Weaning with end-tidal CO2 and pulse oximetry

Study Objective: To determine whether continuous measurement of arterial oxyhemoglobin saturation (SpO₂) and end-tidal carbon dioxide (P_ETCO₂) can be used to wean patients safely and efficiently from postoperative mechanical ventilation after cardiac surgery.

Design: Prospective study comparing SpO₂ and P_ETCO₂ to calculated arterial oxygen saturation (SaO₂ and arterial carbon dioxide tension (PaCO₂) obtained from blood gas analysis.

Setting: Cardiac surgical intensive care unit at a university-affiliated hospital.

Patients: Ten patients requiring elective coronary artery bypass grafting (CABG) were studied in the postoperative period during weaning from mechanical ventilation.

Interventions: Continuous monitoring of SpO₂ and P_ETCO₂ was used to wean patients from mechanical ventilation.

Measurements and Main Results: The patients were weaned from mechanical ventilation in an average time of 6.5 ± 1.5 hours (mean ± SD). A plot of SaO₂ versus SpO₂ indicated a high correlation (r = 0.84) with sensitivity (100%) for hypoxemia (SaO₂ less than 90%). P_ETCO₂ was a good indicator of PaCO₂ (r = 0.76); its sensitivity to detect hypercarbia (PaCO₂ less than 45 mmHg) was 95%. The gradient between SpO₂ and SaO₂ was not significantly affected by the weaning process, but the PaCO₂---P_ETCO₂ gradient decreased significantly as the ventilator rate was decreased (p < 0.001). The weaning process was discontinued on four separate occasions because of metabolic acidosis. Ninety-five percent of arterial blood samples confirmed the weaning recommendations based on the continuous monitoring of SpO₂ and P_ETCO₂.

Conclusions: Continuous monitoring of SpO₂ and P_ETCO₂ can be used to wean patients safely and effectively after CABG when adjustment of minute ventilation compensates for an increased PaCO₂---P_ETCO₂ gradient during controlled ventilation.     

Lack of effect of CO2 on cerebral arterial diameter in man

Study Objective: To establish the quantitatve effects on the diameter of cerebral arteries following controlled changes in arterial carbon dioxide tension (PaCO₂₎.

Design: Nonrandomized interventional study.

Setting: Angiography suite of a tertiary referral hospital.

Patients: 12 anesthetized patients suffering from a cerebral arteriovenous malformation undergoing endovascular treatment.

Intervention: Induced hypocapnia by hyperventilation and induced graded hypercapnia by the administration of carbon dioxide to the anesthetized patient’s breathing circuit.

Measurements and Main Results: A digital angiography computer was used to make computerized measurements and calculations of the diameter of deep and small cortical arteries outside the vascular territory of cerebral arteriovenous malformations following controlled and standardized changes in PaCO₂. Cardiovascular parameters were simultaneously measured and cardiac output (CO) calculated. No statistically significant changes in the diameter of cerebral arteries down to a size of 0.57 mm, which was the smallest artery studied, could be observed following changes in PaCO₂ in the range between 28 ± 4 mmHg and 74 ± 4 mmHg. However, there was a 64 % change in cardiac index following the above change in PaCO₂.

Conclusion: Deep cortical cerebral arteries down to a diameter of 0.57 mm seem to act merely as conductance vessels. The observed dramatic increase in CO following an increase in PaCO₂ may offer an explanation for the changes in cerebral blood flow and cerebral flow velocity recorded by others and usually attributed to cerebral vasodilatation, which we were unable to demonstrate in this study.     

