Spontaneous Ventilation Group Research Articles

The impact of tubeless anesthesia versus intubated anesthesia on cerebral oxygen saturation and postoperative cognitive function in patients undergoing video-assisted thoracoscopic surgery: a randomized trial.

In video-assisted thoracoscopic surgery (VATS), intubated anesthesia may affect cerebral oxygen balance and postoperative cognitive dysfunction (POCD). To avoid complications associated with intubated anesthesia, tubeless strategies have been proposed in recent years, but its effect on cerebral oxygen balance and POCD is still unclear. This prospective study compared the cerebral oxygen saturation and the incidence of POCD in patients undergoing VATS anesthetized with tubeless anesthesia vs. intubated anesthesia. A total of 60 patients with American Society of Anesthesiologists Standard (ASA) grade I-II who planned to undergo VATS at The First People's Hospital of Yunnan Province between May and October 2021 were selected and divided into non-intubated spontaneous ventilation group (SV group) or intubated mechanical ventilation group (MV group) by random number method. The primary outcome included the incidence of POCD and Mini-Mental State Examination (MMSE) on the 1st before operation and the 4th, 7th, 14th, and 30th day postoperatively, and cerebral oxygen saturation during surgery. Other outcomes of interest include respiratory and hemodynamic parameters, serum concentration of cognitive function related proteins [S100β, interleukin (IL)-6, IL-1β, and tumor necrosis factor α (TNF-α)], inflammatory cell counts, perioperative adverse events (arrhythmia, hypoxemia, asphyxia, etc.), postoperative pain scores, etc. The incidence of hypercapnia in the SV group was significantly higher than in the MV group (P<0.001). Cerebral oxygen saturation at intraoperative was significantly higher than that in MV group (P<0.01). There was no significant difference in the incidence of POCD and the expression of cognitive function related proteins between the two groups (P>0.05). Leukocyte and neutrophil counts were significantly higher in the MV group after operation (P<0.05), whilst compared to the MV group, the SV group showed shorter postoperative recovery time, rest time before the first out of bed activity, chest tube duration, as well as less drainage volume of the chest tube and postoperative sore throat rarely occurred (P<0.05). Tubeless VATS can increase the incidence of hypercapnia and intraoperative cerebral oxygen saturation, but has no statistically significant difference in the incidence of POCD. In addition, tubeless anesthesia reduces systemic inflammatory, promotes the early postoperative mobilization, and accelerates the postoperative rehabilitation of patients. Chinese Clinical Trial Registry ChiCTR2100042381.

Better intraoperative cardiopulmonary stability and similar postoperative results of spontaneous ventilation combined with intubation than non-intubated thoracic surgery.

Non-intubated spontaneous ventilation video-assisted thoracic surgery lobectomy is a well-known procedure, but there are doubts regarding its safety. To solve this problem, we developed a safe procedure for spontaneous ventilation thoracic surgery (spontaneous ventilation with intubation). This study analyzed the intraoperative parameters and postoperative results of spontaneous ventilation with intubation. Between March 11, 2020 and March 26, 2021, 38 spontaneous ventilation with intubation video-assisted thoracic surgery lobectomies were performed. We chose the first 38 non-intubated spontaneous ventilation video-assisted thoracic surgery lobectomy cases with a laryngeal mask performed in 2017 for comparison. There were no significant differences between the non-intubated spontaneous ventilation and spontaneous ventilation with intubation groups in postoperative surgical results (surgical time: 98,7 vs. 88,1min (p = 0.067); drainage time: 3.5 vs. 2.7days (p = 0.194); prolonged air leak 15.7% vs. 10.5% (p = 0.5); conversion rate to relaxation: 5.2% vs. 13.1% (p = 0.237); failure of the spontaneous ventilation rate: 10.5% vs. 13.1% (p = 0.724); and morbidity: 21% vs. 13.1% (p = 0.364)) and oncological outcomes. Significantly lower lowest systolic and diastolic blood pressure (systolic, 83.1 vs 132.3mmHg, p = 0.001; diastolic 47.8 vs. 73.4mmHg, p = 0.0001), lowest oxygen saturation (90.3% vs 94.9%, p = 0.026), and higher maximum pCO2 level (62.5 vs 54.8kPa, p = 0.009) were found in the non-intubated spontaneous ventilation group than in the spontaneous ventilation with intubation group. Spontaneous ventilation with intubation is a more physiological procedure than non-intubated spontaneous ventilation in terms of intraoperative blood pressure stability and gas exchange. The surgical results were similar in the two groups.

