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1.
ObjectiveTo compare the effects of fraction of inspired oxygen (FiO2) with the addition of positive end-expiratory pressure (PEEP) during anesthesia on arterial oxygenation in the first 4 postoperative hours in dogs. We hypothesized that compared with dogs breathing FiO2 ≥ 0.95 and no PEEP (ZEEP), the use of intraoperative PEEP would improve postoperative oxygenation, and that the use of PEEP combined with an FiO2 of 0.4 would further improve it.Study designProspective, randomized study.AnimalsA total of 30 dogs undergoing unilateral stifle surgery.MethodsUsing a standardized anesthetic protocol, dogs were assigned to either FiO2 ≥ 0.95 and ZEEP, FiO2 ≥ 0.95 and 5 cmH2O PEEP or FiO2 0.4 and 5 cmH2O PEEP. All dogs were mechanically ventilated with a tidal volume of 12 mL kg–1. Dogs breathed room air after recovery from anesthesia. Arterial blood gases were measured during surgical closure and 10, 120 and 240 minutes after extubation. Demographic characteristics were compared with Kruskal–Wallis tests. The effects of treatment and time on the PaO2, PaCO2, PaO2:FiO2 and shunt fraction (F-shunt) were assessed with mixed-effect models.ResultsThe PaO2 and F-shunt were lower during anesthesia for dogs breathing FiO2 0.4. No differences among groups were measured after extubation for any variable.Conclusions and clinical relevanceCompared with dogs ventilated with FiO2 ≥ 0.95 and ZEEP, application of 5 cmH2O PEEP did not improve intraoperative gas exchange. The combination of 5 cmH2O PEEP and FiO2 0.4 resulted in lower intraoperative F-shunt values. However, no benefits from those maneuvers on postoperative PaO2 and F-shunt were recorded after extubation, suggesting that alterations in pulmonary function imposed by anesthesia were reversed soon after extubation.  相似文献   

2.
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.  相似文献   

3.

Objective

To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep.

Study design

Prospective, randomized, crossover study.

Animals

A total of nine adult sheep (36–52 kg).

Methods

Sheep were administered three treatments (≥10-day intervals) during isoflurane–fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg?1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO2 pneumoperitoneum); PNEUMOARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH2O increases in PEEP of 1 minute duration until 20 cmH2O of PEEP) was followed by 10 cmH2O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation.

Results

PaO2 was decreased from 435–462 mmHg (58.0–61.6 kPa) (range of mean values in CONTROL) to 377–397 mmHg (50.3–52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (Cqst, mL cmH2O?1 kg?1) was decreased from 0.85–0.92 in CONTROL to 0.52–0.58 in PNEUMO. PaO2 increased from 383–385 mmHg (51.1–51.3 kPa) in PNEUMO to 429–444 mmHg (57.2–59.2 kPa) in PNEUMOARM/PEEP (p < 0.05) and Cqst increased from 0.52–0.53 in PNEUMO to 0.70–0.74 in PNEUMOARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO2 and Cqst to control values. Cardiac index (L minute?1 m2) decreased from 4.80–4.70 in CONTROL to 3.45–3.74 in PNEUMO and 3.63–3.76 in PNEUMOARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg.

Conclusions and clinical relevance

Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.  相似文献   

4.
Objective To compare, ventilation using intermittent positive pressure ventilation (IPPV) with constant positive end‐expiratory pressure (PEEP) and alveolar recruitment manoeuvres (RM) to classical IPPV without PEEP on gas exchange during anaesthesia and early recovery. Study design Prospective randomized study. Animals Twenty‐four warm‐blood horses, weight mean 548 ± SD 49 kg undergoing surgery for colic. Methods Premedication, induction and maintenance (isoflurane in oxygen) were identical in all horses. Group C (n = 12) was ventilated using conventional IPPV, inspiratory pressure (PIP) 35–45 cmH2O; group RM (n = 12) using similar IPPV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths PIP 60, 80 then 60 cmH2O, held for 10–12 seconds). RMs were applied as required to maintain arterial oxygen tension (PaO2) at >400 mmHg (53.3 kPa). Physiological parameters were recorded intraoperatively. Arterial blood gases were measured intra‐ and postoperatively. Recovery times and quality of recovery were measured or scored. Results Statistically significant findings were that horses in group RM had an overall higher PaO2 (432 ± 101 mmHg) than those in group C (187 ± 112 mmHg) at all time points including during the early recovery period. Recovery time to standing position was significantly shorter in group RM (49.6 ± 20.7 minutes) than group C (70.7 ± 24.9). Other measured parameters did not differ significantly. The median (range) of number of RMs required to maintain PaO2 above 400 mmHg per anaesthetic was 3 (1–8). Conclusion Ventilation using IPPV with constant PEEP and RM improved arterial oxygenation lasting into the early recovery period in conjunction with faster recovery of similar quality. However this ventilation mode was not able to open up the lung completely and to keep it open without repeated recruitment. Clinical relevance This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses.  相似文献   