Pre- and postoperative exercise capacity associated with hemodynamics in adult patients with atrial septal defect: A retrospective study

Objective: This study evaluated the pre- and postoperative exercise capacity in adult patients with atrial septal defect (ASD) associated with hemodynamic variables. Methods: Adults (70) with ASD underwent symptom-limited exercise tests. Peak O₂ uptake (Peak VO₂) and % peak VO₂, that is the percentage of predicted value, were measured. These patients were divided into three groups according to pulmonary-to-systemic flow ratio (Qp/Qs) and systolic pulmonary arterial pressure (PAs); Group A: Qp/Qs3, PAs50 mm Hg, Group B: Qp/Qs>3, any PAs, Group C: Qp/Qs3, PAs>50 mm Hg. Exercise test was repeated in 22 patients after surgical closure of ASD (mean 4.6±2.0 months). Results: Peak VO₂ was significantly lower in group B (P<0.01) and group C (P<0.01) than in group A (19.3±5.7, 17.6±3.6, 27.6±6.3 ml/min/kg, respectively). In patients except those in group C, there were a weak negative correlation between PAs and % peak VO₂ (r=0.61) and a significant negative correlation between Qp/Qs and % peak VO₂ (r=0.86). Postoperative peak VO₂ increased significantly in group A (27.2±5.1–31.1±5.1 ml/min/kg, P<0.05) and group B (16.7±3.3–21.5±2.1 ml/min/kg, P<0.01). However, there was no significant difference between pre- and postoperafive peak VO₂ in group C (16.8±1.3–17.8±2.8 ml/min/kg, NS). Conclusions: In ASD patients except those with small or moderate left-to-right shunt and high pulmonary arterial pressure, there was a significant negative correlafion between Qp/Qs and peak VO₂ corrected by age and gender. Patients with large left-to-right shunt and/or high pulmonary arterial pressure had reduced exercise capacity. However, exercise capacity in patients with large left-to-right shunt increased after closure of ASD regardless of whether they had high pulmonary arterial pressure.     

Effect of low fresh gas flow rates on inspired gas composition in a circle absorber system

Study Objective: To determine the effects of fresh gas f ow on inspired gas composition during low flow anesthesia.

Design: Randomized trial with 2-hour observation periods in patients assigned to one of three groups.

Setting: Inpatient surgery clinic at a medical center.

Patients: Thirty-six patients undergoing abdominal surgery with low flow anesthesia. Interventions: Fresh gas flow was given at a starting rate of 5 L/min for 6 minutes. Thereafter, the fresh gas flow setting was nitrous oxide (N₂O) 1 L/min and oxygen (O₂) 0.6 L/min (Group 1), N₂O 0.5 L/min and O₂ 0.5 L/min (Group 2), and with a moderate surplus of N₂O and O₂ with respect to the patient's O₂ consumption (Group 3).

Measurements and Main Results: The inspired O₂ concentration (FIO₂) was measured using a paramagnetic technique, and N₂O levels were measured with infrared sensors; the inspired nitrogen concentration (FIN₂) was calculated by the following formula: (FIN₂) = 1 - FIO₂ - FIN₂O, where FIN₂O is the inspired N₂O concentration. After 1 hour of anesthesia, FIO₂ was significantly lower in Group 1 than in Groups 2 and 3 (p < 0.01), and FIN₂ was significantly higher in Groups 2 and 3 than in Group 1 (p < 0.01). After 2 hours of anesthesia, (FIN₂) returned to normal in Group 2 but continued to increase in Group 3. FIN₂O was close to 0.7% only in Group 1.

Conclusions: The same initial period of denitrogenation is not adequate to denitrogenate the circle system in all cases. The lower the fresh gas flow, the longer the initial period of denitrogenation should be. Various levels of fresh gas flow for low-flow anesthesia have been suggested, but none guarantees adequate control of inspired gas composition unless f owmeters are continuously adjusted.     

心肺转流下冠状动脉搭桥术呼气末二氧化碳分压与心输出量变化的相关性

目的 探讨心肺转流(CPB)下行冠脉搭桥术PETCO2与心输出量(CO)变化的相关性.方法 选择择期CPB下行冠状动脉搭桥术的患者50例,男32例,女18例,年龄49～73岁,BMI 19～25 kg/m2,ASAⅡ—Ⅳ级,采用静-吸复合全身麻醉,丙泊酚、舒芬太尼、顺式阿曲库铵及七氟醚等常规剂量维持麻醉.麻醉后放置Sw...     

