CO(2) and indomethacin vasoreactivity in patients with head injury

Relationships of Jugular Bulb Parameters with Cerebral Perfusion and Metabolism After Resuscitation from Cardiac Arrest: A Post-Hoc Analysis of Experimental Studies Using a Minipig Model

BACKGROUND

Cerebral blood flow (CBF) decreases in the first few hours or days following resuscitation from cardiac arrest, increasing the risk of secondary cerebral injury. Using data from experimental studies performed in minipigs, we investigated the relationships of parameters derived from arterial and jugular bulb blood gas analyses and lactate levels (jugular bulb parameters), which have been used as indicators of cerebral perfusion and metabolism, with CBF and the cerebral lactate to creatine ratio measured with dynamic susceptibility contrast magnetic resonance imaging and proton magnetic resonance spectroscopy, respectively.

METHODS

We retrospectively analyzed 36 sets of the following data obtained during the initial hours following resuscitation from cardiac arrest: percent of measured CBF relative to that at the prearrest baseline (%CBF), cerebral lactate to creatine ratio, and jugular bulb parameters, including jugular bulb oxygen saturation, jugular bulb lactate, arterial-jugular bulb oxygen content difference, cerebral extraction of oxygen, jugular bulb-arterial lactate content difference, lactate oxygen index, estimated respiratory quotient, and arterial-jugular bulb hydrogen ion content difference. Linear mixed-effects models were constructed to examine the effects of each jugular bulb parameter on the %CBF and cerebral lactate to creatine ratio.

RESULTS

The arterial-jugular bulb oxygen content difference (P = 0.047) and cerebral extraction of oxygen (P = 0.030) had a significant linear relationship with %CBF, but they explained only 12.0% (95% confidence interval [CI] 0.002-0.371) and 14.2% (95% CI 0.005-0.396) of the total %CBF variance, respectively. The arterial-jugular bulb hydrogen ion content difference had a significant linear relationship with cerebral lactate to creatine ratio (P = 0.037) but explained only 13.8% (95% CI 0.003-0.412) of the total variance in the cerebral lactate to creatine ratio. None of the other jugular bulb parameters were related to the %CBF or cerebral lactate to creatine ratio.

CONCLUSIONS

In conclusion, none of the jugular bulb parameters appeared to provide sufficient information on cerebral perfusion and metabolism in this setting.

Short-term mild hyperventilation on intracranial pressure, cerebral autoregulation, and oxygenation in acute brain injury patients: a prospective observational study

Current guidelines suggest a target of partial pressure of carbon dioxide (PaCO2) of 32-35 mmHg (mild hypocapnia) as tier 2 for the management of intracranial hypertension. However, the effects of mild hyperventilation on cerebrovascular dynamics are not completely elucidated. The aim of this study is to evaluate the changes of intracranial pressure (ICP), cerebral autoregulation (measured through pressure reactivity index, PRx), and regional cerebral oxygenation (rSO2) parameters before and after induction of mild hyperventilation. Single center, observational study including patients with acute brain injury (ABI) admitted to the intensive care unit undergoing multimodal neuromonitoring and requiring titration of PaCO2 values to mild hypocapnia as tier 2 for the management of intracranial hypertension. Twenty-five patients were included in this study (40% female), median age 64.7 years (Interquartile Range, IQR = 45.9-73.2). Median Glasgow Coma Scale was 6 (IQR = 3-11). After mild hyperventilation, PaCO2 values decreased (from 42 (39-44) to 34 (32-34) mmHg, p < 0.0001), ICP and PRx significantly decreased (from 25.4 (24.1-26.4) to 17.5 (16-21.2) mmHg, p < 0.0001, and from 0.32 (0.1-0.52) to 0.12 (-0.03-0.23), p < 0.0001). rSO2 was statistically but not clinically significantly reduced (from 60% (56-64) to 59% (54-61), p < 0.0001), but the arterial component of rSO2 (ΔO2Hbi, changes in concentration of oxygenated hemoglobin of the total rSO2) decreased from 3.83 (3-6.2) μM.cm to 1.6 (0.5-3.1) μM.cm, p = 0.0001. Mild hyperventilation can reduce ICP and improve cerebral autoregulation, with minimal clinical effects on cerebral oxygenation. However, the arterial component of rSO2 was importantly reduced. Multimodal neuromonitoring is essential when titrating PaCO2 values for ICP management.

