Relationship of Vascular Wall Tension and Autoregulation Following Traumatic Brain Injury

Background

The vascular wall tension (WT) of small cerebral vessels can be quantitatively estimated through the concept of critical closing pressure (CrCP), which denotes the lower limit of arterial blood pressure (ABP), below which small cerebral arterial vessels collapse and blood flow ceases. WT can be expressed as the difference between CrCP and intracranial pressure (ICP) and represent active vasomotor tone. In this study, we investigated the association of WT and CrCP with autoregulation and outcome of a large group of patients after traumatic brain injury (TBI).

Methods

We retrospectively analysed recordings of ABP, ICP and transcranial Doppler (TCD) blood flow velocity from 280 TBI patients (median age: 29 years; interquartile range: 20–43). CrCP and WT were calculated using the cerebrovascular impedance methodology. Autoregulation was assessed based on TCD-based indices, Mx and ARI.

Results

Low values of WT were found to be associated with an impaired autoregulatory capacity, signified by its correlation to FV-based indices Mx (R = ?0.138; p = 0.021) and ARI (R = 0.118; p = 0.048). No relationship could be established between CrCP and any of the autoregulatory indices. Neither CrCP nor WT was found to correlate with outcome.

Conclusions

Impaired autoregulation was found to be associated with a lower WT supporting the role of vasoparalysis in the loss of autoregulatory capacity. In contrast, no links between CrCP and autoregulation could be identified.     

Quantitative indices of baroreflex-sympathoneural function: application to patients with chronic autonomic failure

Purpose

Chronic autonomic failure syndromes such as Parkinson disease with orthostatic hypotension (PD + OH), multiple system atrophy (MSA), and pure autonomic failure (PAF) typically feature arterial baroreflex failure. Identifying baroreflex-sympathoneural failure from hemodynamic responses to the maneuver usually has been qualitative. We report quantitative methods for evaluating baroreflex-sympathoneural function, based on beat-to-beat systolic blood pressure (BPs) responses to the Valsalva maneuver.

Method

Using the trapezoid rule, we calculated the area under the curve (baroreflex area, BRA) between baseline systolic blood pressure (BPs) and the BPs for each beat in Phase II (BRA-II) and Phase IV (BRA-IV) in 136 autonomic failure patients and 171 controls. The sum of the areas was defined as total BRA (BRA-T). We compared individual values by the BRA approach with those by other measures.

Results

Mean values for log BRA-II, BRA-IV, and BRA-T were higher in PD + OH, PAF, and MSA than in controls (p < 0.001 each). The log of BRA-T correlated negatively with the fractional orthostatic change in total peripheral resistance (r = ?0.41, p < 0.001), fractional orthostatic change in plasma norepinephrine (r = ?0.27, p < 0.001), orthostatic change in BPs (r = ?0.62, p < 0.001), fall in BPs in Phase II of the Valsalva (r = 0.58, p < 0.001), and log of baroreflex-cardiovagal slope (r = ?0.40, p < 0.001). Areas under receiver operating characteristic curves were 0.85 for BRA-T and 0.89 for BRA-IV (p < 0.001).

Conclusion

The BRA approach provides quantitative measures of baroreflex-sympathoneural function. Chronic autonomic failure syndromes entail deficiencies of both the cardiovagal and sympathoneural limbs of the arterial baroreflex.     

Continuous Optical Monitoring of Cerebral Hemodynamics During Head-of-Bed Manipulation in Brain-Injured Adults

Introduction

Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering.

Methods

Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO₂), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 min at each position. Patient and control response differences were assessed.

Results

rCBF, ΔHbO₂, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P < 0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3 ± 28.2 %, P = 0.938). rCBF increased in controls (18.6 ± 9.4 %, P < 0.001). ΔHbO₂, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R = 0.40, P < 0.001), but not intracranial pressure.

Conclusion

DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.     

Monitoring cerebral autoregulation after head injury. Which component of transcranial Doppler flow velocity is optimal?

Background

Cerebral autoregulation assessed using transcranial Doppler (TCD) mean flow velocity (FV) in response to various physiological challenges is predictive of outcome after traumatic brain injury (TBI). Systolic and diastolic FV have been explored in other diseases. This study aims to evaluate the systolic, mean and diastolic FV for monitoring autoregulation and predicting outcome after TBI.