不同水平呼气末正压通气对肥胖患者围术期呼吸功能的影响

目的 评价不同水平呼气末正压(PEEP)通气对肥胖患者胃减容手术围术期呼吸功能的影响.方法 选择2018年3月至2019年12月于我院行择期腹腔镜下胃减容手术肥胖患者70例,男43例,女27例,年龄28～52岁,BMI 34～43 kg/m2,ASAⅡ或Ⅲ级.采用随机数字表法将患者分为两组:PEEP 10 cmH2 O...     

A prospective randomized study to evaluate splanchnic hypoxia during beating-heart and conventional coronary revascularization

Objective: Cardiopulmonary bypass (CPB) is associated with gut mucosal hypoxia, which may contribute to gastrointestinal complications. We examined gastric mucosal oxygenation together with whole-body oxygen flux in low-risk patients undergoing coronary artery bypass grafting (CABG) with and without CPB. Methods: Fifty-four patients undergoing primary CABG by the same surgeon were randomized into either on-pump (ONCAB, n=27) or off-pump (OPCAB, n=27) groups. The ONCAB group underwent mild hypothermic (35°C) pulsatile CPB with arterial line filtration. Each patient underwent perioperative monitoring with continuous tonometry and cardiac output devices. Gastric intramucosal pH (pHi), gastric-arterial carbon dioxide partial pressure difference (CO₂ gap), whole-body oxygen delivery (DO₂) and consumption (VO₂) and whole-body oxygen extraction fraction were measured at sequential time-points intraoperatively and up to 6 h postoperatively. Anaesthetic management was standardized. Results: Both groups had similar demographic makeup and extent of revascularization (ONCAB 2.6±0.9 grafts versus OPCAB 2.5±0.8 grafts; P=0.55). The ONCAB group had a mean (±SD) CPB time of 62±25 min and aortic cross-clamp time of 32±11 min. In both groups there was a similar and progressive drop in pHi intraoperatively. Postoperatively, there was a gradual separation between the groups with ONCAB patients showing no further decline in pHi, while further deterioration was observed in the OPCAB group up to 6 h postoperatively. There was a significant difference between the groups over time (P=0.03). There was a corresponding progressive rise in CO₂ gap perioperatively in both groups, with ONCAB patients demonstrating superior preservation of gastric mucosal oxygenation in the early postoperative period. Global oxygen utilization measurements showed superior DO₂ and VO₂ in the OPCAB group throughout the study. Conclusions: Despite superior global oxygen flux associated with beating-heart revascularization, gastric mucosal hypoxia occurred to similar extents in both groups with worsening trends for the OPCAB patients postoperatively. The splanchnic pathophysiology during beating-heart revascularization should be further explored.     

Respiratory dysfunction after coronary artery bypass grafting employing bilateral internal mammary arteries: the influence of intact pleura

Objective: To evaluate the role of intact pleurae regarding the postoperative respiratory functional status in patients undergoing coronary revascularization employing both internal mammary arteries (IMAs), according to the pedunculated or skeletonized technique (SKT) with opened or intact pleurae. Materials and methods: Using both IMAs, 299 patients underwent elective coronary revascularization. They were randomized and divided into group I (n=82, undergoing IMA harvesting according to the SKT without opening the pleurae); group II (n=186, undergoing IMA harvesting according the pedunculated technique with open pleurae); and group III (n=31, undergoing IMA harvesting according the SKT with incidentally opened pleurae). There were no differences regarding the preoperative patient characteristics and the anaesthetic and surgical management. Results: There were two deaths in group I versus seven in group II and one in group III (P=ns). The number of total arterial myocardial revascularization and arterial composite grafts was significantly higher in groups I and III than in group II, (P<0.001 and P<0.005, respectively). The incidence of postoperative complications was similar between groups. Blood loss of >1000 ml was significantly higher in group II than group I (P<0.028); but the incidence of re-thoracotomy and blood transfusion was similar between groups. The mechanical ventilation time was significantly higher in groups II and III versus group I (P<0.018 and P<0.02, respectively). The incidence of prolonged ventilation (>24 h), pleural effusion, thoracocentesis and atelectasis, resulted in being significantly higher in group II than group I. The incidence of thoracocentesis was significantly higher in group III than group I. The pain score and analgesic requirements at 1–12 h after awakening were significantly higher in groups II and III versus group I, becoming similar after the chest tubes were removed. PaO₂ was significantly higher, and PaCO₂ and FiO₂ were significantly lower in group I than groups II and III at 1 and 4 h before extubation and at 1 and 4 h after extubation. PaO₂ and PaCO₂ became similar between groups at the 5th postoperative day. Conclusions: According to our results, we may conclude that pleural integrity has beneficial effects on the respiratory functional status after coronary revascularization using both IMAs. A meticulous and more careful IMA harvesting approach significantly reduces the postoperative morbidity regarding the pulmonary functional status, and as a consequence, reduces the hospital costs.     

