Predictive factors that may contribute to secondary insults with nursing interventions in adults with traumatic brain injury.
Background: Nursing interventions pose risks and benefits to patients with traumatic brain injury at a neurointensive care unit. Objectives: The aim of this study was to investigate the risk of inducing high intracranial pressure (ICP) related to interventions and whether intracranial compliance, baseline ICP, or autoregulation could be used as predictors. Methods: The study had a quantitative, prospective, observational design. Twenty-eight patients with TBI were included, and 67 interventions were observed. The definition of a secondary ICP insult was ICP of 20 mm Hg or greater for 5 minutes or more within a continuous 10-minute period. Results: Secondary ICP insults related to nursing interventions occurred in 6 patients (21%) and 8 occasions (12%). Patients with baseline ICP of 15 mm Hg or greater had 4.7 times higher risk of developing an insult. The predictor with the best combination of sensitivity and specificity was baseline ICP. Conclusions: Baseline ICP of 15 mm Hg or greater was the most important factor to determine the risk of secondary ICP insult related to nursing intervention.
Keywords: neurointensive care, nursing implications, nursing interventions, secondary insults
Traumatic brain injury (TBI) is a serious health problem with both high morbidity and mortality. (1) Modern neurointensive care (NIC) has improved patient outcomes substantially. (2) The main aim of NIC is to avoid secondary brain insults, for example, high intracranial pressure (ICP), hypotension, low cerebral perfusion pressure (CPP), hypoxemia, hypercapnia, hyperglycemia, seizures, and fever. (3) To prevent secondary insults, many prophylactic measures are used such as mechanical ventilation, drug utilization, and nursing interventions, for example, oral care, endotracheal suction, and changing of body position. Moreover, repeated imaging and multimodality monitoring are used, including ICP and CPP monitoring, to be able to detect and treat secondary brain insults immediately. Patient outcomes can be improved when these methods are used as part of a systematic clinical routine aimed at preventing the development of secondary brain injury. (2)
There is also a risk that nursing interventions can cause intracranial hypertension. One possible risk factor for inducing increased ICP is low intracranial compliance, that is, poor ability to compensate for added intracranial volume. Intracranial compliance is expressed as the change in volume per unit change in ICP (C = [DELTA]V/[DELTA]P) (4) Compliance can be evaluated as the mean value of the amplitude of the ICP waveform. (5) Another possible risk factor for inducing intracranial hypertension is disturbed cerebral pressure autoregulation. Increased blood pressure in situations of stress causes cerebral vasodilatation when the pressure autoregulation is disturbed, which may cause intracranial hypertension, particularly if compliance is low. If the pressure autoregulation is intact, an increased blood pressure causes cerebral vasoconstriction, and the ICP does not increase. The pressure reactivity index (PRx) is a method, based on the correlation of ICP and mean arterial pressure (MAP), to estimate the degree of pressure autoregulation. High values of the PRx are associated with disturbed pressure autoregulation ([greater than or equal to] 0.3), and low values are associated with intact pressure autoregulation (<0.3). (6)
In our earlier pilot study, we showed that nursing interventions (oral care, repositioning, endotracheal suctioning, hygienic measures, and simultaneous measures) started a secondary insult with ICP of greater than 20 mm Hg in 5%, CPP of less than 60 mm Hg in 3%, and systolic blood pressure of less than 100 mm Hg in 1 % of the cases. (7) There were substantial variations among the patients, and therefore, it would be helpful to find a way to estimate the patient's risk of developing a secondary insult if a nursing intervention is performed. In this study, nursing interventions that were possible to plan when to perform were observed to ensure that all interventions were performed under the same conditions. The included nursing interventions were repositioning in 2 ways and a hygienic procedure. Moreover, it was interesting to study nursing interventions in which the nurse could choose to act or not.
Nursing interventions can prevent secondary insults and offer comfort to the patient, but sometimes, they may also cause a secondary insult. Therefore, it would be of great value if patients at risk could be identified in advance. The aims of this study of patients with TBI were to investigate the occurrence of secondary ICP insult in association with nursing interventions and to determine whether ICP amplitudes ([greater than or equal to] 6 mm Hg), baseline ICP level ([greater than or equal to]15 mm Hg), or the PRx ([greater than or equal to] 0.3) can be used to identify patients at risk.
The study had a prospective, observational design.
Inclusion criteria were as follows: age of 16 to 80 years, mechanical ventilation, and ICP monitoring during the study period. Intracranial pressure was monitored using either a parenchymal probe or a closed ventricular catheter drain system.
