Cerebral and extracerebral vulnerability to hypoxic insults after diffuse traumatic brain injury in rats.

The post-traumatic brain vulnerability suggests that after traumatic brain injury (TBI), the brain may be more susceptible to posttraumatic hypoxic insults. This concept could be extended to 'peripheral' organs, as non-neurologic organ failure is common after TBI. This study aims to characterize and quantify cerebral and extracerebral tissue hypoxia with pimonidazole resulting from a standardized hypoxia-hypotension (HH) phase occurring after a diffuse experimental TBI in rats. Rats were allocated to Sham (n=5), TBI (n=7), HH (n=7) and TBI+HH (n=7) groups. Then, pimonidazole was injected and brain, liver, heart and kidneys were analysed. In the cerebral cortex, post-treatment hypoxia was higher in TBI+HH group than Sham group (p=0.003), HH group (p=0.003) and TBI group (p=0.002). Large trends in thalamus, hippocampus and striatum for the TBI+HH group compared to the other groups were observed. For the heart and liver, the 4 groups were comparable. For the kidneys, post-treatment hypoxia was higher in the TBI group compared to the Sham and HH groups, but not more than TBI+HH group. This study reveals that a posttraumatic hypoxic insult occurring after a severe TBI has major hypoxic consequences on brain structures. However, TBI by itself appears to induce renal hypoxia that is not enhanced by posttraumatic hypoxic insult.

The Doppler renal resistive index for early detection of acute kidney injury after hip fracture.

BACKGROUND: Postoperative acute kidney injury (AKI) is linked to an increase in morbidity and mortality, particularly in elderly populations. This study's aim was to assess the accuracy of the Doppler renal resistive index (RI) in detecting AKI at an early stage after hip fracture surgery. METHODS: This prospective single-centre study included 48 patients suffering hip fractures requiring surgery and who presented risk factors for the development of AKI. The RI was calculated preoperatively and postoperatively in patients without pain and with haemodynamic and respiratory stability. The occurrence of AKI was determined by measurements of serum creatinine according to AKIN criteria. RESULTS: Twenty-nine patients (60%) developed AKI during the first five postoperative days, without need for dialysis. The RI was increased in patients who developed postoperative AKI 0.68 (0.67-0.71) vs. 0.72 (0.7-0.73); P=0.014 for the preoperative index; and 0.6 (0.58-0.68) vs. 0.74 (0.71-0.76); P<0.0001 for the postoperative index. A postoperative index superior or equal to 0.706 is a marker for the early detection of AKI with a high sensitivity and a high specificity (76% and 89%, respectively). CONCLUSION: The calculation of the RI during the perioperative periods of hip fracture surgery predicts early and effectively the postoperative occurrence of AKI, thus allowing treatment to be anticipated so as to improve patient prognosis.

Noninvasive assessment of hemodynamic response to a fluid challenge using femoral Doppler in critically ill ventilated patients.

PURPOSE: The purpose of the study is to determine if femoral artery blood flow Doppler parameters can assess cardiac response to a fluid challenge (FC). MATERIALS AND METHODS: We prospectively recorded in 52 critically ill ventilated patients' velocity time integral variation (%VTIf) and maximal systolic velocity variation (%Vfmax) derived from femoral Doppler analysis and aortic velocity time integral variation registered on transthoracic echocardiography before and after an FC of 500-mL saline. RESULTS: According to Pearson coefficient, %Vfmax and %VTIf were found to be positively correlated with aortic velocity time integral variation (r(2) = 0.46 and 0.51, respectively; P < .0001) and were significantly different between responder patients and nonresponders (11% ± 3.4% vs 5.9% ± 4.3% and 14.9% ± 4.2% vs 5.5% ± 5.5%, respectively; P < .0001). Increase of %VTIf 10% or higher and %Vfmax 7% or higher after an FC showed a sensitivity of 80% and 84%, a specificity of 85% and 73%, and an area under the curve of 0.905 and 0.851, respectively, for discriminating responder and nonresponder patients. CONCLUSION: Variation of femoral Doppler parameters before and after FC mirrors cardiac response to fluid loading. This tool could be considered as an alternative to transthoracic echocardiography in case of poor thoracic insonation.

