Double-dose cefuroxime concentrations in bone, synovial fluid of the knee joint and subcutaneous adipose tissue-A randomised porcine microdialysis study

This study evaluated target tissue concentrations of double dose cefuroxime administered intravenously as either one 15 min infusion of 3000 mg (Group 1) or two single 15 min infusions of 1500 mg administered 4 h apart (Group 2). Sixteen pigs were randomised into two groups of eight. Cortical and cancellous bone, synovial fluid of the knee joint and subcutaneous adipose tissue concentrations were measured based on sampling via microdialysis. Plasma samples were collected as a reference. Comparison of the groups was based on time with concentrations above relevant minimal inhibitory concentrations (fT>MIC) of 4 μg/mL. The mean time fT>MIC (4 μg/mL) across compartments was longer for Group 2 (280-394 min) than for Group 1 (207-253 min) (p<0.01). Cortical bone showed a tendency towards longer fT>MIC (4 μg/mL) in Group 2 (280 min) than in Group 1 (207 min) (p = 0.053). Within 50 min after administration, the mean concentration of 4 μg/mL was reached in all compartments for both groups. The mean concentrations decreased below 4 μg/mL after approximately 4 h (Group 1) and 3 h (Group 2) from initiation of administration (time zero). During an 8 h interval, double-dose cefuroxime administered as 2 × 1500 mg with a 4 h interval provides longer time above MIC breakpoint for Staphylococcus aureus (4 μg/mL) than a single bolus of 3000 mg cefuroxime. To maintain sufficient tissue concentrations during longer surgeries, re-administration of cefuroxime (1500 mg) should be considered 3 h after the first administration.

Hypoxia - Reoxygenation in neonatal cardiac arrest: Results from experimental models

In this review, we summarize the results of studies that investigated the effects of hypoxia and reoxygenation in cardiac arrest, including the use of different fractions of inspired oxygen, in neonatal animals. The studies were heterogenous in terms of anaesthetic regimens, and definitions of cardiac arrest and circulatory recovery. Cardiopulmonary resuscitation with 100% oxygen increased oxidative stress in maturing rats. Studies in fetal/neonatal lambs and post-transitional neonatal piglets indicate no consistent differences between ventilation with 21% vs. 100% oxygen with regards to recovery times, oxygen damage or adverse events. If 21% oxygen is as effective as 100% oxygen in newborn infants with cardiac arrest requiring chest compression, the use of 21% instead of 100% oxygen could reduce morbidity and mortality in asphyxiated infants. Unanswered questions include what is the most optimal cerebral oxygen delivery during reperfusion, as well as oxygenation targets after return of spontaneous circulation.

Quantification of porcine myocardial perfusion with modified dual bolus MRI - a prospective study with a PET reference

BACKGROUND

The reliable quantification of myocardial blood flow (MBF) with MRI, necessitates the correction of errors in arterial input function (AIF) caused by the T1 saturation effect. The aim of this study was to compare MBF determined by a traditional dual bolus method against a modified dual bolus approach and to evaluate both methods against PET in a porcine model of myocardial ischemia.

METHODS

Local myocardial ischemia was induced in five pigs, which were subsequently examined with contrast enhanced MRI (gadoteric acid) and PET (O-15 water). In the determination of MBF, the initial high concentration AIF was corrected using the ratio of low and high contrast AIF areas, normalized according to the corresponding heart rates. MBF was determined from the MRI, during stress and at rest, using the dual bolus and the modified dual bolus methods in 24 segments of the myocardium (total of 240 segments, five pigs in stress and rest). Due to image artifacts and technical problems 53% of the segments had to be rejected from further analyses. These two estimates were later compared against respective rest and stress PET-based MBF measurements.

RESULTS

Values of MBF were determined for 112/240 regions. Correlations for MBF between the modified dual bolus method and PET was r_s = 0.84, and between the traditional dual bolus method and PET r_s = 0.79. The intraclass correlation was very good (ICC = 0.85) between the modified dual bolus method and PET, but poor between the traditional dual bolus method and PET (ICC = 0.07).

CONCLUSIONS

The modified dual bolus method showed a better agreement with PET than the traditional dual bolus method. The modified dual bolus method was found to be more reliable than the traditional dual bolus method, especially when there was variation in the heart rate. However, the difference between the MBF values estimated with either of the two MRI-based dual-bolus methods and those estimated with the gold-standard PET method were statistically significant.

Efficacy of buprenorphine for management of surgical castration pain in piglets

Background

Surgical castration is a painful procedure, performed routinely on commercial pig farms to prevent boar taint and reduce aggression. The objectives of this study were to assess the efficacy of 0.04 mg/kg buprenorphine (BUP) in reducing pain in castrated piglets, using behavioral indicators and vocalization analysis. This study also sought to further validate the Piglet Grimace Scale (PGS) as a pain assessment tool.

A pilot study first assessed the safety of BUP or 0.2 mg/kg butorphanol administration to piglets (n = 4 per treatment). When no side effects were noted with BUP, ten litters of 5-day old piglets (n = 60 total, 15 per treatment group) were used, and randomly assigned to one of four possible treatments: BUP (castrated or uncastrated), saline, or sham. Treatments were administered as an intramuscular injection 20 min prior to surgical castration. Piglets were video recorded 1 h pre-procedure, post-castration for 8 h and for another hour, 24 h post-procedure. Behaviors were scored continuously for the first 15 min of each hour and 511 still-images of piglet faces were scored using the PGS. Vocalizations were recorded from each piglet at three points in the study: at initial handling, injection, and castration.

