Ultrasound-Guided Greater Ischiatic Notch Plane Block Combined with the Caudal Quadratus Lumborum Block (GIN-TONIC Block) in Dogs Undergoing Pelvic Limb Surgery: Preliminary Results.

This study assessed the analgesic and motor effects of the GIN-TONIC block, a combination of the greater ischiatic notch plane block and the caudal lateral quadratus lumborum block, in 24 dogs undergoing pelvic limb surgery. Dogs were randomly divided into two equal groups: GA received acepromazine [(20 µg kg-1 intravenously (IV)] as premedication, and GD received dexmedetomidine (2 µg kg-1 IV). General anesthesia was maintained with isoflurane, and both groups received a GIN-TONIC block using 2% lidocaine. Nociception during surgery and postoperative pain [assessed using the Glasgow Composite Measure Pain Score (GCMPS-SF)] were assessed. Fentanyl (2 µg kg-1 IV) was administered if nociception was noted and morphine (0.5 mg kg-1 IV) was administered during recovery if the pain scores exceeded the predefined threshold. Motor function was assessed during the recovery period using descriptors previously reported. All dogs received analgesics at the 4 h mark before being discharged. Three and two dogs in GD and GA required fentanyl once. Postoperative pain scores remained ≤4/20 for all dogs except one. Dogs achieved non-ataxic ambulation within 38.9 ± 10.3 and 35.1 ± 11.1 min after extubation in GD and GA, respectively. This study highlighted the potential of the GIN-TONIC block as a feasible regional anesthesia method for delivering perioperative analgesia in dogs undergoing pelvic limb orthopedic surgery.

Ultrasound-guided lateral pericapsular hip desensitization of the articular branches of the cranial gluteal nerve: A canine cadaveric study and feasibility study in dogs.

OBJECTIVE: To develop and assess the feasibility, as a diagnostic block, of an ultrasound-guided lateral pericapsular hip desensitization (L-PHD) technique in dogs. STUDY DESIGN: Prospective, randomized, anatomical and feasibility study. ANIMALS: A total of 11 canine cadavers and eight adult dogs scheduled for acetabular surgical denervation. METHODS: After studying the ultrasound anatomy of the lateral aspect of the gluteal region and determining an acoustic window to perform an ultrasound-guided L-PHD in three canine cadavers, the right and left hemipelves of eight canine cadavers were injected in the interfascial plane located lateral (LL-PHD group) or medial (LM-PHD group) to the deep gluteal muscle, with 0.05 mL kg-1 of dye per hip on each cadaver. The staining of the pericapsular nerves was assessed by anatomical dissection. Then, the LM-PHD was performed using 2% lidocaine as a diagnostic block in dogs scheduled for acetabular surgical denervation. Positive predictive value (PPV) was calculated for those animals who had favorable outcomes after acetabular surgical denervation. RESULTS: The ultrasound-guided LL-PHD and LM-PHD could be performed by inserting the needle lateral and medial to the deep gluteal muscle. Ultrasound-guided LL-PHD stained the cranial gluteal nerve and its muscular branches in all injections and partially stained the lumbosacral trunk in two out of eight cadavers. The LM-PHD selectively stained the articular branches of the cranial gluteal nerve in all but one cadaver. The PPV for LM-PHD successful test prediction was 85.7% (95% confidence interval: 48.6% to 98.6%). CONCLUSIONS: and clinical significance Ultrasound-guided LM-PHD using 0.05 mL kg-1 of dye selectively stained the articular branches of the cranial gluteal nerve in canine cadavers. The LM-PHD technique is feasible and could be used as a diagnostic block before acetabular surgical denervation in dogs.

Ventilator output splitting interface 'ACRA': Description and evaluation in lung simulators and in an experimental ARDS animal model.

The current COVID-19 pandemic has led the world to an unprecedented global shortage of ventilators, and its sharing has been proposed as an alternative to meet the surge. This study outlines the performance of a preformed novel interface called 'ACRA', designed to split ventilator outflow into two breathing systems. The 'ACRA' interface was built using medical use approved components. It consists of four unidirectional valves, two adjustable flow-restrictor valves placed on the inspiratory limbs of each unit, and one adjustable PEEP valve placed on the expiratory limb of the unit that would require a greater PEEP. The interface was interposed between a ventilator and two lung units (phase I), two breathing simulators (phase II) and two live pigs with heterogeneous lung conditions (phase III). The interface and ventilator adjustments tested the ability to regulate individual pressures and the resulting tidal volumes. Data were analyzed using Friedman and Wilcoxon tests test (p < 0.05). Ventilator outflow splitting, independent pressure adjustments and individual tidal volume monitoring were feasible in all phases. In all experimental measurements, dual ventilation allowed for individual and tight adjustments of the pressure, and thus volume delivered to each paired lung unit without affecting the other unit's ventilation-all the modifications performed on the ventilator equally affected both paired lung units. Although only suggested during a dire crisis, this experiment supports dual ventilation as an alternative worth to be considered.

Effect of PEEP on Dead Space in an Experimental Model of ARDS.