Indomethacin-responsive headaches-A narrative review

BACKGROUND

Indomethacin is a nonsteroidal anti-inflammatory drug whose mechanism of action in certain types of headache disorders remains unknown. The so-called indomethacin-responsive headache disorders consist of a group of conditions with a very different presentation that have a particularly good response to indomethacin. The response is so distinct as to be used in the definition of two: hemicrania continua and paroxysmal hemicrania.

METHODS

This is a narrative literature review. PubMed and the Cochrane databases were used for the literature search.

RESULTS

We review the main pharmacokinetic and pharmacodynamics properties of indomethacin useful for daily practice. The proposed mechanisms of action of indomethacin in the responsive headache disorders, including its effect on cerebral blood flow and intracranial pressure, with special attention to nitrergic mechanisms, are covered. The current evidence for its use in primary headache disorders, such as some trigeminal autonomic cephalalgias, cough, hypnic, exertional or sexual headache, and migraine will be covered, as well as its indication for secondary headaches, such as those of posttraumatic origin.

CONCLUSION

Increasing understanding of the mechanism(s) of action of indomethacin will enhance our understanding of the complex pathophysiology that might be shared by indomethacin-sensitive headache disorders.

Hyperventilation in Adult TBI Patients: How to Approach It?

Hyperventilation is a commonly used therapy to treat intracranial hypertension (ICTH) in traumatic brain injury patients (TBI). Hyperventilation promotes hypocapnia, which causes vasoconstriction in the cerebral arterioles and thus reduces cerebral blood flow and, to a lesser extent, cerebral blood volume effectively, decreasing temporarily intracranial pressure. However, hyperventilation can have serious systemic and cerebral deleterious effects, such as ventilator-induced lung injury or cerebral ischemia. The routine use of this therapy is therefore not recommended. Conversely, in specific conditions, such as refractory ICHT and imminent brain herniation, it can be an effective life-saving rescue therapy. The aim of this review is to describe the impact of hyperventilation on extra-cerebral organs and cerebral hemodynamics or metabolism, as well as to discuss the side effects and how to implement it to manage TBI patients.

Indomethacin for intracranial hypertension secondary to severe traumatic brain injury in adults

BACKGROUND

Among people who have suffered a traumatic brain injury, increased intracranial pressure continues to be a major cause of early death; it is estimated that about 11 people per 100 with traumatic brain injury die. Indomethacin (also known as indometacin) is a powerful cerebral vasoconstrictor that can reduce intracranial pressure and, ultimately, restore cerebral perfusion and oxygenation. Thus, indomethacin may improve the recovery of a person with traumatic brain injury.

OBJECTIVES

To assess the effects of indomethacin for adults with severe traumatic brain injury.

SEARCH METHODS

We ran the searches from inception to 23 August 2019. We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 8) in the Cochrane Library, Ovid MEDLINE, Ovid Embase, CINAHL Plus (EBSCO), four other databases, and clinical trials registries. We also screened reference lists and conference abstracts, and contacted experts in the field.

SELECTION CRITERIA

Our search criteria included randomised controlled trials (RCTs) that compared indomethacin with any control in adults presenting with severe traumatic brain injury associated with elevated intracranial pressure, with no previous decompressive surgery.

DATA COLLECTION AND ANALYSIS

Two review authors independently decided on the selection of the studies. We followed standard Cochrane methods.

MAIN RESULTS

We identified no eligible studies for this review, either completed or ongoing.

AUTHORS' CONCLUSIONS

We found no studies, either completed or ongoing, that assessed the effects of indomethacin in controlling intracranial hypertension secondary to severe traumatic brain injury. Thus, we cannot draw any conclusions about the effects of indomethacin on intracranial pressure, mortality rates, quality of life, disability or adverse effects. This absence of evidence should not be interpreted as evidence of no effect for indomethacin in controlling intracranial hypertension secondary to severe traumatic brain injury. It means that we have not identified eligible research for this review.

