Brain Tissue Oxygen Monitoring in Severe Brain Injury, II (2003)

The authors describe how critical care teams integrate interventions to maintain adequate brain oxygenation as patients progress through hospitalization. Critical-care algorithms are defined and a case study is presented, allowing readers to analyze the interventions used to optimize a patient’s recovery.Research related to the effects of certain interventions on brain tissue oxygen monitoring was presented in part I: “Research and Usefulness in Critical Care.”1 In this article, we continue the discussion of brain tissue oxygen monitoring and its effects on patients with severe traumatic brain injury. First, we describe how the interventions of critical care teams are integrated to maintain adequate brain oxygenation as patients progress through the critical phases of hospitalization. Second, we define critical-thinking algorithms that allow the team to implement sequenced interventions to maintain patients with traumatic brain injury in the zone of control. Last, we apply that theoretical and practical information to an actual case study, allowing readers to follow a case and analyze the interventions used to optimize a patient’s recovery.The Guidelines for the Management of Severe Brain Injury2 describe evidence-based treatment that includes a discussion of appropriate management of intracranial pressure (ICP) and cerebral perfusion pressure (CPP). An algorithm outlines a tiered approach to avoid secondary injury.2 The literature review in the guidelines and a review of the Traumatic Coma Data Bank clearly indicate that the avoidance of early hypoxia and hypotension and a rapid resuscitation and evacuation of intracranial hematomas are necessary and could improve the chances for a good outcome.3Data presented in the guidelines suggest that a CPP of 70 mm Hg or greater is sufficient for adequate perfusion of neuronal cells in the absence of other brain pathology.2 The guidelines may enable patients to derive even greater benefit from a targeted approach to therapies that includes monitoring the partial pressure of oxygen in brain tissue (Pbto2) because traumatic brain injury can be such a multifaceted problem.4Resuscitating patients with severe brain injury and stabilizing and maintaining their condition require an organized critical care team armed with protocols that define interventions to optimize cerebral oxygenation and reduce ICP. Targeting therapy to maintain ICP at less than 20 mm Hg has been the reference standard for years. With the introduction of methods for monitoring oxygen levels in brain tissue, interventions must take into account this important new variable. The goal of the critical care team is to balance ICP and Pbto2 throughout the critical phases of patients’ hospitalization. In the following section, we present interventions that increase Pbto2 and integrate them into the overall management of patients with severe traumatic brain injury.The team’s focus on brain resuscitation begins in the emergency department and continues through diagnostic radiology and operating room procedures. During this time, invasive monitors for evaluating ICP and Pbto2 are not in place. Establishing physiological goals for each phase will assist the team in targeting therapies to each patient’s situation until more definitive treatment can be delivered (Table 1).Initial interventions in the emergency department include protecting the airway and supporting oxygenation and ventilation. Patients admitted with a score between 3 and 8 on the Glasgow Coma Scale (GCS) require airway protection with endotracheal intubation.2 Stabilization of the cervical spine during the airway manipulation is essential. Because laryngeal manipulation during intubation has untoward effects on ICP, use of a rapid-sequence intubation regimen allows the team to administer medications and sequence airway maneuvers in such a way as to complete the procedure while minimizing increases in ICP5,6 (Table 2). By combining the sequenced timing of the medications and airway intubation, elevations in ICP can be decreased or minimized. Assessment of the correct placement of the endotracheal tube and the adequacy of oxygenation and ventilation is essential. The fraction of inspired oxygen (Fio2) should be maintained at 100% until respiratory parameters can be assessed definitively via arterial blood gas analysis. The Paco2 greatly affects the ICP and the size of the cerebral vasculature. A Paco2 less than 35 mm Hg produces cerebral vaso-constriction, reducing ICP, but may lead to decreases in