Preinduction Period Research Articles

The effects of preinduction warming on temperature and blood pressure during propofol/nitrous oxide anesthesia

BACKGROUND Core temperature decreases rapidly after induction of anesthesia, largely because heat is redistributed to peripheral tissues. The hypothesis that warming peripheral tissues before induction of general anesthesia (prewarming) minimizes hypothermia was tested. Because circulating blood volume may be greater during exposure to heat compared to cold, the hypothesis that prewarming decreases the amount of hypotension associated with induction of anesthesia was tested also. Finally, the hypothesis that the difference between direct radial arterial blood pressure and blood pressure measured oscillometrically at the brachial artery depends on thermoregulatory and anesthetic conditions was tested. METHODS Each of six volunteers underwent general anesthesia (propofol and nitrous oxide) twice on the same day. Each anesthetic lasted 1 h and was preceded by either 2 h of active warming with forced air or 2 h of passive cooling by exposure to a typical operating room environment. After induction of each anesthetic, volunteers were fully exposed to the ambient environment. Volunteers recovered for 2 h before starting the second preinduction treatment. RESULTS Initial tympanic membrane temperatures were similar before each preinduction treatment: 36.7 +/- 0.4 degrees C when volunteers were not warmed and 36.7 +/- 0.6 degrees C when volunteers were warmed. Tympanic membrane temperature did not change during the preinduction period without warming but increased slightly (delta T = 0.4 +/- 0.2 degree C) during warming. After induction of anesthesia, core temperatures decreased to 36.1 +/- 0.4 degree C over 1 h when volunteers were prewarmed but decreased to 34.9 +/- 0.4 degrees C when they were not. Radial arterial systolic, diastolic, and mean blood pressures were lower before induction of anesthesia when volunteers were warmed compared to when no warming was given. Oscillometric diastolic and mean pressures also were lower during prewarming; however, oscillometric systolic pressure did not differ significantly. Prewarming did not result in less hypotension after induction. Without warming, the difference (radial arterial minus oscillometric) in systolic blood pressure measurements was approximately 17 mmHg. Warming was associated with a reversal of the systolic pressure difference to approximately -6 mmHg. After induction of anesthesia, the differences in systolic and mean pressure measurements became more negative with respect to the preinduction values regardless of preinduction warming treatment. CONCLUSIONS These data confirm our hypothesis that redistribution hypothermia can be minimized by preinduction warming of peripheral tissues. Prewarming decreases blood pressure but does not prevent subsequent hypotension after induction. The difference between radical arterial blood pressure and oscillometric blood pressure depends on thermoregulatory vasomotor changes but also may be influenced by vasodilation associated with administration of propofol and nitrous oxide.

Effect of Clonidine on ICP and on the Hemodynamic Responses to Nociceptive Stimuli in Patients with Brain Tumors

The effect of clonidine on intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), heart rate (HR), and drug requirements was studied in 24 patients scheduled for elective cerebral tumor resection (ICP < or = 20 mm Hg). The patients were randomly assigned to one of two groups: Group P (placebo), 12 patients; Group C (clonidine 3 micrograms/kg 10 min before induction), 12 patients. In all patients, anesthesia was induced with a propofol infusion (500 micrograms/kg/min) combined with fentanyl 2 micrograms/kg, lidocaine 1.5 mg/kg, and vecuronium 0.1 mg/kg. Propofol was also used for maintenance. During the preinduction period, clonidine had no effect on ICP or HR, but in clonidine-treated patients, MAP and CPP decreased significantly in comparison to those of the placebo group. During induction, ICP and HR were stable and similar in both groups. MAP and CPP remained significantly lower in Group C. At intubation and Mayfield clamp application, ICP increased in both groups, with similar values at all times. MAP increased in both groups at intubation, Mayfield clamp application, and incision, staying lower, however, in Group C. CPP followed a pattern similar to that of MAP. Propofol requirements up to the 20th min were lower in Group C than in Group P (2.08 +/- 0.83 vs. 3.3 +/- 0.7 mg/kg, p < 0.05). Finally, throughout the study, eight patients in Group C versus two in Group P had a CPP value < 60 mm Hg for > or = 1 min (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Net economic benefit of a manufactured dinoprostone gel for pre-induction cervical ripening.

