decrease in the overall mean number of procedures performed per day during the lockdown compared to baseline, driven largely by a reduction in blood investigations (% change − 73.9, 95%CI − 75.9 to − 71.7, p < 0.001). Conclusions We highlighted a significant decrease in infection-related presentations likely attributed to the lockdown and showed that the relative proportion of trauma-related attendances increased. By describing the impact of COVID-19 on health services, we report important trends that may provide guidance when planning resources for future pandemics.

Stability and performance of the EnSite Precision cardiac mapping system for electrophysiology mapping and ablation procedures: results from the EnSite Precision observational study

Background The EnSite Precision™ Cardiac Mapping System is a catheter navigation and mapping system capable of displaying the three-dimensional (3D) position of conventional and sensor enabled electrophysiology catheters, as well as displaying cardiac electrical activity as waveform traces and dynamic 3-D maps of cardiac chambers. Objective The EnSite Precision™ Observational Study was designed to quantify and characterize the use of the EnSite Precision™ Cardiac Mapping System for mapping and ablation of cardiac arrhythmias in a real-world environment and to evaluate procedural and subsequent clinical outcomes. Methods 1065 patients were enrolled at 38 centers in the U.S. and Canada between 2017–2018. Eligible subjects were adults undergoing a cardiac electrophysiology mapping and radiofrequency ablation procedures using the EnSite Precision™ System. Results Of 989 patients who completed the protocol, a geometry was created in 936 (94.7%). Most initial maps were created using Automap (n=545, 67.0%) or a combination of Automap and manually mapping (n=151, 18.6%). Median time to create an initial map was 9.0 min (IQR 5.0–15.0), with a median number of used mapping points per minute of 92.7 (IQR 30.0–192.0). During ablation, AutoMark was used in 817 (82.6%) of procedures. The most frequent metrics for lesion color were Impedance Drop or Impedance Drop Percent (45.5% combined), time (23.9%) and average force (14.2%). At Canadian sites where LSI was an option, it was used as the color metric in 87 (45.8%) of cases (10.6% overall). The EnSite System was stable throughout 79.7% (n=788 of 989) of procedures. Factors affecting stability were respiratory change (n=88 of 989, 8.9%), patient movement (n=73, 7.4%), CS Positional Reference dislodgement (n=32, 3.2%), and cardioversion (n=19, 1.9%). Conscious sedation was used in 189 (19.1%) of patients. Acute success was reached based on the pre-defined endpoints for the procedure in 97.4% (n=963) of cases. Conclusion In a real-world study analysis, the EnSite Precision™ mapping system was associated with a high prevalence of acute procedural success, low mapping times, and high system stability. Funding Acknowledgement Type of funding source: None

Influence of Tidal Volume on Pulse Pressure Variations in Hypovolemic Ventilated Pigs with Acute Respiratory Distress-like Syndrome

Background Sensitivity and specificity of respiratory change in pulse pressure (DeltaPP) to predict preload dependency has been questioned at small tidal volumes (VT) in critically ill patients suffering from acute respiratory distress syndrome (ARDS). We studied DeltaPP in pigs with ARDS-like syndrome during reversible hemorrhagic shock. Methods Prospective, observational animal study in a Laboratory Investigation Unit. Sixteen deeply sedated mechanically ventilated pigs were successively ventilated with VT of 10 ml/kg at a respiratory rate of 15 breaths/min (RR15) and VT of 6 ml/kg at RR15 and RR25. ARDS-like syndrome was produced by lung lavage in eight pigs (ARDS group). Severe hemorrhagic shock was induced by removal of 40% of total blood volume followed by restoration. Results After bleeding, in the control group ventilated with a VT of 10 ml/kg, DeltaPP increased from 8.5 (95% confidence interval [CI], 7.1 to 9.9%) to 18.5% (CI, 15.3 to 21.7%; P&lt;0.05). In the ARDS group, this index increased similarly, from 7.1% (95% CI, 5.3 to 9.0%) to 20.1% (CI, 15.3 to 24.9%; P&lt;0.05). In control lungs, reduction in VT from 10 to 6 ml/kg reduced the DeltaPP reaction by 40%, although it remained a statistically valid indicator of hypovolemia regardless of the RR value. In contrast, in the ARDS group, DeltaPP was an unreliable hypovolemia marker at low VT ventilation, regardless of the RR value (p=not statistically significant). Conclusions The present study suggests that DeltaPP is a reliable indicator of severe hypovolemia in pigs with healthy lungs regardless of VT or RR. In contrast, in pigs with ARDS-like syndrome ventilated with small VT, DeltaPP is not a good indicator of severe hemorrhage. However, in this setting, indexing DeltaPP to respiratory changes in transpulmonary pressure allows this marker to significantly indicate the occurrence of hypovolemia.

The respiratory change in preejection period: a new method to predict fluid responsiveness

The accuracy and clinical utility of preload indexes as bedside indicators of fluid responsiveness in patients after cardiac surgery is controversial. This study evaluates whether respiratory changes (Δ) in the preejection period (PEP; ΔPEP) predict fluid responsiveness in mechanically ventilated patients. Sixteen postcoronary artery bypass surgery patients, deeply sedated under mechanical ventilation, were enrolled. PEP was defined as the time interval between the beginning of the Q wave on the electrocardiogram and the upstroke of the radial arterial pressure. ΔPEP (%) was defined as the difference between expiratory and inspiratory PEP measured over one respiratory cycle. We also measured cardiac output, stroke volume index, right atrial pressure, pulmonary arterial occlusion pressure, respiratory change in pulse pressure, systolic pressure variation, and the Δdown component of SPV. Data were measured without positive end-expiratory pressure (PEEP) and after application of a PEEP of 10 cmH2O (PEEP10). When PEEP10 induced a decrease of >15% in mean arterial pressure value, then measurements were re-performed before and after volume expansion. Volume loading was done in eight patients. Right atrial pressure and pulmonary arterial occlusion pressure before volume expansion did not correlate with the change in stroke volume index after the fluid challenge. Systolic pressure variation, ΔPEP, Δdown, and change in pulse pressure before volume expansion correlated with stroke volume index change after fluid challenge ( r2 = 0.52, 0.57, 0.68, and 0.83, respectively). In deeply sedated, mechanically ventilated patients after cardiac surgery, ΔPEP, a new method, can be used to predict fluid responsiveness and hemodynamic response to PEEP10.

Respiratory response to activation or disinhibition of the dorsal periaqueductal gray in rats

The neural substrates mediating autonomic components of the behavioral defense response have been shown to reside in the periaqueductal gray (PAG). The cardiovascular components of the behavioral defense response have been well described and are tonically suppressed by GABAergic input. The ventilatory response associated with disinhibition of the dorsal PAG (dPAG) neurons is unknown. In urethane-anesthetized, spontaneously breathing rats, electrical stimulation of the dPAG was shown to decrease the expiration time and increase respiratory frequency, with no change in time of inspiration. Baseline and the change in diaphragm electromyograph also increased, resulting in an increase in neural minute activity. Microinjection of bicuculline methobromide, a GABAA-receptor antagonist, into the dPAG produced a similar response, which was dose dependent. Disinhibition of the dPAG also produced a decrease in inspiration time. These results suggest that GABAA-mediated suppression of dPAG neurons plays a role in the respiratory component of behavioral defense responses. The respiratory change is due in part to a change in brain stem respiratory timing and phasic inspiratory output. In addition, there is an increase in tonic diaphragm activity.