Doxycycline reduces early neurologic impairment after cerebral arterial air embolism in the rabbit

Deep hypothermic circulatory arrest in cyanotic piglets is associated with increased neuronal necrosis

BACKGROUND

The contribution of neonatal cyanosis, inherent to cyanotic congenital heart disease, to the magnitude of neurologic injury during deep hypothermic circulatory arrest has not been fully delineated. This study investigates the impact of cyanosis and deep hypothermic circulatory arrest on brain injury.

METHODS

Neonatal piglets were randomised to placement of a pulmonary artery to left atrium shunt to create cyanosis or sham thoracotomy. At day 7, animals were randomised to undergo deep hypothermic circulatory arrest or sham. Arterial oxygen tension and haematocrit were obtained. Neurobehavioural performance was serially assessed. The animals were sacrificed on day 14. Brain tissue was assessed for neuronal necrosis using a 5-point histopathologic score.

RESULTS

Four experimental groups were analysed (sham, n = 10; sham + deep hypothermic circulatory arrest, n = 8; shunt, n = 9; shunt + deep hypothermic circulatory arrest, n = 7). Cyanotic piglets had significantly higher haematocrit and lower partial pressure of oxygen at day 14 than non-cyanotic piglets. There were no statistically significant differences in neurobehavioural scores at day 1. However, shunt + deep hypothermic circulatory arrest piglets had evidence of greater neuronal injury than sham animals (median (range): 2 (0-4) versus 0 (0-0), p = 0.02).

DISCUSSION

Cyanotic piglets undergoing deep hypothermic circulatory arrest had increased neuronal injury compared to sham animals. Significant injury was not seen for either cyanosis or deep hypothermic circulatory arrest alone relative to shams. These findings suggest an interaction between cyanosis and deep hypothermic circulatory arrest and may partially explain the suboptimal neurologic outcomes seen in children with cyanotic heart disease who undergo deep hypothermic circulatory arrest.

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Doxycycline restrains glia and confers neuroprotection in a 6-OHDA Parkinson model

Neuron-glia interactions play a key role in maintaining and regulating the central nervous system. Glial cells are implicated in the function of dopamine neurons and regulate their survival and resistance to injury. Parkinson's disease is characterized by the loss of dopamine neurons in the substantia nigra pars compacta, decreased striatal dopamine levels and consequent onset of extrapyramidal motor dysfunction. Parkinson's disease is a common chronic, neurodegenerative disorder with no effective protective treatment. In the 6-OHDA mouse model of Parkinson's disease, doxycycline administered at a dose that both induces/represses conditional transgene expression in the tetracycline system, mitigates the loss of dopaminergic neurons in the substantia nigra compacta and nerve terminals in the striatum. This protective effect was associated with: (1) a reduction of microglia in normal mice as a result of doxycycline administration per se; (2) a decrease in the astrocyte and microglia response to the neurotoxin 6-OHDA in the globus pallidus and substantia nigra compacta, and (3) the astrocyte reaction in the striatum. Our results suggest that doxycycline blocks 6-OHDA neurotoxicity in vivo by inhibiting microglial and astrocyte expression. This action of doxycycline in nigrostriatal dopaminergic neuron protection is consistent with a role of glial cells in Parkinson's disease neurodegeneration. The neuroprotective effect of doxycycline may be useful in preventing or slowing the progression of Parkinson's disease and other neurodegenerative diseases linked to glia function.

Animal models of cerebral arterial gas embolism

Cerebral arterial gas embolism is a dreaded complication of diving and invasive medical procedures. Many different animal models have been used in research on cerebral arterial gas embolism. This review provides an overview of the most important characteristics of these animal models. The properties discussed are species, cerebrovascular anatomy, method of air embolization, amount of air, bubble size, outcome parameters, anesthesia, blood glucose, body temperature and blood pressure.

Multimodal brain monitoring reduces major neurologic complications in cardiac surgery

OBJECTIVE

Although adverse neurologic outcomes are common complications of cardiac surgery, intraoperative brain monitoring has not received adequate attention. The aim of the present study was to evaluate the effectiveness of multimodal brain monitoring in the prevention of major brain injury and reducing the duration of mechanical ventilation, intensive care unit, and postoperative hospital stays after cardiac surgery.