5.
ObjectivesTo investigate the influence of two inspired oxygen fractions (FIO2) on the arterial oxygenation in horses anaesthetized with isoflurane.Study DesignRetrospective, case-control clinical study.AnimalsTwo hundred equine patients undergoing non-abdominal surgery (ASA class 1–2), using a standardized anaesthetic protocol and selected from anaesthetic records of a period of three years, based on pre-defined inclusion criteria.MethodsIn group O (n = 100), medical oxygen acted as carrier gas, while in group M (n = 100), a medical mixture of oxygen and air (FIO2 0.60) was used. Demographic data, FIO2, arterial oxygen tension (PaO2) and routinely monitored physiologic data were recorded. The alveolar-arterial oxygen tension difference [P(A-a)O2] and PaO2/FIO2 ratio were calculated. The area under the curve, standardized to the anaesthetic duration, was calculated and statistically compared between groups using t-tests or Mann–Whitney tests as appropriate. Categorical data were compared using Chi-square tests.ResultsNo significant differences in age, body weight, sex, breed, surgical procedure, position, anaesthetic duration or arterial carbon dioxide tension were found. Mean FIO2 was 0.78 in group O and 0.60 in group M. Compared to group O, significantly lower values for PaO2 and for P(A-a)O2 were found in group M. In contrast, the PaO2/FIO2 ratio and the percentage of horses with a PaO2 <100 mmHg (13.33 kPa) were comparable in both groups.ConclusionsAlthough a reduction of the inspired oxygen fraction resulted in a lower PaO2, the P(A-a)O2 was also lower and the number of horses with PaO2 values <100 mmHg was comparable.Clinical relevanceIn healthy isoflurane anaesthetized horses, the use of a mixture of oxygen and air as carrier gas seems acceptable, but further, prospective studies are needed to confirm whether it results in a lower degree of ventilation/perfusion mismatching.  相似文献   

6.

Objective

To examine the intrapulmonary gas distribution of low and high tidal volumes (VT) and to investigate whether this is altered by an alveolar recruitment maneuver (ARM) and 5 cmH2O positive end-expiratory pressure (PEEP) during anesthesia.

Study design

Prospective randomized clinical study.

Animals

Fourteen client-owned bitches weighing 26 ± 7 kg undergoing elective ovariohysterectomy.

Methods

Isoflurane-anesthetized dogs in dorsal recumbency were ventilated with 0 cmH2O PEEP and pressure-controlled ventilation by adjusting the peak inspiratory pressure (PIP) to achieve a low (7 mL kg?1; n = 7) or a high (12 mL kg?1; n = 7) VT. Ninety minutes after induction (T90), an ARM (PIP 20 cmH2O for 10 seconds, twice with a 10 second interval) was performed followed by the application of 5 cmH2O PEEP for 35 minutes (RM35). The vertical (ventral=0%; dorsal=100%) and horizontal (right=0%; left=100%) center of ventilation (CoV), four regions of interest (ROI) (ventral, central-ventral, central-dorsal, dorsal) identified in electrical impedance tomography images, and cardiopulmonary data were analyzed using two-way repeated measures anova.

