Inconsistent Methods Used to Set Airway Pressure Release Ventilation in Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Regression Analysis

Airway pressure release ventilation (APRV) is a protective mechanical ventilation mode for patients with acute respiratory distress syndrome (ARDS) that theoretically may reduce ventilator-induced lung injury (VILI) and ARDS-related mortality. However, there is no standard method to set and adjust the APRV mode shown to be optimal. Therefore, we performed a meta-regression analysis to evaluate how the four individual APRV settings impacted the outcome in these patients. Methods: Studies investigating the use of the APRV mode for ARDS patients were searched from electronic databases. We tested individual settings, including (1) high airway pressure (PHigh); (2) low airway pressure (PLow); (3) time at high airway pressure (THigh); and (4) time at low pressure (TLow) for association with PaO2/FiO2 ratio and ICU length of stay. Results: There was no significant difference in PaO2/FiO2 ratio between the groups in any of the four settings (PHigh difference -12.0 [95% CI -100.4, 86.4]; PLow difference 54.3 [95% CI -52.6, 161.1]; TLow difference -27.19 [95% CI -127.0, 72.6]; THigh difference -51.4 [95% CI -170.3, 67.5]). There was high heterogeneity across all parameters (PhHgh I2 = 99.46%, PLow I2 = 99.16%, TLow I2 = 99.31%, THigh I2 = 99.29%). Conclusions: None of the four individual APRV settings independently were associated with differences in outcome. A holistic approach, analyzing all settings in combination, may improve APRV efficacy since it is known that small differences in ventilator settings can significantly alter mortality. Future clinical trials should set and adjust APRV based on the best current scientific evidence available.

A proposed rescue transesophageal echocardiographic protocol for anesthetized dogs

OBJECTIVE

To describe the acquisition and pitfalls of a 3-view transesophageal echocardiography (TEE) protocol in anesthetized, dorsally recumbent dogs.

ANIMALS

8 beagles, 1 to 2 years old, 7.4 to 11.2 kg.

METHODS

Dogs were anesthetized, mechanically ventilated, and placed in dorsal recumbency. A TEE probe was advanced, and 3 views were performed: midesophageal 4-chamber and long axis (ME 4C and ME LAX) and caudal esophageal short axis (CE SAX) at the level of the papillary muscles. Probe insertion depth, flexion, omniplane angle, and image acquisition time were recorded. Two observers assessed 24 video clips each and identified anatomical structures.

RESULTS

The ME 4C and ME LAX were obtained at 35 (30 to 40) cm insertion depth, omniplane at 0° and 103° (90 to 116), respectively. Views were obtained in ≤30 seconds once the TEE was in the cervical esophagus. Left-sided structures were identified in all cases, whereas right-sided structures were not always simultaneously obtained in the ME 4C, requiring further probe manipulation. All structures were identified on ME LAX. CE SAX was obtained at 40 (35 to 45) cm, omniplane at 0°, and in 15 (10 to 90) seconds. A true SAX view (circular left ventricle at the level of papillary muscles) could not be obtained in all dogs.

CLINICAL RELEVANCE

A 3-view TEE protocol using core views as those described in humans may be applicable to dogs under general anesthesia and in dorsal recumbency. The CE SAX view at the level of the papillary muscles appears more difficult to obtain with consistency than midesophageal views.

The Latest in Resuscitation Research: Highlights From the 2022 American Heart Association's Resuscitation Science Symposium

BACKGROUND

Every year the American Heart Association's Resuscitation Science Symposium (ReSS) brings together a community of international resuscitation science researchers focused on advancing cardiac arrest care.

METHODS AND RESULTS

The American Heart Association's ReSS was held in Chicago, Illinois from November 4th to 6th, 2022. This annual narrative review summarizes ReSS programming, including awards, special sessions and scientific content organized by theme and plenary session.

CONCLUSIONS

By exploring both the science of resuscitation and important related topics including survivorship, disparities, and community-focused programs, this meeting provided important resuscitation updates.

Duration of neuromuscular block is more variable and recovery time is shorter with rocuronium than cisatracurium in anesthetized dogs

OBJECTIVE

To compare the variability in the duration of action of a single dose of rocuronium or cisatracurium, and duration of subsequent top-up doses in anesthetized dogs.

ANIMALS

Thirty dogs requiring ophthalmic surgery with neuromuscular block.

