Effect of AT1 receptor blockade on cardiovascular outcome after cardiac arrest: an experimental study in rats

Angiotensin II receptor 1(AT1) antagonists are beneficial in focal ischemia/reperfusion (I/R). However, in cases of global I/R, such as cardiac arrest (CA), AT1 blocker's potential benefits are still unknown. Wistar male rats were allocated into four groups: Control group (CG)-animals submitted to CA by ventricular fibrillation induced by direct electrical stimulation for 3 min, and anoxia for 5 min; Group AT1 (GAT1)-animals subjected to CA and treated with 0.2 mg/kg of candesartan diluted in dimethylsulfoxide (DMSO) (0.1%); Vehicle Group (VG): animals subjected to CA and treated with 0.2 ml/kg of DMSO and Sham group (SG)-animals submitted to surgical interventions, without CA. Cardiopulmonary resuscitation consisted of group medications, chest compressions, ventilation, epinephrine (20 mcg/kg) and defibrillation. The animals were observed up to 4 h after spontaneous circulation (ROSC) return, and survival rates, hemodynamic variables, histopathology, and markers of tissue injury were analyzed. GAT1 group had a higher rate of ROSC (62.5% vs. 42.1%, p < 0.0001), survival (100% vs. 62.5%, p = 0.027), lower incidence of arrhythmia after 10 min of ROSC (10% vs. 62.5%, p = 0.000), and lower neuronal and cardiac injury scores on histology evaluation (p = 0.025 and p = 0.0052, respectively) than GC group. The groups did not differ regarding CA duration, number of adrenaline doses, or number of defibrillations. AT1 receptor blockade with candesartan yielded higher rates of ROSC and survival, in addition to neuronal and myocardial protection.

Computed Tomography Assessment of Tidal Lung Overinflation in Domestic Cats Undergoing Pressure-Controlled Mechanical Ventilation During General Anesthesia

Objective

This study aimed to evaluate lung overinflation at different airway inspiratory pressure levels using computed tomography in cats undergoing general anesthesia.

Study Design

Prospective laboratory study.

Animals

A group of 17 healthy male cats, aged 1.9–4.5 years and weighing 3.5 ± 0.5 kg.

Methods

Seventeen adult male cats were ventilated in pressure-controlled mode with airway pressure stepwise increased from 5 to 15 cmH₂O in 2 cmH₂O steps every 5 min and then stepwise decreased. The respiratory rate was set at 15 movements per min and end-expiratory pressure at zero (ZEEP). After 5 min in each inspiratory pressure step, a 4 s inspiratory pause was performed to obtain a thoracic juxta-diaphragmatic single slice helical CT image and to collect respiratory mechanics data and an arterial blood sample. Lung parenchyma aeration was defined as overinflated, normally-aerated, poorly-aerated, and non-aerated according to the CT attenuation number (−1,000 to −900 HU, −900 to −500 HU, −500 to −100 HU, and −100 to +100 HU, respectively).

Result

At 5 cmH₂O airway pressure, tidal volume was 6.7± 2.2 ml kg⁻¹, 2.1% (0.3–6.3%) of the pulmonary parenchyma was overinflated and 84.9% (77.6%−87.6%) was normally inflated. Increases in airway pressure were associated with progressive distention of the lung parenchyma. At 15 cmH₂O airway pressure, tidal volume increased to 31.5± 9.9 ml kg⁻¹ (p < 0.001), overinflated pulmonary parenchyma increased to 28.4% (21.2–30.6%) (p < 0.001), while normally inflated parenchyma decreased 57.9% (53.4–62.8%) (p < 0.001). Tidal volume and overinflated lung fraction returned to baseline when airway pressure was decreased. A progressive decrease was observed in arterial carbon dioxide partial pressure (PaCO₂) and end-tidal carbon dioxide (ETCO₂) when the airway pressures were increased above 9 cmH₂O (p < 0.001). The increase in airway pressure promoted an elevation in pH (p < 0.001).

Conclusions and Clinical Relevance

Ventilation with 5 and 7 cmH₂O of airway pressure prevents overinflation in healthy cats with highly compliant chest walls, despite presenting acidemia by respiratory acidosis. This fact can be controlled by increasing or decreasing respiratory rate and inspiratory time.

