Intraoperative awake tracheal intubation using the Airway Scope™ in caesarean section.

The Airway Scope™, a novel videolaryngoscope used for tracheal intubation, is minimally invasive and can be used in conscious patients. The parturient with a potentially difficult airway should sometimes be intubated while awake, without anaesthesia or neuromuscular block. Two pregnant women who experienced massive postpartum haemorrhage during caesarean section underwent unscheduled intraoperative tracheal intubation using the Airway Scope. They were conscious and were intubated with minimal local anaesthesia so as to prevent cardiovascular compromise. We believe the Airway Scope is useful for anaesthetic procedures in the parturient who has haemodynamic instability.

Involvement of glucocorticoid receptor on hyperpyrexia induced by methamphetamine administration.

UNLABELLED: We have investigated the involvement of glucocorticoid on methamphetamine (MA) induced hyperpyrexia using a bio-telemetric system. A significant level of hyperpyrexia was observed in MA administered rats. In contrast, increase of body temperature was suppressed by adrenalectomy or by the administration of RU-486, an antagonist of the glucocorticoid receptor. These data suggest that the glucocorticoid receptor may be involved in hyperpyrexia induced by MA. KEYWORDS: methamphetamine - hyperpyrexia - glucocorticoid - corticosterone.

Crystalloid infusion rate during fluid resuscitation from acute haemorrhage.

BACKGROUND: Information is lacking concerning optimal infusion rates of crystalloid during resuscitation from acute haemorrhage. In this study, a mathematical model was used to predict infusion volume of crystalloid needed to restore and maintain blood volume after acute haemorrhage. METHODS: The scenario was a haemorrhage of 15 ml kg(-1) over 30 min in a 70 kg man. A bolus of crystalloid was administered at a rate of 40, 60, 80, 100, or 120 ml kg(-1) h(-1) until blood volume was restored. Fluid infusion rate needed to maintain blood volume for a further 1 h was computed. RESULTS: Blood volume was restored earlier at high bolus infusion rates compared with low bolus infusion rates (6 min at 120 ml kg(-1) h(-1) vs 63 min at 40 ml kg(-1) h(-1)). Fluid infusion rates for blood volume maintenance approached 33 ml kg(-1) h(-1) irrespective of bolus infusion rates. The restoration fluid volume at 40 ml kg(-1) h(-1) was 2.9 litre, three times that at 80-120 ml kg(-1) h(-1). The maintenance fluid volume at 80-120 ml kg(-1) h(-1) was 2.9 litre, 0.6 litre more than that at 40 ml kg(-1) h(-1). During the blood volume maintenance, the interstitial volume increased to 3.8 litre above normal at 40 ml kg(-1) h(-1) and to 2.5 litre at 80-120 ml kg(-1) h(-1). CONCLUSIONS: Bolus crystalloid infusion exceeding 80 ml kg(-1) h(-1) may not increase effectiveness of fluid resuscitation. Crystalloid resuscitation for more than 2 h may be detrimental in view of an excessive net fluid retention.

Effect of continuous infusion of prostaglandin E1 on hepatic blood flow.

