[The Effect of Emulsified Sevofluran on Muscular Relaxation through Selective Blockage of Peripheral Nerves].

OBJECTIVES: To identify the site that emulsified sevoflurane influences in the nerve system. METHODS: Thirty-six healthy New Zealand rabbits were randomly and equally divided into low concentration emulsified sevoflurane group [4 mL/(kg·h)], medium concentration [6 mL/(kg·h)]group, high concentration group[10 mL/(kg·h)]and intralipid control group. Emulsified sevoflurane was infused through arterial to selectively block peripheral nerves, neuro-muscular junctions and muscle fibers. The anterior tibial muscle resting tensions and muscle contraction forces were compared before and after the infusions. RESULTS: Significant differences of blood sevoflurane pressure between femoral veins and internal jugular veins appeared in rabbits in all the groups ( P<0.05). No significant changes in the resting tension of anterior tibia muscles were found in terms of single contractions and tetanic forces with the low and medium levels of infusion of sevoflurane compared to the base values. High level of infusion of sevoflurane resulted in decreased single contraction forces and tetanic forces of anterior tibia muscles ( P<0.05). CONCLUSIONS: A rabbit model with selective blockage of peripheral nerves was established. Peripheral nerves are not the primary site which low and medium levels of emulsified sevoflurane influence skeletal muscle relaxations.

[Emulsified Sevoflurane Selectively Blocking Spinal Cord and Brain in Rabbit Model].

OBJECTIVES: To establish the rabbits model of selectively anesthetized brain and spinal cord and to explore the skeletal muscle relaxation sites of sevoflurane. METHODS: Sixteen adult male New Zealand white rabbits were randomly assigned to the experiment. The upper torso systemic circulation and the lower torso bypass circulation were independently established by the ligation of thoracic aorta at T12-L1 level. Sevoflurane was administered to the upper or lower torso through lungs or oxygenator to selectively anesthetized brain or spinal cord (mainly lumbar and sacro-coccygeal region). Sevoflurane concentration from end-tidal (represented the brain) and oxygenator outlet (represented the spinal cord) was measured by an anesthetic gas analyzer. The concentration and partial pressure of sevoflurane in carotid artery (represented the brain) and abdominal aorta (represented the spinal cord) were determined using a gas chromatograph with the two-stage headspace equilibration method. RESULTS: When 1.5 mininum alveolar concentration (MAC) sevoflurane was administrated via lungs, the concentration and partial pressure of sevoflurane in the carotid artery were significantly higher than those in the abdominal aorta (P<0.05), with the end-tidal sevoflurane concentration higher than that of oxygenator outlet ( P<0.05), which indicated sevoflurane concentration and partial pressure in brain were higher than those in spinal cord. When 1.5 MAC sevoflurane was delivered via oxygenator,the indicators were conversed ( P<0.05), which indicated sevoflurane concentration and partial pressure in spinal cord were higher than those in brain. CONCLUSIONS: Based on the unique blood supply to the spinal cord of New Zealand white rabbits, we successfully established selectively anesthetized brain and spinal cord rabbit models.

The feasibility of measuring renal blood flow using transesophageal echocardiography in patients undergoing cardiac surgery.

BACKGROUND: There is no reliable method to monitor renal blood flow intraoperatively. In this study, we evaluated the feasibility and reproducibility of left renal blood flow measurements using transesophageal echocardiography during cardiac surgery. METHODS: In this prospective noninterventional study, left renal blood flow was measured with transesophageal echocardiography during three time points (pre-, intra-, and postcardiopulmonary bypass) in 60 patients undergoing cardiac surgery. Sonograms from 6 subjects were interpreted by 2 blinded independent assessors at the time of acquisition and 6 mo later. Interobserver and intraobserver reproducibility were quantified by calculating variability and intraclass correlation coefficients. RESULTS: Patients with Doppler angles of >30 degrees (20 of 60 subjects) were eliminated from renal blood flow measurements. Left renal blood flow was successfully measured and analyzed in 36 of 60 (60%) subjects. Both interobserver and intraobserver variability were <10%. Interobserver and intraobserver reproducibility in left renal blood flow measurements were good to excellent (intraclass correlation coefficients 0.604-0.999). Left renal arterial luminal diameter for the pre, intra, and postcardiopulmonary bypass phases, ranged from 3.8 to 4.1 mm, renal arterial velocity from 25 to 35 cm/s, and left renal blood flow from 192 to 299 mL/min. CONCLUSION: In patients undergoing cardiac surgery, it was feasible in 60% of the subjects to measure left renal blood flow using intraoperative transesophageal echocardiography. The interobserver and intraobserver reproducibility of renal blood flow measurements was good to excellent.

Synergistic myoprotection of L-arginine and adenosine in a canine model of global myocardial ischaemic reperfusion injury.

BACKGROUND: Endogenous nitric oxide and adenosine increase simultaneously to keep the balance of energy demand and supply when the oxygen supply is insufficient, which suggests that nitric oxide and adenosine might exert a synergistic myoprotection during tissue hypoxia. In this study, we tested this hypothesis utilizing a canine model of prolonged global myocardial ischaemic reperfusion injury. METHODS: In this double blind, controlled study, the hearts of 24 anaesthetized mongrel dogs were arrested for 2 hours with aortic cross clamping and blood cardioplegia. The treatment groups were those supplemented with 2 mmol/L L-arginine (ARG), supplemented with 1 mmol/L adenosine (ADO), ARG + ADO supplemented with both, and no supplementation (control) (n = 6 in each group). Haemodynamics, biochemical indices, adenosine triphosphate (ATP) content and myeloperoxidase activities of myocardium were determined to evaluate myocardial injury. Statistical comparison was performed by two way ANOVA. RESULTS: Although the requirements for inotropic supports were higher, the cardiac outputs were lower in control group than in ARG, ADO and the combination groups. Plasma cardiac troponin I levels were higher and the areas of hydropic changes were larger in control group than in ARG and ADO groups. Combination of arginine and adenosine provided further myoprotection with respect to better cardiac performance, lower release of cardiac troponin I, and smaller areas of hydropic changes compared with ARG and ADO groups. ATP content was higher, but myeloperoxidase activities of myocardium were significantly lower in the combination group than in control, ARG and ADO groups (P < 0.05). CONCLUSIONS: Combination of L-arginine and adenosine provides synergistic myoprotection in a canine model of global myocardial ischaemia. Thus, the combination is recommended when the heart is exposed to a prolonged ischaemia during cardiac surgery.