Monitoring neurologic patients in intensive care

Temporal Profiles of Cerebral Perfusion Pressure After Subarachnoid Hemorrhage

INTRODUCTION

Insufficient cerebral perfusion pressure (CPP) after aneurysmal subarachnoid hemorrhage can impair cerebral blood flow. We examined the temporal profiles of CPP change and tested whether these profiles were associated with delayed cerebral ischemia (DCI).

METHOD

CPP values were retrospectively reviewed for 238 subjects. Intracranial pressure and mean arterial pressure values were obtained every 2 hours for 14 days. Induced hypertension was utilized to prevent vasospasm. The linear and quadratic CPP changes over time were tested using growth curve analysis. Multivariable logistic regression was utilized to examine the association between DCI and percentages of CPP values of >110, >100, <70, and <60 mm Hg. DCI was defined as neurological deterioration because of impaired cerebral blood flow.

RESULTS

Between-subject differences accounted for 39% of variation in CPP values. There was a significant linear increase in CPP values over time (β = 0.06, SE = 0.006, p < .001). The covariance (-0.52, SE = 0.09, p < .001) between initial CPP and linear parameter was negative, indicating that subjects with high CPP on admission had a slower rate of increase whereas those with low CPP had a faster rate of increase. For every 10% increase in the proportion of CPP of >100 or >110 mm Hg, the odds of DCI increased by 1.21 and 1.43, respectively (p < .05).

CONCLUSIONS

The longer the time patients spent with high CPP, the greater the odds for DCI. When used prophylactically, induced hypertension contributes to higher CPP values. On the basis of the CPP trends and correlations observed, induced hypertension may not confer expected benefits in patients with aneurysmal subarachnoid hemorrhage.

Bench-to-Bedside and Bedside Back to the Bench; Seeking a Better Understanding of the Acute Pathophysiological Process in Severe Traumatic Brain Injury

Despite substantial investments, traumatic brain injury (TBI) remains one of the major disorders that lack specific pharmacotherapy. To a substantial degree, this situation is due to lack of understanding of the pathophysiological process of the disease. Experimental TBI research offers controlled, rapid, and cost-effective means to identify the pathophysiology but translating experimental findings into clinical practice can be further improved by using the same or similar outcome measures and clinically relevant time points. The pathophysiology during the acute phase of severe TBI is especially poorly understood. In this Mini review, I discuss some of the incongruences between current clinical practices and needs versus information provided by experimental TBI research as well as the benefits of designing animal experiments with translation into clinical practice in mind.

Normothermic cardiopulmonary bypass increases cerebral tissue oxygenation during combined valve surgery: a single-centre, randomized trial

OBJECTIVES

In cardiac surgery, the choice of temperature regimen during cardiopulmonary bypass (CPB) remains a subject of debate. Hypothermia reduces tissue metabolic demands, but may impair the autoregulation of cerebral blood flow and contribute to neurological morbidity. The aim of this study was to evaluate the effect of two different temperature regimens during CPB on the systemic oxygen transport and the cerebral oxygenation during surgical correction of acquired heart diseases.

METHODS

In a prospective study, we randomized 40 adult patients with combined valvular disorders requiring surgical correction of two or more valves into two groups: (i) a normothermic (NMTH) group (n = 20), in which the body core temperature was maintained at 36.6°C during CPB and (ii) a hypothermic (HPTH) group (n = 20), in which the body was cooled to a core temperature of 32°C maintained throughout the period of CPB. The systemic oxygen transport and the cerebral oxygen saturation (SctO2) were assessed by means of a PiCCO2 haemodynamic monitor and a cerebral oximeter, respectively. All the patients received standard perioperative monitoring. We assessed haemodynamic and oxygen transport parameters, the duration of mechanical ventilation and the length of the ICU and the hospital stays.

RESULTS

During CPB, central venous oxygen saturation was significantly higher in the HPTH group but SctO2 was increased in the NMTH group (P < 0.05). Cardiac index, systemic oxygen delivery and consumption increased postoperatively in both groups. However, oxygen delivery and consumption were significantly higher in the NMTH group (P < 0.05). The duration of respiratory support and the length of ICU and hospital stays did not differ between the groups.

CONCLUSIONS

During combined valve surgery, normothermic CPB provides lower central venous oxygen saturation, but increases cerebral tissue oxygenation when compared with the hypothermic regimen.

