Blood Pressure and the Brain: How Low Can You Go?

There are occasionally intraoperative circumstances in which reduction of mean arterial pressure (MAP) to levels well below those that occur in nonanesthetized adults is necessary or unavoidable. In these situations, clinicians are inevitably concerned about the limits of the tolerance of the brain for hypotension. Reference to the phenomenon of cerebral blood flow autoregulation is frequently made in discussions of safe MAP limits.

Atorvastatin, but not pravastatin, inhibits cardiac Akt/mTOR signaling and disturbs mitochondrial ultrastructure in cardiac myocytes.

Statins, which reduce LDL-cholesterol by inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, are among the most widely prescribed drugs. Skeletal myopathy is a known statin-induced adverse effect associated with mitochondrial changes. We hypothesized that similar effects would occur in cardiac myocytes in a lipophilicity-dependent manner between 2 common statins: atorvastatin (lipophilic) and pravastatin (hydrophilic).

Baseline Cerebral Metabolic Rate Is a Critical Determinant of the Cerebral Vasodilating Potency of Volatile Anesthetic Agents.

A Comparison of the Direct Cerebral Vasodilating Potencies of Halothane and Isoflurane in the New Zealand White Rabbit. By Drummond JC, Todd MM, Scheller MS, and Shapiro HM. ANESTHESIOLOGY 1986; 65:462-7.

Effects of ovarian disaggregation on adult murine follicle yield and viability.

Follicles are isolated from ovaries for numerous reasons, including IVM, but adult murine yields are <2 folliclesmg. The aim of the present study was to optimise ovarian disaggregation and develop methods applicable to the rapid screening of follicle viability. Ovaries from adult mice (n=7) were halved and disaggregated mechanically, or by using collagenase IV (Col-IV; 590UmL) or animal origin-free collagenase IV (AOF) at 590 or 1180UmL.

The Inter-Mammary Sticky Roll: A Novel Technique for Securing a Doppler Ultrasonic Probe to the Precordium for Venous Air Embolism Detection.

Venous air embolism is a devastating and potentially life-threatening complication that can occur during neurosurgical procedures. We report the development and use of the "inter-mammary sticky roll," a technique to reliably secure a precordial Doppler ultrasonic probe to the chest wall during neurosurgical cases that require lateral decubitus positioning. We have found that this noninvasive technique is safe, and effectively facilitates a constant Doppler signal with no additional risk to the patient.

An Observational Study of Cerebral Blood Flow Velocity During Hypotensive Epidural Anesthesia.

Background: Hypotensive epidural anesthesia (HEA), as practiced at our institution, uses sympathetic blockade to achieve mean arterial blood pressure (MAP) of ≤50 mm Hg while administering epinephrine by infusion to support the circulation. HEA has not been associated with gross adverse effects on neurologic outcome or cognitive function in the postoperative period, suggesting adequate cerebral blood flow (CBF). However, the use of MAPs well below the commonly accepted lower limit of CBF autoregulation suggests that CBF should be significantly reduced below normal levels.

The Effect of Clevidipine on Cerebral Blood Flow Velocity and Carbon Dioxide Reactivity in Human Volunteers.

Background: Clevidipine is a short acting, esterase metabolized, calcium channel antagonist administered as a continuous infusion for control of hypertension. Its profile allows for rapid titration and may be uniquely suited to achieving tight hemodynamic targets in neurosurgical and neurocritical care patients. The present study was designed to investigate the effect of clevidipine infusion on cerebral blood flow and cerebral CO2 responsiveness as measured by cerebral blood flow velocity (CBFV) using transcranial Doppler.

Paraplegia after epidural-general anesthesia in a Morquio patient with moderate thoracic spinal stenosis.

Purpose: We describe an instance in which complete paraplegia was evident immediately postoperatively after apparently uneventful lumbar epidural-general anesthesia in a patient with Morquio Type A syndrome (Morquio A) with moderate thoracic spinal stenosis.

Clinical Features: A 16-yr-old male with Morquio A received lumbar epidural-general anesthesia for bilateral distal femoral osteotomies. Preoperative imaging had revealed a stable cervical spine and moderate thoracic spinal stenosis with a mild degree of spinal cord compression.

Direct pressure on a pseudomeningocele resulting in intraoperative cerebral ischemia.

Purpose: When positioning patients with meningocele and meningomyelocele, it is standard practice to avoid direct pressure on the lesions. That caution is intended to prevent injury to neural elements within the lesion and violation of the cerebrospinal fluid space. We herein report an additional hazard of direct intraoperative pressure on such lesions.

Long-term atorvastatin treatment leads to alterations in behavior, cognition, and hippocampal biochemistry.

Membrane/lipid rafts (MLR) are plasmalemmal microdomains that are essential for neuronal signaling and synaptic development/stabilization. Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in the biosynthesis of mevalonic, a precursor to cholesterol via the mevalonate pathway. Because there has been controversy over the effects of statins on neuronal and cognitive function, we investigated the impact of long-term atorvastatin treatment (5mg/kg/d for 7 months by oral gavage) on behavior, cognition, and brain biochemistry in mice.

Revisioning, reconnecting and revisiting: the psychosocial transition of returning home from hospital following a stroke.

Purpose: This study aimed to investigate and improve understanding of the experiences of patients and their carers during the first month at home following discharge from hospital, thereby enhancing appropriate care from a more informed perspective.

Method: In-depth interviews and self-report diaries were used to capture data from 12 patient/carer dyads. Four survivors with marked communication problems were included in this number, two requiring the use of pictures and diagrams to express their views.

An observational study of the influence of "white-coat hypertension" on day-of-surgery blood pressure determinations.

Background: Because decisions as to what range of intraoperative blood pressure (BP) is consistent with cerebral well-being are often made in reference to "baseline BP," we sought to determine whether day-of-surgery BPs accurately reflect baseline BP, as defined by ambulatory clinic BPs over the preceding 7 months.

Methods: Consecutive patients (n=101) who were severely hypertensive (Severe-HTN), systolic (S)>160 mm Hg, or diastolic (D)>100 at first operating room BP (1st OR-BP) were identified retrospectively. Two additional groups were formed from patients whose 1st OR-BP was moderately hypertensive (Mod-HTN, systolic BP=140 to 159 and/or diastolic BP=90 to 99; and normotensive, SBP=110 to 139 and DBP<89).