Effects of pneumoperitoneum and reverse Trendelenburg position on cardiopulmonary function in morbidly obese patients receiving laparoscopic gastric banding

Estimating Arterial Partial Pressure of Carbon Dioxide in Ventilated Patients: How Valid Are Surrogate Measures?

The arterial partial pressure of carbon dioxide (Pa_CO2) is an important parameter in critically ill, mechanically ventilated patients. To limit invasive procedures or for more continuous monitoring of Pa_CO2, clinicians often rely on venous blood gases, capnography, or transcutaneous monitoring. Each of these has advantages and limitations. Central venous Pco₂ allows accurate estimation of Pa_CO2, differing from it by an amount described by the Fick principle. As long as cardiac output is relatively normal, central venous Pco₂ exceeds the arterial value by approximately 4 mm Hg. In contrast, peripheral venous Pco₂ is a poor predictor of Pa_CO2, and we do not recommend using peripheral venous Pco₂ in this manner. Capnography offers measurement of the end-tidal Pco₂ (Pet_CO2), a value that is close to Pa_CO2 when the lung is healthy. It has the advantage of being noninvasive and continuously available. In mechanically ventilated patients with lung disease, however, Pet_CO2 often differs from Pa_CO2, sometimes by a large degree, often seriously underestimating the arterial value. Dependence of Pet_CO2 on alveolar dead space and ventilator expiratory time limits its value to predict Pa_CO2. When lung function or ventilator settings change, Pet_CO2 and Pa_CO2 can vary in different directions, producing further uncertainty. Transcutaneous Pco₂ measurement has become practical and reliable. It is promising for judging steady state values for Pa_CO2 unless there is overt vasoconstriction of the skin. Moreover, it can be useful in conditions where capnography fails (high-frequency ventilation) or where arterial blood gas analysis is burdensome (clinic or home management of mechanical ventilation).

Comparison of Arterial Oxygenation Following Head-Down and Head-Up Laparoscopic Surgery

BACKGROUND

Regarding the role of gas entry in abdomen and cardiorespiratory effects, the ability of anesthesiologists would be challenged in laparoscopic surgeries. Considering few studies in this area and the relevance of the subject, this study was performed to compare the arterial oxygen alterations before operation in comparison with after surgery between laparoscopic cholecystectomy and ovarian cystectomy.

METHODS

In this prospective cohort, 70 consecutive women aged from 20 to 60 years who were candidate for laparoscopic cholecystectomy (n = 35) and ovarian cystectomy (n = 35) with reverse (20 degrees) and direct (30 degrees) Trendelenburg positions, respectively, with ASA class I or II were enrolled. After intubation and before operation, for the first time, the arterial blood gas from radial artery in supine position was obtained for laboratory assessment. Then, the second blood sample was collected from radial artery in supine position and sent to the lab to be assessed with the same device after 30 minutes from surgery termination. The measured variables from arterial blood gas were arterial partial pressure of oxygen (PaO2) and Oxygen saturation (SpO2) alterations.

RESULTS

Total PaO2 was higher in the first measurement. The higher values of PaO2 in cholecystectomy (upward) than in ovarian cystectomy (downward) were not significant in univariate (P = 0.060) and multivariate analysis (P = 0.654). Furthermore, higher values of SpO2 in cholecystectomy (upward) than in ovarian cystectomy (downward) were not significant in univariate (P = 0.412) and multivariate analysis (P = 0.984).

CONCLUSIONS

In general, based on the results of this study, the values of PaO2 in cholecystectomy (upward) were not significantly higher than the values in cystectomy (downward) in laparoscopic surgeries when measured 30 minutes after surgery.

Assessment of Ventilation Distribution during Laparoscopic Bariatric Surgery: An Electrical Impedance Tomography Study

Introduction. The aim of the study was to assess changes of regional ventilation distribution at the level of the 3rd intercostal space in the lungs of morbidly obese patients as a result of general anaesthesia and laparoscopic surgery as well as the relation of these changes to lung mechanics. We also wanted to determine if positive end-expiratory pressure of 10 cm H₂O prevents the expected atelectasis in the morbidly obese patients during general anaesthesia. Materials and Methods. 49 patients completed the examination and were randomized to 2 groups: ventilated without positive end-expiratory pressure (PEEP 0) and with PEEP of 10 cm H₂O (PEEP 10) preceded by a recruitment maneuver with peak inspiratory pressure of 40 cm H₂O. Impedance Ratio (IR) was utilized to examine ventilation distribution changes as a result of anaesthesia, pneumoperitoneum, and change of body position. We also analyzed intraoperative respiratory mechanics and pulse oximetry values. Results. In both groups general anaesthesia caused a ventilation shift towards the nondependent lungs which was not further intensified after pneumoperitoneum. Reverse Trendelenburg position promoted homogeneous ventilation distribution. Respiratory system compliance was reduced after insufflation and improved after exsufflation of pneumoperitoneum. There were no statistically significant differences in ventilation distribution between the examined groups. Respiratory system compliance, plateau pressure, and pulse oximetry values were higher in PEEP 10. Conclusions. Changes of ventilation distribution in the obese do occur at cranial lung regions. During pneumoperitoneum alterations of ventilation distribution may not follow the direction of the changes of lung mechanics. In the obese patients PEEP level of 10 cm H₂O preceded by a recruitment maneuver improves respiratory compliance and oxygenation but does not eliminate atelectasis induced by general anaesthesia.