Individualized positive end-expiratory pressure following alveolar recruitment manoeuvres in lung-healthy anaesthetized dogs: a randomized clinical trial on early postoperative arterial oxygenation

ObjectiveTo assess and compare the effect of intraoperative stepwise alveolar recruitment manoeuvres (ARMs), followed by individualized positive end-expiratory pressure (PEEP), defined as PEEP at maximal respiratory system compliance + 2 cmH2O (PEEPmaxCrs+2), with that of spontaneous ventilation (SV) and controlled mechanical ventilation (CMV) without ARM or PEEP on early postoperative arterial oxygenation in anaesthetized healthy dogs. Study designProspective, randomized, nonblinded clinical study. AnimalsA total of 32 healthy client-owned dogs undergoing surgery in dorsal recumbency. MethodsDogs were ventilated intraoperatively (inspired oxygen fraction: 0.5) with one of the following strategies: SV, CMV alone, and CMV with PEEPmaxCrs+2 following a single ARM (ARM1) or two ARMs (ARM2, the second ARM at the end of surgery). Arterial blood gas analyses were performed before starting the ventilatory strategy, at the end of surgery, and at 5, 10, 15, 30 and 60 minutes after extubation while breathing room air. Data were analysed using Kruskal-Wallis and Friedman tests (p < 0.050). ResultsAt any time point after extubation, PaO2 was not significantly different between groups. At 5 minutes after extubation, PaO2 was 95.1 (78.1–104.0), 93.8 (88.3–104.0), 96.9 (86.6–115.0) and 89.1 (87.6–102.0) mmHg in the SV, CMV, ARM1 and ARM2 groups, respectively. PaO2 decreased at 30 minutes after extubation in the CMV, ARM1 and ARM2 groups (p < 0.050), but it did not decrease after 30 minutes in the SV group. Moderate hypoxaemia (PaO2, 60–80 mmHg) was observed in one dog in the ARM1 group and two dogs each in the SV and ARM2 groups. Conclusions and clinical relevanceIntraoperative ARMs, followed by PEEPmaxCrs+2, did not improve early postoperative arterial oxygenation compared with SV or CMV alone in healthy anaesthetized dogs. Therefore, this ventilatory strategy might not be clinically advantageous for improving postoperative arterial oxygenation in healthy dogs undergoing surgery when positioned in dorsal recumbency.

The Effect of High-Flow Nasal Oxygen on Carbon Dioxide Accumulation in Apneic or Spontaneously Breathing Adults During Airway Surgery: A Randomized-Controlled Trial.