Results

The low VT was centered in more ventral (nondependent) areas compared with high VT at T90 (CoV: 38.8 ± 2.5% versus 44.6 ± 7.2%; p = 0.0325). The ARM and PEEP shifted the CoV towards dorsal (dependent) areas only during high VT (50.5 ± 7.9% versus 41.1 ± 2.8% during low VT, p = 0.0108), which was more distributed to the central-dorsal ROI compared with low VT (p = 0.0046). The horizontal CoV was centrally distributed and cardiovascular variables remained unchanged throughout regardless of the VT, ARM, and PEEP.

Conclusions and clinical relevance

Both low and high VT were poorly distributed to dorsal dependent regions, where ventilation was improved following the current ARM and PEEP only during high VT. Studies on the role of high VT on pulmonary complications are required.  相似文献   

7.
ObjectiveTo compare the effect of invasive continuous positive airway pressure (CPAP), pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) and spontaneous breathing (SB) on PaO2, PaCO2 and arterial to central venous oxygen content difference (CaO2-CcvO2) in healthy anaesthetized dogs.Study designProspective randomized crossover study.AnimalsA group of 15 adult male dogs undergoing elective orchidectomy.MethodsDogs were anaesthetized [buprenorphine, medetomidine, propofol and isoflurane in an air oxygen (FiO2= 0.5)]. All ventilatory treatments (CPAP: 4 cmH2O; PCV: 10 cmH2O driving pressure; PEEP, 4 cmH2O; respiratory rate of 10 breaths minute–1 and inspiratory-to-expiratory ratio of 1:2; SB: no pressure applied) were applied in a randomized order during the same anaesthetic. Arterial and central venous blood samples were collected immediately before the start and at 20 minutes after each treatment. Data were compared using a general linear mixed model (p < 0.05).ResultsMedian PaO2 was significantly higher after PCV [222 mmHg (29.6 kPa)] than after CPAP [202 mmHg (26.9 kPa)] and SB [208 mmHg (27.7 kPa)] (p < 0.001). Median PaCO2 was lower after PCV [48 mmHg (6.4 kPa)] than after CPAP [58 mmHg (7.7 kPa)] and SB [56 mmHg (7.5 kPa)] (p < 0.001). Median CaO2-CcvO2 was greater after PCV (4.36 mL dL–1) than after CPAP (3.41 mL dL–1) and SB (3.23 mL dL–1) (p < 0.001). PaO2, PaCO2 and CaO2-CcvO2 were no different between CPAP and SB (p > 0.99, p = 0.697 and p = 0.922, respectively).Conclusions and clinical relevanceCPAP resulted in similar arterial oxygenation, CO2 elimination and tissue oxygen extraction to SB. PCV resulted in improved arterial oxygenation and CO2 elimination. Greater oxygen extraction occurred with PCV than with CPAP and SB, offsetting its advantage of improved arterial oxygenation. The benefit of invasive CPAP over SB in the healthy anaesthetized dog remains uncertain.  相似文献   

8.

Objective

To examine changes in the distribution of ventilation and regional lung compliances in anaesthetized horses during the alveolar recruitment manoeuvre (ARM).

Study design

Experimental study in which a series of treatments were administered in a fixed order on one occasion.

Animals

Five adult Warmblood horses.

Methods

Animals were anaesthetized (xylazine, midazolam–ketamine, isoflurane), placed in dorsal recumbency and ventilated with 100% oxygen using peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) of 20 cmH2O and 0 cmH2O, respectively. Thoracic electrical impedance tomography (EIT), spirometry and routine anaesthesia monitoring were performed. At 90 minutes after induction of anaesthesia, PIP and PEEP were increased in steps of 5 cmH2O to 50 cmH2O and 30 cmH2O, respectively, and then decreased to baseline values. Each step lasted 10 minutes. Data were recorded and functional EIT images were created using three breaths at the end of each step. Arterial blood samples were analysed. Values for left-to-right and sternal-to-dorsal centre of ventilation (COV), lung compliances and Bohr dead space were calculated.

Results

Distribution of ventilation drifted leftward and dorsally during recruitment. Mean ± standard deviation (SD) values at baseline and highest airway pressures, respectively, were 49.9 ± 0.7% and 48.0 ± 0.6% for left-to-right COV (p = 0.009), and 46.3 ± 2.0% and 54.6 ± 2.0% for sternal-to-dorsal COV (p = 0.0001). Compliance of dependent lung regions and PaO2 increased, whereas compliance of non-dependent lung regions decreased during ARM and then returned to baseline (p < 0.001). Bohr dead space decreased after ARM (p = 0.007). Interestingly, PaO2 correlated to the compliance of the dependent lung (r2 = 0.71, p < 0.001).