Methods

300 head-injured patients with blood pressure (ABP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), and FV recordings were studied. Autoregulation was calculated as a correlation of slow changes in diastolic, mean and systolic components of FV with CPP (Dx, Mx, Sx, respectively) and ABP (Dxa, Mxa, Sxa, respectively) from 30 consecutive 10?s averaged values. The relationship with age, severity of injury, and dichotomized 6?months outcome was examined.

Results

Association with outcome was significant for Mx and Sx. For favorable/unfavorable and death/survival outcomes Sx showed the strongest association (F?=?20.11; P?=?0.00001 and F?=?13.10; P?=?0.0003, respectively). Similarly, indices derived from ABP demonstrated the highest discriminatory value when systolic FV was used (F?=?12.49; P?=?0.0005 and F?=?5.32; P?=?0.02, respectively). Indices derived from diastolic FV demonstrated significant differences (when calculated using CPP) only when comparing between fatal and non-fatal outcome.

Conclusions

Systolic flow indices (Sx and Sxa) demonstrated a stronger association with outcome than the mean flow indices (Mx and Mxa), irrespective of whether CPP or ABP was used for calculation.     

Should the Neurointensive Care Management of Traumatic Brain Injury Patients be Individualized According to Autoregulation Status and Injury Subtype?

Introduction

The status of autoregulation is an important prognostic factor in traumatic brain injury (TBI), and is important to consider in the management of TBI patients. Pressure reactivity index (PRx) is a measure of autoregulation that has been thoroughly studied, but little is known about its variation in different subtypes of TBI. In this study, we examined the impact of PRx and cerebral perfusion pressure (CPP) on outcome in different TBI subtypes.

Methods

107 patients were retrospectively studied. Data on PRx, CPP, and outcome were collected from our database. The first CT scan was classified according to the Marshall classification system. Patients were assigned to “diffuse” (Marshall class: diffuse-1, diffuse-2, and diffuse-3) or “focal” (Marshall class: diffuse-4, evacuated mass lesion, and non-evacuated mass lesion) groups. 2 × 2 tables were constructed calculating the proportions of favorable/unfavorable outcome at different combinations of PRx and CPP.

Results

Low PRx was significantly associated with favorable outcome in the combined group (p = 0.002) and the diffuse group (p = 0.04), but not in the focal group (p = 0.06). In the focal group higher CPP values were associated with worse outcome (p = 0.02). In diffuse injury patients with disturbed autoregulation (PRx >0.1), CPP >70 mmHg was associated with better outcome (p = 0.03).

Conclusion

TBI patients with diffuse injury may differ from those with mass lesions. In the latter higher levels of CPP may be harmful, possibly due to BBB disruption. In TBI patients with diffuse injury and disturbed autoregulation higher levels of CPP may be beneficial.     

Effect of Early Physiotherapy on Intracranial Pressure and Cerebral Perfusion Pressure

Background

Physiotherapy plays an important role in the therapy of patients with acute cerebral diseases. Studies concerning the effects of physiotherapy on intracerebral pressure (ICP) and cerebral perfusion pressure (CPP) are, however, rare.

Methods

An observational study was performed on critically ill patients who were receiving ICP measurements and who were treated with passive range of motion (PROM) on our neuro-intensive care unit. ICP, CPP, mean arterial pressure (MAP) and heart rate were recorded continuously every minute, beginning 15 min before, during (26 min) and 15 min after treatment with PROM. Patients with mean ICP <15 mmHg (Group 1) and patients with mean ICP ≥15 mmHg (Group 2) before physiotherapy were analyzed separately.

Results

Overall there were 84 patients (f:m = 1:1) with 298 treatments units, 224 in Group 1 and 74 in Group 2, respectively. Mean ICP before treatment was 11.5 ± 5.1 mmHg, with a significant decrease of 1 mmHg during therapy (p = 2.0e–10). This was also true for Group 1 (baseline ICP 9.4 ± 3.7 mmHg, decrease of 0.7 mmHg, p = 3.8e–6) and Group 2 (baseline ICP 18.1 ± 2.7 mmHg, decrease of 2 mmHg, p = 3.7e–6). However, a persistent ICP reduction after therapy was seen only in Group 2. There were no significant differences between mean CPP and MAP comparing ICP before and after PROM in all groups. No adverse side effects of PROM were observed.

