Acoustic monitoring of lung sounds for the detection of one-lung intubation

INTRODUCTION

Monitoring methods for the early diagnosis of one-lung intubation (OLI) are nonspecific and controversial. In this study, we evaluated a new acoustic monitoring system for the detection of OLI.

METHODS

Lung sounds were collected from 24 adult surgical patients scheduled for routine surgical procedures. Four piezoelectric microphones attached to the patients' backs were used to sample lung sounds during induction of anesthesia and endotracheal tube positioning. To achieve OLI, the endotracheal tube was inserted and advanced down the airway so that diminished or no breath sounds were heard on the left side of the chest. The tube was then withdrawn stepwise until equal breath sounds were heard. Fiberoptic bronchoscopy confirmed the tube's final position. Acoustic analyses were preformed by a new algorithm which assumes a Multiple Input Multiple Output system, in which a multidimensional Auto-Regressive model relates the input (lungs) and the output (recorded sounds) and a classifier, based on a Generalized Likelihood Ratio Test, indicates the number of ventilated lungs without reconstructing the original lung sounds from the recorded samples.

RESULTS

This algorithm achieved an OLI detection probability of 95.2% with a false alarm probability of 4.8%.

CONCLUSION

Higher detection values can be achieved at the price of a higher incidence of false alarms.

Laryngeal mask in prone position: pure exhibitionism or a valid technique

AIM

The laryngeal mask airway (LMA) is used worldwide during general anesthesia with controlled or spontaneous breathing. Normally its use is limited to patients undergoing surgery in the supine but not the prone position.

METHODS

A prospective study of 50 consecutive ASA 1 and 2 patients who underwent ambulatory surgery in the prone position. In the first 25 patients anesthesia was induced in the supine position on a transport trolley after which the patients were turned face down following tracheal intubation. The next 25 patients were asked to lie comfortably in the prone position before receiving anesthesia. Induction and insertion of LMA were performed when they were already prone.

RESULTS

There were neither complications nor airway loss when LMA was used in the prone position. The induction-incision time was 23.6+/-3.6 min (range 21-37) in Group 1 and 7+/-2.44 min (range 5-15) in Group 2 (P<0.0001) and the manpower required for positioning (the number of medical and paramedical personnel required to place the patient prone) was considerable reduced in Group 2 (LMA) compared to Group 1 (1.0 versus 3.12+/-0.6 (range 2-4; P<0.0001). Group 2 showed also, significantly more favorable hemodynamic parameters.

CONCLUSION

To start anesthesia with patients already prone shortens the induction-incision time, reduces the manpower involved in the positioning process and causes fewer hemodynamic changes than the standard technique of induction and intubation in the supine position followed by turning the patient facedown.

Laryngeal mask airway and the Robinow syndrome

The Robinow syndrome is an extremely rare congenital syndrome that causes facial malformations, as well as genital, cardiac and skeletal abnormalities. Patients with this syndrome undergo several operations during their life. Because of the facial abnormalities they carry a potential risk for difficult intubation. We describe the case of a boy who underwent several operations with documented difficult intubation. The laryngeal mask airway provided a good solution for airway control and afforded adequate ventilation under both controlled mechanical ventilation and spontaneous breathing.

Insertion of the endotracheal tube, laryngeal mask airway and oesophageal-tracheal Combitube®. A 6-month comparative prospective study of acquisition and retention skills by medical students

OBJECTIVE

To assess the ability of medical students to learn and retain skills of airway manipulation for insertion of the endotracheal tube, the laryngeal mask airway (Laryngeal Mask Company, Henley-on-Thames, UK) and the oesophageal-tracheal Combitube (Kendall-Sheridan Catheter Corp., Argyle, NY, USA).

METHODS

A 6-month prospective study was conducted among fifth-year medical students attending a 3-week clerkship in the Division of Anesthesiology and Critical Care Medicine in the Soroka Medical Center. All the students viewed a demonstration of insertion technique for the endotracheal tube, the laryngeal mask airway and the Combitube, followed by formal teaching in a mannikin. At the end of the program, the insertion skills were demonstrated in the mannikin, the success rate on the first attempt was registered and the students were requested to assess (by questionnaire) their ability to execute airway manipulation (phase 1). Six months later, the students were requested to repeat the insertion technique, and a similar re-evaluation applied (phase 2).

