Katie Patel

Prevention of Nitroprusside-Induced Cyanide Toxicity with Hydroxocobalamin

To investigate hydroxocobalamins role in preventing cyanide intoxication from sodium nitroprusside, we studied two groups of patients. One group received nitroprusside alone, and the other received nitroprusside and hydroxocobalamin. Red-cell and plasma cyanide levels were 83.44 +/- 23.12 and 3.51 +/- 1.01 microgram per 100 ml after nitroprusside alone and were 33.18 +/- 17.29 and 2.18 +/- 0.65 microgram per 100 ml after nitroprusside plus hydroxocobalamin. Acidosis developed in patients with red-cell cyanide levels higher than 75 microgram per 100 ml. When hydroxocobalamin infusion was stopped before sodium nitroprusside infusion was discontinued, blood cyanide levels and base deficit increased in a manner similar to that in the untreated group. The dose of nitroprusside used in each group did not differ statistically. These data show that hydroxocobalamin prevents cyanide transfer from red cells and plasma to tissue after nitroprusside metabolism, and thereby prevents cyanide toxicity from large intravenous doses of the drug.

Cerebrospinal fluid cyanide after nitroprusside infusion in man

Sodium nitroprusside (SNP) is frequently used as an hypotensive agent for clipping of intracranial aneurysms, repair of arteriovenous malformations and resection of vascular tumours. Cyanide (CN), which is its main metabolic product, has been recovered from the cerebrospinal fluid (CSF) of the rat after intravenous administration of CN, but recovery of CN from CSF after SNP has not been reported in man.Seven consenting adults were studied. Adequate premedication was provided with pentobarbitone 2 mg . kg-1 and atropine 0.4 mg one hour before operation. Anaesthesia was induced with thiopentone 8 mg . kg-1 and maintained with nitrous oxide 60 per cent with oxygen and supplemental fentanyl 0.05 mg and pancuronium 0.5-1 mg as needed. Lumbar subarachnoid, radial artery, central venous, and Foley urinary catheters were inserted. Arterial carbon dioxide tension (Paco2) was maintained between 4.6-5.32 kPa (35-40 torr) with an Air Shields ventilator. Red cell, plasma and CSF cyanide were measured using a digital ionanalyzer before and at 30 minutes interval after infusing SNP at a rate sufficient to maintain the blood pressure at two thirds of the pre-operative level. Average total dose of SNP was 0.51 mg kg-1. CN concentration in the red blood cells increased from 9.5 ± 2.05 to 75.12 ±17.12. Plasma CN increased from 0.54 ± 0.05 to 1.09 ± 0.14 µg percent. CSF CN increased from 0.11 ± 0.04 to 0.72 ± 0.07 µg per cent.Significant increase in red cell, plasma and CSF CN occurred five minutes after the start of SNP and returned to the preoperative level 19 hours later.RésuméLe nitroprusside de sodium est l’agent hypotenseur par excellence utilisé au cours des interventions intracranienne telles que malformation artério-veineuse, excision de tumeur vasculaire, réparation d’anévrysmes cérébraux. Le cyanure, principal métabolite du SNP a été retrouvé dans le liquide céphalo-rachidien du rat après administration intraveineuse de thiocyanate de sodium. Aussi une étude a été entreprise sur sept volontaires en vue de déterminer la quantité de cyanure présente dans le LCR de l’homme à la suite d’une injection intraveineuse de la substance susmentionnée (SNP).Ces patients ont reçu pentobarbitone 2 mg . kg-1 et atropine 0.4 mg, une heure avant l’intervention chirurgicale. L’induction anesthésique a été réalisée au thiopentone 8 mg . kg-1 et au protoxyde d’azote 60 pour cent. Du fentanyl et du pancuronium ont été ajoutés au besoin. Des cathéters ont été placés, respectivement dans le canal rachidien, l’oreillette droite et l’artère radiale. La Pco2 a été maintenue entre 4.66 et 5.32 kPa (35 et 40 torr) pendant toute la durée de l’intervention. La quantité de cyanure contenue dans le plasma, les globules rouges et le LCR a été calculée à l’aide d’un ionisateur digital à des intervalles de 30 minutes après l’injection de SNP. La pression artérielle de ces patients a été réduite aux 2/3 de la valeur trouvée avant l’opération. Pour une dose moyenne de 0.51 mg . kg-1 de SNP injecté, la concentration de cyanure retrouvée dans les globules rouges passait de 9.5 ± 2.05 à 75.12 ± 17.12. Au niveau du plasma cette concentration s’était élevée de 0.54 ± 0.05 à 1.09 ± 0.14 µg pour cent. Dans le LCR, le cyanure atteignait une concentration de 0.11 ± 0.4 à 0.72 ± 0.07 µg pour cent.Une augmentation considérable du cyanure dans les globules rouges, le plasma et le LCR a donc été observée 45 minutes après l’administration de SNP par voie intraveineuse chez l’homme, augmentation qui n’était plus notée 19 heures après l’injection.

A new double-lumen tube adapter.

One-lung anesthesia has gained acceptance because it isolates normal lung from contaminated lung and provides a motionless surgical field.’ The metal connectors of the double-lumen tube are usually connected to the common catheter mount (Carlens’ “Y” connector) by soft-rubber connectors. Ventilatory isolation of the lung is performed by clamping the rubber connector after disconnecting it from the metal connector, thus allowing the lung to deflate to atmospheric pressure. Tracheal or bronchial suction is accomplished through the disconnected metal connector of the double-lumen tube. This maneuver, however, requires an additional clamp. Existing rubber and metal connectors are difficult to attach and detach, causing delays in ventilation. In addition, rubber connectors are soft and may kink easily. We have devised a “double-lumen tube adapter” which obviates these disadvantages. Two identical three-way stopcocks were made by drilling two adjacent barrels into a duralumin plate (5 cm x 2.5 cm x 2 cm) weighing 64 g. Three channels were drilled into each barrel (total of six channels) forming two symmetrical systems (Fig 1). Channels at the machine end of the plate (Fig 1, channel 1) were welded to the right and left limbs of the common catheter mount. Channels drilled at the patient end of the plate (Fig 1, channel 2) received the metal connectors of the double-lumen tube. The third set of channels (Fig 1, channel 3) were left open for suction and vent purposes. The axes of the suction/vent channels were at 135 degrees and streamlined with the axes of the patient channels. A tight-fitting selector knob (Fig 1) was inserted into each barrel, thus converting it