Effect of fentanyl constant-rate infusions with or without medetomidine on the minimum infusion rate of propofol required to prevent motor movement in dogs

Propofol is a potential injectable anesthetic agent used in total intravenous anesthesia. However, the sparing effect of fentanyl and medetomidine on the required propofol dose in dogs remains unclear. We aimed to investigate the effect of fentanyl constant-rate infusion (CRI) with or without medetomidine on the minimum infusion rate of propofol required to prevent motor movement (MIRNM) in dogs. Six healthy purpose-bred dogs were anesthetized on three occasions with propofol alone (loading dose [LD], 8 mg/kg to effect; initial infusion rate [IR], 0.70 mg/kg/min); propofol (LD, 6 mg/kg to effect; IR, 0.35 mg/kg/min) and fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min); or propofol (LD, 4 mg/kg to effect; IR, 0.25 mg/kg/min), fentanyl (LD, 2 µg/kg; IR, 0.10 µg/kg/min), and medetomidine (LD, 2 µg/kg; IR, 0.5 µg/kg/hr) under controlled ventilation. The MIRNM was determined by observing the response to a noxious electrical stimulus. Heart rate, blood pressure, and blood gas analyses were performed at 1, 2, 3, and 4 hr after initiating CRI. The MIRNM (mean [range]) was significantly lower in the propofol-fentanyl-medetomidine group (0.16 [0.10-0.27] mg/kg/min) than that in the propofol-alone group (0.63 [0.47-0.82] mg/kg/min) (P=0.0004). Fentanyl combined with medetomidine did not significantly decrease the mean arterial pressure in dogs receiving propofol CRI 1-3 hr after initiating CRI compared with propofol CRI alone (P>0.9999, P=0.1536, and P=0.0596, respectively), despite inducing a significantly lower heart rate.

Dosage effect of cisatracurium on intubation and intraoperative neuromonitoring during thyroidectomy: a randomized controlled trial

Background

Intraoperative neuromonitoring (IONM) reduces the risk of recurrent laryngeal nerve (RLN) injury during thyroid surgery. However, the use of neuromuscular blocking agents (NMBAs), which are essential to improve intubation conditions, may hinder the electromyographic response during IONM. The aim of this prospective, double-blind, randomized controlled trial was to explore the optimal dosage of cisatracurium to produce adequate muscle relaxation for tracheal intubation without significantly affecting evoked potentials of IONM during thyroidectomy.

Methods

Patients undergoing thyroidectomy with IONM in our institution, with an American Society of Anesthesiologists grade of I-II, aged 18-75 years, and with a body mass index below 32 kg/m² were enrolled and randomly assigned (by random numbers) to receive 1× (group C1) or 2× (group C2) the effective dose (ED₉₅) of cisatracurium for tracheal intubation. The patients, surgeons, and anesthesiologists in charge were blinded to group assignment. Anesthesia was induced with sufentanil, propofol, and cisatracurium (0.05 mg/kgin group C1, 0.1 mg/kg in group C2). Ease of intubation was evaluated with the intubation condition score (Cooper score) and the intubation difficulty scale (IDS). Amplitudes of evoked potentials during intermittent IONM were compared between groups. The primary outcomes were the Cooper score, the IDS score, and the evoked potentials of IONM.

Results

Fifty-three patients were randomized from October 2019 to November 2020, and 52 were analyzed (with 26 patients in each group). The Cooper score was significantly lower in group C1 [median, 8.0 (interquartile range, 7.0-8.3)] than in group C2 [9.0 (9.0-9.0), P<0.001]. The rate of difficult laryngoscopy without external laryngeal pressure was significantly higher in group C1 than in group C2 (61.5% vs. 11.5%, P<0.001). More patients in group C1 required assistance to complete tracheal intubation (16 vs. 4, P=0.001). The IDS score was significantly higher in group C1 [3.0 (0.0-4.0) vs. 1.0 (0.0-1.0), P=0.045]. There were no significant differences between groups in amplitudes of evoked potentials. No serious adverse events were observed.

Conclusions

A dose of 2× ED₉₅ of cisatracurium provided better intubation conditions and easier tracheal intubation than 1× ED₉₅, without disturbing IONM.

Trial Protocol

Chinese Clinical Trial Registry (No. ChiCTR1900022884).

Management of Gravity Intravenous Infusions in an Austere Environment Using the DripAssist Infusion Rate Monitor

The US Army's 541st Forward Surgical Team (FST) deployed in support of Operation Inherent Resolve- Syria in 2017. Throughout the deployment the 541st FST provided surgical and anesthesia services to US, coalition, and partner forces in numerous austere environments. Following an enemy attack, the FST received multiple casualties and provided a total of 7 critical medication infusions to 3 patients without the aid of electronic-controlled intravenous (IV) infusion pumps or syringes for 10 hours while the wounded soldiers waited for evacuation to a higher level of care. The team administered propofol, norepinephrine, tranexamic acid, and ketamine by individual gravity infusions relying solely on counting drops. An infusion rate monitor (DripAssist, Shift Labs Inc) was used to assist in initial IV rate setup and maintenance. The medics and nurses of the 541st FST found that the infusion rate monitor improved the speed of setting the IV infusion rate, drop counting accuracy, and the team's ability to monitor the continuous delivery of gravity IV infusions.

Laryngeal mask for airway management in open tracheal surgery-a retrospective analysis of 54 cases

Background

Airway management in tracheal resections presents many challenges. The aim of this retrospective analysis is to report the efficacy and complications associated with the use of the laryngeal mask airway in this procedure.

Methods

The charts of 54 consecutive patients operated for tracheal stenosis during the period 2009-2016 were reviewed. This cohort included only resections of the trachea. We evaluated total success rate of laryngeal mask insertion (%), insertion success rate on the first attempt, the quality of intraoperative ventilation through the laryngeal mask, the quality of fibre optic view through the device, incidence of bleeding during the first 24 h, signs of dehiscence of the anastomosis within 48 h and 30-day mortality.

Results

The laryngeal mask airway provided a patent airway throughout the procedure in 52 (96.4%) patients. Insertion of the device failed in 1 (1.8%) patient due to abnormal upper airway anatomy. Another patient (1.8%) developed laryngeal mask malposition during intraoperative neck extension subsequently requiring tracheal intubation. Fibre optic view through the devices including insertion of the flexible bronchoscope was satisfactory in 52 (96.4%) patients. Serious complications, such as pulmonary aspiration, early postoperative bleeding or suture dehiscence were not observed in this cohort.

Conclusions

Based on this analysis of 54 patients, we would consider the laryngeal mask airway a feasible alternative to the tracheal tube for airway management and ventilation during open tracheal surgery.