Conclusions

Physiotherapy with PROM can be used safely in patients with acute neurological diseases, even if ICP is elevated before therapy.     

The Physiologic Effects of Indomethacin Test on CPP and ICP in Severe Traumatic Brain Injury (sTBI)

Background

Refractory intracranial hypertension (RICH) is associated with high mortality in severe traumatic brain injury (sTBI). Indomethacin (INDO) can decrease intracranial cerebral pressure (ICP) improving cerebral pressure perfusion (CPP). Our aim was to determine modifications in ICP and CPP following INDO in RICH secondary to sTBI.

Methods

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by continuous 2-h infusion period (0.5 mg/kg/h). Clinical outcome was assessed at 30 days according to Glasgow Outcome Scale (GOS). Differences in ICP and CPP values were assessed using repeated-measures ANOVA. Receiver operating characteristic curve (AUC) was used for discrimination in predicting 30-day survival and good functional outcome (GOS 4 or 5). Analysis of INDO safety profile was also conducted.

Results

Thirty-two patients were included. Median GCS score was 6 (interquartile range: 4–7). The most frequent CT finding was the evacuated mass lesion (EML) according to Marshall classification (28.1 %). Mortality rate was 34.4 %. Within 15 min of INDO infusion, ICP decreased (Δ%: ?54.6 %; P < 0.0001), CPP increased (Δ%: +44.0 %; P < 0.0001), and the remaining was stable during the entire infusion period. Patients with good outcome (n = 12) showed a greater increase of CPP during INDO test (P = 0.028). CPP response to INDO test discriminated moderately well surviving patients (AUC = 0.751; P = 0.0098) and those with good functional recovery (AUC = 0.763; P = 0.0035) from those who died and from those with worse functional outcome, respectively. No adverse events were observed.

Conclusions

INDO appears effective in reducing ICP and improving CPP in RICH. INDO test could be a useful tool in identifying RICH patients with favorable outcome. Future studies are needed.     

Blood Transfusion is an Important Predictor of Hospital Mortality Among Patients with Aneurysmal Subarachnoid Hemorrhage

Background

Red blood cell (RBC) transfusion after aneurysmal subarachnoid hemorrhage (aSAH) has been associated with increased mortality but prior studies have not adequately adjusted for transfusion-indication bias.

Methods

This is a retrospective study of consecutive aSAH patients admitted to the intensive care units of two academic medical centers over a 7-year period. Data collection included demographics, World Federation of Neurosurgical Surgeons score (WFNS), modified Fisher score (mFisher), admission and nadir hemoglobin (Hb) level, vasospasm, cerebral infarction, acute lung injury, and hospital mortality. The association between RBC transfusion and mortality was evaluated using a multivariate logistic regression analysis using the propensity for RBC transfusion as a covariate.

Results

We identified 318 patients. The median age was 54 years (46, 65), and 204 (64 %) were females. Hospital mortality was 13 % (42/318). Seventy-two (23 %) patients were transfused. Predictors of transfusion were admit and nadir Hb levels (p < 0.001), age (p = 0.02), gender (0.008), WFNS score (p < 0.001), mFisher score (p = 0.009), surgical versus endovascular treatment (p < 0.001) and moderate to severe vasospasm (p = 0.025) were predictors of transfusion. After adjustment for probability of receiving RBC transfusion, APACHE IV and nadir Hb, transfusion remained independently associated with hospital mortality (OR 3.16, 95 % CI = 1.02–9.69, p = 0.047).

Conclusions

Among patients with aSAH, RBC transfusion was independently associated with an increased mortality after adjustment for the most common clinical indications for transfusion.     

The role of stress sensitization in progression of posttraumatic distress following deployment

Purpose

Military personnel exposed to combat are at risk for experiencing post-traumatic distress that can progress over time following deployment. We hypothesized that progression of post-traumatic distress may be related to enhanced susceptibility to post-deployment stressors. This study aimed at examining the concept of stress sensitization prospectively in a sample of Dutch military personnel deployed in support of the conflicts in Afghanistan.

