Classics in ECT: 1990 Paper on Hyperventilation

"Classics in ECT" brings you this paper from researchers at the University of Michigan:

Effect of hyperventilation on seizure length during electroconvulsive therapy.

Pande AC, Shea J, Shettar S, Grunhaus LJ, Haskett RF.Biol Psychiatry. 1990 Apr 1;27(7):799-801. doi: 10.1016/0006-3223(90)90597-u.PMID: 2109642 

The pdf is here.

And from the text:

Comparison of seizure length showed that the lowest pCO2 group had the longest first seizure among the 3 groups. Within the series of 5 treatments in each group the first seizure was the longest as well. Seizure length declined precipitously by the second treatment, and subsequent treatments were indistinguishable for seizure length either among or within groups.
...There are major methodological differences between this study and Bergsholm et al. (1984), thus making a comparison of results difficult. These authors intubated all patients, used etomidate as the anesthetic agent, and crossed patients from hyper- to normooxygenation and hypo-to-normocapnia in successive treatments so as to demonstrate differential effects of the two ventilatory states on EEG-monitored secure length. On the contrary, we were looking for a clearly demonstrable effect of varying levels of hypocapnia that could have clinical utilility. Hence, we adhered as closely as possible to our usual ECT procedure while varying the rate of ventilation to influence the end-tidal pCO2. Although we used a higher than usual methohexital dose, all groups were subject to the same dose, hence this factor alone may not explain our inability to find as robust an effect of hypocapnia on seizure length as did Bergsholm et al. (1984). We suggest that hypocapnia as a strategy for prolonging seizure duration in routine clinical practice needs further study before it can be adopted into routine ECT practice. Moreover, as Bergsholm et al. (1984) have pointed out, the relationship of longer seizures to the clinical efficacy of ECT is in need of confirmation as well.

Following up on yesterday's classic paper, this is neither the first, nor the last, word on hyperventilation in ECT, but it is interesting nonetheless. These investigators showed that hyperventilation-induced hypocapnia increased seizure length at the first treatment, but not subsequently. They studied 5 patients, but did not have a within-patient crossover design, limiting their conclusions. They needed to intubate patients in the lowest CO2 group.

Worth a full read, only ~10 minutes.