3rd Malaysian International MMA Medical Students Conference on Trauma

The 3rd Malaysian International MMA Medical Students conference held at Melaka-Manipal college has just concluded (2nd - 5th June 2011).

I must say that it was a huge success given the limited resources they have, especially since the committee members themselves are busy medical students, many of whom are clinical students.

I wish that more medical students from Universiti Sains Malaysia could attend, and I hope that the Persatuan Sains Perubatan USM can play a bigger and more active role in promoting the conference to the students and at the same time, actively presenting free papers. I am impressed by the quality of the papers presented by the students, from Melaka-Manipal, Universiti Malaya, IMU, Penang Medical, UNIMAS, etc. And these student presenters are not just the 4th and 5th years, but many of them are 3rd years. In fact, one of the participants who won the 2nd place of oral paper is a 3rd year student from Universiti Malaya. I am pretty impressed by the methodology and statistics that he presented. USM students should actively get themselves involved in such projects -- projects that can be simple, yet meaningful and clinically relevant (instead of just doing it for the sake of doing as a chore or pre-requisite on something irrelevant).

I talked on 2 topics: 1) Pitfalls in the management and resuscitation of a trauma patient 2) Tips on interpreting X-rays in emergency department. Besides I was also asked to be one of the judges the oral and poster presentation. Overall, the clinical students were appreciative of my talks, but from my conversation with the pre-clinical students (year 2 and some year 3s), they were lost and not able to follow through the presentation. Nonetheless, the theme of the conference is a rather clinical one: Trauma - Constructing The Future, Growing From the Past.

In my first talk, I first talked about the various sources of errors (right from pre-hospital and triaging to patient disposition) in managing patients in emergency department, particularly in a case of trauma patient. I talked about the Rasmussen model of human error -- skill-based errors, rule-based errors and knowledge-based errors, and then move on to talk about three common erroneous attitudes that can render a healthcare provider prone to error: diagnostic labeling, false negative prediction and false attribution. Most of us as doctors are prone to commit the 'sin' of diagnostic labeling. I then use detection of hemorrhagic shock in trauma as a specific model of discussion because undetected hemorrhagic shock is one of the most tragic thing that can happen to a trauma patient. I talked about the dangers of depending on a drop of BP before diagnosing hemorrhagic shock, and how we should use Shock Index, Mean Arterial Pressure as well as newer markers such as lactate level and lactate clearance to assist us in early detection of hemorrhagic shock.

In the 2nd presentation, I talked about the common useful X-rays in managing a trauma patient -- I focussed particularly on three important X-rays - Cervical, chest and pelvic X-ray. I taught them about how to interpret cervical X-ray in the context of trauma and used hangman fracture and Jefferson fracture as particular topics for discussion. I talked about chest x-ray: criteria to qualify for an adequate good chest x-ray film, and discussed on pneumothorax and traumatic aortic dissection. I reminded the students that tension pneumothorax is not supposed to the radiological diagnosis, it is a clinical diagnosis; and a doctor is supposed to "destroy" the radiological evidence of a tension pneumothorax rather than allowing it to manifest. I also talked about the tips on interpreting a pelvic X-ray -- the importance of visualizing the integrity of the three pelvic rings, tracing the integrity of iliopubic and ilio-ischial line, radiologic 'U' as well as the tear-drop sign. I talked a bit on maxillofacial X-ray, tracing the elephant trunks of Dolan lines, as well as a quick introduction on tripod # and Le Fort #. And then we run through some important things on interpreting wrist, elbow and lower limb X-ray. It is not possible to go through every details in a single talk. I also made the disclaimer that I am not a radiologist, and my talk is geared rather on correlate X-ray findings in the context of clinical setting of managing a trauma patient and therefore the talk would be pragmatic rather than technical.

Below are the slides that I used for my presentations:

Pitfalls in the management of trauma patients2

View more presentations from Chew Keng Sheng

Tips for interpreting x ray in trauma

View more presentations from Chew Keng Sheng

The Use of Mannitol in Acute Traumatic Brain Injury

Mannitol has been widely used to reduce intracranial pressure (ICP) as early as the 1960s, classically thought to be due to its hyperosmotic action to draw water from the edematous brain. This osmotic property usually takes effect in 15-30 minutes when it sets up an osmotic gradient and draws water out of neurons.

However, it was subsequently shown that there was actually less correlation between changes in ICP with changes with white matter water content (see this review article, which was written in an easy to understand way).

Severe other mechanisms were proposed to explain away how mannitol works.
One of them is the change in cerebral hemodynamics induced by mannitol. Mannitol has been proven to increase cerebral perfusion pressure (CPP) and microcirculation perfusion.

Therefore, many proposed that the primary effect of mannitol may be due to its ability to improve the rheology and thus, the reduction in viscosity.

This leads to increased flow, increased in CBF and cerebral O2 delivery.

The brain intact auto regulatory mechanism (like a loop of negative feedback) then results in vasoconstriction which decrease cerebral blood volume and lowers ICP.

Mannitol is not without disadvantages. Two notorious disadvantages:

1/ Prolonged use (continuous infusion) of mannitol molecules results in the movement of the mannitol molecules across the post-traumatic leaky blood brain barrier into the cerebral interstitial space and may thus, paradoxically, exacerbate cerebral oedema and raise ICP. Mannitol itself can directly contributes to this breakdown of the blood brain barrier.

2/ Mannitol, through its osmotic diuresis action, not only reduce ICP but may reduce intravascular volume, thereby compromising cerebral perfusion pressure, which could have a deleterious effect on outcomes for brain-injured patients.