Management Strategies for Intracranial Pressure Crises in Subarachnoid Hemorrhage

Objectives: Standard management strategies for lowering intracranial pressure (ICP) in traumatic brain injury has been well-studied, but the use of lesser known interventions for ICP in subarachnoid hemorrhage (SAH) remains elusive. Searches were performed in PubMed and EBSCO Host to identify best available evidence for evaluation and management of medically refractory ICP in SAH. The role of standard management strategies such as head elevation, hyperventilation, mannitol and hypertonic saline as well as lesser known management such as sodium bicarbonate, indomethacin, tromethamine, decompressive craniectomy, decompressive laparotomy, hypothermia, and barbiturate coma are reviewed. We also included dose concentrations, dose frequency, infusion volume, and infusion rate for these lesser known strategies. Nonetheless, there is still a gap in the evidence to recommend optimal dosing, timing and its role in the improvement of outcomes but early diagnosis and appropriate management reduce adverse outcomes.

Hyperventilation Therapy for Control of Posttraumatic Intracranial Hypertension

During traumatic brain injury, intracranial hypertension (ICH) can become a life-threatening condition if it is not managed quickly and adequately. Physicians use therapeutic hyperventilation to reduce elevated intracranial pressure (ICP) by manipulating autoregulatory functions connected to cerebrovascular CO₂ reactivity. Inducing hypocapnia via hyperventilation reduces the partial pressure of arterial carbon dioxide (PaCO₂), which incites vasoconstriction in the cerebral resistance arterioles. This constriction decrease cerebral blood flow, which reduces cerebral blood volume and, ultimately, decreases the patient’s ICP. The effects of therapeutic hyperventilation (HV) are transient, but the risks accompanying these changes in cerebral and systemic physiology must be carefully considered before the treatment can be deemed advisable. The most prominent criticism of this approach is the cited possibility of developing cerebral ischemia and tissue hypoxia. While it is true that certain measures, such as cerebral oxygenation monitoring, are needed to mitigate these dangerous conditions, using available evidence of potential poor outcomes associated with HV as justification to dismiss the implementation of therapeutic HV is debatable and remains a controversial subject among physicians. This review highlights various issues surrounding the use of HV as a means of controlling posttraumatic ICH, including indications for treatment, potential risks, and benefits, and a discussion of what techniques can be implemented to avoid adverse complications.

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.

Capillary transit time heterogeneity and flow-metabolism coupling after traumatic brain injury

Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12 hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of 'classic' ischemia. We discuss diagnostic and therapeutic consequences of these predictions.

Effects of indomethacin test on intracranial pressure and cerebral hemodynamics in patients with refractory intracranial hypertension: a feasibility study

BACKGROUND

Intracranial hypertension is the final pathway of many neurocritical entities, such as spontaneous intracerebral hemorrhage (sICH) and severe traumatic brain injury (sTBI).

OBJECTIVE

This study aimed to (1) determine alterations in intracranial pressure (ICP) and cerebral hemodynamics after an indomethacin (INDO) infusion test and the related association with survival in patients with refractory intracranial hypertension (RICH) secondary to sICH or sTBI and (2) assess the safety profile after INDO.

METHODS

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by a 2-hour continuous infusion (0.5 mg/kg/h) in RICH patients with ICP greater than 20 mm Hg who did not respond to first-line therapies. Changes in ICP, cerebral perfusion pressure (CPP), and cerebrovascular variables (assessed by transcranial Doppler and jugular bulb saturation) were observed. Clinical outcome was assessed at 1 and 6 months according to the Glasgow Outcome Scale and correlated with INDO infusion test response. Analysis of INDO safety profile was conducted.

RESULTS

Thirteen sICH and 10 sTBI patients were studied. The median GCS score at admission was 6. Within 30 minutes of INDO infusion, ICP decreased (42.0 ± 13.5 vs 27.70 ± 12.7 mm Hg; Δ%: -48.4%; P < .001), and both CPP (57.7 ± 4.8 vs 71.9 ± 7.0 mm Hg; Δ%: +26.0%; P < .001) and middle cerebral artery velocity (35.2 ± 5.6 vs 42.0 ± 5.1 cm·s(-1); Δ%: +26.1%; P < .001) increased. The CPP response to a 2-hour INDO infusion test was correlated (R2 = 0.72, P < .001) with survival. No adverse events were observed after INDO.

CONCLUSION

Our findings support the effectiveness and feasibility of an INDO test in decreasing ICP and improving cerebral hemodynamics in surviving RICH patients. Future studies to evaluate different doses, lengths of infusion, and longer term effects are needed.