High-flow nasal oxygen (HFNO) is an emerging technology that has generated interest in tubeless anesthesia for airway surgery. HFNO has been shown to maintain oxygenation and CO2 clearance in spontaneously breathing patients and is an effective approach to apneic oxygenation. Although it has been suggested that HFNO can enhance CO2 clearance during apnea, this has not been established. The true extent of CO2 accumulation and resulting acidosis using HFNO during prolonged tubeless anesthesia remains undefined. In a single-center trial, we randomly assigned 20 adults undergoing microlaryngoscopy to apnea or spontaneous ventilation (SV) using HFNO during 30 minutes of tubeless anesthesia. Serial arterial blood gas analysis was performed during preoxygenation and general anesthesia. The primary outcome was the partial pressure of CO2 (Paco2) after 30 minutes of general anesthesia, with each group compared using a Student t test. Nineteen patients completed the study protocol (9 in the SV group and 10 in the apnea group). The mean (standard deviation [SD]) Paco2 was 89.0 mm Hg (16.5 mm Hg) in the apnea group and 55.2 mm Hg (7.2 mm Hg) in the SV group (difference in means, 33.8; 95% confidence interval [CI], 20.6-47.0) after 30 minutes of general anesthesia (P < .001). The average rate of Paco2 rise during 30 minutes of general anesthesia was 1.8 mm Hg/min (SD = 0.5 mm Hg/min) in the apnea group and 0.8 mm Hg/min (SD = 0.3 mm Hg/min) in the SV group. The mean (SD) pH was 7.11 (0.04) in the apnea group and 7.29 (0.06) in the SV group (P < .001) at 30 minutes. Five (55%) of the apneic patients had a pH <7.10, of which the lowest measurement was 7.057. No significant difference in partial pressure of arterial O2 (Pao2) was observed after 30 minutes of general anesthesia. CO2 accumulation during apnea was more than double that of SV after 30 minutes of tubeless anesthesia using HFNO. The use of robust measurement confirms that apnea with HFNO is limited by CO2 accumulation and the concomitant severe respiratory acidosis, in contrast to SV. This extends previous knowledge and has implications for the safe application of HFNO during prolonged procedures.

A Retrospective Analysis of Neuromuscular Blocking Drug Use and Ventilation Technique on Complications in the Pediatric Difficult Intubation Registry Using Propensity Score Matching.

Ventilation is critical in airway management, and failure can be fatal. The optimal ventilation approach for endotracheal intubation in children with difficult airways remains controversial. The Pediatric Difficult Intubation (PeDI) Registry is an international multicenter registry that collects intubation data in difficult to intubate children. The registry captures the initial (at induction) and final ventilation technique (at intubation), the use of neuromuscular blocking drugs (NMBDs), airway reactivity during intubation, and complications. We analyzed data in the PeDI Registry to determine the frequency of use of various ventilation techniques and associated complications. Because spontaneously breathing patients ventilate throughout intubation, we hypothesized that spontaneous ventilation would be associated with fewer complications than other approaches. We queried the PeDI Registry for cases entered between September 2012 and February 2016, from 16 children's hospitals. We categorized the attending anesthesiologist's ventilation plan into 3 groups: spontaneous ventilation, controlled ventilation after administering an NMBD, and controlled ventilation without administering an NMBD. Generalized Estimating Equation (GEE) model, with a binomial family distribution and logit link, was used to determine the association between ventilation technique and the risk of complications, as well as to account for within-site clustering. Propensity score matching was further applied to balance pretreatment characteristics of ventilation groups. Of 1289 anticipated difficult intubations, 507 (39%) were managed with spontaneous ventilation, 453 (35%) controlled ventilation with an NMBD, and 329 (26%) controlled ventilation without an NMBD. Complications occurred in 242 (18.8%; 95% confidence interval [CI], 16.6%-20.9%) patients. Of these, 218 (16.9%) were nonsevere, and 24 (1.9%) were severe. The spontaneous ventilation group had 114 (22.5%, standardized residual [Std.Res] = 4.29) nonsevere complications, which was higher than the controlled ventilation with an NMBD 60 (13.3%, Std.Res = -2.58), and controlled ventilation without an NMBD 44 (13.4%, Std.Res = -1.98), P < .001. Nearest neighbor matching with caliper width equal to 0.2 of the standard deviation (SD) of the logit of the propensity score also demonstrated that patients with spontaneous ventilation had greater odds of complications compared to controlled ventilation techniques: odds ratio (OR) = 2.07 (95% CI, 1.36-3.15; P = .001). Spontaneous ventilation is associated with more nonsevere complications, such as hypoxemia and laryngospasm, than controlled ventilation techniques during intubation of children with difficult airways. Inadequate anesthetic depth may contribute to increased complications.

Controlled vs Spontaneous Ventilation for Bronchoscopy in Children with Tracheobronchial Foreign Body.

