The LICOX Brain Tissue Oxygen Monitor
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Severe traumatic brain injuries have been a challenge for medical community for many decades. The Center for Disease Control and Prevention defines a traumatic brain injury as ‘an injury in the head that disrupts the normal functioning of brain’. In the United States, it is estimated that almost 1.5 million cases of brain injuries are reported yearly, their scope ranging from mild to severe. Furthermore, it has been reported that approximately 50,000 peoples with traumatic brain injuries die, while 80,000 become disabled. Brain injury causes disruption of cells, axons and the integrity of cell membrane, which results in an increased disintegration of cell structures, eventually causing death. This essay provides an overview of the latest technology in oxygen monitoring of brain tissues based on the LICOX system. It also provides a thorough description of the device, how it works as well as the risks associated with its use.
For many years, traumatic brain injuries have been managed by focusing on the management of Cerebral Perfusion Pressure (CPP) and the Intra-Cranial Pressure (ICP). Monitoring has helped in providing information that greatly improves patient outcomes. However, managing and treating ICP in brain injuries does not allow for the assessment of oxygenation, which is one of the most important parameter in brain damage management. Oxygen is used at cellular level and also controls the excitatory amino acids. Therefore, its delivery and use can have a direct effect on these tissues survival. The technological advancement of oxygen monitoring in brain tissues provides information on the cellular dynamics of oxygenation. It also provides a better understanding of the effects of low oxygen state in brain.
Although there are many devices that have been used for tissue oxygen monitoring, most studies have been done using the LICOX system. It is a PbrO2 system that was developed by a German scientist, Wolfgang Fleckenstein. The LICOX brain tissue oxygen system is a triple lumen catheter that is inserted in an intracranial bolt to measure PbrO2, ICP and brain tissue temperature. The device has been in use since 1980s. It is incorporated with a monitor having a screen which displays the values of oxygen and temperature, as well as cables connecting the bed side monitor and the monitoring probes. It has pre-calibrated ‘smart’ card accompanying the probe, thus making the system calibration appealing to bedside nurses.
LICOX CMP Triple Lumen Monitoring System measures PbtO2, ICP and the brain tissue temperature. It consists of a display screen connected to two probes to measure temperature and brain tissue oxygenation and a bedside monitor. The system also consists of a separate ICP monitor which is connected to an ICP probe.
When using the LICOX, the practitioner drills a single burr hole and places an intracranial bolt. Each probe is then inserted to its port in the LICOX housing system. The placement of the probe is based on the condition of the patient, the goals of the therapy and a review of a computed tomography (CT) scan. For instance, the probes may be placed near a cerebral lesion if oxygen monitoring therapy is to be done. Areas near hematomas and infarct should be avoided. If it is difficult to place the probes on the side of the injury, they can be placed on the opposite hemisphere to enable measurement of global oxygenation (Bouma, Muizelaar, Choi, Newlon & Young, 1999). After placing the probes, a sterile dressing is applied over the bolt site. The probe cables are then connected to the monitor. The LICOX system is quickly calibrated with a smart card.
In order to obtain reliable data it is necessary to ensure precise placement of the LICOX catheters. Usually, the catheters are placed on the right-hand side of the frontal lobe because placing them on the left-hand side of the frontal lobe may lead to injury of the brain’s speech center. However, a CT scan can be employed to pinpoint the damaged area so that the LICOX catheter may be inserted into the penumbra of the injury.
After about 10 to 120 minutes, the system starts recording and displaying temperature measurements and the local cerebral oxygen. Recording is done after stabilization of the brain tissues from the micro-trauma of probe insertion. In some patients, a vebtriculostomy may be needed for cerebrospinal fluid drainage. PbtO2 measurements is recorded and tested if the probe’s accuracy is doubtable or its reading is unexpectedly low.
In order to perform an oxygen challenge test, the ventilator’s F1O2 setting is placed on 100% for 2-5 minutes. An accurately placed probe will indicate an increase in PbtO2. In case there is no response to the increase in F1O2, it is advisable to perform a CT scan to obtain the correct probe placement.
The use of PbtO2 monitoring enables practitioners to detect the occurrence of brain hypoxia in patients at risk of cerebral ischemia. Normal PbtO2 values are expected to vary from 25-50 mm Hg. Ischemia is indicated by values below 15 mm Hg, while brain cell death is indicated by values below 5 mm Hg. Oxygen delivery to tissues surrounding the probe is indicated by the oxygenation value. Monitoring of brain tissue temperature is also done since the temperature value is needed to calculate PbtO2.