RESULTS

The success rate, during the first phase, at first attempts was 100% for the laryngeal mask airway and the Combitube, compared to 57.4% for the endotracheal tube (P < 0.02), and 92.6%, 96.2% and 62.9% (P < 0.02) respectively for the second phase of the study.

CONCLUSION

Learning and retention skills of medical students, in a mannikin, are more accentuated with the laryngeal mask airway and the Combitube than seen with an endotracheal tube.

Does supplemental perioperative oxygen administration reduce the incidence of wound infection in elective colorectal surgery?

AIM

An association has been proposed between perioperative administration of 80% oxygen and a lower incidence of wound infection after colorectal surgery. The present study was conducted to assess this hypothesis.

METHODS

Thirty-eight patients (ASA classification 1 and 2) undergoing elective colorectal cancer surgery were allocated at random to 2 groups. Group 1 consisted of 19 patients who received an admixture of 80% oxygen and 20% nitrogen during anesthesia through an orotracheal tube and during the 2 first hours in the recovery room through a tight facemask with reservoir. Group 2 consisted of 19 patients who received an admixture of 70% nitrous oxide and 30% oxygen during anesthesia, followed by administration of 30% oxygen delivered by a blender through a tight facemask with reservoir in the same manner than group 1, during the first 2 hours in the recovery room. Wound infection was evaluated daily during hospital stay and after 7 days, 2 weeks, and 1 month.

RESULTS

The incidence of wound infection was 12.5% in group 1 and 17.6% in group 2 (p=0.53).

CONCLUSIONS

The results of this study showed no reduction in the incidence of wound infection following elective colorectal surgery in patients receiving 80% oxygen during the perioperative period.

The anaesthetic management of patients with congenital insensitivity to pain with anhidrosis

BACKGROUND

Congenital insensitivity to pain with anhidrosis (CIPA, or hereditary sensory and autonomic neuropathy type IV) is a rare, autosomal recessive disease, related to a mutation in the TrkA gene, characterized by inability to sweat, insensitivity to pain and recurrent episodes of hyperpyrexia. There are two Bedouin tribes in Israel with different mutations of the TrkA gene: one in the southern region and the other in the northern region. The Soroka University Medical Center is the referral centre for the entire southern region of Israel. One in 4500 anaesthesia cases involves a patient with CIPA.

METHODS

We reviewed 40 anaesthesia records of 20 patients with CIPA for anaesthetic technique and incidence of side-effects.

RESULTS

Sixteen patients developed complications in the immediate perioperative period: mild hypothermia in one patient and cardiovascular events in 15 others with one case of cardiac arrest. These complications were unrelated to the anaesthetic drug administered. There were no events of hyperthermia or postoperative nausea.

CONCLUSIONS

Cardiovascular complications following anaesthesia are common in patients with the southern Israel variant of CIPA. Hyperthermia, previously recognized as a major concern in patients with congenital insensitivity to pain with anhydrous, was not seen in our patients. We conclude that cardiovascular involvement is frequently encountered in CIPA patients following anaesthesia and is the major concern in their anaesthetic management.

Retrograde tracheal intubation: beyond fibreoptic endotracheal intubation

BACKGROUND

Flexible fibreoptic laryngoscopy is the method of choice for coping with difficult tracheal intubations, a leading cause of catastrophic outcomes in anaesthesia. However, this technique is not always available or feasible. Retrograde intubation is a minimally invasive airway management technique with a flat learning curve and a high level of skill retention.

METHODS

A retrospective review of the anaesthesia records of 24 patients who underwent retrograde intubation. The success rate and the incidence of complications were recorded.

RESULTS

Retrograde tracheal intubation was successful in all 24 patients. In 21 patients it succeeded on the first attempt. In two patients it succeeded when the technique was changed from sliding over a guide wire to a pulling technique. The most common complication was a sore throat in almost 60% of the patients. Two patients had mild subcutaneous emphysema and one had minimal bleeding at the puncture site.

