Capnogram slope and ventilation dead space parameters: comparison of mainstream and sidestream techniques.

BACKGROUND: Capnography may provide useful non-invasive bedside information concerning heterogeneity in lung ventilation, ventilation-perfusion mismatching and metabolic status. Although the capnogram may be recorded by mainstream and sidestream techniques, the capnogram indices furnished by these approaches have not previously been compared systematically. METHODS: Simultaneous mainstream and sidestream time and volumetric capnography was performed in anaesthetized, mechanically ventilated patients undergoing elective heart surgery. Time capnography was used to assess the phase II (SII,T) and III slopes (SIII,T). The volumetric method was applied to estimate phase II (SII,V) and III slopes (SIII,V), together with the dead space values according to the Fowler (VDF), Bohr (VDB), and Enghoff (VDE) methods and the volume of CO2 eliminated per breath ([Formula: see text]). The partial pressure of end-tidal CO2 ([Formula: see text]) was registered. RESULTS: Excellent correlation and good agreement were observed in SIII,T measured by the mainstream and sidestream techniques [ratio=1.05 (sem 0.16), R(2)=0.92, P<0.0001]. Although the sidestream technique significantly underestimated [Formula: see text] and overestimated SIII,V [1.32 (0.28), R(2)=0.93, P<0.0001], VDF, VDB, and VDE, the agreement between the mainstream and sidestream techniques in the difference between VDE and VDB, reflecting the intrapulmonary shunt, was excellent [0.97 (0.004), R(2)=0.92, P<0.0001]. The [Formula: see text] exhibited good correlation and mild differences between the mainstream and sidestream approaches [0.025 (0.005) kPa]. CONCLUSIONS: Sidestream capnography provides adequate quantitative bedside information about uneven alveolar emptying and ventilation-perfusion mismatching, because it allows reliable assessments of the phase III slope, [Formula: see text] and intrapulmonary shunt. Reliable measurement of volumetric parameters (phase II slope, dead spaces, and eliminated CO2 volumes) requires the application of a mainstream device.

Comparison of sedation and general anaesthesia for transcatheter aortic valve implantation on cerebral oxygen saturation and neurocognitive outcome†.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is a treatment strategy for patients with severe aortic stenosis. Although general anaesthesia (TAVI-GA) and sedation (TAVI-S) have previously been described for TAVI, the difference in safety and efficacy of both methods has not been studied in a randomized trial. METHODS: The INSERT trial was a single centre, controlled parallel-group trial with balanced randomization. Sixty-six patients (68-94 yr) with acquired aortic stenosis undergoing transfemoral CoreValve™ were assigned to TAVI-GA or TAVI-S. Comparable operative risk was determined from risk-scores (EUROscore, STS-Score). Monitoring and anaesthetic drugs were standardized. Near-Infrared-Spectroscopy was used to monitor cerebral-oxymetry blinded. Primary outcome was the perioperative cumulative cerebral desaturation. As secondary outcomes, changes in neurocognitive function and respiratory and haemodynamic adverse events were evaluated. RESULTS: Of 66 included patients, 62 (TAVI-GA: n=31, TAVI-S: n=31) were finally analysed. Baseline characteristics were comparable. In 24 patients (39%) cerebral desaturation was observed. Cumulative cerebral desaturation was comparable (TAVI-GA:(median [IQR]) (0[0/1308] s%) vs. TAVI-S:(0[0/276] s%); P=0.505) between the groups. Neurocognitive function did not change within and between groups. Adverse events were more frequently observed in TAVI-S patients (P<0.001). Bradypnoea (n=16, 52%) and the need for airway manoeuvres (n=11, 36%) or bag-mask-ventilation (n=6, 19%) were the most common respiratory adverse events. CONCLUSIONS: Cerebral desaturation occurred in both patient groups, but there was no significant difference between the two groups. Based on primary outcome, both methods were shown to be comparable. Neurocognitive outcome was similar. The higher incidence of adverse events in the sedation group suggests a potential advantage of general anaesthesia. CLINICAL TRIAL REGISTRATION: NCT 01251328.