Effects of prostaglandin E1 on the cardiovascular response to tracheal intubation

Study Objective: To evaluate the efficacy of prostaglandin E, in attenuating the hypertensive response to laryngoscopy and intubation.

Design: Controlled, comparative, and randomized study.

Setting: Induction of anesthesia for elective surgery at a university hospital.

Patients: Thirty normotensive patients (ASA physical status I) undergoing elective surgery divided into three groups. Each group consisted of ten patients.

Interventions: Anesthesia was induced with thiopental sodium 5 mglkg intravenously, and tracheal intubation was facilitated with vecuronium 0.2 mglkg. Either 0.3 μglkg of prostaglandin E₁, 0.6 μg/kg of prostaglandin E₁, or saline (control) was injected 15 seconds before starting direct laryngoscopy (within 30 seconds), which was attempted 2 minutes after administration of thiopental sodium and vecuronium.

Measurements and Main Results: Patients receiving saline showed a significant increase in mean arterial pressure and rate-pressure product associated with tracheal intubation. These increases following tracheal intubation were significantly less in prostaglandin E₁-treated patients than in the control group (p < 0.05).

Conclusions: A single rapid intravenous administration of prostaglandin E₁ is a practical pharmacologic and safe method to attenuate the hypertensive response to tracheal intubation. The use of 0.6 μglkg of prostaglandin E₁ as a supplement during induction is recommended for reducing the pressor response to intubation on the basis of rate-pressure product and mean arterial pressure , following intubation as an index.     

Verbessert die intraoperative Hyperventilation neuropsychologische Funktionen bei älteren Patienten nach Allgemeinnarkosen?

The purpose of the study was to investigate the effect of intraoperative hyperventilation on postoperative cognitive functions. METHODS: A total of 120 patients (60 older and 60 younger than 65 years old) were allocated randomly to group I "hyperventilation" (p(et)CO(2)=30 mmHg) or group II "normoventilation" (p(et)CO(2)=45 mmHg). Before the operation and on days 1, 3 and 6 after the operation, a battery of neuropsychological tests was performed (concentration endurance test d2, number connection test, digit symbol test). A decline of 20% in at least one test was regarded as postoperative cognitive deficit (POCD). Anaesthesia was maintained with isoflurane in nitrous oxide/oxygen supplemented with fentanyl. RESULTS: In all patients pooled, POCD was present in 26 patients (22%). In patients older than 65 years, POCD was present in 3 cases after hyperventilation and 13 cases after normoventilation ( p<0.01). In younger subjects, 5 cases of POCD were diagnosed in each ventilation group. Furthermore, POCD was more severely pronounced in older patients after normoventilation. CONCLUSION: In older patients, POCD occurred more frequently after intraoperative normoventilation. We assume that a reduced amount of noxious substances reach the brain after hyperventilation, because hyperventilation reduces the cerebral blood flow.     

后腹腔镜手术患者术后球结膜水肿的危险因素

目的 分析泌尿外科后腹腔镜手术患者术后发生球结膜水肿的危险因素。方法 收集2018年9月至2019年12月在山西医科大学第一医院接受泌尿外科后腹腔镜手术患者的临床资料,按术后是否发生球结膜水肿分为球结膜水肿组与未发生球结膜水肿组。对患者相关资料进行单因素及多因素Logistic回归分析,绘制ROC曲线并计算曲线下面积。结果 825例患者中术后球结膜水肿85例(10.3%)。单因素分析显示,与对照组相比,肾癌手术占比明显增高,术中出血量、输液量明显增多,折刀位头低角度增大,手术时间明显延长。CO₂气腹压力升高、气管插管5 min后、侧卧折刀位5 min后、恢复平卧位前、气腹结束并恢复平卧位后5 min时P_ETCO₂明显增高(P<0.05)。Logistic回归分析显示：折刀位头低角度(OR=2.967,95%CI:1.825～4.826,P<0.001),手术时间(OR=30.673,95%CI:3.861～243.676,P=0.001),CO₂气腹压力(OR=8.371,95%CI:3...     