oxygen delivery to the brain. Therefore, every effort should be made to maintain the Paco2 between 35 and 45 mm Hg during the early resuscitation period until the team can assess how decreasing Paco2 will affect Pbto2.Restoration of adequate blood pressure in the emergency department is important for maintaining perfusion to the brain. Patients who experience episodes of hypotension in the early phases of trauma have more morbidity and mortality than do patients whose blood pressure is normal.3 Therefore, every effort should be made to provide adequate fluids in the early phases to maintain a mean arterial pressure greater than 90 mm Hg.2 Multiple interventions (eg, physical examination, initial radiography, and placement of catheters) are done during this phase in an attempt to identify primary and secondary injuries and to provide a means to intervene with and monitor the patient.Rapidly obtaining radiographic studies, including computed tomography (CT) scans of the brain and radiographs of the cervical spine, chest, and pelvis, assists in detecting injuries. Once severe brain injury has been diagnosed on the basis of findings on clinical examination and radiographic evidence, the patient is taken to the operating room for definitive intervention.Once again, the goals of the operative phase must be understood by the entire team (Table 1). Placement of an ICP monitor and a brain tissue oxygen monitor as well as central venous monitoring assists the team in meeting the needs of the injured brain during this critical phase. Specific operative interventions, craniotomy for evacuation of acute hemorrhages or craniectomy, help reduce ICP and improve cerebral oxygenation.7,8 Careful attention to coagulopathies that develop intraoperatively is important. Prompt attention to correcting the specific deficiency must occur, with administration of blood products, platelets, fresh-frozen plasma, and/or cryoprecipitate.Because of the possibility of multiple operative procedures and a prolonged period in the operating room, it is helpful to have the intensive care unit (ICU)/trauma nurse present during this phase. This nurse works with the anesthesiologist by helping to intervene when ICP and Pbto2 change rapidly. This nurse also assists with interventions and critical documentation so that an accurate record is kept of all of the interventions that occur during the operating room phase.The hemodynamic status of many patients is unstable postoperatively. During transfer to the ICU, it is helpful to use a battery-operated ventilator. Doing so ensures that the ventilator mode remains stable. If a manual resuscitation bag is used, the person administering breaths may be inconsistent in delivering the correct number of breaths per minute, a situation that can lead to hypocapnia or hypercapnia.The stabilization period, the first few hours in the ICU, is a critical period during which the patient must be quickly brought into the zone of control. Members of the critical care team must understand the effect that each intervention has on Pbto2 and ICP. Use of a standardized protocol with team interventions provided via standardized physician orders will help the team prioritize and orchestrate interventions while continuing to stabilize the patient’s condition (Table 3). Pbto2 is influenced by multiple factors8–18 (Table 4). Critical care nurses must understand how to manipulate each factor and the appropriate sequence in which to initiate changes in order to balance oxygen delivery to the brain and ICP. Maintaining these therapies until brain swelling is reduced and brain oxygenation stays within the normal range is the primary focus of critical care nurses.When the patient arrives from the operating room, the team rapidly confirms that the ventilatory support is correct, connects all hemodynamic monitors, assesses the patient’s condition, and determines the priorities in care. During the admission, the ICU nurse should ask if a CT scan of the brain was obtained postoperatively to verify location of the LICOX catheter. This question is important because in order to obtain meaningful readings, the catheter must be positioned in viable tissue. If the catheter is in a contusion, a blood clot, or nonviable brain parenchyma, then the reliability of the readings obtained via the catheter are questionable. Once the patient is settled, then the team’s priorities are established. During this initial ICU phase, the ICU nurse also quickly assesses the following parameters: Pbto2, mean arterial pressure, ICP, CPP, pulmonary capillary wedge pressure, central