Bilateral otorrhagia: a rare complication of laparoscopic abdominopelvic surgery

An 80-year-old woman without any previous otological symptoms underwent laparoscopic abdominoperineal resection for T3N0M0 low rectal carcinoma 4-5 cm from the anal verge. The total operative time was 6 h, of which she spent long hours in the Trendelenburg (35°) position due to difficult pelvic dissection. Midway through the procedure, she developed spontaneous non-traumatic bilateral otorrhagia. This case highlights the potential risk of increased intracranial pressure during prolonged periods of being in a steep Trendelenburg position caused either by the position itself or in combination with carbon dioxide pneumoperitoneum. We also consider the effect of a sudden change from this position to supine as a potential risk.

Laparoscopic approach to acute abdomen from the Consensus Development Conference of the Società Italiana di Chirurgia Endoscopica e nuove tecnologie (SICE), Associazione Chirurghi Ospedalieri Italiani (ACOI), Società Italiana di Chirurgia (SIC), Società Italiana di Chirurgia d'Urgenza e del Trauma (SICUT), Società Italiana di Chirurgia nell'Ospedalità Privata (SICOP), and the European Association for Endoscopic Surgery (EAES)

BACKGROUND

In January 2010, the SICE (Italian Society of Endoscopic Surgery), under the auspices of the EAES, decided to revisit the clinical recommendations for the role of laparoscopy in abdominal emergencies in adults, with the primary intent being to update the 2006 EAES indications and supplement the existing guidelines on specific diseases.

METHODS

Other Italian surgical societies were invited into the Consensus to form a panel of 12 expert surgeons. In order to get a multidisciplinary panel, other stakeholders involved in abdominal emergencies were invited along with a patient's association. In November 2010, the panel met in Rome to discuss each chapter according to the Delphi method, producing key statements with a grade of recommendations followed by commentary to explain the rationale and the level of evidence behind the statements. Thereafter, the statements were presented to the Annual Congress of the EAES in June 2011.

RESULTS

A thorough literature review was necessary to assess whether the recommendations issued in 2006 are still current. In many cases new studies allowed us to better clarify some issues (such as for diverticulitis, small bowel obstruction, pancreatitis, hernias, trauma), to confirm the key role of laparoscopy (such as for cholecystitis, gynecological disorders, nonspecific abdominal pain, appendicitis), but occasionally previous strong recommendations have to be challenged after review of recent research (such as for perforated peptic ulcer).

CONCLUSIONS

Every surgeon has to develop his or her own approach, taking into account the clinical situation, her/his proficiency (and the experience of the team) with the various techniques, and the specific organizational setting in which she/he is working. This guideline has been developed bearing in mind that every surgeon could use the data reported to support her/his judgment.

Effects of four intraoperative ventilatory strategies on respiratory compliance and gas exchange during laparoscopic gastric banding in obese patients

BACKGROUND

Respiratory function is impaired in obese patients undergoing laparoscopic surgery. This study was performed to determine whether repeated lung recruitment combined with PEEP improves respiratory compliance and arterial partial pressure of oxygen (Pa(O2)) in obese patients undergoing laparoscopic gastric banding.

METHODS

Sixty patients with BMI >30 kg m(-2) were randomized, after induction of pneumoperitoneum, to receive either PEEP of 10 cm H2O (Group P), inspiratory pressure of 40 cm H2O for 15 s once (Group R), Group R recruitment followed by PEEP 10 cm H2O (Group RP), or Group RP recruitment but with the inspiratory manoeuvre repeated every 10 min (Group RRP). Static respiratory compliance and Pa(O2) were determined after intubation, 10 min after pneumoperitoneum (before lung recruitment), and every 10 min thereafter (after recruitment). Results are presented as mean (SD).

RESULTS

Pneumoperitoneum decreased respiratory compliance from 48 (3) to 30 (1) ml cm H2O(-1) and decreased Pa(O2) from 12.4 (0.3) to 8.8 (0.3) kPa in all groups (P<0.01). Immediately after recruitment, compliance was 32 (1), 32 (2), 40 (2), and 40 (1) ml cm H2O(-1) and Pa(O2) was 9.1 (0.3), 9.1 (0.1), 11.9 (0.1), and 11.9 (0.1) kPa in Groups P, R, RP, and RRP, respectively (P<0.01). Ten and 20 min later, Pa(O2) in Group R decreased to 9.2 (0.1) kPa and compliance in Group PR decreased to 33 (2) ml cm H2O(-1), respectively (P<0.01).

CONCLUSIONS

Group RRP recruitment strategy was associated with the best intraoperative respiratory compliance and Pa(O2) in obese patients undergoing laparoscopic gastric banding.

Anesthetic complications of gross obesity

PURPOSE OF REVIEW

The number of obese patients undergoing anesthesia and surgery is increasing. This article aims to present recent achievements in the management of gross and morbidly obese patients in order to improve safety.

RECENT FINDINGS

Current investigations have demonstrated that the type of anesthesia (total intravenous anesthesia or volatile) and the anesthetics used have an important influence on the perioperative period, especially on postanesthesia recovery and respiratory failure during the postoperative period. These findings were compared with previous publications. Practical advice is also presented for performing successful intubation and mechanical ventilation in the morbidly obese patient, as well as describing drug dosage and administration.

SUMMARY

The progress in anesthesia techniques and modern drugs allows for safe management of obese patients, with mortality decreasing in this group of patients.

Presurgical assessment of intraabdominal visceral fat in obese patients with early-stage endometrial cancer treated with laparoscopic approach: Relationships with early laparotomic conversions

STUDY OBJECTIVE

To evaluate the relationship between intraabdominal visceral fat (IVF) and early conversion from laparoscopy to laparotomy in obese patients.

DESIGN

Prospective study (Canadian Task Force classification II-2).

SETTING

Department of obstetrics and gynecology, University "Magna Graecia" of Catanzaro.

PATIENTS

One hundred fifty-one obese patients with endometrial cancer and laparoscopic surgery.

INTERVENTIONS

Laparoscopic treatment for early-stage endometrial cancer.

