The effect of various surgical positions on vital capacity

Anesthesiologic effects of transperitoneal versus extraperitoneal approach during robot-assisted radical prostatectomy: results of a prospective randomized study

Objectives:

To compare the effects of CO₂ insufflation on hemodynamics and oxygen levels and on acid-base level during Robot-Assisted Radical Prostatectomy (RARP) with transperitoneal (TP) versus extra-peritoneal (EP) accesses.

Materials and Methods:

Sixty-two patients were randomly assigned to TP (32) and EP (30) to RARP. Pre-operation data were collected for all patients. Hemodynamic, respiratory and blood acid-base parameters were measured at the moment of induction of anesthesia (T0), after starting CO₂ insuffation (T1), and at 60 (T2) and 120 minutes (T3) after insufflation. In all cases, the abdominal pressure was set at 15 mmHg. Complications were reported according to the Clavien-Dindo classification. Student's two–t-test, with a significance level set at p<0.05, was used to compare categorical values between groups. The Mann-Whitney U-test was used to compare the median values of two nonparametric continuous variables.

Results:

The demographic characteristics of the patients in both groups were statistically comparable. Analysis of intra-operative anesthesiologic parameters showed that partial CO₂ pressure during EP was significantly higher than during TP, with a consequent decrease in arterial pH. Other parameters analysed were similar in the two groups. Postoperative complications were comparable between groups. The most important limitations of this study were the small size of the patient groups and the impossibility of maintaining standard abdominal pressure throughout the operational phases, despite attempts to regulate it.

Conclusions:

This prospective randomized study demonstrates that, from the anesthesiologic viewpoint, during RARP the TP approach is preferable to EP, because of lower CO₂ reabsorption and risk of acidosis.

Influence of pneumoperitoneum and postural change on the cardiovascular and respiratory systems in dogs

We investigated the influence of pneumoperitoneum#(PP) and postural change under inhalation anesthesia with isoflurane, which is routinely used in dogs, on the cardiovascular and respiratory systems. As test animals, 6 adult beagles were used. To induce anesthesia, atropine, butorphanol and propofol were intravenously injected. Anesthesia was maintained with 1.3 MAC (1.7%) isoflurane. The following were the experiment conditions: I:E ratio, 1:1.9; tidal air exchange, 20 ml/kg; and ventilation frequency, 14 times/min. Respiration was regulated so that the PaCO2 was approximately 35 to 40 mmHg before the start of the experiment. PP with CO2 (intraperitoneal pressure 15 mmHg) and a postural change (15°C) was performed during the experiment. As parameters of circulatory kinetics, heart rate (HR), mean aortic pressure (MAP), mean pulmonary arterial pressure (MPAP), central venous pressure (CVP), femoral venous pressure (FVP) and cardiac output (CO) were measured. As parameters of respiratory kinetics, airway pressure (PAW) and blood gas (BG) were measured. There were significant increases in HR, MAP, MPAP, CVP, FVP, CO, PAW and PaCO2 after PP in the horizontal position. There were significant increases in CVP, FVP, PAW and PaCO2 after PP in the Trendelenburg position. There were significant increases in the MPAP, CVP, FVP, PAW and PaCO2 after PP in the inverse Trendelenburg position. There was a significant difference in FVP after PP between the Trendelenburg position and inverse Trendelenburg position. The results of this experiment suggest that appropriate anesthesia control, such as changing the ventilation conditions after PP, is required for laparoscopic surgery under inhalation anesthesia with isoflurane.

A brief review: anesthesia for robotic prostatectomy

A brief review of the anesthesia for robotic prostatectomies, with a description of the procedure, the physiological principles involved, anesthetic management, problems, and possible complications.

Non-invasive ventilation corrects alveolar hypoventilation during spinal anesthesia

PURPOSE

To document and explain the beneficial effects of non-invasive ventilation in correcting hypoxemia and hypoventilation in severe chronic obstructive pulmonary disease, during spinal anesthesia in the lithotomy position.

CLINICAL FEATURES

A morbidly obese patient with severe chronic obstructive pulmonary disease underwent prostate surgery in the lithotomy position under spinal anesthesia. Hypoxemia was encountered during surgery, and a profound decrease of forced vital capacity associated with alveolar hypoventilation and ventilation/perfusion mismatching were observed. In the operating room, an M-mode sonographic study of the right diaphragm was performed, which confirmed that after spinal anesthesia and assuming the lithotomy position, there was a large decrease (-30%) in diaphragmatic excursion. Hypoxemia and alveolar hypoventilation were successfully treated with non-invasive positive pressure ventilation.

CONCLUSIONS

Intraoperative application of non-invasive positive pressure ventilation improved diaphragmatic excursion and overall respiratory function, and reduced clinical discomfort in this patient.