Conclusions and clinical relevance

The proportion of tidal volume distributed to dependent and left lung regions increased during ARM, presumably as a result of opening atelectasis. Monitoring compliance of the dependent lung with EIT may substitute PaO2 measurements during ARM to identify an optimal PEEP.  相似文献   

9.
ObjectiveTo compare the efficacy of single-breath continuous positive airway pressure manoeuvre (CPAP-M) with inhaled salbutamol, and a combination of both.Study designRandomized, clinical study.AnimalsA total of 62 client-owned horses (American Society of Anesthesiologists status III–V) anaesthetized for laparotomy.MethodsHorses were premedicated with intravenous (IV) xylazine (0.4–0.6 mg kg–1), anaesthesia was induced with midazolam (0.06 mg kg–1 IV) and ketamine (2.2 mg kg–1 IV) and maintained with isoflurane in oxygen using volume-controlled ventilation without positive end-expiratory pressure. If PaO2 was < 100 mmHg (13.3 kPa), either a CPAP-M (50 cmH2O for 45 seconds) or salbutamol (0.002 mg kg–1) was administered. The intervention was considered successful if PaO2 reached 100 mmHg (13.3 kPa). If PaO2 remained < 100 mmHg (13.3 kPa), treatments were switched. PaO2/FiO2 ratio and estimated shunt fraction (F-shunt) were derived from data obtained from arterial blood gas measurements. Dynamic compliance (Cdyn) was calculated from variables recorded at the moment of arterial blood analysis. Fisher’s exact tests compared success rates between treatments, and linear models were performed to test whether the treatment modified the values of the measurements; p < 0.05.ResultsSalbutamol was the first intervention in 28 horses and was effective in 22 horses. CPAP-M was the first intervention in 34 horses and was effective in 26 horses. CPAP-M after salbutamol was performed in six horses, with four responders, and salbutamol after CPAP-M was administered to eight horses, with one responder. Salbutamol, but not CPAP-M, significantly decreased F-shunt. Both salbutamol and CPAP-M significantly increased Cdyn.Conclusions and clinical relevanceSalbutamol and CPAP-M were comparably effective in improving oxygenation and Cdyn in anaesthetized horses with PaO2 < 100 mmHg (13.3 kPa). Whether combining both treatments might be beneficial needs to be confirmed on a larger number of horses.  相似文献   

10.

Objective

To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period.

Study design

Prospective, randomized clinical trial.

Animals

A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency.

Methods

Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups Lat- CMV and Dors-CMV (each n = 12) were ventilated using CMV. Groups Lat-RM and Dors-RM (each n = 12) were ventilated using CMV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths with peak inspiratory pressure of 60 cmH2O, 80 cmH2O and 60 cmH2O, respectively). RMs were applied as required to maintain PaO2 at > 400 mmHg (> 53.3 kPa). Dobutamine was given to maintain mean arterial blood pressure at > 60 mmHg. Physiological parameters were recorded every 10 minutes. Arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova), t tests and the Mann–Whitney U-test.

Results

Horses in Dors-RM had higher PaO2 values [478 ± 35 mmHg (63.7 ± 4.6 kPa)] than horses in Dors-CMV [324 ± 45 mmHg (43.2 ± 6 kPa)] during anaesthesia and the early recovery period. There were no differences between horses in groups Lat-CMV and Lat-RM. Other measured parameters did not differ between groups.