MEASUREMENT AND MAIN RESULTS

In all patients, demographic, anthropometric (including body mass index, waist-to-hip ratio, and waist circumference), and IVF assessments (using ultrasonography [IVF-USG, cm] and computed tomography [IVF-CT, cm(2)]), were evaluated. In 122 patients (122/151, 80.8%), the laparoscopies were successfully completed (group A), whereas 29 patients (29/151, 19.2%) had a laparotomic conversion. Specifically, in 19 (19/29, 65.5%) and in 10 patients (10/29, 34.5%) the conversion was early (group B1) and late (group B2), respectively. A significant (p <.05) difference in surgical stage IC and in postoperative complications rate was detected between group A and groups B1 and B2, without difference between these 2 last groups. IVF-USG and IVF-CT were significantly (p <.01) higher in group B1 in comparison with groups A and B2, without difference between these 2 last groups. A strong and significant (p <.001) association between IVF-USG and IVF-CT was detected in all groups by Spearman bivariate correlation (r = 0.78, 0.918, and 0.978 for group A, B1, and B2, respectively). Multivariate analysis showed the IVF-CT as the main predictor for early laparotomic conversion (OR 2.184; 95% CI 1.227-3.886).

CONCLUSIONS

Intraabdominal visceral fat is a predictor for early laparotomic conversion in obese patients with endometrial cancer. Further studies are necessary to assess the efficacy of the IVF evaluation for reducing the laparotomic conversion risk in obese women undergoing laparoscopic surgery for gynecologic malignancy.

Anesthesia in the obese patient: Pharmacokinetic considerations

The prevalence of obesity has increased 15% up to 20% and represents an important challenge for the anesthesiologist in drug-dosing management. The aim of this work is to provide an overview on physiological changes and pharmacokinetic implications of obesity for the anesthesiologist. Obesity increases both fat and lean masses; however, the percentage of fat tissue increases more than does the lean mass, affecting the apparent volume of distribution of anesthetic drugs according to their lipid solubility. Benzodiazepine loading doses should be adjusted on actual weight, and maintenance doses should be adjusted on ideal body weight. Thiopental sodium and propofol dosages are calculated on total body weight (TBW). The loading dose of lipophilic opioids is based on TBW, whereas maintenance dosages should be cautiously reduced because of the higher sensitivity of the obese patient to their depressant effects. Pharmacokinetic parameters of muscle relaxants are minimally affected by obesity, and their dosage is based on ideal rather than TBW. Inhalation anesthetics with very low lipid solubility, such as sevoflurane and desflurane, allow for quick modification of the anesthetic plan during surgery and rapid emergence at the end of surgery, hence representing very flexible anesthetic drugs for use in this patient population. Drug dosing is generally based on the volume of distribution for the loading dose and on the clearance for maintenance. In the obese patient, the volume of distribution is increased if the drug is distributed both in lean and fat tissues whereas the anesthetic drug clearance is usually normal or increased.

Transdiaphragmatic pressure control of airway pressure support in healthy subjects

We designed a new servoventilator that proportionally adjusts airway pressure to transdiaphragmatic pressure (Pdi) generated by the subject during inspiration. Each cycle is triggered by either a preset Pdi increase or a preset inspiratory flow value (whichever is reached first), whereas cycling-off is flow-dependent. We evaluated the servoventilator in seven healthy subjects at normocapnia and three levels of hypercapnia (normocapnia + 3, + 6, and + 9 mm Hg) comparatively with spontaneous breathing. Triggering was by Pdi in six subjects and flow in one. At all end-tidal carbon dioxide pressure levels, time from onset of diaphragm electromyographic activity to inspiratory flow was similar with and without the servoventilator. Airway pressure increased proportionally to Pdi variation during servoventilator breathing. Flow, tidal volume, respiratory rate, intrinsic positive end-expiratory pressure, and esophageal and transdiaphragmatic pressure-time products increased significantly with hypercapnia with and without the servoventilator. Breathing pattern parameters were similar in the two breathing modes, and no differences were found for intrinsic positive end-expiratory pressure or gastric pressure variation during exhalation. Esophageal and transdiaphragmatic pressure-time products were lower with than without the servoventilator. The Pdi-driven servoventilator was well synchronized to the subjects effort, delivering a pressure proportional to Pdi and reducing respiratory effort at normocapnia and hypercapnia.

Respiratory mechanics in morbid obese patients with chronic obstructive pulmonary disease and hypertension during pneumoperitoneum

BACKGROUND AND OBJECTIVE

To evaluate the effects of pneumoperitoneum and the reverse Trendelenburg position on respiratory mechanics and blood-gases in morbid obese patients with chronic obstructive pulmonary disease and hypertension.

METHODS

Sixteen morbid obese patients with chronic obstructive pulmonary disease and hypertension were studied. Mean arterial pressure, heart rate, respiratory resistance, dynamic respiratory compliance and peak inspiratory pressures were measured at four time points: 5 min after induction of anaesthesia (T1), 5 min after insufflation of the peritoneum (T2), 5 min after adoption of a 20 degrees reverse Trendelenburg position (T3), and 5 min after deflation of the peritoneum (T4). Arterial blood-gas status was measured at the same measuring points.

RESULTS

Respiratory compliance was 40 +/- 12, 28 +/- 8, 32 +/- 8 and 37 +/- 11 mL cm H2O(-1) in T1, T2, T3 and T4, respectively. The changes were significant at T2, T3 and T4. Airway resistance and peak inspiratory pressures showed comparable changes throughout the study with that of respiratory compliance. Haemodynamic measurements showed no clinically significant changes in this study.

CONCLUSIONS

In morbid obese patients with chronic obstructive pulmonary disease and hypertension, a 20 degrees reverse Trendelenburg position improved respiratory mechanics and oxygenation without any apparent adverse effects on haemodynamics during laparoscopic gastric banding surgery.

