Keizo Shibata

Predicting difficult intubation with indirect laryngoscopy

Background It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult. Methods Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity. Results Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01). Conclusions Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.

Ketamine inhibits endotoxin-induced shock in rats

BackgroundCytokines and nitric oxide are believed to participate importantly in the pathogenesis of endotoxin-induced shock. Several investigators have documented that ketamine attenuates production of cytokines and nitric oxide in endotoxemia, but little is known concerning hemodynamic effects of the drug in this state. The objective of the current study was to assess the potential modifying effects of ketamine in endotoxemia. MethodsThe authors randomly assigned 40 rats to one of four equal groups: endotoxin alone, receiving Escherichia coli endotoxin (15 mg/kg, administered intravenously); saline control, receiving saline only; ketamine alone, receiving ketamine (10 mg · kg−1 · h−1, administered intravenously); pretreatment, with ketamine administration initiated before the endotoxin exposure; and posttreatment, with ketamine initiated 2 h after endotoxin. During the 5 h after endotoxin injection, hemodynamics, acid-base status, and plasma concentrations of tumor necrosis factor &agr; and interleukin 6 were assessed in each group. ResultsEndotoxin injection produced progressive hypotension, metabolic acidosis, and a large increase in the plasma cytokine concentrations. This hemodynamic and cytokine responses to endotoxin were completely abolished in the pretreatment group and modestly suppressed in the posttreatment group. In the absence of endotoxin, ketamine did not modify these responses. ConclusionKetamine administration inhibited hypotension, metabolic acidosis, and cytokine responses in rats injected with endotoxin. The results suggest that judicious use of ketamine as an anesthetic agent may offer advantages in endotoxemia.

Effects of lidocaine administration on hemodynamics and cytokine responses to endotoxemia in rabbits.

Objective: To investigate the effects of lidocaine administration on hemodynamics and cytokine concentrations in Escherichia coli endotoxemia in rabbits. Design: Randomized, prospective laboratory study. Setting: University laboratory. Subjects: Thirty‐two Japanese rabbits anesthetized with urethane and ventilated mechanically. Interventions: Animals were randomly assigned to one of four groups: endotoxemic controls (n = 8), receiving intravenous E. coli endotoxin (0.5 mg/kg bolus) via the mesenteric vein; laparotomy controls (n = 8), treated identically to the endotoxemic controls except for the substitution of 0.9% saline for endotoxin; lidocaine controls (n = 8), treated identically to the laparotomy controls with the addition of intravenous lidocaine (3 mg/kg bolus followed by infusion at 2 mg/kg/hr) administered immediately after the injection of 0.9% saline; and lidocaine‐treated rabbits (n = 8), treated identically to the endotoxemic controls with the addition of intravenous lidocaine (3 mg/kg bolus followed by infusion at 2 mg/kg/hr) administered immediately after the injection of endotoxin. Measurements and Main Results: We compared the cardiac output, systemic vascular resistance, blood gases, and plasma cytokine concentrations (tumor necrosis factor, interleukin [IL]‐6, and IL‐8) for each group. After endotoxin injection, the mean arterial pressure, cardiac output, and systemic vascular resistance decreased progressively in the endotoxemic controls. At 4 hrs after injection, all of the variables except the heart rate and central venous pressure were lower in the endotoxemic controls than in the other groups. At 4 hrs after endotoxin injection, both IL‐6 and IL‐8 concentrations increased in all groups. However, the mean concentrations of IL‐6 and IL‐8 in the endotoxemic controls significantly exceeded those in the other groups. No significant differences existed between the laparotomy controls and lidocaine‐treated rabbits. Conclusions: Lidocaine had a profound inhibitory effect on the hemodynamic and cytokine responses to endotoxemia when it was administered immediately after exposure to endotoxin. Our results demonstrate the potential usefulness of lidocaine as an anti‐inflammatory agent in endotoxemia.

Pharmacokinetics of milrinone in patients with congestive heart failure during continuous venovenous hemofiltration.

