Biomedical subjects
M Vucevic
Publications and source records attributed to M Vucevic.
Hemodynamic consequences of high- and low-pressure capnoperitoneum during laparoscopic cholecystectomy.
BACKGROUND: Peritoneal insufflation to 15 mmHg diminishes venous return and reduces cardiac output. Such changes may be dangerous in patients with a poor cardiac reserve. The aim of this study was to investigate the hemodynamic effects of high (15 mmHg) and low (7 mmHg) intraabdominal pressure during laparoscopic cholestectomy (LC) METHODS: Twenty patients were randomized to either high- or low-pressure capnoperitoneum. Anesthesia was standardized, and the end-tidal CO2 was maintained at 4.5 kPa. Arterial blood pressure was measured invasively. Heart rate, stroke volume, and cardiac output were measured by transesophageal doppler. RESULTS: There were 10 patients in each group. In the high-pressure group, heart rate (HR) and mean arterial blood pressure (MABP) increased during insufflation. Stroke volume (SV) and cardiac output were depressed by a maximum of 26% and 28% (SV 0.1 > p > 0.05, cardiac output p > 0. 1). In the low-pressure group, insufflation produced a rise in MABP and a peak rise in both stroke volume and cardiac output of 10% and 28%, respectively (p < 0.05). CONCLUSIONS: Low-pressure pneumoperitoneum is feasible for LC and minimizes the adverse hemodynamic effects of peritoneal insufflation.
Urine colour as an index of hydration in critically ill patients.
In order to test the hypothesis that urine colour can be used as an index of hydration in critically ill patients, we selected 40 intensive care and high-dependency patients and correlated urine colour (scored on an eight-point scale) with various indices of hydration: urine:plasma sodium, osmolality and urea ratios, urine output and central venous pressure. In addition, we compared the colour-chart score with scores made by intensive care nurses (without the benefit of a colour chart) in order to test subjective assessment of urine colour. There were weak but statistically significant correlations between urine colour and urine output (Spearman's r = - 0.555) and between urine colour and urine:plasma sodium ratio (Spearman's r = - 0.459). Subjective assessment of urine colour appeared to be reliable. Thus, although urine colour does vary with hydration in the critically ill, assessment of urine colour adds little to the overall assessment of hydration in this group of patients.
Patient-controlled sedation using propofol in elderly patients in day-case cataract surgery.
Patient-controlled sedation (PCS) with propofol has been used successfully as an adjunct to local anaesthetic procedures. We studied a group of elderly patients (mean age 75.4 yr) undergoing cataract surgery and attempted to increase patient acceptability and comfort of local anaesthesia. Propofol was self-administered in a dose of 0.25 mg kg-1 for patients more than 60 yr of age, with a lockout period of 3 min. A total of 14 of 20 patients used PCS; eight of 20 used the PCS only once and another six had three tries or less. Despite this, 18 of 20 patients claimed they found the PCS useful. However, while it is possible to administer PCS successfully to elderly patients undergoing cataract surgery and produce a decrease in the level of anxiety, we found it unacceptable because of head movement in two patients. These patients received only two and three divided doses, to a maximum of 29 and 30 mg, respectively. There were no other adverse events.
Analgesia after intracranial surgery: a double-blind, prospective comparison of codeine and tramadol.
We have compared codeine and tramadol in a prospective, double-blind study of postoperative analgesia in 75 patients after elective intracranial surgery. Twenty-five patients received codeine 60 mg, tramadol 50 mg or tramadol 75 mg i.m. Patients receiving codeine had significantly lower pain scores over the first 48 h after operation (P < 0.0001). Although there was no difference in visual analogue scale (VAS) scores between the three groups at 24 h, the codeine group had significantly lower scores at 48 h (P < 0.0001). The tramadol 75 mg group had significantly higher scores for both sedation and nausea and vomiting (P < 0.0001 for both scores). We conclude that codeine 60 mg i.m. provided better postoperative analgesia than tramadol after craniotomy and that tramadol 75 mg should be avoided because of its side effects of increased sedation and nausea and vomiting.
The haemodynamic effects of propofol in combination with ephedrine in elderly patients (ASA groups 3 and 4).
