Effect of Altered Arterial Carbon Dioxide Tensions on the Electroencephalogram During Hypothermia

The effect of strictly controlled changes in PaC0₂ on the electro-encephalogram was observed in dogs under stable anaesthesia and moderate systemic hypothermia. Pulmonary ventilation and amounts of carbon dioxide given were regulated to produce: (1) relative hypocapnia, (2) a constant PaCO₂, and (3) relative hypercapnia. Changes in PaCO₂ did not significantly affect coldinduced depression of the electro-encephalogram, thereby negating the prospect that the administration of carbon dioxide may prevent the depression of the electrical activity of the brain which accompanies hypothermia. Inertness of raised PaC0₂ on the electro-encephalogram was demonstrated also in hypothermic patients.

ZUSAMMENFASSUNG

Bei Hunden wurde unter gleichbleibenden Narkosebedingungen und mäßiger allgemeiner Hypothermic die Wirkung genau kontrollierter Veränderungen des arteriellen Kohlensäuredrucks auf das EEG untersucht. Die Lungenventilation und Zugabe von Kohlensäure wurden so reguliert, daß sie 1) eine relative Hypokapnie, 2) ein konstantes PaC0₂ und 3) relative Hyperkapnie erzeugten. Veränderungen des PaC0₂ beeinflußten die k#aUlteinduzierte Dämpfung des Elektroenzephalogramms nicht signifikant. Womit die Vorstellung zu negieren ist, daß die Gabe von Kohlensäure imstande ist, die mit der Hypothermic einhergehende Dämpfung der elektrischen Aktivität des Gehirns zu verhindern. Die Wirkungslosigkeit erhöhter arterieller Kohlensäuredrucke auf das EEG wurde auch bei hypothermen Patienten demonstriert.     

The Effect on the Splanchnic Blood Flow and Cardiac Output of Various Carbon Dioxide Concentrations during Fluroxene (Fluoromar®) Anaesthesia An Animal Study

Seven dogs premedicated with pethidine 10 mg/kg body weight, were anaesthetized with mebumal natrium 25 mg/kg body weight i.v. and gallamoni jodidum 80 mg, together with O₂-N₂O in a ratio of 1 to 1. Thereafter four dogs were constantly hyperventilated and three constantly hypoventilated under stepwise increasing anaesthesia with fluoromar® (= fluroxene), up to 6% inspiratory concentration. A change was made between the groups at this fluoromar concentration, from hyper- to hypoventilation and vice versa, after which the fluoromar concentration was reduced stepwise to 0% inspiratory. During the course of this anaesthesia, the related values for flow, pressure and resistance in the systemic and splanchnic circulations were measured at fluoromar concentrations: 0–1 1/2–3-6-6-3-1 1/2-0%. The relative changes in the systemic circulation during increasing concentrations of fluoromar are independent of hypo- or hypercapnia, while the absolute magnitudes of the measured parameters are strongly dependent on the CO₂ tensions. The hypercapnic dogs had the highest cardiac output, stroke volume and most rapid pulse, as well as the lowest peripheral resistance. The same group of dogs had the lowest liver blood flow and the greatest splanchnic resistance. The mean pressures in the aorta, right atrium and portal vein were not different between the groups. A straight line dependence at 6% fluoromar, was demonstrated between cardiac index and Pa_co2: cardiac index (1-min^-1-m^-2) = 1.22 + 0.23 ± Pa_co2 (kPa), ((cardiac index (1-min^-1-m^-2) = 1.22 + 0.03 ± Pa_co2 (mmHg)), and peripheral resistance and Pa_o2: peripheral resistance (kPa 1^-1 min) = 12.85—0.5 ± Pa_co2 (kPa), ((peripheral resistance (dyn-sec-cm^-5 ± 10^-3) = 7.72-0.04 ± Pa_co2 (mmHg)). The pressure in the portal vein appears to rise and the liver flow to fall with rising carbon dioxide tension, but the relationship is not significant. In the latter half of the investigation only small changes were demonstrated which could be related to the falling concentration of fluoromar. These were slight rises in the mean pressure of the aorta and cardiac frequency, similar for both groups. In addition, a slight rise in the peripheral resistance and splanchnic resistance were observed in the hypocapnic group. No changes were seen in the cardiac output and liver flow in any of the groups during falling fluoromar concentrations. The absolute magnitude of the measured parameters in relation to the CO₂ tension reflects the conditions in the first half of the investigation, but the difference between the groups is less pronounced. This was partly due to the smaller difference in Pa_co2 between the groups in this part of the investigation and partly due to the time and experimental course.     

