R. A. De Blasi

Combined intrathecal and epidural magnesium sulfate supplementation of spinal anesthesia to reduce post-operative analgesic requirements : a prospective, randomized, double-blind, controlled trial in patients undergoing major orthopedic surgery

Background:  New ways of decreasing post‐operative analgesic drug requirements are of special interest after major surgery. Magnesium sulfate (MgSO4) alters pain processing and reduces the induction and maintenance of central sensitization by blocking the N‐methyl‐d‐aspartate (NMDA) receptor in the spinal cord. We investigated whether supplementation of spinal anesthesia with combined intrathecally and epidurally infused MgSO4 reduced patients’ post‐operative analgesia requirements.

Control of post anaesthetic shivering with nefopam hydrochloride in mildly hypothermic patients after neurosurgery

Postoperative shivering may be prevented by maintaining normothermia intraoperatively or it may be treated using specific drugs.

Propofol induces bronchodilation in mechanically ventilated chronic obstructive pulmonary disease (COPD) patients

The aim of this study was to evaluate the effects of propofol administration (2 mg · kg‐1 i.v.) on the airways resistances and respiratory mechanics of patients affected by COPD exacerbation, requiring mechanical ventilation. Twenty patients required anaesthesia for diagnostic or therapeutic procedures. Fourteen consecutive patients were divided at random into two groups: Group P received propofol and Group C (control) received only Intralipid 10%; an additional group of six patients received i.v. flunitrazepam (0.03 mg · kg‐1). Lung mechanics (dynamic and static compliance, peak inspiratory pressure, intrinsic positive and expiratory pressure, minimal and maximal resistances of the respiratory system) were evaluated in basal conditions and 3 and 6 min after propofol, Intralipid or flunitrazepam administration. We did not observe significant variations of the evaluated variables after Intralipid or flunitrazepam (Groups C and F), while in patients who received propofol (Group P), we observed the following modifications: dynamic compliance increased from 2.3 ± 0.3 to 2.8 ± 0.4 ml · kPa‐1 (P<0.05), peak inspiratory pressure decreased from 3.3 ± 0.7 to 2.8 ± 0.4 kPa (P <0.05), minimal resistances of the respiratory system (that mainly reflect airways resistances) decreased from 1 ± 0.2 to 0.7 ± 0.2 kPa · 1‐1 · s‐1 (P <0.01). Our results suggest that propofol induces bronchodilation in mechanically ventilated COPD patients, and that this effect is not related specifically to the induction of general anesthesia.

Cerebral and muscle oxygen saturation measurement by frequency-domain near-infra-red spectrometer

Tissue oxygen saturation quantification was obtained using a frequency-domain multi-source method based on two wavelength light-emitting diodes. Brain saturation was 60·3±1·1% (n=12). Brachioradial muscle saturation declined during forearm ischaemia and maximal voluntary contraction from 73·7±1·8 and 74·7±1·8% at rest to 44·2±3·3 and 61·4±2·9%, respectively.

Effects of the heat-moisture exchangers on dynamic hyperinflation of mechanically ventilated COPD patients

In recent years the use of devices called Heat and Moisture Exchangers (HME) has become widespread as gas conditioners for ICU patients requiring mechanical ventilation. As an important variation of the resistive properties of the HME, related to flow and duration of use, has recently been pointed out during “in vitro” studies, the use of these devices in COPD patients could increase the levels of auto PEEP and dynamic hyperinflation. In this study we have compared the levels of auto PEEP and difference in functional residual capacity (Δ FRC) in a group of COPD patients, requiring controlled mechanical ventilation (CMV), at basal conditions and after the insertion into the circuit of three HMEs (Dar Hygrobac, Pall Ultipor, Engstrom Edith) at random: the results obtained excluded a significant increase of auto PEEP and Δ (FRC) both with “new” HMEs and after 12 h of continuous use.

Detection of leukotrienes B4, C4 and of their isomers in arterial, mixed venous blood and bronchoalveolar lavage fluid from ARDS patients

Seven patients with the adult respiratory distress syndrome (ARDS) were studied. As a control group we used 6 surgical patients who underwent minor surgical operation (inguinal hernia). For both groups the same sample collection and analysis was used. The presence of leuktorienes (LTs) B4 and C4 and of their isomers 11-trans LTC4 and Δ6-trans-12-epi LTB4 was determined in arterial, mixed venous blood and in bronchoalveolar lavage (BAL) fluid. The samples, analysed by reverse phase high performance liquid chromatography (RP-HPLC), showed a similar chromatographic picture among ARDS patients, while the control group showed no detectable amounts of LTs in BAL or blood. The distribution of these arachidonic acid metabolites in mixed venous blood, arterial blood and BAL seems to suggest pulmonary metabolism and/or inactivation. It is suggested that these mediators act as humoral factors in pathogenesis of the ARDS.

