Direct Measurement Of Arterial Pressure Research Articles

A Retrospective Comparative Study of the Frequency of Hypotension in Pediatric Cardiac Catheterization under General Anesthesia: Remimazolam versus Sevoflurane

ObjectiveTo compare the incidence of hypotension between remimazolam and sevoflurane under general anesthesia for cardiac catheterization of congenital heart disease. DesignRetrospective observational study. SettingA single university hospital with 300 pediatric cardiac catheterizations by general anesthesia performed annually. ParticipantsPatients younger than 15 years who underwent cardiac catheterization under general anesthesia between March 1, 2021, and December 31, 2022. Exclusion criteria: general anesthesia maintained with other than remimazolam or sevoflurane, the administration of remifentanil, ASA score of 4–5, emergency procedures, and no direct arterial pressure measurement. InterventionsGeneral anesthesia was maintained with remimazolam or sevoflurane. Measurements and Main Results309 patients were analyzed, 28 in the remimazolam group and 281 in the sevoflurane group. Propensity score matching adjusted for confounding factors resulted in 28 patients in each arm, with no apparent differences in background factors. Hypotension was defined as a time-averaged area of systolic arterial pressure falling below 80% of the baseline from the start of anesthesia to the end of procedure that was > 1. Significance level: p < 0.05. The incidence of hypotension was 39.3% in the Remimazolam and 46.4% in the Sevoflurane with no significant difference (p=0.79), although the ratio of median systolic arterial pressure to the baseline was significantly higher in the Remimazolam: 91.4 (SD: 15.2)% vs 83.2 (SD: 11.4)% in the Sevoflurane (p=0.03). ConclusionsRemimazolam did not result in lower hypotension incidence than sevoflurane during pediatric cardiac catheterization for congenital heart disease, while maintaining significantly higher blood pressure overall.

Effects of maternal protein restriction on central and peripheral renin-angiotensin systems in male rat offspring

AimsWe investigated the involvement of the renin angiotensin system (RAS) on the cardiorespiratory control in rats from dams fed with a low-protein diet. Main methodsMale offspring were obtained from dams fed a normoprotein diet (NP, 17% casein) and low-protein diet (LP, 8% casein) during pregnancy and lactation. Direct measurements of arterial pressure (AP), heart rate (HR) and respiratory frequency (RF) were recorded in awake 90-day-old at resting and after losartan potassium through either intracerebroventricular (ICV) microinjections or intravenous (IV) administration. Cardiovascular variability was evaluated by spectral analysis. Peripheral chemoreflex sensitivity was assessed through the potassium cyanide (KCN; 40 μg/0.1 ml/rat, IV). Gene expression was evaluated by qPCR, and MAPK (Mitogen Activated Protein Kinase) expression was evaluated by western blot. Key findingsThe LP offspring had higher mean AP (MAP) and RF than NP offspring. In the spectral analysis, the LP rats also showed higher low frequency of systolic AP (NP: 2.7 ± 0.3 vs. LP: 5.0 ± 1.0 mmHg). After ICV losartan, MAP and RF in LP rats remained higher than those in NP rats, but without changes in HR. The peripheral chemoreflex was similar between the groups. LP group had lower gene expression of Rac1 (Ras-related C3 botulinum toxin substrate 1) (NP: 1.13 ± 0.06 vs. LP: 0.88 ± 0.08). Peripherally, LP rats had larger delta of MAP after IV losartan (NP: −9.8 ± 2 vs. LP: −23 ± 6 mmHg), without changes in HR and RF. SignificanceIn rats, the RAS participates peripherally, but not centrally, in the maintenance of arterial hypertension in male offspring induced by maternal protein restriction.

Enhancement of excitatory transmission in NTS neurons projecting to ventral medulla of rats exposed to sustained hypoxia is blunted by minocycline.

