Lewis A. Coveler

Subacute Upper Respiratory Infection in Small Children

Although it is widely accepted as good practice to avoid elective administration of general anesthesia to a patient who has an acute upper respiratory infection (URI), there is a paucity of information regarding the nature of the morbidity that may result if anesthesia were administered. Furthermore, the optimal period of recovery from the URI that should be allowed prior to considering the patient a candidate for an elective surgical procedure has not been defined. The following are two case reports which are representative of 11 patients who developed unexplained intra-anesthetic pulmonary dysfunction. The common factor in all but one patient was a history of an upper respiratory infection during the previous month.

Invasive pressure monitoring of patients during magnetic resonance imaging

The purpose of this paper is to describe a system for monitoring patients who require general anaesthesia, profound sedation or intensive care while undergoing high field (≥1.5 T) magnetic resonance (MR) imaging. Continuous evaluation of invasive and noninvasive pressures, inspired and end-tidal respiratory gas concentrations, body temperature, heart rate, ECG and pulse oximetry were measured successfully during the MR examination. Diagnostic quality MR images were acquired on all 15 monitored patients. The calculated signal-to-noise ratios were not different between the control and monitored patients. Commonly encountered technical problems and their solutions are described. This study demonstrates that invasive monitoring can be safely performed in critically ill patients who are undergoing high field MR examinations.RésuméCet article décrit un système de monitorage pour des patients soumis à une imagerie par résonance magnétique à champ de rayonnement de forte intensité (≥1,5 T) sous anesthésie générale, sédation profonde ou sous traitement aux soins intensifs. Pendant la résonance magnétique, on a accès à une lecture continue par voie directe ou indirecte des pressions sanguines, des concentrations inspirées et télé-expiratoires des gaz, de la température corporelle, de la fréquence cardiaque, et de l’oxymétrie puisée. On obtient des images diagnostiques de qualité pour les 15 patients monitorés. Le rapport signal/bruit ne diffère pas entre contrôles et patients monitorés. On rapporte les problèmes les plus fréquents et leurs solutions. Cette étude montre qu’on peut procéder en toute sécurité à des examens par résonance magnétique à champ de rayonnement de haute intensité même chez des grands malades.

Contaminated oxygen cylinder.

Potential sources of lay public exposure to stored oxygen supplies include commercial aircraft decompression, mountain climbing at high altitudes, and emergency medical rescue activities. Hospitalized patients are exposed to supplemental oxygen, the most commonly used medical gas, from two sources: pipeline supplied oxygen from a central tank storage system or gas delivered from small portable cylinders. Despite reports of central oxygen supply contamination or misconnections, clinicians usually assume that the gas source is pure (14). Perhaps justifiably, even greater reliance is placed on the purity of the contents of small oxygen cylinders. The standard of care in anesthesia requires monitoring of the inspired oxygen concentration during general anesthesia. In some operating rooms, complex systems, such as the mass spectrophotometer, repetitively analyze the composition of both the inspired and exhaled anesthetic gas mixture. Outside of the operating room, gas monitoring is uncommon, except for an occasional spot check in intensive care units. Monitoring of cylinder supplied gases during transport ventilation of patients is almost nonexistent. This report details the use of what was subsequently recognized to be a contaminated oxygen cylinder during transport ventilation of a hospitalized patient. A 54-year-old, 120-kg, 163-cm woman presented for elective tracheostomy 23 days after hospitalization for an emergency right parietal craniotomy to manage an intracerebral hemorrhage. At the time of admission, she had a blood pressure of 230/110 mm Hg. Past medical history was significant for hypertension complicated by a cerebral vascular accident, morbid obesity, and renal failure.

Postoperative rocuronium reparalysis.