Cyclooxygenases 1 and 2 inhibition and analgesic efficacy of dipyrone at different doses or meloxicam in cats after ovariohysterectomy

OBJECTIVE

To evaluate the cyclooxygenases (COX) inhibition, adverse effects and analgesic efficacy of dipyrone or meloxicam in cats undergoing elective ovariohysterectomy.

STUDY DESIGN

Prospective, blinded, randomized, clinical study.

ANIMALS

A total of 30 healthy young cats.

METHODS

The cats were randomly assigned to three postoperative groups: D25 (dipyrone 25 mg kg^-1 every 24 hours), D12.5 (dipyrone 12.5 mg kg^-1 every 12 hours) and M (meloxicam 0.1 mg kg^-1 every 24 hours). In the first 24 hours, the drugs were administered intravenously (IV), and then orally for 6 (dipyrone) or 3 days (meloxicam). Prostanoids thromboxane B₂ and prostaglandin E₂ concentrations served as indicators of COX activity and, with physiological variables and pain and sedation scores, were measured for 24 hours after first analgesic administration. Rescue analgesia (tramadol, 2 mg kg^-1 IV) was provided if Glasgow feline composite measure pain scale (CMPS-Feline) ≥5. Laboratory tests included symmetric dimethylarginine and adverse effects were evaluated regularly up to 7 and 10 days after surgery, respectively. Parametric and nonparametric data were analyzed with two-way anova and Kruskal-Wallis tests, respectively (p < 0.05).

RESULTS

In the first half hour after analgesic administration, COX-1 activity was close to zero and remained significantly lower than before drug administration for 24 hours in all groups. The inhibition of COX-2 activity was significant for 30 minutes in all groups and up to 4 hours in group M. No alterations in laboratory tests or significant adverse effects were observed. Pain scores and need for rescue analgesia did not differ statistically among groups.

CONCLUSIONS

Dipyrone at both doses and meloxicam provided a nonselective inhibition of COX-1 and -2 activities and effective analgesia without causing significant adverse effects or laboratory tests alterations.

CLINICAL RELEVANCE

Dipyrone at both doses provides equally effective analgesia without causing adverse effects in cats undergoing ovariohysterectomy.

Ultrasound-guided continuous block of median and ulnar nerves in horses: development of the technique

OBJECTIVE

To develop a technique for ultrasound-guided continuous median and ulnar peripheral nerve block in horses.

STUDY DESIGN

Anatomical and prospective experimental study.

ANIMALS

A total of 16 thoracic limbs from horse cadavers and 18 adult horses.

METHOD

This study was conducted in three phases. Phase 1: Dissection of median and ulnar nerves in the antebrachial region of two cadaver limbs to identify localizing landmarks. Description of sonoanatomy in 14 cadaver limbs using ultrasound-guided perineural infiltration of a combination of cellulose gel (5 mL), contrast medium (4 mL) and methylene blue (1 mL). Catheters were inserted between the perineural sheath and epineurium in six limbs, followed by computed tomography. Phase 2: Ultrasonographic images of the limbs of 18 healthy horses of different breeds were used to define an acoustic window and optimize the approach to nerves. Phase 3: Two case reports of horses with chronic pain of different etiologies. Catheters were inserted between the epineurium and paraneural sheath of the median and/or ulnar nerves guided by ultrasound, followed by continuous infusion of 0.4% ropivacaine.

RESULTS

Information from phase 1 was used to direct needle insertion, solution dispersion and catheter implantation in phase 2, which resulted in 100% technique accuracy. In response to the peripheral nerve block, pain reduction was apparent in the two clinical cases by increased weight bearing in affected limbs and decreased requirement for systemic analgesic medications. No local reactions were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

The ultrasound technique allowed real-time visualization of needle, catheter and drug dispersion and resulted in a high success rate for nerve blocks. The horses administered a median and ulnar nerve block exhibited no discomfort or signs of infection at the catheter insertion site. Further studies are warranted to validate the efficacy of this technique.

Comparison of pulse pressure variation versus echocardiography-derived stroke volume variation for prediction of fluid responsiveness in mechanically ventilated anesthetized dogs

OBJECTIVE

To evaluate the ability and accuracy of aortic flow velocity-time integral variation (ΔVTI) and peak aortic velocity variation (ΔVpeak) compared with pulse pressure variation (PPV) to predict fluid responsiveness in mechanically ventilated dogs.

STUDY DESIGN

Prospective clinical study.