DESIGN

A retrospective, observational, controlled study.

SETTING

A single-center regional hospital.

PARTICIPANTS

One thousand seven hundred twenty-one patients who had undergone cardiac surgery with cardiopulmonary bypass from July 2007 to July 2010. One hundred sixty-six patients with multimodal brain monitoring and a control group without brain monitoring (N = 1,555) were compared retrospectively.

INTERVENTIONS

Multimodal brain monitoring was performed for 166 patients, consisting of intraoperative recordings of somatosensory-evoked potentials, electroencephalography, and transcranial Doppler.

MEASUREMENTS AND MAIN RESULTS

The incidence of major neurologic complications and the duration of mechanical ventilation, intensive care unit, and postoperative hospital stays were considered. Patients with brain monitoring had a significantly lower incidence of perioperative major neurologic complications (0%) than those without monitoring (4.06%, p = 0.01) and required significantly shorter periods of mechanical ventilation (p = 0.001) and intensive care unit stays (p = 0.01) than controls. The length of postoperative hospital stays did not differ significantly between the 2 groups (p = 0.57).

CONCLUSIONS

This preliminary study suggests that multimodal brain monitoring can reduce the incidence of neurologic complications as well as hospital costs associated with post-cardiac surgery patient care. Furthermore, intraoperative brain monitoring provides useful information about brain functioning, blood flow velocity, and metabolism, which may guide the anesthesiologist during surgery.

Neuroprotection (including hypothermia)

There have been over 2000 publications in the last year addressing the topic of neuroprotection. Novel and emerging therapeutic targets that have been explored include cerebral inflammation, hypothermia, neural transplantation and repair and gene therapy. Unfortunately, with few exceptions, the successes of experimental neuroprotection have not been translated into clinical practice. The possible reasons for the discrepancy between experimental success and clinical benefit are explored.

Adverse cerebrovascular effects of intraarterial CO2 injections: development of an in vitro/in vivo model for assessment of gas-based toxicity

PURPOSE

To assess whether and how CO(2) can cause ischemic injury in the central nervous system after internal carotid artery injection.

MATERIALS AND METHODS

In 14 adult pigs, both internal carotid arteries were catheterized via a transfemoral approach. One carotid artery served as control and the other was injected via a prototype gas injector with defined volumes and pressures of gas. Effects were assessed by clinical observation, repeated magnetic resonance (MR) imaging, histopathology, and vital staining. An in vitro flow circuit was used to model injection parameters.

RESULTS

Single injections of CO(2) did not produce persistent clinical symptomatology. In vitro conditions were created in which bubbles adhered to the tubing of the circuit, creating functional stenoses, or coalesced into larger bubbles that became trapped, thereby reducing flow and augmenting potential embologenic effects of subsequent injections. With in vitro-derived dual injection parameters, seven pigs underwent two sequential injections of CO(2). All did well after the first injections, but all had adverse effects after the second injections, including involuntary tonic-clonic muscular movements, cardiopulmonary arrest, recurrent intractable seizure activity during recovery, hemorrhagic venous infarcts on gross and histopathologic examination, and blood-brain barrier breakdown on vital staining. MR imaging was not sensitive even after symptomatic intraarterial air injection.

CONCLUSIONS

Absence of adverse effects after single bolus injections in pigs does not prove the safety of intracranial CO(2) injections in human patients. Considering the possible deleterious effects of repeat intravascular injections in the highly sensitive system of the brain, it may be prudent for clinical application at other approved sites to let time pass between boluses sufficient to permit absorption of wall-adherent and coalescent bubbles that could cause gas embolic events.

Regional low-flow perfusion improves neurologic outcome compared with deep hypothermic circulatory arrest in neonatal piglets

BACKGROUND

Regional low-flow perfusion is an alternative to deep hypothermic circulatory arrest, but whether regional low-flow perfusion improves neurologic outcome after deep hypothermic circulatory arrest in neonates remains unknown. We tested neurologic recovery after regional low-flow perfusion compared with deep hypothermic circulatory arrest in a neonatal piglet model.

