Closed-loop administration of analgesic drugs based on heart rate variability analysis.

General anesthesia is based on the use of hypnotic, muscle relaxant and analgesic drugs in order to render the patient unresponsive to the surgical procedure. The difficulty for anesthesiologists is then to determinate the minimum efficient dose to avoid any risk of under or over dosing. For several years, monitoring systems were developed in order to measure depth of hypnosis, myorelaxation and analgesia. As soon as all these monitoring systems became available, several teams worked on the closed-loop administration of anesthetic agents. We have developed a closed-loop system allowing the automatic administration of analgesic drugs. This system is based on the analysis of a heart rate variability based index: the ANI (Analgesia Nociception Index). In this paper, we describe this device and demonstrate its efficiency, repeatability and safety in a simulation environment.

Ambulatory pain evaluation based on heart rate variability analysis: Application to physical therapy.

Pain assessment is critical for efficient pain management. Clinicians usually use self-report or behavioral pain scales. In practice, the choice of the most adaptive scale depends on several parameters like the clinical context, the patient consciousness or its age, but all evaluation scales are known to be more or less subjective and to present high inter and intra individual variability. Recently, several innovative medical devices have been developed in order to provide to the clinicians a physiological measure of pain. These technologies are mainly used for the continuous monitoring of patients in intensive care or during surgery. As an example, we have developed a heart rate variability analysis based technology for analgesia/nociception monitoring in patients undergoing surgery under general anesthesia. Even if this technology is now used in other clinical settings, the resulting device presents some mobility constraints. In this paper, we describe the adaptation of this technology to the ambulatory pain evaluation and its clinical validation in the particular context of physical therapy. In the frame of this validation, we showed the device usability and efficiency for pain evaluation during physical therapy sessions.

Automated analgesic drugs delivery guided by vagal tone evaluation: interest of the Analgesia Nociception Index (ANI).

Analgesic drugs delivery optimization constitutes one of the main objectives of modern anesthesia. Indeed, their over or under determination constitutes a risk for anesthetized patient in terms of hemodynamic reactivity or post-operative hyperalgesia. Nowadays, new physiological indexes allow anesthesiologists to evaluate the balance between the analgesia level and the noxious stimulus importance. ANI is an index related to the autonomic nervous system activity based on heart rate variability analysis. Its ability for the analgesia / nociception balance evaluation has been established bringing evidences about its helpfulness for analgesic drug delivery. In this article, we describe a device for automatic analgesic drugs administration based on the ANI evolution during surgical procedures under general anesthesia. We hypothesized that such a device could improve the quality and safety of anesthesia by reducing adverse cardiovascular events and delivered analgesic drugs doses.

Heart rate variability analysis for arterial hypertension etiological diagnosis during surgical procedures under tourniquet.

Pneumatic tourniquets are widely used to provide a bloodless operative field during upper or lower limb surgery. If tourniquet inflation during general anesthesia is initially a mild stimulus, a long duration of inflation can imply heart rate and blood pressure increasing. However, heart rate or blood pressure increasing can also be caused by other external stimuli. Indeed, in the case of an insufficient analgesia, painful surgical stimuli can also cause an increase in heart rate and blood pressure. Therefore, in the case of the use of a tourniquet during surgery, it's very difficult for the anesthesiologist to distinguish hypertension caused by pain from hypertension caused by tourniquet inflation. In such a case, an efficient and reliable hypertension diagnosis could help the anesthesiologist in the medication choice. We have previously developed and evaluated an Analgesia / Nociception Index (ANI) based on the magnitude analysis of the respiratory patterns on the RR series. We hypothesize that the use of such an index could help in the arterial hypertension etiological diagnosis during surgical procedures under tourniquet.

PhysioDoloris: a monitoring device for analgesia / nociception balance evaluation using heart rate variability analysis.

Continuous Analgesia / Nociception balance evaluation during general anesthesia could be of precious help for the optimization of analgesic drugs delivery, limiting the risk of toxicity due to the use of opioid drugs, limiting the risk of post operative hyper algesia, and, probably, reducing time of recovery after surgical procedure. Heart Rate Variability analysis has been shown in several studies to measure the Autonomic Nervous System tone, which is strongly influenced by anesthetic drugs. Recording RR series during general anesthesia enabled us to observe that the Respiratory Sinus Arrhythmia pattern changed when a surgical stimulation was painful, even though the patient was not conscious. We have previously developed and evaluated a pain / analgesia measurement algorithm based on the magnitude analysis of the respiratory patterns on the RR series. In this paper, we present the development of a monitoring device (PhysioDoloris), based on the previously described technology, giving in real time an Analgesia Nociception Index (ANI) which can be used during general anesthesia in order to give to the anesthetist, a complementary tool for optimized drug delivery.

