Effects of a prophylactic or therapeutic application of perflubron emulsion on myocardial ischaemia-reperfusion injury in rats.

BACKGROUND AND OBJECTIVE: The efficacy of administering a perfluorochemical-based oxygen therapeutic such as perflubron emulsion (Oxygen) prior to ischaemia is currently unknown, although there is evidence for potential beneficial effects for the perioperative treatment in cardiac risk patients. This experimental study investigated the efficacy of perflubron emulsion in preventing reperfusion injury and myocardial infarction size after coronary ischaemia and reperfusion. The perflubron emulsion was given either in a prophylactic manner, prior to induction of myocardial ischaemia, or as a therapeutic agent given during ischaemia. METHODS: Thirty-two anaesthetized and mechanically ventilated rats were subjected to 25 min occlusion of the left coronary artery followed by 120 min reperfusion. Animals were randomized to one of four groups:Group 1 was treated with administration of 6 g kg (-1) intravenous perflubron emulsion 25 min before occlusion; Group 2 received the same dose 10 min after occlusion; and Groups 3 and 4 received no perflubron emulsion. Inspired O2 (FiO2) concentration was maintained at 1.0 in Groups 1, 2 and 3 and at 0.35 in Group 4. RESULTS: Neither prophylactic nor therapeutic perflubron emulsion treatment reduced infarct size measurements by triphenyltetrazolium-chloride staining or severity of cardiac arrhythmias in comparison to the hyperoxic control group. However, prophylactic application of perflubron emulsion reduced areas of impaired perfusion vs. Group 3 assessed by in vivo staining with Thioflavin-S while no significant effect was seen in Groups 2 and 4 vs. 3. Density of DNA single-strand breaks in the ventricle was increased in all groups ventilated with 100% oxygen. CONCLUSION: Although administration of perflubron emulsion did not reduce infarct size, areas of impaired perfusion were significantly mitigated when perflubron emulsion was administered prior to coronary occlusion. However, a high oxygen concentration may provoke DNA strand breaks during reperfusion after ischaemia. Further studies must clarify whether enhanced oxidative stress outweighs the advantage of improved areas of impaired perfusion following perflubron emulsion.

Comparative study of different concentrations of prilocaine and ropivacaine for intraoperative axillary brachial plexus block.

BACKGROUND AND OBJECTIVE: To compare the anaesthetic characteristics in terms of onset and offset times of the sensory and motor blocks of prilocaine 1% and ropivacaine 0.75% alone and in different combinations when used for brachial plexus anaesthesia in axillary perivascular blocks. METHODS: After informed consent 96 ASA I-III patients undergoing forearm or hand surgery participated in this prospective, randomized, double-blind study. Patients received either prilocaine 1% 40 mL (G1), prilocaine 1% 30 mL and ropivacaine 0.75% 10 mL (G2), prilocaine 1% 20 mL and ropivacaine 0.75% 20 mL (G3) or ropivacaine 0.75% 40 mL (G4) for axillary perivascular brachial plexus anaesthesia. Onset and duration of sensory and motor blocks in the distribution of the musculocutaneous, radial, median and ulnar nerves were assessed. RESULTS: The onset time of the sensory and motor blocks of the whole brachial plexus differed only between patients in G4 with ropivacaine 0.75% 40 mL demonstrating a later motor onset in comparison to all other groups and a later sensory onset in comparison to G1 and G2 (P < 0.01). The addition of ropivacaine resulted in longer offset times of the sensory and motor blocks. The median offset time of the motor block was 179.5 min in G1, 262 min in G2, 389.5 min in G3 and 745 min in G4 (P < 0.01). The median offset time of the sensory block was 163.5 min in G1, 277 min in G2, 383.5 min in G3 and 784 min in G4 (P < 0.01). There was no difference in onset and offset times between sensory and motor blocks within the groups. CONCLUSIONS: For axillary perivascular brachial plexus block prilocaine 1% alone and in combination with ropivacaine 0.75% was similar in terms of onset of sensory and motor blocks but different in duration of sensory and motor blocks without a differential sensory and motor offset.

Effects of prophylactic or therapeutic application of bovine haemoglobin HBOC-200 on ischaemia-reperfusion injury following acute coronary ligature in rats.

BACKGROUND: Haemoglobin-based oxygen carriers (HBOCs) are assessed as blood substitutes in patients with perioperative anaemia including patients at risk for perioperative cardiac ischaemia. There is controversy as to whether HBOCs are beneficial or deleterious during ischaemia-reperfusion (I-R). Therefore the effects of HBOC-200 on I-R injury were evaluated in a randomized placebo-controlled animal trial. METHODS: Animals were randomized to receive either placebo i.v. without I-R (sham group, n=9), placebo i.v. with I-R (control group, n=10), HBOC-200 0.4 g kg(-1) i.v. prior to I-R (prophylaxis group, n=12) or HBOC-200 0.4 g kg(-1) i.v. during I-R (therapy group, n=15). I-R consisted of 25 min of acute ligature of the left coronary artery followed by 120 min of reperfusion. Measurements included assessment of the area at risk and infarct size using triphenyl tetrazolium chloride (TTC) stain, DNA single-strand breaks (in situ nick translation with autoradiography/densitometry) and cardiac arrhythmias. RESULTS: Infarct size within the area at risk was 62 (sd 15)% (control), 46 (10)% (prophylaxis, P<0.025 vs control) and 61 (9)% (therapy, P<0.85 vs control). The frequency of DNA single-strand breaks was reduced vs control in the sham (P<0.01) and prophylaxis (P<0.04) groups and was almost the same in the therapy group (P<0.75). The severity of cardiac arrhythmias during ischaemia was lower compared with control in the sham (P<0.001) and prophylaxis (P<0.039) groups, but there was no difference in the therapy group. CONCLUSION: This study demonstrates that neither prophylactic nor therapeutic application of the cell-free haemoglobin solution HBOC-200 aggravates cardiac I-R injury. Furthermore, the prophylactic approach may offer a new opportunity for pretreatment of patients at risk for perioperative ischaemic cardiac events.