The purpose of this study was to estimate the net economic cost or benefit of pretreating women who have a medical indication for induction of labour, and an unprepared (unripe) cervix, with a manufactured dinoprostone (prostaglandin E 2) gel. Findings of a meta-analysis of the results of 3 large, randomised clinical trials were employed in the construction of a decision tree used in the economic analysis. For the intended target population, the primary clinical and economic outcomes of gel pretreatment were shortening of the treatment-to-delivery interval, an increase in the percentage of patients achieving labour and a decrease in the percentage of patients requiring delivery by caesarean section. Application of cost factors associated with these and other variables led to a finding of net savings associated with use of the dinoprostone gel pretreatment, compared with no gel pretreatment, of $US159 to $US214 (1993 prices) per treated patient, corresponding to the maximum and minimum duration of the pre-induction treatment period, respectively.

The Effects of Preinduction Warming on Temperature and Blood Pressure during Propofol/Nitrous Oxide Anesthesia

Core temperature decreases rapidly after induction of anesthesia, largely because heat is redistributed to peripheral tissues. The hypothesis that warming peripheral tissues before induction of general anesthesia (prewarming) minimizes hypothermia was tested. Because circulating blood volume may be greater during exposure to heat compared to cold, the hypothesis that prewarming decreases the amount of hypotension associated with induction of anesthesia was tested also. Finally, the hypothesis that the difference between direct radial arterial blood pressure and blood pressure measured oscillometrically at the brachial artery depends on thermoregulatory and anesthetic conditions was tested. Each of six volunteers underwent general anesthesia (propofol and nitrous oxide) twice on the same day. Each anesthetic lasted 1 h and was preceded by either 2 h of active warming with forced air or 2 h of passive cooling by exposure to a typical operating room environment. After induction of each anesthetic, volunteers were fully exposed to the ambient environment. Volunteers recovered for 2 h before starting the second preinduction treatment. Initial tympanic membrane temperatures were similar before each preinduction treatment: 36.7 +/- 0.4 degrees C when volunteers were not warmed and 36.7 +/- 0.6 degrees C when volunteers were warmed. Tympanic membrane temperature did not change during the preinduction period without warming but increased slightly (delta T = 0.4 +/- 0.2 degree C) during warming. After induction of anesthesia, core temperatures decreased to 36.1 +/- 0.4 degree C over 1 h when volunteers were prewarmed but decreased to 34.9 +/- 0.4 degrees C when they were not. Radial arterial systolic, diastolic, and mean blood pressures were lower before induction of anesthesia when volunteers were warmed compared to when no warming was given. Oscillometric diastolic and mean pressures also were lower during prewarming; however, oscillometric systolic pressure did not differ significantly. Prewarming did not result in less hypotension after induction. Without warming, the difference (radial arterial minus oscillometric) in systolic blood pressure measurements was approximately 17 mmHg. Warming was associated with a reversal of the systolic pressure difference to approximately -6 mmHg. After induction of anesthesia, the differences in systolic and mean pressure measurements became more negative with respect to the preinduction values regardless of preinduction warming treatment. These data confirm our hypothesis that redistribution hypothermia can be minimized by preinduction warming of peripheral tissues. Prewarming decreases blood pressure but does not prevent subsequent hypotension after induction. The difference between radical arterial blood pressure and oscillometric blood pressure depends on thermoregulatory vasomotor changes but also may be influenced by vasodilation associated with administration of propofol and nitrous oxide.

