Potential sources of operating room air contamination: a preliminary study.

BACKGROUND: The Neptune® surgical suction system (NSSS) and the Bair Hugger® (BH) forced-air warmer both discharge filtered exhaust or heated air into the operating room (OR), often in close proximity to a surgical site. AIM: To assess the effectiveness of this filtration, we examined the quantity and identity of microbial colonies emitted from their output ports compared with those obtained from circulating air entering the OR. METHODS: Air samples were collected from each device using industry-standard sampling devices in which a measured volume of air is impacted on to a blood agar plate at a controlled flow rate. Twelve ORs were studied. Sample plates were incubated for one week per study protocol, then interpreted for colony counts and sent for species identification. FINDINGS: The average colony count from the NSSS exhaust was not significantly different from that obtained from room air samples, however the average count from the BH output was significantly higher (P=0.0086) than room air. Genetic identification profiles revealed the presence of environmental or commensal organisms that differed depending on the source. High variability in colony counts from both devices suggests that certain NSSS and BH devices could be significant sources of OR air contamination. CONCLUSIONS: Our study showed that the BH patient warming device could be a source of airborne microbial contamination in the OR and that individual BH and NSSS units exhibit a higher output of microbial cfu than would be expected compared with incoming room air. We make simple suggestions on ways to mitigate these risks.

Fiberoptic light source-induced surgical fires -- the contribution of forced-air warming blankets.

BACKGROUND: Fiberoptic light sources have been identified as a fire ignition mechanism in the operating room. This study attempted to determine whether a forced-air warming blanket (FAWB) could affect the ignition or spread of fire caused by a fiberoptic light source. METHODS: We exposed surgical drapes to a fiberoptic light source at close range. The results were categorized according to time to first smoke and damage resulting at 1 min. Data were analyzed using the Mann-Whitney rank-sum test. RESULTS: The sums of the rank values for the components of the drape indicated that there was a greater than 96.8-99.2% chance that the FAWB accelerated the time to first smoke. The FAWB appeared to protect the patient gown from damage during all trials. The presence of an FAWB under a surgical drape accelerated the time to first smoke when exposed to unprotected fiberoptic light sources, yet prevented damage to the underlying patient gown. In an actual surgical setting, it is likely that the FAWB would offer some protection to the patient's skin directly below the surgical drape. CONCLUSION: It is likely that the FAWB can offer some protection to the patient should an unprotected fiberoptic light source cause a fire.

The haemodilution enhanced onset of coagulation as measured by the thrombelastogram is transient.

BACKGROUND AND OBJECTIVE: Crystalloid haemodilution has been widely found to enhance coagulation onset, but the duration of this effect has never been documented. METHODS: Twelve healthy, consenting volunteers had a rapid infusion of 14 mL kg-1 of normal (0.9%) saline. Blood samples were taken, prior to (control), and immediately after (30 min) the rapid saline infusion was completed (30 min). They were then repeated at regular intervals up to 120 min. Haematocrit/platelet counts were taken to determine the degree of dilution and thrombelastograms, with and without platelet antagonists (ReoPro, Abciximab), were measured in all samples. Antithrombin levels were selectively measured. RESULTS: The haematocrit and platelet count showed a rapid dilutional decrease at 30 min (mean of -12.2% and -14.4%, respectively), with values returning towards baseline within 15 min after finishing the infusion. There was a significantly faster onset of coagulation (decrease in r-time) in the post-infusion sample (30 min) compared to control (P<0.05), again returning towards normal as the dilution effect was reversed. Similar thrombelastograms findings were evident in the plasma factor only group (platelets inhibited by ReoPro). Antithrombin levels changed in keeping with the haemodilution effect (P<0.0001). There was a linear relationship between antithrombin and thrombelastograms r-time (P=0.012). CONCLUSION: The faster onset of coagulation brought on by haemodilution return towards normal as the dilutional effect is reversed. This effect is mediated through plasma clotting factors. Of interest is the significant inverse correlation of the onset of coagulation increasing as the antithrombin levels decreased with dilution.

Nitrous oxide and laparoscopic bariatric surgery.