Tracheobronchial foreign body aspiration is a common life-threatening condition in children. There are controversies in the management of this condition, including the type of ventilation during bronchoscopy. This study aims to compare anesthesia with controlled ventilation versus spontaneous ventilation in rigid bronchoscopy in children with foreign body aspiration. Patients who were candidates for rigid bronchoscopy due to foreign body aspiration were randomly assigned to either anesthesia with spontaneous ventilation or controlled ventilation. End tidal CO2 (ETCO2), electrocardiogram (ECG), heart rate (HR), oxygen saturation (SpO2), non-invasive blood pressure (NIBP) and complications and accidents during the surgery and recovery were recorded for each patient. Surgeon comfort during the procedure was also evaluated for each patient. A 20% change in HR or NIBP was considered significant. SpO2 values under 90% are considered desaturation. Fifty-one patients (31 male and 20 female) entered the study. The mean age was 26.76 months, ranging from 6 to 100 months. Choking and cough were present in 94% and 96.1% of the patients, respectively. Nuts were the most common foreign body (76.9%). The controlled ventilation group had significantly fewer complications, and surgeon comfort was significantly higher in this group. Oxygen desaturation was significantly more prevalent in the spontaneous ventilation group during laryngoscopy and bronchoscopy (P<0.001). Controlled ventilation has the potential to be used as an effective alternative option in anesthesia for patients with suspected foreign body aspiration.

The impact of spontaneous ventilation on non-operative lung injury in thoracic surgery: a randomized controlled rabbit model study.

One-lung ventilation (OLV) with general anaesthesia may increase adverse effects after thoracic surgery, specifically ventilator-induced lung injury. Spontaneous ventilation (SV) has no mechanical ventilation process, thus, we established a rabbit model to assess non-operative lung injury between OLV and SV. Thirty-six rabbits were randomly divided into 6 groups: OLV and SV (0, 2 and 4 h). Blood gas analysis was performed after thoracic surgery. Lung tissue and bronchoalveolar lavage fluid were obtained from the non-operative lung. Pathological injury score in lung tissue and tumour necrosis factor α (TNF-α) level in bronchoalveolar lavage fluid using enzyme-linked immunosorbent assay were determined. Moreover, messenger RNA and protein of TNF-α in lung tissue were also determined by quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Compared with the OLV group, significantly higher partial pressure of carbon dioxide (47.78 ± 3.57 vs 38.95 ± 3.88 mmHg, P < 0.01) and partial pressure of oxygen (101.08 ± 13.1 vs 85.6 ± 11.07 mmHg, P < 0.01), as well as a significantly lower pathological injury score (6.83 ± 1.17 vs 8.83 ± 1.72, P < 0.05), TNF-α level in bronchoalveolar lavage fluid (290.32 ± 29.38 vs 368.43 ± 31.26 pg/ml, P < 0.01), TNF-α messenger RNA (6.31 ± 1.13 vs 8.6 ± 1.34, P < 0.01), immunostaining intensity in lung tissue were found at 4 h in the SV group. However, there are no significant differences between OLV and SV groups at 2 h (P > 0.05), except in TNF-α messenger RNA. Based on this rabbit model, SV for thoracic surgery is not inferior to OLV in terms of lung injury. Considering our results, when performing time-consuming thoracic procedures under OLV, surgeons should more closely examine patients for non-operative lung injury postoperatively.

Comparing 3 ventilation modalities by measuring several respiratory parameters using the ProSeal laryngeal mask airway in children

