Pseudoobstruction of the colon: early recognition and therapy.

A case of pseudoobstruction of the colon in a patient receiving oral nimodipine therapy is presented. Early recognition of this entity, diagnostic aids, and therapy are discussed. Successful colonoscopic decompression and close observation allowed completion of nimodipine course of therapy.

Retained fragment of a lumbar subarachnoid drain.

We present two patients who each had a retained subarachnoid drain catheter broken during postoperative removal. Management of these fragments should be individualized. The fragment remained in one patient, but was removed in the other because of further procedures required for hydrocephalus. We discuss possible causes of this complication as well as suggestions for prevention.

Anesthesia with antiphospholipid antibodies: anesthetic management of a parturient with lupus anticoagulant and anticardiolipin antibody.

The anesthetic management of a parturient with a circulating lupus anticoagulant and an anticardiolipin antibody presenting to the obstetric suite taking heparin and aspirin is discussed. Issues concerning placement of a regional anesthetic with recent aspirin ingestion and heparin therapy are discussed. Documentation of heparin dissipation via a whole blood heparin concentration assay before induction of regional anesthesia, including several laboratory tests that could be used in monitoring coagulation status in this patient population, is discussed in detail.

Intraoperative use of automated external defibrillator.

We report on the anesthetic management of a patient with peripartum cardiomyopathy and frequent episodes of ventricular tachycardia, who underwent surgery for tracheal stenosis. Prior to this surgery, the patient had been implanted with an automatic implantable cardioverter-defibrillator (AICD), placed abdominally. In the operating room, the AICD was deactivated, and an automated external defibrillator (AED) was placed. Intraoperatively, the AED identified and treated the patient's ventricular tachycardia. Advantages of the AED in this hospital setting included rapid response to the cardiomyopathy, safe, hands-free operation, and minimal disruption of the surgical procedure. Safety concerns when using the AED are also detailed.

Effects of split torso positioning and laparoscopic surgery for donor nephrectomy on respiratory mechanics.

STUDY OBJECTIVE: To test whether split torso positioning, abdominal insufflation, and other procedures performed during laparoscopic nephrectomy would affect mechanical impedances to inflation [i.e., elastance (E) and resistance (R) of the total respiratory system (Ers, and Rrs), lungs (EL and RL), and chest wall (Ecw and Rcw)] differently from previously studied laparoscopic procedures. DESIGN: Unblinded study, each patient serving as own control. SETTING: University hospital. PATIENTS: 12 ASA physical status I and II patients scheduled for laparoscopic donor nephrectomy, all without cardiopulmonary disease. INTERVENTIONS: Patients were anesthetized and paralyzed, tracheally intubated and mechanically ventilated at 10, 20, and 30 breaths/minute and at tidal volumes of 250, 500, and 800 ml. Measurements were made in the following positions: supine, split torso, abdominal insufflation (Pab = 15 mmHg), and supine after deflation. MEASUREMENTS AND MAIN RESULTS: Airway flow and pressure and esophageal pressure were measured. Discrete Fourier transformation was used to calculate E and R. These were analyzed with repeated measures, linear multiple regression with accepted level of significance at p < 0.05. Ers, Ecw, and Rcw increased (p < 0.05) while EL decreased (p < 0.05) when patients changed from supine to split torso. During Pab = 15 mmHg, Ers, Ecw, and Rcw increased further and Rrs and RL increased (p < 0.05). Following abdominal deflation, Ecw and Ers remained elevated (p < 0.05). The changes in Ecw caused by laparoscopy and surgery were greater than we have previously measured in other laparoscopic procedures, while the changes in EL were less. CONCLUSIONS: Laparoscopic nephrectomy affects lung and chest wall mechanical properties differently from other laparoscopic procedures. This finding could be due to the split torso positioning, and the effects of abdominal swelling on the chest wall caused by administration of more perioperative fluids with laparoscopic nephrectomy.

Effects of Trendelenburg and reverse Trendelenburg postures on lung and chest wall mechanics.