Patients with cerebrospinal fluid leakage and/or external decompressive craniectomy were excluded from the study because their intracranial compliance was influenced and the PRx calculation was unreliable. Patients with barbiturate coma treatment were excluded because of the treatment regimen and high likelihood of sustained increased ICP. Furthermore, patients with increased ICP of greater than 20 mm Hg at the time of inclusion were excluded.
The nursing interventions studied were repositioning and hygienic interventions. The included patients with TBI were observed when they were repositioned by at least 2 persons. When repositioning, the neck was always extended to avoid venous stasis. To facilitate venous outflow and to prevent ventilator-associated pneumonia, the patients' heads were elevated 30[degrees].
The observed hygienic intervention included a series of procedures. The patients were washed in bed by 1 or 2 persons with washcloths. In connection with the washing, bed sheets and clothes were changed. Oral care was also performed. Sometimes, endotracheal suction was needed and performed. Strict hygiene, a negative pressure of 20 cm [H.sub.2]0, and as short a procedure as possible (10-15 seconds) are prescribed in our standardized management protocol system.
Figure 1 shows the study design. Before the nursing intervention began, we ensured that the patients were undisturbed for 30 minutes (preintervention periods A and B, both 15 minutes). The aim of preintervention period A was to avoid effects from previous interventions. The mean baseline values of ICP, the PRx, and ICP amplitude were calculated for preintervention period B. No patient had any ICP values greater than 20 mm Hg in preintervention period B. After the nursing intervention was finished, the patient was again left undisturbed for another 30 minutes. The postintervention period was divided into postintervention periods A and B (Fig 1). Intracranial pressure, ICP amplitude, and the PRx were recorded once every minute throughout the study.
The observed interventions were made, on average, 3.2 [+ or -] 1.9 (range, 1-8) days after injury.
The study was performed at an NIC unit with 12 beds in Uppsala, Sweden, with a catchment area of approximately 2 million people. All types of neurosurgical patients who need NIC are admitted, from small children to adults. The main diagnoses are TBI, subarachnoid hemorrhage, and intracerebral hemorrhage.
At the NIC unit, a licensed intensive care nurse with at least 4 years of university education is responsible for all nursing interventions, assisted by licensed practical nurses. One intensive care nurse and 1 licensed practical nurse take care of 2 patients.
Routine Treatment Protocols
The patients with TBI were treated according to a standardized escalated management protocol based on available guidelines. (3) The treatment goals (eg, ICP < 20 mm Hg, CPP > 60 mm Hg, and systolic blood pressure > 100 mm Hg) are presented in Supplemental Table 1 (available as Supplemental Digital Content 1 at http://links.lww.com/JNN/A80). (2) All patients who did not respond to commands, Glasgow Coma Scale (GCS)-Motor of less than 5, were intubated and artificially ventilated, and ICP was monitored continuously. Propofol was given for sedation (maximum, 4 mg/kg/h), and morphine chloride (intermittent intravenous injections of 2 mg or infusion of 1 mg/mL, 1-5 mL/h) was given for analgesia. Sedation and pain relief were administered until the patient was judged relaxed and comfortable by the attending author (L.N.); that is, the patient was calm with stable vital parameters and no signs of grimace, tearing, or frown forehead. The standardized management protocols at the NIC unit also emphasize the importance of giving extra sedation and pain relief to the patients before and during a nursing intervention to avoid stress. The sedation level was not assessed because the patients were unconscious and had acute brain injuries. Neurological wake-up tests (8,9) were performed regularly.
Twenty-eight patients with TBI treated from March 1, 2012, to August 22, 2014, were conveniently included in this prospective study. Inclusion took place when L.N. was present at the unit.
Three different nursing interventions were planned to be observed in each patient, one of each type according to the protocol. Finally, 67 nursing interventions were observed. There were 17 observations considered as missing data because some patients had to be excluded after 1 or 2 observations because the opening of ventricular catheter drain systems had been prescribed, barbiturate coma treatment had been introduced, or baseline ICP was greater than 20 mm Hg.
The following interventions were performed and included in the final study: (1) repositioning from supine to lateral position, n = 24; (2) repositioning from lateral to supine position, n = 25; and (3) hygienic intervention, n = 18.
Since 2008, all patients with TBI admitted to our NIC unit have been included in a local registry for patients with TBI--the Uppsala Traumatic Brain Injury register. (10) Patient characteristics were extracted from that database.