Study objectiveTo determine quantitative differences in several routinely measured ventilation parameters using a standardized anesthetic technique and 3 different ventilation modalities in pediatric patients with a ProSeal laryngeal mask airway (PLMA). DesignRandomized prospective study. SettingPediatric hospital of a tertiary care academic medical center. PatientsThirty-three, American Society of Anesthesiologists classification 1-2, pediatric patients (12 months to 5 years). InterventionsThree different ventilation strategies: spontaneous ventilation (SV), pressure support ventilation (PSV), and pressure-controlled ventilation (PCV) were randomly applied to patients who underwent a standardized mask induction with sevoflurane/oxygen and propofol 3 mg/kg and morphine 0.05 mg/kg administered intravenously followed by PLMA insertion. Patients were maintained on sevoflurane and N2O. MeasurementsWe measured the differences in end-tidal CO2 (Etco2), tidal volume, and respiratory rate over time between SV, PSV, and PCV. These data were recorded at 5-minute intervals. Main resultsEtco2 (mm Hg) was significantly higher in the SV vs PSV (P=.016) and vs PCV (P<.001). Tidal volume (mL/kg) was significantly lower in SV vs PSV (P<.001) and vs PCV (P<.001). Respiratory rate (breaths/min) was significantly higher in SV vs PSV (P<.001) and vs PCV (P=.005). ConclusionsAll 3 modes of ventilation using a PLMA were safely used. Our SV group was noted to have a significantly higher Etco2 when compared with PSV and PCV with a mean Etco2 over time in excess of 55 mm Hg. PSV and PCV were found to be more appropriate ventilation strategies to more optimally control Etco2 over time in these patients.

Efficacy and safety of spontaneous ventilation technique using dexmedetomidine for rigid bronchoscopic airway foreign body removal in children

In children, removal of an airway foreign body is usually performed by rigid bronchoscopy under general anesthesia. Debate continues regarding the respiratory mode (spontaneous or controlled ventilation) and appropriate anesthetic drugs. Dexmedetomidine has several desirable pharmacologic properties and appears to be a useful agent for airway surgeries. This study evaluates the efficacy of spontaneous ventilation (SV) technique using dexmedetomidine for bronchoscopic removal of foreign bodies in children. Eighty pediatric patients undergoing rigid bronchoscopy for airway foreign body removal were randomly divided into two groups. In the SV group, dexmedetomidine (4 μg∙kg(-1)) and topical lidocaine (3-5 mg∙kg(-1)) were administered and the patients were breathing spontaneously throughout the procedure. In the manual jet ventilation (MJV) group, anesthesia was induced with fentanyl (2 μg∙kg(-1)), propofol (3-5 mg∙kg(-1)), and succinylcholine (1 mg∙kg(-1)), and MJV was performed. The success rates of foreign body removal, the incidence of body movement and other perioperative adverse events, and hemodynamic changes were similar between the two groups. The SV patients required longer stays in the postanesthesia care unit (P < 0.01) but experienced less coughing (P = 0.029) in the recovery room. Dexmedetomidine may provide appropriately deep anesthesia and ideal conditions for rigid bronchoscopic airway foreign body removal without respiratory depression or hemodynamic instability.

The Effectiveness of Noninvasive Positive Pressure Ventilation to Enhance Preoxygenation in Morbidly Obese Patients: A Randomized Controlled Study

Noninvasive positive-pressure ventilation (NPPV) with pressure support-ventilation and positive end-expiratory pressure are effective in providing oxygenation during intubation in hypoxemic patients. We hypothesized administration of oxygen (O2) using NPPV would more rapidly increase the end-tidal O2 concentration (ETO2) than preoxygenation using spontaneous ventilation (SV) in morbidly obese patients. Twenty-eight morbidly obese patients were enrolled in this prospective randomized study. Administration of O2 for 5 min was performed either with SV group or with NPPV (pressure support = 8 cm H2O, positive end-expiratory pressure = 6 cm H2O) (NPPV group). ETO2 was measured using the anesthesia breathing circuit, and is expressed as a fraction of atmospheric concentration. The primary end-point was the number of patients with an ETo(2) >95% at the end of O2 administration. Secondary end-points included the time to reach the maximal ETO2 and the ETO2 at the conclusion of O2 administration. A larger proportion of patients achieved a 95% ETO2 at 5 min with NPPV than SV (13/14 vs 7/14, P = 0.01). The time to reach the maximal ETO2 was significantly less in the NPPV than in the SV group (185 +/- 46 vs 222 +/- 42 s, P = 0.02). The mean ETO2 at the conclusion of O2 administration was larger in the NPPV group than the SV group (96.9 +/- 1.3 vs 94.1 +/- 2.0%, P < 0.001). A modest, although significant, increase in gastric distension was observed in the NPPV group. No adverse effects were observed in either group. Administration of O2 via a facemask with NPPV in the operating room is safe, feasible, and efficient in morbidly obese patients. In this population NPPV provides a more rapid O2 administration, achieving a higher ETO2.