The effects of tidal volume and respiratory rate on oxygenation and respiratory mechanics during laparoscopy in morbidly obese patients

Morbidly obese (MO) patients undergoing laparoscopy have lower PaO(2) compared with normal-weight (NW) patients. We hypothesized that increases in tidal volume (V(T)) or respiratory rate (RR) would improve oxygenation. All measurements were performed at: 1) baseline: V(T) 600-700 mL and 10 breaths/min, 2) double V(T): V(T) 1200-1400 mL and 10 breaths/min, and 3) double rate: V(T) 600-700 mL and 20 breaths/min. We calculated static respiratory system compliance (Cst,rs) and inspiratory resistance (RI,rs). End-tidal CO(2) was measured with a mass spectrometer, and PaO(2) and PaCO(2) with a continuous blood gas monitor. Supine anesthetized MO patients had 29% lower Cst,rs than the NW patients (P < 0.05). Positioning patients head-up or head-down before pneumoperitoneum did not significantly affect Cst,rs in either group (P = 0.8). Doubling the V(T), but not RR, increased Cst,rs in both groups. Pneumoperitoneum caused large decreases in Cst,rs in both groups (both P < 0.001). During pneumoperitoneum, changing the body position, V(T), or RR did not further affect Cst,rs in either group (P > 0.7). Before pneumoperitoneum, RI,rs was higher in the MO patients compared with the NW patients regardless of body position (P = 0.01). Doubling either RR or V(T) before pneumoperitoneum did not change RI,rs in either group. After pneumoperitoneum, RI,rs increased in both the head-down and head-up positions (P < 0.05), but not in the supine position. Regardless of the conditions studied, alveolar-arterial difference in oxygen tension was always significantly higher in MO patients (P < 0.05). The alveolar-arterial difference in oxygen tension was not affected by body position, pneumoperitoneum, or the mode of ventilation. Arterial oxygenation during laparoscopy was affected only by body weight and could not be improved by increasing either the V(T) or RR.

IMPLICATIONS

Morbid obesity decreases arterial oxygenation and respiratory system compliance. During laparoscopy, arterial oxygenation is affected only by the patient's body weight. Increases in tidal volume or respiratory rate do not improve arterial oxygenation.

Cricoid yoke: the effect of surface area and applied force on discomfort experienced by conscious volunteers

BACKGROUND AND OBJECTIVE

The application of cricoid force is central to techniques that reduce the risk of gastric regurgitation and the subsequent pulmonary aspiration associated with obstetric and emergency anaesthesia. The discomfort associated with cricoid force in awake preoperative patients increases the incidence of coughing, struggling and pain during induction of anaesthesia. This study determined if increasing the surface area of a cricoid yoke reduced the associated discomfort in volunteers.

METHODS

Fifty volunteers participated in a randomized single-blinded study. The cricoid yoke was positioned using standard anatomical landmarks and forces of 10, 20, 30 and 40 N were applied in a random order for 20s, using two different yoke attachments with surface areas of 3 and 10 cm2. A rest of 30s was allowed between the application of forces. Discomfort was graded by volunteers on a scale from 0 to 10 (0: no discomfort; 10: worse discomfort imaginable). A score of 10 was allocated if the volunteers could not tolerate the applied force for 20s.

RESULTS

Median scores for the small yoke were always higher than those for the large yoke at each force. There were significant differences between the scores for the small and large yokes at 10 and 20 N (P < 0.001) and 30 N (P = 0.0233), but there was no significant difference at 40 N.

CONCLUSIONS

The larger yoke was tolerated better by volunteers when clinically relevant cricoid forces were applied.

Tracheal intubation without muscle relaxants: remifentanil or alfentanil in combination with propofol

BACKGROUND AND OBJECTIVE

In some situations, the use of muscle relaxants (neuromuscular blocking drugs) are undesirable or contraindicated. We compared intubating conditions without muscle relaxants in premedicated patients receiving either alfentanil 40 microg kg(-1) or remifentanil 2, 3 or 4 microg kg(-1) followed by propofol 2 mg kg(-1).

METHODS

In a randomized, double-blind study, 80 healthy patients were assigned to one of four groups (n = 20). After intravenous atropine, alfentanil 40 microg kg(-1) or remifentanil 2, 3 or 4 microg kg(-1) were injected over 90 s followed by propofol 2 mg kg(-1). Ninety seconds after administration of the propofol, laryngoscopy and tracheal intubation were attempted. Intubating conditions were assessed as excellent, good or poor on the basis of ease of lung ventilation, jaw relaxation, laryngoscopy, position of the vocal cords, and patient response to intubation and slow inflation of the endotracheal tube cuff.

RESULTS

Seven patients who received remifentanil 2 microg kg(-1) and one patient who received remifentanil 3 microg kg(-1) could not be intubated at the first attempts. Excellent intubating conditions (jaw relaxed, vocal cords open and no movement in response to tracheal intubation and cuff inflation) were observed in those who received either alfentanil 40 microg kg(-1) (45% of patients) or remifentanil in doses of 2 microg kg(-1) (20%), 3 microg kg(-1) (75%) or 4 microg kg(-1) (95%). Overall, intubating conditions were significantly better (P < 0.05), and the number of patients showing excellent conditions were significantly higher (P < 0.05) in patients who received remifentanil 4 microg kg(-1) compared with those who received alfentanil 40 microg kg(-1) or remifentanil 2 microg kg(-1). No patient needed treatment for hypotension or bradycardia.

CONCLUSIONS

Remifentanil 4 microg kg(-1) and propofol 2 mg kg(-1) administered in sequence intravenously provided good or excellent conditions for tracheal intubation in all patients without the use of muscle relaxants.