Lung aeration and pulmonary gas exchange during lumbar epidural anaesthesia and in the lithotomy position in elderly patients

We investigated a total of 36 subjects with a mean (SD) age of 65 (13) years, during baseline conditions (supine, before any anaesthesia), and then during one of the following protocols: (1) lithotomy positioning (n = 12), (2) epidural anaesthesia (n = 12), (3) general anaesthesia in the supine position (n = 12). Lung aeration, ventilation/perfusion matching, gas exchange and functional residual capacity were measured. Lung aeration was normal during baseline assessment with almost no regions with poor aeration and no substantial dependent densities. Shunt and perfusion of poorly ventilated regions were minor. Lithotomy positioning did not reduce functional residual capacity and did not affect aeration of the lung or ventilation/perfusion matching. Epidural anaesthesia, in general, had no effect on aeration, ventilation/perfusion matching or gas exchange, regardless of whether the patient was in the supine or lithotomy position. General anaesthesia, however, caused significant increases in poorly aerated lung regions and in dependent densities (interpreted as atelectasis). In conclusion, no or little impairment of lung aeration and ventilation/perfusion matching was caused by the lithotomy position and/or epidural anaesthesia, contrary to the effects seen during general anaesthesia. However, our findings also suggest that being overweight is a factor that may cause impairment of lung aeration.

General anesthesia using the laryngeal mask airway during brief, laparoscopic inspection of the peritoneum in children

The authors prospectively examined the cardiorespiratory changes seen with general anesthesia using the laryngeal mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of halothane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic blood pressure (SBP), end-tidal CO2 (ETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min prior to the start of laparoscopy and every minute during the laparoscopic procedure. A total of 15 patients were enrolled in the study ranging in age from 15 to 90 months (35.5 +/- 23.8 months) and in weight from 10 to 26.4 kg (14.9 +/- 4.9 kg). The length of the laparoscopy varied from 3 to 9 min (6.1 +/- 2.1 min). Although clinically insignificant, there was an increase in the heart rate from a baseline value of 141 +/- 9 to 148 +/- 9 beats/min (p = 0.0016) and in the SBP from a baseline value of 97 +/- 6 mm Hg to 101 +/- 7 mm Hg (p = 0.0087). The baseline tidal volume prior to the start of laparoscopy was 5.2 +/- 1.1 mL/kg and increased to 6.4 +/- 1.4 mL/kg during laparoscopy (p < 0.0001) while the respiratory rate increased from 32 +/- 4 to 40 +/- 6 breaths/min (p < 0.0001). ETCO2 increased from a baseline value of 47 +/- 6 to 53 +/- 6 torr (p = 0.0059). The maximum value of the ETCO2 was 55 torr or greater in 6 patients, exceeded 60 torr in 3 patients, with a maximum value of 63 torr. The increased ETCO2 returned to baseline within 2 to 7 min (4.7 +/- 1.5 min) following completion of the laparoscopy. There was no significant change in oxygen saturation. Our initial experience suggests that general anesthesia may be provided using the laryngeal mask during brief laparoscopic inspection of the peritoneum.

Cardiorespiratory changes in children during laparoscopy

The authors prospectively examined the cardiorespiratory changes during brief laparoscopy (less than 15 minutes) in children. Intraoperative ventilatory management included a tidal volume of 12 mL/kg, with the rate adjusted to achieve an end-tidal CO2 (PETCO2) of 30 to 35 mm Hg. The initial rate and tidal volume were not changed during the procedure. Baseline measurements of heart rate, blood pressure, peak inflating pressure (PIP), PETCO2, and oxygen saturation were recorded every minute for 5 minutes before the start of the laparoscopic procedure, and every minute during the laparoscopic procedure. Fifty-five patients were enrolled in the study (age range, 1 month to 7 years; weight range, 5.2 to 31 kg). PIP increased from the baseline value of 20 +/- 2.5 to 23 +/- 3.2 cm H2O (P < .01) during laparoscopy. The increase in PIP was 5 or more in six patients, with a maximum of 7. PETCO2 increased from the baseline value of 32 +/- 3.1 to 35 +/- 4.8 mm Hg (P < .01). The PETCO2 returned to baseline within 10 minutes after completion of the laparoscopy. No increase in ventilatory parameters was required during the brief laparoscopic procedure.

General anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children

We prospectively examined the cardiorespiratory changes seen with general anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of isoflurane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic/diastolic blood pressure (BP), end-tidal CO2 (PETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min before the start of laparoscopy and every minute during the laparoscopic procedure. A total of 20 patients were enrolled in the study, ranging in age from 15 to 80 months (mean 40.8 months) and in weight from 10.5 to 27 kg (mean 15.9 kg). The length of the laparoscopy varied from 3 to 18 min (mean 6.9 min). No significant changes (increase or decrease of 20% from baseline) of heart rate or BP occurred. Oxygen saturation remained at 98%-100% throughout the procedure in all patients. The baseline tidal volume before the start of laparoscopy was 6.27 +/- 1.9 mL/kg and increased to 7.3 +/- 2.2 mL/kg during laparoscopy (p = 0.01). The baseline respiratory rate was 27.7 +/- 7.0 breaths/min and increased to 33.5 +/- 7.2 breaths/min during laparoscopy (p = 0.0001). PETCO2 increased from a baseline value of 37.5 +/- 6.5 to 44.6 +/- 6.8 mm Hg (p = 0.0001). The increase in PETCO2 was 10 or greater in 3 patients and exceeded 50 mm Hg in 3 patients, with a maximum value of 66 torr.(ABSTRACT TRUNCATED AT 250 WORDS)