BACKGROUND: Nitrous oxide (N2O) is frequently used to supplement more potent anesthetic agents. One side-effect of N2O is its ability to expand an air-containing space. We investigated if N2O adversely affected operating conditions by distending normal bowel during laparoscopic bariatric procedures. METHODS: 50 morbidly obese patients were divided into 2 study groups. Group 1 patients were ventilated with a halogenated anesthetic/oxygen/air mixture, while Group 2 received a halogenated anesthetic/oxygen/N2O mixture. At 30, 60, and 90 min intervals during the operation, the surgeon was asked if N2O was being used. RESULTS: The surgeons responded correctly only 42% (30 min), 50% (60 min), and 48% (90 min) of the time. In Group 2 (N2O) patients, they incorrectly answered that N2O was not being used 88% (30 min), 68% (60 min), and 68% (90 min); and in Group 1 (air) patients, they incorrectly answered that N2O was being used 28% (30 min), 32% (60 min), and 36% (90 min) of the time. CONCLUSION: We found that using N2O did not cause noticeable bowel distention during laparoscopic bariatric procedures of relatively short duration.

Seizure duration with remifentanil/methohexital vs. methohexital alone in middle-aged patients undergoing electroconvulsive therapy.

BACKGROUND: The object of this study was to test whether substituting part of the methohexital dose with the short-acting opioid remifentanil would prolong seizure duration in middle-aged patients while providing a similar depth of anesthesia as with methohexital alone. This has been reported for the combined use of methohexital and remifentanil in elderly patients, but has not been investigated in middle-aged patients likely to require a higher total dose of methohexital for inducing anesthesia. METHOD: Seven patients (42+/-10 years; mean +/-SD) receiving electroconvulsive therapy (ECT) were anesthetized with methohexital (1.25 mg kg-1) or with methohexital (0.625 mg kg-1) plus remifentanil (1 micro g kg-1) in this randomized, double blind, crossover study. Additional methohexital was given as needed until loss of eyelash reflex was observed. Suxamethonium (1 mg kg-1) was used for muscular paralysis. RESULTS: Motor and EEG seizure durations were significantly longer after induction with methohexital plus remifentanil (45+/-14 and 58+/-15 s) than with methohexital alone (31+/-11 and 42+/-18 s). A methohexital dose of 1.2+/-0.3 and 1.9+/-0.3 mg was necessary to achieve loss of eyelash reflex if methohexital was used with and without remifentanil. Peak heart rate after ECT was significantly higher if remifentanil was coadministered with methohexital (148+/-12 vs. 126+/-24 b.p.m). CONCLUSION: Substituting part of the methohexital dose with remifentanil is a useful anesthetic technique to prolong seizure duration in middle-aged patients requiring a 1.5-fold higher induction dose of methohexital than elderly patients, the only population studied to date for the combined use of methohexital and remifentanil in ECT.

Immediate control of life-threatening digoxin intoxication in a child by use of digoxin-specific antibody fragments (Fab).

Digoxin-immune antibody fragments (Fab) for treatment of digitalis intoxication was introduced in 1976. Many reports have been published concerning this therapy for children, but few have focused on its immediate reversal of cardiac as well as extracardiac life-threatening manifestations of digoxin toxicity. We present a case of life-threatening digitalis intoxication in a child with postoperative renal insufficiency, after a Sennings procedure for transposition of the great arteries. Digoxin administration according to the nationally recommended dosage and intervals unexpectedly resulted in serum levels in the toxic range. Severe cardiac arrhythmias, haemodynamic instability and a rapid-increasing serum potassium level resulted. This report demonstrates how administration of Fab according to the manufacturer's dosage recommendation reversed the tachyarrhythmia immediately and re-established a normal level of serum potassium within minutes.

Fetal heart rate decelerations during ECT-induced seizures: is it important?

Electroconvulsive therapy (ECT) is sometimes indicated during pregnancy and may offer advantages over pharmacotherapy for the patient and the fetus (1,2). However, very little data is available on the impact of epileptic or ECT-induced seizures on the fetus. We report a case of brief fetal heart rate decelerations in a fetus associated with maternal ECT-induced convulsions.

Oral midazolam with an antacid may increase the speed of onset of sedation in children prior to general anaesthesia.