Conclusions and clinical relevance

Ventilation with CMV, constant PEEP and interposed RM provided improved arterial oxygenation in horses in dorsal recumbency that lasted into the early recovery period, but had no benefit in horses in lateral recumbency. This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses, especially in dorsal recumbency.  相似文献   

11.
ObjectiveTo compare PaO2 and PaCO2 in horses recovering from general anesthesia maintained with either apneustic anesthesia ventilation (AAV) or conventional mechanical ventilation (CMV).Study designRandomized, crossover design.AnimalsA total of 10 healthy adult horses from a university-owned herd.MethodsDorsally recumbent horses were anesthetized with isoflurane in oxygen [inspired oxygen fraction = 0.3 initially, with subsequent titration to maintain PaO2 ≥ 85 mmHg (11.3 kPa)] and ventilated with AAV or CMV according to predefined criteria [10 mL kg–1 tidal volume, PaCO2 40–45 mmHg (5.3–6.0 kPa) during CMV and < 60 mmHg (8.0 kPa) during AAV]. Horses were weaned from ventilation using a predefined protocol and transferred to a stall for unassisted recovery. Arterial blood samples were collected and analyzed at predefined time points. Tracheal oxygen insufflation at 15 L minute–1 was provided if PaO2 < 60 mmHg (8.0 kPa) on any analysis. Time to oxygen insufflation, first movement, sternal recumbency and standing were recorded. Data were analyzed using repeated measures anova, paired t tests and Fisher’s exact test with significance defined as p < 0.05.ResultsData from 10 horses were analyzed. Between modes, PaO2 was significantly higher immediately after weaning from ventilation and lower at sternal recumbency for AAV than for CMV. No PaCO2 differences were noted between ventilation modes. All horses ventilated with CMV required supplemental oxygen, whereas three horses ventilated with AAV did not. Time to first movement was shorter with AAV. Time to oxygen insufflation was not different between ventilation modes.ConclusionsAlthough horses ventilated with AAV entered the recovery period with higher PaO2, this advantage was not sustained during recovery. Whereas fewer horses required supplemental oxygen after AAV, the use of AAV does not preclude the need for routine supplemental oxygen administration in horses recovering from general anesthesia.  相似文献   

12.
The cardiovascular effects of intravenously (iv) administered medetomidine 20 μg/kg bodyweight (bwt) and ketamine (2 mg/kgbwt), with and without 100% inspired oxygen, were investigated in six domestic sheep. A second dose of medetomidine and ketamine was administered iv, at dose 10 μg/kg bwt and 1 mg/kg bwt respectively, 25 minutes after the initial injection. Heart rate, PaO2 pH and haemoglobin saturation decreased whereas PaCO2 and base excess increased post-injection. Transient hypertension and an increase in respiration rate were evident within the first 10 minutes of anaesthesia. Significant hypoxaemia (P<0.01) developed in sheep breathing room air. Inspired 100% oxygen improved PaO2 (but the difference was not significant), and improved haemoglobin saturation significantly (P<0.05), however, this effect varied between individuals. One sheep breathing room air suffered a cardiac arrest immediately post-injection and had to be resuscitated. Atipamezole 125 μg/kg given intramuscularly 45 minutes after the initial injection rapidly reversed the effects of medetomidine. Recovery times did not significantly differ although time to extubation and standing tended to be longer in sheep breathing room air compared to the sheep breathing 100% oxygen. The quality of the recovery did not differ.  相似文献   

13.
Apneic oxygenation was studied in six ponies for 30 minutes, and six horses for 10 minutes. Arterial blood was sampled at regular intervals for measurement of oxygen and carbon dioxide tensions (PaO2 and PaCO2) and calculation of alveolar-arterial oxygen tension difference (PAO2-PaO2). In both groups of animals, PaO2 decreased rapidly during the first 3 minutes of apnea, then more slowly. Although the mean value was above 100 mmHg at 10 minutes, there was considerable inter-animal variability. Before apnea, PAO2-PaO2 was slightly, but not significantly, larger in horses than in ponies and increased in both groups during the first 3 minutes of apnea, after which the increase was slower. There was no significant difference between ponies and horses up to 10 minutes, suggesting that PAO2-PaO2 is independent of body size. In ponies, the PAO2-PaO2 did not change significantly between 10 and 30 minutes. Final PaO2 could not be correlated with initial PaO2 or initial PAO2-PaO2. The rate of rise of PAO2-PaO2 could not be predicted from baseline values. The rate of rise of PaCO2 was similar and fairly constant in ponies and horses, and did not contribute to the rapid initial decrease in PaO2. It appears that apneic oxygenation should not be used in the equine species, since it is impossible to predict in which animals the technique is safe for more than a few minutes.  相似文献   