BACKGROUND: The difference between Bohr and Enghoff dead space are not well described in ARDS patients. We aimed to analyze the effect of PEEP on the Bohr and Enghoff dead spaces in a model of ARDS. METHODS: 10 pigs submitted to randomized PEEP steps of 0, 5, 10, 15, 20, 25 and 30 cm H2O were evaluated with the use of lung ultrasound images, alveolar-arterial oxygen difference (P(A-a)O2 ), transpulmonary mechanics, and volumetric capnography at each PEEP step. RESULTS: At PEEP ≥ 15 cm H2O, atelectasis and P(A-a)O2 progressively decreased while end-inspiratory transpulmonary pressure (PL), end-expiratory PL, and driving PL increased (all P < .001). Bohr dead space (VDBohr /VT), airway dead space (VDaw /VT), and alveolar dead space (VDalv /VTalv ) reached their highest values at PEEP 30 cm H2O (0.69 ± 0.10, 0.53 ± 0.13 and 0.35 ± 0.06, respectively). At PEEP <15 cm H2O, the increases in atelectasis and P(A-a)O2 were associated with negative end-expiratory PL and highest driving PL. VDBohr /VT and VDaw /VT showed the lowest values at PEEP 0 cm H2O (0.51 ± 0.08 and 0.32 ± 0.08, respectively), whereas VDalv /VTalv increased to 0.27 ± 0.05. Enghoff dead space and its derived VDalv /VTalv showed high values at low PEEPs (0.86 ± 0.02 and 0.79 ± 0.04, respectively) and at high PEEPs (0.84 ± 0.04 and 0.65 ± 0.12), with the lowest values at 15 cm H2O (0.77 ± 0.05 and 0.61 ± 0.11, respectively; all P < .001). CONCLUSIONS: Bohr dead space was associated with lung stress, whereas Enghoff dead space was partially affected by the shunt effect.

The use of electrical stimulation to guide epidural and intrathecal needle advancement at the L5 -L6 intervertebral space in dogs.

OBJECTIVE: To determine the minimal electrical threshold (MET) necessary to elicit appropriate muscle contraction when the tip of an insulated needle is positioned epidurally or intrathecally at the L5-6 intervertebral space (phase-I) and to determine whether the application of a fixed electrical current during its advancement could indicate needle entry into the intrathecal space (phase-II) in dogs. STUDY DESIGN: Prospective, blinded study. ANIMALS: Thirteen (phase-I) and seventeen (phase-II) dogs, scheduled for a surgical procedure where L5-6 intrathecal administration was indicated. METHODS: Under general anesthesia, an insulated needle was first inserted into the L5-6 epidural space and secondly into the intrathecal space and the MET necessary to obtain a muscular contraction of the pelvic limb or tail at each site was determined (phase-I). Under similar conditions, in dogs of phase-II an insulated needle was inserted through the L5-6 intervertebral space guided by the use of a fixed electrical current (0.8 mA) until muscular contraction of the pelvic limb or tail was obtained. Intrathecal needle placement was confirmed by either free flow of cerebrospinal fluid (CSF) or myelography. RESULTS: The current required to elicit a motor response was significantly lower (p < 0.0001) when the tip of the needle was in the intrathecal space (0.48 ± 0.10 mA) than when it was located epidurally (2.56 ± 0.57). The use of a fixed electrical stimulation current of 0.8 mA resulted in correct prediction of intrathecal injection, corroborated by either free flow of CSF (n = 12) or iohexol distribution pattern (n = 5), in 100% of the cases. CONCLUSION AND CLINICAL RELEVANCE: Nerve stimulation may be employed as a tool to distinguish epidural from intrathecal insulated needle position at the L5-6 intervertebral space in dogs. This study demonstrates the feasibility of using an electrical stimulation test to confirm intrathecal needle position in dogs.

Use of electrical stimulation to monitor lumbosacral epidural and intrathecal needle placement in rabbits.

OBJECTIVE: To determine the minimal electric threshold of neurostimulation dorsally and ventrally to the interarcuate ligament in the lumbosacral area necessary to cause muscle contraction of the hind limb or tail and determine whether a continuous electrical stimulation applied to an insulated needle during lumbosacral epidural needle placement could be used to distinguish the epidural from the intrathecal space in rabbits. ANIMALS: 24 New Zealand white rabbits. PROCEDURES: Rabbits received iohexol (0.2 mL/kg) either dorsally (group 1) or ventrally to the interarcuate ligament in the lumbosacral area (groups 2 and 3). Correct placement of the needle was determined by use of the loss of resistance to injection technique (group 2) or a continuous electrical stimulation (group 3) and confirmed by examination of the iohexol distribution pattern on radiographs. RESULTS: In all rabbits of group 1, iohexol was injected in the lumbosacral area, outside the epidural space. In groups 2 and 3, iohexol was injected intrathecally. No pure iohexol epidural migration of iohexol was observed. Mean ± SD minimal electric threshold to elicit a motor response was 1.2 ± 0.3 mA, 0.3 ± 0.1 mA, and 0.3 ± 0.1 mA in groups 1, 2, and 3, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Neurostimulation was a useful technique to determine correct intrathecal needle placement in rabbits but failed to detect the lumbosacral epidural space when the common technique, used in dogs and cats for the lumbosacral epidural approach, was used.