Metabolic and ventilatory rates in newborn kittens during acute hypoxia

Mortola, Jacopo P.; Rezzonico, Rossano

doi:10.1016/0034-5687(88)90127-2

Cited by 56 publications

(25 citation statements)

References 18 publications

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“…The kitten's ventilatory response to acute hypoxia, characterized by rapid and shallow breathing with minimal changes in VE, very closely resembled that previously observed in the same species (5,6,15) and conforms to the breathing pattern response of many other newborn mammals (7). The puppy, on the other hand, responded to 10% O2 with an increase in VT and no changes in f. This species difference could be attributed to the differences in sensitivity to hypoxia (7) as well as differences in the contribution of sleep state to the ventilatory response to hypoxia of newborn dogs and cats (15,16).…”

Section: Ve With No Metabolic Changessupporting

confidence: 77%

“…The finding that, after 30 min of hypoxia, the kitten's V, was stimulated by warming also implies that hypoxia-induced depression of central neuronal activity was not a major contributor to the lack of sustained VE. A similar conclusion was reached by observing that the decrease in VE in hypoxic kittens could be readily reversed by adding C 0 2 to the inspired gas (6,19).…”

Section: Ve With No Metabolic Changessupporting

confidence: 53%

“…The VE-Vc02 ratio was increased in both species during hypoxia; this was previously shown in many newborn species (7), indicating the existence of a hyperventilatory response even in those cases, as in the kittens in our study, in which the absolute value of VE was similar to the normoxic value (7). Previously, it was found that arterial Pco2 decreased in the hypoxic kitten even when the ventilatory level was below the normoxic value (6), which emphasizes the importance of the metabolic adaptation in the acute ventilatory response of the newborn.…”

Section: Ve With No Metabolic Changesmentioning

confidence: 91%

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CO2 Production, Body Temperature, and Ventilation in Hypoxic Newborn Cats and Dogs before and after Body Warming

Pedraz

Mortola

1991

Pediatr Res

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ABSTRACT. Many newborn mammals decrease metabolism and body temperature (Tb) during acute hypoxia. We asked what effects warming of the hypoxic newborn would have on these variables. In unanesthetized newborn cats and dogs, we measured the breathing pattern, C 0 2 production, Tb, and ambient temperature during normoxia at an ambient temperature of 28"C, 30 min of hypoxia (10% 02), and an additional 30 min of hypoxia plus warming. During hypoxia, Tb and COz production decreased in both species, whereas the absolute value of ventilation did not change in kittens and increased in puppies. During hypoxia plus warming, Tb was gradually returned to the normoxic value by increasing ambient temperature by 3 to 4.5OC. This increase did not modify C 0 2 production in either species, and it increased minute ventilation in kittens. We conclude that during hypoxia 1 ) warming the newborn can increase Tb, but not metabolism, to the normoxic value; 2) the decrease in Tb is not a causative prerequisite of the hypoxia-hypometabolism; and 3) an artificial increase in Tb to the normoxic value can stimulate minute ventilation, probably because it is perceived as an hyperthermic stimulus. In many newborn mammals, including infants, metabolic rate and Tb decrease during acute hypoxia (1-7). The mechanisms responsible for these phenomena are not understood, nor is it clear whether the drop in Tb and the metabolic adaptation are linked by a cause-effect relationship. In newborn cats, hypoxia would not lower oxygen consumption if the animals were maintained at about 34"C, which is their normoxic thermoneutral value (8), whereas both Tb and metabolism decrease during hypoxia at 28 to 30°C (2, 5, 6), a range of Ta that is similar to or slightly higher than that experienced in the nest (9). In newborn rats, metabolic rate decreases during hypoxia even at Ta values equivalent to the lower end of their normoxic thermoneutral range (3, 10). One hypothesis, therefore, could be that, in a newborn, even a small hypothermic stress favors the hypometabolic response during hypoxia. If this interpretation were correct, it would follow that in a hypoxic newborn both T b and metabolism could be returned to the normoxic values by means of external body warming.An alternative possibility could be that during hypoxia T b decreases as the result of the hypometabolism and reduced heat production and adjusts to what would represent the normal value for that metabolic conditions, similarly to the mechanism of T b resetting of hibernators (1 1). In such a case, external warming of the hypoxic newborn would act as an hyperthermic challenge, which could raise Tb but not necessarily increase metabolic rate.In these experiments, we attempted to gain some insights into the relationship between body temperature and metabolic rate of the hypoxic newborn by simulating a condition of acute hypoxia in newborn cats and dogs at first maintained at the average Ta of their nest. As expected, we observed a drop in Tb and Vco2. With the animals under continuous hypoxia, we t...