Power spectral analysis of EEG during sufentanil infusion in humans

The purpose of this study was to examine the relationship of continuous sufentanil infusion (0.71 micrograms.kg-1.min-1 for 14 min) and the response of the power spectrum of the electroencephalogram (EEG) performed during the induction of anaesthesia in 12 patients undergoing CABG surgery. Data were collected at various times including the preinduction period, every minute during the infusion period (minute 0 to 14), and 15, 20 and 25 min after the start of the infusion (1, 6 and 11 min respectively after completion of the infusion). Within three minutes of the sufentanil infusion, the total power and the relative power of delta increased to near maximum, while the 95% spectral edge and the mean frequency decreased markedly. In spite of the continued infusion of sufentanil, there were very little further changes in the EEG activity. This ceiling effect for the EEG changes appear to coincide with the failure to respond to verbal command. We conclude that the power spectrum of the EEG failed to respond to increasing doses of sufentanil during its infusion after the rapid initial changes.

Effect of Fentanyl on Circulatory Response to Laryngoscopy and Intubation

The effect of fentanyl on arterial pressure and heart rate during laryngoscopy and intubation was studied in 40 adult normotensive patients. Two groups of 20 patients were observed. Patients received thiopental sodium 5 mg/kg (contal group) or fentanyl 2 μg/kg with thiopental 5 mg/kg (fentanyl group) for induction of anesthesia. The changes of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were measured during the preinduction period, before thiopental (or thiopental+fentanyl), after succinylcholine, immediately after intubation and 5 minutes after intubation. The values were compared with preinduction control values. The results were as follows: The contro#l group showed a significant inerease of SBP, DBP and MAP (p<0.001) but no significant increase was noted in the fentanyl group with tracheal intubation. DBP and MAP returned to normal within 5 minutes and SBP decreased significantly (p<0.05). Significant heart rate elevation following intubation was observed in both groups. It is suggested from the above results that pretreatment with fentanyl 2 g/kg reduce the blood pressure elevation following intubation but dose not prevent the elevation of heart rate.

Simulation technique for difficult intubation: Teaching tool or new hazard?

This investigation evaluated the risks of a simulation drill designed to improve the skill of anesthesia personnel in dealing with an unexpected difficult intubation. In a controlled prospective study, 40 patients with normal airways scheduled to undergo noncardiothoracic surgery were randomized into two groups of 20 patients. In the control group, intubation was performed by standard techniques. In the simulation group, intubation of a difficult airway was simulated and performed with the aid of an endotracheal tube introducer. Heart rate (HR); systolic, mean, and diastolic blood pressures (BPs); and arterial oxygen saturation were measured noninvasively during the preinduction period and 1 minute postintubation. A record was kept of all adverse events, including electrocardiogram (EKG) evidence of myocardial ischemia or cardiac arrhythmias, esophageal intubation, pulmonary aspiration, or tracheal injury. There were no significant differences in percent changes in HR, BP, or oxygen saturation between the two groups. There were five uncomplicated esophageal intubations in the simulation group compared with none in the control group ( p = 0.001). No other adverse events were recorded. The potential hazards of esophageal intubation should be considered before this simulation drill is performed.

LEFT BUNDLE BRANCH BLOCK IN PREINDUCTION PERIOD OF ANESTHESIA

We has experienced a case who had normal preoperative ECG findings, however, developed a left bundle branch block (LBBB) in preinduction period of anesthesia. A 73-year-old male, with chief complaint of melena, was diagnosed as cancer of the sigmoid colon. He had no remarkable medical history nor abnormalities in preoperative laboratory findings. After entering the operating room to undergo elective resection of the sigmoid colon, lead II ECG tracing prior to mesthesia induction revealed a LBBB. However, it changed to normal sinus rhythm snddenly during our investigation of the cause. Following preoxygenation, anesthesia was induced with thiopental, intubated with succinylcholine, and maintained with nitrous oxide 66 percent in oxygen and halothane. During operation, a LBBB pattern occurred whenever heart rate increased to over 110 per minutes (rate dependent LBBB). No change in blood pressure was accompanied by these episodes.Recovery from anesthesia was uneventful. Post operative holter ECG showed intermittent LBBB with no change in GOT, GPT, CPK etc. Though LBBB itself is a relatively benign dysrhythmia, it is significant during anesthesia, because it may indicate a possible development of myocardial infarction. It is difficult to diagnose myocardial infarction on the ECG in the presence of a LBBB.