Rats subjected to sustained hypoxia (SH) present increases in arterial pressure (AP) and in glutamatergic transmission in the nucleus tractus solitarius (NTS) neurons sending projections to ventrolateral medulla (VLM). Treatment with minocycline, a microglial inhibitor, attenuated the increase in AP in response to SH. The increase in the amplitude of glutamatergic postsynaptic currents in the NTS-VLM neurons, induced by postsynaptic mechanisms, was blunted by minocycline treatment. The number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS of minocycline-treated rats. The data show that microglial recruitment/proliferation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the observed increase in AP. Short-term sustained hypoxia (SH) produces significant autonomic and respiratory adjustments and triggers activation of microglia, the resident immune cells in the brain. SH also enhances glutamatergic neurotransmission in the NTS. Here we evaluated the role of microglial activation induced by SH on the cardiovascular changes and mainly on glutamatergic neurotransmission in NTS neurons sending projections to the ventrolateral medulla (NTS-VLM), using a microglia inhibitor (minocycline). Direct measurement of arterial pressure (AP) in freely moving rats showed that SH (24h, fraction of inspired oxygen ( ) 0.1) in vehicle and minocycline (30mg/kg i.p. for 3days)-treated groups produced a significant increase in AP in relation to control groups under normoxic conditions, but this increase was significantly lower in minocycline-treated rats. Whole-cell patch-clamp recordings revealed that the active properties of the membrane were comparable among the groups. Nevertheless, the amplitudes of glutamatergic postsynaptic currents, evoked by tractus solitarius stimulation, were increased in NTS-VLM neurons of SH rats. Changes in asynchronous glutamatergic currents indicated that the observed increase in amplitude was due to postsynaptic mechanisms. These changes were blunted in the SH group previously treated with minocycline. Using immunofluorescence, we found that the number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS neurons of minocycline-treated rats. Our data support the concept that microglial activation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the increase in AP observed in this experimental model.

Liberating carotid arteries: measuring arterial pressure through femoral artery in mice

ABSTRACTResearches involving arterial pressure measurements in mice have primarily relied on carotid arterial catheterization. However, in some circumstances, measuring arterial pressure through the carotid arterial impairs accuracy. This study was aimed to evaluate whether femoral artery could displace carotid artery for the blood pressure (BP) measurements in mice. Fifty-six Swiss mice (n = 14 in each group) were randomized into four groups: control, left femoral artery, right femoral artery, and union group, in which BP was measured through left carotid, left femoral, right femoral artery, and simultaneously from right femoral artery and left carotid artery, respectively. Arterial pressure was recorded for 5 min after catheterization. There was no significant difference of the success rate and mortality rate among four groups (P > 0.05), and no obvious difference (P > 0.05) of catheterization time among the first three groups. For intergroup comparison of arterial pressure, there was no significant difference (P > 0.05) of the systolic blood pressure (SBP), diastolic BP, mean arterial pressure, and pulse pressure among the first three groups. For intragroup comparison, SBP, diastolic blood pressure (DBP), mean arterial pressure (MAP) monitored from right femoral artery were similar (P > 0.05) with those from left carotid artery, with significantly positive correlation. The mean values of difference of SBP, DBP, and MAP were −1.3, 1.2, and 0.5 mmHg, respectively. Our results indicated that femoral artery catheterization could be a safe, feasible, reliable, and accuracy alternative for the direct measurement of arterial pressure in anesthesia mice.

Abstract P239: Toll-Like Receptors 9 (TLR9) Play a Key Role in Cardiac and Vascular Dysfunction Associated With 2-Kydney 1-Clip (2K1C) Hypertension in Mice