Arterial Oxygenation during One-lung Ventilation: A Comparison of Enflurane and Isoflurane

Background: Because maintaining arterial oxygenation (PAO2) during one-lung ventilation (OLV) can be a clinical problem, it is useful to be aware of factors that influence PaO2 in this situation and are under the control of the anesthesiologist. It is unknown whether, among the commonly used volatile anesthetic agents, one is associated with higher PaO2 levels. Clinical studies suggest that isoflurane provides superior PaO2 during OLV than does halothane. These have not been compared to enflurane. The authors studied PaO2 and hemodynamics during OLV with 1 MAC enflurane versus 1 MAC isoflurane.

Methods: Twenty-eight adults who had prolonged periods of OLV anesthesia with minimal trauma to the nonventilated lung (thoracoscopic or esophageal surgery) were studied in a crossover design. Patients were randomized to two groups: Group 1 received 1 MAC enflurane in oxygen from induction until after the first 30 min of OLV, then were switched to 1 MAC isoflurane. In group 2, the order of the anesthetics was reversed.

Results: Isoflurane was associated with higher PaO2 values during OLV (P < 0.0001). Mean PaO2 (plus/minus SD) after 30 min OLV isoflurane was 231 (plus/minus 125) mmHg versus 184 (plus/minus 106) mmHg after 30 min OLV enflurane. The difference in Pa sub O2 between the two anesthetics was most marked in the patients with the highest PaO2 during OLV: PaO2 isoflurane - PaO2 enflurane alpha PaO2 isoflurane (r = 0.65, P < 0.001). There were no other significant differences between anesthetic gases in the measured hemodynamic or respiratory variables. In the subgroup of patients with pulmonary artery catheters (n = 7), PaO sub 2 correlated with cardiac output during OLV for both anesthetics (r = 0.81, P < 0.001).     

The Influence of Arterial Carbon Dioxide Tension on the Cerebrovascular Response to Arterial Hypoxia and to Haemodilution

Cerebral blood flow (CBF) measurements and blood gas analyses were performed on anaesthetized and artifically ventilated dogs during arterial hypoxia or haemodilution in different ranges of arterial carbon dioxide tension. Arterial hypoxia as well as haemodilution produced a flow increase in all ranges of ventilation. However, this flow increase was elicited at a cerebrovenous oxygen tension which rose with the arterial carbon dioxide tension, but which tended to be maintained by the flow increase during continued decrease of the arterial oxygen content. On the assumption that the cerebrovenous oxygen tension reflects the oxygen tension of the brain tissue, it is suggested that the arterial carbon dioxide tension influences the ability of the brain tissue to maintain the aerobic metabolism during reduced tissue oxygen tension. This means that tissue hypoxia, in the sense of utilisation of anaerobic metabolism, occurs at a tissue oxygen tension which is lower the lower the arterial carbon dioxide tension is.     

Effects on Humidification and Ventilatory Parameters of Three Single-limb Heated-wired Circuits for Non-invasive Ventilation: A Bench Study

BackgroundThe objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model.MethodsThree SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15 cm H₂O with FiO₂ 0.3 and 1, respectively; and, IPAP of 25 cm H₂O with FiO₂ 0.3 and 1, respectively. EPAP was set at 5 cm H₂O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured.ResultsIn each FiO₂ group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P < .001). Except for RP at FiO₂ 0.3, AH increased significantly in IT and RP groups as IPAP increased (P < .001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO₂ group compared to IT (P < .001).ConclusionsHumidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.     