Evaluation of post-surgical cognitive function and protein fingerprints in the cerebro-spinal fluid utilizing surface-enhanced laser Desorption/Ionization time-of-flight mass-spectrometry (SELDI-TOF MS) after coronary artery bypass grafting: review of proteomic analytic tools and introducing a new syndrome.

Cognitive dysfunction following surgery is a common complication, which increases the incidence of other co-morbid conditions, hospital and health-care costs. The reported rate of the occurrence of post-operative cognitive decline varies with different studies, depending on population profile, type of surgery, definition of cognitive disorder and detection methods, design of study, etc. It remains unclear whether these psychiatric signs and symptoms are direct results of the effects of surgery or general anesthesia. Nonetheless they are more frequent after cardiac surgery and are likely to be multi-factorial, but the patho-mechanisms are not yet fully characterized. This communication provides a synopsis of proteomics tools and delineates novel SELDI-TOF results to evaluate biomarkers in this regard. Presented for the first time is a classification of the clinically relevant forms of post-operative cognitive decline with the advent of a novel subclass.

Crackle-sound recording to monitor airway closure and recruitment in ventilated pigs.

It was hypothesised that the recruitment of atelectatic lung areas is signified by changes in the airway and tissue mechanics, and by the appearance of crackle activity attributed to the sudden reopening of collapsed airways. The authors also assumed that the acoustic activity is an earlier indicator of lung recruitment than the change in the overall mechanical state of the lungs. Six thoracotomised and mechanically ventilated mini-pigs were studied. Low-frequency pulmonary impedance was measured at end-expiratory pauses at transpulmonary pressures of 4 and 1 hPa to estimate airway resistance (Raw) and the coefficient of lung tissue elastance (H), and tracheal sounds were recorded during subsequent slow inflations to 30 hPa, in the control state and following increasing doses of i.v. methacholine (Mch). Raw and H were higher at baseline and increased more in response to Mch at 1 hPa than at 4 hPa. The crackles detected during the subsequent inflations were concentrated around and associated with the development of the lower knee of the pressure-volume curve. The number of crackles increased faster following the Mch doses and reached statistical significance earlier than Raw and H. Crackle recording during mechanical ventilation can be employed as a simple method with which to monitor lung recruitment-derecruitment.

Components of respiratory resistance monitored in mechanically ventilated patients.

The interrupter technique is commonly adopted to monitor respiratory resistance (Rrs,int) during mechanical ventilation; however, Rrs,int is often interpreted as an index of airway resistance (Raw). This study compared the values of Rrs,int provided by a Siemens 940 Lung Mechanics Monitor with total respiratory impedance (Zrs) parameters in 39 patients with normal spirometric parameters, who were undergoing elective coronary bypass surgery. Zrs was determined at the airway opening with pseudorandom oscillations of 0.2-6 Hz at end inspiration. Raw and tissue resistance (Rti) were derived from the Zrs data by model fitting; Rti and total resistance (Rrs,osc=Raw+Rti) were calculated at the actual respirator frequencies. Lower airway resistance (Rawl) was estimated by measuring tracheal pressure. Although good agreement was obtained between Rrs,osc and Rrs,int, with a ratio of 1.07+/-0.19 (mean+/-SD), they correlated poorly (r2=0.36). Rti and the equipment component of Raw accounted for most of Rrs,osc (39.8+/-11.9 and 43.0+/-6.9%, respectively), whereas only a small portion belonged to Rawl (17.2+/-6.3%). It is concluded that respiratory resistance may become very insensitive to changes in lower airway resistance and therefore, inappropriate for following alterations in airway tone during mechanical ventilation, especially in patients with relatively normal respiratory mechanics, where the tissue and equipment resistances represent the vast majority of the total resistance.

Effect of axillary brachial plexus blockade on baroreflex-induced skin vasomotor responses: assessing the effectiveness of sympathetic blockade.