Introduction: Renovascular hypertension is the leading cause of secondary hypertension and is also involved in the physiopathogenesis of resistant hypertension. The activation of toll-like receptors 9 (TLR9) was demonstrated to contribute to the increase in arterial pressure (AP) in spontaneously hypertensive rats. We hypothesize that the TLR9 are also activated in two-kidney one- clip (2K1C) hypertensive mice, eliciting cardiac and vascular dysfunction; therefore, contributing to the increase in AP. Methods and Results: C57BL (WT) and TLR9 knockout (TLR9_KO) mice were anesthetized with isoflurane and submitted to 2K1C hypertension by placing a silver clip (0.12 mm) around the left renal artery. After 4 weeks, the cardiac function of mice was evaluated by echocardiography in anesthetized subjects. Following, the direct AP measurement was carried out and the third-order mesenteric resistance arteries (MRA) were removed for vascular function evaluation. All data were compared to Sham-operated WT mice. The AP was remarkably elevated in 2K1C WT mice (133±2 vs 93 ± 4 mmHg), whereas this increase was partially prevented by the absence of the TLR9 (114±5 mmHg). 2K1C hypertension caused cardiac dysfunction in WT mice, displaying decreased ejection fraction (42.6±3.1 vs 52.7±1.5%), fractional shortening (10.1±0.7 vs 13.7±0.9%), stroke volume (25.9±2.2 vs 37.9±1.9 μL) and cardiac output (9.2±0.8 vs 14.6±0.8 mL/min); however, the 2K1K hypertension did not affect the cardiac function in TLR9_KO mice: ejection fraction (54.5±1.6%), fractional shortening (14.5±1.1%), stroke volume (43.4±4.6 μL) and cardiac output (15.2±1.6 mL/min). Vascular dysfunction, characterized by increased contractile response to phenylephrine (Emax: 167.2±2.2 vs 125.9±3.5%) and reduced relaxation to acetylcholine (Emax: 69.3±1.6 vs 87.6±1.4%) and sodium nitroprusside (pD2: 7.3±0.07 vs 7.9±0.05), was observed in 2K1C WT mice, but not in 2K1C TLR9_KO mice (Emax: 127.7±2.9%, 88.5±2.0% and pD2: 7.78±0.06, to phenylephrine, acetylcholine and sodium nitroprusside). Conclusions: TLR9 is involved in both cardiac and vascular dysfunctions of 2K1C mice and also in the increase of AP of this experimental model.

Acute Aortic Regurgitation And The Autonomic Modulation To The Heart

Aortic regurgitation (AR) produces a volume overload to the heart. Acute AR determines poor prognostic, and its main cause is infective endocarditis. The role of autonomic participation on this situation is still missing. We studied hemodynamic parameters, autonomic modulation, heart rate (HR) variability and baroreflex sensibility (BRS) in acute AR rats.Male Wistar rats (250‐280g) were undergone to sham or AR surgery. Following one week the rats received a catheter into the femoral artery (direct measurements of arterial pressure, AP), and another into the jugular vein (drug administration). Intrinsic HR (IHR) was evaluated after simultaneous blockade with atenolol (6 mg/kg) and atropine (3 mg/kg). The sympathetic tonus (ST) and vagal tonus (VT) were obtained from IHR minus the maximum HR after atropine and the lowest HR after atenolol, respectively. Overall variability of HR in the time domain and BRS were calculated from basal recordings. Diastolic pressure was lower in AR rats(70 ± 6 vs sham 99 ± 5 mmHg). There were no changes for IHR, ST, VT or HR variability. Acute AR impaired BRS (1,10 ± 0,11 vs sham 1,61 ± 0,14 ms/mmHg). The results show that acute AR does not altered autonomic modulation to the heart, although it produces a decrease in the BRS, this import mechanism is dismished in onset sustained volume overload to the heart. Financial support: FAPESP 2013/00742‐7

Maternal low-protein diet induces changes in the cardiovascular autonomic modulation in male rat offspring