To the Editor: We read with interest the report by Arndt et aLl Recurarization appears to occur frequently and we would like to provide two further reports. Patient #1 sustained a gunshot to her neck causing an intimal flap injury to the carotid artery. During stent placement under conscious sedation an intracranial AV fistula was discovered during arteriography. Subsequently, invasive radiological ablation under general anaesthesia after awake fibreoptic intubation, proceeded uneventfully. After standard neuromuscular reversal and tracheal extubation, the patient was transported awake, sitting up, and talking in the SICU. Fifteen minutes after extubation, she was unable to open her eyes and noted difficulty breathing. Bag mask ventilation was begun. Fibreoptic intubation under controlled ventilation via an LMA proceeded uneventfully. The ulnar nerve response revealed one weak twitch to TOF stimulation. Twenty minutes later, the patient was again able to open her eyes, lift her head and cough. The trachea was extubated uneventfully Patient #2 presented for breast biopsy under general anaesthesia. Anaesthesia was induced with propofol and fentanyl, followed by an intubation dose ofrocuronium (0.6 mg-kg q) and anaesthesia was maintained with nitrous oxide-oxygen-sevoflurane. Vancomycin (1 g) was given preoperatively. Post surgery, normal TOF, sustained tetanus and head lift (> 5sec) was evident after standard reversal. After awake extubation, the patient was transported to PACU. Within 20 min, she became progressively dyspneic and weak as evidenced by depressed ulnar twitch responses. Calcium chloride (1.5 mg.kg -1) followed by 10 mg pyridostigmine and 0.2 mg glycopyrrolate was given with no immediate improvement. Subsequently, the trachea was reintubated after 5 mg midazolam and the lungs were ventilated until spontaneous neuromuscular recovery. Extubation proceeded uneventfully. In summ~y, we describe two cases of rocuronium reparalysis in which neuromuscular recovery was demonstrated prior to PACU arrival. Vancomycininduced neuromuscular potentiation should be given serious consideration when used with rocuronium. 2

Failure of a noninvasive automated blood pressure monitor to detect the blood pressure after repositioning of the patient's arm.

There are obviously controversies about the possible effect of several anesthetics on platelet aggregation, perhaps due to the different technical approaches and interpretations of the results from study to study. Our investigation was in vitro. In no part of our paper do we extrapolate directly to in vivo conditions. Our results only describe a different behavior of propofol in vitro between two types of samples: isolated platelets and whole blood. In whole blood, erythrocytes and/or leukocytes play an important role in platelet function and in its inhibition by drugs. The in vitro effect of propofol is influenced by the nitric oxide-cGMP pathway interaction with platelet-leukocyte (1). For that reason, we think that whole blood aggregometry could demonstrate better than isolated platelets the inhibitory effect of propofol. Even more, we obtained recent in vivo results in whole blood aggregometry in patients who received a bolus of propofol (1). In these patients, platelet function in isolated platelets was not modified statistically, but using whole blood aggregometry, we observed an inhibitory effect 5 min after the propofol bolus (50% effective dose for collagen 0.5 pg/mL before bolus, 1.9 pg/mL after bolus); moreover, plasma nitrites (as indicators of nitric oxide production) were increased after the propofol bolus. In conclusion, our study is the first step of an investigation that requires other consecutive steps to obtain a definitive conclusion.

Pancuronium added to intravenous regional anesthesia: systemic weakness after prolonged tourniquet inflation time.

To the Editor: Neuromuscular blockers (NMBs) may be added to intravenous regional anesthesia (IVRA) to enhance both the motor and sensory blockade.1 , 2Most reports indicated lack of systemic effects with these agents but we encountered a case of weakness upon tourniquet deflation with the use of pancuronium despite a tourniquet inflation time of 89 min. A healthy 41-yr-old, 81 kg man presented for repair of a lacerated right extensor pollicis longus tendon and IVRA was performed with 40 lidocaine ml 0.7% plus 2 mg pancuronium. This quantity of pancuronium was inadvertently administered instead of the 1 mg dose typically used at our institution. The block was performed in the standard manner, with exsanguination of the arm and inflation of a double-cuffed tourniquet to 300 mmHg. The tourniquet was deflated after 89 min. Three minutes later the patient experienced diplopia and was unable to lift his head. Intravenous administration of 2.5 mg neostigmine (with 0.5 mg glycopyrrolate) terminated the diplopia and allowed a sustained head lift for > 5 sec. The apparent systemic release of a substantial quantity of NMB in this case is in contrast to that of local anesthetics, in which one would expect no systemic effects after deflation of a tourniquet which had been inflated for 89 min. The differences probably relate to the lesser extremity tissue binding with NMBs due to their greater ionization and lower lipid solubility. Clinicians who add NMBs to IVRA should be aware of the potential for systemic weakness, even after prolonged tourniquet inflation.