Classic Papers Revisited: An Early Study of Cardioprotection by Volatile Anesthetics: A Behind-the-scenes Look.

Recovery of Contractile Function of Stunned Myocardium in Chronically Instrumented Dogs Is Enhanced by Halothane or Isoflurane. By Warltier DC, al-Wathiqui MH, Kampine JP, and Schmeling WT. ANESTHESIOLOGY 1988; 69:552-65. Reprinted with permission.Following brief periods (5-15 min) of total coronary artery occlusion and subsequent reperfusion, despite an absence of tissue necrosis, a decrement in contractile function of the postischemic myocardium may nevertheless be present for prolonged periods. This has been termed "stunned" myocardium to differentiate the condition from ischemia or infarction. Because the influence of volatile anesthetics on the recovery of postischemic, reperfused myocardium has yet to be studied, the purpose of this investigation was to compare the effects of halothane and isoflurane on systemic and regional hemodynamics following a brief coronary artery occlusion and reperfusion. Nine groups comprising 79 experiments were completed in 42 chronically instrumented dogs. In awake, unsedated dogs a 15-min coronary artery occlusion resulted in paradoxical systolic lengthening in the ischemic zone. Following reperfusion active systolic shortening slowly returned toward control levels but remained approximately 50% depressed from control at 5 h. In contrast, dogs anesthetized with halothane or isoflurane (2% inspired concentration) demonstrated complete recovery of function 3-5 h following reperfusion. Because the anesthetics directly depressed contractile function, additional experiments were conducted in which a 15-minute coronary artery occlusion was produced during volatile anesthesia; however, each animal was allowed to emerge from the anesthetized state at the onset of reperfusion. Similar results were obtained in these experiments, demonstrating total recovery of contractile function within 3-5 h following reperfusion. Thus, despite comparable degrees of contractile dysfunction during coronary artery occlusion in awake and anesthetized dogs, the present results demonstrate that halothane and isoflurane produce marked improvement in the recovery of segment function following a transient ischemic episode. Therefore, volatile anesthetics may attenuate postischemic left ventricular dysfunction occurring intraoperatively and enhance recovery of regional wall motion abnormalities during reperfusion.

Calculation of volatile anaesthetics consumption from agent concentration and fresh gas flow.

BACKGROUND: The assessment of volatile agents' consumption can be performed by weighing vapourisers before and after use. This method is technically demanding and unavailable for retrospective analysis of anaesthesia records. Therefore, a method based on calculations from fresh gas flow and agent concentration is presented here. METHODS: The presented calculation method herein enables a precise estimation of volatile agent consumption when average fresh gas flows and volatile agent concentrations are known. A pre-condition for these calculations is the knowledge of the vapour amount deriving from 1 ml fluid volatile agent. The necessary formulas for these calculations and an example for a sevoflurane anaesthesia are presented. RESULTS: The amount of volatile agent vapour deriving from 1 ml of fluid agent are for halothane 229 ml, isoflurane 195 ml, sevoflurane 184 m, and desflurane 210 ml. The constant for sevoflurane is used in a fictitious clinical case to exemplify the calculation of its consumption in daily routine resulting in a total expenditure of 23.6 ml liquid agent. CONCLUSIONS: By application of the presented specific volatile agent constants and equations, it becomes easy to calculate volatile agent consumption if the fresh gas flows and the resulting inhaled concentration of the volatile agent are known. By this method, it is possible to extract data about volatile agent consumption both ways: (1) retrospectively from sufficiently detailed and accurate anaesthesia recordings, as well as (2) by application of this method in a prospective setting. Therefore, this method is a valuable contribution to perform pharmacoeconomical surveys.

The effect of succinylcholine on malignant hyperthermia events in susceptible swine.

BACKGROUND: While the impact of volatile anaesthetics to induce malignant hyperthermia (MH) is abundantly clear, the role of succinylcholine still remains controversial. To evaluate the influence of succinylcholine on porcine MH events, the authors investigated the hemodynamic and metabolic responses in MH susceptible (MHS) and non-susceptible (MHN) swine following either succinylcholine or halothane application alone or a combination of both substances. METHODS: With approval of the local animal care committee 27 MHS and 30 MHN pigs were anaesthetized and mechanically ventilated. Fiberoptic probes for continuous PCO2 measurement were inserted into the femoral vein and the triceps muscle. Group A received succinylcholine 4 mg/kg, group B incremental doses of halothane (0.5, 1.0 vol%) and group C succinylcholine and halothane simultaneously. Vital signs were recorded continuously. RESULTS: Prior to drug application measured values did not differ between MHS and MHN. While MHN pigs did not show relevant alterations, succinylcholine, halothane and the combination of both lead to significant hemodynamic and metabolic changes in MHS swine. CONCLUSIONS: Hemodynamic and metabolic alterations following succinylcholine were similar to halothane in MHS pigs. The combination of both pharmacological agents potentiated the observed effects. According to these results succinylcholine acted as an independent and supportive factor during onset of an MH episode.