PROCEDURES

Neuromuscular function was monitored with train-of-four (TOF) and acceleromyography. Dogs received an initial dose of rocuronium 0.6 mg/kg, or cisatracurium 0.15 mg/kg IV, which produced complete neuromuscular block. Upon return of the first response (T1) of TOF, a third of the initial dose was repeated. The duration of the initial dose and its variability were compared between agents. Duration of subsequent top-up doses was assessed with mixed effect models. Spontaneous (from last return of T1) or neostigmine-enhanced (from administration to complete recovery) recovery times were measured for each agent.

RESULTS

Duration of action of the initial dose was [median (range)] 25 (10-60) min with rocuronium and 35 (15-45) min with cisatracurium (p = .231). The variability of rocuronium was 3.25 times larger than cisatracurium (p = .034). Duration of top-up doses did not vary for either agent. Spontaneous recovery was shorter for rocuronium [15 (10-20) min] than cisatracurium [25 (15-45) min] (p = .02). Neostigmine-enhanced recovery times were 5 (5-25) for rocuronium and 10 (5-10) for cisatracurium (p = .491).

CONCLUSIONS

Duration of action for a single dose is significantly more variable with rocuronium than cisatracurium. Time to spontaneous recovery was longer for cisatracurium, and cases of unexpectedly long recovery times were observed with both agents. Objective monitoring is recommended.

A flexible endotracheal tube introducer improves first-attempt success of intubation in cats by novice anesthetists

OBJECTIVE

To test whether the use of a flexible endotracheal tube introducer (ETI) facilitates intubation of cats by veterinary students with little or no experience.

ANIMALS

125 healthy cats.

PROCEDURES

Cats were sedated with dexmedetomidine and morphine IM, and anesthesia was induced with propofol. They were randomly assigned to be intubated by supervised veterinary students using an ETI within a tracheal tube or an endotracheal tube alone (3.0, 3.5, or 4.0 internal diameter sizes). Success rate at first attempt, number of attempts to intubate (up to 3), and time to intubate were recorded. Multivariate logistic regression was used to test associations between several factors such as use of an ETI, cat’s weight, endotracheal tube size, administration of ketamine for sedation, and first-attempt success. Significance was considered when P < 0.05.

RESULTS

Success rate for the first attempt was higher with an ETI (79% [51/64) than without it (46% [28/61]), and attempts to intubate were fewer when an ETI was used (both P < 0.001). Time to intubate did not differ between groups (ETI, 30 seconds [4 to 143 seconds]; endotracheal tube, 28 seconds [5 to 180 seconds]). Use of an ETI was positively associated with improved first-attempt success, and the 3.0-mm internal diameter of the tube was negatively associated (both P ≤ 0.001).

CLINICAL RELEVANCE

The use of a flexible ETI improved the success of first-attempt intubation of cats by veterinary students. This technique may help minimize the number of attempts during intubation and incidence of complications that could arise from multiple attempts.

Evaluation of noninvasive blood pressure in anesthetized horses: Bias, limits of agreement, and comparative detection of a predetermined mean blood pressure warranting treatment

Oscillometric blood pressure monitoring may be a practical tool for short procedures or those performed outside of the operating room. Oscillometric and direct blood pressure values in 30 juvenile and adult horses in a clinical setting using mixed effect models were compared. The limits of agreement and percentage errors were also calculated. We evaluated the sensitivity and false positive rate for the oscillometric method to trigger an intervention for treating blood pressure [direct mean arterial pressure (MAP) < 70 mmHg]. Oscillometric MAP and diastolic arterial pressure (DAP) differed from direct values (P < 0.001); systolic arterial pressure (SAP) did not (P = 0.08). Wide limits of agreement were observed. Percentage errors were smaller for SAP (39%) than for MAP and DAP (48% and 72%). The oscillometric monitor indicated there was a requirement for blood pressure treatment with a true positive rate of 82%, consequently, it failed 18% of the times. The false positive rate (unnecessary treatment) was 55%.

Evaluation of the effects of helmet continuous positive airway pressure on laryngeal size in dogs anesthetized with propofol and fentanyl using computed tomography

OBJECTIVE

To evaluate the effect of 5 cm H₂ O of continuous positive airway pressure (CPAP) on laryngeal size in spontaneously breathing anesthetized dogs via computed tomography (CT).