CONCLUSIONS

In these patients retrograde tracheal intubation was easy to perform, had a high success rate and a low incidence of complications. It is a reliable alternative when fibreoptic intubation is precluded, fails or is unavailable.

A history of neuraxial administration of local analgesics and opioids

The history of intrathecal and epidural anaesthesia is in parallel with the development of general anaesthesia. As ether anaesthesia (1846) is considered the first modern anaesthetic since its use by Morton 157 yr ago, so Bier made history by using cocaine for intrathecal anaesthesia in 1898. The first published report on opioids for intrathecal anaesthesia belongs to a Romanian surgeon, Racoviceanu-Pitesti, who presented his experience at Paris in 1901. It was almost a century before the opioids were used for epidural analgesia. Behar and his colleagues published the first report on the epidural use of morphine for the treatment of pain in The Lancet in 1979. Epidural and intrathecal opioids are today part of a routine regimen for intra- and postoperative analgesia. Over the last 30 yr, the use of epidural opioids has became a standard for analgesia in labour and delivery, and for the management of chronic pain. Finally, epidural opioids have been shown to have a pre-emptive effect, when used before major surgery. We present the evolution of neuraxial anaesthesia and the history of intrathecal and epidural administration of opioids.

Influence of the cortical electrical activity level during general anaesthesia on the severity of immediate postoperative pain in the morbidly obese

BACKGROUND

The objective of anaesthesia is to provide hypnosis, analgesia and adequate conditions during surgery. It is difficult to establish the appropriate dose of general anaesthetic drugs in the morbidly obese patient. Moreover, there are conflicting data concerning adequate anaesthesia levels and the severity of postoperative pain. The aim of this study was to investigate the relationship between the spectral edge frequency (SEF) during general anaesthesia and the severity of immediate postoperative pain following gastric banding surgery in morbidly obese patients.

METHODS

Seventy-one ASA 2 morbidly obese patients (BMI > 35%) undergoing elective laparoscopic gastric banding procedure were recruited for this study. Anaesthesia consisted of midazolam, fentanyl and thiopental for induction, vecuronium for muscle relaxation, N2O and isoflurane with additional fentanyl administrations, according to the clinical judgement of the anaesthesiologist, for maintenance. Continuous SEF monitoring was added to the standard monitors (SpO2, ETCO2, ECG, NIBP, O2 and isoflurane concentration), but the EEG monitor screen was hidden from the anaesthesiologist's sight. SEF postoperative analysis divided the patients into two groups: group 1, SEF-recommended target range of 8-12 Hz, more than 80% of the surgical time; and group 2, SEF-recommended target range of 8-12 Hz, less than 80% of the surgery duration. Pain intensity was assessed in the post anaesthesia care unit using a standard visual analogue scale (VAS) of 10 cm, when patients were awake enough to correct a deliberately given wrong own telephone or ID number. Intravenous morphine was administered for postoperative analgesia in 2-mg increments, every 3-4 min, until the patient felt comfortable. A recovery room nurse unaware of the SEF range recorded during surgery registered pain severity and morphine requirements.

RESULTS

The end-tidal isoflurane concentration was significantly higher in group 1 than in group 2 (0.83 vs. 0.7 P = 0.016). The intensity of pain at admission into the recovery room and at discharge was significantly lower in group 1 than in group 2 (VAS 6.1 vs. 6.9-P = 0.0049, and 3.9 vs. 4.2-P = 0.00478, respectively).

CONCLUSIONS

Keeping the SEF range between 8 and 12 Hz during anaesthesia for laparoscopic gastric banding for morbid obesity, both the immediate post operative pain intensity and morphine requirement, are significantly reduced.

Should disclosure of the danger of awareness during general anesthesia be a part of preanesthesia consent?