14.
ObjectiveTo evaluate arterial oxygenation during the first 4 postoperative hours in dogs administered different fractions of inspired oxygen (FiO2) during general anesthesia with mechanical ventilation.Study designProspective, randomized clinical trial.AnimalsA total of 20 healthy female dogs, weighing >15 kg and body condition scores 3–7/9, admitted for ovariohysterectomy.MethodsDogs were randomized to breathe an FiO2 >0.9 or 0.4 during isoflurane anesthesia with intermittent positive pressure ventilation. The intraoperative PaO2:FiO2 ratio was recorded during closure of the linea alba. Arterial blood was obtained 5, 60 and 240 minutes after extubation for measurement of PaO2 and PaCO2 (FiO2 = 0.21). Demographic characteristics, duration of anesthesia, PaO2:FiO2 ratio and anesthetic agents were compared between groups with Wilcoxon tests. The postoperative PaO2, PaCO2, rectal temperature, a visual sedation score and events of hypoxemia (PaO2 < 80 mmHg) were compared between groups with mixed-effects models or generalized linear mixed models.ResultsGroups were indistinguishable by demographic characteristics, duration of anesthesia, anesthetic agents administered and intraoperative PaO2:FiO2 ratio (all p > 0.08). Postoperative PaO2, PaCO2, rectal temperature or sedation score were not different between groups (all p > 0.07). During the first 4 postoperative hours, hypoxemia occurred in three and seven dogs that breathed FiO2 >0.9 or 0.4 during anesthesia, respectively (p = 0.04).Conclusions and clinical relevanceThe results identified no advantage to decreasing FiO2 to 0.4 during anesthesia with mechanical ventilation with respect to postoperative oxygenation. Moreover, the incidence of hypoxemia in the first 4 hours after anesthesia was higher in these dogs than in dogs breathing FiO2 >0.9.  相似文献   

15.
ObjectiveTo determine the effect of fraction of inspired oxygen (FiO2) on intrapulmonary shunt fraction as measured by F-shunt in ponies during isoflurane anaesthesia.Study designProspective, randomized clinical study.AnimalsA group of 23 adult Shetland ponies undergoing a total of 32 anaesthetic procedures.MethodsPonies were premedicated intravenously (IV) with detomidine (0.01 mg kg–1) and either morphine (0.1 mg kg–1) or butorphanol (0.02 mg kg–1). Anaesthesia was induced with ketamine (2.2 mg kg–1) and midazolam (0.07 mg kg–1) administered IV. Ponies were randomly allocated to maintenance of anaesthesia with isoflurane in oxygen (group TH; FiO2 = 0.95) or a mixture of oxygen and medical air (group TL; FiO2 = 0.65); all ponies were given a constant rate of infusion of detomidine. Animals were mechanically ventilated to maintain PaCO2 between 40 and 50 mmHg. Arterial blood gas analysis was performed every 30 minutes. The F-shunt equation was calculated for each time point T0, T30, T60 and T90. Data were analysed using linear mixed model analysis and presented as mean ± standard deviation (p < 0.05).ResultsPaO2 was greater in group TH than in group TL (TH: 406 ± 90, 438 ± 83, 441 ± 69 and 464 ± 53 mmHg versus TL: 202 ± 90, 186 ± 84, 172 ± 85 and 191 ± 98 mmHg at T0, T30, T60 and T90, respectively; p < 0.0001). In TH, F-shunt was < TL. Significant differences were found at T60 (TH: 13.2% ± 4.3 versus TL: 19.4% ± 8.3; p = 0.016) and T90 (TH: 11.7% ± 3.5 versus TL: 18.6% ± 9.5; p = 0.036).Conclusions and clinical relevanceOur findings do not support a beneficial effect of using a reduced FiO2 to improve oxygenation in anaesthetized and mechanically ventilated Shetland ponies.  相似文献   

16.

Objective

To compare static compliance (Cst) and alveolar–arterial oxygen tension difference [P(a–a)O2] between positive end-expiratory pressures (PEEP) of 7, 12 and 17 cmH2O applied after an alveolar recruitment maneuver (RM) in isoflurane-anesthetized horses.

Study design

Prospective, randomized, clinical study.