[Management of venous thromboembolic disease in ambulatory and hospital settings: an assessment of general practices in France]. / Prise en charge hospitalière et ambulatoire de la maladie veineuse thromboembolique en France: un état des lieux.

OBJECTIVE: In spite of increasing use of prophylactic treatments, venous thromboembolic disease (VTD) remains an important public health problem because of its high morbidity and mortality, in particular after major orthopedic surgery. The aim of this study is to provide an assessment of current medical management of VTD and post-thrombotic disease (PTD) in France. METHOD: A random sample of 210 investigators including hospital practitioners (orthopedic surgeons and anesthesiologists), general practitioners (GP), and angiologists working in the ambulatory setting completed a standardized questionnaire about their current medical practice. RESULTS: VTD led to an additional 8.5 days of hospital stay needed for the management of deep vein thrombosis (DVT) and 15.8 days in the event of pulmonary embolism (PE). Doppler diagnosis of DVT was obtained in 97% to 100% of patients. When PE was suspected, a lung scan was performed in 62% of patients managed by hospital practitioners and in 43% of patients treated by GPs. Whereas the rate of hospitalization for distal DVT diagnosed in outpatients did not exceed 14% of patients, the rate of hospitalization for proximal DVT reached 40%-48%. Eighty-eight percent of the patients with PE were managed in a hospital setting. Two-thirds of the patients with PE were given low-molecular-weight heparin for an average duration of 9.3 days and one-third of patients were treated with non-fractioned heparin for an average duration of a 11 days. Doppler diagnosis of PTD was established in 98% of patients and 98% of the patients with PTD were treated with elastic contention stockings. CONCLUSION: Based on physicians' report of their current medical practice, this study provides useful data on diagnostic and therapeutic practices in the management of VTD and PTD.

[Pneumocephalus after spinal anesthesia]. / Pneumencéphalie après rachianesthésie.

We report the case of a 76-year-old man who received a spinal anaesthesia for inguinal hernia repair surgery. A cranial CT scan which was performed because the patient complained of postoperative headache and hemiparesis showed an important pneumocephalus. Because postoperative questioning revealed that the patient had a chronic and neglected rhinorrhea, we hypothesise that this pneumocephalus was secondary to an old unknown osteodural leak with intracranial air entry secondary to the spinal anaesthesia-releated decrease in CSF pressure.

An attempt to prevent spread of local anaesthetic to the phrenic nerve by compression above the injection site during the interscalene brachial plexus block.

The brachial plexus was identified by electrical stimulation before interscalene block with 30 mL 0.5% bupivacaine and adrenaline 1:200,000. During injection, compression was applied with a finger proximal to the injection site. Spirometric measurements were made before the block, and then at 5 min, 10 min, 20 min and 4 h after the injection. Diaphragmatic excursion was measured radiographically before the block, and at 15 min and 4 h afterwards. In 25 patients studied, spirometric measurements decreased. Twenty minutes after the injection, the forced vital capacity was 27% less, forced expiratory volume at 1 s 34% less and peak expiratory flow rate 15% less (all P < 0.05). Right diaphragmatic excursion decreased from 4.5 cm (SD 1.2 cm) to 1.8 cm (0.6 cm) at 15 mins and to 1.1 cm (0.6 cm) at 4 h (P < 0.05). Identification of the plexus by electric stimulation combined with finger compression above the injection site did not prevent diaphragmatic paresis.

[Subarachnoid hematoma after spinal anesthesia and low molecular weight heparin]. / Hématome sous-arachnoïdien après rachianesthésie et héparine de bas poids moléculaire.

A case is reported of spinal subarachnoid haematoma occurring after spinal anaesthesia. The patient was given prophylactic pre and postoperative low molecular weight heparin. On the second postoperative day, he complained of backache and got a partial cauda equina syndrome. Magnetic resonance imaging carried out on the 6th day confirmed the presence of a spinal haematoma, which was removed surgically. One year later, the bilateral motor palsy which had involved several roots, had completely regressed. It remained a severe sensory loss associated with a loss of sphincter control. This case highlights the role of predisposing factors and the importance of early diagnosis.