Method

In a cohort of soldiers (N = 814), symptoms of post-traumatic stress disorder (PTSD) were assessed before deployment as well as 2, 7, 14, and 26 months (N = 433; 53 %) after their return. Data were analyzed using latent growth modeling. Using multiple group analysis, we examined whether high combat stress exposure during deployment moderated the relation between post-deployment stressors and linear change in post-traumatic distress after deployment.

Results

A higher baseline level of post-traumatic distress was associated with more early life stressors (standardized regression coefficient = 0.30, p < 0.001). In addition, a stronger increase in posttraumatic distress during deployment was associated with more deployment stressors (standardized coefficient = 0.21, p < 0.001). A steeper linear increase in posttraumatic distress post-deployment (from 2 to 26 months) was predicted by more post-deployment stressors (standardized coefficient = 0.29, p < 0.001) in high combat stress exposed soldiers, but not in a less combat stress exposed group. The group difference in the predictive effect of post-deployment stressors on progression of post-traumatic distress was significant (χ²(1) = 7.85, p = 0.005).

Conclusions

Progression of post-traumatic distress following combat exposure may be related to sensitization to the effects of post-deployment stressors during the first year following return from deployment.     

A Prospective Evaluation of Labetalol Versus Nicardipine for Blood Pressure Management in Patients with Acute Stroke

Introduction

Acute hypertension is common following stroke and contributes to poor outcomes. Labetalol and nicardipine are often used for acute hypertension but there are little data comparing the two. This study is to evaluate the therapeutic response and tolerability of these two agents following acute stroke.

Methods

This is a prospective, pseudo-randomized study comparing labetalol and nicardipine for blood pressure (BP) management in acute stroke patients. Patients who presented to the emergency department (ED) with confirmed hemorrhagic or ischemic stroke received either labetalol or nicardipine for 24 h from ED admission. Therapeutic response was assessed by achievement of goal BP, time spent within goal, and variability in BP. Clinical outcomes including length of stay, clinical status at discharge, and in-hospital mortality were recorded.

Results

54 patients were enrolled (labetalol = 28; nicardipine = 26) with 25 ± 6 BP measurements per patient. Majority of patients had a hemorrhagic stroke and baseline characteristics were similar between groups. All patients who received nicardipine achieved goal BP compared to 17 (61 %) in the labetalol group (p < 0.001) with 89 % nicardipine-treated patients achieved goal BP within 60 min of drug initiation versus 25 % in labetalol group (p < 0.001). Nicardipine group had better maintenance of BP, a greater percentage of time spent within goal, and significantly less BP variability compared to labetalol group (p < 0.001). Less rescue antihypertensive agents were given to nicardipine group than labetalol group (p < 0.001). The incidences of adverse drug events were similar between groups and there were no differences in clinical outcomes.

Conclusion

In acutely hypertensive stroke patients, superior therapeutic response was achieved with nicardipine versus labetalol. Despite this, there was no demonstrable difference in clinical outcomes.     

Seizures Do Not Increase In-Hospital Mortality After Intracerebral Hemorrhage in the Nationwide Inpatient Sample

Background

Seizures are common after intracerebral hemorrhage (ICH) but their impact on outcome is uncertain and prophylactic anti-convulsant use is controversial. We hypothesized that seizures would not increase the risk of in-hospital mortality in a large administrative database.

Methods

The study population included patients in the 2006 Nationwide Inpatient Sample over the age of 18 with a principal diagnosis of ICH (ICD9 = 431). Subjects with a secondary diagnosis of aneurysm, arterio-venous malformation, brain tumor, or traumatic brain injury were excluded. Seizures were defined by ICD9 codes (345.0x–345.5x, 345.7x–345.9x, 780.39). Logistic regression was used to quantify the relationship between seizures and in-hospital mortality. Pre-specified subgroups included age strata, length of stay, and invasive procedures.

