ISOBOLOGRAPHIC AND DOSE-RESPONSE ANALYSIS OF THE INTERACTION BETWEEN PIPECURONIUM AND VECURONIUM

We have studied the neuromuscular effects of pipecuronium, vecuroniumand their combination in 130 ASA group I or II patients. Patientswere anaesthetized with 0.8% halothane and 60% nitrous oxidein oxygen. Neuromuscular block was recorded as the evoked thenarmechanomyographic response to train-of-four stimulation of theulnar nerve (2Hz at 10-s intervals). The dose-response curveswere determined by probit analysis. The calculated doses producing50% depression of the first twitch height were 15.6, 16.9 and15.0 µg kg^–1 for the pipecuronium, vecuronium andpipecuronium-vecuronium combination groups, respectively. Isobolographic and algebraic (fractional) analyses were used to assessquantitatively the combined neuromuscular effect of pipecuroniumand vecuronium and to define the type of interaction betweenthese drugs. The interaction between pipecuronium and vecuroniumwas found to be additive. (Br. J. Anaesth. 1993; 71: 556–560)      

EFFECT OF PRE-TREATMENT WITH LYSINE ACETYL SALICYLATE ON SUXAMETHONIUM-INDUCED MYALGIA

The hypothesis that prostaglandin inhibitors might reduce theincidence and severity of suxamethonium-induced myalgia wasinvestigated using lysine acetyl salicylate (LAS) 13 mg kg^–1i.v. 3 min before the administration of suxamethonium in 20patients. A comparison was made with atracurium 0.09 mg kg^–1(and placebo) in a double-blind prospective randomized trial.LAS and atracurium were effective in reducing the incidenceand severity of post-suxamethonium myalgia and the increasesin serum potassium concentration. There were no appreciablechanges in serum calcium, sodium, chloride, phosphate, magnesium,creatinine, creatine phosphokinase concentrations or plasmacholinesteraseactivity. Atracurium caused a delay in the onset of action anda decrease in the intensity of suxamethonium-induced neuromuscularblock. It is concluded that LAS pretreatment might have a placein suitable patients in the prevention of suxamethonium-inducedmyalgia and increases in serum potassium concentration.     

COMPARATIVE EFFECTS OF PIPECURONIUM AND TUBOCURARINE ON PLASMA CONCENTRATIONS OF HISTAMINE IN HUMANS

We have examined the effects of a rapid bolus dose of pipecuronium0.1 mg kg^–1 or tubo-curarine 0.5mg kg^–1 on plasmahistamine concentration, heart rate and arterial pressure in20 patients (n = 10 in each group). Anaesthesia was inducedwith thiopentone 6 mg kg^–1 i.v. and maintained with 70%nitrous oxide and halo-thane in oxygen. Neuromuscular blockingdrugs were administered 4 min after administration of thiopentone.Venous blood samples were obtained before induction, 1 min afterthiopentone and 1, 3 and 5 min after the administration of theneuromuscular blocking drugs. Tubocurarine caused 240% and 210%increases in plasma concentration of histamine at 1 and 3 min,respectively. These changes were significant (P < 0.05) at1 min and associated with a decrease in mean arterial pressureand an increase in heart rate. None of the 10 patients receivingpipecuronium had a significant change in plasma concentrationof histamine or in haemo-dynami variables. ^*Present addresses: Department of Anaesthesia, Al-Kasr El-AniHospital, Cairo University, Cairo, Egypt. Present addresses: Department of Pharmacology, Lund University,Lund, Sweden.     

CANNULATION OF THE RADIAL AND DORSALIS PEDIS ARTERIES

The complications inherent in cannulation of the radial (groupI) and dorsalis pedis (group II) arteries were studied in 46patients. All the local and systemic variables which might beconsidered to contribute to damage of the artery were studied,from which it appeared that only the duration of cannulation,prothrombin time and partial thromboplastin time were significantin determining post-cannulation blood flow. A 20-gauge Tefloncannula was used in all patients and velocity of flow measuredwith a Doppler velocimeter probe. A majority of arteries showeda reduction of flow velocity for 24–72 h after the removalof the cannula, with evidence of improvement at 120 h. In sixarteries—three in each group—flow ceased altogetherafter 24–72 h. No disability of either hand or foot resulted.     

KETAMINE FOR CAUDAL ANALGESIA IN CHILDREN: COMPARISON WITH CAUDAL BUPIVACAINE

Fifty children undergoing inguinal herniotomy were allocatedrandomly to three groups to receive a caudal injection of either0.25% bupiv-acaine 1 ml kg^–1 with or without ketamine0.5 mg kg^–1 or ketamine 0.5 mg kg^–1 with normalsaline 1 ml kg^–1. There was no significant differencein quality of pain relief, postoperative behaviour or analgesicrequirements between the ketamine group and the two other groups.The bupivacaine-ketamine mixture provided better analgesia thanthe bupivacaine solution alone. Side effects such as motor weaknessor urinary retention were not observed in the ketamine group.     