Background and aimsMaternal undernutrition induces development of the arterial hypertension. We investigated the effects of a maternal low-protein diet on cardiovascular autonomic control in the offspring. Methods and resultsMale Wistar rats were divided into two groups according to the diets of their mothers during gestation and lactation: the control (normal protein, NP, 17% casein; n = 14) and low-protein (LP, 8% casein; n = 14) groups. Direct measurements of arterial pressure (AP) were recorded from wakeful 90-day-old male offspring. The LP offspring presented higher mean AP than did the NP rats (NP: 93 ± 4 vs. LP: 113 ± 2 mmHg; p < 0.05), whereas the heart rate (HR) was similar in the two groups. In the spectral analysis, the LP group showed higher power at low (NP: 1.98 ± 0.25 vs. LP: 3.7 ± 0.3 mmHg²; p < 0.05) and high (NP: 1.28 ± 0.18 vs. LP: 2.13 ± 0.42 mmHg²; p < 0.05) frequencies of systolic arterial pressure (SAP). In the pulse interval, the LP group presented an increase in the LF/HF ratio (NP: 0.32 vs. LP: 0.56; p < 0.05). After propranolol (4 mg/kg, intravenous (iv)), the bradycardia was higher in the LP group (NP: −36 ± 8 vs. LP: −94 ± 12 bpm; p < 0.05), after methylatropine (2 mg/kg, iv), the tachycardia was similar to NP group. After administration of the ganglionic blocker (hexamethonium; 25 mg/kg, iv), the LP animals showed larger delta variation in the AP (NP: −33.7 ± 5 vs. LP: −53.6 ± 4 mmHg; p < 0.05). ConclusionThe rats subjected to protein malnutrition presented an increase in the cardiovascular sympathetic tone, which contributed to the elevated AP observed in these animals.

Evaluation of the cardiovascular changes in juvenile and adult female rats submitted to chronic intermittent hypoxia (680.3)

Chronic intermittent hypoxia (CIH) induces hypertension in juvenile and adult male rats due to an increase in sympathetic activity. There is experimental evidence that changes in respiratory network are driving the sympathetic overactivity in this model. Female rats are more resistant to the development of hypertension in several experimental models. In this study, we evaluated the cardiovascular changes in juvenile and adult female rats in response to CIH. Juvenile female rats were exposed to CIH for a 10 days protocol and adult female rats to a 35 days protocol and at the end of the protocols direct measurements of arterial pressure were performed in control and CIH rats. Juvenile female rats exposed to CIH (n=30) presented significant increase in arterial pressure compared to their respective control [n=34 (94±1 vs 86±1 mmHg, p&lt;0.05)], as well adult female rats exposed to CIH (n=27) when compared to their respective control [n=26 (111±1 vs 104±1 mmHg, p&lt;0.05)]. We concluded that juvenile and adult female rats submitted to CIH develop high arterial pressure similarly to male rats after CIH, suggesting that sexual characteristics and hormones are not playing a protective role in this experimental model of hypertension.Grant Funding Source: Supported by CAPES, CNPQ and FAPESP

The proportion of clinically relevant alarms decreases as patient clinical severity decreases in intensive care units: a pilot study

ObjectivesTo determine (1) the proportion and number of clinically relevant alarms based on the type of monitoring device; (2) whether patient clinical severity, based on the sequential organ failure assessment...

Lisinopril Indifferently Improves Heart Rate Variability During Day and Night Periods in Spontaneously Hypertensive Rats

The aim of this work was to investigate the effect of 10 weeks of lisinopril treatment to spontaneously hypertensive rats (SHRs) on day/night variations of blood pressure, heart rate and autonomic cardio-regulation parameters. Male SHR with surgically implanted radio-telemetry implant that provided direct measurements of arterial pressure and electrocardiogram wave were used. Animals were allocated to two groups (n=5 each). The first group was treated with lisinopril (20 mg/kg by gavage) daily for 10 weeks (treated group); whereas the second was gavaged daily with tap water (untreated group). Arterial blood pressure, ECG and other telemetry parameters were recorded at the start and at the end of 10-week treatment. Collected data were analyzed using specialized software and were statistically tested. In addition to the expected lowering of blood pressure, spectral analysis of R-R intervals revealed that lisinopril treatment for 10 weeks significantly caused 2-3 fold increase in heart rate variability (HRV) during both active and inactive periods. However, R-R interval durations demonstrated variable distribution patterns during those periods. The cause of observed distribution pattern of R-R intervals during active and inactive periods may be of significance to better understand HRV changes and warrants further investigations.

