Guy Annat

Spontaneous Cardiac Baroreflex in Humans Comparison With Drug-Induced Responses

We compared two methods of assessment of baroreflex sensitivity in eight supine healthy volunteers during repeated baseline measurements and various conditions of cardiac autonomic blockade. The spontaneous baroreflex method involved computer scanning of recordings of continuous finger arterial pressure and electrocardiogram to locate sequences of three or more beats in which pressure spontaneously increased or decreased, with parallel changes in pulse intervals. The mean regression slope of all these sequences during each study condition was considered to represent the mean spontaneous baroreflex slope. In the drug-induced method, sigmoidal curves were constructed from data obtained by bolus injections of phenylephrine and nitroprusside; the tangents taken at the resting pressure of each of these curves were compared with the mean spontaneous baroreflex slopes. The two methods yielded slopes that were highly correlated (r = .96, P < .001), with significant but similar intraindividual baseline variability. Atropine virtually eliminated the baroreflex slope; subsequent addition of propranolol did not alter it further. Propranolol or clonidine alone increased average baroreflex slope to the extent that they increased resting pulse interval (r = .69 to .83). The spontaneous baroreflex method provides a reliable, noninvasive assessment of human vagal cardiac baroreflex sensitivity within its physiological operating range.

Pulmonary CO2 elimination during surgical procedures using intra- or extraperitoneal CO2 insufflation

We examined end-tidal CO2 tension (PETCO2) and pulmonary CO2 elimination of CO2 (&OV0312;ECO2) during CO2 insufflation under general anesthesia for three surgical procedures: gynecologic laparoscopy (intraperitoneal CO2 insufflation for 43 ± 4 min), laparoscopic cholecystectomy (intraperitoneal CO2 insufflation for 125 ± 14 min), and pelviscopy (extraperitoneal CO2 insufflation for 45 ± 3 min). All patients (10 in each pup) underwent controlled mechanical ventilation. Oxygen consumption (&OV0312;O2) and &OV0312;ECO2 were measured at 2-min intervals by a system using a mass spectrometer. For the three surgical procedures, &OV0312;O2 remained stable, whereas &OV0312;ECO2 and PETCO2 increased in parallel from the 8th to the 10th min after the start of CO2 insufflation. A plateau was reached 10 min later in patients having intraperitoneal insufflation, whereas &OV0312;ECO2 and PETCO2 continued to increase slowly throughout CO2 insufflation during pelviscopy. During pelviscopy, the maximum increase in &OV0312;ECO2 and PETCO2 (76 ± 5% and 71 ± 7%) was significantly more pronounced than that observed during cholecystectomy (25 ± 4% and 25 ± 4%) and gynecologic laparoscopy (15 ± 3% and 12 ± 2%). The authors conclude that CO2 diffusion into the body is more marked during extraperitoneal than during intraperitoneal CO2 insufflation but is not influenced markedly by the duration of intraperitoneal insufflation.

Clinical validation of the Deltatrac monitoring system in mechanically ventilated patients

AbstractObjectiveTo evaluate a monitor of pulmonary gas exchange (Deltatrac, Datex) in a clinical setting.DesignAfter in vitro evaluation, comparison over 2 min between

OXYGEN UPTAKE AFTER MAJOR ABDOMINAL SURGERY : EFFECT OF CLONIDINE

\dot VO_2

Energy Expenditure during Severe Acute Pancreatitis

and

Continuous measurement of pulmonary gas exchange during general anaesthesia in man

\dot VCO_2