STUDY OBJECTIVE: To evaluate the effects of an intravenous infusion of prostaglandin E1 (PGE1) on hepatic blood flow. DESIGN: Prospective clinical study. SETTING: University-affiliated hospital. PATIENTS: 16 ASA physical status I and II surgical patients who were scheduled for abdominal surgery. INTERVENTIONS: Patients were anesthetized with 1% sevoflurane and 66% nitrous oxide. PGE1 0.05 mg/kg/min or PGE1 0.10 mg/kg/min was continuously infused, followed by an infusion of 1000 mL Ringer's acetate solution. MEASUREMENTS: The hemodynamic effect of PGE1 was examined using pulse dye densitometry (PDD). A nose probe for PDD was used, and 10 mg indocyanine green (ICG) in 2 mL distilled water was bolus-infused into a central venous catheter for each measurement. Cardiac output (CO), circulating blood volume (CBV), and plasma dye clearance rate (K) were monitored from the dye-densitogram. Hepatic blood flow was estimated using the K and CBV values. MAIN RESULTS: PGE1 did not increase CBV or CO. Even adding a 1000 mL crystalloid infusion did not expand CBV, whereas mean arterial pressure (MAP) significantly decreased from 91.1 +/- 16.5 mmHg to 84.8 +/- 13.5 mmHg (PGE1 0.05 microg/kg/min) and 80.6 +/- 14.4 mmHg (PGE1 0.10 microg/kg/min ) (p < 0.01 compared with control value), then to 72.0 +/- 6.5 mmHg (PGE1 0.10 microg/kg/min + 1000 mL Ringer's acetate) (p < 0.01 compared with control value). Hepatic blood flow changes were 1.46 +/- 0.60 L/min (control), 1.48 +/- 0.45 L/min (PGE1 0.05 microg/kg/min), 1.14 +/- 0.35 L/min (PGE1 0.10 microg/kg/min), and 1.15 +/- 0.19 L/min (PGE1 0.10 microg/kg/min + 1000 mL Ringer's acetate) (no significant difference, p < 0.05). Hepatic blood flow and K values did not statistically significantly differ at each condition. CONCLUSIONS: PGE1 does not affect blood volume shift, CO, or hepatic blood flow.

Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 1: Incorporation of fat tissue into cell suspension model in the arm.

The non-invasive characterisation of cell pathophysiology is clinically important. A cell suspension model is applied to derive the extracellular fluid (ECF) volume fraction and the equivalent dielectric constant of the cell membrane epsilon m from the dielectric properties of human arms. Frequency-dependent dielectric constants and electrical conductivities of arms are obtained from 35 surgical patients over a frequency range of 5-1000 kHz. The cell suspension model is applied to fit the data using a complex non-linear least-squares method. The arms show typical dielectric dispersions, although the cell suspension model yields a poor fitting in dielectric constants at lower frequencies and electrical conductivities at higher frequencies. In contrast, a new cell suspension model, taking into account the fat tissue component, remarkably improves the overall fitting performance, allowing estimation of the volume fractions of ECF (0.34 +/- 0.05) and fat tissue (0.16 +/- 0.04) and the equivalent epsilon m (23 +/- 9). The resulting estimates of the volume fraction of fat tissue are in good correlation with arm skinfold thickness (fat volume fraction of arm = 2.42 x 10(-3) x arm skinfold thickness (mm) + 0.099, R = 0.756, p < 0.0001). Therefore it is concluded that the newly derived cell suspension model is well suited for the description of the dielectric properties of human tissues and thus the derivation of the ECF volume fraction and equivalent epsilon m.

Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 2: A preliminary study for tracking the progression of surgical tissue injury.

A study is conducted to determine whether the extracellular fluid (ECF) volume fraction and equivalent dielectric constant of the cell membrane epsilon m, derived from the dielectric properties of the human body can track the progression of surgical tissue injury. Frequency-dependent dielectric constants and electrical conductivities of body segments are obtained at surgical (trunk) and non-surgical sites (arm and leg) from five patients who have undergone oesophageal resections, before and at the end of surgery and on the day after the operation. The ECF volume fraction and the equivalent epsilon m of body segments are estimated by fitting the dielectric data for body segments to the cell suspension model incorporating fat tissue, and their time-course changes are compared between body segments. By the day after the operation, the estimated ECF volume fraction has increased in all body segments compared with that before surgery, by 0.13 in the arm, 0.16 in the trunk and 0.14 in the leg (p < 0.05), indicating postoperative fluid accumulation in the extracellular space. In contrast, the estimated equivalent epsilon m shows a different time course between body segments on the day after the operation, characterised by a higher change ratio of epsilon m of the trunk (1.34 +/- 0.66, p < 0.05), from that of the arm (0.66 +/- 0.34) and leg (0.61 +/- 0.11). The results suggest that the equivalent epsilon m of a body segment at a surgical site can track pathophysiological cell changes following surgical tissue injury.