venous pressure, cardiac index, oxygen saturation, Paco2, and body temperature. The team must bring these values under control. The goals for this phase are to maintain Pbto2 greater than 20 mm Hg and ICP less than 20 mm Hg.If the Pbto2 is less than 15 mm Hg, the team should ensure that the Fio2 administered via the mechanical ventilator is 100%, even if the oxygen saturation is 100%, because the driving force that moves oxygen into tissue is the gradient between the dissolved oxygen in the blood and brain tissue oxygen levels. Supranormal levels of oxygen may be needed for the first few hours during stabilization in the ICU.10 The Fio2 can be slowly decreased once the Pbto2 is greater than 20 mm Hg and stable. Next, ICP and Paco2 are assessed. These 2 variables must be considered together when their effect on Pbto2 is evaluated.13,19 If the ICP is less than 20 mm Hg and Pbto2 is less than 20 mm Hg, the Paco2 is allowed to increase up to 45 mm Hg so long as the ICP remains less than 20 mm Hg. If ICP is greater than 20 mm Hg and Pbto2 is less than 20 mm Hg, cerebrospinal fluid is drained if a ventriculostomy was done. Increasing the Paco2 might worsen the ICP, but it will increase the Pbto2.13,19 In efforts to increase Pbto2, ICP is considered in relation to mean arterial pressure and CPP. If the CPP is less than 70 mm Hg, efforts should be made to increase the mean arterial pressure.17 If the pulmonary capillary wedge pressure is less than 8 mm Hg, a bolus of isotonic sodium chloride solution or 250 mL of 5% albumin should be given. If the hematocrit is less than 0.33, packed red blood cells are administered. Then, the patient’s fluid volume status should be reassessed. Fluids should be given until the pulmonary capillary wedge pressure is greater than 8 but less than 12 mm Hg. If the patient is euvolemic and the CPP is still low, a vasopressor may be given.Next, the Pbto2, CPP, and ICP are reevaluated. If Pbto2 is greater than 20 mm Hg and ICP is less than 20 mm Hg, the CPP should be maintained at that level. The minimal CPP requirement of patients with severe traumatic brain injury will change and must be evaluated frequently. Once CPP is optimized, the ICP and Pbto2 are reevaluated. If the ICP is still greater than 20 mm Hg, 0.25 to 1.0 g/kg mannitol may be given as an intravenous bolus and/or propofol may be infused intravenously at a rate of 10 to 100 μg/kg per minute. During this time, administration of analgesic and sedative agents should be started and then maintained continuously. Cooling measures should be used to maintain the patient’s body temperature at 36°C to 37°C.If Pbto2 is greater than 20 mm Hg on admission to the ICU, assessment of ICP and the other factors will provide information for planning strategies for care. If Pbto2 and ICP are normal, then the patient’s condition can be stabilized by using an Fio2 of 30% to 40% and a Paco2 of 35 to 40 mm Hg, and efforts can be made to determine the optimal CPP. A CPP of 55 to 60 mm Hg may be acceptable if the Pbto2 is greater than 20 mm Hg without supplemental increased oxygen support.8,14 The fluid volume status should be assessed, and euvolemia should be maintained. Administration of analgesic and sedative agents should begin. The patient’s condition should be evaluated frequently.If ICP is elevated but Pbto2 is normal, then efforts should be made to reduce ICP. These efforts include draining cerebrospinal fluid, decreasing Paco2 so long as the Pbto2 is greater than 20 mm Hg, optimizing the mean arterial pressure with fluids and vasopressors, and administering sedatives, analgesic agents, and/or an osmotic diuretic. If the ICP remains greater than 20 mm Hg, consultation with the physician team may lead to an emergent CT scan, orders for propofol and/or barbiturates, and, possibly, a craniectomy. The optimal CPP for a patient with an elevated ICP and normal Pbto2 must be determined and may exceed the “recommended” CPP of 70 mm Hg. In some instances, patients might require a CPP of 90 to 110 mm Hg to decrease the ICP.Once the patient’s condition is stabilized and the parameters have reached the goals for then the of the critical care team must be organized to the situation under control. a patient continue without elevations of ICP or decreases in Therefore, the ICU nurse must the patient and the interventions with other team The ICU team a of the patient’s parameters should be in order to maintain all parameters within the goal for the the interventions in 3 ensures an organized approach to patients’ algorithms are helpful in team in (Table The