1 I04

Correspondence

postlumbar puncture headache comparable to that of spinal anaesthesia [ I , 21. Secondly, the elongated lateral eye of the Sprotte needle is more suitable for preventing inadvertent intraneural injection in neural blockade procedures. These definite advantages of the large lateral eye have to be taken into account when considering the theoretical drawbacks referred to by Aglan and Stansby. With regard to the alleged greater failure rate, this was not apparent during spinal anaesthesia in the 6-year testing phase preceding initial publication [3]. A prospective random double-blind study revealed a significantly lower number of incomplete blocks for the 24-gauge Sprotte needle compared to a 25-gauge Quincke needle (1.6% vs 7.8%) 141. Furthermore, routine use of the 24-gauge Sprotte cannula in a number of neuroradiological departments over a period of several years indicated that there were no problems with double epidural-spinal injection of contrast media during myelography, i.e. with free CSF aspiration, the entire contents of the syringe are distributed solely in the subarachnoid space. Naturally, the stability of the needle tip is greater if the lateral eye is smaller. Therefore a special quality steel is employed for the production of these needles to compensate for the lateral eye and reduced wall thickness 141. For use in the USA the FDA require comprehensive physical testing. To avoid any misunderstandings it should be pointed out at this juncture that for comparative purposes we were forced to refer to 22 and 25-gauge Whitacre needles from Becton and Dickinson, which

despite their smaller lateral eye proved to be more unstable than the 22 and 24-gauge Sprotte cannula (Test Certificate of TUV Product Service Abt. Chemie, Medicalprodukte Munich 18.06.91). I should like to express my thanks to Drs Aglan and Stansby for their constructive contribution, which discusses one critical aspect of the Sprotte needle and at the same time offers me the opportunity to comment on this publicly. Institut fur Anaesthesiologie, Universitat Wurzburg, Germany

G. SPROTTE

References [I] JAGER H, SCHIMRIGK K, HAAS A. Das postpunktionelle Syndrom selten bei der Punktionshadel nach Sprotte (Eng. Abstr.) Postlumbar puncture headache prevention by means of an “atraumatic” needle Akt. Neurology 1991; 18: 6 1 4 . 121 ENGELHARD A, OHEIMS, NEUNDORFER B. Lumbar puncture with a new atraumatic needle. Journal of Neurology 1990; 237: 54. [3] SPROTTEG, SCHEDEL R, PAJUNKH, PAJUNKH. Eine atraumatische Universalkaniile fur einzeitige Regionalanaesthesien (Eng Abstr.) Regional-Anaesthesie 1987; 1 0 104-8. [4] BOTTNERJ, WRFSCH KP, KLOSE R. Bietet eine konisch geformte Kaniilenspitze Vorteile bei der Spinalanesthesie?(Eng Abstr.) Regional-Anaesthesie 1990; 13 124-8.

Intravenous magnesium therapy in critically ill patients Magnesium homeostasis 11-31, the use of magnesium in the control of tachyarrhythmias in critically ill patients [4, 51, and the effect of magnesium on mortality following acute myocardial infarction (LIMIT-2 study) [6], have been the subject of several recent reports. A number of different dosing schedules have been documented. Some regimens suggest fairly rapid infusion of magnesium sulphate (20 mmol (5 G) over 1 min [4], 8 mmol (2 G) over 5 min [6]), while others are more circumspect: 40 mmol (10 G) over 24 h [3]. Using a ’rapid’ regimen (8 mmol.5 min-I), we administered magnesium sulphate to three patients suffering from Gram-negative septicaemia, who were subject to a variety of tachyarrhythmias (atrial fibrillation, nodal/supraventricular tachycardia, recurrent ventricular ectopy). In two patients, hypotension (due to a fall in systemic vascular resistance (SVR) and requiring increased inotropic support) persisted for over 4 h. A third patient again showed a fall in SVR but unaccompanied by hypotension because of a significant increase in cardiac output. The hypotensive response was not unexpected although we were surprised by its duration, particularly as hypotension had not been a significant problem in the LIMIT-2 study [6] whose dosage schedule we were using. Despite this, in all three patients, the arrhythmias were significantly blunted. Since these experiences, we have altered our regimen, so that magnesium (48 mmol) is infused over 24 h.

Hypotension has not been noticeable. We suggest that in septicaemic patients (who are subject to global myocardial depression, unlike most patients suffering from acute myocardial infarction), magnesium should be infused slowly, unless there is clear evidence of clinical hypomagnesaemia (e.g. fasciculation, hypotonia etc). South Cleveland Hospital, Middlesbrough Cleveland TS4 3B W References [I] GAMBLING DR, BIRMINGHAM CL, JENKINS LC. Magnesium and the anaesthetist. Canadian Journal of Anaesthesia 1988; 35: 64454. [2] CHERNOW B, BAMBERGER S, STOIKO M, VADNAISM. MILLSS , HOELLERICH V, WARSHAW AL. Hypomagnesemia in patients in postoperative intensive care. Chest 1989; 9 5 391-7. [3] JAMESMFM. Magnesium in critical care medicine. Care

Intravenous magnesium therapy in critically ill patients.

1 I04 Correspondence postlumbar puncture headache comparable to that of spinal anaesthesia [ I , 21. Secondly, the elongated lateral eye of the Spro...
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