Anaesthesia for caesarean section in a parturient with quintuplet gestation, pulmonary oedema and thrombocytopaenia.

The case of a 32-year-old parturient with a quintuplet pregnancy is described. The pregnancy had been complicated by premature labour which was treated with ritodrine tocolysis. Betamethasone was administered to hasten fetal lung maturation. The ritodrine therapy was complicated with fluid overload and pulmonary oedema requiring intravenous diuretic treatment. The patient presented urgently for Caesarean section, with fluid overload and worsening thrombocytopaenia. Life-threatening pulmonary oedema was manifest in the immediate preinduction period, following insertion of a pulmonary artery catheter and surgery was delayed to improve the mother's condition with intravenous diuretic therapy. Induction was carried out with the patient in the sitting position, with cricoid pressure maintained to protect the airway as the patient was lowered to a wedged, supine position. Intravenous nitroglycerin was used to control blood pressure. Low pressure mask-bag ventilation was utilized to maintain oxygen saturation and the patient was intubated and ventilated with positive end-expiratory pressure. Positive pressure ventilation was continued for 24 hours postoperatively. The perioperative course is reviewed and followed by a discussion of the anaesthetic considerations for multiple gestation pregnancies.

Photoinduced Seed Germination of Oenothera biennis L

The postinduction period of Oenothera biennis L. seed germination was examined by temperature treatments. For all experiments, seeds received a standard 24 hour/24 degrees C preinduction period and 12 hour/32 degrees C photoinduction period. Germination is inhibited by postinduction temperatures above 32 degrees C. When seeds are briefly incubated at 44 degrees C and then transferred to 28 degrees C, they germinate at a much lower percentage than 28 degrees C controls. When thermally inhibited seeds are placed in the dark at 28 degrees C for 20 hours, they can be promoted to germinate by a single pulse of red light. Seeds incubated at 12 degrees C or below immediately after photoinduction enter a lag period in which they germinate slowly or not at all for a long time and then resume germination. The length of the lag period is exponentially related to the postinduction temperature. When seeds are incubated at a low temperature and then transferred to a warm temperature, they germinate much more rapidly than seeds not incubated at a low temperature. A model is proposed which is consistent with these and additional results. In the model, a germination promoter is irreversibly formed from a precursor and the synthesis of the precursor is favored at low temperatures and its degradation is favored at high temperatures.

The incidence of awareness, and amnesia for perioperative events, after cardiac surgery with lorazepam and fentanyl anesthesia

One hundred patients (mean age 59 ± 10 years) were premedicated with morphine, 0.15 mg/kg, and scopolamine, 0.008 mg/kg. Anesthesia was induced with lorazepam, 50 μg/kg, followed by fentanyl, 50 μg/kg, oxygen and pancuronium, 0.15 mg/kg. Isoflurane was given for short periods before and after cardiopulmonary bypass to 57 patients when hypertension was uncontrolled by addition of fentanyl and/or nitroglycerin. Morphine was used as the sole sedative postoperatively. Patients were interviewed following discharge from the surgical intensive care unit to assess the incidence of operative awareness, and to assess amnesia for events occurring during four preoperative and two postoperative periods of the patients' hospital stay. During three preoperative periods (day of admission, evening before, and morning before operation), 1%, 3%, and 2% of patients had complete amnesia, and 19%, 41%, and 31% had partial amnesia of events. Fifty-five percent of patients exhibited complete, and 34% of patients exhibited partial amnesia to events occurring in the preinduction period. Two patients reported intra-operative awareness (noises, conversation) occurring at the end of the anesthetic. In the two postoperative periods (morning of the day after surgery and intensive care stay), 9% and 15% of patients had complete, and 35% and 47% of patients exhibited partial amnesia. Amnesia was statistically significantly greater in patients over 60 years of age in the preinduction period. Duration of cardiopulmonary bypass did not affect the incidence of amnesia.