STUDY OBJECTIVE: To test whether the Trendelenburg ("head-down") or reverse Trendelenburg ("head-up") postures change lung and chest wall mechanical properties in a clinical condition. DESIGN: Unblinded study, each patient serving as own control. SETTING: University of Maryland at Baltimore Hospital, Baltimore, Maryland. PATIENTS: 15 patients scheduled for laparoscopic surgery. INTERVENTIONS: Patients were anesthetized and paralyzed, tracheally intubated and mechanically ventilated at 10 to 30 per minute and at a tidal volume of 250 to 800 ml. Measurements were made before surgery in supine, head-up (10 degrees from horizontal) and head-down (15 degrees from horizontal) postures. MEASUREMENTS AND MAIN RESULTS: Airway flow and airway and esophageal pressures were measured. From these measurements, discrete Fourier transformation was used to calculate elastances and resistances of the total respiratory system, lungs, and chest wall. Total respiratory elastance and resistance increased in the head-down posture compared with supine due to increases in lung elastance and resistance (p < 0.05); but chest wall elastance and resistance did not change (p > 0.05). Lung elastance also exhibited a negative dependence on tidal volume while head-down that was not observed in the supine posture. The change in lung elastance compared with supine was positively correlated to body mass index (weight/height2) and negatively correlated to tidal volume. Lung and chest wall elastance and resistance were not affected by shifting from supine to head-up (p > 0.05). CONCLUSIONS: The Trendelenburg posture increases the mechanical impedance of the lung to inflation, probably due to decreases in lung volume. This effect may become clinically relevant in patients predisposed with lung disease and in obese patients.

Effects of PEEP on respiratory mechanics are tidal volume and frequency dependent.

How the effects of frequency, tidal volume (VT) and PEEP interact to determine the mechanical properties of the respiratory system is unclear. Airway flow and airway and esophageal pressures were measured in ten intubated, anesthetized/paralyzed patients during mechanical ventilation at 10-30 breaths/min and VT of 250-800 ml. From these measurements, Fourier transformation was used to calculate elastance (E) and resistance (R) of the total respiratory system (subscript rs), lungs (subscript L) and chest wall (subscript cw) at 5, 10 and 0 cm PEEP. As PEEP increased from 0-5 cmH2O, all elastances and resistances decreased (P < 0.05). Increasing PEEP to 10 cmH2O decreased EL, Rrs, and RL further (P < 0.05). The changes in Ers, EL, Rrs and RL caused by PEEP were less (P < 0.05) as VT increased, while changes in Rrs, RL and Ers were less (P < 0.05) as frequency increased. VT dependences in Ers and Rrs were enhanced (P < 0.05) at 0 cmH2O PEEP. The ratio of EL to chest wall elastance was not affected by PEEP (P > 0.05), but increased (P < 0.05) with increasing VT at 5 and 10 cmH2O PEEP. We conclude that it is critical to standardize ventilatory parameters when comparing groups of patients or testing clinical intervention efficacy and that the differential effects on the lungs and chest wall must be considered in optimizing the application of PEEP.

The effects of increased abdominal pressure on lung and chest wall mechanics during laparoscopic surgery.

We tested the hypothesis that increases in pressure in the abdomen (Pab) exerted by CO2 insufflation during laparoscopy would increase elastance (E) and resistance (R) of both the lungs and chest wall. We measured airway flow and airway and esophageal pressures of 12 anesthetized/paralyzed tracheally intubated patients during mechanical ventilation at 10-30/min and tidal volume of 250-800 mL. From these measurements, we used discrete Fourier transformation to calculate E and R of the lungs and chest wall. Measurements were made at 0, 15, and 25 mm Hg Pab in the 15 degrees head-down (Trendelenburg) posture and at 0 and 15 mm Hg Pab in the 10 degrees head-up (reverse Trendelenburg) posture. Lung and chest wall Es and Rs while head-down increased at Pab = 15 mm Hg, and both Es increased further at Pab = 25 mm Hg (P < 0.05). Both Es and Rs also increased while head-up at Pab = 15 mm Hg (P < 0.05), but increases in lung E and R were less than while head-down (P < 0.05). The increase in lung E and R at Pab = 15 mm Hg in either posture were positively correlated to body weight or body mass index, whereas the increases in chest wall E and R were negatively correlated to the same factors (P < 0.05). Lung and chest wall mechanical impedances increase with increasing Pab; the increases depend on body configuration and are greater while head-down.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in lung and chest wall properties with abdominal insufflation of carbon dioxide are immediately reversible.