The LICOX monitoring system has enabled clinical nurses to save many people’s lives. For instance, in 2001, an 18-year old boy’s life was saved due to the use of the LICOX monitoring system. The boy suffered a fatal brain injury after being involved in a car accident. The LicoX Brain Tissue Oxygen Monitor was surgically implanted through the boy’s skull via small probes. Brain tissue oxygen levels were monitored using sensors which enabled the nurses make an informed decision on the appropriate treatment protocol (Bruzzone, Dionigi, Bellinzona, Imberti & Stocchetti, 1998).
In another case, a patient called Michael was admitted to hospital having a rapidly deteriorating condition. He had a GSC score of 9/15. A CT scan of his brain showed that there was a continuous enlargement of contusions. By use of a LICOX brain tissue oxygen probe and a continuous EtCO2 monitoring, physicians were able to lower the patient’s ICP. The ICP was lowered to 28 mm Hg, the Cerebral Perfusion Pressure (CPP) was 52 mm Hg and PbtO2 was 5 mm Hg. To prevent ischemia, the physicians normalized his CO2, thus promoting his cerebral oxygenation. In two weeks’ time, the patient recovered from coma and thereafter was released from hospital. Both the patient and the nurses acknowledged that without the brain monitoring system, the patient might not have survived (Ledwith, Bloom, Maloney-Wilensky, Coyle & Polomano, 2010)
Monitoring provides essential information on the effect of various interventions in patients. Early monitoring of vital parameters in patients faced with traumatic brain injury, helps in providing useful clinical information. Brain tissue oxygen monitoring provides information on the response of intervention and its success.
By using Brain Oxygen Monitoring System, the outcomes of patients with brain injuries have been improved to greater extent. The LICOX Brain Tissue Oxygen Monitoring System provides a direct, precise and a real-time measurement of oxygen levels in brain tissue. The information from the monitoring system provides an early warning of any problem related to oxygenation that could lead to secondary injury. The combinations of LICOX with other monitoring parameters provide practitioners with information that helps them in making decisions on the intervention to use and its effectiveness.
Despite its many useful advantages brain tissue oxygen monitoring has some risks associated with its use. The use of the LICOX monitor still involves several unresolved issues. Changes on a global scope are less detectable due to the catheter being placed locally. However, the levels of oxygenation will show some potential secondary difference depending on whether the monitor is placed in damaged tissues or in healthy tissues. Furthermore, overtreatment may be observed if placement is performed in an affected area rendering the surrounding areas to be at risk. Also, hyperventilation with 100% oxygen may result in a decrease in PbtO2 reading and this may cause some secondary ischemic events in viable brain tissues.
The new Licox PMO probe provides accurate measurements but tends to under-read oxygen tension. This has been found to be more pronounced at higher temperatures. The LICOX probe has been found to under-read the temperature by approximately 0.5-0.8 degrees Celsius. Thus, caution should be taken if the temperature measured by the LICOX PMO is used to guide the decisions on treatment strategies to be used.
Scientists are still debating on where the PbtO2 should be placed. It has been found that placement at different positions accompanies various advantages and disadvantages. For instance, in assessing regional oxygenation and swelling, placement in the penumbra of the injury is recommended. However, this placement has a disadvantage because the values indicated would be reflecting on the local area. Thus, it does not indicate the condition of the uninjured brain. Clinicians use placement in the normal tissues to represent normal oxygen delivery.
Additionally, clinicians should come up with information regarding the influence of certain parameters on PbtO2 levels and the effects of oxygen monitoring on patients. A study by Minnesota Institute of Legal Education indicates the occurrence of two adverse events after brain tissue oxygen monitoring (Minnesota Institute of Legal Education, 1999). The adverse occurrence was related to hematomas which occurred after the catheter placement.According to Silver, McAllister & Yudofsky, because three probes are inserted through a bolt (oxygen, ICP and temperature probe) it is difficult to determine which of the probes causes bleeding (Silver, McAllister, & Yudofsky, 2005).
In conclusion, brain injuries are a challenge which scientists continue to face at the local and international level. Unless treated properly, head injuries result in severe mental and physical disability, as well as death. Ultimately, the prevention of secondary brain tissue ischemia is the key goal of brain monitoring. Multimodal monitoring has facilitated timely management and prevention of head injuries. Medical practitioners are constantly challenged by numerous fundamental medical problems as they choose treatment procedures. Such problems include hypoxia and hypoperfusion. Therefore, intensive care unit patients should be given unique management. In order to tackle these issues, aggressive treatment is vital to preclude secondary cerebral ischemia. LICOX provides synergistic and valuable information for evaluation which can be used both locally and globally.
The continuous evaluation on practices and the technology used in treatment of fatal brain injuries by medical practitioners, can lead to improvements in technology design and management. This would lead to discovery of cost effective interventions and treatments and, therefore, improve the outcome of treatment.
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