Results

13,033 subjects met all eligibility criteria, of which 1,430 (11.0 %) had a secondary diagnosis of seizure. Subjects with seizure were younger (64 vs. 70 years, p < 0.001), more likely to get craniectomy (2.1 vs. 1.2 %, p = 0.006), ventriculostomy (8.5 vs. 6.0 %, p < 0.001), intubation (32.2 vs. 25.9 %, p < 0.001), and tracheostomy (6.4 vs. 4.2 %, p < 0.001). Seizure patients had lower in-hospital mortality (24.3 vs. 28.0 %, p = 0.003). In a multivariable model incorporating patient and hospital level variables, seizures were associated with reduced odds of in-hospital death (OR = 0.62, 95 % CI 0.52–0.75).

Conclusions

A secondary diagnosis of seizure after ICH was not associated with increased in-hospital death overall or in any of the pre-specified subgroups; however, there may be residual confounding by severity. These findings do not support a need for routine prophylactic anti-epileptic drug use after ICH.     

Treadmill gait training improves baroreflex sensitivity in Parkinson’s disease

Background

Partial weight supported treadmill gait training (PWSTT) is widely used in rehabilitation of gait in patient with Parkinson’s Diseases (PD). However, its effect on blood pressure variability (BPV) and baroreflex sensitivity (BRS) in PD has not been studied.

Aim

To evaluate the effect of conventional and treadmill gait training on BPV components and BRS.

Methods

Sixty patients with idiopathic PD were randomized into three groups. Twenty patients in control group were on only stable medication, 20 patients in conventional gait training (CGT) group (Stable medication with CGT) and 20 patients in PWSTT group (Stable medication with 20 % PWSTT). The CGT and PWSTT sessions were given for 30 min per day, 4 days per week, for 4 weeks (16 sessions). Groups were evaluated in their best ‘ON’ states. The beat-to-beat finger blood pressure (BP) was recorded for 10 min using a Finometer instrument (Finapres Medical Systems, The Netherlands). BPV and BRS results were derived from artifact-free 5-min segments using Nevrocard software.

Results

BRS showed a significant group with time interaction (F = 6.930; p = 0.003). Post-hoc analysis revealed that PWSTT group showed significant improvement in BRS (p < 0.001) after 4 weeks of training. No significant differences found in BPV parameters; systolic BP, diastolic BP, co-variance of systolic BP and low frequency component of systolic BP.

Conclusions

Four weeks of PWSTT significantly improves BRS in patients with PD. It can be considered as a non-invasive method of influencing BRS for prevention of orthostatic BP fall in patients with PD.     

ICP Versus Laser Doppler Cerebrovascular Reactivity Indices to Assess Brain Autoregulatory Capacity

Background

To explore the relationship between various autoregulatory indices in order to determine which approximate small vessel/microvascular (MV) autoregulatory capacity most accurately.

Methods

Utilizing a retrospective cohort of traumatic brain injury patients (N = 41) with: transcranial Doppler (TCD), intracranial pressure (ICP) and cortical laser Doppler flowmetry (LDF), we calculated various continuous indices of autoregulation and cerebrovascular responsiveness: A. ICP derived [pressure reactivity index (PRx)—correlation between ICP and mean arterial pressure (MAP), PAx—correlation between pulse amplitude of ICP (AMP) and MAP, RAC—correlation between AMP and cerebral perfusion pressure (CPP)], B. TCD derived (Mx—correlation between mean flow velocity (FVm) and CPP, Mx_a—correlation between FVm and MAP, Sx—correlation between systolic flow velocity (FVs) and CPP, Sx_a—correlation between FVs and MAP, Dx—correlation between diastolic flow index (FVd) and CPP, Dx_a—correlation between FVd and MAP], and LDF derived (Lx—correlation between LDF cerebral blood flow [CBF] and CPP, Lx_a—correlation between LDF-CBF and MAP). We assessed the relationship between these indices via Pearson correlation, Friedman test, principal component analysis (PCA), agglomerative hierarchal clustering (AHC), and k-means cluster analysis (KMCA).

Results

LDF-based autoregulatory index (Lx) was most associated with TCD-based Mx/Mx_a and Dx/Dx_a across Pearson correlation, PCA, AHC, and KMCA. Lx was only remotely associated with ICP-based indices (PRx, PAx, RAC). TCD-based Sx/Sx_a was more closely associated with ICP-derived PRx, PAx and RAC. This indicates that vascular-derived indices of autoregulatory capacity (i.e., TCD and LDF based) covary, with Sx/Sx_a being the exception, whereas indices of cerebrovascular reactivity derived from pulsatile CBV (i.e., ICP indices) appear to not be closely related to those of vascular origin.