Previously we have reported that large increases in lung and chest wall elastances as well as lung resistance occur with abdominal insufflation of carbon dioxide during laparoscopic surgery. To examine whether these effects were reversible with abdominal deflation, we calculated lung and chest wall elastances and resistances from measurement of airway flow and pressure and esophageal pressure in 17 anesthetized/paralyzed patients undergoing laparoscopic surgery. Measurements were made immediately prior to abdominal insufflation and after deflation. Lung and chest wall elastances and resistances were not changed from baseline (P > 0.05), although total respiratory elastance remained slightly increased compared to baseline (P < 0.05). The change in total respiratory elastance did not correlate with abdominal insufflation time, surgical site, smoking history, or physical characteristics of the patients. There were no differences in frequency and tidal volume dependences of the elastances and resistances before and after abdominal insufflation (P > 0.5). We conclude that residual changes in respiratory mechanics caused by carbon dioxide insufflation during laparoscopic surgery are minor, and that the reported compromise of respiratory function indicated by pulmonary function tests after laparoscopy does not appear to be due to changes in passive mechanical properties of the lungs or chest wall.

Transesophageal echocardiographic detection of gas embolism and cardiac valvular dysfunction during laparoscopic nephrectomy.

UNLABELLED: We used transesophageal echocardiography (TEE) to monitor venous gas embolism, cardiac performance, and the hemodynamic effects of positioning and pneumoperitoneum in 16 healthy kidney donors undergoing laparoscopic nephrectomy. A four-chamber view was used continuously, except at predetermined intervals, when a complete TEE examination for cardiac function was performed. Other clinical variables recorded include systolic, diastolic, and mean arterial blood pressure; heart rate (HR), pulse oximetric saturations; and end-tidal CO2. Baseline valvular incompetence was seen in 13 of the 16 patients when supine and asleep. After positioning for surgery and induction of pneumoperitoneum, TEE revealed valvular incompetence with regurgitation more pronounced from baseline in 15 of the 16 patients. In one patient, during renal vein dissection, gas entered the right atrium from the inferior vena cava, worsening tricuspid regurgitation. Hemodynamic variables and ejection fraction were tested by using repeated-measures analysis of variance for significance (P < 0.05). Pneumoperitoneum increased (P < 0.05) systolic blood pressure (from 102.8 +/- 3.89 to 120.8 +/- 3.88 mm Hg) and HR (from 68.9 +/- 3.19 to 75.6 +/- 2.62). Ejection fraction was unchanged. The high incidence of valvular incompetence indicates that further studies are needed to assess these effects during laparoscopic nephrectomy with cardiac disease. IMPLICATIONS: Laparoscopic surgery has gained popularity as a procedure for the removal of donated kidneys. Although the insufflation of gas necessary for this relatively simple approach poses a low risk of venous air embolism, it may increase the risk of changes in valvular competency.

Lung, chest wall, and total respiratory system resistances and elastances in the normal range of breathing.

We measured total respiratory system and lung and chest wall resistances (Rrs, Rl, and Rcw) and elastances (Ers, El, and Ecw) in awake, relaxed human subjects during sinusoidal volume forcing at the mouth from 0.2 to 0.6 Hz with tidal volumes (VT) of 6 to 18% VC at constant mean airway pressure. In addition, we repeated measurements with the lowest VT at a lower airway pressure and therefore at a lower mean lung volume (Vl). Rrs and Rcw decreased with increasing respiratory frequency (f) and VT, but Rl was independent of f and VT. All resistances were higher at the lower Vl. Ers and Ecw increased with increasing f and decreased with increasing VT. El increased slightly with increasing f but was not affected by VT. All elastances tended to increase at the lower Vl. We conclude that in the normal range of breathing amplitude and frequency, (1) lung properties are nearly constant if mean lung volume does not change, and (2) f and VT dependencies of total respiratory system properties are caused by the chest wall.