The alkalinisation of bupivacaine for intercostal nerve blockade

A double-blind randomised study was performed to investigate the effect of pH adjustment of bupivacaine, with adrenaline 1:200,000, on the duration of block and pain relief after intercostal nerve blockade following thoracotomy. One group (n = 10) received bupivacaine with adrenaline 1:200,000 (pH = 4.1) and the other (n = 10) received alkalinised bupivacaine with adrenaline 1:200,000 (pH = 6.9). There was no significant difference in block duration (mean 23.9 and 26.4 hours respectively) visual analogue pain scores or morphine usage. Patients were more likely to have a block during the first 12 hours if they received alkalinised bupivacaine (p less than 0.01, Chi-squared test). A progressive regression of block, not previously described, was observed, explicable by means of spread of local anaesthesia to adjacent intercostal nerves. Alkalinisation of bupivacaine with adrenaline for intercostal nerve blockade has little clinical benefit.     

Spontaneous, Electrically, and Cesium Chloride Induced Arrhythmia and Afterdepolarizations in the Rapidly Paced Dog Heart

JONES, D.L., et al. : Spontaneous, Electrically, and Cesium Chloride Induced Arrhythmia and Afterdepolarizations in the Rapidly Paced Dog Heart. Despite frequent arrhythmia and sudden death in heart failure, attempts to study arrhythmia mechanisms in patients are difficult. The dog heart, paced for several weeks at a fast rate to induce heart failure is prone to arrhythmia. The aim of this study was to determine the activation patterns of spontaneous and electrically induced arrhythmia and the susceptibility of the failing dog heart to arrhythmia and early afterdepolarization (EAD) induced triggered activity elicited by exogenous administration of cesium chloride (CsCl). The hearts of 56 mongrel dogs were paced at 240 beats/min for 3–5 weeks (heart failure group). Twenty‐one similarly operated, but not paced dogs served as the control group. At baseline, all dogs were healthy as assessed electrophysiologically and hemodynamically. Spontaneous (bradycardia, tachycardia, and arrhythmic deaths) and electrically induced arrhythmia was frequent in dogs with heart failure. Also, the minimal dose of CsCl that produced ventricular tachycardia was significantly lower in the heart failure than the control dogs (1.02 ± 0.02 vs 1.21 ± 0.07 mMol/kg, P < 0.05 ). Epicardial mapping during spontaneous and electrically induced arrhythmia in the heart failure dogs showed initiation patterns with focal origin, often from multiple sites. This pattern was consistent with the patterns observed with CsCl induced ventricular tachycardia. In in vitro microelectrode studies, CsCl superfusion (2.5–5 mMol/L ) induced triggered activity due to EADs within 30 minutes, in seven of the eight Purkinje fibers from four heart failure dogs. EADs were also found in ventricular myocytes of papillary muscle from two heart failure dogs. In contrast, 5 mMol/L CsCl induced EADs in only one of eight Purkinje fibers from the hearts of four control dogs and no papillary myocytes even with continuous superfusion for up to 60 minutes (P < 0.01 ). These results demonstrate that pacing induced heart failure in the dog has an increased tendency to develop ventricular tachycardia and triggered activity unmasked by CsCl.     

Stiffness of the Distal Tip of Bipolar Pacing Leads

CAMERON, J., ET AL.: Stiffness of the Distal Tip of Bipolar Pacing Leads. The stiffness of a bipolar pacing lead, particularly between anode and cathode, may be responsible for myocardial penetration and perforation. Following an unprecedented 7% incidence of high threshold exit block with a single model bipolar ventricular endocardial lead, a study was undertaken to compare pacing lead stiffness between anode and cathode of six models of bipolar leads from two manufacturers; Telectronics (T) and Medtronics (M). Four leads had polyurethane insulation; T 030–284 (Laser Dish), T 329–259 (Cordis, Encor), M4012 (Target Tip), and M 4004 (Capsure). Two leads had silicone rubber insulation; M 5026 (Capsure) and M 5024 (Capsure SP). All leads were subjected to two stiffness tests. The Tip Deflection Test involved securing the lead at 45° at the indifferent electrode and applying a force to deflect the tip 5 mm. The three point bending test involved placing the lead over two fixed bars in contact with the anode and cathode. Midway a third bar was pushed onto the lead and the force to deflect the lead 2 mm was recorded. The results showed that pacing leads with polyurethane insulation were much stiffer than those with silicone rubber insulation. The T 030–284 because of its construction was found to be the stiffest. The next stiffest was the M 4012. Both these leads had an unacceptable incidence of high threshold exit block; 7% with the T 030–284 (89 implants) and 3% with the M 4012 (102 implants). No cases of high threshold exit block were documented with the other four pacing leads and in particular the silicone rubber M 5026 (344 implants). It is recommended that bipolar pacing leads with low stiffness between anode and cathode be used and that all new pacing leads be tested for stiffness prior to human implants.     

Possis Angiojet Rapid Thrombectomy System: A New Device for the Definitive Treatment of Thrombotic Coronary Lesions

The incidence of thrombotic lesions is relatively common, and is associated with increased risk and complications. The optimal approach to the percutaneous treatment of these high risk lesions remains unclear. The Possis Angiojet Rapid Thrombectomy System is a new device designed to remove intravascular thrombus by rheolytic thrombectomy. This article describes the use of the Possis Angiojet on a patient with peri-infarct angina and refractory thrombus in the left anterior descending coronary artery.