Does hyperventilation improve operating condition during supratentorial craniotomy? A multicenter randomized crossover trial

BACKGROUND

Hyperventilation has been an integral, but poorly validated part of neuroanesthetic practice. We conducted a two-period, crossover, randomized trial to evaluate surgeon-assessed brain bulk and measured intracranial pressure (ICP) in patients undergoing craniotomy for removal of supratentorial brain tumors during moderate hypocapnia or normocapnia.

METHODS

Two-hundred and seventy-five adult patients with supratentorial brain tumors were randomized to one of two treatment sequences: hyperventilation (arterial carbon dioxide tension, PaCO2 = 25 +/- 2 mm Hg) followed by normoventilation (PaCO2 = 37 +/- 2 mm Hg) or normoventilation followed by hyperventilation. Ventilation and end-tidal CO2 tension were kept constant for 20 min. Patients were also randomly assigned to receive a propofol infusion or isoflurane anesthesia. At the end of each study period, subdural ICP was measured and the neurosurgeon, blinded to the treatment group, was asked to rate the brain bulk using a four-point scale.

RESULTS

Using a generalized estimation equation model, we found that hyperventilation decreased the risk of increased brain bulk by 45%, P = 0.004, 95% confidence intervals 22% to 61%, and the number needed to treat was 8. The mean (+/-SD) ICP during hyperventilation, 12.3 +/- 8.1 mm Hg, was lower than that during normoventilation, 16.2 +/- 9.6 mm Hg, P < 0.001. Anesthetic regimen did not affect brain bulk assessment or ICP.

CONCLUSIONS

In patients with supratentorial brain tumors, intraoperative hyperventilation improves surgeon-assessed brain bulk which was associated with a decrease in ICP.

Indomethacin and cerebral autoregulation in severe head injured patients: a transcranial Doppler study

OBJECTIVE

To assess the effect of indomethacin on cerebral autoregulation, systemic and cerebral haemodynamics, in severe head trauma patients.

DESIGN

Prospective, controlled clinical trial, with repeated measurements.

SETTINGS

A 12-bed adult general intensive care unit in a third level referral university hospital.

PATIENTS

16 severely head injured patients, 14 males, age range 17-60.

INTERVENTIONS

Indomethacin was administrated as a load plus continuous infusion. Indomethacin reactivity was assessed as the estimated cerebral blood flow change elicited by the load. Dynamic and static cerebral autoregulation tests were performed before indomethacin administration, and during its infusion.

MEASUREMENTS AND MAIN RESULTS

Systemic and cerebral haemodynamic changes were assessed through continuous monitoring of mean arterial pressure, transcranial Doppler cerebral blood flow velocity, intracranial pressure, cerebral perfusion pressure, and jugular venous oxygen saturation. Indomethacin loading dose was immediately followed by a cerebral blood flow median decrease of 36 or 29% (p = ns) evaluated by two different methods, by an ICP decrease and by an AVDO(2) increase from 3.52 to 6.15 mL/dL (p = 0.002). Dynamic autoregulation increased from a median of 28 to 57% (p<0.05) during indomethacin infusion; static autoregulation also increased, from a median of 72 to 89% (p = ns).

CONCLUSIONS

Indomethacin decreased intracranial pressure and cerebral blood flow, and increased cerebral perfusion pressure, while maintaining tissue properties of further extracting O(2). The increase in both autoregulatory values reveals an enhancement of cerebral microvasculature reactivity under indomethacin, during hypertensive and--especially--during hypotensive situations.

Therapy of intracranial hypertension in patients with fulminant hepatic failure

Severe intracranial hypertension (IH) in the setting of fulminant hepatic failure (FHF) carries a high mortality and is a challenging disease for the critical care provider. Despite considerable improvements in the understanding of the pathophysiology of cerebral edema during liver failure, therapeutic maneuvers that are currently available to treat this disease are limited. Orthotopic liver transplantation is currently the only definitive therapeutic strategy that improves outcomes in patients with FHF. However, many patients die prior to the availability of donor organs, often because of cerebral herniation. Currently, two important theories prevail in the understanding of the pathophysiology of IH during FHF. Ammonia and glutamine causes cytotoxic cerebral injury while cerebral vasodilation caused by loss of autoregulation increases intracranial pressure (ICP) and predisposes to herniation. Although ammonia-reducing strategies are limited in humans, modulation of cerebral blood flow seems promising, at least during the early stages of hepatic encephalopathy. ICP monitoring, transcranial Doppler, and jugular venous oximetry offer valuable information regarding intracranial dynamics. Induced hypothermia, hypertonic saline, propofol sedation, and indomethacin are some of the newer therapies that have been shown to improve survival in patients with severe IH. In this article, we review the pathophysiology of IH in patients with FHF and outline various therapeutic strategies currently available in managing these patients in the critical care setting.