BACKGROUND: The combination of laser Doppler flowmetry and non-invasive blood pressure monitoring allows the continuous observation of cutaneous vascular resistance (CVR). Continuous recording of unmodulated skin blood flow (SBF) is very sensitive to artefacts, rendering the method unreliable. In contrast, intermittent short lasting challenges of the CVR by cardiovascular autonomic reflexes may provide information about the responsiveness of the sympathetic nervous system in the skin. METHODS: Eleven patients with below-wrist hand surgery (six males and five females; aged 35.2+/-7.1 years) performed Valsalva maneuver following axillary blockade. Skin blood flow was continuously monitored on the forearm of the side axillary blockade, as well as on the contra-lateral forearm, which was used as the control. The responses were expressed as changes compared with the baseline level derived from a resting period of 30 s. The maximal change in CVR was determined during the late strain phase of the Valsalva maneuver on both sides. For numerical comparison the change in CVR on the axillary blockade and control sides were simultaneously calculated. RESULTS: During the Valsalva maneuver a significant increase in CVR was observed on the control side with a maximum value during the late strain phase (baseline 0.18+/-0.1 and late strain phase 0.42+/-0.2 relative units; P<0.01). In contrast, only minimal changes were detected on the side of axillary blockade in CVR (baseline 0.17+/-0.8 and late strain 0.16+/-0.2 relative units; P=NS). CONCLUSIONS: Our findings support the disputed hypothesis that the human skin microvasculature is involved in baroreflex regulation under thermoneutral conditions. The determination of baroreflex stimulus-induced microvascular responses may serve as a feasible method for monitoring the effectiveness of sympathetic blockade.

[Surgical treatment of giant basilar artery aneurysm with induced hypothermia and circulatory arrest]. / Arteria basilaris óriásaneurysma mútéti kezelése hypothermiában végzett keringésmegállítás alatt.

Surgical management of giant and complex posterior circulation aneurysms continues to be a technically difficult task with high operative morbidity. To minimize morbidity we have used cardiopulmonary bypass and circulatory arrest for the treatment of a giant basilar aneurysm. A 48-year-old woman presented with sudden headache. Magnetic resonance angiography revealed a giant basilar aneurysm. On the 2nd hospital day she developed right sided hemiparesis and cranial nerve deficits as a result of the second rupture of the aneurysm. The aneurysm was successfully treated and no significant neurological complications were related to this technique. This initial experience indicates that patients with giant posterior circulation aneurysm that cannot be treated using conventional techniques might benefit from a surgical approach that included the use of deep hypothermic circulatory arrest.

[The importance of capnometry and pulse oximetry in laparoscopic cholecystectomy]. / Capnométer és pulzus-oximéter alkalmazásának jelentösége laparoscopiás cholecystectomiák során.

Recently the number of surgical and gynaecological operations performed via laparoscope has increased. The authors looked for the answer whether the carbon dioxide insufflated into the abdominal cavity during laparoscopy could cause significant change in the amount of carbon dioxide expired per minute. They measured the concentrations of carbon dioxide at the end of expiration, the amount of carbon dioxide produced per minute and the oxygen saturation during ataranaesthesia, muscle relaxation, intratracheal intubation and controlled mechanical ventilation in 20 cases of laparoscopic cholecystectomy. According to the results the amount of carbon dioxide exhaled per minute increased 1-3 minutes after insufflation and its maximum value was reached within 15-30 minutes (120-140% of the basic value). The continuous pulsoxymetrical examination showed that the constant intraperitoneal pressure equal or higher than 13-15 Hgmm could lead to the increase of the intrapulmonal shunt-circulation due to dystelectasis of the pulmonary bases. This could be prevented by increasing the respiratory pause-pressure to the level corresponding to the intraperitoneal pressure. In order to decrease the intraoperative anaesthesiological risks associated with the procedure the authors propose the use of capnometer and pulsoxymeter for the mentioned operation; this will keep level up with the relatively small risks associated with the postoperative period of the laparoscopic operations.