Category Archives: Pediatrics

Photoplethysmographic pulsus paradoxicus!

Say that three times fast.

We had a challenging case in our emergency department recently involving a patient with a self-inflicted stab wound to the anterior chest, which resulted in a pericardial effusion, prompting concern for the development of tamponade. A challenging element of the case involved thinking about the patient’s stability, and the urgent/emergent need for operative intervention v percutaneous intervention v observation — how could we determine whether this patient was, in fact, in cardiac tamponade or on their way towards developing this condition?

A classic teaching is to assess for a pulsus paradoxus, or an exaggerated decrease in the arterial blood pressure with inspiration. Traditionally this is done using a stethoscope and manual blood pressure cuff (I will not try to spell the S-word). If the difference in BP between the first expiratory Korotkoff sound and the first Korotkoff sound that no longer disappears with inspiration (the pulsus) is greater than 10 mmHg, a pulsus paradoxus is present.

Has anyone ever checked for one of these, or has this technique become like with many other physical exam findings, something that people are aware of but don’t really know how to check for? I’m not sure — I personally have never checked for one, and reach for the ultrasound when trying to risk stratify patients with pericardial effusions. Is there an easier way, or one that doesn’t require PoC echo?

These authors evaluate the utility of pulse oximetry, or plethysmography in the assessment of tamponade. They suggest that the difference between the inspiratory decrease in the magnitude of the waveform and the expiratory increase has been shown to correlate with intraarterially measured pulsus paradoxus. Unfortunately it turns out that this finding is not pathognomic for cardiac tamponade — it is linked to a number of other conditions (e.g. elevated intrathoracic pressures from asthma), and may be absent in patients who actually have tamponade physiology.

The most relevant article to this particular case is probably the study from Stone et al., “Respiratory changes in the pulse-oximetry waveform associated with pericardial tamponade.” from 2006, when they measured phasic respiratory variability in the pulse-oximetry waveform of patients undergoing aspiration of pericardial effusions. They found that the degree of respiratory variability in the pulse-oximetry waveform was significantly increased in these patients compared to effusion-less patients, and increased with the hemodynamic consequences of the tamponade. When the effusions were aspirated and drained, the variability disappeared.

So, is this something to hang your hat on? Probably not useful entirely for ruling OUT pericardial tamponade, but in a patient with an effusion if you’re asked by the consultant you wake up in the middle of the night whether you’ve checked for a pulsus yet, this might be an easier way than busting out your manual BP cuff and Googling how to check one the traditional way.


Clark JA1, Lieh-Lai M, Thomas R, Raghavan K, Sarnaik AP. Comparison of traditional and plethysmographic methods for measuring pulsus paradoxus. Arch Pediatr Adolesc Med. 2004 Jan;158(1):48-51. PMID: 14706958. [PubMed] [Read by QxMD]

Duration of symptoms of respiratory tract infections in children

From the BMJ, we have a very interesting systematic review evaluating the duration of symptoms in children seen in the ED (or A&E, if you will) for fairly minor complaints: otitis media, acute cough, sore throat, and common cold. In my time in the pediatric ED, I’ve noticed that a not-insignificant number of visits are repeat visits for persistent symptoms in well-appearing children who were seen and discharged from the ED within the last week or so. The parents are often concerned that the cough has still not gone away, or that the child’s breathing at night still sounds funny to them — these are not different symptoms than the child was originally evaluated for, but I thought it was possible that better anticipatory guidance in terms of the duration of symptoms parents could expect might result in fewer of these “bounce

So what did the authors at BMJ find? In 90% of children, earache was resolved by seven to eight days, sore throat between two and seven days, croup by two days, bronchiolitis by 21 days, acute cough by 25 days, common cold by 15 days, and non-specific respiratory tract infections symptoms by 16 days.

21 days of cough for bronchiolitis and 25 days for non-bronchiolitis URIs? That is way longer than what I hear when parents are being discharged — I am no less guilty of underselling the duration of symptoms than others. It’s a tough question to answer, right? “How much longer will this last?” — Prognostication is always the hardest part of medicine, whether you’re talking to the dying cancer patient or to the parents of the child with the perpetually stuffy nose and inflamed upper airways. Well, I personally intend to try to provide parents with a more evidence-based answer for the rest of this season– something along these lines: “Longer than you can possibly imagine. Most kids will have a cough for three weeks or more, and many will seem like they go the entire winter without getting better. But as long as they’re eating, drinking, pooping, peeing, moving about and more or less acting like a slightly-more-congested-and-therefore-irritable version of themselves, that’s okay!”

It’s a tough balance. You wouldn’t want to dissuade parents from seeking medical attention (ideally from their PMD) if the child doesn’t get better in a reasonable amount of time, but it’s very difficult knowing what that time is for them. Moral of the story: encourage that follow up visit with the PMD, and make sure to give thorough and explicit return precautions accounting for the myriad reasons we *do* need to see these patients back ASAP.


Thompson M1, Vodicka TA, Blair PS, Buckley DI, Heneghan C, Hay AD; TARGET Programme Team. Duration of symptoms of respiratory tract infections in children: systematic review. BMJ. 2013 Dec 11;347:f7027. PMID: 24335668. [PubMed] [Read by QxMD]

ALTE Badness – Who to Admit?