Stability of the LMA-ProSeal and standard laryngeal mask airway in different head and neck positions: a randomized crossover study

BACKGROUND AND OBJECTIVE

The LMA-ProSeal laryngeal mask airway is a new laryngeal mask airway with a modified cuff and drainage tube. We compared oropharyngeal leak pressure, intracuff pressure and anatomical position (assessed fibreoptically) for the Size 5 LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway in different head-neck positions and using different intracuff inflation volumes.

METHODS

Thirty paralysed anaesthetized adult male patients were studied. The LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway were inserted into each patient in random order. The oropharyngeal leak pressure, intracuff pressure, and anatomical position of the airway tube and drainage tube (LMA-ProSeal laryngeal mask airway only) were documented in four head and neck positions (neutral first, then flexion, extension and rotation in random order), and at 0-40 mL cuff volumes in the neutral position in 10 mL increments.

RESULTS

Compared with the neutral position, the oropharyngeal leak pressure for both the LMA-ProSeal laryngeal mask airway and the classic laryngeal mask airway was higher in flexion and rotation (all P < or = 0.02), but lower in extension (all P < or = 0.01). Changes in head-neck position did not alter the anatomical position of the airway tube or the drainage tube. The oropharyngeal leak pressure was always higher for the LMA-ProSeal laryngeal mask airway (all P < or = 0.005) and anatomical position better for the classic laryngeal mask airway (all P < or = 0.04).

CONCLUSIONS

The anatomical position of the LMA-ProSeal and the classic laryngeal mask airway is stable in different head-neck positions, but head-neck flexion and rotation are associated with an increase, and head-neck extension a decrease, in oropharyngeal leak pressure and intracuff pressure. The Size 5 LMA-ProSeal laryngeal mask airway is capable of forming a more effective seal than the Size 5 classic laryngeal mask airway in males.

Breathing pattern and workload during automatic tube compensation, pressure support and T-piece trials in weaning patients

BACKGROUND AND OBJECTIVE

Automatic tube compensation has been designed as a new ventilatory mode to compensate for the non-linear resistance of the endotracheal tube. The study investigated the effects of automatic tube compensation compared with breathing through a T-piece or pressure support during a trial of spontaneous breathing used for weaning patients from mechanical ventilation of the lungs.

METHODS

Twelve patients were studied who were ready for weaning after prolonged mechanical ventilation (10.2 +/- 8.4 days) due to acute respiratory failure. Patients with chronic obstructive pulmonary disease were excluded. Thirty minutes of automatic tube compensation were compared with 30 min periods of 7 cmH2O pressure support and T-piece breathing. Breathing patterns and workload indices were measured at the end of each study period.

RESULTS

During T-piece breathing, the peak inspiratory flow rate (0.65 +/- 0.20 L s(-1)) and minute ventilation (8.9 +/- 2.7L min(-1)) were lower than during either pressure support (peak inspiratory flow rate 0.81 +/- 0.25 L s(-1) minute ventilation 10.2 +/- 2.3 L min(-1), respectively) or automatic tube compensation (peak inspiratory flow rate 0.75 +/- 0.26L s(-1); minute ventilation 10.8 +/- 2.7 L min(-1)). The pressure-time product as well as patients' work of breathing were comparable during automatic tube compensation (pressure-time product 214.5 +/- 104.6 cmH2O s(-1) min(-1), patient work of breathing 1.1 +/- 0.4 J L(-1)) and T-piece breathing (pressure-time product 208.3 +/- 121.6 cmH2O s(-1) min(-1), patient work of breathing 1.1 +/- 0.4 J L(-1)), whereas pressure support resulted in a significant decrease in workload indices (pressure-time product 121.2 +/- 64.1 cmH2O s(-1) min(-1), patient work of breathing 0.7 +/- 0.4 J L(-1)).

CONCLUSIONS

In weaning from mechanical lung ventilation, patients' work of breathing during spontaneous breathing trials is clearly reduced by the application of pressure support 7 cmH2O, whereas the workload during automatic tube compensation corresponded closely to the values during trials of breathing through a T-piece.

Anaesthetic agents in adult day case surgery

This study reports a review of all comparative published studies of adult day case anaesthesia in the English language up to December 2000. Ten databases were searched using appropriate keywords and data were extracted in a standardized fashion. One hundred-and-one published studies were examined. Recovery measurements were grouped as early, intermediate, late, psychomotor and adverse effects. With respect to induction of anaesthesia, propofol was superior to methohexital, etomidate and thiopental, but equal to sevoflurane and desflurane. Desflurane and sevoflurane were both superior to thiopental. There was no detectable difference between sevoflurane and isoflurane. With respect to the maintenance of anaesthesia, isoflurane and halothane were the worst. There were no significant differences between propofol, desflurane, sevoflurane and enflurane. Propofol is the induction agent of choice in day case patients. The use of a propofol infusion and avoidance of nitrous oxide may help to reduce postoperative nausea and vomiting.

Prediction of difficult tracheal intubation

BACKGROUND AND OBJECTIVE

Preoperative bedside screening tests for difficult tracheal intubation may be neither sensitive nor specific enough for clinical use. The aim was to investigate if a combination of the Mallampati classification of the oropharyngeal view with either the thyromental or sternomental distance measurement improved the predictive value.

METHODS

A total of 212 (109 male, 103 female) non-obstetric surgical patients, aged >18 yr, undergoing elective surgical procedures requiring tracheal intubation were assessed preoperatively with respect to the oropharyngeal (modified Mallampati) classification, thyromental and sternomental distances. An experienced anaesthetist, blinded to the preoperative airway assessment, performed laryngoscopy and graded the view according to Cormack and Lehane's classification.