Awareness during anesthesia (AGA) is known as an intraoperative incident which could lead to a series of untoward effects, among them symptoms compatible with the posttraumatic stress syndrome (PTSS). Incidence of AGA ranges between 0.1% and 0.7%, most of the reports indicating a 0.2% rate of all general anesthesias. Nevertheless, some patients are considered to be in a higher than usual risk for developing this incident. The list of AGA high-risk situations include caesarian section, open heart surgical procedures, marked obesity, major trauma with hemodynamic instability and chronic use of drugs, alcohol or tobacco smoking. The usual preanesthetic informed consent does not mention AGA among the possible undesired effects of general anesthesia, neither in Israel nor in other parts of the world. This paper rises the question of the indication to discuss the AGA matter, as part of the informed consent, with any patient who is prone develop it in a significant higher percentage than the general population. The topic can be discussed by the primary care physician or by the surgeon, but this represents the obvious task of the anesthesiologist during his/her first contact with the patient before anesthesia and surgery. It is the authors belief that a preoperative discussion on AGA might substantially reduce the magnitude of repercussions of AGA among high-risk patients to develop this anesthetic complication.

Vocal cord paralysis as a consequence of peritonsillar infiltration with bupivacaine

Reduction of postoperative pain is an important goal in the perioperative management of tonsillectomy patients. This is particularly the case for children, who often exhibit resistance to intramuscular or rectal administration of drugs. Peritonsillar bupivacaine infiltration, a relatively safe method of pain control, is in some centers frequently used by otolaryngologists for pain relief. We present the case of a 5-year-old girl who developed bilateral vocal cord paralysis following preoperative peritonsillar bupivacaine infiltration. After an uneventful tonsillectomy and extubation, stridor and respiratory distress developed. Bilateral vocal cord paralysis was seen on laryngoscopy. The patient was reintubated and five hours later was successfully extubated without further sequelae. Anesthesiologists and surgeons should be aware of this uncommon complication than can occur with the use of peritonsillar bupivacaine infiltration for pain control in tonsil surgery.

Commercial propofol solutions: is the more expensive also the more effective?

STUDY OBJECTIVE

To compare the efficacy and safety of four commercial propofol solutions marketed in Israel.

DESIGN

Prospective, randomized, double-blind study.

SETTING

University-affiliated medical center.

PATIENTS

120 ASA physical status I and II nullipara patients undergoing dilatation and curettage for interrupted pregnancy.

INTERVENTIONS

Patients were randomized into four groups of 30 patients each. Group 1 was anesthetized with Diprivan (AstraZeneca, UK), group 2 with Recofol (Leiras Oy, Finland), group 3 with Propofol (Abbott), and group 4 with Diprofol (Taro, Israel).

MEASUREMENTS AND MAIN RESULTS

The four study groups were similar in mean age and weight. There were no statistically significant differences in the administered doses, quality of anesthesia, recovery time, or adverse effects among the four groups.

CONCLUSIONS

Diprivan, Recofol, Diprofol, and Propofol Abbott are equally effective as anesthesia induction drugs for dilation and curettage, with a similar incidence of adverse effects. Because cost limitations have become a significant factor in medical care, the choice of drug in this group should be based solely on cost considerations.

Continuous venovenous hemofiltration improves intensive care unit, but not hospital survival rate, in nonoliguric septic patients

PURPOSE

The purpose of this study was to assess the effect of the early institution of continuous veno-venous hemofiltration on survival rates of nonoliguric, septic patients.

MATERIALS AND METHODS

A retrospective study of 48 nonoliguric septic patients with PaO(2)/FIO(2) < or = 250, who were admitted to the General Intensive Care of the Soroka Medical Center. Twenty-six patients were treated with continuous venovenous hemofiltration (CVVH group) and 22 were treated by conventional therapy. The end point of treatment was weaning from mechanical ventilation, adequate oxygenation, and the need for minimal cardiocirculatory support.

RESULTS

The study groups were similar in terms of age, gender, percentage of surgical or nonsurgical patients, APACHE II scores, and the Therapeutic Intervention Scoring System (TISS). Baseline serum urea and creatinine levels were similar in the groups, but the PAO(2)/FIO(2) ratio was significantly lower in the CVVH group (150.6 +/- 86 vs. 214.2 +/- 8.9). Twenty of the CVVH patients and 10 of the patients receiving conventional therapy were discharged from the intensive care unit (P =.03), but the hospital discharge rate was only slightly higher in the CVVH group (12 of 26) compared with the conventional therapy group (7 of 22) (P =.145).