Baseline ICP, ICP Amplitudes, and the PRx
Intracranial pressure was monitored with a ventricular drainage catheter system (Smiths Medical, Grasbrunn, Germany) if possible. In cases with compressed ventricular system, a parenchymal probe was used instead (Codman 1CP express; Johnson & Johnson, Raynham, Mass). In this study, 6 patients (21%) had a closed ventricular drainage catheter system, and 22 patients (79%) had a parenchymal probe available as Supplemental Digital Content 2 at http://links.lww.com/JNN/A81).
Baseline ICP was characterized as high ([greater than or equal to] 15 mm Hg) or low (<15 mm Hg).
Compliance was estimated by using the amplitudes in the ICP curve as previously described. (5) The amplitude was calculated as the difference between the maximum and minimum of the ICP pulse waveform. A patient was considered to have poor intracranial compliance when ICP amplitudes exceeded 6 mm Hg.
Pressure autoregulation was estimated by using the PRx. The PRx is based on the correlation of ICP and MAP, so that, when ICP is highly correlated with MAP, the PRx approaches a maximum value of 1. When MAP and ICP are uncorrelated or negatively correlated, the PRx is close to 0 or negative, with the minimum possible being--1. Hence, high values of the PRx are associated with disturbed pressure autoregulation, and low values are associated with intact autoregulation. In this study, we classified patients as having disturbed pressure autoregulation when PRx was 0.3 or greater and as having intact pressure autoregulation when PRx was less than 0.3. Usually, the PRx is computed from the ICP and MAP waveforms by taking the mean values of a series of 5- to 10-second segments during 3 to 5 minutes. The correlation of ICP and MAP is then computed to produce the index. Waveforms are sometimes preprocessed using a bandpass filter to remove irrelevant low- and high-frequency variations. (5) Here, we used the methodology described by Howells et al. (11)
Definition of a Secondary Insult
A secondary insult may be defined in several ways. In this study, a secondary ICP insult was defined as sustained ICP of 20 mm Hg or greater for 5 minutes or more during a continuous 10-minute period. The entire insult had to occur within the intervention and/or postintervention period A (Fig 1). It was necessary to include the postintervention period A because some interventions did not last for the 5 minutes required to fulfill the criteria for an insult.
All patients at the NIC unit in Uppsala University Hospital, Sweden, are connected to the Odin monitoring system developed by Tim Howells and colleagues in Edinburgh and Uppsala. This system collects minute-by-minute monitoring data and makes it possible to study physiological monitoring parameters in real time or retrospectively. Waveform data are also acquired. Here, ICP and MAP were recorded at 100 Hz. The quality of the collected monitoring data was screened, and artifacts were removed using the Odin software.
The first author (L.N.) attended all occasions when data were collected to ensure that the monitor equipment was correctly calibrated and to record the exact start and stop times of the intervention periods.
The mean values of ICP, ICP amplitude, and the PRx during preintervention period B were analyzed and used as predictors. Those measures were used to classify the patients as being at high or low risk of an ICP insult in 3 ways.
Compliance is measured with amplitudes (high risk, [greater than or equal to] 6 mm Hg; low risk, <6 mm Hg). High-risk baseline ICP is 15 mm Hg or greater, and low risk is less than 15 mm Hg. Pressure autoregulation is calculated as PRx (high risk, [greater than or equal to] 0.3; low risk, <0.3).
To evaluate the accuracy of using these thresholds for predicting the risk of a secondary ICP insult after a nursing intervention, sensitivity, specificity, positive predictive value, and negative predictive value were calculated. For comparing risk groups, [chi square] test was used with P <.05 as the level of significance.
The patients were unconscious when they participated in this study. Informed consent was obtained from their next of kin. The study was approved by the local ethics committee, and the study was performed according to the Declaration of Helsinki.
Twenty-eight patients, 24 men and 4 women, were included. The median age was 49 years (interquartile range [IQR], 41 years; range, 19-79 years). On admission, the median GCS was 7 (IQR, 2; range, 5-15), and GCS-Motor response was 5 (IQR, 0.0; range, 1-6). The main types of injury were as follows: acute subdural hematoma (7, 25%), contusions (6, 21%), diffuse axonal injury (4,14%), traumatic subarachnoid hemorrhage (3, 11%), epidural hematoma (2,7%), and mixed injury (6, 22%) available as Supplemental Digital Content 2 at http://links.lww.com/JNN/A81).