Pharmacodynamic effects of three doses of ORG 9426 used for endotracheal intubation in humans

Study Objective: To determine the pharmacodynamic characteristics of three incremental doses of ORG 9426 used for endotracheal intubation in patients.

Design: Double-blind, randomized administration of one of three doses of intravenous ORG 9426.

Setting: Inpatients requiring surgery at Georgetown University Medical Center.

Patients: Thirty-six patients, ages 18 to 65, ASA physical status I, II, and III, scheduled for general surgery.

Interventions: After Georgetown University Institutional Review Board approval and patient consent, patients were premeditated with midazolam or droperidol. Anesthesia was induced with thiopental sodium and fentanyl. Anesthesia was maintained with 60% nitrous oxide in oxygen. The ulnar nerve was stimulated supramaximally with a 2 Hz train-of four (TOF) every 20 seconds. Thumb contractions were measured with a force transducer. When TOF and anesthesia were stable, 2, 2.5, or 3 times the ED₉₅ of ORG 9426 (570 μg/kg 710 μg/kg or 850 μg/kg) was administered randomly. Tracheal intubation was attempted at maximal depression of the first TOF response (T₁).

Measurements and Main Results: The following parameters were measured: time interval from the injection of ORG 9426 to 90% depression of T₁ (T₁ 90% block), maximal T₁ depression (onset time), intubating conditions, clinical duration (time for return of T₁ to 25% of control), heart rate (HR), blood pressure (BP), and any adverse clinical experience. ORG 9426 provided adequate intubating conditions in all patients but two, independent of the dose used. Its onset time was rapid, but increasing the dose did not shorten the onset. T₁ 90% block was achieved rapidly (75 ± 25 seconds to 78 ± 18 seconds, means ± SD). The clinical duration of ORG 9426 was relatively short and lengthened with increasing doses (from 36 ± 18 minutes at 570 μg/kg to 42 ±10 minutes at 850 μg/kg. Spontaneous twitch recovery from 10% to 25% was similar in all dosage groups (5 ± 1 minutes to 6 ± 4 minutes). No clinically significant changes in HR and BP and no adverse clinical experiences were noted in any group.

Conclusion: These findings warrant further clinical evaluation of ORG 9426 for induction and maintenance of muscle relaxation in humans.     

Effects of alkalinization of lidocaine on the pain of skin infiltration and intravenous catheterization

Study Objective: To test the hypothesis that alkalinization of lidocaine decreases the pain of skin infiltration in surgical patients.

Design: Double-blind, randomized, prospective study.

Setting: Preoperative holding units, Brigham and Women's Hospital.

Patients: 184 adult surgical patients.

Interventions: We compared the efficacy of 1% lidocaine with and without 0.1 mEq/ml of sodium bicarbonate (NaHC0₃) for relief of pain of (1) skin infiltration and (2) intravenous (IV) catheterization prior to surgery.

Measurements and Main Results: Patients evaluated the intensity of pain using a 100 mm visual analog scale (VAS). There were no differences between study groups (lidocaine with NaHCO₃, N = 89; lidocaine alone, N = 95) with respect to site of catheterization or catheter gauge used. Lidocaine plus NaHC0₃ caused significantly less pain on skin infiltration (median VAS = 4; RANGE = 0 to 51) than did lidocaine alone (VAS = 8; RANGE = 0 to 48; p < 0.008). Pain of IV catheterization also did not differ between groups. There was a weak correlation between catheter gauge and pain of IV catheterization (r = −0.19; p = 0.01).