THIOPENTONE-PROPOFOL HYPNOTIC SYNERGISM IN PATIENTS

The hypnotic effects of thiopentone, propofol and their combinationwere studied in 120 unpremedicated ASA group I patients. Theendpoint for induction of anaesthesia was taken as inabilityto open the eyes to command 60 s after the end of injection.The dose-response curves were determined by probit analysis.Isobolographic and algebraic (fractional) analyses were usedto assess quantitatively the combined hypnotic effect of thiopentoneand propofol and to define the type of interaction between thesetwo drugs. The interaction between thiopentone and propofolwas found to be synergistic. ^*Present address: Department of Anaesthesia, Solihull Hospital,Solihull, Birmingham.     

INDUCTION DOSE-RESPONSE STUDIES WITH PROPOFOL AND THIOPENTONE

The relative potencies of propofol and thiopentone were assessedusing different indicators of induction of anaesthesia: abolitionof the response to verbal commands and eyelash stimulation.Log-probit dose-response curves for these end-points were determined30, 60 and 90 s after induction in 96 unpremedicated ASA groupI patients. For propofol, ED₅₀ values for abolition of the responseto verbal commands and eye/ash stimulation at different timeintervals were in the ranges 1.76–1.42 and 1.23–1.72mg kg^–1, respectively; corresponding ED₉₅ values were2.18–2.67 and 2.42–3.27 mg kg^–1, respectively.For thiopentone, the calculated ED₅₀ values for verbal commandsand eyelash stimulation at the same time intervals were 1.81–2.23and 3.55–3.40 mg kg^–1; corresponding ED₉₅ valueswere 5.11–6.29 and 6.41–6.70 mg kg^–1, respectively.The potency ratio of propofol to thiopentone observed in thisstudy varied from 1:1.27 to 1:2.88. It is concluded that a dose-responsecurve reflecting one end-point of anaesthesia cannot be usedto define another end-point of anaesthesia.     

Anesthetic management of the hybrid stage 1 procedure for hypoplastic left heart syndrome (HLHS)

Introduction: Despite advances in the surgical and perioperative management of patients with hypoplastic left heart syndrome (HLHS), outcomes for this high‐risk group of patients remains suboptimal. The hybrid approach [bilateral pulmonary artery (PA) banding, ductal stenting, balloon atrial septostomy], is an emerging alternative therapy for the management of HLHS, which defers the risks of a major surgical repair until the infants are older. This article will describe our experience providing the anesthetic management of patients undergoing the hybrid procedure. Methods: After Institutional Review Board approval, we retrospectively reviewed the records of 77 patients who underwent the hybrid procedure as neonates between July 2002 and August 2008. We reviewed both the anesthetic and intensive care records. Results: The hybrid procedure was performed in 77 patients (31 female and 46 male). The average age of the patients was 11.8 days with an average weight of 2.98 kg. Fentanyl was used for analgesia at an average dose of 5.7 mcg·kg^?1. The average increase in the systolic blood pressure after placement of the right and left PA bands was 11.3 mmHg. The average drop in the systemic saturation after placement of the bands was 7%, with an average postband and stent SaO₂ of 82%. Twenty‐one patients received blood transfusion (27.3%) at an average dose of 43.5 ml (14.5 ml·kg^?1). Forty patients received albumin during the case (51.9%) at an average dose of 23.2 ml (7.7 ml·kg^?1). Seventeen patients arrived at the hybrid suite already intubated, and no attempt was made to extubate these patients at the end of the case. Thirty‐six patients were extubated at the end of the procedure, and a total of 64.9% of patients were extubated within the first 24 h postoperatively. Patients had notably stable hemodynamics throughout the first 24 h in the intensive care unit. Discussion: Patients undergoing the hybrid procedure have relatively stable intraoperative and early postoperative hemodynamics. The procedure is performed without cardiopulmonary bypass (CPB) and with minimal narcotic and anesthetic exposure. Patients typically do not require blood transfusions or inotropic support and are extubated at either the end of the procedure or within 24 h of ICU admission. In our experience, the anesthetic management of patients undergoing the hybrid procedure is straightforward and requires relatively few interventions when compared to traditional neonatal surgical repairs. Deferring the risks of anesthesia, CPB, hypothermic circulatory arrest, and prolonged postoperative sedation may yield developmental advantages to patients born with HLHS.