In 35 of the nursing interventions (52%), ICP remained less than 20 mm Hg throughout the observation period. In general, a few monitoring values greater than 20 mm Hg related to nursing interventions were observed (available as Supplemental Digital Content 3 at http://links.lww.com/JNN/A82). A secondary ICP insult with the definition "ICP > 20 mm Hg during >5 minutes" was observed in 6 patients (21%) and 8 occasions (12%). All these ICP insults occurred within 10 minutes.
Repositioning took 1 to 8 minutes (median, 2 minutes; IQR, 2.3 minutes). Four patients (16%) turned from lateral to supine position and had a secondary ICP insult, as did 1 patient (4%) who turned from supine to lateral position.
The hygienic procedures took 12 to 43 minutes (median, 23 minutes; IQR, 17.5 minutes). Three patients (17%) had a secondary ICP insult related to hygienic procedures.
Predicting a Secondary Insult
The results for the high- and low-risk groups for secondary ICP insults are given in Table 1. The high-risk pressure autoregulation group (PRx [greater than or equal to] 0.3) had a risk ratio of 1.7 (ie, 60% more insults than the low-risk group), whereas the high-risk intracranial compliance group (amplitude [greater than or equal to] 6 mm Fig) had a risk ratio of 2.9 (170% more insults than the low-risk group), but these results were not statistically significant. The only statistically significant result was for the high-risk ICP group (ICP [greater than or equal to] 15 mm Fig), which had a risk ratio of 4.7 or 360% more insults than the low-risk group.
Generally, for all 3 predictors, specificity was higher than sensitivity, which was low. The high negative predictive values indicate that it is of low probability that a patient in the low-risk group will have a secondary insult related to a nursing intervention. This means that the predictors had relatively good ability to identity true negative cases, that is, patients with low risk. On the contrary, a large proportion of the patients identified as having high risk did not have secondary insults, that is, that the values were not good positive predictors, although the risk ratio was higher than in the group identified to have low risk.
Compliance (baseline amplitudes, [greater than or equal to] 6 or <6 mm Hg) showed the highest sensitivity (63%). Baseline ICP ([greater than or equal to] 15 or <15 mm Hg) had the highest specificity (86%) and showed the best combination of sensitivity (50%) and specificity (86%) (Table 1). The negative predictive value was high in all 3 groups, and ICP of 15 mm Hg or greater had the highest positive predictive value (33%) (Table 1). Baseline amplitude of 6 mm Hg or greater had the best ability to identify true positive cases (high sensitivity), that is, patients with high risk. The baseline mean values of the predictors in 6 patients who had an ICP insult related to a nursing intervention are presented in supplemental Table 4 (available as Supplemental Digital Content 4 at http:// links.lww.com/JNN/A83).
Secondary ICP insults occurred in 6 patients (21%) and in 8 of the studied nursing interventions (12%). We evaluated mean baseline ICP, ICP amplitude, and the PRx as potential predictors of secondary insults. Our main finding was a significant difference in the occurrence of insults between the groups with high and low baseline ICPs. It was easier to identify patients with low risk for secondary ICP insults related to nursing interventions than patients with high risk; that is, the specificity was high, and the sensitivity was low. If the predictor ICP of 15 mm Hg or greater is used in practice, nurses should be aware that some of the high-risk patients may become inadequately undertreated because of the low sensitivity; that is, they would have managed to undergo a nursing intervention without developing an insult. There is strong evidence for early mobilization in critically ill patients, which should also be considered. However, because of the high specificity, it is unlikely that a patient with low risk would experience a secondary insult related to a nursing intervention.
A few previous studies have in different ways analyzed how nursing interventions influence ICP in patients with TBI, but no earlier study had a definition when a secondary insult had occurred. (7,12-16) In a previous pilot study, (7) the proportion of secondary ICP insults was lower (5%) than that in this study. This may be because, in the pilot study, patients with an open ventricular drainage were included. (7) Another observational study on the effects of nursing intervention on ICP concluded that nursing interventions do not cause a consistent response on ICP; the response depends on the situation in which the intervention is delivered. (13) It is obvious that it would be valuable if patients could be identified with/without high risk for ICP insults. In this study, the result indicates that, if the patient's baseline ICP is less than 15 mm Hg, the risk will be low.
