Monitoring of fluid absorption with nitrous oxide during transurethral resection of the prostate.

BACKGROUND: The fluid absorption that occurs during transurethral resection of the prostate (TURP) can be indicated and quantified by the ethanol method. Recently, nitrous oxide (N(2)O) was tested in animals and volunteers and seemed to be more accurate and safe. The present study compared these two methods in surgical patients. METHODS: Eighty-six TURPs were performed at two hospitals using an irrigating fluid that contained 3% mannitol, 1% ethanol and 0.004% N(2)O (40 ml/l). The ethanol concentration was measured by end-expiratory tests every 10 min. The N(2)O concentration was measured by a flared nasal cannula every second. Fluid absorption was calculated based on a regression equation (ethanol method) from the area under the curve based on the samples where CO(2) >median (N(2)O method). RESULTS: Thirteen patients (15%) absorbed >300 ml of fluid as indicated by the ethanol method. The median volume was 707 ml (range 367-1422). Ethanol yielded higher figures for fluid absorption up to 700-800 ml, whereafter the N(2)O method indicated that the absorption was larger. Over the entire range, the mean difference between the two methods at the end of any 10-min period of TURP was only +45 ml, although the 95% limits of agreement were quite separated (-479 to +569 ml). CONCLUSIONS: The N(2)O method does not require forced breath sampling and was successfully apply clinically. However, there was a dose-dependent difference in result between the ethanol and N(2)O methods, which markedly separated the limits of agreement for a wider range of fluid absorption events.

Short-term crystalloid fluid resuscitation in uncontrolled intra-abdominal bleeding in swine.

INTRODUCTION: Fluid therapy in uncontrolled bleeding is controversial. In a previously used experimental animal model of aortic injury, the outcome often was impaired by re-bleeding that began at least 20 minutes after crystalloid fluid resuscitation was initiated. Therefore, it was hypothesized that re-bleeding might be avoided if volume loading is carried out for 20 minutes and then discontinued. METHODS: Ten minutes after a 5 mm laceration was produced in the infra-renal aorta on eight anesthetized pigs, they received a 20-minute intravenous infusion of Ringer's solution in the ratio of 1:1 to the expected blood loss. Hemodynamics were studied for 120 minutes using arterial and pulmonary artery catheters and blood flow probes placed proximal and distal to the aortic lesion and around the left renal artery and portal vein. RESULTS: The bleeding stopped between three and four minutes after the onset of bleeding. The blood flow rate dropped to 38% (mean) of baseline in the splanchnic region, to 31% in the upper aorta, and to 13% in the kidney. The flow rates and the oxygen consumption increased transiently during fluid resuscitation, but never reached baseline levels. Re-bleeding amounted to about 15% of the initial bleeding and occurred in only three of the animals. Four of the pigs died of shock within 90 minutes (range 47-85 minutes) after the aortic injury. CONCLUSION: Short-term crystalloid fluid therapy in uncontrolled aortic hemorrhage transiently improved the hemodynamic status and the oxygen consumption following the initial bleeding. Furthermore, the infusion did not cause re-bleeding of more than 100 ml, which occurred in previously conducted experiments when the infusion was continued for more than 20 minutes.

Nitric oxide increases cutaneous and respiratory heat dissipation in conscious rabbits.

The influence of systemic nitric oxide (NO) donor infusion and NO synthase inhibition on major thermoregulatory mechanisms was investigated under thermoneutral conditions (24 degrees C) in the conscious rabbit. Both low (25 nmol.min-1.kg-1) and high-dose (75 nmol.min-1.kg-1) infusion of the NO donors 3-morpholinosydnonimine-hydrochloride and S-nitroso-N-acetylpenicillamine augmented respiratory heat dissipation due to raised respiratory frequency (RF) and evaporative water loss (REWL). At the higher dose of NO donor, RF and REWL increased (from 107 +/- 16 to 156 +/- 19 breaths/min and from 7.12 +/- 0.97 to 11.29 +/- 1.29 mg.min-1.kg-1; P < 0.05), and, combined with a moderate rise in cutaneous heat dissipation (ear skin temperature increased from 29.03 +/- 1.76 to 33.29 +/- 2.71 degrees C; P < 0.05), deep body temperature was slightly reduced (-0.1 degrees C, P > 0.05) without a change in metabolic heat production. In contrast, blockade of endogenous NO synthesis induced a sustained rise in body temperature (0.2 degrees C, P < 0.05), concomitant with a reduction in both RF and REWL (from 131 +/- 11 to 94 +/- 12 breaths/min and from 10.86 +/- 1.14 to 8.70 +/- 0.88 mg.min-1.kg-1, P < 0.05), whereas metabolic heat production decreased slightly and cutaneous heat dissipation was minimally altered. The data indicate that, under thermoneutral conditions, systemically applied NO primarily influences body temperature in the conscious rabbit by modulating the rate of respiratory heat dissipation, whereas the roles of cutaneous heat dissipation and metabolic heat production are relatively minor.