Lactate clearance for death prediction in severe sepsis or septic shock patients during the first 24 hours in Intensive Care Unit: an observational study.

BACKGROUND: This study was design to investigate the prognostic value for death at day-28 of lactate course and lactate clearance during the first 24 hours in Intensive Care Unit (ICU), after initial resuscitation. METHODS: Prospective, observational study in one surgical ICU in a university hospital. Ninety-four patients hospitalized in the ICU for severe sepsis or septic shock were included. In this septic cohort, we measured blood lactate concentration at ICU admission (H0) and at H6, H12, and H24. Lactate clearance was calculated as followed: [(lactateinitial - lactatedelayed)/ lactateinitial] x 100%]. RESULTS: The mean time between severe sepsis diagnosis and H0 (ICU admission) was 8.0 ± 4.5 hours. Forty-two (45%) patients died at day 28. Lactate clearance was higher in survivors than in nonsurvivors patients for H0-H6 period (13 ± 38% and -13 ± 7% respectively, p = 0.021) and for the H0-H24 period (42 ± 33% and -17 ± 76% respectively, p < 0.001). The best predictor of death at day 28 was lactate clearance for the H0-H24 period (AUC = 0.791; 95% CI 0.6-0.85). Logistic regression found that H0-H24 lactate clearance was independently correlated to a survival status with a p = 0.047 [odds ratio = 0.35 (95% CI 0.01-0.76)]. CONCLUSIONS: During the first 24 hr in the ICU, lactate clearance was the best parameter associated with 28-day mortality rate in septic patients. Protocol of lactate clearance-directed therapy should be considered in septic patients, even after the golden hours.

Cerebral hemodynamic changes induced by a lumbar puncture in good-grade subarachnoid hemorrhage.

BACKGROUND: Patients with good-grade subarachnoid hemorrhage (SAH) are those without initial neurological deficit. However, they can die or present severe deficit due to secondary insult leading to brain ischemia. After SAH, in a known context of energy crisis, vasospasm, hydrocephalus and intracranial hypertension contribute to unfavorable outcome. Lumbar puncture (LP) is sometimes performed in an attempt to reduce intracranial pressure (ICP) and release headaches. We hypothesize that in good-grade SAH patients, a 20-ml LP releases headaches, reduces ICP and improves cerebral blood flow (CBF) as measured with O(15) PET scan. METHODS: Six good-grade (WFNS grade 1or 2) SAH patients (mean age 48 years, 2 women, 4 men) were prospectively included. All aneurysms (4 anterior communicating artery and 2 right middle cerebral artery) were coiled at day 1. Patients were managed according to our local protocol. LP was performed for severe headache (VAS >7) despite maximal painkiller treatment. Patients were included when the LP was clinically needed. The 20-ml LP was done in the PET scan (mean delay between SAH and LP: 3.5 days). LP allows hydrostatic measurement of ICP. Arterial blood pressure (ABP) was noninvasively gauged with photoplethysmography. Every signal was monitored and analyzed off-line. Regional CBF (rCBF) was measured semiquantitatively with O(15) PET before and after LP. Then we calculated the difference between baseline and post-LP condition for each area: positive value means augmentation of rCBF after the LP, negative value means reduction of rCBF. Individual descriptive analysis of CBF was first performed for each patient; then a statistical group analysis was done with SPM for all voxels using t statistics converted to Z scores (p < 0.01, Z score >3.2). RESULTS: A 20-ml LP yielded a reduction in pain (-4), a drop in ICP (24.3 ± 12.5 to 6.9 ± 4.7 mm Hg), but no change in ABP. Descriptive and statistical image analysis showed a heterogeneous and biphasic change in cerebral hemodynamics: rCBF was not kept constant and either augmented or decreased after the drop in ICP. Hence, cerebrovascular reactivity was spatially heterogeneous within the brain. rCBF seems to augment in the brain region roughly close to the bleed and to be reduced in the rest of the brain, with a rough plane of symmetry. CONCLUSIONS: In good-grade SAH, LP releases headaches and lowers ICP. LP and the drop in ICP have a heterogeneous and biphasic effect on rCBF, suggesting that cerebrovascular reactivity is not spatially homogeneous within the brain.