ANIMALS

A group of 50 mechanically ventilated dogs with spontaneous hypotension during orthopedic or oncologic surgery.

METHODS

Investigations were performed in the surgery room. When mean arterial pressure (MAP) decreased to <65 mmHg, measurements were performed before and after a fluid challenge (lactated Ringer's solution 5 mL kg^-1 over 15 minutes). Responders were defined as a change in stroke volume (SV; transesophageal Doppler) ≥15%. Data were analyzed using paired/unpaired t test or Mann-Whitney/Wilcoxon test when appropriate and receiver operating characteristics (ROC) curves; a p value <0.05 was considered statistically significant.

RESULTS

After the fluid challenge, 35 (70%) of 50 dogs were responders with significant increases in SV and decreases in PPV; 15 dogs were nonresponders. ΔVTI and ΔVpeak correlated with a 15% increase in SV. The optimum cut-off value for PPV was 15.6% (sensitivity, 88%; specificity, 100%), for ΔVTI was 10.65% (sensitivity, 65%; specificity, 100%) and for ΔVpeak was 10.15% (sensitivity, 80%; specificity, 100%). The area under the ROC curve for PPV was (0.93 ± 0.08) and for ΔVpeak was (0.89 ± 0.09), before fluid challenge. The gray zone area spread from 6.15% to 15.6% for PPV (18 dogs), 2.45% to 10.65% for ΔVTI (22 dogs) and 0.6% to 10.15% for ΔVpeak (25 dogs).

CONCLUSIONS

When using mechanical ventilation, ΔVTI and ΔVpeak predicted fluid responsiveness with the same ability as PPV, based on the area under the ROC curve analysis. However, PPV showed great accuracy demonstrated by a narrower gray zone that included fewer individuals.

CLINICAL RELEVANCE

ΔVTI and ΔVpeak can be used as indices of fluid responsiveness in anesthetized dogs.

Pulse pressure variation as a guide for volume expansion in dogs undergoing orthopedic surgery

OBJECTIVE

To investigate whether pulse pressure variation (PPV) can predict fluid responsiveness in healthy dogs during clinical surgery.

STUDY DESIGN

Prospective clinical study.

ANIMALS

Thirty-three isoflurane-anesthetized dogs with arterial hypotension during orthopedic surgery.

METHODS

Fluid challenge with lactated Ringer's solution (15 mL kg^-1 in 15 minutes) was administered in mechanically ventilated dogs (tidal volume 10 mL kg^-1) with hypotension [mean arterial pressure (MAP) < 65 mmHg]. The volume expansion was considered effective if cardiac output (CO; transesophageal Doppler) increased by ≥ 15%. Cardiopulmonary data were analyzed using two-way ANOVA, receiver operating characteristics (ROC) curves and Spearman coefficient; p < 0.05 was considered significant.

RESULTS

Effective volume expansion, mean ± standard deviation 42 ± 4% increase in CO (p < 0.0001) was observed in 76% of the dogs, resulting in a decrease in PPV (p < 0.0001) and increase in MAP (p < 0.0001), central venous pressure (CVP; p = 0.02) and ejection fraction (p < 0.0001) compared with before the fluid challenge. None of these changes occurred when volume expansion resulted in a nonsignificant CO increase of 4 ± 5%. No significant differences were observed in blood gas analysis between responsive and nonresponsive dogs. The increase in CO was correlated with the decrease in PPV (r = -0.65; p < 0.0001) but absolute values of CO and PPV were not correlated. The PPV performance (ROC curve area: 0.89 ± 0.06, p = 0.0011) was better than that of CVP (ROC curve area: 0.54 ± 0.12) and MAP (ROC curve area: 0.59 ± 0.13) to predict fluid responsiveness. The best cut-off for PPV to distinguish responders and nonresponders was 15% (50% sensitivity and 96% specificity).

CONCLUSIONS AND CLINICAL RELEVANCE

In mechanically ventilated, healthy, isoflurane-anesthetized dogs, PPV predicted fluid responsiveness to volume expansion, and MAP and CVP did not show such applicability.