Evaluation of respiratory system resistance in mechanically ventilated patients: The role of the endotracheal tube

ObjectiveTo investigate the role played by the endotracheal tube (ETT) in the correct evaluation of respiratory system mechanics with the end inflation occlusion method during constant flow controlled mechanical ventilation.SettingGeneral ICU, university of Rome “La Sapienza”.Patients12 consecutive patients undergoing controlled mechanical ventilation.MethodsWe compared the values of minimal resistance of the respiratory system (i.e. airway resistance) (RRS min) obtained: i) subtracting the theoretical value of ETT resistance from the difference between P max and P1, measured on airway pressure tracings obtained from the distal end of the ETT; ii) directly measuring airway pressure 2 cm below the ETT, thus automatically excluding ETT resistance from the data.ResultsThe values of RRS min obtained by measuring airway pressure below the ETT were significantly lower than those obtained by measuring airway pressure at the distal end of the ETT and subtracting the theoretical ETT resistance (4.5±2.8 versus 2.5±1.6 cm H2O/l/s,p<0.01).ConclusionWhen precise measurements of ohmic resistances are required in mechanically ventilated patients, the measurements must be obtained from airways pressure data obtained at tracheal level. The “in vivo” positioning of ETT significantly increases the airflow resistance of the ETT.

Effects of remifentanil-based general anaesthesia with propofol or sevoflurane on muscle microcirculation as assessed by near-infrared spectroscopy

BACKGROUND Although anaesthetics are known to alter microcirculation no study has, to our knowledge, documented changes in human skeletal microcirculatory function during general anaesthesia. METHODS Forty-four patients undergoing maxillofacial surgery at a university hospital were prospectively randomized to receive general anaesthesia with remifentanil combined with propofol or sevoflurane. Muscle microcirculation was investigated with near-infrared spectroscopy (NIRS) before general anaesthesia was induced and 30 min later. An NIRS device (NIMO, Nirox) was used to quantify calf deoxyhaemoglobin [HHb], oxyhaemoglobin [HbO2], and total haemoglobin [HbT] concentrations, coupled to a series of venous and arterial occlusions to measure calf blood flow, muscle oxygen consumption, calf vascular resistance, microvascular compliance, and haemoglobin resaturation rate (RR). RESULTS In both the groups, general anaesthesia induced marked changes in muscle microcirculation: the tissue blood volume increased (+33% in remifentanil-sevoflurane and +45% with remifentanil-propofol groups), microvascular resistance decreased (-31% and -38%, respectively), and the post-ischaemic haemoglobin RR decreased (-48% and -36%, respectively). In the remifentanil-propofol group, the muscle blood flow increased (P<0.001), whereas in the remifentanil-sevoflurane group microvascular compliance and muscle oxygen consumption decreased (P<0.01). CONCLUSIONS Remifentanil-based general anaesthesia with propofol or sevoflurane altered the muscle microcirculation in different ways. Quantitative NIRS, a technique that takes into account the optical tissue properties of the individual subject, can effectively measure these changes non-invasively.

Lateral popliteal sciatic nerve block: a single injection targeting the tibial branch of the sciatic nerve is as effective as a double-injection technique

Background:  Evidence indicating that single‐ and double‐injection techniques for inducing a sciatic nerve block via a posterior subgluteal approach yield a similar success rate prompted us to investigate whether the two anesthetic techniques yield a similar success rate via a lateral approach. We also hypothesized that, owing to the peculiar anatomic features of the sciatic nerve at the popliteal level, a single injection via the lateral approach might induce effective anesthesia by targeting the tibial nerve only.

A new device to remove obstruction from endotracheal tubes during mechanical ventilation in critically ill patients

ObjectiveTo evaluate the efficiency of a new device developed to remove obstructions from endotracheal tubes (ETT) in mechanically ventilated patients.DesignOpen study in mechanically ventilated sedated and paralyzed ICU patients.SettingGeneral ICU and Laboratory of Respiratory Mechanics of the University of Rome “La Sapienza”.Patients8 consecutive unselected mechanically ventilated, critically ill patients in which a partial obstruction of ETT was suspected on the basis of an increase of the peak inspiratory pressure (>20%) plus the difficult introduction of a standard suction catheter.InterventionsObstructions to ETT were removed with an experimental “obstruction remover” (OR)Measurements“In vivo” ETT airflow resistance (0.25; 0.5; 0.75; 1l/s) was evaluated before and after use of the OR; the work of breathing necessary to overcome ETT resistance (WOBett) was also evaluated before and after OR use.ResultsThe use of OR significantly reduced in all patients the ETT “in vivo” resistance (From 5.5±2.3 to 2.9±0.5 cmH2O/l/s at 0.25l/s,p<0.05; from 9±2.4 to 3.8±0.8 cmH2O/l/s at 0.51l/s; from 12.2±3.5 to 5.7±1.2 cmH2O/l/s at 0.75l/s; from 16.9±6 to 9.3±3.8 cmH2O/l/s at 1l/s,p<0.01 respectively). Also the WOBett was significantly reduced after use of the OR (from 0.66±0.19 to 0.34±0.08 J/l;p<0.05)ConclusionThis experimental device can be safely and successfully used to remove obstructions from the ETT lumen, without suspending mechanical ventilation, reducing the need for rapid ETT substitution in emergency and life-threatening situations.