Avoiding Psychic Adverse Effects during Induction of Neurolept Anaesthesia with Levomepromazine A Double-Blind Study of Levomepromazine and Droperidol

Levomepromazine 0.1 μg/kg or droperidol 0.15 mg/kg for induction of neurolept anaesthesia were compared in a double-blind prospective study of 60 patients undergoing upper abdominal surgery. On the morning after surgery, eight of 30 patients (26.7%) who received droperidol remembered having had unpleasant anxiety, or nightmarish or panicky experiences during induction of anaesthesia, whereas only one of 30 patients (3.3%) receiving levomepromazine experienced such unpleasant adverse effects ( P <0.0l). During anaesthesia, the patients induced with levomepromazine needed somewhat less fentanyl, had somewhat less pain intensity, during the first 3 h after surgery, and they required the first postoperative dose of morphine 1.5 h later than the patients receiving droperidol ( p <0.02). There was no difference in the number of patients receiving naloxone at the end of anaesthesia in the two groups. However, 21 of 30 patients (70%) in the levomepromazine group and only seven of 30 patients (23.3%) in the droperidol group were given physostigmine for arousal at the end of anaesthesia ( p <0.0l). There was no difference between the two groups in the occurrence of postoperative nausea, restlessness, hallucinations, or sedation in the recovery ward. This study shows that levomepromazine is superior to droperidol for induction of neurolept anaesthesia because it gives less psychic adverse effects. more analgesia, and a deeper sedation, which is easily reversed with physostigmine at the end of anaesthesia.     

Effects of Practolol and Metoprolol on QT Interval, Heart Rate and Arterial Pressure during Induction of Anaesthesia

The effects of the selective β₁-adrenergic receptor blocking agents, practolol with intrinsic sympathetic activity (ISA) and metoprolol without ISA, were studied on QT interval, heart rate, arterial pressure and cardiac arrhythmias during the induction of anaesthesia in 142 adults. In the control group, the QT interval was statistically significantly prolonged after thiopental, and the most marked prolongation occurred after suxamethonium. Neither practolol nor metoprolol alone affected the QT interval. Practolol 100 μg/kg i.v., but not 40 or 150 μg/kg i.v., almost completely reduced the prolongation of the QT interval after suxamethonium. In all doses of 20, 30 and 40 μg/kg i.v. metoprolol statistically significantly and dose-dependently reduced the prolongation of the QT interval after thiopental, suxamethonium and laryngoscopy, but the prolongation of the QT interval after intubation still occurred. Practolol and metoprolol alone statistically significantly reduced heart rate, but did not prevent the increase of heart rate after thiopental. The effects on arterial pressure were minimal. Neither practolol nor metoprolol prevented the cardiovascular intubation response. Ventricular ectopic beats after intubation occurred in 20% of the patients in the control group and their incidence ranged from 20 to 27% in the groups pretreated with practolol or metoprolol 20 μg/kg. In the groups pretreated with metoprolol 30 or 40 μg/kg, ventricular ectopic beats occurred in 5% and 8%, respectively. It is concluded that the selective β₁-adrenergic receptor blocking agents practolol with ISA, and especially metoprolol without ISA, reduced the prolongation of the QT interval after suxamethonium. The results suggest that the prolongation of the QT interval after suxamethonium may be mediated by the stimulation of the sympathetic nervous system caused by suxamethonium.     

高频喷射通气（HFJV）气流运输和效应的动物实验研究

犬8条,分油酸组(C_L)和非油酸组(C_N),每组4条。根据正交实验设计表L_9(4~3)分9种状态作HFJV,应用热线呼吸测速仪测定0级气管内的气流速度,并于30min后作动脉血气分析。结果显示,两组在f 15时,吸气和呼气末的气流都能降到零,曲线上出现两个峰,f 60和120时,整个呼吸周期均有气流存在,一个双峰,呼气末速度不能降到零,这有利于气体的对流。V_T·f乘积计算证明f 60、120大于f 15.即高频的对流效应好于常频。然而,血气分析提示,随频率升高,PaCO_2也有升高趋势,特别是C_L组。所以,不能认为对流效应好,通气效应就一定好。对此,作者从气流动力学角度作了阐述,认为临床上应对频率加以限制。     

A Comparative Study of the Haemostatic Properties and Cardiovascular Effects of Adrenaline and Ornipressin in Children during Enflurane Anaesthesia

In a randomised, double-blind trial, haemostatic and cardiovascular effects of ornipressin and adrenaline were compared in 30 children requiring surgery for "bat-ear" deformity. Mean total blood loss was 14.3 ml with ornipressin and 11.7 ml with adrenaline, this difference being insignificant. There was a significant and progressive reduction in mean heart rate in children who received ornipressin. from 134 to 116 bpm (P<0.0.5). and a significant rise from 127 to 134 bpm (P<0.05) with adrenaline. Mean systolic pressure was unaltered by ornipressin but was significantly increased from 97 to 105 mmHg (P<0.05) in children receiving adrenaline. Ornipressin is as effective a haemostatic agent as adrenaline and the rises in heart rate and systolic pressure associated with adrenaline, which are factors known to predispose to the onset of ventricular dysrhythmias, do not occur with ornipressin.     