interventions are and allow the team to through the situation in a standardized that primary interventions are done more The patient’s status will the changes are to in the early phases of care and to in the the during all phases of the patient’s is the pulmonary to and the use of are drained with a or or should within hours of admission to the of and the of The patient’s should be maintained in an by a or to of can be by using of the or and using range of The of is reduced by the and and the patient has the patient’s of care will Once the patient has a normal ICP and Pbto2 with for interventions, then the team can to the patient therapy 1). The more interventions are and the patient is slowly brought of the the theoretical information presented is to the of findings from to the clinical In the following case study, we to integrate into a was driving from at when the and an was not a and not have an at and condition as a prolonged clinical examination the airway to obtain a blood score for for and for with and interventions at the the was was a critical trauma patient and was to the trauma in the emergency department in critical supporting airway by using a manual resuscitation bag and 100% Because of to maintain a and a score of was by using a rapid-sequence was with 100% and the was maintained at 35 mm Hg. assessment of and a blood pressure of 70 mm Hg. started intravenous catheter. A intravenous catheter was started by using a and was to a to allow intravenous administration of fluids and blood status a score of mm in and An tube to a catheter for and an arterial catheter for monitoring blood pressure hematocrit was radiographs of the pelvis, and By the of the emergency department phase, of isotonic sodium chloride solution and of packed red blood was by the trauma team to the radiology department for an emergent CT scan at A battery-operated ventilator was used during to maintain levels. The CT scan of the brain cerebral a of intracranial and multiple 2). resuscitation because of blood pressure mm Hg The goal was to a mean arterial pressure of at 90 mm Hg. an of packed red blood cells and of fresh-frozen consultation in a to to the operating trauma quickly a pulmonary catheter for of cardiac and a oxygen saturation catheter. The mean arterial pressure from mm Hg at the of the case to to 60 mm Hg during the first a and the of The anesthesiologist and trauma ICU nurses multiple of red blood platelets, fresh-frozen plasma, and into was administered intravenously in an attempt to the goal of a mean arterial pressure of 90 mm operative team the with placement of an ICP catheter and a LICOX brain tissue oxygen catheter. The initial ICP was 35 mm Hg, a from the normal of less than 20 mm Hg. The Pbto2 was 3 mm Hg, a critical Pbto2 is 20 to 35 mm During the the ICP increased to mm Hg and the Pbto2 at 3 mm Hg. The team was using multiple interventions during this period in an effort to reduce ICP and improve administered an Fio2 of 100%, maintained the at 35 mm Hg, administered analgesic agents and and to increase the mean arterial pressure to greater than mm Hg but for a to a when the team was to the ICP. By the the was the ICP reached 60 mm Hg. the was and the the ICP decreased to 8 or 10 mm Hg and the Pbto2 increased to 20 to 45 mm Hg. Because of the unstable and critical condition, to stabilize the the a on the in the for to be once the patient reached the a so the quickly The physician team not to the because of critical By the the operative procedures the ICP once increased to more than 40 mm Hg, and the Pbto2 decreased to 2 mm Hg 3). multiple interventions, the team could not increase the Pbto2 to more than 2 mm Hg or decrease the ICP to less than 40 mm Hg. condition was unstable and the operative was to the ICU for definitive care. A battery-operated ventilator was used during The of multiple intravenous for CPP cerebral perfusion pressure, which is mean arterial pressure ICP, intracranial pressure Pbto2, partial pressure of oxygen in brain tissue delivering fluids and and the the The ICU team the from the trauma ICU nurses to condition was score was and and mm in and ICP was greater than 40 mm Hg, and Pbto2 was between and mm Hg. The ventilator was to maintain an Fio2 of 40% and a pressure and rate to maintain the at 35 mm Hg. administration of fluids and was In to was and in an effort to increase the CPP to 70 mm Hg. Because the ICP values between 40 and mm Hg, the CPP was 40 to mm Hg. The team was to bring into the zone of or the goals that been for this phase, which maintaining an ICP less than 20 mm Hg and a Pbto2 greater