Objective: To evaluate the pharmocokinetics of intravenous milrinone in patients with severe congestive heart failure during continuous venovenous hemofiltration (CVVH). Design: Prospective study of patients with congestive heart failure admitted to the intensive care unit (ICU). Setting: ICU between September 1997 and August 1999. Patients and methods: Six patients with severe congestive heart failure during CVVH: all patients received a continuous infusion of milrinone of 0.25 μg · kg− 1· min− 1. The hemodynamics and plasma concentration of milrinone were measured before and after the infusion. Pharmacokinetics were analyzed with one-compartment model featuring constant rate infusion. Results: The steady-state concentration (Css) was 845 ± 135 (mean ± SD) ng/ml, and the half-life time (t1/2) was 20.1 ± 3.3 h. Cardiac index and stroke volume index after the infusion of milrinone increased significantly compared with pre-infusion levels. Other hemodynamic parameters did not change significantly. All patients died within 1 month after the injection of milrinone because of severe forms of arrhythmia, such as ventricular tachycardia and ventricular fibrillation. Conclusions: We found that the mean Css and the mean t1/2 of milrinone in subjects during CVVH were much higher and longer than those previously reported for subjects with normal renal function. It is therefore essential to adjust the dose or modify the dosing interval of milrinone during renal replacement therapy for patients with severe congestive heart failure. However, further studies are needed to determine the details of pharmacokinetics of milrinone and therapeutic procedures for patients with severe heart failure during CVVH.

Effects of Epidural Anesthesia on Cardiovascular Response and Survival in Experimental Hemorrhagic Shock in Dogs

The purpose of the present study was to assess the effects of epidural anesthesia on cardiovascular responses and survival in experimental hemorrhagic shock in dogs. Thirty mongrel dogs were randomly assigned to one of three groups on the basis of anesthetic technique: the upper-level group (n = 10), receiving general anesthesia plus upper-level (mainly thoracic region) epidural anesthesia; the lower-level group (n = 10), receiving general anesthesia plus lower-level (mainly lumbar region) epidural anesthesia; and the control group (n = 10), receiving general anesthesia alone. After withdrawal of blood, the changes in mean arterial pressure (40 mmHg) and cardiac index were similar in all groups. In the upper-level group, a lower heart rate and systemic vascular resistance than the control group were maintained throughout in the presence of severe hypotension. A significant difference in survival was seen between the upper-level and control groups over the 100-min observation period as a whole (P less than 0.05 by the Generalized Wilcoxon test), since, at the end of the period, only two of the ten animals in the control group survived, whereas nine of ten in the upper-level group survived (P less than 0.001 by the Kaplan-Meier test). This result demonstrates that, in dogs lightly anesthetized with halothane and nitrous oxide, upper thoracic level epidural anesthesia significantly improves survival in experimental hemorrhagic shock (compared with survival in dogs with lumbar epidural or no epidural anesthesia) when the epidural is performed before hemorrhage and when the mean arterial pressure is constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitivity to vecuronium in seropositive and seronegative patients with myasthenia gravis.

Patients with myasthenia gravis (MG) are hypersensitive to nondepolarizing neuromuscular blocking drugs. Although antibodies to the acetylcholine receptor (AChR) often are observed in MG patients, 10% to 30% of patients do not show an anti-AChR antibody. Little is known about differences in sensitivity to nondepolarizing neuromuscular blocking drugs between MG patients with and without anti-AChR antibody. Hypothesizing that seronegative patients are as sensitive to vecuronium as seropositive patients, we assessed sensitivity in seropositive and seronegative MG patients and in non-MG patients (n = 8 each). During anesthesia with sevoflurane (2.5%) and nitrous oxide (60%) in oxygen, neuromuscular transmission was monitored by measuring the twitch tension of the adductor pollicis muscle with supramaximal stimulation. After baseline measurements, 10 &mgr;g/kg IV dose increments of vecuronium were administered sequentially until blockade exceeded 90%. The degree of blockade and onset time after the initial 10 &mgr;g/kg of vecuronium were assessed, and doses required to exceed 90% blockade were recorded. In addition, effective doses of 50% and 95% for vecuronium were calculated from a single data point. Both types of MG patients showed increased sensitivity to vecuronium compared with non-MG patients.

Neuromuscular monitoring at the orbicularis oculi may overestimate the blockade in myasthenic patients.

BackgroundIn most publications about myasthenia, monitoring neuromuscular blockade during anesthesia is recommended. In healthy patients, the relation of blockade between muscles has been established, but there is little information about the relation in myasthenic patients. Our objective was to investigate whether the relation between the orbicularis oculi and adductor pollicis muscles is the same in healthy patients and myasthenic patients. MethodsAfter anesthesia was induced with 4–6 mg/kg thiopental and 2 &mgr;g/kg fentanyl, followed by 2% sevoflurane and 60% nitrous oxide in oxygen, 10 healthy patients and 10 myasthenic patients received 0.025 and 0.01 mg/kg vecuronium, respectively. Neuromuscular monitoring was performed with use of accelerometry at the orbicularis oculi and the adductor pollicis muscles by stimulating the temporal branch of the facial nerve and the ulnar nerve. ResultsThe relation of blockade between these two muscles was not the same in healthy patients and myasthenic patients: in healthy patients, the maximum neuromuscular blockade with 0.025 mg/kg vecuronium was less in the orbicularis oculi than in the adductor pollicis (median 72%vs. 91%;P < 0.05); in contrast, in myasthenic patients, the blockade with 0.01 mg/kg vecuronium was greater in the orbicularis oculi than in the adductor pollicis (median 96%vs. 62%;P < 0.05). ConclusionNeuromuscular monitoring at the orbicularis oculi may overestimate blockade in myasthenic patients. Extubation must be performed when the muscle most sensitive to neuromuscular blocking agents is recovered. Therefore, neuromuscular monitoring at the orbicularis oculi is recommended to avoid persistent neuromuscular blockade in patients with myasthenia gravis.