Cerebral metabolic response to low blood flow: possible role of cytochrome oxidase inhibition

The reactions of cerebral metabolism to imposed changes of cerebral blood flow (CBF) are poorly understood. A common explanation of the mismatched CBF and oxygen consumption (CMR(O(2))) during neuronal excitation holds that blood flow rises more than oxygen consumption to compensate for an absent oxygen reserve in brain mitochondria. The claim conversely implies that oxygen consumption must decline when blood flow declines. As the prevailing rate of reaction of oxygen with cytochrome c oxidase is linked to the tension of oxygen, the claim fails to explain how oxygen consumption is maintained during moderate reductions of CBF imposed by hyperventilation (hypocapnia) or cyclooxygenase (COX) inhibition. To resolve this contradiction, we extended the previously published oxygen delivery model with a term allowing for the adjustment of the affinity of cytochrome c oxidase to a prevailing oxygen tension. The extended model predicted constant oxygen consumption at moderately reduced blood flow. We determined the change of affinity of cytochrome c oxidase in the extended model by measuring CBF in seven, and CMR(O(2)) in five, young healthy volunteers before and during COX inhibition with indomethacin. The average CBF declined 35%, while neither regional nor average CMR(O(2)) changed significantly. The adjustment of cytochrome c oxidase affinity to the declining oxygen delivery could be ascribed to a hypothetical factor with several properties in common with nitric oxide.

Hyperventilation in head injury: a review

The aim of this review was to consider the effects of induced hypocapnia both on systemic physiology and on the physiology of the intracranial system. Hyperventilation lowers intracranial pressure (ICP) by the induction of cerebral vasoconstriction with a subsequent decrease in cerebral blood volume. The downside of hyperventilation, however, is that cerebral vasoconstriction may decrease cerebral blood flow to ischemic levels. Considering the risk-benefit relation, it would appear to be clear that hyperventilation should only be considered in patients with raised ICP, in a tailored way and under specific monitoring. Controversy exists, for instance, on specific indications, timing, depth of hypocapnia, and duration. This review has specific reference to traumatic brain injury, and is based on an extensive evaluation of the literature and on expert opinion.

Treatment of elevated intracranial pressure with indomethacin: friend or foe?

Indomethacin has been suggested as a therapeutic tool to manage elevated intracranial pressure in patients with severe head injury and patients undergoing craniotomy for brain tumors. Indomethacin is a non-selective cyclooxygenase inhibitor. Compared to other cyclooxygenase inhibitors indomethacin has unique effects on cerebral blood flow. Administration of indomethacin causes cerebral vasoconstriction and decreases cerebral blood flow, which elicits a decrease in intracranial pressure. The mechanism of indomethacin-induced cerebral vasoconstriction is not completely understood and controversies exist whether indomethacin causes cerebral ischemia. The primary aims of this article were to review the existing knowledge of indomethacin's influence upon cerebral hemodynamics and elevated ICP in patients with brain pathology. Furthermore, indomethacin's mechanism of action and whether it causes cerebral ischemia are discussed.

The effects of indomethacin on intracranial pressure and cerebral haemodynamics in patients undergoing craniotomy: A randomised prospective study

We compared the effects of indomethacin (bolus of 0.2 mg.kg-1 followed by an infusion of 0.2 mg.kg-1.h-1) and placebo on intracranial pressure and cerebral haemodynamics in 30 patients undergoing craniotomy for supratentorial brain tumours under propofol and fentanyl anaesthesia. Indomethacin was given before induction of anaesthesia and the infusion was terminated after opening of the dura. Subdural intracranial pressure was measured through the first burr hole and before opening the dura. Cerebral blood flow velocity, cerebral perfusion pressure, jugular bulb oxygen saturation, arterio-venous oxygen difference and carbon dioxide reactivity were measured; dural tension and the degree of brain swelling were estimated. Before induction of anaesthesia, indomethacin administration was associated with a significant decrease in cerebral blood flow velocity compared with placebo. After induction of anaesthesia, cerebral blood flow velocity and mean arterial blood pressure decreased significantly in both groups. Indomethacin was not associated with a decrease in intracranial pressure. There were no differences in cerebral perfusion pressure, dural tension or degree of brain swelling between the two groups. Carbon dioxide reactivity measured after induction of anaesthesia was significantly lower in the indomethacin group (p < 0.05). After removal of the bone flap, no significant difference in carbon dioxide reactivity was observed. We suggest that these findings are explained by propofol-induced cerebral vasoconstriction.