Animals

A group of 30 healthy adult horses undergoing arthroscopic surgery.

Methods

Animals in dorsal recumbency and mechanically ventilated with a tidal volume of 14 mL kg?1 and 7 cmH2O PEEP (control; n = 6) were subjected to an RM by increasing PEEP from 7 to 22 cmH2O in 5 cmH2O increments at 5 minute intervals, and then decreased similarly to PEEP of 17 (RM17; n = 8), 12 (RM12; n = 8) or 7 cmH2O (RM7; n = 8). Cst and P(a–a)O2 were assessed prior to (baseline) and after the RM at 5, 10, 15, 20, 40, 60 and 80 minutes after achieving each target PEEP, and during recovery from anesthesia.

Results

Post-RM improvements on P(a–a)O2 were maintained (baseline versus 80 minutes) in RM12 [216 ± 77 mmHg (28.8 ± 10.3 kPa) versus 194 ± 39 mmHg (25.9 ± 5.2 kPa)] and RM17 [180 ± 86 mmHg (24.0 ± 11.6 kPa) versus 136 ± 75 mmHg [18.2 ± 10.0 kPa]). The improvements on Cst were maintained only in RM12 (0.80 ± 0.13 versus 0.98 ± 0.13 mL cmH2O?1 kg?1). No such improvements were observed in RM7 and control. No significant differences were observed between groups during recovery from anesthesia.

Conclusions

and clinical relevance The 12 and 17 cmH2O PEEP can be used to maintain the improvements on P(a–a)O2 obtained after an RM. Only 12 cmH2O PEEP maintained the post-RM increase on Cst. Such variables were not influenced by the 7 cmH2O PEEP.  相似文献   

17.
ObjectiveTo determine if pressure support ventilation (PSV) weaning from general anesthesia affects ventilation or oxygenation in horses.Study designProspective randomized clinical study.AnimalsTwenty client‐owned healthy horses aged 5 ± 2 years, weighing 456 ± 90 kg.MethodsIn the control group (CG; n = 10) weaning was performed by a gradual decrease in respiratory rate (fR) and in the PSV group (PSVG; n = 10) by a gradual decrease in fR with PSV. The effect of weaning was considered suboptimal if PaCO2 > 50 mmHg, arterial pH < 7.35 plus PaCO2 > 50 mmHg or PaO2 < 60 mmHg were observed at any time after disconnection from the ventilator until 30 minutes after the horse stood. Threshold values for each index were established and the predictive power of these values was tested.ResultsPressure support ventilation group (PSVG) had (mean ± SD) pH 7.36 ± 0.02 and PaCO2 41 ± 3 mmHg at weaning and the average lowest PaO2 69 ± 6 mmHg was observed 15 minutes post weaning. The CG had pH 7.32 ± 0.02 and PaCO2 57 ± 6 mmHg at weaning and the average lowest PaO2 48 ± 5 mmHg at 15 minutes post weaning. No accuracy in predicting weaning effect was observed for fR (p = 0.3474), minute volume (p = 0.1153), SaO2 (p = 0.1737) and PaO2/PAO2 (p = 0.1529). A high accuracy in predicting an optimal effect of weaning was observed for VT > 10 L (p = 0.0001), fR/VT ratio ≤ 0.60 breaths minute?1 L?1 (p = 0.0001), VT/bodyweight > 18.5 mL kg?1 (p = 0.0001) and PaO2/FiO2 > 298 (p = 0.0002) at weaning. A high accuracy in predicting a suboptimal effect of weaning was observed for VT < 10 L (p = 0.0001), fR/VT ratio ≥ 0.60 breaths minute?1 L?1 (p = 0.0001) and Pe′CO2 ≥ 38 mmHg (p = 0.0001) at weaning.Conclusions and clinical relevancePressure support ventilation (PSV) weaning had a better respiratory outcome. A higher VT, VT/body weight, PaO2/FiO2 ratio and a lower fR/VT ratio and Pe′CO2 were accurate in predicting the effect of weaning in healthy horses recovering from general anesthesia.  相似文献   

18.

Objective

To evaluate the effects of an alveolar recruitment maneuver (ARM) followed by 5 cmH2O positive end-expiratory pressure (PEEP) in dogs undergoing laparoscopy.