Conclusions

Transcranial Doppler Mx is the most closely associated with LDF-based Lx/Lx_a. Both Sx/Sx-a and the ICP-derived indices appear to be dissociated with LDF-based cerebrovascular reactivity, leaving Mx/Mx-a as a better surrogate for the assessment of cortical small vessel/MV cerebrovascular reactivity. Sx/Sx_a cocluster/covary with ICP-derived indices, as seen in our previous work.

     

Coagulopathy Disproportionately Predisposes to Lobar Intracerebral Hemorrhage

Background

Anticoagulation increases the risk of intracerebral hemorrhage (ICH), yet whether different underlying disease processes are equally affected is unknown. We tested the hypothesis that coagulopathy, measured by admission international normalized ratio (INR), disproportionately increases the risk for lobar hemorrhages.

Methods

Patients with primary ICH were enrolled into a registry between December 2006 and February 2012 with prospective data acquisition and systematic follow up. Logistic regression was used to test whether lobar versus deep ICH location was independently associated with INR, and then whether INR had an influence on mortality. Spearman’s correlation coefficient was used to test for an association between INR and hematoma volume separately in the lobar and deep ICH groups.

Results

221 patients were studied. Patients with lobar ICH were older (71 vs. 62 years old, p < 0.001) and more likely to have prior ICH (10 vs. 0 %, p < 0.001). INR >1.4 was observed on admission more frequently in lobar versus deep ICH (19 vs. 8 %, p = 0.02). Lobar ICH location was independently associated with INR >1.4 (OR: 2.51, 95 % CI: 1.03–6.14, p = 0.043). ICH volume correlated with INR in lobar ICH (p = 0.009), but not deep ICH (p = 0.8). Death at 1 month was independently associated with INR >1.4 (OR: 7.6, 95 % CI: 2.4–24.1, p = 0.001) after correction for the ICH Score.

Conclusions

Abnormal coagulation occurs disproportionally in lobar versus deep ICH, and is associated with larger ICH volumes and higher mortality. These findings suggest a unique risk interaction between coagulopathy and underlying brain pathology due to cerebral amyloid angiopathy.     

The Neurological Wake-up Test Does not Alter Cerebral Energy Metabolism and Oxygenation in Patients with Severe Traumatic Brain Injury

Background

The neurological wake-up test (NWT) is used to monitor the level of consciousness in patients with traumatic brain injury (TBI). However, it requires interruption of sedation and may elicit a stress response. We evaluated the effects of the NWT using cerebral microdialysis (MD), brain tissue oxygenation (Pb_tiO₂), jugular venous oxygen saturation (SjvO₂), and/or arterial-venous difference (AVD) for glucose, lactate, and oxygen in patients with severe TBI.

Methods

Seventeen intubated TBI patients (age 16–74 years) were sedated using continuous propofol infusion. All patients received intracranial pressure (ICP) and cerebral perfusion pressure (CPP) monitoring in addition to MD, Pb_tiO₂ and/or SjvO₂. Up to 10 days post-injury, ICP, CPP, Pb_tiO₂ (51 NWTs), MD (49 NWTs), and/or SjvO₂ (18 NWTs) levels during propofol sedation (baseline) and NWT were compared. MD was evaluated at a flow rate of 1.0 μL/min (28 NWTs) or the routine 0.3 μL/min rate (21 NWTs).

Results

The NWT increased ICP and CPP levels (p < 0.05). Compared to baseline, interstitial levels of glucose, lactate, pyruvate, glutamate, glycerol, and the lactate/pyruvate ratio were unaltered by the NWT. Pathological SjvO₂ (<50 % or >71 %; n = 2 NWTs) and Pb_tiO₂ (<10 mmHg; n = 3 NWTs) values were rare at baseline and did not change following NWT. Finally, the NWT did not alter the AVD of glucose, lactate, or oxygen.