The marked vasodilator and negative inotropic effects of propofol are disadvantages in frail elderly patients. We investigated the safety and efficacy of adding different doses of ephedrine to propofol in order to obtund the hypotensive response. The haemodynamic effects of adding 15, 20 or 25 mg of ephedrine to 200 mg of propofol were compared to control in 40 ASA 3/4 patients over 60 years presenting for genito-urinary surgery. The addition of ephedrine to propofol appears to be an effective method of obtunding the hypotensive response to propofol at all doses used in this study. However, marked tachycardia associated with the use of ephedrine in combination with propofol occurred in the majority of patients, occasionally reaching high levels in individual patients. Due to the risk of this tachycardia inducing myocardial ischemia, we would not recommend the use in elderly patients of any of the ephedrine/propofol/mixtures studied.
Comparison of air tonometry with gastric tonometry using saline and other equilibrating fluids: an in vivo and in vitro study.
OBJECTIVE: 1) To compare saline gastric tonometry monitoring with air tonometry (Tonocap) in a group of general ICU patients. 2) An in vitro investigation of the performance of other fluids used in gastric tonometry and to assess the effects of variation of temperature and carbon dioxide concentration within the range encountered in clinical use. DESIGN: a) A prospective, observational study in ICU patients b) A comparative laboratory study. SETTING: The general Intensive Care Unit (ICU) and the laboratory at Leeds General Infirmary. PATIENTS AND PARTICIPANTS: Nine patients in the general ICU with severe sepsis or septic shock. MEASUREMENTS AND RESULTS: In vivo comparison of saline and air tonometry demonstrated a difference between the two techniques. Bland & Altman analysis showed a mean bias in the measurement of gastric PCO2 of 1.88 kPa with a precision of 1.22 kPa, with saline giving the lower result. In vitro, saline, air (Tonocap), gelatin and heparinised blood were used, at temperatures of 33-42 degrees C and at carbon dioxide concentrations of 4-8 kPa. While gelatin and blood gave unpredictable results, dependent on temperature and carbon dioxide concentration, air tonometry gave highly reproducible results. A consistent bias between the results with saline and air tonometry was seen over the range of temperatures and carbon dioxide (CO2) concentrations studied. The mean bias was 0.85 kPa with a precision of 0.40 kPa, saline consistently giving lower results. CONCLUSIONS: There are clinically significant differences in values for gastric mucosal PCO2 measured by air tonometry and saline tonometry both in vivo and in vitro.
Regional anaesthesia with a subarachnoid microcatheter for caesarean section in a parturient with aortic stenosis.
We present a woman in her first pregnancy, with known aortic stenosis prior to conception, who successfully underwent regional anaesthesia for an elective Caesarean section using a subarachnoid microcatheter. The anaesthetic management of patients with aortic stenosis requiring noncardiac surgery is a complex and contentious matter, particularly when the situation is compounded by the physiological changes accompanying pregnancy and delivery. This is the first reported use of a subarachnoid microcatheter in such a patient. The choice of technique is discussed and compared with other options for providing anaesthesia.
Use of the Combitube for airway maintenance during percutaneous dilatational tracheostomy.
The Combitube airway allows short-term ventilation during cardiopulmonary resuscitation and can be useful in the management of the difficult airway. In a prospective observational study we assessed its use during percutaneous dilatational tracheostomy (PDT). Twenty-one intensive care patients scheduled for elective PDT had their tracheal tube replaced by a Combitube airway retaining the same ventilator settings. Arterial blood gases, airway pressures, SpO2 and end-tidal CO2 were measured as were the transmural pressures exerted by the Combitube cuffs. Combitube placement was successful in 20 of 21 patients although adequate ventilation was possible in only 17 (85%). There was no significant change in PaO2, SpO2, end-tidal CO2, Paco2 or mean airway pressure during Combitube ventilation. A high mean (SD) transmural pressure of 14.7 (5) kPa was exerted by the distal cuff. The Combitube provided a satisfactory alternative airway to the tracheal tube during performance of PDT in 85% of our patients. Potential problems associated with its use in intensive care patients are outlined.
Esophageal rupture associated with the use of the Combitube.
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Lack of agreement between bioimpedance and continuous thermodilution measurement of cardiac output in intensive care unit patients.