METHODS

Sixteen neonatal piglets underwent cardiopulmonary bypass, were randomized to 90 minutes of deep hypothermic circulatory arrest or regional low-flow perfusion (10 mL.kg(-1).min(-1)) at 18 degrees C, and survived for 1 week. Standardized neurobehavioral scores were obtained on postoperative days 1, 3, and 7 (0 = no deficit to 90 = brain death). Histopathologic scores were determined on the basis of the percentage of injured and apoptotic neurons in the neocortex and hippocampus by hematoxylin and eosin and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (0 = no injury to 4 = diffuse injury). Differences between groups were tested by using the Wilcoxon rank sum test, and results are listed as medians within a range.

RESULTS

There were no significant differences between groups during cardiopulmonary bypass. Postoperative neurobehavioral scores were abnormal in 25% (2/8) of the regional low-flow perfusion animals versus 88% (7/8) of controls. Regional low-flow perfusion animals had significantly less neurologic injury compared with controls on postoperative day 1 (0.00 [range, 0-5] vs 12.5 [range, 0-52]; P <.008). There was a trend for less severe injury in the regional low-flow perfusion group (2.0 [range, 1-4] vs 0.0 [range, 0-50]; P =.08) on hematoxylin and eosin. The degree of apoptosis was significantly less in the regional low-flow perfusion group (0.0 [range, 0-1] vs 2.5 [range, 0-4]; P =.03).

CONCLUSIONS

Regional low-flow perfusion decreases neuronal injury and improves early postoperative neurologic function after deep hypothermic circulatory arrest in neonatal piglets.

Brain injury after adult cardiac surgery

Despite remarkable progress in surgical, cardiopulmonary bypass and anaesthetic techniques during the last three decades, brain damage remains an important complication of adult cardiac surgery. Effective brain protection strategies are already implemented today, but ongoing research is needed to meet the challenges faced in operating on increasingly old and disabled patients. The incidence of brain injury may be reduced by modifying the surgical procedure according to carotid duplex scanning and epiaortic echocardiography, by using techniques to reduce microembolization during cardiopulmonary bypass and by optimizing patient temperature during and after surgery. Increased knowledge will aid in choosing the best procedure or combination of procedures in each case to ensure that risks do not outweigh benefits.

Effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant defense system, paraoxonase (PON1) activities, and homocysteine levels in an animal model of spinal cord injury

STUDY DESIGN

Investigation of the effects of prostaglandin E1, melatonin, and oxytetracycline on lipid peroxidation, antioxidant and paraoxonase activities, and homocysteine levels in an experimental model of spinal cord injury.

OBJECTIVES

To determine the antioxidant efficacy of prostaglandin E1, melatonin, and oxytetracycline and whether paraoxonase and homocysteine can be used as monitoring parameters in the acute oxidative stress of spinal cord injury.

SUMMARY OF BACKGROUND DATA

Melatonin has been found useful in spinal cord injury in previous studies. No study exists investigating the effects of melatonin, prostaglandin E1, and oxytetracycline as well as the response type of paraoxonase enzyme and homocysteine levels in the acute oxidative stress of spinal cord injury.

METHODS

Sixty-three male albino Wistar rats were anesthetized with 400 mg/kg chloral hydrate and divided into 5 groups. The G1 (n = 7) control group provided the baseline levels. G2-G5 underwent T3-T6 total laminectomies and spinal cord injuries by clip compression at the T4-T5 levels. Medications were applied to G3-G5 right after clip compression. Hence, G2 constituted laminectomy + injury, G3 laminectomy + injury + prostaglandin E1; G4 laminectomy + injury + melatonin, and G5 laminectomy + injury + oxytetracycline groups. Animals were decapitated either the first or fourth hour after injury. Spinal cord tissue and blood malonyldialdehyde and plasma homocysteine levels, plasma glutathione peroxidase, superoxide dismutase, paraoxonase activities were assayed. The SPSS 9.0 program was used for statistical analysis and graphics. Intergroup comparisons were made by Bonferroni corrected Mann Whitney U test (P < 0.025) and intragroups comparisons by Wilcoxon Rank test (P < 0.03).

