Berton Braverman

Growth of Staphylococcus aureus in four intravenous anesthetics

Patient infections related to the use of propofol have been reported. To investigate the growth of Staphylococcus aureus in propofol, thiopental, methohexital, etomidate, and 0.9% saline containing no bacteriostatic drug, these preparations were inoculated and samples were plated onto blood agar at 0,3,6,21,24, and 27 h. The number of colony-forming units (CFU) on the plates was then determined after 24 h of incubation. Samples from the inoculated etomidate solution showed zero CEU at 3 h and thereafter, whereas 21 h were required by the methohexital and thiopental solutions to reduce the number of CFU to zero. For normal saline, no significant change in CFU was seen before the first 6 h, then the number of CFU gradually declined, although some S. aureus CFU were still present at 27 h. Inoculation of the propofol emulsion resulted in a substantial growth of S. aureus between 6 and 21 h after inoculation. We conclude that, of the preparations tested, only propofol was an excellent medium for the rapid growth of S. aureus. Meticulous sterile technique, therefore, is advised when handling it.

Sodium thiosulfate disposition in humans: relation to sodium nitroprusside toxicity.

Thiosulfate concentrations and pharmacokinetics were studied in relation to sodium nitroprusside before, during, and after anesthesia. Normal thiosulfate concentrations were 1.13 ± 0.11 mg/dl and 0.28 ± 0.02 mg/dl in plasma and urine, respectively. Cholecystectomy patients had similar concentrations during surgery, with bile thiosulfate concentration of 13.72 ± 2,95 mg/dl. Fasting patients and children had significantly higher plasma and urine thiosulfate concentrations. Over 99% of endogenous filtered thiosulfate was reabsorbed by the kidney in the average case. Coronary bypass patients had decreased plasma thiosulfate levels and increased excretion postoperatively. Disappearance of injected thiosulfate was biphasic; the distribution phase was dependent on the initial rate of injection, and the elimination phase depended on extracellular fluid turnover and renal excretion. Cholecystectomy patients on diurectics had a markedly increased rate of excretion, 56% within 100 min, versus normal subjects who excreted less than 50% in up to 18 h. In children, plasma thiosulfate did not change significantly, while blood cyanide concentration increased significantly during sodium nitroprusside administration and surgery. Thiosulfate did not change during recovery while cyanide decreased. Normal production of thiosulfate in humans may be limited; hence, continuous thiosulfate infusion may be required during sodium nitroprusside administration.

Cyanide antidotes and methods of their administration in dogs: a comparative study.

To test the efficacies of various antidotes to cyanide (CN) poisoning, the lethal dose of cyanide in dogs was estimated during constant infusion of potassium cyanide at a rate of 0.1 mg/kg/min. Additionally, arterial blood pressure, right ventricular pressure, heart rate, electrocardiogram, blood-gas and pH values, and whole blood and tissue CN concentrations were measured. The lethal dose in animals whose lungs were ventilated with room air was 2.4 ± .2 mg/kg (mean ± SE), while the whole-blood CN concentration was 438 ± 40 µg/dl and the gracilis muscle concentration was 2.0 ± .3 µg/100 g. A low dose of vitamin B12a (100 mg/kg), an infusion of thiosulfate (12 mg/kg/h), or ventilation with 100 per cent O2 increased the amount of CN needed to cause death. A bolus injection of nitrite (5 mg/kg), thiosulfate (150 mg/kg), or cysteine (450 mg/kg) increased the protection from lethality even further. Protection against CN administration for the total 150-min period of observation was provided by a bolus injection plus a constant infusion of nitrite (5 mg/kg bolus plus 5 mg/kg/h), (hiosulfate (30 mg/kg bolus plus 60 mg/kg/h), or vitamin B12a (50 mg/kg bolus plus 100 mg/kg/h). However, nitrite infusion produced high levels of methemoglobin 7.2 ±1.1 g/dl, while vitamin B12a infusion and cysteine injection, at the stated doses, did not prevent cyanide-induced circulatory failure. Therefore, thiosulfate appears to be the most effective and safest prophylactic agent against cyanide toxicity in dogs.