Preinduction Cervical Priming with PGE2Intracervical Gel

A prospective, randomized, controlled clinical trial was conducted to evaluate the safety and efficacy of a single, 0.5-mg dose of prostaglandin E2 gel in a shelf-stable triacetin base administered intracervically in patients with an unfavorable cervix (Bishop score less than or equal to 4) 12 hours prior to oxytocin-induction of labor. forty-eight evaluable patients were enrolled, 25 in the PGE2 group and 23 in the control group. PGE2 gel treatment resulted in a significant improvement in the mean Bishop score compared to control (3.14 versus 0.70, P less than .00005). Sixty-four percent of the patients treated with PGE2 had regular uterine contractions during the 12-hour preinduction period beginning 2.18 +/- 2.0 hours after gel insertion, compared to 9% in the control group, P = .0001. Moreover, 12% (3/25) of the patients receiving PGE2 progressed into active labor and delivered during the preinduction period. The duration of oxytocin infusion required for the induction or augmentation of labor was significantly shorter for patients who received intracervical PGE2 gel compared to the control group (13.1 +/- 8.1 versus 19.0 +/- 8.7, P less than .05). However, there was no significant difference in the incidence of cesarean section between the two study groups (40 and 22% in the PGE2 and control groups, respectively). No episodes of uterine hypertonus or hyperstimulation or gastrointestinal side effects occurred as a result of PGE2 gel treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

The induction of bacterial bioluminescence system on solid medium

Induction of the luminescence system of the marine luminous bacteriumVibrio harveyi growing on a solid medium was studied. The induction occurred when the total number of cells per square centimeter of solid medium approached 104 cells (i.e., either 100 colonies consisting of 100 cells per each colony or 1 colony with about 104 cells). The preinduction period and number of cells per colony at the time of induction decreased as the number of colonies per cm2 increased. The ecological significance of the induction of the luminescence system on solid medium is discussed.

MEMORY UNDER DIAZEPAM-MORPHINE NEUROLEFTANESTHESIA IN MALE SURGICAL PATIENTS

Sixty patients participated in an evaluation of memory during elective surgery performed under a type of neuroleptanesthesia in which diazepam and morphine were used as adjuncts to the nitrous oxide (N20)-curare technic. All patients were tested for recall of preinduction and postinduction events. In addition, patients in the experimental group heard word-pairs and neutral narrative passages through earphones at various times during operation; control patients wore the earphones but did not hear any of the taped materials. In general, patients had good recall of the preinduction period. Anesthesia was induced in all patients in approximately 2 minutes, and was accompanied by a deep sleep or amnesic state that lasted for the duration of the operative procedure. A small number (n = 9) of the patients reported vague recall of dreams, and events occurring immediately prior to (n = 2) or following (n = 5) operation. However, none reported that these recollections were in any way upsetting or distressing to them. It is concluded that the administration of a benzodiazepine tranquilizer (diazepam) and a narcotic analgesic (morphine) as adjuncts to NL.0-curare anesthesia results in a type of neuroleptanesthesia that, in addition to producing satisfactory anesthesia for major surgery, also offers considerable assurance that there will be no recollection or awareness during the operative procedure.

AWARENESS DURING ANAESTHESIA

Awareness is the postoperative recall of sensory perception during general anaesthesia. The incidence is quoted at 1-2 per every 1000 patients. This rare but serious adverse event can be extremely distressing for both the patient as well as the anaesthesiologist. Awareness during anaesthesia may occur despite apparently sound anaesthetic management and is usually not associated with pain. However, a few cases may experience excruciating pain and have long term neuropsychiatric sequelae like post-traumatic stress disorder. This adverse event can also have serious medicolegal implications. This article addresses the various contributory factors that may predispose to intra-operative awareness. Preventive measures in the preinduction period as well as intraoperatively are discussed, including the use of depth of anaesthesia monitors. Remedial steps to be taken when such an event occurs are also discussed.