In another study, Ledwith et al (12) concluded that there is no single optimal body position that reduces ICP but that lateral position should be used with caution. In clinical practice, supine position is often used to reduce a high ICP. In this study, secondary ICP insults were more common when turning the patient from lateral to supine position (16%) than vice versa (4%). Prone position is used to treat acute lung insufficiency and may be used even in NIC patients without influencing ICP and CPP. (16) When performing hygienic procedures, we found that 17% of the patients had a secondary insult with ICP greater than 20 mm Hg for 5 minutes or more. The hygienic procedures were the longest observed nursing interventions in this study. One way to avoid secondary ICP insult when performing a hygienic procedure could be to select the most necessary elements of the procedure to make it shorter. Prendergast et al (14) has found that oral care does not influence ICP. Further studies are required to learn more about the risk of increasing ICP in association with different nursing interventions and how to identify patients at risk of developing high ICP.
In this study, the proportion of nursing interventions causing a secondary ICP insult with ICP greater than 20 mm Hg for 5 minutes or more was 12%. All these secondary ICP insults occurred in 6 of 28 patients. This indicates that relatively few patients have an increased risk of secondary ICP insults in association with nursing interventions. Theoretically, patients with ICP close to 20 mm Hg (insult level) and patients with low intracranial compliance (high amplitudes) should have an increased risk of developing secondary ICP insults when a nursing intervention is performed. Furthermore, patients with disturbed pressure autoregulation should have an increased risk of developing high ICP if a nursing intervention is stressful and increases the blood pressure. Most of these risk factors were present before the nursing interventions in 6 patients who had ICP insults, although exceptions occurred (available as Supplemental Digital Content 4 at http://links.lww.com/JNN/A83). It means that these predictors could be used to identify patients who are at an increased risk to be affected by secondary insults related to nursing interventions, although it was noticed that a substantial proportion of the patients identified as high risk was false.
The analysis of all patients showed that insults differed significantly between the groups with high ([greater than or equal to] 15 mm Hg) and low (<15 mm Hg) baseline ICPs. Although the results for parameters relating to intracranial compliance (ICP amplitude) and pressure autoregulation (PRx) were not statistically significant, it should be noted that patients classified with poor compliance (ICP amplitude [greater than or equal to] 6 mm Hg) had ICP insults 2.9 times more often than patients with good compliance, whereas patients with disturbed pressure autoregulation (PRx [greater than or equal to] 0.3) had insults 1.7 times more often than patients with intact pressure autoregulation.
One previous study has shown that compliance and resting ICP were more specific (easier to identify tme negative cases) than sensitive (able to identify tme positive cases) in identifying patients at risk of developing increased ICP in relation to a nursing intervention. (15) The same relation was found in this study, although sensitivity was rather low in all 3 predictors. When sensitivity and specificity were calculated to find a predictor that could identify high-risk patients, amplitudes had the highest sensitivity, whereas specificity was rather high for all 3 factors. The factor with the best combination of sensitivity and specificity seemed to be baseline ICP (greater than or less than 15 mm Hg), which also is the easiest available parameter. Positive and negative predictive values showed the same relation.
There are some methodological limitations of this study that need to be considered. It was advantageous that the data used were well controlled and all interventions were made in a standardized way, but only patients with TBI were included, which could make the results difficult to generalize to other NIC patients. Furthermore, there was a small sample size, the sample was convenient, and the data were collected from only 1 study site, which also may have influenced the results. The fact that the author (L.N.) attended during all occasions when data were collected may have influenced the results. For example, the nursing interventions may have become better planned when an observer was present, but this also ensured that all patients were cared for in the same way.
Intracranial pressure can rise for many different reasons in addition to nursing interventions. However, in this study, all patients were stable before the nursing interventions and adequately sedated.
The definition used for an ICP insult may also be discussed. This study used a definition of ICP of 20 mm Hg or greater for 5 minutes or more occurring within a 10-minute window. This definition is similar to an earlier study by Jones et al, (17) which required 5 continuous minutes over threshold to establish a secondary insult. The 5-minute duration was chosen as a minimum duration by which it is reasonable to believe that a secondary ICP insult may harm the brain. In our study, the 5 minutes with ICP of greater than 20 mm Hg did not need to be continuous, but in a defined, short time frame (10 minutes).