Kaji et al. bring us “Apparent life-threatening event: multicenter prospective cohort study to develop a clinical decision rule for admission to the hospital”, which is pretty much what it sounds like. What did it leave us with? The study looked at 832 kids presenting w/ ALTE to four different sites and identified three variables (obvious need for admission, significant medical history, >1 apparent life-threatening event in 24 hours) that identified most (but not all!) infants with apparent life-threatening events necessitating admission. I’ll just put that here again, in case you missed it: one of the conclusions was that obvious need for admission was a variable that predicted need for admission. Huh.

That point aside (and really, it’s a more interesting conclusion than it sounds like — meaning, that the ALTE kids who look sick when they get there tend to go on to have bad outcomes (hypoxia, apnea, bradycardia that is not self-resolving, or serious bacterial infection) discovered while in-hospital or receive some sort of “significant intervention” during their hospitalization that, retrospectively, necessitated admission. To be fair, the variable “obvious need for admission” was defined in the paper as occurring “if the child needed supplemental oxygen for non–self-resolving hypoxia, intubation, ventilation, cardiopulmonary resuscitation (CPR), intravenous antibiotics for a confirmed serious bacterial infection, or antiepileptic drugs (for status epilepticus); had hemodynamic instability warranting continuous intravenous fluids or vasopressors; or had a positive test result for respiratory syncytial virus or pertussis in the setting of an apparent life-threatening event.”

It would be difficult to argue against admitting any patient in one of these contexts (with the possible exception of non-self-solving hypoxia, which in the bronchiolitic child who is otherwise well-appearing should probably not serve in isolation as a reason to admit), and I imagine that such events occurring in the context of an ALTE are even more clear-cut indications for continued observation and management. Still, this is a nice body of literature showing that even with 84% of patients appearing well at time of ED presentation, 23% go onto need serious interventions once hospitalized — which is to say, being well-appearing at presentation does not protect against the need for escalation of care or therapeutic interventions soon thereafter.


Kaji AH1, Claudius I, Santillanes G, Mittal MK, Hayes K, Lee J, Gausche-Hill M. Apparent life-threatening event: multicenter prospective cohort study to develop a clinical decision rule for admission to the hospital. Ann Emerg Med. 2013 Apr;61(4):379-387. PMID: 23026786. [PubMed] [Read by QxMD]

Bronchiolitis and the Risk of Apneic Events – Risk Stratification Tool?

Walsh et al. published “Derivation of Candidate Clinical Decision Rules to Identify Infants at Risk for Central Apnea.” in Pediatrics in November, which attempted to derive several CDRs and compare them for identifying risk of central apnea in pediatric patients with respiratory illness. Of course, for an outcome as rare as central apnea in a population that usually does very well, almost any set of criteria you apply to patients will leave you with a rule that has a very high NPV — so what did they find?

The group analyzed 990 ED visits for 892 infants. Central apnea subsequently occurred in the hospital in 41 (5%) patients. Three candidate CDRs were generated by different techniques, and the results were analyzed and yielded the following risk factors: Parental report of apnea, previous history of apnea, congenital heart disease, birth weight ≤2.5 kg, lower weight, and age ≤6 weeks all identified a group at high risk for subsequent central apnea. All CDRs and RFs were 100% sensitive (95% confidence interval [CI] 91%-100%) and had a negative predictive value of 100% (95% CI 99%-100%) for the subsequent apnea.

Candidate clinical decision rules from Walsh et al.

Candidate clinical decision rules from Walsh et al.

The third tool, not shown above, is a computationally-intensive algorithm that used a Random Forest method to generate a risk stratification. Much like the recently-published work on sepsis using Big Data strategies, this had a better AOC than either of the above two, which are much simpler and can by applied by clinicians. This rule and others like it may have a future in the form of electronic heath record-embedded decision support, but are less amenable to being remembered and applied by the physician at the point of care when making a disposition decision.

It is important to note some caveats about this and the results — particularly the prevalence of apnea in this population, which accepted parental reports of apneic events as part of the numerator (i.e. not just monitored and captured events), but it still underscores the idea that parental concern should be your concern until proven otherwise.

Anyway, all this to say, bronchiolitis-related apnea is a terrible outcome but a very rare outcome. Admission for observation may be considered in high-risk patients, and should be discussed with parents. If a hospital doesn’t have apnea monitoring, is it still reasonable to admit these kids for observation? That’s not really germane to the studies published here, but came up recently on one of my rotations — I guess if a respiratory arrest happened, it would be better to be in a setting where a response could occur swiftly and with full capabilities, but I don’t know that such an admission is better than sending the kid home with parents who will likely be steadfast bedside observers of the child’s respiratory status throughout the night. That question will have to wait for another study, I suppose.


Walsh P1, Cunningham P2, Merchant S3, Walker N3, Heffner J3, Shanholtzer L3, Rothenberg SJ4. Derivation of Candidate Clinical Decision Rules to Identify Infants at Risk for Central Apnea. Pediatrics. 2015 Nov;136(5):e1228-36. PMID: 26482666. [PubMed] [Read by QxMD]