Lidocaine attenuates the hypotensive and inflammatory responses to endotoxemia in rabbits

OBJECTIVE To assess the effects of lidocaine on the hemodynamic and inflammatory responses to Escherichia coli endotoxemia in rabbits. DESIGN Prospective, randomized, controlled experimental study. SETTING University laboratory. SUBJECTS Twenty-seven female Japanese rabbits, anesthetized with urethane and ventilated mechanically. INTERVENTIONS Animals were randomly assigned to one of three groups: a) endotoxemic control group (n = 9), receiving intravenous Escherichia coli endotoxin (0.5 mg/kg bolus) via the mesenteric vein; b) laparotomy control group (n = 9), treated identically to the endotoxemic control group, except for substitution of 0.9% saline for endotoxin; and c) lidocaine-treated group (n = 9), treated identically to the endotoxemic controls and additionally, intravenous lidocaine (3 mg/kg bolus, followed by infusion at 2 mg/kg/hr) was administered immediately after endotoxin MEASUREMENTS AND MAIN RESULTS We compared hemodynamics, blood gases, and microscopic findings of lung tissue obtained at necropsy in each group. Laparotomy alone had a minimal effect on the parameters and findings. Endotoxin injection decreased mean systolic arterial pressure from 135 +/- 6 (SD) to 95 +/- 25 mm Hg (p < .05) and increased the mean base deficit from -1.2 +/- 1.8 to -14.4 +/- 4.2 mmol/L (p < .05), and caused the infiltration of neutrophils into the lungs. Lidocaine administration abolished the hypotension and attenuated the increase the base deficit to -9.5 +/- 2.1 mmol/L (p < .05) and the cellular infiltration in comparison with endotoxemic controls. CONCLUSIONS Lidocaine attenuated the hemodynamic and inflammatory responses to endotoxemia in rabbits. Findings suggest that lidocaine administration may prevent the development of hypotension and metabolic acidosis during endotoxemia.

Extensive chemical burns from toluene

A 22-year-old man with heavy, generalized exposure to a toluene-based paint developed extensive chemical burns on approximately 71% of his total body surface area followed by acute renal failure and disseminated intravascular coagulation that led to death. Although the skin damage initially appeared mild, it was followed by blistering, extensive necrosis, and massive loss of fluid. Histological examination of the skin showed findings similar to those observed in second-degree thermal burns. Although the most common toxic effects of toluene are depression of central nervous system activity, irritation of mucous membranes, and hepatic or renal dysfunctions, emergency physicians should be aware of the risk of skin toxicity. Therefore, it is important to irrigate the exposed skin immediately and vigorously.

Epidural Anesthesia Modifies the Cardiovascular Response to Marked Hypercapnia in Dogs

Background:There is little information on the cardiovascular response to marked hypercapnia during epidural anesthesia (EA). Our objective was to assess the potential modifying effects of various levels of EA on this response. Methods:We randomly assigned 48 mongrel dogs anesthetized with halothane (0.5%) to one of four groups: control (n=12), receiving general anesthesia alone; lumbar (n=12), also receiving lumbar EA; thoracic (n=12), also receiving thoracic EA; and thoracolumbar (n=12), also receiving thoracolumbar EA. During marked hypercapnia (mean arterial CO2 tension > 90 mmHg for 15 min), we measured hemodynamic parameters and plasma catecholamine concentrations in each group. Results:In the control condition, marked hypercapnia increased cardiac output, reduced systemic vascular resistance, modestly increased mean arterial blood pressure. Lumbar EA abolished the increase in cardiac output, and thoracic and thoracolumbar EA caused CO2 to depress the cardiac output and the mean arterial blood pressure during marked hypercapnia. The physiologic increase in circulating catecholamines during marked hypercapnia was abolished only in the thoracolumbar EA group. Conclusions:We conclude that sympathetic blockade by EA modifies the cardiovascular response to marked hypercapnia in dogs. Although modest hypoventilation is often effective in treating hypotension during general anesthesia, the current results suggest that hypoventilation may be detrimental during the combination of EA and general anesthesia.