CONCLUSIONS

In this retrospective uncontrolled study, the mortality rate was considerably lower in nonoliguric septic patients who received continuous venovenous hemofiltration early in the course of the disease. The improved survival rate may be due to the ability of CVVH to eliminate mediators involved in the septic process, thus averting the multiple system organ failure consequent to septic insult.

Evaluation of the VersaMed portable ventilator: clinical trials

The VersaMed 201 is a lightweight, computer-controlled, electrically driven ventilator, designed for transport, home-ventilation and field use. We have evaluated the device in human beings with healthy and pathological lungs. In the first part of the study, the VersaMed was substituted for a standard operating room ventilator for 15-30 min during elective surgery in 20 subjects. In the second stage of the study, 20 patients with lung pathology who were being ventilated in the critical care department were transferred to the VersaMed for a 30-min period. In all the patients studied, arterial blood gases, haemodynamic parameters and other respiratory variables were maintained at similar values seen with the standard ventilators used. We conclude that the VersaMed 201 is suitable for use in human beings with healthy and pathological lungs as a reliable, portable ventilator.

Propofol versus midazolam for conscious sedation guided by processed EEG during endoscopic retrograde cholangiopancreatography: a prospective, randomized, double-blind study

BACKGROUND AND STUDY AIMS

Endoscopic retrograde cholangiopancreatography (ERCP) is a complex procedure, which requires appropriate sedation. The aim of this prospective, randomized, double-blind study was to compare the quality and characteristics of sedation with midazolam or propofol in patients undergoing ERCP.

PATIENTS AND METHODS

A total of 32 patients undergoing ERCP were randomly allocated for sedation with propofol (n = 15) or midazolam (n = 17). Blood pressure, heart rate, and O2 saturation were monitored. Sedation was maintained at near constant levels by use of the spectral edge frequency (SEF) technique, an EEG-based method for measuring the depth of sedation. Clinical variables, patient cooperation, time to recovery, and amnesia served as outcome variables.

RESULTS

There was no significant difference between the two study groups in patient characteristics. The "target SEF" was 13.6 +/- 0.7 Hz for the propofol group and 14.8 +/- 1.1 Hz for the midazolam group (n.s.). The only clinical parameter with a significant difference between the groups was the percent of time in which the heart rate deviated more than 20% from baseline for at least 2 minutes, i.e. 14.6 +/- 2.0 % for propofol and 48.2 +/- 38.0% for midazolam (P<0.01). Patient cooperation was better in the propofol group than in the midazolam group (full cooperation, 13/15 vs. 1/17, respectively; P<0.001). Patient recovery was significantly quicker in the propofol group (P<0.001). The degree of amnesia was similar in both groups; no patient in either group remembered details of the procedure.

CONCLUSIONS

ERCP is better tolerated by patients sedated with propofol compared with midazolam, with a shorter recovery time and lesser hemodynamic side effects. Propofol should be considered to be the sedative drug of choice for ERCP.

Predictors of recommendation and acceptance of intrapartum epidural analgesia

We conducted this prospective study to characterize the obstetric and sociodemographic variables that predict physicians' recommendations and patients' acceptance of intrapartum epidural analgesia. The study population consisted of 447 consecutive, low-risk parturients in early active labor. Epidural analgesia was recommended to 393 patients (87.9%), however only 164 (41.7%) consented to receive it. A multiple logistic regression analysis demonstrated that the severity of pain, as assessed by the medical staff (odds ratio [OR] = 1.5, 95% confidence interval [CI] 1.13, 1.93), low parity (OR = 0.57, 95% CI 0.44, 0.74), and low maternal age (OR = 0.89, 95% CI 0.79, 0.99) were significant factors affecting recommendations of epidural analgesia. In a multivariate analysis, severity of subjective pain (OR = 1.39, 95% CI 1.16, 1.68), low parity (OR = 0.80, 95% CI 0.73, 0.99), high education (OR = 90.09, 95% CI 27.02,257.06), and the patients' being secular compared with religious (OR = 2.14, 95% CI 1.08,4.21) were found to be independent predictors of acceptance of epidural analgesia. There are differences between patients offered and those not offered epidural analgesia and between parturients who accept and those who do not accept this analgesia.