Normal values of b-wave responses of full-field electroretinogram in Lhasa Apso dogs with cataracts according to age

Lhasa Apso dogs with immature, mature or hypermature cataracts were divided into four groups according to their age (G1: 1 to 3 years old, G2: 4 to 7 years old, G3: 8 to 11 years old, G4: more than 12 years old). All animals were evaluated under the same sedation protocol to allow the performance of the electroretinogram (ERG) exam to determine normal value of b-wave response of the full-field ERG according to age. Three ERG responses were recorded: rod, maximal and cone responses. The amplitude values and b-wave implicit time of the responses of all groups were compared and analyzed by Kruskal-Wallis test (variance analysis for non-repeated measures), followed by the Dunn post-test (when p<0,05). A significant decrease was observed in maximal responses' amplitude, when comparing the G4 group with G1 and G2. No statistically relevant differences were observed in the b-wave implicit time values between groups. The ERG values are directly influenced by the animal's age. Older patients presented a decrease in the amplitude of the maximal response. The study determined the normal parameters of ERG b-waves for Lhasa Apso dogs with cataract according to their age group.

Evaluation of the effects of methadone and tramadol on postoperative analgesia and serum interleukin-6 in dogs undergoing orthopaedic surgery

BACKGROUND

Acute postsurgical pain is of great interest due to potential risk of becoming chronic if not treated properly, worsening patient's recovery and quality of life. Twenty-eight dogs with ruptured cruciate ligaments were divided into three groups that received intramuscular injections of 4 mg/kg of tramadol (TRA), 0.5 mg/kg of methadone (MET0.5), or 0.7 mg/kg of methadone (MET0.7). Physiological parameters (heart and respiratory rates and blood pressure) were evaluated at specified times: baseline (TBL), 1 (T1), 2 (T2), 4 (T4), 6 (T6), and 24 (T24) hours after premedication. Pain scores were described by visual analogue scale (VAS), modified Glasgow Composite, and Colorado University Acute Pain scales. Blood samples for measurement of interleukin (IL)-6 were collected at TBL, T1, T6, and T24. This was a prospective, randomised investigation to evaluate the efficacy of tramadol and methadone as premedications in dogs undergoing osteotomies.

RESULTS

There were no statistically significant differences between groups with respect to age, weight, gender, surgery time, and time to extubation. Heart rate, respiratory rate, and blood pressure values were maintained within acceptable ranges, and a reduction was observed at T2 in MET0.5 and MET0.7 compared with TBL. Increases in VAS scores were observed in TRA at T4 compared with TBL, T1, and T24 and between T1 and T6 (p < 0.001). In MET0.5, there was significant increase in VAS score at T4 compared with T1 (p < 0.001). TRA and MET0.5 showed significantly higher mean ± SD VAS scores (3.4 ± 2.5 and 2.5 ± 2.6, respectively) than MET0.7 (1.1 ± 1.5) at T4 (p < 0.001). TRA showed greater demand of rescue analgesia (four animals in T4 and two in T6) (p < 0.037). There were no statistically significant differences in sedation scores, Colorado Scale scores, or interleukin levels between groups and time points.

CONCLUSIONS

Methadone given as premedication in doses of 0.7 mg/kg was better at controlling pain compared with lower doses and tramadol. However, dosage increases, administered as rescue analgesia, promoted adequate pain control even in tramadol group. Influence of these analgesics on IL-6 release could not be demonstrated, but significant levels were not found.

Effect of pressure support ventilation during weaning on ventilation and oxygenation indices in healthy horses recovering from general anesthesia

OBJECTIVE

To determine if pressure support ventilation (PSV) weaning from general anesthesia affects ventilation or oxygenation in horses.

STUDY DESIGN

Prospective randomized clinical study.

ANIMALS

Twenty client-owned healthy horses aged 5 ± 2 years, weighing 456 ± 90 kg.

METHODS

In the control group (CG; n = 10) weaning was performed by a gradual decrease in respiratory rate (fR ) and in the PSV group (PSVG; n = 10) by a gradual decrease in fR with PSV. The effect of weaning was considered suboptimal if PaCO2 > 50 mmHg, arterial pH < 7.35 plus PaCO2 > 50 mmHg or PaO2 < 60 mmHg were observed at any time after disconnection from the ventilator until 30 minutes after the horse stood. Threshold values for each index were established and the predictive power of these values was tested.