Evaluation of the oscillometric technique for intermittent non-invasive arterial blood pressure measurement in the anaesthetized pig

This study was designed to evaluate the oscillometric technique for intermittent non-invasive measurement of arterial pressure (AP) in the anaesthetized pig. In six pigs under sevoflurane anaesthesia, intermittent (every 2 minutes) oscillometric measurements of AP made at a forelimb (FL), a hindlimb (HL) and the tail base were compared with simultaneous direct AP measurements made at the aortic arch (AA) over a wide pressure range (30-140 mmHg of mean AP). All oscillometric measurements strongly correlated (Pearson correlation coefficient >0.837, P < 0.001) with direct AP measurements, with those made at the FL exhibiting the highest correlation. On the basis of consistency of difference between oscillometric and AA pressure readings at graded pressure levels, measurements made at the tail base provided reliable prediction of systolic AP, at the FL of diastolic AP and at both the tail base and the FL of mean AP. In conclusion, oscillometric measurements at the FL and the tail base offer reliable prediction of AP in the anaesthetized pig.

Is the pleth variability index a surrogate for pulse pressure variation in a pediatric population undergoing spine fusion?

To compare simultaneous measurements of pulse pressure variation (PPV) and pleth variability index (PVI) in patients undergoing spinal fusion. To determine if PVI can be used as a surrogate for PPV and also the influence of the prone position on these measurements. Spine fusion is an involved surgical procedure requiring attention to fluid administration. Dynamic indices for assessing fluid responsiveness like PPV have proven useful to guide fluid administration. Plethysmographic waveform variation like PVI is an appealing surrogate for measurements like PPV that require invasive arterial pressure measurement. Spine fusion patients are unique and the potential of either PPV or PVI to guide fluid therapy has not been studied. Patients undergoing spine fusion for scoliosis were studied. In addition to the usual monitors including direct arterial pressure measurement, a multi-wavelength pulse co-oximeter was applied to measure PVI. Paired measurements of PPV and PVI were obtained and limits of agreement determined using the method of Bland and Altman. PPV and PVI in prone and supine positions were compared by paired t-test. The bias between PVI and PPV measurements was -0.56% with 95% limits of agreement of +21.67% to -20.55%. There was no significant difference between the prone and supine measurements at the P = 0.05 level (Table 1). Our data indicate that PVI is not a surrogate for PPV. PVI measurements were not influenced by changing from the supine to prone position and therefore may prove useful for patients undergoing spine surgery.

Evaluation of indirect blood pressure monitoring in awake and anesthetized red-tailed hawks (Buteo jamaicensis): effects of cuff size, cuff placement, and monitoring equipment

ObjectiveTo compare Doppler and oscillometric methods of indirect arterial blood pressure (IBP) with direct arterial measurements in anesthetized and awake red-tailed hawks. Study designProspective, randomized, blinded study. AnimalsSix, sex unknown, adult red-tailed hawks. MethodsBirds were anesthetized and IBP measurements were obtained by oscillometry (IBP-O) and Doppler (IBP-D) on the pectoral and pelvic limbs using three cuffs of different width based on limb circumference: cuff 1 (20–30% of circumference), cuff 2 (30–40%), and cuff 3 (40–50%). Direct arterial pressure measurements were obtained from the contralateral superficial ulnar artery. Indirect blood pressure measurements were compared to direct systolic arterial pressure (SAP) and mean arterial pressure (MAP) during normotension and induced states of hypotension and hypertension. Measurements were also obtained in awake, restrained birds. Three-way anova, linear regression and Bland–Altman analyses were used to evaluate the IBP-D data. Results are reported as mean bias (95% confidence intervals). ResultsThe IBP-O monitor reported errors during 54% of the measurements. Indirect blood pressure Doppler measurements were most accurate with cuff 3 and were comparable to MAP with a bias of 2 (−9, 13 mmHg). However, this cuff consistently underestimated SAP with a bias of 33 (19, 48 mmHg). Variability in the readings within and among birds was high. There was no significant difference between sites of cuff placement. Awake birds had SAP, MAP and diastolic arterial pressure that were 56, 43, and 38 mmHg higher than anesthetized birds. Conclusions and clinical relevanceIndirect blood pressure (oscillometric) measurements were unreliable in red-tailed hawks. Indirect blood pressure (Doppler) measurements were closer to MAP measurements than SAP measurements. There was slightly better agreement with the use of cuff 3 on either the pectoral or pelvic limbs. Awake, restrained birds have significantly higher arterial pressures than those under sevoflurane anesthesia.