RESULTS

Twenty tracheal intubations (9%) were difficult as defined by a Cormack and Lehane Grade 3 or 4, or the requirement for a bougie in patients with Cormack and Lehane Grade 2. Used alone, the Mallampati oropharyngeal view, and thyromental and sternomental distances were associated with poor sensitivity, specificity and positive predictive values. Combining the Mallampati Class III or IV with either a thyromental distance <6.5cm or a sternomental distance <12.5cm decreased the sensitivity (from 40 to 25 and 20%, respectively), but maintained a negative predictive value of 93%. The specificity and positive predictive values increased from 89 and 27% respectively for Mallampati alone to 100%.

CONCLUSIONS

The findings suggest that the Mallampati classification, in conjunction with measurement of the thyromental and sternomental distances, may be a useful routine screening test for preoperative prediction of difficult tracheal intubation.

Remifentanil versus alfentanil in total intravenous anaesthesia for day case surgery

BACKGROUND AND OBJECTIVE

We assessed the intraoperative haemodynamic responses and recovery profiles of total intravenous anaesthesia with remifentanil and alfentanil for outpatient surgery.

METHODS

Patients in Group 1 (n = 20) received alfentanil 20 microg kg(-1) followed by 2 microg kg(-1) min(-1) intravenously; patients in Group 2 (n = 20) received remifentanil 1 microg kg(-1) followed by 0.5 microg kg(-1) min(-1) intravenously. Both groups then received propofol 2 mg kg(-1) followed by 9 mg kg(-1) h(-1) intravenously. Five minutes after skin incision, infusion rates were decreased, and at the end of surgery, all infusions were discontinued. Early recovery was assessed by the Aldrete score, whereas intermediate recovery was assessed with the postanaesthetic discharge scoring system (PADS).

RESULTS

Perioperative arterial pressure was similar in both groups; heart rate was lower in Group 2 (P < 0.05). The times to spontaneous and adequate respiration, response to verbal commands, extubation and times for Aldrete score > or = 9 were shorter in Group 2 patients (P < 0.05). Pain scores were higher in Group 2 patients (P < 0.05). Overall times for postanaesthetic discharge scores > or = 9 were similar.

CONCLUSIONS

Early recovery of patients after day surgery is significantly shorter after total intravenous anaesthesia with remifentanil compared with that with alfentanil but postoperative pain management must be planned ahead.

Effects of different doses of oral ketamine for premedication of children

BACKGROUND AND OBJECTIVE

A need exists for a safe and effective oral preanaesthetic medication for use in children undergoing elective surgery. The study sought to define the dose of oral ketamine that would facilitate induction of anaesthesia without causing significant side-effects.

METHODS

We studied 80 children undergoing elective surgery under general anaesthesia who received oral ketamine 4, 6 or 8 mg kg(-1) in a prospective, randomized, double-blind placebo controlled study. We compared the reaction to separation from parents, transport to the operating room, the response to intravenous cannula insertion and application of an anaesthetic facemask, the induction of anaesthesia and recovery from anaesthesia.

RESULTS

In the group receiving ketamine 8 mg kg(-1), the children were significantly calmer than those of the other groups, and anaesthesia induction was more comfortable. Recovery from anaesthesia was longer in the group receiving ketamine 8 mg kg(-1) compared with the other groups, but no differences between the groups were observed after 2 h in the recovery room.

CONCLUSIONS

It is concluded that oral ketamine 8 mg kg(-1) is an effective oral premedication in inpatient children undergoing elective surgery.

Trendelenburg positioning after cardiac surgery: effects on intrathoracic blood volume index and cardiac performance

BACKGROUND AND OBJECTIVE

The efficacy of the Trendelenburg position, a common first step to treat suspected hypovolaemia, remains controversial. We evaluated its haemodynamic effects on cardiac preload and performance in patients after cardiac surgery.

METHODS

Twelve patients undergoing mechanical ventilation of the lungs who demonstrated left ventricular 'kissing papillary muscles' by transoesophageal echocardiography, thus suggesting hypovolaemia, were positioned 30 degrees head down for 15 min immediately after cardiac surgery. Cardiac output by thermodilution, central venous pressure, pulmonary artery occlusion pressure, left ventricular end-diastolic area by transoesophageal echocardiography and intrathoracic blood volume by thermo- and dye dilution were determined before, during and after this Trendelenburg manoeuvre.

RESULTS

Trendelenburg's manoeuvre was associated with increases in central venous pressure (9 +/- 2 to 12 +/- 3 mmHg) and pulmonary artery occlusion pressure (8 +/- 2 to 11 +/- 3 mmHg). The intrathoracic blood volume index increased slightly (dye dilution from 836 +/- 129 to 872 +/- 112 mL m(-2); thermodilution from 823 +/- 129 to 850 +/- 131 mL m(-2)) as did the left ventricular end-diastolic area index (7.5 +/- 2.1 to 8.1 +/- 1.7 cm2 m(-2)), whereas mean arterial pressure and the cardiac index did not change significantly. After supine repositioning, the cardiac index decreased significantly below baseline (3.0 +/- 0.6 versus 3.5 +/- 0.8 L min(-1) m(-2)) as did mean arterial pressure (76 +/- 12 versus 85 +/- 11 mmHg), central venous pressure (8 +/- 2 mmHg) and pulmonary artery occlusion pressure (6 +/- 4 mmHg). The intrathoracic blood volume index and left ventricular end-diastolic area index did not differ significantly from baseline.

CONCLUSIONS

Trendelenburg's manoeuvre caused only a slight increase of preload volume, despite marked increases in cardiac-filling pressures, without significantly improving cardiac performance.

