Halothane concentrations required to block the cardiovascular responses to incision (MAC CVR) in infants and children

Enflurane requirement for blocking adrenergic responses to incision in infants and children

BACKGROUND

Enflurane is one of the most commonly used inhaled anesthetics in China, but its requirement to block adrenergic responses after skin incision in pediatric patients is still unknown. This study was to determine the minimum alveolar anesthetic concentration (MAC) of potent inhaled anesthetics required to blunt the adrenergic response to skin incision of enflurane (MACBAR) in infants and children.

METHODS

Twenty-eight patients, 10 infants (6-12 months) and 18 young children (1-6 years), were studied. The 18 children were randomly assigned into two groups, with or without fentanyl. Anesthesia was induced with 3 mg/kg propofol and 0.15 mg/kg vecuronium, and maintained with enflurane in 100% oxygen. Fentanyl (3 microg/kg) was given intravenously 5 minutes before incision for the patients of fentanyl group. The "up and down" method (with 0.3 MAC as a step size and 1 MAC as the start dose) was applied to determine MACBAR. The response was considered positive if the mean arterial pressure (MAP) or heart rate (HR) increased > or =15% after incision. The MACBAR was calculated as the mean of four independent cross-over responses in each group.

RESULTS

MACBAR of enflurane in children of 1-6 years old was 3.2% (95% CI, 2.8%-3.6%) and was reduced to 2.2% (95% CI, 1.8%-2.5%) by 3 microg/kg fentanyl. In infants of 6-12 months old, the MACBAR of enflurane was 3.4% (95% CI, 3.0%-3.8%).

CONCLUSIONS

MACBAR of enflurane in infants older than 6 months is similar to that in young children. The MACBAR of enflurane decreases with co-administration of fentanyl in the pediatric population.

Clinical features and echocardiography of embolism during cemented hip arthroplasty

PURPOSE

In previous studies the degree of embolization detected by transoesophageal echocardiography (TEE) during cemented total hip arthroplasty (THA) did not correlate with changes in haemodynamic variables nor did it result in persistent ventilation-perfusion mismatching. The aim of this study was to record evidence of embolism and to relate the findings to demographic data and the subsequent clinical course of the patients during THA.

METHOD

Forty-eight patients scheduled to undergo elective cemented THA during general anaesthesia were monitored. A TEE probe was inserted with special attention to the right atrium (RA), the right ventricle (RV) Haemodynamic (heart rate, arterial blood pressure, central venous pressure) and blood-gas variables were measured repeatedly during the operative procedure (after induction, placement of the acetabular component, placement of the femoral component, relocation of the hip joint). Grading of venous embolism at these times was based on the size of particles detected by TEE (three-minutes video segments of each periods) and correlated with demographic, haemodynamic and blood-gas data.

RESULTS

The TEE monitoring revealed showers of echogenic material traversing the RA and RV in all but one patients during reaming and cementing of the acetabular and femoral components, and during relocation of the hip joint. No correlation was observed between frequency or size of embolic particles and demographic or blood-gas and haemodynamic variables studied at the same times.

CONCLUSION

This study failed to show any clinical impact of TEE detected emboli during cemented THA.

Embolism detected by transoesophageal echocardiography during hip arthroplasty

This case report demonstrates embolization of echogenic material detected by transoesophageal echocardiography during a cemented total hip arthroplasty in a 76-yr-old woman without patent foramen ovale. During the placement of the acetabular and femoral components, and during relocation of the hip joint, a "snow flurry" appearing in the right atrium was followed by several highly echogenic and mobile emboli of various sizes, some of them with a vermiform shape 1 to 5 cm long. At skin closure, echogenic material was seen in the right branch of the pulmonary artery adherent to the vascular wall of the bifurcation of the main pulmonary artery. No changes were observed in any haemodynamic variable monitored (heart rate, systemic and right atrial pressures). Also, no desaturation was detected by pulse oximetry and blood gases at the time of embolism and there was no decrease in PETCO2. This case report is in line with other studies which failed to show a haemodynamic impact of TEE detected emboli during THA.

Amniotic fluid embolus

A case report of a 27-yr-old healthy patient for Caesarean section under epidural anaesthesia is presented. The patient suffered an acute cardiorespiratory collapse when the infant's head was being delivered through the anterior abdominal wall. The patient remained cyanosed after proper tracheal intubation and pulmonary ventilation with 100% O2. Hypotension was difficult to treat but returned to normal 25 min after the event. A pulmonary artery catheter inserted three hours after the event showed normal pressures and a high cardiac output. The patient suffered permanent neurological damage. The differential diagnosis is discussed and current concepts of the aetiology and management of amniotic fluid embolism reviewed.