Study design

Prospective, randomized clinical study.

Animals

A group of 20 dogs undergoing laparoscopic ovariectomy.

Methods

Dogs were sedated with acepromazine and methadone intramuscularly; anesthesia was induced with propofol intravenously and maintained with inhaled isoflurane. The following baseline ventilatory setting (BVS) was administered: tidal volume of 12 mL kg–1, inspiratory to expiratory ratio of 1:2, inspiratory pause 25% of inspiratory time, no PEEP and a respiratory rate to maintain end-tidal carbon dioxide tension between 5.3 and 7.3 kPa. Then, 10 minutes after the pneumoperitoneum, 10 dogs (RM) underwent a sustained inflation ARM followed by BVS plus 5 cmH2O PEEP, while 10 dogs (NO-RM) were left with BVS throughout the procedure. Gas exchange and respiratory system mechanics were evaluated before the pneumoperitoneum (PPpre), before ARM (PP10), 30 minutes later (PP30) and 20 minutes after pneumoperitoneum discontinuation (PPpost20). Data were analyzed using anova (p < 0.05).

Results

The Fshunt at PP30 and PPpost20 was lower (p < 0.001) in the RM (2.3 ± 2.2 and 4.7 ± 3.7%) than in the NO-RM (5.2 ± 2.1 and 11.1 ± 5.2%), and PaO2 at PP30 and PPpost20 was higher (p < 0.001) in the RM (67.3 ± 4.2 and 60.1 ± 9.4 kPa) than in the NO-RM (50.2 ± 7.4 and 45.5 ± 11.1 kPa). Static compliance of the respiratory system at PP30 and PPpost20 was greater (p < 0.001) in the RM (2.4 ± 0.2 and 2.1 ± 0.4 mL cmH2O?1 kg–1) than in the NO-RM (0.9 ± 0.4 and 1.2 ± 0.2 mL cmH2O?1 kg–1).

Conclusions and clinical relevance

In dogs undergoing laparoscopy, ARM followed by 5 cmH2O PEEP improves gas exchange and respiratory system mechanics.  相似文献   

19.
20.
ObjectiveTo evaluate the impact of a 30% end-inspiratory pause (EIP) on alveolar tidal volume (VTalv), airway (VDaw) and physiological (VDphys) dead spaces in mechanically ventilated horses using volumetric capnography, and to evaluate the effect of EIP on carbon dioxide (CO2) elimination per breath (Vco2br–1), PaCO2, and the ratio of PaO2-to-fractional inspired oxygen (PaO2:FiO2).Study designProspective research study.AnimalsA group of eight healthy research horses undergoing laparotomy.MethodsAnesthetized horses were mechanically ventilated as follows: 6 breaths minute–1, tidal volume (VT) 13 mL kg–1, inspiratory-to-expiratory time ratio 1:2, positive end-expiratory pressure 5 cmH2O and EIP 0%. Vco2br–1 and expired tidal volume (VTE) of 10 consecutive breaths were recorded 30 minutes after induction, after adding 30% EIP and upon EIP removal to construct volumetric capnograms. A stabilization period of 15 minutes was allowed between phases. Data were analyzed using a mixed-effect linear model. Significance was set at p < 0.05.ResultsThe EIP decreased VDaw from 6.6 (6.1–6.7) to 5.5 (5.3–6.1) mL kg–1 (p < 0.001) and increased VTalv from 7.7 ± 0.7 to 8.6 ± 0.6 mL kg–1 (p = 0.002) without changing the VTE. The VDphys to VTE ratio decreased from 51.0% to 45.5% (p < 0.001) with EIP. The EIP also increased PaO2:FiO2 from 393.3 ± 160.7 to 450.5 ± 182.5 mmHg (52.5 ± 21.4 to 60.0 ± 24.3 kPa; p < 0.001) and Vco2br–1 from 0.49 (0.45–0.50) to 0.59 (0.45–0.61) mL kg–1 (p = 0.008) without reducing PaCO2.Conclusions and clinical relevanceThe EIP improved oxygenation and reduced VDaw and VDphys, without reductions in PaCO2. Future studies should evaluate the impact of different EIP in healthy and pathological equine populations under anesthesia.  相似文献   

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