Conclusions: Pain resulting from skin infiltration of lidocaine solutions can be diminished by adding NaHC0₃ However, catheter size is more important than the presence or absence of NaHC0₃ in determining the pain of IV catheterization.     

瑞芬太尼联合右美托咪定在腹腔镜疝囊高位结扎术中的麻醉效果及对并发症的影响

目的分析瑞芬太尼联合右美托咪定在腹腔镜疝囊高位结扎手术腹股沟疝患儿的麻醉效果及对并发症的影响。 方法选择2017年1月至2021年1月珠海市中西医结合医院收治的98例腹股沟疝患儿作为研究对象,研究组（49例）采用瑞芬太尼联合右美托咪定麻醉,对照组（49例）采用常规麻醉,对比入室（T₀）、置喉罩（T₁）、手术开始（T₂）、术毕（T₃）时段2组患儿的心率、平均动脉压（MAP）、呼气末二氧化碳分压（P_ETCO₂）及脑电双频指数（BIS）,记录2组患儿的拔喉罩时间、呼吸恢复时间、完全清醒时间及并发症发生情况。 结果相比T0时间点,T₁时间点的2组患儿心率水平、MAP水平、BIS指数明显降低,研究组明显高于对照组（P<0.05）,2组患儿P_ETCO₂水平较T₀均明显升高,但组间对比无统计学意义（P>0.05）。T₂时间点的2组患儿心率水平、MAP水平、BIS指数明显降低,研究组明显高于对照组（P<0.05）,2组患儿的P_ETCO₂水平较T₀均明显升高,而研究组明显低于对照组（P<0.05）。T₃时间点2组患儿心率水平、BIS指数明显降低,研究组明显高于对照组（P<0.05）,MAP水平低于T₀水平,但组间对比无差异（P>0.05）;2组患儿的P_ETCO₂水平较T₀均明显升高,而研究组明显低于对照组（P<0.05）。研究组患儿的拔喉罩时间、呼吸恢复时间、完全清醒时间均明显低于对照组（P<0.05）。研究组患儿的呛咳及咽喉疼痛发生率稍低于对照组（P>0.05）,而躁动、呼吸抑制及恶心呕吐发生率明显低于对照组（P<0.05）。 结论瑞芬太尼联合右美托咪定可有效保持腹股沟疝患儿腹腔镜疝囊高位结扎术中的血流动力学稳定,具有良好的镇静及麻醉后复苏效果,并可减少围手术期并发症的发生。     

Jugular bulb oxygen saturation during propofol and isoflurane/nitrous oxide anesthesia in patients undergoing brain tumor surgery.

We investigated, in brain tumor patients, the jugular bulb venous oxygen partial pressure (PjO2) and hemoglobin saturation (SjO2), the arterial to jugular bulb venous oxygen content difference (AJDO2), and middle cerebral artery blood flow velocity (Vmca) during anesthesia, and the effect of hyperventilation on these variables. Twenty patients were randomized to receive either isoflurane/ nitrous oxide/fentanyl (Group 1) or propofol/fentanyl (Group 2). At normoventilation (PacO2 35 +/- 2 mm Hg in Group 1 and 33 +/- 3 mm Hg in Group 2), SjO2 and PjO2 were significantly higher in Group 1 than in Group 2 (SjO2 60% +/- 6% and 49% +/- 13%, respectively; P = 0.019) (PjO2 32 +/- 3 and 27 +/- 5 mm Hg, respectively; P = 0.027). In Group 2, 5 of 10 patients had SjO2 < 50%, and 3 of these patients had SjO2 < 40% and AJDO2 > 9 mL/dL. All patients in Group 1 had SjO2 > 50%. During hyperventilation, there were no differences in SjO2, PjO2, or AJDO2 between the two groups. On hyperventilation, there was no correlation between the relative decreases of Vmca and 1/AJDO2 (r = 0.21, P = 0.41). The results indicate during propofol anesthesia, half of the brain tumor patients showed signs of cerebral hypoperfusion, but not during isoflurane/nitrous oxide anesthesia. Furthermore, during PacO2 manipulations, shifts in Vmca are inadequate to evaluate brian oxygen delivery in these patients. Implications: During propofol anesthesia at normoventilation, 50% of brain tumor patients showed signs suggesting cerebral hypoperfusion, but this could not be demonstrated during isoflurane/nitrous oxide anesthesia. During PacO2 manipulations, consecutive measurements of the cerebral blood flow velocity may be inadequate to assess cerebral oxygenation.     