Effects of Minute Volume Increases on the Rebreathing Characteristics of the Bain Anaesthesia Circuit During Controlled Ventilation

In the course of a study on the carbon dioxide rebreathing characteristics of the Bain anaesthesia circuit, it was noted that raising the minute volume without changing the fresh gas inflow invariably led to increased rebreathing of expired gases. Altering tidal volume and rate in order to reproduce a given minute volume had the same effect on rebreathing. A nomogram constructed to quantitate increases in rebreathing in function of carbon dioxide production per minute, fresh gas flow from the anaesthesia machine, and minute volume is produced. It can be used to assess the amount of fresh gas flow necessary to mantain a steady and inspired gas composition.     

CO2气腹对肿瘤细胞种植与生长的影响

目的　探讨腹腔镜手术中常用的气腹介质CO2 对径路口及腹腔内肿瘤细胞种植及转移的影响。方法　手术前 1h于 30只Wistar大鼠腹腔内注入R15肝癌细胞株 ,并按随机抽样法将大鼠均分为免气腹组、He气腹组和CO2 气腹组 3组 ,实验维持 2h、2 8d后宰杀动物 ,比较各组径路口及腹腔内肿瘤的种植及转移情况。结果　在径路口、肠浆膜层、肠系膜、大网膜和膈肌部位种植的肿瘤重量 :CO2 气腹组分别为 (32 6 .7± 2 30 .3)mg、(6 2 6 .2± 2 15 .9)mg、(476 .2± 2 0 4 .8)mg、(2 5 36 .5± 90 6 .7)mg及 (384 .5± 14 9.9)mg ;He气腹组分别为(2 35 .6± 10 7.3)mg、(414 .2± 14 8.4 )mg、(2 6 1.8± 92 .6 )mg、(16 33.4± 2 4 7.3)mg及 (2 2 0 .0± 5 7.9)mg ;免气腹组分别为 (14 5 .0± 4 2 .4 )mg、(2 2 1.5± 10 8.2 )mg、(2 12 .5± 10 9.6 )mg、(797.5± 335 .9)mg和 113.0mg。在各部位种植的肿瘤重量 ,CO2 气腹组均明显高于He气腹组和免气腹组 ,差异有显著性意义 (P<0 .0 5 ) ;He气腹组均高于免气腹组 ,但差异无显著性意义 (P>0 .0 5 )。结论　CO2 气腹与He气腹及免气腹相比 ,可促进腹腔内肿瘤细胞的种植与生长。     

Arterial Wall Compliance after Diode Laser Assisted Microanastomosis: A Comparative Study with Conventional Manual Microanastomosis on the Rabbit Femoral Artery

. Microvascular anastomosis compliance mismatch is a predictive factor for anastomosis patency rate. We compared the arterial wall compliance of manual and laser-assisted vascular micro-anastomosis. Twelve New Zealand white rabbits were operated with conventional manual microanastomosis (CMMA) on the left femoral artery (10-0 separated stitches) and laser-assisted microanastomosis (LAMA) on the right (diode laser, wavelength 988 nm, power output 500 mW). Diameter and compliance were immediately measured by echotracking with 20 MHz microprobes, on the anastomosis level, as well as 3 mm upstream and 3 mm downstream from the anastomosis. On the LAMA side, diameter decreased downstream from the anastomosis (from 1.94±0.41 to 1.65±0.21 mm; p=0.012), while compliance increased upstream from the anastomosis (from 0.0034±0.001 to 0.0042±0.0012 mm/mm Hg; p=0.0195). There were no significant diameter or compliance change on the CMMA side (p<0.05). It was concluded that diode LAMA creates a transition site at the anastomosis level, increasing compliance mismatch. Paper received 1st June 1999; accepted after revision 17th December 1999.     