In such cases where the blood pressure is low (e.g. hypovolemic shock), an alternative would be to use hypertonic saline. Hypertonic Saline has been shown to be a viable alternative option. The ICP reduction was sustained for at least 24 hours without repeat saline administration.

A Cochrane Review has been published regarding the role of Mannitol in Acute Traumatic Brain Injury. Click here to access.


In short, some of the salient points of the Cochrane review includes:
- At the current moment, the effectiveness of mannitol in the ongoing treatment of severe head injury remains unclear.

- There is evidence that excessive administration of mannitol may be harmful, by mannitol passing from the bloodstream into the brain, increases the ICP and worsens the cerebral edema.

- This review found a small benefit when mannitol treatment is directed by measurement of intracranial pressure compared to ‘standard treatment' (treatment without measurement of intracranial pressure).

- However, when compared to treatment with hypertonic saline, it was found that treatment with mannitol may increase the likelihood of death.

- The review found insufficient data on the effectiveness of pre-hospital administration of mannitol at the current moment.

Can We Avoid Head CT scan in Some Pediatric Patients With Head Trauma?

In a multicenter trial published in Lancet recently, Kuppermann N et al. enrolled 42,412 children (age, ≤18 years) with mild head trauma (defined as Glasgow Coma Scale score >13) to derive and validate decision rules for two separate age groups:
- those below 2 years and
- those aged 2 years and above.

In that paper, the authors highlighted the need to identify pediatric patients with very low risk of clinically important brain injuries who might not need a CT scan after all:

1. 40 - 60% of those with traumatic brain injuries seen on CT scan are from this group of patients with minor head injuries or those with GCS 14 and 15.

2. But the converse is not true - less than 10% of those with minor head injuries show traumatic brain injuries

3. Furthermore, even if there are head trauma identified, injuries needing neurosurgery are very uncommon in children with GCS scores of 14 - 15

4. The risk of radiation exposure. Ionising radiation from CT scans can cause lethal malignancies. The estimated rate of lethal malignancies from CT is between 1 in 1000 to 1 in 5000 pediatric cranial CT.

But predictive models in such cases are not new. There have been predictive models to identify low risk patients where Head CT may probably be avoided. However, in that paper, it is stated that the problems with previous predictive models:

- are limited by small sample size
- lack of validation
- no independent assessment of preverbal children (less than 2 years old)

From that study, the authors identified that:

The Decision To Avoid CT in Children with Head Trauma could be made:

A. In Children less than 2 years old if
* Normal mental status
* No scalp hematoma except frontal hematoma
* LOC<5 seconds
* Non severe mechanisms of injuries (see below for the list)
* No palpable scalp fracture
* Normal behavior

B. In Children 2 years and above if
* Normal mental status
* No LOC
* No vomiting
* Non severe mechanisms of injuries (see below for the list)
* No signs of base of skull fracture
* No severe headache

Non severe mechanisms of injuries:
# death of a passenger in the accident
# ejection of patient from the vehicle
# rollover
# pedestrian or bicyclist without helmet struck by the vehicle
# fall more than 1.5 m for children above 2 years old and more than 0.9 m for children less than 2 years
# head struck by high impact object

In the validation group of 2216 children younger than 2 years, the rule had 100% sensitivity and negative predictive value. In the validation group of 6411 children 2 years and older, the rule had 96.8% sensitivity and 99.5% negative predictive value.

Using the list of features identified, the suggested algorithm for mild head trauma in that paper:
A. In Children less than 2 years old:
Step 1:
Is the patient with altered mental status OR a palpable skull fracture: If yes - CT;
If no, then proceed to Step 2

Step 2:
Is the patient has occipital or parietal or temporal scalp hematoma OR LOC 5 or more seconds OR severe mechanism of injury OR "not acting normally" as per parent:
if yes: (use clinical judgement with the following in mind)
Observation vs CT on the basis of other clinical features include
- physician experience
- multiple versus isolated findings
- worsening symptoms of signs after emergency department observation
- age of less than 3 months
- parental preference


if not
- then CT SCAN IS NOT RECOMMENDED

B. In Children 2 years or older

Step 1:
Is the patient with altered mental status OR other signs of basilar skull #: if yes - CT

If no, then proceed to Step 2:

Step 2:
Is the patient with history of LOC OR vomiting OR severe mechanism of injury OR severe headache:

If yes, again Observation vs CT on the basis of other clinical factors including:
- physician experience
- multiple versus isolated findings (see note below)
- worsening symptoms or signs after emergency department observation
- parental preference

If no, then CT SCAN IS NOT RECOMMENDED.

Note: Patients with certain isolated findings (i.e. without other findings suggestive of traumatic brain injury) such as
- isolated LOC
- isolated headache
- isolated vomiting
- certain types of isolated scalp hematomas in infants older than 3 months
have risk of clinical important TBI (traumatic brain injuries) of less than 1%.

In general, if risk of clinically important TBI is exceedingly low, lower than risk of CT induced malignancies, then CT scans are not indicated.

In short, while using this rule may identify pediatric patients at very low risk of having clinically important TBI when ALL of the CRITERIA are fulfilled; the converse is not true. Doctors still have to use their own clinical judgment to see which patients they would order a CT scan. Nevertheless, as always, extra caution is still advisable in children younger than 3 months, in whom clinical evaluation may be less reliable.


Reference:
Kuppermann N et al. Identification of children at very low risk of clinically-important brain injuries after head trauma: A prospective cohort study. Lancet 2009 Sep 15; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S0140-6736(09)61558-0)