Investigation of the pharmacokinetics and analgesic effects of an intramuscular injection of sustained-release sufentanil for postoperative pain: An open study

Study Objectives: To investigate the pharmacokinetics after an intramuscular (IM) injection of sufentanil in thin vegetable oil in postsurgical patients and to determine whether sustained-release IM sufentanil can provide safe and sufficient analgesia of long duration in these patients.

Design: Open study.

Setting: University hospital.

Patients: 10 ASA physical status I and II patients aged 18 to 65 years who were scheduled for elective surgery.

Interventions: All patients were premeditated with lorazepam and anesthetized with a general anesthetic technique containing nitrous oxide, fentanyl, and isoflurane. As soon as significant pain [visual analog scale score of 5 or greater (range, 0 = no pain to 10 = worst pain imaginable)] occurred during the early postoperative period, the patient received an IM injection of sustained-release sufentanil.

Measurements and Main Results: During the first 48 hours following surgery, blood samples were taken for determination of plasma sufentanil concentrations. Blood pressure, heart rate, respiratory rate, pain scores, and sedation scores were documented at the same time. The IM administration of sufentanil in thin vegetable oil provided sufficient pain relief, although the onset of analgesia was rather slow (± 1 hour). The analgesic effect was still apparent 48 hours later. Plasma concentration of sufentanil at the different time points varied from 0.021 to 0.142 ng/ml, with a mean maximal peak concentration of 0.103 ng/ml. The plasma concentration 48 hours after injection varied from 0.026 to 0.074 ng/ml.

Conclusions: Although an IM injection of sufentanil in thin vegetable oil is effective for postoperative pain relief, it is associated with wide interindividual variability in plasma concentration of sufentanil and long duration of action.     

Reliability of CO2 measurements from the airway by a pharyngeal catheter in unintubated, spontaneously breathing subjects

Although several short communications have appeared describing attempts to record the concentrations of carbon dioxide (CO₂) from the unintubated airway by a catheter placed in the nose, so far only few reports have documented the reliability of the method. To evaluate the reliability of CO₂ measurements by a catheter in the open, unintubated airway during spontaneous respiration, a 12 CH PVC catheter was forwarded through the nostril to the hypopharynx and connected to a capnograph in nine healthy volunteers. Another capnograph was connected to a tightly fitting face mask and simultaneous CO₂ recordings were attained from the two parts of the airway during normoventilation, hyperventilation and rebreathing. A corresponding blood sample was drawn from the radial artery for blood gas analysis. The configurations of the capnograms recorded from the pharyngeal catheter were similar to those recorded from the face mask. The results were analysed by a multifactor analysis of variance. The carbon dioxide tension ( p CO₂) was significantly influenced by degree of ventilation ( P <0.0001), subject ( P <0.0001), measurement site ( P =0.030) and interaction subject-ventilation ( P =0.015). In spite of the significant influence of the measurement site, the difference between end tidal carbon dioxide tension ( P CO₂(ET)) and carbon dioxide tension in arterial blood ( P CO₂(a)) was small. The mean differences between paired measurements ( p CO₂(ET)- p CO₂(a)) were -0.10 kPa±0.41 kPa (mean±SD) for the catheter and -0.20 kPa ±0.43 kPa for the face mask. The study demonstrates that reliable recordings of CO₂ concentrations during spontaneous respiration can be obtained by a thin catheter positioned in the hypopharynx.     