CATARACT SURGERY;

Objective: To compare the effects of spontaneous versus controlled ventilation on IntraocularPressure (IOP) with concomitant haemodynamic changes during cataract extraction and intraocular (IOL) implantsurgery under anaesthesia. Design: Comparative study. Place and Duration of Study: The study was conducted atdepartment of Anesthesiology Combined Military Hospital Jhelum Cantt from Jan 2005 to Oct 2005. Subjects andMethods: 40 ASA I and II patients of both sexes aged 40-68 years, undergoing surgical cataract extraction werestudies. In 20 patients ventilation was controlled while the other 20 patients breathed spontaneously during surgery.IOP was measured preoperatively in non-operated eye.Results: Intraocular pressure (IOP) decreased below the baseline after induction of anaesthesia but it markedly increased after intubation in both group. During operation IOPdecreased more in controlled ventilation group than spontaneous ventilation group. At the end of surgery beforeextubation, IOP increased in both groups with a greater rise in spontaneous ventilation group and extubation wasfollowed by a further rise in IOP in both groups. Heart rate (HR) and arterial blood pressure (BP) changes followedalmost the same pattern as IOP. Conclusion: General anaesthetics decrease IOP in general. Laryngoscopy andintubation are anaesthesia-related events, which cause rise in IOP. In appropriate patients, general anaesthesia withcontrolled ventilation is an acceptable technique for intraocular surgery offering advantages in terms of intraocularpressure and cardiovascular stability compared to spontaneous ventilation.

Change in Intrathoracic Pressure in Rats with Spontaneous and Controlled Ventilation during Microgravity by Parabolic Flight

We previously reported that the intrathoracic pressure (ITP) decreases and the transmural pressure of the aortic wall (TMP) increases during 4.5 s of microgravity (muG) induced by free drop. To examine the ITP response to a longer period of muG in the absence of the respiratory rate (RR) decrease, i.e., bradypnea, which occurs at the onset of muG, we measured the aortic blood pressure at the diaphragma level (AP) and ITP. We then calculated the TMP at the aortic arch level during 20 s of muG induced by parabolic flight in anesthetized rats (n = 7) with either spontaneous ventilation (SPN-V) or controlled ventilation (CONT-V). In the SPN-V group, the bradypnea was observed in all rats after the onset of the muG (RR change -13.9 +/- 2.9/min). The ITP during muG (-9.3 +/- 0.9 mmHg) was significantly lower than that during 1 G (-7.7 +/- 0.9 mmHg), and the TMP was significantly increased during muG (112 +/- 6 mmHg) compared to 1 G (103 +/- 5 mmHg). Similar changes in ITP and TMP were observed in the CONT-V group: During muG and 1G, respectively, the ITP was -8.4 +/- 0.6 mmHg and -5.9 +/- 0.7 mmHg, and the TMP was 112 +/- 6 mmHg and 101 +/- 6 mmHg, whereas no change in RR was observed because of the controlled ventilation. These results show that the ITP decreases and the TMP increases during muG, and they are not affected by a disturbance of respiratory rhythm.

Anesthesia for removal of inhaled foreign bodies in children

Foreign body aspiration may be a life-threatening emergency in children requiring immediate bronchoscopy under general anesthesia. Both controlled and spontaneous ventilation techniques have been used during anesthesia for bronchoscopic foreign body removal. There is no prospective study in the literature comparing these two techniques. This prospective randomized clinical trial was undertaken to compare spontaneous and controlled ventilation during anesthesia for removal of inhaled foreign bodies in children. Thirty-six children posted for rigid bronchoscopy for removal of airway foreign bodies over a period of 2 years and 2 months in our institution were studied. After induction with sleep dose of thiopentone or halothane, they were randomly allocated to one of the two groups. In group I, 17 children were ventilated after obtaining paralysis with suxamethonium. In group II, 19 children were breathing halothane spontaneously in 100% oxygen. All the patients in the spontaneous ventilation group had to be converted to assisted ventilation because of either desaturation or inadequate depth of anesthesia. There was a significantly higher incidence of coughing and bucking in the spontaneous ventilation group compared with the controlled ventilation group (P = 0.0012). Use of controlled ventilation with muscle relaxants and inhalation anesthesia provides an even and adequate depth of anesthesia for rigid bronchoscopy.