BACKGROUND: Bolus thermodilution is the standard bedside method of cardiac output measurement in the intensive care unit (ICU). The Baxter Vigilance monitor uses a modified thermodilution pulmonary artery catheter with a thermal filament to give a continuous read-out of cardiac output. This has been shown to correlate very well with both the 'gold standard' dye dilution method and the bolus thermodilution method. Bioimpedance cardiography using the Bomed NCCOM 3 offers a noninvasive means of continuous cardiac output measurement and has been shown to correlate with the bolus thermodilution method. We investigated the agreement between the continuous bioimpedance and continuous thermodilution methods, enabling acquisition of a large number of simultaneous measurements. RESULTS: A total of 2390 paired data points from seven patients were collected. There was no correlation (r2 = 0.01) between the methods. The precision (1.16 l/min/m2) of agreement between the Vigilance and the Bomed, assessed by the Bland-Altam method, was very poor although the bias (-0.16 l/min/m2) appeared fair. CONCLUSIONS: The Bomed NCCOM 3 bioimpedance monitor shows poor agreement with the Baxter Vigilance continuous thermodilution monitor in a group of general ICU patients and cannot be recommended for cardiac output monitoring in this situation.
The reinforced laryngeal mask airway for dento-alveolar surgery.
We have evaluated the reinforced laryngeal mask airway (LMA) for use during dento-alveolar surgery in 100 ASA I and II day-case patients allocated randomly to receive either a nasotracheal tube or reinforced LMA. We recorded ease of airway insertion, airway complications, quality of recovery and replies to a 24-h postoperative questionnaire. In addition, a fibreoptic assessment was made of laryngotracheal soiling, and the effect of head movement and the position of the reinforced LMA. There were no significant differences in difficulty in airway positioning or perioperative oxygen desaturation. Nineteen patients in the nasotracheal tube group had epistaxis (P = 0.001) and laryngotracheal soiling occurred in three of these patients. Two reinforced LMA were dislodged on moving into the operating theatre and in a further five patients in this group there was partial airway obstruction (compared with none in the nasotracheal tube group; P = 0.018) which was caused by downward pressure on the mandible by the surgeon. There were no differences in postoperative complications. No surgeon reported poor access to the operating field. Overall the reinforced LMA provided satisfactory conditions for this surgery but vigilance of the airway was required, especially at the time of extraction.
The haemodynamic effects of propofol in combination with ephedrine.
Forty ASA1 patients presenting for minor gynaecological surgery were randomly allocated into four study groups to compare the haemodynamic effects of adding different doses of ephedrine to an induction dose of propofol. Heart rate, oxygen saturation and non-invasive arterial blood pressure were monitored before and for 5 min after induction. In those patients who received propofol alone, there was a significant decrease in both systolic (p < 0.001) and diastolic (p = 0.003) blood pressure. The addition of ephedrine 15 mg or 20 mg to 1% propofol 20 ml was very effective in maintaining blood pressure at pre-induction values. There was a statistically significant increase from baseline in systolic (p = 0.004) and diastolic (p = 0.031) pressures, but this only occurred at 1 min postinduction. The addition of ephedrine 10 mg was insufficient to prevent hypotension. There was no significant effect on either heart rate or oxygen saturation in any group. We conclude that ephedrine may be safely employed to reduce the degree of hypotension during induction with propofol in this patient group.
SCOTI device for detection of tracheal intubation.
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Peripheral analgesic effect of morphine.
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The SMART needle. A new Doppler ultrasound-guided vascular access needle.
Central venous access is an essential part of patient management in many clinical settings. Traditionally this has been achieved by a blind, external landmark guided technique which may not correlate exactly with the location of the vessel. We have prospectively evaluated the SMART needle, a new Doppler ultrasound guided vascular access device, in 40 patients, to evaluate whether it can improve on the standard technique. The SMART needle was easy to use and reliably distinguished between arterial and venous signals. No advantage was demonstrated in 'easy' internal jugular vein cannulations. Although ease of cannulation in difficult cases was subjectively improved, the differences in time to cannulation and number of passes between the groups failed to reach statistical significance and the complication rates were similar. However, the use of the SMART needle on two occasions enabled avoidance of carotid artery puncture by correctly distinguishing the artery from the vein, so that it may have a rôle in patients in whom difficult internal jugular venous cannulation is anticipated.
Not awake, not asleep, not dead?
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Esmolol hydrochloride for management of the cardiovascular stress responses to laryngoscopy and tracheal intubation.
In a double-blind, randomized, controlled prospective study, 30 grade ASA I/II patients received a continuous i.v. infusion of normal saline or esmolol hydrochloride before induction of anaesthesia and tracheal intubation. Arterial pressure and heart rate were measured to assess the pressor response to laryngoscopy and intubation. The heart rate decreased in the esmolol group before induction of anaesthesia. The pressor response to laryngoscopy was significantly less marked in the esmolol group.