[Measurements of extracellular water volume by bioelectrical impedance analysis during perioperative period of esophageal resection].

Segmental bioelectrical impedance analysis (BIA) was conducted in five patients who underwent esophageal resections. Resistance values fitted at zero frequency (R0) in each body segment (arm, trunk and leg) were determined before the induction of anesthesia, at the end of surgery and on the second or third postoperative day. Extracellular water volume (ECW) in each body segment was estimated using the equation derived from the cell suspension theory. ECW in whole body was obtained from the sum of each body segment. R0 in trunk and leg significantly decreased at the end of surgery compared to the values before the induction of anesthesia (P < 0.05). The change ratio of R0 in trunk before the induction of anesthesia was significantly lower at the end of surgery than that in arm (P < 0.05), resulting from the most striking fluid accumulation in the trunk. Postoperatively, R0 in all body segments, however, appeared to decrease similarly compared to the values before the induction of anesthesia, suggesting the redistribution phenomena of extracellular water among body segments. The correlation (r = 0.90, P < 0.001) and good agreement [bias = 0.01 (L)] between net fluid balances and estimates of ECW changes in whole body suggest that BIA allows close monitoring of tissue hydration during perioperative period by providing estimates of ECW in body segments.

Proton nuclear magnetic resonance spectroscopy of urine for rapid multicomponent analysis of intraoperative cellular metabolites.

We serially measured the proton nuclear magnetic resonance spectra of the urine of intraoperative patients over time to assess their potential use for rapid multicomponent analysis of cellular metabolites. Within a few minutes, the spectra provided signals of many low molecular weight urinary metabolites, including amino acids, ketone bodies, lactate, and glucose. The proton magnetic resonance spectra of the urine of most of the intraoperative patients showed large increases in urinary excretion of alanine, ketone bodies, and lactate and/or glucose, confirming alterations in energy substrate-endocrine relationships during the perioperative period. These metabolic changes appeared to be roughly proportional to the degree of surgical stress, but they were not consistent among patients who underwent the same operation. The study suggests that routine intraoperative metabolic monitoring is necessary to prevent critical metabolic disorders and that proton nuclear magnetic resonance spectroscopy of urine may meet this need by allowing rapid multicomponent analysis of cellular metabolites.

Segmental bioelectrical impedance analysis improves the prediction for extracellular water volume changes during abdominal surgery.

OBJECTIVE: To determine whether the segmental multifrequency bioelectrical impedance analysis may improve the prediction for intraoperative changes in extracellular water volume (deltaECW) compared with whole body multifrequency bioelectrical impedance analysis in abdominal surgical patients. DESIGN: Prospective, consecutive sample. SETTING: Surgical operative patients in a university-affiliated city hospital. PATIENTS: Thirty patients who underwent elective gastrointestinal surgery. INTERVENTIONS: Multifrequency bioelectrical impedance analysis was conducted preoperatively (before the induction of anesthesia) and postoperatively (after recovery from anesthesia). Resistance values fitted at zero frequency (R0) in the whole body and in each body segment (arm, trunk, and leg) were determined by performing nonlinear curve-fitting and subsequent extrapolation. DeltaECW values were estimated from the whole body resistance between wrist and ankle using two different prediction formulas. In segmental multifrequency bioelectrical impedance analysis, however, ECW was obtained as the sum of each body segment (arms, trunk, and legs) using the equation newly derived from the cell suspension theory. DeltaECW estimated from both measurements were compared with net fluid balances during surgery. MEASUREMENTS AND MAIN RESULTS: R0 in whole body and all body segments significantly decreased after surgery (p < .0001). The most striking decrease in post/preoperative ratios was found in the R0 in the trunk. The post/preoperative ratio of the R0 value in the trunk was significantly lower than the post/preoperative ratio of the R0 value in the leg (p = .0007). DeltaECW from segmental multifrequency bioelectrical impedance analysis was similar to net fluid balance (r2 = .80, bias = -0.03 L), whereas whole body multifrequency bioelectrical impedance analysis resulted in considerable underestimations of deltaECW (r2 = .50, .51, bias = 0.95, 0.53 L). CONCLUSIONS: The difference in the prediction of deltaECW between whole body and segmental multifrequency bioelectrical impedance analysis may be explained by the significant decrease in the resistance of the trunk, which contributed only minimally to the whole body resistance. Segmental multifrequency bioelectrical impedance analysis provides a better approach to predict ECW changes in critically ill patients with nonuniform fluid distribution.