RESULTS

Pressure support ventilation group (PSVG) had (mean ± SD) pH 7.36 ± 0.02 and PaCO2 41 ± 3 mmHg at weaning and the average lowest PaO2 69 ± 6 mmHg was observed 15 minutes post weaning. The CG had pH 7.32 ± 0.02 and PaCO2 57 ± 6 mmHg at weaning and the average lowest PaO2 48 ± 5 mmHg at 15 minutes post weaning. No accuracy in predicting weaning effect was observed for fR (p = 0.3474), minute volume (p = 0.1153), SaO2 (p = 0.1737) and PaO2 /PAO2 (p = 0.1529). A high accuracy in predicting an optimal effect of weaning was observed for VT > 10 L (p = 0.0001), fR /VT ratio ≤ 0.60 breaths minute(-1) L(-1) (p = 0.0001), VT /bodyweight > 18.5 mL kg(-1) (p = 0.0001) and PaO2 /FiO2 > 298 (p = 0.0002) at weaning. A high accuracy in predicting a suboptimal effect of weaning was observed for VT < 10 L (p = 0.0001), fR /VT ratio ≥ 0.60 breaths minute(-1) L(-1) (p = 0.0001) and Pe'CO2 ≥ 38 mmHg (p = 0.0001) at weaning.

CONCLUSIONS AND CLINICAL RELEVANCE

Pressure support ventilation (PSV) weaning had a better respiratory outcome. A higher VT , VT /body weight, PaO2 /FiO2 ratio and a lower fR /VT ratio and Pe'CO2 were accurate in predicting the effect of weaning in healthy horses recovering from general anesthesia.

Comparison of Epidural and Systemic Tramadol for Analgesia Following Ovariohysterectomy

The objective of the study was to compare epidural and systemic tramadol for postoperative analgesia in bitches undergoing ovariohysterectomy. Twenty animals, randomly divided into two groups, received either epidural (EPI) or intramuscular (IM) tramadol (2 mg/kg) 30 min before anesthetic induction. Analgesia, sedation, cardiorespiratory parameters, end-tidal isoflurane, blood catecholamines and cortisol, and arterial blood gases were measured at different time points up to 24 hr after agent administration. There were no differences between the two groups regarding cardiorespiratory parameters, end-tidal isoflurane, and pain scores. Two dogs in the IM and one in the EPI group required supplemental analgesia. Cortisol was increased (P&lt;0.05) at 120 min (3.59 μg/dL and 3.27μg/dL in the IM and EPI groups, respectively) and 240 min (2.45 μg/dL and 2.54μg/dL in the IM and EPI groups, respectively) compared to baseline. Norepinephrine was also increased (P&lt;0.05) at 120 min in both groups compared to baseline values. Epinephrine values were higher (P&lt;0.05) in the IM group compared with the EPI group at 50 min, 120 min, and 1,440 min after tramadol administration. Epidural tramadol is a safe analgesic, but does not appear to have improved analgesic effects compared with IM administration.

Use of pulse pressure variation to estimate changes in preload during experimental acute normovolemic hemodilution

BACKGROUND

Acute normovolemic hemodilution (ANH) is an alternative to blood transfusion in surgeries involving blood loss. This experimental study was designed to evaluate whether pulse pressure variation (PPV) would be an adequate tool for monitoring changes in preload during ANH, as assessed by transesophageal echocardiography.

METHODS

Twenty-one anesthetized and mechanically ventilated pigs were randomized into three groups: CTL (control), HES (hemodilution with 6% hydroxyethyl starch at a 1:1 ratio) or NS (hemodilution with saline 0.9% at a 3:1 ratio). Hemodilution was performed in animals of groups NS and HES in two stages, with target hematocrits 22% and 15%, achieved at 30-minute intervals. After two hours, 50% of the blood volume withdrawn was transfused and animals were monitored for another hour. Statistical analysis was based on ANOVA for repeated measures followed by multiple comparison test (P<0.05). Pearson's correlations were performed between changes in left ventricular end-diastolic volume (LVEDV) and PPV, central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP).

RESULTS

Group NS received a significantly greater amount of fluids during ANH (NS, 900 ± 168 mL vs. HES, 200 ± 50 mL, P<0.05) and presented greater urine output (NS, 2643 ± 1097 mL vs. HES, 641 ± 338 mL, P<0.001). Significant decreases in LVEDV were observed in group NS from completion of ANH until transfusion. In group HES, only increases in LVEDV were observed, at the end of ANH and at transfusion. Such changes in LVEDV (∆LVEDV) were better reflected by changes in PPV (∆PPV, R=-0.62) than changes in CVP (∆CVP, R=0.32) or in PAOP (∆PAOP, R=0.42, respectively).