Neuromonitoring for Traumatic Brain Injury in Neurosurgical Intensive Care

The primary aim of neuromonitoring in patients with traumatic brain injury is early detection of secondary brain insults so that timely interventions can be instituted to prevent or treat secondary brain injury. Intracranial pressure monitoring has been a stalwart in neuromonitoring and is still very much the main parameter to guide therapy in brain injured patients in many centres. Cerebral oxygenation is also established as an important parameter for monitoring: global cerebral oxygenation is reliably measured using jugular venous oxygen saturation while brain tissue oxygen tension measurement allows focal brain oxygenation to be monitored. Near-infrared spectroscopy allows a non-invasive option for monitoring of regional cerebral oxygenation. Cerebral microdialysis makes focal measurements of markers of cellular metabolism and cellular injury and death possible, and it is in transition from being a research tool to being an important clinical tool in neuromonitoring. Multimodal monitoring allows different parameters of brain physiology and function to be monitored and can improve identification and prediction of secondary cerebral insults. Multimodal monitoring can potentially improve outcomes in patients with traumatic brain injury by promoting customised treatment strategies for individual patients in place of the commonplace practice of strict adherence to achieving the same standard physiological targets for every patient.

Effects of propofol sedation during the early postoperative period in hemorrhagic stroke patients

BACKGROUND

The early postoperative period is a critical time for patients after receiving a decompressive craniotomy. Prompt detection and early management of postoperative recurrent/residual hemorrhagic complications may dramatically improve clinical outcomes.

METHODS

The present cohort retrospective study involved 135 patients who received decompressive craniotomy and intensive care unit (ICU) supervision as life-saving measures. The purpose of the study was to evaluate the effects of propofol sedation on the clinical outcome during the ICU stay. The patients' demographic data, hemodynamic variables, the dose of propofol used during the first 48 hours after surgery, residual/recurrent blood clot volume after surgery, and neurologic and clinical outcomes were reviewed. The propofol dosages used for sedation were further divided into three categories: < 0.66, 0.66-3.33 and > 3.33 mg/kg/hr, based on the doses infused during the first 12 hours after surgery.

RESULTS

Our results indicated that the patients of the propofol-sedated group had a significantly smaller amount of residual/recurrent blood clot (p < 0.05) than did those of the non-sedated group. The 30-day mortality rate was significantly lower in the propofol-sedated group (p < 0.05) than in the non-sedated group. Among the propofol-sedated patients, those who received a dose of 0.66-3.33 mg/kg/hr in the first 12 hours after surgery achieved significantly improved clinical and neurologic outcomes than those who received either more than 3.33 mg/kg/hr or less than 0.66 mg/kg/hr of propofol.

CONCLUSION

Our results support the use of propofol sedation during the early postoperative period after craniotomy in hemorrhagic stroke patients, because it improved both neurologic and clinical outcomes. However, early postoperative use of propofol sedation at larger dosages warrants special attention.

Potential use of quantitative bedside CBF monitoring (Xe-CT) for decision making in neurosurgical intensive care

During a 3-year period, mobile xenon-computerized tomography (Xe-CT) for bedside quantitative assessment of cerebral blood flow was used as an integrated tool for decision making during the care of complicated patients in our neurosurgical intensive care units (NSICU), in an attempt to make a preliminary evaluation regarding the usefulness of this method in routine work in the neurosurgical intensive care. With approximately 200 studies involving 75 patients, we identified six different categories where the use of bedside Xe-CT significantly influenced (or, with more experience, could have influenced) the decision making, or facilitated the handling of patients. These categories included identification of problems not apparent from other types of monitoring, avoidance of adverse effects from treatment, titration of standard treatments, evaluation of the vascular resistance reserve, assessment of adequate perfusion pressure and better utilization of resources from access to the bedside cerebral blood flow (CBF) technology. We conclude that quantitative bedside measurements of CBF could be an important addition to the diagnostic and monitoring arsenal of NSICU-tools.

Multicenter evaluation of propofol for head-injured patients in Taiwan

BACKGROUND

The present study was a multicenter, retrospective study which aimed to evaluate the efficacy of propofol, a new choice of pharmacotherapy in head-injured patients.

METHODS

Head-injured patients admitted to 3 hospitals during the period from January 2003 to December 2004 were included in this clinical trial. Data on patients' demographics, laboratory data, GCS score, ICP, CPP, concurrent medications, and therapeutic outcomes were collected.

RESULTS

Among the 104 patients included, only 44 were given propofol. The average age was 40.8 +/- 22 years for all patients, with 41.91 +/- 20.41 and 43.48 +/- 23.19 years for the propofol group and nonpropofol group, respectively (P=.097). There was no significant difference in baseline GCS score between the 2 groups (5.86 +/- 1.84 vs 5.66 +/- 1.59, P=.729). Mean ICP for the first 3 days in the ICU was 17.23 +/- 9.0 mm Hg in the propofol group and 33.19 +/- 32.56 in the nonpropofol group, respectively (P=.017). Mean CPP for the first 5 days in the ICU was 71.10 +/- 15.32 mm Hg in the propofol group and 43.20 +/- 29.92 mm Hg in the nonpropofol group (P<.001). A higher survival rate was found in the propofol group (81.8% vs 46.7%, P<.001).

CONCLUSIONS

The present study demonstrated that propofol improved the outcome in recovery phase of head-injured patients.