An apnea monitor using a rapid-response hygrometer.

OBJECTIVE: The aim of this study was to detect cyclic changes in the relative humidity (RH) occurring with spontaneous respiration using a rapid-response hygrometer, and to evaluate its potential applicability as an apnea monitor in nonintubated subjects. METHODS: Respiratory monitoring using a rapid-response hygrometer was performed in spontaneously breathing, nonintubated subjects. Changes in RH during spontaneous breathing were measured in adult volunteers, breathing room air and nonintubated infants who underwent cardiac catheterization under intravenous anesthesia. The detection of apnea by the hygrometer was assessed in the adult patients during the induction of anesthesia and those undergoing minor gynecologic surgery under epidural anesthesia. The hygrometric sensor was positioned in front of the nostril; a simultaneous recording of CO2 was obtained from nasal cannulas by a sidestream capnograph. Each waveform was collected and acquired by a PC-based computer, and data were analyzed off-line. RESULTS: The hygrometer showed a rapid response to the cyclic changes in RH during spontaneous respiration and could identify respiratory phases of tachypnea as high as 60 breaths per minute in infants. RH rapidly increased to 80% with a plateau on expiration and decreased to 40% on inspiration. These phasic changes, consisting of three distinct phases, expiratory upstroke, plateau and inspiratory downslope, preceded the corresponding capnographic changes by nearly two seconds. Expiratory increase in RH appeared to be influenced by the respiratory flow rate as well as the response time of the equipment. As respiration was depressed due to airway obstruction, the magnitude of RH gradually decreased and then disappeared at the time of apnea. CONCLUSIONS: The hygrometer could detect cyclic changes in RH during spontaneous respiration. Apnea was immediately detected by the decreases in the magnitude of RH. The results demonstrate the potential usefulness of a rapid-response hygrometer for monitoring respiratory rate and early detection of apnea.

Proton NMR spectroscopic studies of serum as an aid to perioperative cellular metabolic monitoring.

Perioperative concentration changes of cellular metabolites in serum were studied by proton NMR spectroscopy in four cancer patients who underwent tumorectomies under general anesthesia. In proton NMR spectra of serum, the resonances assignable to fatty acid in lipoprotein, lactate, alanine, glucose, glycoprotein and other metabolites were observed. The concentrations of fatty acid and alanine did not show significant changes during the operations compared with those in healthy volunteers. The concentrations of lactate, glucose and glycoprotein increased during the operations above the concentration ranges in the control subjects. The time-course of concentration change for lactate, glucose and glycoprotein was roughly classified into two patterns: i) the maximums of lactate and glucose concentration were observed in the latter halves or at the ends of the operations; ii) the maximums of glycoprotein concentrations were observed three hours after the incision, regardless of the operative time. The results showed cellular metabolic changes became larger as the operations proceeded responding to surgical stress. Prompt cellular metabolic monitoring is indispensable for the screening of cellular metabolic disorders caused by excessive surgical stress and proton NMR spectroscopy can be a new tool for monitoring perioperative cellular metabolism.

[The effects of H2 blockers on gastric flora and sputum culture].

Gastric juice and sputum of 12 patients, who had entered the intensive care unit postoperatively and received respiratory management, were examined for bacteria and their relationship with gastric pH was investigated. Gastric bacteria were detected in only 3 specimens out of 14 (21.4%) when the pH was under 3.5, and when the pH was above 3.5, gastric bacteria were detected in 33 specimens out of 35 (94.3%). Proliferation of gastric flora was observed as the pH increased. In 7 cases, Gram-negative bacilli (important etiologically as a cause of pneumonia) were detected. Gram-negative bacilli were also detected in sputum culture and these were found to be of the same bacteria type as those found in the gastric juice. However, no evident cases of pneumonia were observed, and proliferation of gastric bacteria did not increase the incidence of postoperative pneumonia.