BACKGROUND: The aim of the study was to see whether sodium citrate solution would speed the gastric absorption of oral midazolam. METHODS: Forty presurgical ASA I and II patients (aged 2-6 years) were randomly assigned to one of two groups. Group I received midazolam 0.5 mg x kg(-1) mixed with sodium citrate while group II (control) received midazolam 0.5 mg x kg(-1) mixed with Hawaiian fruit punch. RESULTS: There was no statistical difference between the ages, weights, preoperative sedation and anxiety scores in the two groups. After premedication, the onset of sedation (mean +/- SD) measured by the first change in sedation score was found to be significantly faster (P < 0.05) in group I (17.8 +/- 7.11) compared with group II (21.9 +/- 5.34). There was no statistical difference in anxiety at any time intervals, separation or induction scoring for both groups. Gastric volumes and the pH of gastric aspirates between the two groups were not statistically significant. CONCLUSIONS: The time to onset of sedation can potentially be shortened, by using a preparation of intravenous midazolam and antacid, given orally.

Suppression of cough during emergence from general anesthesia: laryngotracheal lidocaine through a modified endotracheal tube.

STUDY OBJECTIVE: To ascertain if coughing during emergence from general anesthesia can be suppressed with a modified endotracheal tube. DESIGN: Randomized, double-blind, controlled study. SETTING: Operating rooms at a university hospital. PATIENTS: 46 adult ASA physical status I, II, and III patients requiring elective surgery. INTERVENTIONS: Patients underwent general anesthesia with the laryngotracheal instillation of topical anesthesia (LITA) endotracheal tube (ETT). Thirty minutes before anticipated extubation, one investigator administered, via the LITA tube injection port onto the laryngotracheal mucosa, one of the following according to randomized preselection: 2 mg/kg with 4% lidocaine (Group I; n = 15); 4 mL with saline (Group 2;n = 16); and nothing (Control; n = 15). At the completion of surgery, with the patient adequately anesthetized, the oropharynx was gently suctioned, and the isoflurane was then turned off. When the isoflurane end-tidal concentration was < or =0.2%, the neuromuscular block was reversed and the inspiratory oxygen concentration was increased to 100% while awaiting the return of spontaneous ventilation. MEASUREMENTS: An observer who was blinded to the study drug regimens judged the presence or absence of cough upon emergence, over a 1-minute period. The observer noted the responses to the following verbal commands, in this order: 1) "open your eyes", 2) "grip my hand", and 3) "lift your head". Coughing was defined as any evidence of irritation from having a tube in the trachea. Blood samples for plasma lidocaine levels were taken at the time of extubation from patients who received lidocaine (Group 1). MAIN RESULTS: Seventy-five percent of patients were found to have complete cough suppression upon emergence, while Group 2 (saline) had 14% and Group 3 (the control) only had 13% suppression. CONCLUSIONS: The technique of laryngotracheal topical lidocaine administered by the LITA tube can, in most cases, provide a smooth emergence from general anesthesia without coughing.

Isosulfan blue affects pulse oximetry.

BACKGROUND: Certain vital dyes are known to cause pulse oximetry (Spo2) desaturation. The authors studied the effect of isosulfan blue (IB) on Spo2. METHODS: Thirty-three women, aged 34-81 yr, who were undergoing surgery for breast cancer were studied. IB, 5 ml (50 mg), was injected intraparenchymally around the tumor area by the surgeon. A pulse oximeter was used to continuously record Spo2 values up to 130 min after IB injection. Friedman repeated-measures analysis of ranks was used to analyze the baseline Spo2 and values at 5, 10, 20, 30, 40, 50, and 60 min. RESULTS: Spo2 values were significantly different from baseline values at 5, 10, 20, 30, 40, 50, and 60 min (P < 0.05). In a typical patient, a maximum Spo2 decrease of 3% can be anticipated 25 min after injection of IB. CONCLUSIONS: After peritumoral administration of IB, 50 mg, a significant interference with Spo2 will occur.

General anesthesia in a patient on long-term amphetamine therapy: is there cause for concern?

IMPLICATIONS: Amphetamines are powerful, sympathomimetic amines that, when used chronically, can profoundly effect a patient's cardiovascular stability during anesthesia and surgery. Amphetamines are the third most widely abused class of drugs in the United States. They also have legitimate medical use for attention deficit disorder with hyperactivity, exogenous obesity, and narcolepsy. We report a case of a patient with a 40-yr history of chronic amphetamine use having undergone two general anesthesias without complication.