Accuracy of an oscillometric blood pressure monitor during phenylephrine-induced hypertension in dogs

To examine the agreement between direct arterial blood pressure measurements obtained from 2 arteries and indirect blood pressure measurements obtained with an oscillometric blood pressure monitor (OBPM) during normotension and phenylephrine-induced hypertension in dogs. 16 male Beagles. In anesthetized dogs, arterial catheters were placed in the lingual and dorsal pedal arteries for measurement of arterial blood pressure. A blood pressure cuff was placed on either the dog's fore- or hind limb and connected to an OBPM. Systolic, diastolic, and mean arterial blood pressures (SAP, DAP, and MAP, respectively) were recorded from both arteries and the OBPM every 5 minutes for 30 minutes (baseline), during a 30-minute period in which dogs received a phenylephrine infusion IV to induce hypertension, and for 30 minutes after discontinuation of the infusion. Mean differences in blood pressure values and confidence intervals were calculated to compare the indirect and direct measurement techniques. In dogs, oscillometry underestimated SAP during normotension, and the difference between oscillometric and direct measurements increased during hypertension. Oscillometry underestimated DAP, but the difference between oscillometric and direct measurements decreased during hypertension. There was close agreement among techniques for MAP determinations. Biases between direct measurements and OPBM blood pressure values measured from dogs' forelimbs or hind limbs were not significantly different. In normotensive dogs, oscillometric measurements of MAP and SAP agreed more closely with direct arterial pressure measurements than oscillometric estimates of DAP. Oscillometric measurement of MAP was accurate during both normotension and hypertension in dogs.

Histophysiological effects of fluid resuscitation on heart, lung and brain tissues in rats with hypovolemia

The efficacy of using colloids and crystalloids in the treatment of hypovolemia still remains controversial. An important aspect in treating hypovolemia is to re-establish normal tissue hemodynamics after fluid resuscitation. Production of nitric oxide (NO) or growth factors such as transforming growth factor beta (TGF-beta) has been identified as a key mechanism in physiological and pathological processes in the different systems. This study was designed to investigate the histophysiological effects of resuscitation with different plasma substitutes on the heart, lung and brain tissues following acute blood loss in male Sprague-Dawley rats weighing 250-280g (n=30). After anesthesia with sodium pentobarbital, the left femoral vein and artery were cannulated for the administration of volume expanders and for direct measurement of arterial pressure and heart rate. Twenty rats were bled (5ml/10min) and infused (5ml/10min) with one of four randomly selected solutions, (a) human albumin, (b) gelatin (Gelofusine), (c) dextran-70 (Macrodex); or (d) physiological saline (0.9% isotonic saline). Five control rats were bled without infusion. Tissue samples were taken and fixed in 10% formalin solution, then processed for embedding in paraffin wax. Sections were cut and stained with hematoxylin and eosin. Indirect immunohistochemical labelling was performed to reveal binding of primary antibodies against endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and TGF-beta. Mild immunoreactivity of eNOS was observed in endothelial cells of vessels in brain, heart and lung tissues. Increased immunoreactivities of eNOS, iNOS and TGF-beta were observed in the non-fluid resuscitated group in these organs; mild, moderate, moderate and strong immunoreactivities were seen in the albumin, gelatin, physiological saline and dextran-70 treated groups, respectively. Immunoreactivities of iNOS and TGF-beta in the non-fluid resuscitated group were increased significantly, in comparison to the other groups, apart from the dextran-70 treated group. The results of this study show that gelatin solution and physiological saline may be of use after acute blood loss, and dextran-70 is not the preferred resuscitation fluid in the early stages of acute blood loss. It was concluded that albumin solution is the preferred fluid for resuscitation.

