Elevated lactate during psychogenic hyperventilation

Om CO2 relatert til melkesyre. Denne er ifh panikkangst, men gjelder også ifh trening og hva som helst av aktivitet eller sykdom hvor melkesyre er et element å ta hensyn til.

http://emj.bmj.com/content/28/4/269.long

«Whereas high lactates are usually associated with acidosis and an increased risk of poor outcome, in patients with psychogenic hyperventilation, high lactates are associated with hypocapnia and alkalosis.»

«However, provoked hyperventilation, a less life-threatening condition, has been shown to result in elevated lactate levels as well. Passive overbreathing under anaesthesia has been shown to induce hyperlactataemia in various studies.9 10 Furthermore, active voluntary overbreathing in individuals with panic disorders has been related to the development of a marked hyperlactataemia as well.11 12»

«As expected, median Pco2 (4.3 (2.0–5.5)) was below the lower reference value of 4.6 kPa, and median pH was slightly increased (7.47 (7.40–7.68)). Po2 and saturation were normal in all the patients without supplementary oxygen (table 1). Fourteen participants had a lactate level above the reference value of 1.5 mmol/l, of which 11 were still hyperventilating at the moment of drawing their blood, as reflected by the Pco2 values <4.6 kPa. The participants who were still actively hyperventilating had a higher median pH of 7.50 (7.42–7.68) versus 7.44 (7.40–7.49) (p<0.01) and a higher median lactate level of 1.4 (0.7–4.4) versus 0.9 (0.5–3.5) (p<0.01) compared with the participants diagnosed as having psychogenic hyperventilation who had ceased to actively hyperventilate at the moment of drawing their blood. In line with the higher pH in this group, bicarbonate and potassium concentrations were lower (table 1).»

«In univariate correlation analysis, there was a significant positive correlation of plasma lactate with both Po2 and pH, whereas significant inverse relations were found for potassium and bicarbonate (table 2). Most interestingly, a significant negative correlation was found between Pco2 and arterial lactate (r=−0.50, p<0.001; figure 2). This negative correlation was specifically present in patients with hypocapnia (ie, Pco2 <4.6 kPa): in these patients, there was a moderate significant negative correlation between Pco2 and plasma lactate levels (r=−0.53, p<0.003), whereas this correlation was not seen in normocapnic participants (r=−0.17, NS).»

«Scatter plot of the relation of Pco2 with lactate for patients diagnosed as having psychogenic hyperventilation (n=46). Depicted are the regression line in bold (r2=0.25, p<0.001), with estimated 95% CIs. The vertical dashed line denotes the lower reference value of arterial Pco2; and the horizontal line, the upper reference value of lactate.»

«In our study, we showed that lactate levels are elevated in 30% of the participants with psychogenic hyperventilation who present at the ED. Furthermore, we demonstrate that under these circumstances, Pco2 is the most important predictor of arterial lactate levels and that in this context, an elevated lactate level should not be regarded as an adverse sign.»

«The reported 0.5% incidence of hyperventilation in our study population seems to be low compared with that in previous studies, reporting incidences of 6%–11%.14» «We suppose that the relatively low incidence in our study population could be related to a substantial amount of patients with psychogenic hyperventilation who are not referred to the hospital at all by their general practitioner.»

«Our present study is the first to describe the presence of hyperventilation-related hyperlactataemia in an otherwise healthy patient population presenting in the ED in an observational setting.»

«Pco2 being the strongest lactate predictor of the two, as changes in pH during hyperventilation are modulated by changes in breathing rate (and thus Pco2). Our findings are in line with those of previous studies, which showed that intracellular hypocapnia and alkalosis contribute directly to both an increased lactate production and a reduced lactate clearance.18–21»

«However, it should be noted that in patients with critical illnesses, lactate is a risk marker not a risk mediator22: several studies have shown that the administration of exogenous lactate is safe or even beneficial.23 Lactate can be reused directly as a substrate to generate adenosine triphosphate by many organs, including the heart, the brain and the kidneys.24 25»

TABLE 1

Total Pco2≥4.6 Pco2<4.6
n 46 17 29
Sex (% male) 46 41 48
Age (years) 30 (18–77) 26 (18–66) 35 (18–77)
Respiratory rate at triage 25 (20–35) 24 (20–30) 25 (20–35)
Pco2 (kPa) 4.3 (2.0–5.5) 4.9 (4.7–5.5) 3.9 (92.0–4.5)
Lactate level (mmol/l) 1.2 (0.5–4.4) 0.9 (0.5–3.5) 1.4 (0.7–4.4)*
Lactate level >1.5 mmol/l (n) 14 3 11
Base excess 1.4 (−3.2–4.8) 2.1 (−2.7–4.3) 0.6 (−3.2–4.8)*
Potassium (mmol/l) 3.5 (2.8–4.2) 3.8 (3.3–4.0) 3.4 (2.8–4.2)*
HCO3 (mmol/l) 23 (17–27) 26 (21–27) 22 (17–25)
pH 7.47 (7.40–7.68) 7.44 (7.40–7.49) 7.50 (7.42–7.68)
Po2 (kPa) 13.3 (9.3–17.9) 12.9 (10.3–15.6) 13.8 (9.3–17.9)*
Saturation (%) 98 (97–99) 98 (97–99) 98 (97–99)
  • Clinical and biochemical characteristics of the 46 patients as indicated in figure 1 and after stratification for the presence of hypocapnia (Pco2 <4.6). The data are presented as median (range). Statistical comparisons between the normocapnic and hypocapnic subgroups were made by the χ2 test for dichotomous variables and for continuous variables by Mann–Whitney U test.

  • * p<0.05 compared with normocapnic participants.

  • † p<0.001 compared with normocapnic participants.

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