Laparoscopic surgery--anesthetic implications

Laparoscopic cholecystectomy is a relatively new surgical procedure which is enjoying ever-increasing popularity and presenting new anesthetic challenges. The advantages of shorter hospital stay and more rapid return to normal activities are combined with less pain associated with the small limited incisions and less postoperative ileus compared with the traditional open cholecystectomy. The efficacy of laparoscopic appendectomy and hemicolectomy has been recently evaluated. However, there have been no prospective randomized studies to date comparing laparoscopic with traditional laparotomy techniques. The physiological effects of prolonged pneumoperitoneum and the longer duration of surgery with the laparoscopic techniques are of concern. The application of laparoscopic inguinal hernia repair may be limited because, unlike traditional surgical hepair, general anesthesia is required and concerns have been expressed about the duration of surgery and the possibility of hernia recurrence. Notwithstanding case reports and series describing successful diaphragmatic and hiatus hernia repair using a laparoscopic surgical technique, the frequently encountered complications of cervical surgical emphysema, pneumothorax, and pneumomediastinum, attributed to passage of insufflating gas through weak points or defects in the diaphragm, must be of major concern. Anesthesiologists must maintain a high index of suspicion for these potential complication and must undertake appropriate monitoring. If there is clinical evidence of a tension pneumothorax, immediate chest tube decompression is indicated. Intraoperative complications of laparoscopic surgery are mostly due to traumatic injuries sustained during blind trocar insertion and physiological changes associated with patient positioning and pneumoperitoneum creation. The choice of anesthetic technique for upper abdominal laparoscopic procedures is most frequently limited to general anesthesia. Controlled ventilation avoids hypercarbia, and an anesthetic technique incorporating antiemetics and nonsteroidal anti-inflammatory agents has reduced postoperative nausea and vomiting following laparoscopic cholecystectomy. The use of nitrous oxide during laparoscopic procedures remains controversial. Laparoscopic cholecystectomy is a major advance in the management of patients with symptomatic gall-bladder disease. However, in the present era of cost containment, older and sicker patients may present for this procedure on the day of surgery without adequate preoperative evaluation. Anesthesiologists should thus be prepared to recommend deflation of the pneumoperitoneum and possibly conversion to an open procedure if hemodynamic, oxygenation, or ventilation difficulties arise during the procedure.

Anaesthesia for translumbar aortography

Fifty patients presenting for elective translumbar aortography were randomly allocated to one of two groups receiving either enflurane or isoflurane. Premedication was with oral lorazepam. The patients' tracheas were intubated and they were allowed to breathe spontaneously in the prone position during the procedure. There was no significant difference in heart rate during the investigation but there was a statistically significant fall in the blood pressure from its pre-induction level. Arterial oxygenation was adequate throughout the procedure. Arterial carbon dioxide tension was significantly lower in the isoflurane group at the beginning and at end of the procedure (p less than 0.01), but there was no significant change in carbon dioxide tension within the groups during the procedure. Spontaneous ventilation with enflurane or isoflurane is a satisfactory anaesthetic technique for translumbar aortography.

Blood volume distribution in the Trendelenburg position

The Trendelenburg position is used frequently in treating hypotensive patients. It is believed that placing patients in the Trendelenburg position causes an autotransfusion of blood to the central circulation. No published studies document the volume of blood displaced centrally. In our study ten volunteers were placed in the Trendelenburg position. Blood volumes were determined from body surface area, and radionuclide scanning was used to determine blood volume distribution. Placing normovolemic volunteers in the Trendelenburg resulted in a 1.8% (median) displacement of the total volume centrally. The autotransfusion of blood produced by the Trendelenburg position is small and is unlikely to have an important clinical effect.

Posture with elevated and extended thorax. The influence of the position on some haemodynamic and ventilatory parameters under general anaesthesia

The effects of a change in posture from flat supine to supine with elevated and extended thorax have been investigated in 12 healthy patients under general anaesthesia prior to elective surgery on the stomach. The following parameters were measured: pulse rate, mean arterial blood pressure (MABP), central venous pressure (CVP), ventilation pressure, oesophageal pressure, and arterial oxygen and carbon dioxide tensions. Changes were measured as deviations from initial values before the change of position at 4 and 15 min after the change. One patient (8%) had a 31% fall in MABP and a 87% fall in CVP, requiring treatment outside the standard procedure, but acceptable values were obtained by simple means. Eleven patients showed only minor changes: a mean initial rise in pulse rate of 10% and a fall in CVP of 25%, after which the pulse rate returned to the initial level and the CVP remained stable. MABP was unchanged, as were ventilation pressure, oesophageal pressure and gas tensions. On the basis of reports in the literature and findings in this study, it is concluded that otherwise healthy patients tolerate the posture well, the slight risk of haemodynamic complications being outweighed by the surgical advantages. This posture should be used with caution in patients who may be haemodynamically unable to compensate.