CONCLUSION

Changes in preload during ANH were detected by changes in PPV. ∆PPV was superior to ∆PAOP and ∆CVP to this end.

Comparison of the effects of tramadol, codeine, and ketoprofen alone or in combination on postoperative pain and on concentrations of blood glucose, serum cortisol, and serum interleukin-6 in dogs undergoing maxillectomy or mandibulectomy

OBJECTIVE

To compare analgesic effects of tramadol, codeine, and ketoprofen administered alone and in combination and their effects on concentrations of blood glucose, serum cortisol, and serum interleukin (IL)-6 in dogs undergoing maxillectomy or mandibulectomy.

ANIMALS

42 dogs with oral neoplasms.

PROCEDURES

30 minutes before the end of surgery, dogs received SC injections of tramadol (2 mg/kg), codeine (2 mg/kg), ketoprofen (2 mg/kg), tramadol+ketoprofen, or codeine+ketoprofen (at the aforementioned dosages). Physiologic variables, analgesia, and sedation were measured before (baseline) and 1, 2, 3, 4, 5, and 24 hours after surgery. Blood glucose, serum cortisol, and serum IL-6 concentrations were measured 1, 3, 5, and 24 hours after administration of analgesics.

RESULTS

All treatments provided adequate postoperative analgesia. Significant increases in mean+/-SD blood glucose concentrations were detected in dogs receiving tramadol (96+/-14 mg/dL), codeine (120+/-66 mg/dL and 96+/-21 mg/dL), ketoprofen (105+/-22 mg/dL), and codeine+ketoprofen (104+/-16 mg/dL) at 5, 1 and 3, 5, and 3 hours after analgesic administration, respectively, compared with preoperative (baseline) values. There were no significant changes in physiologic variables, serum IL-6 concentrations, or serum cortisol concentrations. Dogs administered codeine+ketoprofen had light but significant sedation at 4, 5, and 24 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

Opioids alone or in combination with an NSAID promoted analgesia without adverse effects during the 24-hour postoperative period in dogs undergoing maxillectomy or mandibulectomy for removal of oral neoplasms.

Minimum alveolar concentrations and hemodynamic effects of two different preparations of sevoflurane in pigs

BACKGROUND

Original sevoflurane (Sevo A) is made with water, while a generic sevoflurane (Sevocris) is produced with propylene glycol as a stabilizing additive. We investigated whether the original and generic sevoflurane preparations differed in terms of their minimum alveolar concentration (MAC) values and hemodynamic effects.

METHODS

Sixteen pigs weighing 31.6+/-1.8 kg were randomly assigned to the Sevo A or Sevocris groups. After anesthesia induction via mask with the appropriate sevoflurane preparation (6% in 100% oxygen), the MAC was determined for each animal. Hemodynamic and oxygenation parameters were measured at 0.5 MAC, 1 MAC and 1.5 MAC. Histopathological analyses of lung parenchyma were performed.

RESULTS

The MAC in the Sevo A group was 4.4+/-0.5%, and the MAC in the Sevocris group was 4.1+/-0.7%. Hemodynamic and metabolic parameters presented significant differences in a dose-dependent pattern as expected, but they did not differ between groups. Cardiac indices and arterial pressures decreased in both groups when the sevoflurane concentration increased from 0.5 to 1 and 1.5 MAC. The oxygen delivery index (DO(2)I) decreased significantly at 1.5 MAC.

CONCLUSION

Propylene glycol as an additive for sevoflurane seems to be as safe as a water additive, at least in terms of hemodynamic and pulmonary effects.

Hemodynamic effects of PEEP in a porcine model of HCl-induced mild acute lung injury

BACKGROUND

Positive end-expiratory pressure (PEEP) and sustained inspiratory insufflations (SI) during acute lung injury (ALI) are suggested to improve oxygenation and respiratory mechanics. We aimed to investigate the hemodynamic effects of PEEP with and without alveolar recruiting maneuver in a mild ALI model induced by inhalation of hydrochloric acid.

METHODS

Thirty-two pigs were randomly allocated into four groups (Control-PEEP, Control-SI, ALI-PEEP and ALI-SI). ALI was induced by intratracheal instillation of hydrochloric acid. PEEP values were progressively increased and decreased from 5, 10, 15 and 20 cmH2O in all groups. Three SIs maneuvers of 30 cmH2O for 20 s were applied to the assignable groups between each PEEP level. Transesophageal echocardiography (TEE), global hemodynamics, oxygenation indexes and gastric tonometry were measured 5 min after the maneuvers had been concluded and at each established value of PEEP (5, 10, 15 and 20 cmH2O).