Nitrogen Dioxide Production during Mechanical Ventilation with Nitric Oxide in Adults: Effects of Ventilator Internal Volume, Air Versus Nitrogen Dilution, Minute Ventilation, and Inspired Oxygen Fraction

Background: Inhaled nitric oxide (NO) may be useful in the treatment of adult respiratory distress syndrome and other diseases characterized by pulmonary hypertension and hypoxemia. NO is rapidly converted to nitrogen dioxide (NO2) in oxygen (Oxygen2) environments. We hypothesized that in patients whose lungs are mechanically ventilated and in those with a long residence time for NO in the lungs, a clinically important [NO2] may be present. We therefore determined the rate constants for NO conversion in adult mechanical ventilators and in a test lung simulating prolonged intrapulmonary residence of NO.

Methods: NO (800 ppm) was blended with nitrogen (Nitrogen2), delivered to the high-pressure air inlet of a Puritan-Bennett 7200ae or Siemens Servo 900C ventilator, and used to ventilate a test lung. The ventilator settings were varied: minute ventilation (VE) from 5 to 25 l/min, inspired Oxygen2 fraction (FIO2) from 0.24 to 0.87, and [NO] from 10 to 80 ppm. The experiment was then repeated with air instead of Nitrogen2 as the dilution gas. The effect of pulmonary residence time on NO2 production was examined at test lung volumes of 0.5-4.0 l, V with dotE of 5-25 l/min, FIO2 of 0.24-0.87, and [NO] of 10-80 ppm. The inspiratory gas mixture was sampled 20 cm from the Y-piece and from within the test lung. NO and NO sub 2 were measured by chemiluminescence. The rate constant (k) for the conversion of NO to NO2 was determined from the relation 1/[NO]1 1/[NO]0 k x [Oxygen2] x t, where t = residence time.

Results: No NO2 was detected during any trial with V with dot sub E 20 or 25 l/min. With Nitrogen2 dilution and the Puritan- Bennett 7200ae, NO2 (less or equal to 1 ppm) was detected only at a V with dotE of 5 l/min with an FIO2 of 0.87 and [NO] greater or equal to 70 ppm. In contrast, [NO2] values were greater with the Servo 900C ventilator than with the Puritan-Bennett 7200ae at similar settings. When NO was diluted with air, clinically important [NO sub 2] values were measured with both ventilators at high [NO] and FI sub O2. Rate constants were 1.46 x 109 ppm2 *symbol* min sup -1 when NO was mixed with Nitrogen2, 1.17 x 108 ppm sup - 2 *symbol* min sup -1 when NO was blended with air, and 1.44 x 109 ppm sup -2 *symbol* min sup -1 in the test lung.     

腹腔镜CO2气腹对机体免疫功能的影响

多数研究者认为CO2气腹对机体免疫功能有不同程度的影响,其机制一般认为系CO2扩散入细胞、循环系统,引起pH值降低,从而引起一系列免疫、生化功能的变化.另外,气腹高压力状态解除后,引起内脏缺血再灌注损伤,亦是影响内脏生理功能改变的原因之一.     

Treatment of Upper Lip Wrinkles: A Comparison of the 950 μsec Dwell Time Carbon Dioxide Laser to Manual Tumescent Dermabrasion

Background. High-energy pulsed or computer-scanned continuous-wave carbon dioxide (CO₂) laser resurfacing has gained popularity as a wrinkle treatment because of its minimal thermal injury and precise control of tissue vaporization depth. Manual tumescent dermabrasion has also been effective for treating facial wrinkles. This is, to our knowledge, the first study comparing the use of CO₂ laser to manual tumescent dermabrasion for the treatment of wrinkles on the upper lip.
Objective. To compare prospectively the clinical efficacy of the 950 μsec dwell time CO₂ laser to that of manual tumescent dermabrasion in the treatment of upper lip wrinkles.
Methods. Twenty female subjects with moderate to severe upper lip wrinkles were randomly treated with the 950 μsec dwell time CO₂ laser on one side of the upper lip and manual tumescent dermabrasion on the other.
Results . The average upper lip laser-treated wrinkle score (0 = none to 5 = severe) decreased from 4.3 ± 0.2 before treatment to 1.8 ± 0.3 at 6 months after treatment. The average upper lip dermabrasion-treated wrinkle score decreased from 4.4 ± 0.2 to 1.5 ± 0.3. The degree to which the wrinkle score improved after laser treatment compared with that after dermabrasion was not statistically significant ( P = .216).
Conclusion. Manual tumescent dermabrasion and 950 μsec dwell time CO₂ laser resurfacing are equally effective for the treatment of upper lip wrinkles.