Renal Nerves Are Not Involved in Sodium and Water Retention during Mechanical Ventilation in Awake Dogs

Background: The role of renal nerves during positive end-expiratory pressure ventilation (PEEP) has only been investigated in surgically stressed, anesthetized, unilaterally denervated dogs. Anesthesia, sedation, and surgical stress, however, decrease urine volume and sodium excretion and increase renal sympathetic nerve activity independent of PEEP. This study investigated in awake dogs the participation of renal nerves in mediating volume and water retention during PEEP.

Methods: Eight tracheotomized, trained, awake dogs were used. The protocol consisted of 60 min of spontaneous breathing at a continuous positive airway pressure of 4 cm H2 O, followed by 120 min of controlled mechanical ventilation with a mean PEEP of 15-17 cm H2 O (PEEP), and 60 min of continuous positive airway pressure. Two protocols were performed on intact dogs, in which volume expansion had (hypervolemic; electrolyte solution, 0.5 ml [middle dot] kg-1 [middle dot] min-1) and had not (normovolemic) been instituted. This was repeated on the same dogs 2 or 3 weeks after bilateral renal denervation.

Results: Hypervolemic dogs excreted more sodium and water than did normovolemic dogs. There was no difference between intact and renal-denervated dogs. Arterial pressure did not decrease when continuous positive airway pressure was switched to PEEP. Plasma renin activity, aldosterone, and antidiuretic hormone concentrations were greater in normovolemic dogs. The PEEP increased aldosterone and antidiuretic hormone concentrations only in normovolemic dogs.     

Hemorrhage during isoflurane-nitrous oxide anesthesia: effects of endothelin-A or angiotensin II receptor blockade or both

BACKGROUND: The objective of this study was to determine whether endothelin-A receptor blockade (ETAB) impairs hemodynamic and hormonal regulation compared with controls and angiotensin II receptor blockade (AT1B) during hypotensive hemorrhage in dogs under isoflurane-nitrous oxide anesthesia. METHODS: Six dogs were studied in four protocols: (1) control experiments (controls); (2) ETA blockade using ABT-627 (ETAB); (3) AT1 blockade using losartan (AT1B); and (4) combined AT1B and ETAB (AT1B + ETAB). After a 30-min awake period, isoflurane-nitrous oxide anesthesia was established (1.3 minimum anesthetic concentration). After 60 min of anesthesia, 20 ml blood/kg body weight was withdrawn within 5 min, and the dogs were observed for another hour. Thereafter, the blood was retransfused, and the dogs were observed for a final hour. RESULTS: Anesthesia: Cardiac output decreased in all protocols, whereas mean arterial pressure decreased more in AT1B and AT1B + ETAB than in controls and ETAB. Hemorrhage: After 60 min, cardiac output had decreased less in controls than in all other protocols. Mean arterial pressure decreased more during ETAB than in controls, but most severely during AT1B and AT1B + ETAB. Angiotensin II increased further only in controls and ETAB, whereas vasopressin and catecholamines increased similarly in all protocols. Retransfusion: Mean arterial pressure remained below controls in all protocols but was lowest when the AT1 receptor was blocked. Cardiac output fully recovered in all but the ETAB protocol. CONCLUSIONS: ETAB impairs long-term hemodynamic regulation after hemorrhage and retransfusion during anesthesia despite an activation of vasoconstrictive hormones. This suggests that endothelins have a role in long-term cardiovascular regulation. AT1B impairs both short- and long-term blood pressure regulation during anesthesia and after hemorrhage.     

Hemorrhage during Isoflurane-Nitrous Oxide Anesthesia: Effects of Endothelin-A or Angiotensin II Receptor Blockade or Both

Background: The objective of this study was to determine whether endothelin-A receptor blockade (ETAB) impairs hemodynamic and hormonal regulation compared with controls and angiotensin II receptor blockade (AT1B) during hypotensive hemorrhage in dogs under isoflurane-nitrous oxide anesthesia.

Methods: Six dogs were studied in four protocols: (1) control experiments (controls); (2) ETA blockade using ABT-627 (ETAB); (3) AT1 blockade using losartan (AT1B); and (4) combined AT1B and ETAB (AT1B + ETAB). After a 30-min awake period, isoflurane-nitrous oxide anesthesia was established (1.3 minimum anesthetic concentration). After 60 min of anesthesia, 20 ml blood/kg body weight was withdrawn within 5 min, and the dogs were observed for another hour. Thereafter, the blood was retransfused, and the dogs were observed for a final hour.

Results: Anesthesia: Cardiac output decreased in all protocols, whereas mean arterial pressure decreased more in AT1B and AT1B + ETAB than in controls and ETAB. Hemorrhage: After 60 min, cardiac output had decreased less in controls than in all other protocols. Mean arterial pressure decreased more during ETAB than in controls, but most severely during AT1B and AT1B + ETAB. Angiotensin II increased further only in controls and ETAB, whereas vasopressin and catecholamines increased similarly in all protocols. Retransfusion: Mean arterial pressure remained below controls in all protocols but was lowest when the AT1 receptor was blocked. Cardiac output fully recovered in all but the ETAB protocol.     

The effect of stimulation of the posterior hypothalamus on the electrical activity of the neocortex in chronically premesencephalic cats]

Experiments were carried out on 19 adult cats with chronic brain stem transections at the level of the foremost border of the supperior colliculus. High-frequency electric stimulation of the posterior hypothalamus produced in these cats desynchronization of electrical activity in different parts of the neocortex. A predominant influence from the posterior hypothalamus on the electrical activity of frontal lobes was observed. On the basis of the obtained data, it is suggested that the influences from posterior hypothalamus elicit neocortical activation via thalamic nuclei.     

Laparoscopic Nephrectomy in Patients Undergoing Hemodialysis Treatment

Background and Objectives:

To report our experience with laparoscopic nephrectomy (LN) in patients undergoing hemodialysis compared with normal counterparts.

Methods:

Seventeen patients (20 renal units, Group 1) undergoing hemodialysis underwent LN, which was indicated due to nonfunctioning kidney in 17 and suspected malignancy in 3 renal units. Radical nephrectomy (RN), simple nephrectomy (SN), and simple nephroureterectomy (SNU) were performed in 3, 9, and 8 cases, respectively. For comparison, 101 patients (Group 2) without CRF (chronic renal failure) who had undergone LN were evaluated. In this group, RN, SN, SNU and radical nephroureterectomy (RNU) were performed in 48, 41, 8, and 4 patients, respectively.

Results:

The mean age (36.9±13.1 vs. 48.7±19.4yr, P=0.002) and BMI (22.1±4.8 vs. 26.2±5.1kg/m², P=0.001) were lower in Group 1, whereas ASA (physical status score of American Society of Anesthesiologists) score (2.8±0.4 vs. 1.5±0.7, P<0.001) was lower in Group 2. The estimated blood loss (111±114 vs. 184±335mL, P=0.34) was higher in Group 2. Both groups were comparable in regard to mean operative time (133±79 vs. 119±45, P=0.70), hematocrit drop (4.69±3.9 vs. 3.86±3.0, P=0.29) and hospital stay (3.6±3.3 vs. 3.3±2.4 days, P=0.34). Meanwhile, when only patients undergoing SN and SNU in the study cohort (n=17 in Group 1 and n=49 in Group 2) are taken into consideration, no significant difference was observed between the 2 groups in terms of any kind of above-mentioned perioperative parameters. No case in Group 1 was converted to open surgery due to metabolic problems.

Conclusions:

LN in patients undergoing hemodialysis may be performed safely by an experienced laparoscopy team.