Intravenous administration of flurbiprofen does not affect cerebral blood flow velocity and cerebral oxygenation under isoflurane and propofol anesthesia

Flurbiprofen, a nonsteroidal antiinflammatory drug (NSAID), has been used to treat rheumatic and osteoarthritic pain and to reduce postoperative pain. Although other NSAIDs, such as indomethacin, reduce cerebral blood flow (CBF), the effect of flurbiprofen on CBF is unknown. In the present study, we investigated the effects of flurbiprofen on cerebral blood flow velocity (CBFV) and cerebral oxygenation under isoflurane or propofol anesthesia. Forty-eight patients undergoing orthopedic or abdominal surgery were enrolled. Patients were randomly allocated to receive either propofol (target control infusion: target site effect concentration 3 microg/mL) or isoflurane (1 MAC) for maintenance of anesthesia. In each group (n = 12), 1 mg/kg of flurbiprofen (PROP-F and ISO-F groups) or 0.1 mL/kg saline (PROP-S and ISO-S groups) was administered i.v. for 5 min. During and after the administration of flurbiprofen or saline, cerebral oxygenation variables (tissue oxygen index [TOI], total hemoglobin change [Delta cHb], oxygenated hemoglobin changes [Delta O(2)Hb], and deoxygenated hemoglobin changes [Delta HHb]), and middle cerebral artery flow velocity (Vmca) were measured using a cerebral oximeter (NIRO 300) and transcranial Doppler, respectively, from 5 min before study drug administration to 60 min post-administration. Before the administration of flurbiprofen, control values of TOI in the ISO-S and ISO-F groups were significantly higher than those in the PROP-S and PROP-F groups, respectively (ISO-S versus PROP-S, 67% +/- 4% versus 60% +/- 7%; IOS-F versus PROP-F, 69% +/- 4% versus 63% +/- 8%; P < 0.05). However, values of TOI, Delta cHb, Delta O(2)Hb, Delta HHb, and Vmca did not change significantly during and after the administration of flurbiprofen under propofol or isoflurane anesthesia, and these values were similar to those during and after the administration of saline in the same anesthesia group. These data indicate that flurbiprofen does not affect CBFV and cerebral oxygenation under propofol or isoflurane anesthesia.

IMPLICATIONS

Indomethacin, a nonsteroidal antiinflammatory drug (NSAID), has been demonstrated to reduce cerebral blood flow (CBF). The CBF effects of flurbiprofen, another NSAID, are unknown. We investigated cerebral blood flow velocity (CBFV) and cerebral oxygenation during and after the administration of flurbiprofen under isoflurane and propofol anesthesia. We found that flurbiprofen had no effect on CBFV and cerebral oxygenation.

Cyclooxygenase inhibition as a strategy to ameliorate brain injury

Cyclooxygenase (COX) is the obligate, rate-limiting enzyme for the conversion of arachidonic acid into prostaglandins. Two COX enzymes have been identified: a constitutively expressed COX-1 and an inducible, highly regulated COX-2. Widely used to treat chronic inflammatory disorders, COX inhibitors have shown promise in attenuating inflammation associated with brain injury. However, the use of COX inhibition in the treatment of brain injury has met with mixed success. This review summarizes our current understanding of COX expression in the central nervous system and the effects of COX inhibitors on brain injury. Three major targets for COX inhibition in the treatment brain injury have been identified. These are the cerebrovasculature, COX-2 expression by vulnerable neurons, and the neuroinflammatory response. Evidence suggests that given the right treatment paradigm, COX inhibition can influence each of these three targets. Drug interactions and general considerations for administrative paradigms are also discussed. Although therapies targeted to specific prostaglandin species, such as PGE2, might prove more ameliorative for brain injury, at the present time non-specific COX inhibitors and COX-2 specific inhibitors are readily available to researchers and clinicians. We believe that COX inhibition will be a useful, ameliorative adjunct in the treatment of most forms of brain injury.