than 20 mm hours of admission to the ICU, the team to The ICU nurse and respiratory care to increase the Fio2 to a change that in an increase of the Pbto2 to mm Hg within The Fio2 was increased to 100%, and the Pbto2 increased to mm Hg within of that Once the Pbto2 was the team on decreasing the ICP 4). fluid and vasopressor the CPP in the range of 40 to mm Hg, than the goal of 70 mm Hg. was to the and in an attempt to increase ICP between 40 and mm Hg. was administered and the of propofol was increased to 100 μg/kg per fluid was drained at per in an effort to reduce ICP. all these interventions, the ICP not the Pbto2 was greater than 20 mm Hg, the team to decrease the Fio2 from the Fio2 was the Pbto2 decreased to less than mm Hg. Use of 100% Fio2 was to the Pbto2 greater than 20 mm Hg. support was interventions in the first hours on optimizing oxygen levels and ICP. the Pbto2 goal was the ICP was elevated to 40 to 60 mm Hg. The team was by the to maintain Pbto2 but with the ICP. was in for a team to focus their interventions on decreasing the ICP to less than 20 mm Hg and maintaining the Pbto2 at greater than 20 mm Hg. During the ICP between 40 and mm Hg of cerebrospinal fluid, of at to mm Hg, CPP administration of mannitol and use of of propofol The CPP was maintained between and 60 mm Hg with fluid therapy and of and as intravenous the Pbto2 decreased to mm Hg the Fio2 at hematocrit was so the 2 of packed red blood The CPP increased by mm Hg, but the Pbto2 increased from to mm Hg. the red cells Pbto2 when the Fio2 was decreased to less than to decrease the Fio2 on it that Fio2 was the intervention that the Pbto2 greater than 20 mm Hg. change in status mm in and or or was a CT scan of the brain an of blood the on the the been done. critical and the team on with care. The to the operating room and the The ICP decreased from values between 40 and mm Hg to values between 20 and mm Hg CPP and was maintained at greater than 70 mm Hg. During the Pbto2 with levels of Paco2 and Fio2 as well as decreases in CPP of Fio2 with between and Paco2 changes from to mm Hg in a decrease of 8 mm Hg in vasopressor support was maintained. change in the findings during this through brought more to this the team been to because of ICP the multiple and unstable and respiratory The of respiratory was first by decreases in the Pbto2 from values between 20 and mm Hg to values of 8 to 10 mm Hg by increases in airway on the ventilator. was given 100% Fio2 to increase the In therapy was on this therapy increase the Pbto2 to 15 mm Hg. maintain hemodynamic condition, was more vasopressor and CPP values maintained at greater than 60 mm Hg with ICP values from 15 to mm Hg. in an attempt to in the By changes in the and pulmonary a of to to and to a central pulmonary status The therapy was and the Fio2 was at ICP was and was maintained at less than 20 mm Hg with of cerebrospinal less vasopressor support and been from the intravenous of and The was related to the Paco2 levels needed to maintain Pbto2 greater than 20 mm Hg. Because ICP was low, the team allowed the Paco2 to increase until the Pbto2 was maintained at greater than 20 mm Hg. The Paco2 from 45 to mm Hg during this status to to and in at status to and the was done in an to or elevations in ICP 1). During the of was all to the operating room on for of the and the LICOX catheter was score was and was with on the and on the to the operating room for a placement of and and of the and therapies By was from the and was to the unit by to and nurses and as the started to follow was up in a at 3 a was of used a to the been to was evaluated for acute was to acute on and was on 3 a and the was to and in has been and is in of of patients with severe traumatic brain injury have been greatly through the use of oxygen monitoring and the of the Brain of Guidelines for the Management of Severe all for patients with severe traumatic brain injury are for at the patients are from the In order to maintain and established. The the of 3 to of findings on CT scan and/or clinical examination, and 8 or brain within hours of ICU admission, less than 8 and normal findings on CT scan and of or a injury to of we the guidelines for traumatic brain injury and brain oxygen monitoring in the of in the and the the have (Table care for patients with critical brain injuries a team that the the injury and to together to the goals at each phase of Brain oxygen monitoring to when interventions to patients with severe traumatic brain injury. By brain tissue oxygen levels into the overall management of these team will be to the care