Multimodal Brain Monitoring in the Neurological Intensive Care Unit: Where Does Continuous EEG Fit In?

Continuous EEG (cEEG) is a vital component of patient monitoring in the neurologic intensive care unit, allowing the intensivist to diagnose nonconvulsive seizure activity. Though still in its infancy, Fourier-transformed cEEG data are also increasingly being used in ICUs to monitor global cerebral activity and cortical function. In conjunction with other components of multimodality neurologic monitoring, including intracranial pressure, cerebral blood flow, brain tissue oxygen tension monitoring, transcranial Doppler, and microdialysis monitoring, cEEG provides unique data regarding the electrical activity of the brain. The main challenge for clinicians and researchers will be to understand how these different aspects of multimodality monitoring relate to each other, and how physiologic variables such as blood pressure, osmolality, and temperature can be manipulated to optimize cerebral function and tissue survival in the setting of acute injury.

Induced hypothermia in critical care medicine: a review

BACKGROUND

Clinical trials of induced hypothermia have suggested that this treatment may be beneficial in selected patients with neurologic injury.

OBJECTIVES

To review the topic of induced hypothermia as a treatment of patients with neurologic and other disorders.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

Improved outcome was demonstrated in two prospective, randomized, controlled trials in which induced hypothermia (33 degrees C for 12-24 hrs) was used in patients with anoxic brain injury following resuscitation from prehospital cardiac arrest. In addition, prospective, randomized, controlled trials have been conducted in patients with severe head injury, with variable results. There also have been preliminary clinical studies of induced hypothermia in patients with severe stroke, newborn hypoxic-ischemic encephalopathy, neurologic infection, and hepatic encephalopathy, with promising results. Finally, animal models have suggested that hypothermia that is induced rapidly following traumatic cardiac arrest provides significant neurologic protection and improved survival.

CONCLUSIONS

Induced hypothermia has a role in selected patients in the intensive care unit. Critical care physicians should be familiar with the physiologic effects, current indications, techniques, and complications of induced hyperthermia.

Cerebral edema leading to decompressive craniectomy: an assessment of the preceding clinical and neuromonitoring trends

The aim of this study was to examine the pre-operative clinical and neuromonitoring courses in patients with a decompressive craniectomy to assess and to compare clinical and neuromonitoring signs indicating extensive cerebral edema. We conducted a retrospective analysis of the clinical signs and courses of simultaneous monitoring of intracranial pressure (ICP) and cerebral oxygenation (PtiO2) in 26 consecutive patients who were sedated and treated with a decompressive craniectomy due to extensive cerebral edema after aneurysmal subarachnoid hemorrhage (SAH) (n = 20) or severe head injury (SHI) (n = 6). Pathological monitoring trends always preceded clinical deterioration. In 18 of 26 patients extensive cerebral edema was indicated solely by increasing ICP > 20 mmHg or decreasing PtiO2 < 10 mmHg or both. Anisocoria occurred in only 8 of 26 patients. As opposed to SHI patients, 9 of 20 SAH patients showed decreasing PtiO2 as first warning sign clearly before neurological deterioration or ICP increase. This series shows the utility of combined ICP and PtiO2 monitoring in patients who develop extensive cerebral edema. Pathological monitoring trends indicate deterioration prior to clinical signs which offers a wider therapeutical window. PtiO2 monitoring appears to be particularly valuable after aneurysmal SAH as adjunct to ICP monitoring and CT imaging.

Continuous nervous system monitoring, EEG, the bispectral index, and neuromuscular transmission

In critically ill patients, the central nervous system remains vulnerable to multiple insults including ischemia, hemorrhagic events, and encephalopathy. The peripheral nervous system is vulnerable in the setting of neuro-muscular blockade (NMB), related drug-drug interactions, and drug-clinical state interactions. Optimal assessment of the nervous system is done by means of the clinical neurological examination. In this manner, orientation, arousal, and responsiveness to stimulation provide feedback on focal and global stability of the central nervous system. Where clinical evaluation is compromised, such as with deep sedation and NMB, risk of undetected seizure activity, and/or progression of neurological injury increases dramatically. A patient receiving NMB risks breakthrough awareness and pain. Long-term complications of NMB including prolonged weakness or paralysis as well as post-traumatic stress dramatically increase morbidity and length of stay. Technologies such as electroencephalogram (EEG) and bispectral index (BIS trade mark ) monitoring are effective for assessing cerebral function as well as level of sedation or arousal, respectively, in patients with a compromised neurological assessment. Neuromuscular transmission (NMT) monitoring by means of peripheral nerve stimulation and assessment of the evoked response may be utilized, within the context of clinical assessment, to determine level of chemical paralysis and minimize dosing of NMB agents. This article explores utilization and differentiates technologies such as EEG, BIS, and NMT monitoring. Monitoring parameters are illustrated using a case study approach.