Halothane-anaesthetized, closed-chest, guinea-pig model for assessment of drug-induced QT-interval prolongation.

For the halothane-anaesthetized, closed-chest, guinea-pig model, corrected QT interval (QTc) has been empirically used to estimate the extent of drug-induced QT-interval prolongation. In the present study, we employed an atrial pacing method to clarify a net effect of a drug on the QT interval in this model. The atrial pacing catheter was inserted via the jugular vein with a minimal surgical invasion, and the effects of d-sotalol (0.3 and 3 mg/kg, intravenously) and verapamil (0.01 and 0.1 mg/kg, intravenously) on electrocardiogram parameters were assessed under the sinus rhythm and during the atrial pacing of 200 and 240 beats/min. d-Sotalol significantly prolonged the QT interval in a reverse use-dependent manner and decreased the heart rate, while verapamil prolonged the PR interval without affecting the heart rate or QT interval, indicating the sensitivity and specificity of this model in assessing the pharmacodynamics of the drug-induced QT-interval prolongation. Using the QT/RR relationship under the sinus rhythm, we obtained the following two types of QT-interval correcting formulae; namely, QTc = QT - 0.207(RR - 300) by a linear regression method; and QTc = QT/(RR/300)0.332 by a non-linear regression method, the latter of which is equal to 0.67 times of Fridericia's formula, providing rationale for the use of mathematical correction in this model. Thus, the halothane-anaesthetized, closed-chest, guinea-pig model may be highly useful for assessing the drug-induced QT-interval prolongation, which may become an alternative to current models for the in vivo QT assay.

[Quantitative EEG in assessment of anesthesia depth. Methods of comparison]. / Kvantitativ eeg til vurdering/af anaestesidybde. Metodesammenligning.

Methodology for assessment of depth of anaesthesia based on analysis of the electroencephalogram (eeg) is controversial. Techniques range from display of single measures, for example median value of the frequency spectrum, to dedicated pattern recognition systems based on measures of several eeg features. We have compared the performance of four techniques using tape-recorded data from 23 patients anaesthetised with either halothane or isoflurane using standardised regimens. The techniques were: median frequency, spectral edge frequency, the cerebral function analysing monitor (CFAM-1) and a depth of anaesthesia monitor based on eeg pattern recognition (ADAM). Dose-response curves are presented for stepwise increases in stable end-tidal concentrations of each agent. Results indicated considerable inter-patient variability and showed the limitations of single eeg measures, particularly with deeper anaesthesia producing burst suppression patterns in the eeg. Pattern recognition techniques reduced these difficulties and appeared to be promising over a wide range of anaesthetic levels.

Halothane consumption under varying breathing circuit designs.

Thirty one patients at the Eldoret District Hospital, currently being used as a referral and teaching hospital, were anaesthetised and allowed to breathe through any of the three standard Maplesons circuits. The quantity of halothane required to maintain a satisfactory level of anaesthesia was measured and expressed in millilitres per kilogramme body weight, per minute. This value was used to compare the cost-effectiveness of the three circuits under different modes of ventilation.

Halothane and cardiac autonomic control in infants: assessment with quantitative respiratory sinus arrhythmia.

In comparison to adults, infants undergoing halothane anesthesia have an increased incidence of clinically significant episodes of bradycardia, hypotension, and cardiac arrest. To examine potential cardiac autonomic regulatory mechanisms that may account for these observations, the relationship between respiratory activity and short-term variations of heart rate was quantified in 10 healthy term nonpremedicated infants (28.4 +/- 0.6 wk old) undergoing elective surgery with halothane and low caudal anesthesia. Quantitative respiratory activity, heart rate, and cuff blood pressure data were obtained during the preoperative awake period, and at three depths of halothane--1, 1.3, and 2.0 mean alveolar concentration (MAC). Time and frequency domain analyses were performed on two 2.2-min epochs of data from each condition to yield mean values, spectral measures of low (0.02-0.15 Hz) and high (0.15-0.80 Hz) frequency power (LF and HF), and the LF/HF ratio. The sympathetic (As) and parasympathetic (Ap) components of respiratory sinus arrhythmia were quantified using the transfer relations between respiration and heart rate to derive gain factors Ax and Ap, respectively. Mean heart rate, blood pressure, and respiratory activity all decreased with halothane exposure (p < 0.01), but did not differ by halothane dose. Similarly, LF, HF, LF/HF, and respiratory powers all decreased with halothane, but not between doses. When the effects of respiratory activity on heart rate were accounted for, As decreased at 1.3 and 2.0 MAC only, but Ap remained unchanged. Decreased LF and HF power suggests that halothane altered both sympathetic and parasympathetic heart rate control; however, when the ratio between LF and HF and the quantitative effects of respiration are accounted for, halothane appears to cause a reduction in respiratory related sympathetic heart rate control, without a significant change in parasympathetic control.