Prolonged cyclooxygenase-2 induction in neurons and glia following traumatic brain injury in the rat

Cyclooxygenase-2 (COX2) is a primary inflammatory mediator that converts arachidonic acid into precursors of vasoactive prostaglandins, producing reactive oxygen species in the process. Under normal conditions COX2 is not detectable, except at low abundance in the brain. This study demonstrates a distinctive pattern of COX2 increases in the brain over time following traumatic brain injury (TBI). Quantitative lysate ribonuclease protection assays indicate acute and sustained increases in COX2 mRNA in two rat models of TBI. In the lateral fluid percussion model, COX2 mRNA is significantly elevated (>twofold, p < 0.05, Dunnett) at 1 day postinjury in the injured cortex and bilaterally in the hippocampus, compared to sham-injured controls. In the lateral cortical impact model (LCI), COX2 mRNA peaks around 6 h postinjury in the ipsilateral cerebral cortex (fivefold induction, p < 0.05, Dunnett) and in the ipsilateral and contralateral hippocampus (two- and six-fold induction, respectively, p < 0.05, Dunnett). Increases are sustained out to 3 days postinjury in the injured cortex in both models. Further analyses use the LCI model to evaluate COX2 induction. Immunoblot analyses confirm increased levels of COX2 protein in the cortex and hippocampus. Profound increases in COX2 protein are observed in the cortex at 1-3 days, that return to sham levels by 7 days postinjury (p < 0.05, Dunnett). The cellular pattern of COX2 induction following TBI has been characterized using immunohistochemistry. COX2-immunoreactivity (-ir) rises acutely (cell numbers and intensity) and remains elevated for several days following TBI. Increases in COX2-ir colocalize with neurons (MAP2-ir) and glia (GFAP-ir). Increases in COX2-ir are observed in cerebral cortex and hippocampus, ipsilateral and contralateral to injury as early as 2 h postinjury. Neurons in the ipsilateral parietal, perirhinal and piriform cortex become intensely COX2-ir from 2 h to at least 3 days postinjury. In agreement with the mRNA and immunoblot results, COX2-ir appears greatest in the contralateral hippocampus. Hippocampal COX2-ir progresses from the pyramidal cell layer of the CA1 and CA2 region at 2 h, to the CA3 pyramidal cells and dentate polymorphic and granule cell layers by 24 h postinjury. These increases are distinct from those observed following inflammatory challenge, and correspond to brain areas previously identified with the neurological and cognitive deficits associated with TBI. While COX2 induction following TBI may result in selective beneficial responses, chronic COX2 production may contribute to free radical mediated cellular damage, vascular dysfunction, and alterations in cellular metabolism. These may cause secondary injuries to the brain that promote neuropathology and worsen behavioral outcome.

The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Hyperventilation

Chronic prophylactic hyperventilation therapy should be avoided during the first 5 days after severe TBI and particularly during the first 24 h. CBF measurements in patients with severe TBI demonstrate that blood flow early after injury is low and strongly suggest that in the first few hours after injury the absolute values approach those consistent with ischemia. These findings are corroborated by AVdO2 and SjO2 and brain tissue O2 measurements. Hyperventilation will reduce CBF values even further, but will not consistently cause a reduction of ICP and may cause loss of autoregulation. The cerebral vascular response to hypocapnia is reduced in those with the most severe injuries (subdural hematomas and diffuse contusions), and there is substantial local variability in perfusion. While the CBF level at which irreversible ischemia occurs has not been clearly established, ischemic cell change has been demonstrated in 90% of those who die following TBI, and there is PET evidence that such damage is likely to occur when CBF drops below 15-20 cc/100 g/min. A prospective randomized clinical trial has determined that outcomes are worse when TBI patients are treated with chronic prophylactic hyperventilation therapy. Within the standard, guideline, and options, specific paCO2 thresholds have been described that are different for each of the three parameters. These individual thresholds were selected based on the preponderance of literature supporting those thresholds in the contexts of the statements which included them. With the exception of the threshold included for the standard in this guideline, it is emphasized that the paCO2 threshold is not as important as the general concept of hyperventilation. The preponderance of the physiologic literature concludes that hyperventilation during the first few days following severe traumatic brain injury, whatever the threshold, is potentially deleterious in that it can promote cerebral ischemia.