IMPLICATIONS

We studied the factors that influence the recommendation of epidural analgesia by obstetricians, as well as its acceptance by the laboring patients at a university hospital in Israel. Epidural analgesia was recommended more often to low parity, younger women exhibiting more pain. Parturients who perceived greater pain were more secular, had low parity, and had a higher level of education were more likely to accept it.

Intranasal salbutamol instillation in asthma attack

Beta-two sympathomimetic drugs are the treatment of choice for asthmatic attack. Their main effect is to dilate the bronchi by a direct action on beta-two adrenoreceptors on the smooth muscle, and also by mediator release inhibition from mast cells. Salbutamol is widely used in the treatment of bronchial asthma, and is usually administered either by inhalation, orally, or parenterally. The nasal route seems to afford an effective way to administer medications, since the nasal mucosa has a relatively large surface area, and there is no gastrointestinal-hepatic first pass-effect, thus avoiding extensive loss of the administered drug. We describe herein the use of nasal salbutamol in 3 patients with severe asthma attacks who were refractory to conventional therapy, with favorable responses and without significant undesirable effects.

Accidental intra-arterial injection of propofol

We report a case of accidental intra-arterial injection of propofol in a 30-year-old woman admitted for curettage. The patient reported pain, which was followed by a hyperaemic area of 6 x 7 cm around the injection site. Later a blanching of the distal part of the hand was noticed, lasting for 3 min. When pain appears during propofol administration, an intra-arterial injection must be excluded.

Ketamine attenuates the interleukin-6 response after cardiopulmonary bypass

Cardiopulmonary bypass (CPB) has been proposed as a model for studying the inflammatory cascade associated with the systemic inflammatory response syndrome. Serum interleukin-6 (IL-6) concentration seems to be a good indicator of activation of the inflammatory cascade and predictor of subsequent organ dysfunction and death. Prolonged increases of circulating IL-6 are associated with morbidity and mortality after cardiac operations. In the present study, we compared the effects of adding ketamine 0.25 mg/kg to general anesthesia on serum IL-6 levels during and after elective coronary artery bypass grafting (CABG). Thirty-one patients undergoing elective CABG were randomized to one of two groups and prospectively studied in a double-blind manner. The patients received either ketamine 0.25 mg/kg or a similar volume of isotonic sodium chloride solution in addition to large-dose fentanyl anesthesia. Blood samples for analysis of serum IL-6 levels were drawn before the operation; after CPB; 4, 24, and 48 h after surgery; and daily for 6 days beginning the third day postoperatively. Ketamine suppressed the serum IL-6 response immediately after CPB and 4, 24, and 48 h postoperatively (P < 0.05). During the first 7 days after surgery, the serum IL-6 levels in the ketamine group were significantly lower than those in the control group (P < 0.05). On Day 8 after surgery, IL-6 levels were no different from baseline values in both groups. A single dose of ketamine 0.25 mg/kg administered before CPB suppresses the increase of serum IL-6 during and after CABG.

IMPLICATIONS

In this randomized, double-blind, prospective study of patients during and after coronary artery bypass surgery, we examined whether small-dose ketamine added to general anesthesia before cardiopulmonary bypass suppresses the increase of the serum interleukin-6 (IL-6) concentration. Serum IL-6 levels correlate with the patient's clinical course during and after coronary artery bypass. Ketamine suppresses the increase of serum IL-6 during and after coronary artery bypass surgery.