DESIGN

Prospective, randomized, cross-over clinical study.

SETTING

University teaching hospital and referral private practice.

ANIMALS

Eight healthy client-owned dogs undergoing CT.

INTERVENTIONS

Dogs were sedated with acepromazine 20 μg/kg IM and induced with fentanyl 2 μg/kg and propofol 3-5 mg/kg IV before being maintained on fentanyl (5 μg/kg/h) and propofol (0.3 mg/kg/min) constant rate infusion. Dogs received an air/oxygen mixture with (CPAP) and without (NO-CPAP) 5 cm H₂ O of CPAP in a random order. Each study step lasted 15 minutes.

MEASUREMENTS AND MAIN RESULTS

Ten minutes after the beginning of each study period, a CT scan of the laryngeal region was obtained at end-expiration. CT images were analyzed to determine the laryngeal cross-sectional area (CSA; cm² ), total volume (V_TOT ; cm³ ), and laterolateral and dorsoventral diameters (D_LL and D_DV , respectively; cm). Differences between the 2 treatments were analyzed with t-test for paired data (P < 0.05). Compared to the NO-CPAP, during CPAP the CSA increased by 53.3 ± 23.1% (ie, from 3.3 ± 0.8 to 5.1 ± 1.3 cm² , P = 0.0004), V_TOT increased by 52.4 ± 13.6% (from 6.2 ± 1.7 to 9.4 ± 2.4 cm³ , P < 0.0001), and D_LL and D_DV were 55.5 ± 13.3% (3.6 ± 0.8 vs 2.4 ± 0.5 cm, P = 0.006) and 20.3 ± 8.8% larger (3.2 ± 0.7 vs 2.7 ± 0.6 cm, P = 0.0002), respectively.

CONCLUSIONS

Laryngeal volume and cross sectional area increased during the application of 5 cm H₂ O of helmet CPAP in spontaneously breathing anesthetized dogs.

Effects of positive end-expiratory pressure alone or an open-lung approach on recruited lung volumes and respiratory mechanics of mechanically ventilated horses

OBJECTIVE

To evaluate the effects of positive end-expiratory pressure (PEEP) alone and PEEP preceded by lung recruitment manoeuvre (LRM) on lung volumes and respiratory system mechanics in healthy horses undergoing general anaesthesia.

STUDY DESIGN

Controlled, prospective clinical study.

ANIMALS

A group of 15 horses undergoing arthroscopy.

METHODS

Following anaesthetic induction, initial ventilatory settings were: tidal volume 15 mL kg^-1, inspiratory:expiratory ratio 1:2, respiratory rate to maintain end-tidal CO₂ between 5.3-6.6 kPa (40-50 mmHg). The following settings were implemented sequentially: zero PEEP (ZEEP); PEEP 10 cmH₂O (PEEP); LRM (50 cmH₂O for 20 seconds) followed by 10 cmH₂O of PEEP (LRM + PEEP). Static compliance (C_st), driving pressure, delta end-expiratory (ΔEELV) and recruited lung volumes (RLV) were obtained 30 minutes after initiating each ventilatory strategy. Data were analyzed with paired t test or analysis of variance followed by Tukey's post hoc test. Data are shown as mean ± standard deviation; p < 0.05 was considered significant.

RESULTS

PEEP induced ΔEELV of 6.68 ± 3.36 mL kg^-1; ΔEELV during LRM + PEEP was 14.28 ± 5.59 mL kg^-1 (p < 0.0001). The RLV was greater during the LRM + PEEP phase (12.30 ± 5.85 mL kg^-1) than during PEEP (4.47 ± 3.97 mL kg^-1; p < 0.0001). The C_st was unchanged from ZEEP to PEEP (0.75 ± 0.21 and 0.85 ± 0.22 mL cmH₂O^-1 kg^-1, respectively, p = 0.36) but increased using LRM + PEEP (1.11 ± 0.25 mL cmH₂O^-1 kg^-1, p = 0.0004). Driving pressure was lower during LRM + PEEP than during PEEP and ZEEP (16 ± 2, 19 ± 2 and 21 ± 4 cmH₂O, respectively, p < 0.0001).

CONCLUSIONS AND CLINICAL RELEVANCE

Unlike PEEP alone, PEEP preceded by LRM increased RLV and C_st and reduced driving pressure in horses under anaesthesia.