Low-flow transtracheal rescue insufflation of oxygen after profound desaturation

BACKGROUND: The objective of this study was to determine whether low-flow transtracheal insufflation of oxygen (TRIO) could rescue an animal from profound desaturation. This temporizing maneuver could be useful during cannot-intubate or -ventilate scenarios by resolving hypoxia without the morbidity associated with more invasive procedures. METHODS: Seven swine for a total of 12 runs were studied. Animals were pharmacologically anesthetized, paralyzed, and mechanically ventilated with room air. After disconnection from the ventilator and desaturation to an Spo2 < 50%, low-flow TRIO (2 L/min) was administered for 1 hour. RESULTS: All animals survived and Spo2 increased to greater than 90% in 23 seconds on average. Pao2 (mean, 183 mm Hg) remained elevated throughout the study. Hemodynamic stability was maintained for at least 15 minutes. CONCLUSION: Low-flow TRIO rescued animals from profound hypoxia and maintained oxygenation for at least 1 hour. Low-flow TRIO did not prevent hypercarbia with its subsequent sympathetic activation.     

Recovery from mivacurium-induced neuromuscular blockade after neurosurgical procedures of long duration

Study Objective: To determine if recovery following prolonged (5 hours in length or greater) infusions of mivacurium is different from recovery after single bolus administration.

Design: open-labelled, controlled study.

Setting: Inpatient neurosurgical service at a university hospital.

Patients: 36 patients between the ages of 18 to 65 without significant history of renal, hepatic, cardiac, or metabolic disease undergoing neurosurgical procedures. 21 patients had craniotomies or skull base procedures of an estimated length of 5 hours or greater; 15 patients (control) underwent short neurosurgical operations (two hours or less).

Interventions: Intravenous (IV) mivacurium 0.15 mg/kg was given with stable general anesthesia with 70% nitrous oxide in oxygen, 0.2% to 0.3% end-tidal isoflurane, and continuous infusion of fentanyl. The control group was allowed to recover spontaneously after single bolus administration while neuromuscular blockade was maintained in the study group with a continuous infusion of mivacurium until 30 minutes before completion of surgery, at which time the infusion was discontinued and neuromuscular function was allowed to recover spontaneously.

Measurements and Main Results: The evoked compound electromyogram of the adductor pollicis brevis muscle was measured during stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. Measurements included time to 50% and 90% depression of twitch (T₁ of the TOF response), time to T₁ equal to 25% (T₁25), 50% (T₁50), and 75% (T₁75) of baseline, and TOF ratio (TR) at 10%, 25%, 50%, and 75% recovery. Recovery index (RI), which is T₁75 minus T₁25, was also determined. All mivacurium infusion rates decreased during surgery. Recovery rates were significantly longer in the long infusion (LI) group than the control group. RI was also increased in the LI group compared with the single bolus control (11.3 ± 1.2 minutes vs. 7.1 ± 0.8 minutes p < 0.05).

Conclusions: Recovery following mivacurium by prolonged continuous infusion was slower than that observed after single bolus administration in this patient population. Clinically, this increased time to recovery may be insignificant.     

腹腔镜小儿腹股沟斜疝内环结扎术对循环及血气指标的影响

目的探讨腹腔镜小儿腹股沟斜疝内环结扎术的应用效果及对患儿血气指标的影响。 方法回顾性分析2017年3月至2018年6月，山东省聊城市人民医院腹股沟斜疝患儿49例，所有患儿均行腹腔镜下小儿腹股沟斜疝内环结扎术。比较患儿气腹前（T0）、气腹后10 min（T1）、气腹后30 min（T2）及放气后10 min（T3）循环及血气指标的改变。 结果与T0比较，T1～T3时患儿平均动脉压、收缩压、舒张压、每搏输出量循环指标水平均无明显变化（P>0.05）；T1～T2时心率明显加快（P<0.05）；T3时又恢复至T0水平（P>0.05）。与T0比较，T1、T2时患儿动脉血氧分压（PaO₂）及pH值均明显降低，动脉血二氧化碳分压（PaCO₂）明显升高（P均<0.05），T3时PaO₂、PaCO₂及pH值均恢复至T0时水平（P>0.05），T0～T3时间内患儿动脉血氧饱和度无明显变化（P>0.05）。 结论腹腔镜小儿腹股沟斜疝内环结扎术可在一定程度上影响患儿血气，但对循环系统并无明显影响，仅心率有轻微增快。