Use of EEG spectral edge as index of equipotency in a comparison of propofol and isoflurane for maintenance of general anaesthesia

Propofol and isoflurane were compared for haemodynamic stability and recovery time as main anaesthetic agents for maintenance in a total of 43 ASA I and II patients in uncomplicated operations lasting at least 30 min. The premedication (oral diazepam), induction (thiopentone-fentanyl-suxamethonium) and maintenance protocol (N2O-O2 2:1 litre min-1, fentanyl and vecuronium in incremental doses) were identical for all patients. In one group of 20 patients, propofol was used in continuous intravenous (i.v.) infusion (starting dose 3 mg kg-1 h-1), while in the second group of 23 patients, isoflurane was administered in a starting concentration of 1%. To improve the equipotency of the two agents in all cases the dose of the main anaesthetic was titrated to keep the EEG 90% spectral edge frequency (SEF-recorded by processed EEG monitor) between 8 and 12 Hz. Mean blood pressure (BP) and heart rate (HR) deviations of +/- 20% from the baseline were recorded. The incidence of mean blood pressure deviations/case in the propofol group was less than half of those occurring in the isoflurane group (0.45 vs. 0.96 P = 0.04). The mean duration of blood pressure deviation from baseline value was 5.5 min in the propofol group vs. 16.8 min in the isoflurane group (P = 0.01). The recovery intervals were significantly shorter in the propofol group (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of depth of general anesthesia. Observations on processed EEG and spectral edge frequency

The daily use of muscle relaxants and the lack of correlation between the hemodynamic behavior and stages of general anesthesia represent the main obstacles in defining the level of cortical activity depression by the anesthetic drugs. Since classical EEG is cumbersome in the operating room, and demands special knowledge, computerized methods of EEG wave analysis have more or less replaced the 'raw' display of the electrical activity of CNS. The paper describes the place of spectral edge frequency (SEF), one of the parameters obtained by processing the EEG waves, in the list of variables which could be monitored during general anesthesia. Besides, our preliminary observations on a combination of mean blood pressure variations and SEF value are presented. In fact, we designed a hypothetical matrix of those two parameters, which seems to be a useful tool for guiding the general anesthesia. SEF kept in a pre-established range (usually 8-12 Hz) seems to be linked with a more evident hemo-dynamic stability. Some data also suggested that a stable SEF on that range contributed to a higher degree of immediate postoperative analgesia after Cesarean section. The limits of SEF oblige the scientists to go on looking for other monitored parameters, to be studied in correlation with processed EEG. Further studies are needed, in order to improve the anesthesiologist's capabilities to define correctly the stage of general anesthesia.

Cannulation of big arteries in critically ill patients

A retrospective evaluation of 350 axillary and femoral artery cannulations in ICU patients revealed a 6.3-day mean duration of catheterization. Minor incidents such as hematoma (3.7%), catheter malfunction (5.1%), and local inflammation (2.5%) were noticed. The catheter was removed in 25 patients in whom it was suspected of causing sepsis. Six septic patients had the same organism in catheter and arterial blood cultures (with a negative venous blood culture), probably denoting an infected, catheter-linked thrombus. In 241 cases the catheter was removed at the end of the monitoring period. In only 21 of these cases did an organism grow in the catheter culture, but in 18 of these cases, the same organism was found in previous blood, sputum, and/or urine cultures. Thus, in only six patients (of 266 survivors) could arterial cannulation be held responsible for generalized sepsis. However, because no bacteriologic study was performed on catheters removed after the patient's death, this number could have been higher. Percutaneous axillary and femoral artery cannulation is highly recommended for extended monitoring because of its low incidence of minor complications, and no evident danger of tissue ischemia.

Toward a unified monitoring system during anesthesia

A conceptual framework is proposed for the selection of monitored parameters during anesthesia, and a new device for monitoring the parameters in a unified manner is briefly presented. A 'basic set' of 6 parameters is proposed to cover the needs of most routine anesthesia: Blood Pressure, ECG/Heart Rate, Temperature, FiO2, FetCO2, and, Cortical Activity (by EEG spectral analysis). Additional parameters are added in accordance with specified factors such as patient status and complexity of the surgical procedure. An initial version of a new monitor, 'Cerebro Trac', designed for neurosurgery and cardiovascular surgery, is briefly presented, along with planned future capabilities and directions for its use.