RESULTS

The cardiac index, ejection fraction and end-diastolic volume of right ventricle were significantly (P < 0.001) decreased with PEEP in both Control and ALI groups. Left ventricle echocardiography showed a significant decrease in end-diastolic volume at 20 cmH2O of PEEP (P < 0.001). SIs did not exert any significant hemodynamic effects either early (after 5 min) or late (after 3 h).

CONCLUSIONS

In a mild ALI model induced by inhalation of hydrochloric acid, significant hemodynamic impairment characterized by cardiac function deterioration occurred during PEEP increment, but SI, probably due to low applied values (30 cmH2O), did not exert further negative hemodynamic effects. PEEP should be used cautiously in ALI caused by acid gastric content inhalation.

Total intravenous anaesthesia with propofol-racemic ketamine and propofol-S-ketamine: a comparative study and haemodynamic evaluation in dogs undergoing ovariohysterectomy

Total intravenous anaesthesia (TIVA) with propofol and ketamine proved to be very satisfactory from a clinical point of view. This blind randomised controlled trial was designed to compare induction and maintenance of anaesthesia under continuous infusion of propofol-racemic ketamine (PRK) with that of propofol-S-ketamine (PSK) and evaluate their haemodynamic, metabolic and ventilatory effects. Seven female dogs undergoing ovariohysterectomy were involved in each group. Anaesthesia was induced: in Group PRK, with propofol (4.0mg kg-1) and racemic ketamine (2.0mg kg-1) intravenous (i.v.), followed by i.v. infusion of propofol (initial dose of 0.5mg kg-1 min-1) and racemic ketamine (0.2mg kg-1 min-1); in Group PSK, with propofol (4.0mg kg-1) and S-ketamine (1.0 mg kg¹) i.v., followed by i.v. infusion of propofol (initial dose of 0.5mg kg-1 min-1) and S-ketamine (0.1mg kg-1 min-1). Parameters were assessed before anaesthesia and in 6 time points after induction. In both groups, heart rate increased significantly at all time points. There was a slight decrease in systemic blood pressure, cardiac output and cardiac index in both groups. The systolic index decrease significantly and intense respiratory depression was observed in all groups, making assisted ventilation necessary.

Blood-gas and electrolyte values for Amazon parrots (Amazona aestiva)

The aim was to provide reference data for blood gas/acid-base status and electrolytes for non-anesthetized Amazon parrots (Amazona aestiva). Thirty-five adult parrots from Tietê ecologic park were utilized. Arterial blood (0.3ml) samples were anaerobically collected from the superficial ulnar artery in heparinized (sodium heparin) 1-ml plastic syringes. The samples were immediately analyzed through a portable analyzer (i-STAT*, Abbot, Illinois, USA) with cartridges (EG7+). These data were grouped in such a way as to present both mean and standard deviation: body weight (360±37g), respiratory rate (82±33 b/m), temperature (41.8±0.6°C), hydrogen potential (7.452±0.048), carbon dioxide partial pressure (22.1±4.0mmHg), oxygen partial pressure (98.1±7.6mmHg), base excess (-7.9±3.1), plasma concentration of bicarbonate ions (14.8±2.8mmol/L), oxygen saturation (96.2±1.1%), plasma concentration of sodium (147.4±2.2mmol/L), plasma concentration of potassium (3.5±0.53mmol/L), plasma concentration of calcium (0.8±0.28mmol/L), hematocrit (38.7±6.2%) and concentration of hemoglobin (13.2±2.1g/dl). This study led us to conclude that, although the results obtained showed hypocapnia and low values of bicarbonate and base excess, when compared to other avian species, these data are very similar. Besides, in spite of the equipment being approved only for human beings, it was considered simple and very useful in the analysis of avian blood samples. By using this equipment we were able to provide references data for non-anaesthetized Amazon parrots.

