Immobilization during anesthesia for vitrectomy using a laryngeal mask without neuromuscular blockade versus endotracheal intubation and neuromuscular blockade.

BACKGROUND: For intraocular surgery, most authors recommend general anesthesia including intubation and neuromuscular blockade to avoid complications by patient movements. However, anesthesia using a laryngeal mask and avoidance of muscle relaxants is common clinical practice. Purpose of this prospective observational study was to compare the incidence of eye movement and deviation of the eye axis during general anesthesia adjusted to minimal alveolar concentration (MAC) for pars plana-vitrectomy (PPV) using a laryngeal mask without neuromuscular blockade (LM) versus endotracheal intubation and neuromuscular blockade (INT). METHODS: The patients (N.=148) who underwent PPV for vitreoretinal disorders received MAC adjusted general anesthesia by volatile anesthetics. Seventy-four patients were subjected to LM and 74 to INT. In both groups the patient's lungs were mechanically ventilated without allowing spontaneous ventilation. Eye movements and upward deviations were judged and documented during surgery. Postoperatively quality of immobilization was assessed by a standardized questionnaire. RESULTS: Intraoperative movements were not observed in either group. Upward eye deviation was observed in nine (12%) patients in the LM group, but not in patients in the INT group (0%; P=0.003). The standardized questionnaire revealed no clinically relevant difference in quality of immobilization between groups, especially eye deviations did not lead to any relevant surgical complications or difficulties. CONCLUSIONS: For PPV, MAC adjusted balanced anesthesia using a laryngeal mask without neuromuscular blockade was associated with more, but clinically irrelevant upward eye deviations and may be an alternative to intubation with neuromuscular blockade. However, adequate depth of anesthesia must be assured to avoid unwanted injuries during surgery.

Effect of ischemic and pharmacological preconditioning of lower limb muscle tissue on tissue oxygenation measured by near-infrared spectroscopy--a pilot study.

BACKGROUND: Ischemic or volatile anesthetic preconditioning is defined as tissue protection from impending ischemic cell damage by repetitive short periods of tissue exposure to ischemia or volatile anesthetics. Objective of this study was to elucidate, if ischemic preconditioning and pharmacological preconditioning with sevoflurane have effects on muscle tissue oxygen saturation in patients undergoing surgical revascularization of the lower limb. METHODS: In this prospective randomized pilot study ischemic and pharmacological (sevoflurane) preconditioning was performed in 40 patients with lower limb arterial occlusive disease undergoing surgical revascularization. Sevoflurane preconditioning was performed in one group (N = 20) by repetitive application of sevoflurane for six minutes interspersed by six minutes of washout. Thereafter, ischemic preconditioning was performed in all patients (N = 40) by repetitive clamping of the femoral artery for six minutes interspersed by six minutes of reperfusion. The effect of both procedures on leg muscle tissue oxygen saturation (rSO2) was measured by near-infrared spectroscopy during both procedures and during surgery and reperfusion (INVOS® 5100C Oxymeter with Small Adult SomaSensor® SAFB-SM, Somanetics, Troy, Michigan, USA). RESULTS: Repetitive clamping and reperfusion of the femoral artery resulted in significant cyclic decrease and increase of muscle rSO2 (p < 0.0001). Pharmacological preconditioning with sevoflurane resulted in a faster and higher increase of rSO2 during postoperative reperfusion (Maximal 111% baseline ± 20 versus 103% baseline ± 14, p = 0.008) consistent with an additional effect of pharmacological preconditioning on leg perfusion. CONCLUSIONS: Ischemic preconditioning of lower limb muscle tissue and pharmacological preconditioning with sevoflurane have an effect on tissue oxygenation in patients with lower limb occlusive arterial disease. TRIAL REGISTRATION: The trial has been registrated at http://www.ClinicalTrial.gov, TRIAL NUMBER: NCT02038062 at 14 January 2014.