Anaesthetic and haemodynamic effects of continuous spinal versus continuous epidural anaesthesia with prilocaine

BACKGROUND AND OBJECTIVE

To compare, using prilocaine, the effects of continuous spinal anaesthesia (CSA) and continuous epidural anaesthesia (CEA) on haemodynamic stability as well as the quality of anaesthesia and recovery in patients undergoing transurethral resection of the prostate gland.

METHODS

Thirty patients (>60 yr) were randomized into two groups. Prilocaine, 2% 40 mg, was given to patients in the CSA group, and prilocaine 1% 150mg was given to patients in the CEA group. Incremental doses were given if the level of sensory block was lower than T10 or if needed during surgery.

RESULTS

There was a significant decrease in mean arterial pressure in Group CEA compared with Group CSA (P < 0.01). The decrease in heart rate in Group CSA occurred 10 min after the first local anaesthetic administration and continued through the operation (P < 0.05). The level of sensory anaesthesia was similar in both groups. The times to reach the level of T10 and the upper level of sensory blockade (Tmax) were 18.0 +/- 4.7 and 25.3 +/- 7.0 min in Groups CSA and CEA, respectively, and were significantly longer in Group CEA. The duration of anaesthesia was 76.8 +/- 4min and was shorter in Group CSA (P < 0.01).

CONCLUSIONS

Spinal or epidural anaesthesia administered continuously was reliable in elderly patients undergoing transurethral resection of the prostate. Continuous spinal anaesthesia had a more rapid onset of action, produced more effective sensory and motor blockade and had a shorter recovery period. Prilocaine appeared to be a safe local anaesthetic for use with either continuous spinal anaesthesia or continuous epidural anaesthesia.

Cortical activity assessed by Narcotrend in relation to haemodynamic responses to tracheal intubation at different stages of cortical suppression and reflex control

BACKGROUND AND OBJECTIVE

Many anaesthesiologists still interpret haemodynamic responses as signs of insufficient cortical suppression. The aim was to illustrate how haemodynamics may only poorly reflect the level of cortical suppression and that electroencephalographic monitoring could indicate different relationships between cortical effects and haemodynamics.

METHODS

Anaesthesia was induced with thiopental (7 mg kg(-1)), and fentanyl (2 microg kg(-1)) with succinylcholine (1.5 mg kg(-1)) for neuromuscular blockade in the 11 patients of Group 1. In Group 2 (n = 15), thiopental (7 mg kg(-1)) and succinylcholine (1.5 mg kg(-1)) were given. In Group 3, the patients (n = 13) received thiopental (7 mg kg(-1)), fentanyl (2 microg kg(-1)) and cisatracurium (0.1 mg kg(-1)), and they were intubated 3 min later than the patients in Groups 1 and 2. We determined conventional electroencephalographic (EEG) variables and classified 14 EEG stages in real-time ranging from A (= 1), indicating full wakefulness, to F1 (= 14), at profound cortical suppression.

RESULTS

All groups had profound cortical suppression 45 s after thiopental administration, which rapidly decreased (EEG stage, 11 (6-13) versus 7 (2-13) at 4 min, P < 0.0001). Decreasing EEG stages were associated with increasing SEF 95, relative alpha and beta power and decreasing relative delta power. During tracheal intubation, profound cortical suppression remained unchanged in Groups 1 and 2. In Group 3, cortical suppression had decreased before laryngoscopy (P < 0.005). In Group 2, 11 patients had heart rate responses to tracheal intubation, whereas only two responded in Group 1 (P = 0.015) and three in Group 3 (P = 0.02). Thirteen patients in Group 2 had arterial pressure responses, and five in Group 1 (P = 0.038). Circulatory responses did not differ between Groups 1 and 3.

CONCLUSIONS

Electroencephalographic monitoring was suitable to indicate in real-time that haemodynamics only poorly reflect rapidly changing levels of cortical suppression, and how haemodynamics and cortical activity depend on the applied combination of hypnotic and analgesic drugs during anaesthesia induction with thiopental.

Increasing the injection volume by dilution improves the onset of motor blockade, but not sensory blockade of ropivacaine for brachial plexus block

BACKGROUND AND OBJECTIVE

Ropivacaine used for axillary plexus block provides effective motor and sensory blockade. Varying clinical dosage recommendations exist. Increasing the dosage by increasing the concentration showed no improvement in onset. We compared the behaviour of a constant dose of ropivacaine 150 mg diluted in a 30, 40 or 60 mL injection volume for axillary (brachial) plexus block.

METHODS

A prospective, randomized, observer-blinded study on patients undergoing elective hand surgery was conducted in a community hospital. Three groups of patients with a constant dose of ropivacaine 150 mg, diluted in 30,40 or 60 mL NaCl 0.9%, for axillary plexus blockade were compared for onset times of motor and sensory block onset by assessing muscle strength, two-point discrimination and constant-touch sensation.

RESULTS

Increasing the injection volume of ropivacaine 150 mg to 60 mL led to a faster onset of motor block, but not of sensory block, in axillary plexus block, compared with 30 or 40 mL volumes of injection.

CONCLUSIONS

The data show that the onset of motor, but not of sensory block, is accelerated by increasing the injection volume to 60 mL using ropivacaine 150 mg for axillary plexus block. This may be useful for a more rapid determination of whether the brachial plexus block is effective. However, when performing surgery in the area of the block, sensory block onset seems more important.