Results

Butorphanol caused some piglets to become groggy and vomit and was not further evaluated. BUP-castrated piglets demonstrated significantly fewer pain behaviors and less facial grimacing compared to saline-treated pigs (P < 0.0001 and P = 0.0073, respectively). There was no difference between the pain behaviours displayed by BUP-castrated piglets compared to BUP-uncastrated and sham piglets (P = 0.9986 and P = 0.7484). There was also no difference in PGS score between BUP-castrated and BUP-uncastrated piglets (P = 0.9376). Piglets in the BUP-castrated group produced vocalizations of similar frequency, amplitude, power, and energy to saline-treated piglets.

Conclusions

Buprenorphine was highly effective in alleviating castration-associated pain behaviors and facial grimacing in piglets, without causing any obvious side effects. Its administration did not reduce piglet vocalizations at the time of castration. The PGS corresponded well to piglet pain behaviors and has utility as a pain assessment tool.

Comparison of TIVA and Desflurane Added to a Subanaesthetic Dose of Propofol in Patients Undergoing Coronary Artery Bypass Surgery: Evaluation of Haemodynamic and Stress Hormone Changes

Introduction. Increased levels of stress hormones are associated with mortality in patients undergoing coronary artery bypass grafting (CABG). Aim. To compare total intravenous anaesthesia (TIVA) and desflurane added to a subanaesthetic dose of propofol. Material and Methods. Fifty patients were enrolled in this study. Fentanyl (3-5 mcg/kg/h) was started in both groups. Patients were divided into two groups. The PD group (n = 25) received 1 minimum alveolar concentration (MAC) desflurane anaesthesia in addition to propofol infusion (2-3 mg/kg/h), while P group (n = 25) received propofol infusion (5-6 mg/kg/h) only. Biochemical data, cortisol, and insulin levels were measured preoperatively (T0), after initiation of CPB but before cross-clamping the aorta (T1), after removal of the cross-clamp (T2), and at the 24th postoperative hour (T3). Results. Systolic, diastolic, and mean arterial pressure levels were significantly higher in PD group than those in P group in T1 and T2 measurements (p ≤ 0.05). CK-MB showed a significant decrease in group P (p ≤ 0.05). When we compared both groups, cortisol levels were significantly higher in PD group than P group (p ≤ 0.05). Conclusion. Stress and haemodynamic responses were better controlled using TIVA than desflurane inhalation added to a subanaesthetic dose of propofol in patients undergoing CABG.

Interference of angiotensin II and enalapril with hepatic blood flow regulation

Acute reduction of portal vein blood flow (Qpv) increases hepatic arterial perfusion (Qha) [the hepatic arterial buffer response (HABR)]. Angiotensin II (AT-II) reduces Qpv, but its effect on HABR is not known. We explored interactions of AT-II and enalapril with hepatic blood flow regulation. Twenty healthy anesthetized pigs were randomized to receive AT-II (n = 8) from 5 to 61 ng/kg per min, enalapril (n = 8) from 3 to 24 μg/kg per h, or saline (n = 4). HABR was assessed by occluding portal vein and expressed as 1) ratio between changes in Qha and Qpv, 2) hepatic arterial conductance (Cha). AT-II infusion increased mean arterial blood pressure from 74 (66-77) mmHg to 116 (109-130) mmHg (median, IQR; P < 0.0001) and decreased cardiac output, Qpv, and renal artery flow (-24%, -28% and -45%, respectively). The fraction of cardiac output of Qha, carotid, and femoral flows increased. With enalapril, blood pressure decreased, whereas cardiac output was maintained with flow redistribution favoring hepatic and renal arteries. In AT-II group, dQha/dQpv increased from 0.06 (0.03, 0.17) to 0.24 (0.13, 0.31) (P = 0.002), but Cha during acute portal vein occlusion decreased from 4.3 (1.6, 6.6) to 2.9 (1.2, 3.7) ml/mmHg (P = 0.003). Both variables remained unchanged in the enalapril group and in controls. AT-II infusion reduces portal flow in parallel with cardiac output and induces a dose-dependent redistribution of flow, favoring brain, hepatic artery, and peripheral tissues at the expense of renal perfusion. During HABR, AT-II decreases Cha but increases Qha compensation, likely as result of increased hepatic arterial perfusion pressure. Enalapril had no effect on HABR.

Evaluation of the hypnotic and hemodynamic effects of dexmedetomidine on propofol-sedated swine

This study examined the sedative effect of, and hemodynamic response to dexmedetomidine administration in propofol-sedated swine. Sixteen swine were subjects. After anesthetic induction and preparation, the propofol infusion rate was adjusted to maintain a bispectral index (BIS) value between 55 and 65 (i.e., baseline). With the propofol infusion rate fixed at the baseline rate, dexmedetomidine was infused continuously at a rate of 0.2, 0.4, and 0.7 microg.kg(-1).h(-1) for one hour at each rate. The BIS value and hemodynamic parameters were recorded at each step. Dexmedetomidine decreased the BIS value, mean arterial blood pressure, heart rate, cardiac output, and mixed venous oxygen saturation in a dose-dependent manner. The systemic vascular resistance (SVR) did not change, but the pulmonary vascular resistance (PVR) increased. Oxygen delivery (DO(2)) and oxygen consumption (VO(2)) decreased. A small dose of dexmedetomidine (0.2 microg.kg(-1).h(-1)) greatly enhanced the sedative effects of propofol with only small changes in hemodynamics and systemic oxygen balance, suggesting it may be useful in reducing the propofol dose requirement. However, dexmedetomidine 0.4 microg.kg(-1).h (-1) suppressed cardiac contractility, and 0.7 microg.kg(-1).h(-1) induced hemodynamic instability and further systemic oxygen imbalance while the additional sedative effect was limited. A lower dose of dexmedetomidine may be recommended when using it in combination with propofol.