RESULTS

In injury groups, plasma homocysteine levels decreased and paraoxonase activities increased as erythrocyte superoxide dismutase levels and plasma glutathione peroxidase activities decreased in parallel to increases of tissue and blood malonyldialdehyde levels. These alterations were relatively suppressed by prostaglandin E1, melatonin, and oxytetracycline administrations in varying degrees. Melatonin was the most powerful agent, particularly at the fourth hour. Oxytetracycline was also effective, both at the first and fourth hour. Prostaglandin E1 was effective in comparison to injury group, but not as much as melatonin and oxytetracycline.

CONCLUSIONS

Melatonin and oxytetracycline are effective in preventing lipid peroxidation in spinal cord injury. Paraoxonase and homocysteine can be used in monitoring the antioxidant defense system as well as superoxide dismutase and plasma glutathione peroxidase, both in injury and medicated groups.

Regional patterns of neuronal death after deep hypothermic circulatory arrest in newborn pigs

OBJECTIVES

Deep hypothermic circulatory arrest (DHCA) widely used during neonatal heart surgery, carries a risk of brain damage. In adult normothermic ischemia, brain cells in certain regions die, some by necrosis and others by apoptosis (programmed cell death). This study characterized regional brain cell death after DHCA in newborn pigs.

METHODS

Eighteen piglets underwent 90 minutes of DHCA and survived 6 hours, 2 days, or 1 week. Six piglets underwent surgery alone or deep hypothermic cardiopulmonary bypass and survived 2 days. Three piglets received no intervention (control). Brain injury was assessed by neurologic and histologic examination and correlated with perioperative factors. Apoptosis and necrosis were identified by light microscopic analysis of cell structure and in situ DNA fragmentation (TUNEL).

RESULTS

All groups subjected to DHCA had brain injury by neurologic and histologic examination, whereas the other groups did not. DHCA damaged neurons in the neocortex and hippocampus and occasionally in the striatum and cerebellum. Damaged neurons in the neocortex were mainly apoptotic and in the hippocampus, a mixture of necrotic and apoptotic neurons. Apoptosis and necrosis were apparent in all DHCA groups even though neurologic deficits improved over the week's survival. Neocortical and hippocampal damage correlated with blood glucose, hematocrit, and arterial PO(2) during and after cardiopulmonary bypass.

CONCLUSIONS

In neonates, neocortical and hippocampal neurons are selectively vulnerable to death after DHCA. Both apoptosis and necrosis contribute to neuronal death, beginning early in reperfusion and continuing for days. These data suggest the need for several neuroprotective strategies tailored to the region and death process, initiated during the operation and continued after the operation.

Cardiopulmonary bypass time does not affect cerebral blood flow

BACKGROUND

A time-dependent decline in cerebral blood flow (CBF) has been reported in cardiac surgical patients despite stable pump flows and arterial carbon dioxide tension. Other studies have failed to support these hypothermic cardiopulmonary bypass (CPB) results, showing preservation of CBF during CPB. The purpose of the study was to define the influence of mildly hypothermic CPB duration on CBF.

METHODS

Cerebral blood flow was measured using xenon-133 washout and alpha-stat blood gas management during nonpulsatile CPB. Cerebral blood flow measurements were made after the initiation of CPB and near the end of bypass during pump flows of 2.4 L.min-1.m-2.

RESULTS

Fifty-two coronary artery bypass patients were studied. The average time between CBF measurements was 54 +/- 20 minutes (mean +/- standard deviation), with a range of 10 to 100 minutes. Temperature and arterial carbon dioxide tension were controlled: after the initiation of CPB, temperature was 35.5 degrees +/- 0.4 degree C and carbon dioxide tension was 37 +/- 2.8 mm Hg; whereas near the end of bypass temperature was 35.6 degrees +/- 0.5 degree C and carbon dioxide tension was 36 +/- 2.3 mm Hg. We found no correlation between CBF and time on CPB (p = 0.47; r = 0.101), in contrast to other studies suggesting that CPB duration may intrinsically affect CBF.

CONCLUSIONS

Our experimental results include the following: (1) during mildly hypothermic bypass, CBF does not decrease in relation to time and (2) cerebral flow-metabolism coupling is intact at 35 degrees C.