Term 4 Week 13 (w/c 26/11/12)
Good morning (although it is not morning for your international editor). Thank you to Team Gasclass for the invitation & the opportunity.
On your walk/ride/drive to work today, one of your tasks is to mentally prepare for your first case of the day: a 5 year old needs a brain MRI. What are your initial thoughts. One tweet at a time, please.
You have arrived in the MRI suite. The patient is not here yet & neither is the chart. The MRI requisition is from neurosurgery. In the clinical information it says, “Increasing clumsiness and falls”. A radiologist reviewed the req last week & approved it. There are no previous imaging studies. Accepting that you have not yet interviewed the child & family, how would you routinely set up for this case?
Thanks for all the input yesterday. The child & his mother have now arrived & you have learnt the following. The child was completely healthy until 18 months ago, when he fell and sustained a head injury that, Mum says, ‘needed him to have a blood clot taken out of his brain’. He was in hospital about a week. Mum says he made a good recovery. The family moved & now live in a remote rural community. Over the last 3 months, he has had several episodes of stumbling or falling to the ground. He has been referred to the nearest neurosurgical centre because of his previous surgery. They flew in yesterday. The neurosurgeon has arranged to see them after the MR, to review the findings. This is their first time in this hospital.
What are your thoughts? What else would you like to know?
Some more details from the history. His original head injury resulted from a tumble down some concrete steps. The more recent episodes have all been playground incidents. Mum is worried he may be having seizures. There is no family history of problems with anaesthesia and she says he was OK during his last surgery. He was unwell with a cold & cough all last week, but is better now – just a bit of a runny nose still & the occasional cough. On exam., he weighs 20 kg. He does have a runny nose, but his chest is clear. His airway looks normal, & his cardiovascular & neuro exams are unremarkable. He is cooperative.
Are you ready to anaesthetise him? If so, what’s your plan? If not, why not?
Thanks for today’s input. You have put him to sleep & he’s in the magnet, breathing spontaneously (O2/air/sevo) on an LMA. You’re in the control room. About 10 mins in, his end-tidal CO2 disappears & the SaO2 starts to fall.
How do you manage this scenario?
Scanning paused. You, MR tech & ODP check the child. He is apnoeic & pulseless. Now that the scanning sequence is paused, his monitored ECG is legible:
Diagnosis? Actions & priorities?
Final question for the week: if/when this child returns for a procedure requiring general anaesthesia, what additional precautions/preparations would you take/make?
Ask The Expert
Thanks to our expert Simon this week.
Children under 7 are rarely able to tolerate the immobility &/or noise required for successful MRI, so providing general anaesthesia for them is a routine & common pastime for the paediatric anaesthetist. As the availability of, and indications for MRI widen, so does the likelihood of the occasional paediatric anaesthetist needing to be prepared for such an event.
This child requires an MR head. A ‘straight-shot head’ – no contrast, no spectroscopy – takes about 15 mins & doesn’t require breath holding. It does need an unobstructed airway, or else the head moves too much. I routinely do these cases on TIVA (to avoid emergence delirium; good for kids with recent upper respiratory tract infection [URTI]), with the child breathing spontaneously on nasal prongs that have an integral CO2 sampling port. This minimises the depth of anaesthesia required to tolerate the ‘airway’, avoids airway instrumentation (good for URTI again) & makes for efficient wake up & turn around. Many people would prefer the relative security of a laryngeal mask and volatile; a bit of thought is needed about MR compatible pumps if TIVA is the plan.
Two issues complicate this case – the child’s underlying medical problem, & the co-existence of a resolving URTI.
The history of falls, and concerns about seizures, & the fact that the child has previous neurosurgical intervention made it feel like a neuro problem, but as some tweeters mused, all that falls is not neurological, & cardiovascular problems, particularly dysrhythmias – which would be on everyone’s radar, had this been an older adult – also occur in children, albeit less commonly. A pre-induction ECG could be easily justified. In the luxury of a tertiary centre, one can always call a friendly paediatric cardiologist too, if really worried. If the rhythm underlying the arrest is torsades de pointes, the unifying diagnosis of long QT syndrome becomes obvious. LQTS is a complex family of cardiac ion channelopathies that is more common than generally realised, but the condition is highly heterogeneous & so often not recognised or known about, even by the patient. Symptoms, when they occur, are due to torsades, & range from pre-syncope, through syncope & self-aborting arrest, to sudden cardiac death. In children, the syncopal episodes are often misdiagnosed as seizures. The perioperative period is extremely high-risk in untreated LQTS, as sympathetic stimulation, electrolyte disturbances, hypothermia, & some anaesthetic drugs all increase the risk of torsades. Intraoperative arrest should be treated in accordance with APLS guidelines for CPR in children; basic life support should commence immediately on recognition of no pulse. Once the non-perfusing rhythm is identified as torsades, it should be treated as for pulseless VT. MgSO4 can stabilise the myocardium once a perfusing rhythm is restored. The mainstay of long-term LQTS management is beta-blockade, which will control symptoms in the majority – but not all – cases. Additional treatments include mexilitene, cervical sympathectomy & ICD; increasingly treatment is being individualised according to genotype. Preparations for anaesthesia in the child with known LQTS include ensuring maintenance of beta-blockade, normalising & monitoring modifiable risk factors (electrolytes, temperature), avoiding QT-prolonging drugs (see http://www.azcert.org) and being set up to manage an arrest (MgSO4 drawn up; defib pads in situ, low threshold for invasive monitoring). Relevant articles for the interested reader include bja.oxfordjournals.org/content/90/3/349.full; ceaccp.oxfordjournals.org/content/8/2/67.full; www.anesthesia-analgesia.org/content/112/5/1163
The child with a recent/resolving URTI is a classic paediatric anaesthesia chestnut. The weight of published literature on the topic is considerably greater than the amount of clarity about when/when not to proceed. Everyone agrees that the risk of PRAE (periop respiratory adverse events, usually defined as any of laryngospasm, bronchospasm, desaturation or coughing) is increased up to 10-fold in the wake of a recent URTI. Classical dogma defines ‘recent’ as 6 weeks; given that the average number of colds/yr is 7, this has never been of practical help. The salient points, from more recent publications, that have helped me to make day-to-day decisions are the following: if the URTI resolved >; 2 wks ago, no problem; if the child is sytemically unwell, has thick yellow/green snot, or if there is a COUGH, these are all red flags & I would have a low threshhold for postponing; for the 80% who fall between these extremes, it’s as much art as science. There’s no convincing evidence of worse hard outcomes (death, unplanned PICU admission, unplanned overnight stay, for example), & a stormy induction or emergence is typically undetectable a few hours later; I often feel it’s worse for my coronaries than the child’s. I base my decision on a combination of personal comfort level, type of surgery planned & the parents’ attitude to risk. For children who are symptom-free on the day, but had symptoms within the last 2 weeks, there is evidence that a salbutamol nebuliser reduces PRAE. In this week’s gasclass case, I would have proceeded simply because the planned ‘surgery’ was an MRI and I am comfortable with TIVA (which there is some evidence to suggest reduces PRAE risk compared to volatile) – I would have postponed the same child having dental surgery or a tonsillectomy, both of which require airway instrumentation & surgical mucking around in a primed airway.
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