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Section: Ve With No Metabolic Changessupporting

confidence: 77%

Section: Ve With No Metabolic Changessupporting

confidence: 53%

Section: Ve With No Metabolic Changesmentioning

confidence: 91%

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CO2 Production, Body Temperature, and Ventilation in Hypoxic Newborn Cats and Dogs before and after Body Warming

Pedraz

Mortola

1991

Pediatr Res

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“…This finding was supported by studies that showed an association between the decline in ventilation and metabolism in newborn kittens exposed to hypoxia (15). In contrast, Suguihara et al (18) demonstrated in sedated newborn piglets that the decrease in V O 2 at 10 min of hypoxia was independent of whether the ventilatory response to hypoxia was sustained or depressed concluding that the decrease in metabolic rate was not the major cause for the late decline in ventilation.…”

Section: Discussionmentioning

confidence: 84%

“…Therefore, these changes in oxygen delivery and utilization can decrease V O 2 during E. coli endotoxin infusion. This may also influence the ventilatory response to hypoxia during endotoxemia, because metabolic rate and alveolar ventilation are tightly linked (15). To the best of our knowledge, there are no published studies reporting the effect of endotoxemia on the ventilatory response to hypoxia in the newborn.…”

mentioning

confidence: 99%

The Effect of Escherichia coli Endotoxin Infusion on the Ventilatory Response to Hypoxia in Unanesthetized Newborn Piglets

et al. 2003

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To determine the effects of endotoxemia on the neonatal ventilatory response to hypoxia, 17 chronically instrumented and unanesthetized newborn piglets (Յ7 d) were studied before and 30 min after the administration of Escherichia coli O55:B5 endotoxin (n ϭ 8) or normal saline (n ϭ 9). Minute ventilation, oxygen consumption, heart rate, arterial blood pressure, and blood gases were measured during normoxia and 10 min of hypoxia (fraction of inspired oxygen, 0.10). Basal ventilation was not modified by E. coli endotoxin infusion (mean Ϯ SE, 516 Ϯ 49 versus 539 Ϯ 56 mL/min/kg), but the ventilatory response to hypoxia was markedly attenuated at 1 min (955 Ϯ 57 versus 718 Ϯ 97 mL/min/kg, p Ͻ 0.002, saline versus endotoxin) and at 10 min (788 Ϯ 51 versus 624 Ϯ 66 mL/min/kg, p Ͻ 0.002). A larger decrease in oxygen consumption was observed during hypoxia and endotoxemia (6.3 Ϯ 2.8 versus 18.3 Ϯ 2.7%, p Ͻ 0.03, pre-versus post-endotoxin). A significant correlation was demonstrated between the changes in minute ventilation and oxygen consumption with hypoxia during endotoxemia (r ϭ 0.9, p Ͻ 0.002). The ventilatory response to hypoxia was not modified by the saline infusion. These data show a significant attenuation in the ventilatory response to hypoxia during E. coli endotoxemia. This decrease in ventilation was associated with a significant decrease in the metabolic rate during hypoxia and endotoxemia. Changes in the breathing pattern and apnea episodes are frequently associated with neonatal sepsis, especially in the preterm infant (1). It has also been observed that the administration of Escherichia coli endotoxin to anesthetized adult cats produced an abrupt apnea followed by transient rapid and shallow breathing (2). However, the mechanisms explaining these changes in breathing pattern are not clearly understood. Respiratory muscle fatigue, a decrease in lung compliance, and an increase in pulmonary resistance have been cited as possible mechanisms for the ventilatory changes observed during Gram-positive and -negative septicemia (3-6).It is well known that a variety of inflammatory mediators such as cytokines, prostaglandins, leukotrienes, and NO are released during sepsis or endotoxemia (3, 6, 7). Furthermore, the changes in the breathing pattern observed during E. coli infusion to adult cats were eliminated in the animals pretreated with indomethacin or thromboxane A 2 receptor antagonist (2). On the other hand, it has been demonstrated that prostaglandins and NO may mediate the ventilatory depression observed during hypoxia in newborn animals (8, 9). Therefore, the increased release of these inflammatory mediators may further depress the ventilatory response to hypoxia during E. coli endotoxemia.The increased circulating cytokines during sepsis or endotoxemia can induce a systemic inflammatory response involving the microvascular system and trigger hemodynamic changes (7, 10, 11). These changes result in maldistribution of blood flow to different organs, which may be accompanied by January 31, 2002; accepted Dec...

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Adaptations to neonatal anoxia and control of ventilation

Waddell

Fisher

1999

Pediatr. Pulmonol.

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Metabolic and ventilatory rates in newborn kittens during acute hypoxia

Cited by 56 publications

References 18 publications

CO2 Production, Body Temperature, and Ventilation in Hypoxic Newborn Cats and Dogs before and after Body Warming

CO2 Production, Body Temperature, and Ventilation in Hypoxic Newborn Cats and Dogs before and after Body Warming

The Effect of Escherichia coli Endotoxin Infusion on the Ventilatory Response to Hypoxia in Unanesthetized Newborn Piglets

Adaptations to neonatal anoxia and control of ventilation

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