Controlled mechanical ventilation in horses under vecuronium blockage

The purpose of this study was to investigate the metabolic and cardiorespiratory effects of the administration of vecuronium under controlled mechanical ventilation versus spontaneous ventilation in horses. Twenty healthy horses scheduled to elective surgery were randomized and assigned in two groups. All animals were pre-medicated with romifidine (100 mu g/kg iv), anesthesia was induced with an association of tiletamine-zolazepam (2 mg/kg iv) and was maintained with halothane. Animals of group I remained in spontaneous ventilation without muscle relaxation while group II received vecuronium (0.1 mg/kg IV) and was submitted to controlled mechanical ventilation. Vecuronium administration did not cause any significant change of heart rate or rhythm, central venous pressure and arterial pressure. With the animals that remained under spontaneous ventilation, no differences were observed in these parameters. The animals that received vecuronium showed lower values of PaCO2 and normal values of pH in relation to the spontaneous ventilation group. Vecuronium duration was 12.83 ± 1.72 minutes. After halothane discontinuation the weaning time in group I I was 6.09 minutes with mean final PaCO2 values of 50.78 mmHg. There was no need of pharmacological reversion of vecuronium effect and recovery from anesthesia was similar in the two groups. In conclusion, the use of mechanical controlled ventilation and vecuronium in horses is easily performed, does not induce further cardiovascular depression and should be employed in equines undergoing major operations.

Region of epidural blockade determines sympathetic and mesenteric capacitance effects in rabbits.

The mechanisms producing hemodynamic changes during epidural anesthesia are incompletely understood. The role of capacitance changes in the splanchnic venous bed can be clarified by comparing blocks of differing segmental distributions. Specifically, we speculated that blocks that include the innervation to the mesenteric circulation alter hemodynamics, sympathetic activity, and venous capacitance to a greater extent than blocks without blockade of sympathetic nerves to this critical vascular bed. Rabbits were studied during alpha-chloralose anesthesia and mechanical ventilation. Sympathetic efferent nerve activity to the mesenteric vessels was measured by surgically placed electrodes, and mesenteric vein diameter was measured by videomicroscopy. Heart rate and mean arterial pressure were monitored by intraarterial cannulation. Responses were compared after administration of epidural lidocaine using a dose and catheter level that limited anesthetic to lumbar levels (lumbar group) or thoracic levels (thoracic group). In addition, hemodynamic responses were recorded after thoracolumbar block in animals receiving alpha-chloralose but breathing spontaneously (spontaneous ventilation group) and in awake animals (awake group). Mean arterial pressure decreased 38.3 +/- 5.8% in the thoracic group but only 16.5 +/- 2.8 in the lumbar group. Sympathetic efferent nerve activity decreased in the thoracic group but increased in the lumbar group. An increase in vein diameter followed thoracic epidural anesthesia, but venoconstriction was observed after lumbar epidural block. The addition of intravenous sedation with alpha-chloralose did not increase the hypotensive effect of epidural anesthesia in this model. Block of sympathetic fibers to the splanchnic circulation with thoracic epidural lidocaine produces mesenteric venodilatation that contributes to hypotension in rabbits. A lesser decrease in blood pressure follows blocks limited to lower segments, because baroreceptor stimulation produces increased splanchnic sympathetic activity and mesenteric venoconstriction. Responses in this model are comparable with and without general anesthesia and mechanical ventilation. To minimize hemodynamic consequences, epidural blockade should ideally be confined to the fewest necessary segments, avoiding splanchnic innervation if possible.