Pulmonary function is better preserved in pigs when acute normovolemic hemodilution is achieved with hydroxyethyl starch versus lactated Ringer's solution

Acute normovolemic hemodilution (ANH) has been proposed to decrease the need for allogenic blood transfusion. Consequently, great amounts of fluids are necessary to maintain hemodynamics during and after blood removal. The aim of this experiment was to evaluate the oxygenation, respiratory compliance, and lung structure during ANH performed with lactated Ringer's solution and hydroxyethyl starch (HES). Gas exchange, extravascular lung water, intrathoracic blood volume, serum osmolality, respiratory mechanics, and optical and electronic microscopy of lung biopsies were evaluated. Animals were randomized into three groups: CTL (control, n = 9), HES (HES 6% 200/0.5, n = 9), and LR (lactated Ringer's solution, n = 9). Animals in groups HES and LR underwent ANH to reach a preestablished hematocrit of around 15%. The removed blood was replaced with HES in a proportion of 1:1 and with lactated Ringer's solution 3:1. The LR group demonstrated a tendency for a marked time-dependence decrease in compliance (P = 0.013 in T2; P = 0.008 in T3) and in Pao2/fraction of inspired oxygen (Fio2) ratio (P = 0.033 in T2) as well as an increase in (A-a) Grad O2 (P = 0.037 in T2). Extravascular lung water and intrathoracic blood volume did not present any significant variation among the groups. In contrast, serum osmolality presented a significant decline in animals hemodiluted with lactated Ringer's solution. Optical and electronic microscopy of lungs biopsies revealed moderate to serious collapses and basement membrane enlargement in LR group. In this kind of experimental model, ANH with 6% HES (200/0.5) seems to preserve lung structure better as evidenced by maintenance of oxygenation indexes and respiratory compliance when compared with that in the Ringer's solution hemodiluted group.

Hydroxyethyl starch is superior to lactated Ringer as a replacement fluid in a pig model of acute normovolaemic haemodilution

BACKGROUND

Tissue tolerance to oxygen privation during acute normovolaemic haemodilution with different fluids remains unclear. We tested the hypothesis that hydroxyethyl starch (HES) is superior to lactated Ringer's solution in pigs for preserving tissue perfusion during acute normovolaemic haemodilution.

METHODS

Twenty-four animals were randomized into control, lactated Ringer's solution and HES groups. All groups, except the control, underwent acute normovolaemic haemodilution. Haemodynamics, oxygen parameter indices, global anaerobic metabolic markers, echocardiographic parameters, gastric tonometry and serum osmolarity were monitored at baseline, immediately after (0 min) and 60 and 120 min after the end of haemodilution. Myocardial, liver, stomach and intestine samples were collected for further evaluation.

RESULTS

Cardiac and oxygen parameter index responses to acute normovolaemic haemodilution were comparable. However, the increment in cardiac index, stroke volume index, and left ventricular stroke work index were more sustained in the starch group. In the lactated Ringer's group, gastric pH decreased significantly and was accompanied by a significant increase in lactate. Myocardial ultrastructure was better preserved in the starch group. The other tissue samples presented no change.

CONCLUSIONS

In this model of ANH, the starch group had a superior haemodynamic response. Minor loss of myocardial cellular integrity and preserved gastric pHi reinforce these findings.

Comparison between intermittent and continuous measurement of cardiac output after acute normovolemic hemodilution in pigs

Continuous cardiac output (CO) and mixed venous oxygen saturation (SvO2) determined through the pulmonary artery catheter may be helpful in monitoring hemodynamic conditions in critically ill patients. This study aimed to evaluate CO and SvO2 in a model of acute normovolemic hemodilution (ANH), analyzing the accuracy of the continuous versus intermittent method for CO and SvO2 measurement in pigs. Twenty-three pigs were enrolled to three groups: control, ANH with 6% hydroxyethyl starch (HES), or ANH with lactated Ringer's (LR) solution. After hemodilution, we showed that SvO2 was reduced in both groups, mainly in LR animals (P < 0.05). Regarding the evaluation of CO, we showed an increase in both groups submitted to ANH (P < 0.05). Through Bland-Altman analysis, we showed that the continuous CO catheter presented lower values than the intermittent method after hemodilution, mainly with HES (P < 0.001), and there was no difference in the measurement of SvO2. The ANH promoted a decrease in SvO2 and an increase in CO values, mainly in animals submitted to hemodilution with HES. The use of continuous and intermittent (laboratory) measurement of SvO2 showed clinical applicability and good agreement, an effect not reproduced by the CO measurement. New studies are needed to further investigate the agreement between the continuous and intermittent methods for the measurement of CO in adverse hemodynamic conditions such as ANH.