Implications for Nursing Practice
It is the nurses' responsibility to monitor how the patient's ICP is reacting on all different occasions and to treat it if necessary. In daily practice, nurses at an NIC unit continuously make decisions about which nursing interventions should be performed. Nurses have to consider both the positive effects for the patient and the risk that the patient develops a secondary insult. Patients with baseline ICP of less than 15 mm Hg are at a low risk of developing secondary ICP insult in relation to a nursing intervention. Therefore, all kinds of nursing interventions can and shall be performed to prevent possible future secondary insults and to offer the patient maximal comfort. Patients with baseline ICP of 15 to 20 mm Hg could be considered at risk of developing secondary ICP insult in relation to a nursing intervention. However, nursing interventions are necessary also in those patients, but the nurse should be vigilant when performing activities; that is, nursing interventions should be performed in a way that minimizes the probability of secondary insults. The intervention should be well planned. For example, efforts should be taken to correct the body position for optimal venous outflow. Extra sedation/pain relief should be considered. Selected low-priority nursing interventions may be postponed until the ICP is less than 15 mm Hg. When baseline ICP is greater than 20 mm Hg, only nursing interventions that could stop the ongoing secondary insult should be performed, for example, airway suction in endotracheal tube. Extra sedation and pain relief should be given. Sometimes, a nursing intervention has to be done no matter what. If that kind of occasion occurs with a patient at risk for developing a secondary insult, the intervention should be done with particular care, for example, with qualified personnel and extra sedation, pain relief, and necessary equipment nearby.
Secondary ICP insults occurred in 6 patients (21%) and in 8 of the studied nursing interventions (12%). Our main finding was a significant difference in the occurrence of insults between the groups with high and low baseline ICPs. Patients with baseline ICP of 15 mm Hg or greater had secondary ICP insults 4.7 times more often than the low-risk group. It was easier to identify patients with low risk for secondary ICP insults related to nursing interventions than patients with high risk; that is, the specificity was high, and the sensitivity was low. Future work with a larger sample size is needed before a practice change should occur.
Questions or comments about this article may be directed to Lena Nyholm, PhD CCRN, at Lena.firstname.lastname@example.org. She is a Registered Nurse, Department of Neuroscience and Neurosurgery, Uppsala University Hospital, Uppsala University, Uppsala, Sweden.
Tim Howells, PhD, is Software Engineer, Department of Neuroscience and Neurosurgery, Uppsala University, Uppsala, Sweden.
Per Enblad, MD PhD, is Professor of Neurosurgery and Head of Neurointensive Care Unit, Department of Neuroscience and Neurosurgery, Uppsala University, Uppsala, Sweden.
The study was financially supported by the Uppsala County Council (ALE) and Swedish Research Council.
The authors declare no conflicts of interest.
Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jnnonline.com).
The authors are especially thankful to the critical care nurses and the licensed practical nurses at the NIC unit for their support with data collection in this study.
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TABLE 1. Predicting Secondary ICP Insults Related to Nursing Interventions Using Compliance, ICP, and Pressure Autoregulation as Predictive Factors ICP [greater than or equal to] 20 mm Hg for 5 minutes or More in Intervention and Postintervention Period A No Insult Risk Risk Group Insult Insult Rate Ratio Amp [greater than or equal to] 6 5 (1) 20 (2) 0.20 2.9 Amp [less than or equal to] 6 3 (3) 38 (4) 0.07 ICP [greater than or equal to] 15 4 (1) 8 (2) 0.33 4.7 ICP [less than or equal to] 15 4 (3) 51 (4) 0.07 PRx [greater than or equal to] 0.3 3 (1) 15 (2) 0.17 1.7 PRx [less than or equal to] 0.3 5 (3) 44 (4) 0.10 Sensitivity (a)/ PPV (c)/ Risk Group P Specificity (b) NPV(d) Amp [greater than or equal to] 6 .13 63%/66% 20%/93% Amp [less than or equal to] 6 ICP [greater than or equal to] 15 .01 50%/86% 33%/93% ICP [less than or equal to] 15 PRx [greater than or equal to] 0.3 .47 38%/75% 17%/90% PRx [less than or equal to] 0.3 Abbreviations: Amp, amplitudes; ICP, intracranial pressure; NPV, negative predictive value; PPV, positive predictive value; PRx, pressure reactivity index. (a) Sensitivity = true positive (1)/(true positive (1) + false negative (3)). (b) Specificity = true negative (4)/(true negative (4) + false positive (2)). (c) Positive predictive value = true positive (1)/(true positive (1) + false positive (2)). (d) Negative predictive value = true negative (4)/ (true negative (4) + false negative (3)).
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|Author:||Nyholm, Lena; Howells, Tim; Enblad, Per|
|Publication:||Journal of Neuroscience Nursing|
|Date:||Feb 1, 2017|
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