Lena Nyholm

High-temperature open tubular liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry

Abstract A micro heated nebuliser interface was constructed and used for coupling of open tubular liquid chromatography at 150°C to atmospheric pressure chemical ionisation mass spectrometry. For the chromatography, 50 μm I.D. columns were utilised at a flow-rate of 0.1–1.6 μl/min. The efficiency loss due to the MS detector, including the interface, was found to correspond to only 5% for a 10-m column. The MS detector was shown to be mass flow sensitive at these low flow-rates, with a detection limit of 3 pg/s for 7,8-benzoquinoline. This corresponds to a concentration of 1 μM using a flow-rate of 1 μl/min. In addition, the use of a temperature gradient in combination with MS detection is demonstrated. Important parameters for the performance of the interface such as temperature, orifice potential and organic modifier, as well as the choice of buffer salt in the mobile phase are also discussed. The MS detector was used to study the stability of the thermally labile compound bromocriptine in high-temperature chromatography. The experiments suggest that even thermally labile analytes can be separated with high-temperature open tubular liquid chromatography.

Column preparation for reversed-phase high-temperature open tubular column liquid chromatography

A method for the preparation of stable reversed-phase columns for high temperature open tubular column liquid chromatography (HT-OT-LC) has been developed and the effect of covalent bonding of the stationary phase to a covalently bonded deactivation layer, as well as, crosslinking of the polysiloxane stationary phase has been investigated. It was found that the column lifetime depended primarily on the extent of crosslinking of the stationary phase film with azo-tert.-butane and a dynamic crosslinking procedure was developed for this purpose. By extensive crosslinking of the polysiloxane stationary phase, column lifetimes of more than several hundreds of hours could be obtained at 150°C. Inadequate crosslinking, on the other hand, resulted in shorter column lifetimes most likely as a result of hydrolysis of the stationary phase polymer leading to its collapse in the centre of the column. No significant difference in column lifetime was seen between columns prepared with 50% n-octylpolymethylsiloxane or 49% n-octyl-, 1% n-octenylpolymethylsiloxane stationary phases, with cyano or octyl groups in the deactivation layer, or between columns with different stationary phase film thickness (in the range between 0.25 and 0.60 μm).

The Use of Nurse Checklists in a Bedside Computer-Based Information System to Focus on Avoiding Secondary Insults in Neurointensive Care

The feasibility and accuracy of using checklists after every working shift in a bedside computer-based information system for documentation of secondary insults in the neurointensive care unit were evaluated. The ultimate goal was to get maximal attention to avoid secondary insults. Feasibility was investigated by assessing if the checklists were filled in as prescribed. Accuracy was evaluated by comparing the checklists with recorded minute-by-minute monitoring data for intracranial pressure-ICP, cerebral perfusion pressure CPP, systolic blood pressure SBP, and temperature. The total number of checklist assessments was 2,184. In 85% of the shifts, the checklists were filled in. There was significantly longer duration of monitoring time at insult level when Yes was filled in regarding ICP (mean 134 versus 30 min), CPP (mean 125 versus 26 min) and temperature (mean 315 versus 120 min). When a secondary insult was defined as >5% of monitoring time spent at insult level, the sensitivity/specificity for the checklist assessments was 31%/100% for ICP, 38%/99% for CPP, and 66%/88% for temperature. Checklists were feasible and appeared relatively accurate. Checklists may elevate the alertness for avoiding secondary insults and help in the evaluation of the patients. This concept may be the next step towards tomorrow critical care.

Secondary insults related to nursing interventions in neurointensive care: a descriptive pilot study.

ABSTRACT The patients at a neurointensive care unit are frequently cared for in many ways, day and night. The aim of this study was to investigate the amount of secondary insults related to oral care, repositioning, endotracheal suctioning, hygienic measures, and simultaneous interventions at a neurointensive care unit with standardized care and maximum attention on avoiding secondary insults. The definition of a secondary insult was intracranial pressure > 20 mm Hg, cerebral perfusion pressure < 60 mm Hg and systolic blood pressure < 100 mm Hg for 5 minutes or more in a 10-minute period starting from when the nursing intervention began. The insult minutes did not have to be consecutive. The study included 18 patients, seven women and 11 men, aged 36–76 years with different neurosurgical diagnoses. The total number of nursing interventions analyzed was 1,717. The most common kind of secondary insults after a nursing measure was high intracranial pressure (n = 93) followed by low cerebral perfusion pressure (n = 43) and low systolic blood pressure (n = 14). Repositioning (n = 39) and simultaneous interventions (n = 32) were the nursing interventions causing most secondary insults. There were substantial variations between the patients; only one patient had no secondary insult. There were, overall, a limited number of secondary insults related to nursing interventions when a standardized management protocol system was applied to reduce the occurrence of secondary insults. Patients with an increased risk of secondary insults should be recognized, and their care and treatment should be carefully planned and performed to avoid secondary insults.

The influence of hyperthermia on intracranial pressure, cerebral oximetry and cerebral metabolism in traumatic brain injury

Abstract Background: Hyperthermia is a common secondary insult in traumatic brain injury (TBI). The aim was to evaluate the relationship between hyperthermia and intracranial pressure (ICP), and if intracranial compliance and cerebral blood flow (CBF) pressure autoregulation affected that relationship. The relationships between hyperthermia and cerebral oximetry (BtipO2) and cerebral metabolism were also studied. Methods: A computerized multimodality monitoring system was used for data collection at the neurointensive care unit. Demographic and monitoring data (temperature, ICP, blood pressure, microdialysis, BtipO2) were analyzed from 87 consecutive TBI patients. ICP amplitude was used as measure of compliance, and CBF pressure autoregulation status was calculated using collected blood pressure and ICP values. Mixed models and comparison between groups were used. Results: The influence of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and BtipO2) was small, but individual differences were seen. Linear mixed models showed that hyperthermia raises ICP slightly more when temperature increases in the groups with low compliance and impaired CBF pressure autoregulation. There was also a tendency (not statistically significant) for increased BtipO2, and for increased pyruvate and lactate, with higher temperature, while the lactate/pyruvate ratio and glucose were stable. Conclusions: The major finding was that the effects of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and BtipO2) were not extensive in general, but there were exceptional cases. Hyperthermia treatment has many side effects, so it is desirable to identify cases in which hyperthermia is dangerous. Information from multimodality monitoring may be used to guide treatment in individual patients.

Predictive Factors That May Contribute to Secondary Insults With Nursing Interventions in Adults With Traumatic Brain Injury.

ABSTRACT 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.