Hemodynamic responses to endotracheal extubation after coronary artery bypass grafting

After coronary artery bypass grafting (CABG) surgery, patients may remain at risk for myocardial ischemia and infarction and ventricular dysrhythmias. The hemodynamic responses to endotracheal extubation and the efficacy of intravenous lidocaine pretreatment were studied after CABG surgery and overnight mechanical ventilation. Twenty-five patients were divided into two groups: group 1 (n = 13) patients who had tracheal extubation after pretreatment with a placebo; group 2 patients who received lidocaine (1 mg/kg IV) before tracheal extubation. Hemodynamic data, electrocardiographic tracings, and arterial blood gases were obtained before tracheal extubation, during suctioning, and 1, 5, and 20 min after tracheal extubation. Group 1 patients displayed significant increases in heart rate, arterial blood pressure, rate-pressure product, right atrial pressure, and cardiac index during suctioning and within 1 min of tracheal extubation, returning to preextubation level by 5 min. There were no significant changes in pulmonary and systemic resistance indices. Hemodynamic changes in group 2 patients were similar to those in group 1. Both in the absence and presence of lidocaine, tracheal extubation caused hemodynamic responses that were small in magnitude and brief in duration. These responses were not associated with electrocardiographic or enzymatic evidence of myocardial ischemia or infarction, or with ventricular dysrhythmias. Compared with the well-documented hemodynamic responses to tracheal intubation, we found that extubation of the trachea after CABG surgery was associated with less pronounced responses. This may be related to avoidance of laryngoscopy and possibly accommodation to the endo-tracheal tube. These modest hemodynamic responses of extubation of the trachea after CABG surgery were not modified by intravenous lidocaine.

Propofol, but not thiopental, supports the growth of Candida albicans

We determined whether propofol, thiopental, or 0.9% saline would serve as a growth medium for Candida albicans. In Part I, we investigated whether opening 20 propofol ampules would cause glass particles from the exterior of the ampule to fall into the emulsion and contaminate it. Each ampule was painted with red fingernail polish and its contents were passed through filter paper after it was opened in a routine manner. In Part II, a sample from a colony of C. albicans was added to sterile vials containing 20 mL of either 0.9% saline, 1% propofol, or 2.5% thiopental. A 1- micro Liter sample from each vial was then plated onto Sabarouds dextrose plus brain-heart infusion (SABHI) agar at the following times after inoculation: 0, 3, 6, 16, and 24 h. The plates were incubated at 35 degrees C for 24 h and the number of colony-forming units counted. The filtration of two of the painted ampules in Part I revealed red glass fragments. In Part II, the saline and thiopental solutions did not increase the number of colonies of C. albicans by 24 h. However, the propofol, after a latent period between 6 and 16 h, supported the growth of C. albicans at a rapid rate. Our investigation shows that glass particles from the exterior of a propofol ampule can contaminate its contents when the ampule is opened in a routine manner. Furthermore, propofol provides an excellent growth medium for C. albicans. Thiopental and saline showed no growth. We conclude that the ability of propofol to grow C. albicans necessitates rigorous standards of sterility in its handling. (Anesth Analg 1995;81:132-4)

Thiosulfate Pharmacokinetics in Normal and Anuric Dogs

Abstract Cyanide (CN) toxicity has recently become increasingly a clinical problem with the greater use of Laetrile for cancer treatment and of sodium nitroprusside for blood pressure control. Sodium thiosulfate is an excellent antidote for CN toxicity but not all aspects of its pharmacokinetics have been adequately studied. Applying a specific thiosulfate assay, we measured endogenous thiosulfate, the response to CN infusion, and disappearance after iv injection in normal and anuric dogs. Endogenous plasma concentration was approximately 1 mg/dl; the bile concentration was 15 times higher but biliary excretion accounted for less than 2%, compared to renal excretion. Cyanide infusion decreased endogenous plasma thiosulfate 33% before death. The fast component of the thiosulfate disappearance curve was similar, 3 min, after iv injection (150 mg/kg), while the second component was markedly prolonged in anuric dogs (239 min) compared to controls (47 min). Therefore, a constant infusion of thiosulfate would appear to be the best method of maintaining the high plasma concentration necessary for CN detoxification during the continuous administration or absorption of CN-producing compounds.

Prevention of cautery-induced airway fires with special endotracheal tubes

A lthough cautery is often used as a means of achieving hemostasis during surgery, it is associated with serious hazards. In common with the complications of laser airway surgery, the surgical cautery can ignite combustible endotracheal tubes during otolaryngologic or oral surgery, and these fires can kill or injure patients (1-5). The possibility of such fires requires the use of special anesthesia techniques and equipment. This investigation was designed to determine whether the shafts and tips of commercially available endotracheal tubes, designed for use with the C02 laser during airway surgery, which have been evaluated by our group (6,7) for that application, are also resistant to electrocautery-induced combustion. In addition, we determined whether red rubber endotracheal tubes are less susceptible to cautery-induced combustion than polyvinylchloride (PVC) endotracheal tubes.