Cardiovascular effects of intermittent positive pressure ventilation in the anesthetized horse.

Intermittent positive pressure ventilation (IPPV) is useful method for compensate of respiratory function in anesthetized horses. However, IPPV may decrease cardiac output. Alterations in cardiac output of three groups (N = 5) healthy, halothane-anesthetized mares were determined and compared during a 120 min period of anesthesia. The groups were as follows: spontaneous ventilation (SV), controlled ventilation using an end-inspiratory pressure of 20 cmH2O (CV20) and a third group using 25 cmH2O (CV25) inspiratory pressure. In the CV groups, respiratory function was adequately maintained. Although, cardiac output tended to decrease over time in each group. After 105 min of anesthesia in the CV groups, the cardiac outputs decreased below 50 percent of pre-anesthetic values. In the CV25 group, cardiac outputs were significant difference (p < 0.05) from the SV group after 45, 90 and 120 min of anesthesia. There was no significant difference in cardiac output between SV and CV20 group over time. These values suggest that when long durations of anesthesia was used with the IPPV, decrease of cardiac output should be improved. In clinical use of halothane anesthesia, an end-respiratory pressure of 20 cmH2O seems to be appropriate because the mild decrease in cardiac output was observed even though a little high PaCO2.

Transcatheter Closure of Atrial Septal Defects

Transcatheter closure of atrial septal defects using a double-umbrella (clamshell) device can now be performed during an overnight hospital stay with little morbidity and no mortality. The initial 2-yr experience with anesthetic care for the procedure was collected and subsequently analyzed. Primary anesthetic care was given in 118 cases and urgent anesthetic intervention was required in another four cases. Anesthesia with spontaneous ventilation in patients with unprotected airways using intravenous ketamine and midazolam (average cumulative doses 1.4 and 0.17 mg.kg-1.h-1, respectively) was used in 93 cases (77%); mean maximum PaCO2 value was 41 +/- 6 mm Hg. In 29 patients (23%) tracheal intubation and muscle paralysis were used to facilitate control of airway and ventilation. Anesthetic-related complications occurred in three patients: ventilatory compromise developed in two patients in the spontaneous ventilation group and one patient experienced awareness during endotracheal anesthesia with paralysis. Procedural complications that altered anesthetic management were more frequent, including embolization of the clamshell device requiring surgical retrieval in two of six embolizations, intracardiac air embolization (four cases), tricuspid regurgitation (one case), device malplacement requiring late operation (one case), and transient brachial plexus injury (three cases). Anesthesia for transcatheter atrial septal defect closure allows precise device placement, prompt control of hemodynamic complications, and transesophageal echocardiographic monitoring of device placement. Although general anesthesia with spontaneous ventilation using ketamine and midazolam was usually safe and effective, tracheal intubation for control of airway and ventilation was sometimes necessary for safety and for optimal operating conditions. Familiarity with transcatheter closure techniques and close communication with the catheterization team is essential to minimize and treat associated complications.(ABSTRACT TRUNCATED AT 250 WORDS)

ANAESTHESIA FOR PAEDIATRIC TONSILLECTOMY: Comparison of Spontaneous Ventilation and Intermittent Positive Pressure Ventilation

Fifty children undergoing tonsillectomy were anaesthetized using either a spontaneous ventilation (SV) technique with halothane (and nitrous oxide in oxygen) or intermittent positive pressure ventilation (IPPV) (with nitrous oxide, in oxygen) facilitated by atracurium 0.5 mg kg-1. Time to full recovery was significantly less in the IPPV group (1.8 +/- 3.79 min) than the SV group (20.0 +/- 6.77 min) (P less than 0.001) and ventilated children had a better quality of long-term recovery (sleep score 1.02 for the SV and 1.44 for the IPPV groups) (P less than 0.01). Apart from a significantly greater E'CO2 in the halothane group (7.3 kPa +/- 0.9 compared with 5.1 kPa +/- 0.5) (P less than 0.001), there was no significant difference in operative or postoperative morbidity.