Temperature control and recovery of bowel function after laparoscopic or laparotomic colorectal surgery in patients receiving combined epidural/general anesthesia and postoperative epidural analgesia

We compared the effects of a laparoscopic (n = 23) versus laparotomic (n = 21) technique for major abdominal surgery on temperature control in 44 patients undergoing colorectal surgery during a combined epidural/general anesthesia. A thoracic epidural block up to T4 was induced with 6-10 mL of 0.75% ropivacaine; general anesthesia was induced with thiopental, fentanyl, and atracurium IV and maintained with isoflurane. Core temperature was measured with a bladder probe and recorded every 15 min after the induction. In both groups, core temperature decreased to 35.2 degrees C (range, 34 degrees C-36 degrees C) at the end of surgery. After surgery, normothermia returned after 75 min (60-120 min) in the Laparoscopy group and 60 min (45-180 min) in the Laparotomy group (P = 0.56). No differences in postanesthesia care unit discharge time were reported between the two groups. The degree of pain during coughing was smaller after laparoscopy than laparotomy from the 24th to the 72nd observation times (P < 0.01). Morphine consumption was 22 mg (2-65 mg) in the Laparotomy group and 5 mg (0-45 mg) in the Laparoscopy group (P = 0.02). The time to first flatus was shorter after laparoscopy (24 h [16-72 h]) than laparotomy (72 h [26-96 h]) (P = 0.0005), and the first intake of clear liquid occurred after 48 h (24-72 h) in the Laparoscopy group and after 96 h (90-96 h) in the Laparotomy group (P = 0.0005). Although laparoscopic surgery provides positive effects on the degree of postoperative pain and recovery of bowel function, the reduction in heat loss produced by minimizing bowel exposure with laparoscopic surgery does not compensate for the anesthesia-related effects on temperature control, and active patient warming must also be used with laparoscopic techniques.

IMPLICATIONS

This prospective, randomized, controlled study demonstrates that laparoscopic colorectal surgery results in less postoperative pain and earlier recovery of bowel function than conventional laparotomy but does not reduce the risk for perioperative hypothermia. Accordingly, active warming must be provided to patients also during laparoscopic procedures.

The impact of morbid obesity, pneumoperitoneum, and posture on respiratory system mechanics and oxygenation during laparoscopy

We studied the effect of morbid obesity, 20 mm Hg pneumoperitoneum, and body posture (30 degrees head down and 30 degrees head up) on respiratory system mechanics, oxygenation, and ventilation during laparoscopy. We hypothesized that insufflation of the abdomen with CO(2) during laparoscopy would produce more impairment of respiratory system mechanics and gas exchange in the morbidly obese than in patients of normal weight. The static respiratory system compliance and inspiratory resistance were computed by using a Servo Screen pulmonary monitor. A continuous blood gas monitor was used to monitor real-time PaCO(2) and PaO(2), and the ETCO(2) was recorded by mass spectrometry. Static compliance was 30% lower and inspiratory resistance 68% higher in morbidly obese supine anesthetized patients compared with normal-weight patients. Whereas body posture (head down and head up) did not induce additional large alterations in respiratory mechanics, pneumoperitoneum caused a significant decrease in static respiratory system compliance and an increase in inspiratory resistance. These changes in the mechanics of breathing were not associated with changes in the alveolar-to-arterial oxygen tension difference, which was larger in morbidly obese patients. Before pneumoperitoneum, morbidly obese patients had a larger ventilatory requirement than the normal-weight patients to maintain normocapnia (6.3 +/- 1.4 L/min versus 5.4 +/- 1.9 L/min, respectively; P = 0.02). During pneumoperitoneum, morbidly obese, supine, anesthetized patients had less efficient ventilation: a 100-mL increase of tidal volume reduced PaCO(2) on average by 5.3 mm Hg in normal-weight patients and by 3.6 mm Hg in morbidly obese patients (P = 0.02). In conclusion, respiratory mechanics during laparoscopy are affected by obesity and pneumoperitoneum but vary little with body position. The PaO(2) was adversely affected only by increased body weight.

IMPLICATIONS

Morbid obesity significantly decreases respiratory system compliance and increases inspiratory resistance. Increased body weight, and not altered mechanics of breathing, was associated with worse PaO(2) during laparoscopy.

Randomized comparison of isoflurane and sevoflurane for laparoscopic gastric banding in morbidly obese patients

STUDY OBJECTIVE

To compare the efficacy and recovery profile of sevoflurane and isoflurane as the main anesthetics for morbidly obese patients.

DESIGN

Randomized, blinded study.

SETTING

Inpatients.

PATIENTS

30 ASA physical status II and III obese patients [body mass index (BMI) > 35 kg/m(2)] undergoing laparoscopic gastric banding for morbid obesity.

INTERVENTIONS

After standard intravenous induction of general anesthesia and tracheal intubation, anesthesia was maintained with either sevoflurane or isoflurane as the main anesthetics. The end-tidal concentrations of the volatile drugs were adjusted to maintain systolic arterial blood pressure within +/-20% from baseline values. When the surgeon started the skin suture, the end-tidal concentration of the inhalational drug was reduced to 0.5 minimum alveolar concentration in both groups. At the last skin suture, the inhalational drug was discontinued and the vaporizator was removed to allow blinded evaluation of the emergence times.

MEASUREMENTS AND MAIN RESULTS

No differences in anesthetic exposure, hemodynamic parameters, incidence of untoward events, or postoperative pain relief were reported between the two groups. Extubation, emergence, and response times were shorter after sevoflurane [6 min (3-15 min), 8 min (5-18 min), and 12 (6-25 min)] than isoflurane [10 min (6-26 min), 14 min (6-21 min), and 21 min (14-41 min)] (p = 0.001, p = 0.03, and p = 0.0005, respectively). The median time for postanesthesia care unit discharge was 15 minutes (25th-75th percentiles: 10-18 min) after sevoflurane and 27 minutes (25th-75th percentiles: 20-30 min) after isoflurane (p = 0.0005).

CONCLUSIONS

Sevoflurane provides a safe and effective intraoperative control of cardiovascular homeostasis in morbidly obese patients undergoing laparoscopic gastric banding, with the advantage of a faster recovery and earlier discharge from the postanesthesia care unit than isoflurane.