Conclusions

The NWT-induced stress response resulted in increased ICP and CPP levels although it did not negatively alter focal neurochemistry or cerebral oxygenation in TBI patients.     

Goal Directed Brain Tissue Oxygen Monitoring Versus Conventional Management in Traumatic Brain Injury: An Analysis of In Hospital Recovery

Background

Brain tissue oxygen monitoring (pBtO2) has been advocated in the treatment of patients with severe traumatic brain injuries (TBI); however, controversy exists regarding the improvements that pBtO2 monitoring provides. The objective of our study was to evaluate our experience and effect on mortality with goal directed pBtO2 monitoring for severe TBI compared to traditional ICP/CPP monitoring.

Methods

All patients admitted with severe TBI (GCS < 8) to our Level 1 trauma center from June 2007 through June 2009 were retrospectively analyzed. All patients had ICP monitoring and pBtO2 monitors were placed based on the current practices of the attending neurosurgeon producing two temporally matched cohorts of patients with and without pBtO2 monitors. Exclusion criteria were age <18 years and survival <24 h. Goal-directed therapy was utilized in all patients to maintain ICP <20 mmHg and CPP >60 mmHg. Patients with pBtO2 monitors were managed to maintain a level >20 mmHg.

Results

74 patients were treated for severe TBI over the 2-year study period with 37 patients in each group. Both groups were similar in age, sex, and admission Glascow Coma Score(GCS).The pBtO2-monitored group did, however, have significantly lower injury severity score [26 (25–30) vs. 30 (26–36), p = 0.03] and AIS Chest [0 (0–0) vs. 2 (0–3), p = 0.02]. There was no survival difference found (64.9 vs. 54.1 %, p = 0.34). No difference with respect to discharge GCS or discharge Functional Independence Measure score was identified.

Conclusions

Compared with ICP/CPP-directed therapy alone, the addition of pBtO2 monitoring did not provide a survival or functional status improvement at discharge. The true clinical benefit of pBtO2 monitoring will require further study.     

Critical Closing Pressure During Intracranial Pressure Plateau Waves

Background

Critical closing pressure (CCP) denotes a threshold of arterial blood pressure (ABP) below which brain vessels collapse and cerebral blood flow ceases. Theoretically, CCP is the sum of intracranial pressure (ICP) and arterial wall tension (WT). The aim of this study is to describe the behavior of CCP and WT during spontaneous increases of ICP, termed plateau waves, in order to quantify ischemic risk.

Methods

To calculate CCP, we used a recently introduced multi-parameter method (CCPm) which is based on the modulus of cerebrovascular impedance. CCP is derived from cerebral perfusion pressure, ABP, transcranial Doppler estimators of cerebrovascular resistance and compliance, and heart rate. Arterial WT was estimated as CCPm-ICP. The clinical data included recordings of ABP, ICP, and transcranial Doppler-based blood flow velocity from 38 events of ICP plateau waves, recorded in 20 patients after head injury.

Results

Overall, CCPm increased significantly from 51.89 ± 8.76 mmHg at baseline ICP to 63.31 ± 10.83 mmHg at the top of the plateau waves (mean ± SD; p < 0.001). Cerebral arterial WT decreased significantly during plateau waves by 34.3 % (p < 0.001), confirming their vasodilatatory origin. CCPm did not exhibit the non-physiologic negative values that have been seen with traditional methods for calculation, therefore rendered a more plausible estimation of CCP.

Conclusions

Rising CCP during plateau waves increases the probability of cerebral vascular collapse and zero flow when the difference: ABP–CCP (the “collapsing margin”) becomes zero or negative.     

Alteration of skin laser-Doppler flux response to local cooling in gestational hypertension

Purpose

The pathophysiology of the pregnancy-induced hypertension is still poorly understood, especially with regard to the central autonomic nervous system control and peripheral vascular factors.

Methods

Our study therefore aimed to investigate simultaneously the responses of blood pressure, heart rate, heart rate variability (HRV), and laser-Doppler (LD) flux to local cooling in healthy non-pregnant women (N = 12), in pregnant women with normal pregnancy (N = 16) and in women with gestational hypertension (N = 10).