Evaluation of Foil Coverings for Protecting Plastic Endotracheal Tubes from the Potassium-titanyl-phosphate Laser

The potassium-titanyl-phosphate laser is being used for airway surgery and could cause an endotracheal tube fire. To determine whether five different metallic foil tapes or the Laser-Guard protective wrap would protect polyvinylchloride (PVC) endotracheal tubes from this laser, it was set to a power of 18 W and aimed at the wrapped endotracheal tube under study for up to 1 min while 5 L/min of oxygen flowed through the endotracheal tube. A plain (unwrapped) PVC endotracheal tube was studied also. The plain PVC endotracheal tube was ignited by the laser after 14 s. Potassium-titanyl-phosphate laser radiation did not significantly affect the nonadhesive sides of the foil tapes tested or the Laser-Guard covering. However, potassium-titanyl-phosphate laser radiation caused ignition or melting of underlying PVC endotracheal tubes when it was applied to the endotracheal tubes with the adhesive side of the foil tapes facing outward. It is concluded that only the Laser-Guard protective coating adequately protected the PVC endotracheal tubes tested under the conditions of this experiment.

Prevention of nitroprusside toxicity with thiosulfate in dogs.

The dose of sodium nitroprusside (SNP) that can be safely used for deliberate hypotension is limited by the toxicity of cyanide (CN), its metabolite. The cardiovascular effect of combining sodium thiosulfate with SNP in dogs was investigated to determine whether this combination might protect against CN toxicity without altering the SNP-induced hemodynamic changes. Ten pentobarbital-anesthetized dogs were divided into two equal groups, intubated, and maintained on room air. Control animals (group C) received an infusion of 0.7 ml/min of normal saline; test dogs (group T) received a bolus of sodium thiosulfate, 30 mg/kg, followed by 30 mg/kg/hr infused at 0.7 ml/min. Hypotension (mean blood pressure of 60 mm Hg) was then induced and maintained by SNP for 5 hours in both groups. In group T, heart rate (HR) first increased, then returned to base levels after 60 minutes of hypotension, whereas in group C, HR decreased steadily and after 5 hours was 29 beats per minute less than its initial rate. Cardiac output increased initially in both groups and then returned to starting levels after 180 minutes of hypotension. The SNP infusion rate, mean dose 0.8 mg/min (37 ± 5 μg/kg/min) initially in both groups, was kept at this rate throughout hypotension for group T, but had to be reduced steadily to 0.17 mg/min (8 ± 1 μg/kg/min) for group C. The whole-blood CN level in group T rose to 39 μ 9 μg/dl; in group C, it rose to 381 ± 44 μg/dl at 150 minutes, then decreased to 304 ± 114 μg/dl when the SNP infusion rate was at its minimum. Endogenous plasma thiosulfate concentration was initially 1.3 ± 0.32 mg/dl in group C and 1.04 ± 0.09 mg/dl in group T. During SNP infusion, plasma levels of endogenous thiosulfate decreased to 0.91 ± 0.16 mg/dl (p < 0.05) in group C, whereas in group T the infusion of thiosulfate increased the plasma levels of thiosulfate and maintained them at approximately 15.5 mg/dl for 300 minutes. Blood gas tensions and pH were not significantly different between the two groups during most of the study; the venous pH decreased in both groups but to a greater extent in group C. These findings suggest that thiosulfate is effective in maintaining a safe blood CN concentration when high doses of SNP are required to maintain hypotension for 5 hours without altering the SNP-induced hemodynamic effects.

GROWTH OF STAPHXLOCOCCUS AUREUS IN FOUR INTRAVENOUS ANESTHETICS

Patient infections related to the use of propofol have been reported. To investigate the growth of Staphylococcus aureus in propofol, thiopental, methohexital, etomidate, and 0.9% saline containing no bacteriostatic drug, these preparations were inoculated and samples were plated onto blood agar at 0, 3, 6, 21, 24, and 27 h. The number of colony-forming units (CFU) on the plates was then determined after 24 h of incubation. Samples from the inoculated etomidate solution showed zero CFU at 3 h and thereafter, whereas 21 h were required by the methohexital and thiopental solutions to reduce the number of CFU to zero. For normal saline, no significant change in CFU was seen before the first 6 h, then the number of CFU gradually declined, although some S. aureus CFU were still present at 27 h. Inoculation of the propofol emulsion resulted in a substantial growth of S. aureus between 6 and 21 h after inoculation. We conclude that, of the preparations tested, only propofol was an excellent medium for the rapid growth of S. aureus. Meticulous sterile technique, therefore, is advised when handling it.