Effects of diuretic-induced hypovolemia/isosmotic dehydration on cardiorespiratory responses to hyperthermia and its physical treatment in rabbits

Figures & data

Table I.  Respiratory and cardiovascular variables before and after induction of hypovolemia by administration of furosemide.

	Before administration of furosemide	After administration of furosemide
BT (°C)	38	38
Hct (%)	43.0 ± 2.0	48.0 ± 2.0*
[Na^+] (mmol l^−1)	123.0 ± 2.0	121.0 ± 3.0
VE (ml min^−1)	921.5 ± 92.1	1029.3 ± 108.1*
f (breaths min^−1)	86.0 ± 9.0	95.0 ± 8.0
VT (ml)	11.0 ± 1.1	10.8 ± 0.6
PaO2 (kPa)	15.1 ± 1.2	14.4 ± 0.7
PaCO2 (kPa)	2.9 ± 0.3	2.6 ± 0.4
pH	7.398 ± 0.022	7.367 ± 0.020
ETCO2 (kPa)	4.0 ± 0.3	3.6 ± 0.3*
HR (beats min^−1)	190.0 ± 16.0	248.0 ± 11.0*
MAP (kPa)	7.5 ± 0.7	7.1 ± 0.4
SBF (U)	56.3 ± 6.1	40.9 ± 8.1*
MBF (ml min^−1)	90.7 ± 7.1	75.7 ± 7.1*
RBF (ml min^−1)	15.6 ± 1.0	11.5 ± 1.5*

Values are mean ± SEM. *Significantly different from the same variable before administration of furosemide. BT, body temperature; Hct, hematocrit; [Na⁺], sodium concentration; V_E, minute ventilation; f, frequency of breathing; V_T, tidal volume; Pa_O2, partial pressure of oxygen in arterial blood; Pa_CO2, partial pressure of carbon dioxide in arterial blood; ET_CO2, end-tidal carbon dioxide; HR, heart rate; MAP, mean arterial pressure; SBF, skin blood flow; MBF, mesenteric blood flow; RBF, renal blood flow.

Figure 1. Changes in minute ventilation (V_E) during hyperthermia and its physical treatment in the normovolemic (solid line) and hypovolemic (dashed line) groups. Each point represents mean ± SEM. *p < 0.05 significantly different from the normovolemic group at the same body temperature. 38a: initial level of animal body temperature after induction of hypovolemia/isosmotic dehydration.

Table II.  Respiratory and cardiovascular effects of hyperthermia and its physical treatment in normovolemic (NV) and hypovolemic (HV) groups.

	NV group			HV group
BT (°C)	38	42	38 (after Th)	38	42	38 (after Th)
Hct (%)	41.0 ± 1.0	44.0 ± 2.0	43.0 ± 1.0	48.0 ± 2.0	49.0 ± 3.0	49.0 ± 2.0
VE (ml min^−1)	765.7 ± 70.0	1006.6 ± 70.0*	1230.9 ± 103.1	1029.3 ± 108.1	1756.7 ± 251.1*	1279.2 ± 165.3†
f (breaths min^−1)	83.0 ± 6.0	192.0 ± 23.0*	95.0 ± 8.0†	95.0 ± 8.0	134.0 ± 9.0*	79.0 ± 5.0†
VT (ml)	9.3 ± 0.6	5.4 ± 0.7*	14.2 ± 2.2†	10.8 ± 0.6	13.4 ± 2.0	16.2 ± 1.7
PaO2 (kPa)	14.4 ± 0.9	12.2 ± 0.4*	16.3 ± 0.6†	14.4 ± 0.7	11.7 ± 0.9*	16.1 ± 2.3†
PaCO2 (kPa)	3.5 ± 0.3	2.4 ± 0.2*	1.7 ± 0.1†	2.6 ± 0.4	2.0 ± 0.3	1.9 ± 0.3
pH	7.425 ± 0.019	7.396 ± 0.024	7.387 ± 0.030	7.367 ± 0.020	7.320 ± 0.023	7.252 ± 0.035†
ETCO2 (kPa)	3.5 ± 0.1	2.3 ± 0.1*	2.1 ± 0.1	3.6 ± 0.3	2.1 ± 0.2*	2.3 ± 0.3†
HR (beats min^−1)	233.0 ± 11.0	329.0 ± 14.0*	253.0 ± 9.0†	248.0 ± 11.0	326.0 ± 18.0*	256.0 ± 7.0†
MAP (kPa)	7.9 ± 0.5	7.1 ± 0.6	7.7 ± 0.4	7.1 ± 0.4	8.7 ± 1.0	7.7 ± 0.8
SBF (U)	35.5 ± 5.9	113.4 ± 21.0*	32.7 ± 3.1†	40.9 ± 8.1	113.7 ± 14.9*	25.9 ± 5.5†
MBF (ml min^−1)	84.6 ± 8.9	34.4 ± 3.9*	86.0 ± 8.3†	75.7 ± 7.1	53.4 ± 2.5*	66.7 ± 4.9†
RBF (ml min^−1)	18.6 ± 2.5	7.7 ± 0.8*	11.3 ± 0.5†	11.5 ± 1.5	7.6 ± 1.2*	10.3 ± 1.9†

Values are mean ± SEM. *Significantly different from normothermic value (38°C) in respective group (shown in preceding column). †Significantly different from hyperthermic value (at 42°C) in respective group (shown in preceding column). BT, body temperature; Hct, hematocrit; V_E, minute ventilation; f, frequency of breathing; V_T, tidal volume; Pa_O2, partial pressure of oxygen in arterial blood; Pa_CO2, partial pressure of carbon dioxide in arterial blood; ET_CO2, end-tidal carbon dioxide; HR, heart rate; MAP, mean arterial pressure; SBF, skin blood flow; MBF, mesenteric blood flow; RBF, renal blood flow.

Figure 2. Changes in frequency of breathing (f) during body surface heating and cooling in the normovolemic (solid line) and hypovolemic (dashed line) groups. Each point represents mean ± SEM. *p < 0.05 significantly different from the normovolemic group at the same body temperature. 38a: initial level of animal body temperature after induction of hypovolemia/isosmotic dehydration.

Figure 3. Changes in tidal volume (V_T) during overheating to 42°C and during body temperature recovery in the normovolemic (solid line) and hypovolemic (dashed line) groups. Each point represents mean ± SEM. *p < 0.05 significantly different from the normovolemic group at the same body temperature. 38a: initial level of animal body temperature after induction of hypovolemia/isosmotic dehydration.

Figure 4. Changes in ear skin blood flow (SBF), as laser Doppler flowmetry during hyperthermia and its physical treatment in the normovolemic (NV) and hypovolemic (HV) groups. Each point represents mean ± SEM.

Figure 5. Changes in mesenteric blood flow (MBF) during body surface heating and cooling in the normovolemic (NV) and hypovolemic (HV) groups. Each point represents mean ± SEM. *p < 0.05 significantly different from the normovolemic group at the same body temperature.

Figure 6. Changes in renal blood flow (RBF) during hyperthermia and its physical treatment in the normovolemic (NV) and hypovolemic (HV) groups. Each point represents mean ± SEM.