Page 212 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars

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Chapter 10
(2) deliberate continuation of resuscitative efforts (n = 21 [38%]); (3) choice and dosage of administered drugs (n = 8 [14%]); (4) fluid management (n = 8 [14%]); and (5) choice of desti- nation hospital (n = 3 [5%]). We concluded that peri-resuscitation focused echocardiography in the Nijmegen HEMS is feasible and impacts treatment decisions. Most frequently, ultra- sonography was used to support the decision to terminate the resuscitation. Also, it may be a valuable tool to explain to relatives and fellow caregivers the severity of the situation before a futile resuscitation is actually stopped.
In comparison to this observational study, an experimental study design—in which subjects would be randomized to two groups and those groups would be compared—would yield a study that is more reliable and with more internal and external validity.
Moreover, an important weakness of the three published studies in Chapter 6, 7, and 8 is that they reflect the specific situation of the Nijmegen HEMS. Due to the specific crew, skills, mode of operation, geography, and patient population, it might be difficult to gener- alize these findings to other (international) HEMS operations.
In Part IV, we discussed a novel application of ultrasonography that might prove to be useful in prehospital emergency medicine in the future: the sonographic measurement of the optic nerve sheath diameter.
In Chapter 9, we discussed 360 sonographic optic nerve sheath diameter (ONSD) measure- ments in 45 healthy volunteers. Both eyes (optic nerve sheaths) of every subject were mea- sured four times. In half of the measurements, a rigid cervical collar was randomly applied to the subjects. By impeding venous drainage from the intracranial space, the application of a rigid collar might cause an intracranial pressure (ICP) increase. Subsequently, an increased ICP will lead to an increase in the ONSD.4 The measurements in both eyes were performed simultaneously by two HEMS physicians with ample ultrasound experience, blinded for the presence of the collar. The main findings of the study were that the ONSD is higher if a collar is present than without a collar. We concluded that in healthy subjects, a rigid cervical collar causes an increase in the ONSD by impeding venous drainage from the skull, despite intact autoregulation of the cerebral circulation. We suspect that this effect may be even greater in traumatic brain injury (TBI) patients with an impaired cerebral autoregulation. Moreover, we concluded that sonographic ONSD measurements by (nonradiologist) HEMS physicians are feasible. This procedure can be applied in prehospital care and might prove to be valuable in the prehospital treatment of TBI patients with a decreased level of consciousness.