Structure-selective anesthetic action of steroids: anesthetic potency and effects on lipid and protein.

Alphaxalone was a clinically used steroid anesthetic. Its analog delta 16-alphaxalone is nonanesthetic. The only difference between the two is the presence of a double bond at the hydrophobic end of the delta 16-alphaxalone molecule. This study determined the anesthetic potency of alphaxalone and delta 16-alphaxalone in goldfish and compared it with their effects on dipalmitoylphosphatidylcholine (DPPC) membranes and an alpha-helix polypeptide, poly(L-lysine). The goldfish EC50 values were: alphaxalone 5 mumol/L and delta 16-alphaxalone 80 mumol/L. Because these steroids are insoluble to water, the bulk of the steroid in water is absorbed by the fish. Larger containers hold more steroids than smaller containers at the same steroid concentrations. Then, EC50 values vary according to the size of the container. By assuming that the total amount of steroids in the container is distributed into the fish, the EC50 values expressed by the concentration in the fish body become 1.9 mmol/L for alphaxalone, and 30.5 mmol/L for delta 16-alphaxalone. A monoamino acid peptide, poly(L-lysine), can be formed into random-coil, alpha-helix, or beta-sheet. Addition of 0.07 mmol/L alphaxalone to the alpha-helix poly(L-lysine) partially transformed it to a beta-sheet structure. An equivalent change was observed with 3.0 mmol/L delta 16-alphaxalone. These values translate into 3.5 mmol/L for alphaxalone and 0.15 mol/L for delta 16-alphaxalone, when expressed by the concentration in the peptide. The change from alpha-helix to beta-sheet is accompanied by dehydration of the surface of poly(L-lysine). The steroids decreased the phase-transition temperature of DPPC membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of enflurane on human somatosensory evoked potentials: differences between specific and nonspecific responses].

The effect of enflurane on somatosensory evoked potentials (SEP) was investigated in nine gynecological patients under nitrous oxide-enflurane anesthesia. SEPs were obtained from electrodes placed on the scalp C4 and earlobes by median nerve stimulation contralateral to the recording site. SEPs taken in a control study without enflurane consisted of six components; P12, N17, P23, N31, P50, and N65. Components N17, P23, N31, and P50, thought to be specific SEP responses, showed a dose-dependent increase in latencies under enflurane while P12, the initial SEP components, did not show any significant changes throughout the experiment. The longer the latency for a given response component, the greater was the increase in latency seen under enflurane anesthesia. On the other hand, N65, assumed to be a nonspecific SEP response, was completely lost with inhalation of 0.5 MAC or more of enflurane. However, the peak-to-peak amplitude between P23 and N31 was enhanced dose-dependently with enflurane up to 1.5 MAC. These results suggest that, at clinically effective doses, enflurane may inhibit nonspecific projection pathways while enhancing the primary cortical sensory area, and this enhancement may be responsible for provoking convulsive seizures under enflurane anesthesia.

[The anesthetic effects of steroids and their actions on the properties of model membrane].

The action of anesthetic steroid on the GABAA receptor in the postsynaptic membrane has been suggested as a mechanism of steroid anesthesia. Alphaxalone, the main component of althesin, is a strong anesthetic, whereas its analogue, delta 16-alphaxalone is not. The only structural difference between the two is a presence of the double bond in the D ring of delta 16-alphaxalone. The effects of these steroids on the model membrane structure and the hydrogen bonding between lipid membrane and water were examined by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) and compared with their anesthetic potencies in goldfish. Alphaxalone decreased the phase-transition temperature from the solid-gel to the liquid-crystal state of DPPC liposome. FTIR showed that alphaxalone molecules released the bound water molecules in the lipid-water interface of D2O-in-CCl4 reversed micelles. delta 16-alphaxalone in high concentration was also an anesthetic in goldfish. It also showed a weak effect on the phase-transition temperature and the hydrogen bond breaking activity. These changes in the membrane properties correlated to the anesthetic potency. These results suggest that anesthetic potency of steroids is related to their action in destabilizing the structures of the water molecules in the macromolecule-water interface and the macromolecules.