Valoración de un método para intubación a ciegas / Blind nasotracheal intubation

Intubación nasal a ciegas un arte en la práctica anestesiológica es sin duda un método útil y ocasionalmente el único posible este estudio está encaminado a demostrar la eficacia del uso de la sonda de succión para facilitar la introducción de la sonda de succión para facilitar la introducción de la sonda endotraqueal, utilizándola como guía. Se estudiaron 2 grupos a los cuales se designaron 30 pacientes ASA I-II ambos sexos 30 por ciento femeninos y 70 por ciento masculinos al grupo uno se le colocó una guía a través de la sonda endotraqueal (ING) al grupo 2 no se le coloco guía (INSG). La monitorización consiste en el registro continuo de presión arterial automática cada 2.5 minutos, no invasiva, frecuencia cardiaca, temperatura corporal, ECG, con un registro de trazo del monitor, oximetría de pulso y capnografo. La inducción fue con halotano y oxígeno manteniéndolos con ventilación espontánea. Los resultados fueron para evaluar el número de intensos para la realización de la técnica el grupo ING lo realizó en 2 intentos, el primero fue de 61.5 por ciento y el segundo de 38.5 por ciento. El grupo INSG lo logró en 4 intentos, el primero de 33.3 por ciento, 26.7 por ciento, 13.3 por ciento y 26.7 por ciento, respectivamente P= 0.01 y X²=12.1709. 5 pacientes del mismo grupo no se pudieron intubar por lo que se cambio de técnica, P=0.00005 FISHER, concluyendo que el uso de un cateter de succión como guía favorece notablemente la intubación nasotraqueal a ciega

Volatile agent use: perception and practice. A survey of agent use over a 3-year period.

We calculated the quantity, as MAC hours and MAC hours anaesthetic, of halothane, enflurane and isoflurane, used in this Health District over a 3-year period. Halothane accounted for 77% of anaesthesia in the first year and for 57% in the final year. Overall usage of volatile agents decreased. Fifteen consultants and 19 senior registrars perceived, in a survey of practice, only a change in relative use of volatile anaesthetic agents with a large swing from halothane to both enflurane and isoflurane. Half the anaesthetists stated that the medicolegal consideration was the prime reason for their change. The perceived total demise of halothane does not appear to have been realised, despite individual anaesthetist's perceptions.

Assessment of immediate post-anaesthetic recovery in young children following intravenous morphine infusions, halothane, and isoflurane.

Within 15 minutes of terminating general anaesthesia, progressive recovery of consciousness, spontaneous ventilation and cough, and limb movements were assessed in 60 young children (age range 0-5 years, mean +/- SEM; 2.83 +/- 0.34; weight 13.86 +/- 0.41 kg). All patients were ASA physical status class I-III, received a standard intravenous induction (atropine 0.02 mg X kg-1, thiopental sodium 5 mg X kg-1, diazepam 0.2 mg X kg-1), were intubated with an orotracheal tube following the administration of metocurine, 0.4 mg X kg-1, and were maintained under general anaesthesia with nitrous oxide and oxygen in a 70:30 mixture administered by a T-piece circuit. They were ventilated mechanically to maintain normal blood-oxygen tension and normocarbia. The patients were assessed in three equal groups according to the anaesthetic supplement they received. Group I received intravenous infusions of morphine sulfate (loading dose 60 micrograms X kg-1 administered over 5 minutes followed by a continuous intravenous infusion of 2 micrograms X kg-1 X min-1. Patients in Groups II and III had 0.5 per cent halothane and 1.0 per cent isoflurane respectively added to the nitrous oxide/oxygen fresh gas mixture rather than morphine sulphate infusions. By the end of the study period, there was no significant difference in the degree of recovery between the morphine and the isoflurane groups but the patients in the halothane group had recovered to a lesser degree. Generally, the patients in the morphine group were awake but not crying, while those in the other two groups were less sedated.