The hyperventilation of cirrhosis: progesterone and estradiol effects.

Progesterone and estradiol are metabolized in the liver and are elevated in patients with cirrhosis. Progesterone stimulates ventilation by activating progesterone receptors in the central nervous system; estradiol may facilitate progesterone's actions by increasing progesterone receptors. This study evaluated whether progesterone and estradiol contribute to the respiratory alkalosis common in cirrhotic patients. Arterial blood gases and progesterone and estradiol levels were obtained in 50 patients with cirrhosis. Multiple linear regression revealed a statistically significant correlation between PaCO2 and progesterone and estradiol (r = .54, P < .05). Patients with severe hyperventilation (PaCO2 < or = 30 mm Hg) had statistically higher levels of progesterone and estradiol than did patients with mild hyperventilation (30 < PaCO2 < or = 35) or normal ventilation (PaCO2 > 35) (P < .05). Although the progesterone levels were two orders of magnitude lower than those associated with hyperventilation in pregnant patients, the increased ventilatory effect may be because of the altered blood-brain barrier (BBB) present in cirrhotic patients. Progesterone and estradiol appear to contribute to the hyperventilation in cirrhotic patients.

Comparison of end-tidal and arterial carbon dioxide in infants using laryngeal mask airway and endotracheal tube.

The laryngeal mask airway (LMA) has become a popular tool for airway management in selected adult and pediatric patients undergoing routine surgical procedures. The relationship between end-tidal and arterial carbon dioxide during controlled ventilation via the LMA in infants under 10 kg has not been reported. After induction of general anesthesia, the LMA was placed in 12 healthy infants and mechanical ventilation initiated. After maintaining steady-state level of end-tidal carbon dioxide (minimum 5 min), an arterial blood sample was obtained and end-tidal carbon dioxide level noted. The laryngeal mask was then removed, the trachea intubated, and mechanical ventilation resumed with initial ventilatory variables. After reaching a steady-state level of end-tidal carbon dioxide, a second arterial sample was obtained and end-tidal carbon dioxide level noted. The mean end-tidal carbon dioxide and arterial partial pressure of carbon dioxide obtained during ventilation were 42.2 +/- 7.9 and 47.1 +/- 11.0 (LMA) and 37.4 +/- 4.6 and 42.6 +/- 6.7 (endotracheal tube), respectively. Analysis of differences between partial pressure of carbon dioxide and end-tidal carbon dioxide using the Bland and Altman method revealed bias+/-precision of 4.9 +/- 3.9 and 5.3 +/- 3.2 with ventilation via the laryngeal mask and endotracheal tube. Our data indicate that, while ventilating infants under 10 kg with LMA, end-tidal carbon dioxide is an accurate indicator of arterial partial pressure of carbon dioxide.

Effect of methohexitone and propofol with or without alfentanil on seizure duration and recovery in electroconvulsive therapy.

We have studied the effects of methohexitone and propofol with and without alfentanil on seizure duration and recovery in this observer-blinded, prospective, randomized, crossover study involving 24 patients undergoing electroconvulsive therapy (ECT). Each patient had four treatment sessions, and received the following four i.v. regimens in random order: methohexitone 0.75 mg kg-1, methohexitone 0.50 mg kg-1 and alfentanil 10 micrograms kg-1, propofol 0.75 mg kg-1, propofol 0.50 mg kg-1 and alfentanil 10 micrograms kg-1. Additional methohexitone or propofol was given as needed in 10-20-mg increments until loss of consciousness. Suxamethonium 1.0 mg kg-1 i.v. was given for muscular paralysis. Mean motor and EEG seizure durations were longer with methohexitone-alfentanil (44.7 (SD 15.0) and 70.5 (29.7) s) than with methohexitone (37.6 (12.6) and 52.6 (15.3) s) and similarly, seizures were longer with propofol-alfentanil (36.8 (15.2) and 54.5 (20.9) s) than with propofol alone (27.2 (11.9) and 39.2 (3.9) s). Seizures were longest with methohexitone-alfentanil and shortest with propofol. Recovery time was statistically shorter in patients receiving propofol compared with methohexitone-alfentanil and methohexitone alone. Alfentanil with a reduced dose of methohexitone or propofol provided unconsciousness and increased seizure duration in patients undergoing ECT. We conclude that the combination of methohexitone with alfentanil is a good regimen for ECT, especially for patients with short seizure duration.

Relationship between end-tidal and arterial carbon dioxide with laryngeal mask airways and endotracheal tubes in children.

The laryngeal mask airway (LMA) is a useful tool for securing the airway in adults and children and may be substituted for an endotracheal tube (ETT) in selected patients undergoing general anesthesia. The correlation between end-tidal and arterial carbon dioxide during controlled ventilation via LMA has not been reported in a within-patient design in pediatric patients. After induction of general anesthesia, 22 children had a LMA placed and mechanical ventilation initiated. After reaching steady-state end-tidal carbon dioxide (PETCO2), an arterial blood sample was obtained and the partial pressure of carbon dioxide (PaCO2) was measured. The LMA was then removed, the trachea was intubated, and identical ventilatory variables were resumed. After a stable PETCO2 was reestablished (minimum 5 min), a second PaCO2 was measured and the PETCO2 recorded. The mean PETCO2 and PaCO2 obtained during ventilation via the LMA were 37.7 +/- 3.31 and 41.9 +/- 9.09, respectively. The mean PETCO2 and PaCO2 obtained during ventilation via the ETT were 35.2 +/- 2.86 and 39.2 +/- 5.25, respectively. Analysis of differences between PaCO2 and PETCO2 revealed a bias +/- precision of 4.0 +/- 3.42 and 4.2 +/- 3.66 with ventilation via ETT and LMA, respectively. The root mean square error was 0.85 for the ETT and 0.89 for the LMA. Our results indicate that in infants and children weighing more than 10 kg who are mechanically ventilated via the LMA PETCO2 is as accurate an indicator of PaCO2 as when ventilated via ETT.