The alpha-helix to beta-sheet transition in poly(L-lysine): effects of anesthetics and high pressure.

Poly(L-lysine) exists in a random-coil formation at a low pH, alpha-helix at a pH above 10.6, and transforms into beta-sheet when the alpha-helix polylysine is heated. Each conformation is clearly distinguishable in the amide-I band of the infrared spectrum. The thermotropic alpha-to-beta transition was studied by using differential scanning calorimetry. At pH 10.6, the transition temperature was 43.5 degrees C and the transition enthalpy was 170 cal/mol residue. At pH 11.85, the measurements were 36.7 degrees C and 910 cal/mol residue, respectively. Volatile anesthetics (chloroform, halothane, isoflurane and enflurane) partially transformed alpha-helix polylysine into beta-sheet. The transformation was reversed by the application of hydrostatic pressure in the range of 100-350 atm. Apparently, the alpha-to-beta transition was induced by anesthetics through partial dehydration of the peptide side-chains (beta-sheet surface is less hydrated than alpha-helix). High pressure reversed this process by re-hydrating the peptide. Because the membrane spanning domains of channel and receptor proteins are predominantly in the alpha-helix conformation, anesthetics may suppress the activity of excitable cells by transforming them into a less than optimal structure for electrogenic ion transport and neurotransmission. Proteins and lipid membranes maintain their structural integrity by interaction with water. That which attenuates the interaction will destabilize the structure. These data suggest that anesthetics alter macromolecular conformations essentially by a solvent effect, thereby destroying the solvation water shell surrounding macromolecules.

Effect of inhalation anesthetics on swimming activity of artemia salina.

The swimming movement of artemia salina in the artificial sea water was measured by using the video camera system in the absence and presence of anesthetics, i.e. enflurane, halothane, and isoflurane. The movement of artemia looked random at a glance but the obtained distribution curve for the swimming speed was skewed toward the high speed side somewhat resembling a Maxwellian distribution curve seen in the statistics of ideal gases. When anesthetic were added, the distribution curve became sharpened and shifted to the low speed side, which is similar to a behavior of ideal gases when they are cooled down. The mean swimming-speed was decreased eventually leading to an irreversible death with increasing the anesthetic dose. The activity was analyzed by using the hydrodynamic equation. The ED(50), which is a dose that causes a 50% reduction in the activity, of all anesthetics used in this study was quite similar to the MAC values for human. It was also suggested that an interaction between anesthetics and artemia was highly cooperative since the larger Hill coefficients were obtained for all three anesthetics used.

A solid-solution theory of anesthetic interaction with lipid membranes: temperature span of the main phase transition.

Anesthetics (or any other small additives) depress the temperature of the main phase transition of phospholipid bilayers. Certain anesthetics widen the temperature span of the transition, whereas others do not. The widening in a first-order phase transition is intriguing. In this report, the effects of additive molecules on the temperature and its span were explained by the solid-solution theory. By assuming coexistence of the liquid-crystal and solid-gel phases of lipid membranes at phase transition, the phase boundary is determined from the distribution of anesthetic molecules between the liquid-crystal membrane versus water and between the solid-gel membrane versus water. The theory shows that when the lipid concentration is large or when the lipid solubility of the drug is large, the width of the transition temperature increases, and vice versa. Highly lipid-soluble molecules, such as long-chain alkanols and volatile anesthetics, increase the width of the transition temperature when the lipid:water ratio is large, whereas highly water-soluble molecules, such as methanol and ethanol, do not. The aqueous phase serves as the reservoir for anesthetics. Depletion of the additive molecules from the aqueous phase is the cause of the widening. When the reservoir capacity is large, the temperature width does not increase. The theory also predicts asymmetry of the specific heat profile at the transition.