Results

The direct and indirect LD flux responses to local cold exposure were diminished in normotensive pregnant females (Dunnett’s test, p < 0.05) when compared to non-pregnant females with normal menstrual cycle, but not in females with pregnancy-induced hypertension. In addition, blood pressure increased and heart rate decreased during cold exposure only in normotensive pregnant females, but not in pregnant hypertensive females (paired t test, p < 0.05). Simultaneously calculated heart rate variability total power of HRV and LF power values typically increased during local cold provocation test in non-pregnant females and in normotensive pregnant females (paired t test, p < 0.05). In hypertensive pregnant females HRV indices remained unchanged.

Conclusion

Our results indicate that the cardiovascular reactivity adaptation seen in normal pregnancy is absent in gestational hypertension.     

Cerebral Critical Closing Pressure: Is the Multiparameter Model Better Suited to Estimate Physiology of Cerebral Hemodynamics?

Background

Cerebral critical closing pressure (CrCP) is the level of arterial blood pressure (ABP) at which small brain vessels close and blood flow stops. This value is always greater than intracranial pressure (ICP). The difference between CrCP and ICP is explained by the tone of the small cerebral vessels (wall tension). CrCP value is used in several dynamic cerebral autoregulation models. However, the different methods for calculation of CrCP show frequent negative values. These findings are viewed as a methodological limitation. We intended to evaluate CrCP in patients with severe traumatic brain injury (TBI) with a new multiparameter impedance-based model and compare it with results found earlier using a transcranial Doppler (TCD)–ABP pulse waveform-based method.

Methods

Twelve severe TBI patients hospitalized during September 2005–May 2007. Ten men, mean age 32 years (16–61). Four had decompressive craniectomies (DC); three presented anisocoria. Patients were monitored with TCD cerebral blood flow velocity (FV), invasive ABP, and ICP. Data were acquired at 50 Hz with an in-house developed data acquisition system. We compared the earlier studied “first harmonic” method (M1) results with results from a new recently developed (M2) “multiparameter method.”

Results

M1: In seven patients CrCP values were negative, reaching ?150 mmHg. M2: All positive values; only one lower than ICP (ICP 60 mmHg/ CrCP 57 mmHg). There was a significant difference between M1 and M2 values (M1 < M2) and between ICP and M2 (M2 > ICP).

Conclusion

M2 results in positive values of CrCP, higher than ICP, and are physiologically interpretable.

     

Withdrawal of Technological Life Support Following Subarachnoid Hemorrhage

Background

Prognostication of mortality or severe disability often prompts withdrawal of technological life support in patients following aneurysmal subarachnoid hemorrhage (aSAH). We assessed admission factors impacting decisions to withdraw treatment after aSAH.

Methods

Prospectively collected data of aSAH patients admitted to our institution between 1991 and 2009 were reviewed. Patients given comfort care measures were identified, including early withdrawal of treatment (<72 h after admission). Independent predictors of treatment withdrawal were assessed with multivariable analysis.

Results

The study included 1,134 patients, of whom 72 % were female, 58 % white, and 38 % black or African-American. Mean age was 52.5 ± 14.0 years. In-hospital mortality was 18.3 %. Of the 207 patients who died, treatment was withdrawn in 72 (35 %) and comfort measures instituted early in 31 (15 %). Among patients who died, WOLST was associated with older age (63.6 ± 14.2 years, WOLST vs. 55.6 ± 13.7 years, no WOLST, p < 0.001); GCS score <8 (62 % of WOLST vs. 44 % with no WOLST, p = 0.010); HH >3 (72 % of WOLST vs. 53 % with no WOLST, p = 0.008); and hydrocephalus (81 % of WOLST vs. 63 % with no WOLST, p = 0.009). Independent predictors of WOLST were poorer Hunt and Hess grade (AOR 1.520, 95 % CI 1.160–1.992, p = 0.002) and older age (AOR 1.045, 95 % CI 1.022–1.068, p < 0.001) with the latter also impacting early WOLST decisions.

Conclusions

Older age and poor clinical grade on presentation predicted WOLST, and age predicted decisions to withdraw treatment earlier following aSAH. While based on prognosis, and in some cases patient wishes, this may also constitute a self-fulfilling prophecy in others.