Determination of Indirect Blood Pressure in the Companion Bird

Abstract The information gathered through arterial blood pressure measurement must be correctly interpreted for appropriate decisions to be made. Systolic blood pressure is the pressure exerted against the blood vessel wall during systole. Although direct arterial pressure measurement is ideal, it is not commonly used because of the need for specific technical skill, invasive nature of the procedure, and cost of equipment. All indirect blood pressure measurement techniques are based on detection of blood flow beneath an inflated cuff. Systolic blood pressure determination via ultrasonic Doppler flow detection (Doppler) has been found to correlate well with direct blood pressure measurements in ducks ( Anas platyrhynchos). Clinical techniques and applications for Doppler blood pressure monitoring will be discussed. Treatment of hypotension involves monitoring blood pressure, removal of the underlying cause, and volume support for hypovolemia. Hypertension has not yet been defined in the psittacine species. The routine use of blood pressure monitoring in the avian species can provide the clinician with a better knowledge base about intravascular volume status to avoid or minimize long-term complications of hypertension.

Intramucosal pH Measurements for Extremely Obese Patients During Laparoscopic Bariatric Surgery

To the Editor: Excessive obesity is defined as a body weight ≥225 % over the ideal weight or body mass index 50 kg · m2(1). As surgical treatment of obesity has developed, interest is renewed in the anesthetic management of these patients (2). Laparoscopic surgical techniques seem beneficial in obese patients (3). The gastric tonometry is a minimally invasive device by which the adequacy of splanchnic blood flow is assessed indirectly (4). We aimed to investigate intramucosal pH (pHi) measurements for excessively obese patients during laparoscopic bariatric surgery. Twelve obese patients with (ASA) class II-III who undergoing laparoscopic gastric banding were included in this study (Table 1). Table 1: The Patients’ Main Characteristics (Number or Mean ± sd)All patients received a low molecular weight heparin and ranitidine 12 h prior to the operation. All anesthetics and other medications were administered according to the corrected weight. Corrected weight was calculated using the following equation. Corrected weight =[0.4 × excess weight] + ideal weight (5). Anesthesia was induced with fentanyl 2 μg · kg−1 and propofol 1 mg · kg−1, a propofol infusion was administered at a rate of 6 mg · kg−1/h−1 until the end of the operation. Atracurium 0.6 mg · kg−1 was given to facilitate orotracheal intubation with a cuffed tube. Throughout the operation, fentanyl 2 μg · kg−1 and atracurium 0.1 mg · kg−1 were given as needed. Controlled ventilation was performed in all patients and ventilator was set to deliver 10 mL · kg−1 tidal volume, 10 min−1 frequency, I:E 1:2, inspiratory pause 20 % of inspiration and a constant inspiratory flow rate. Inspired oxygen content was 50% oxygen-air mixture and fresh gas flow rate was 8 L · min−1. Intra-abdominal pressure was held at 12 mm Hg during laparoscopy and a constant CO2 flow of 2 L · min−1 administered through a laparoscopic insufflator device. After anesthesia induction, arterial catheter was placed into radial artery. Direct arterial pressure measurements and blood gas sampling were performed via arterial catheter. The gastric tonometer (Trip TM, Tonometrics, Helsinki, Finland) was placed into stomach before the surgical incision and its position was verified with fluoroscopy. Mean arterial pressure, heart rate, and pHi values were measured in four periods: after 15 min of anesthesia induction (induction), after 20 min of pneumoperitoneum (pneumoperitoneum), after 10 min of desufflation (desufflation), and after 20 min of extubation (extubation). Atropine 0.01 mg/kg and neostigmine 0.02 mg/kg were administered to antagonize the neuromuscular blockade. At the end of the operation and following emergence from anesthesia, all patients were tracheally extubated and sent to postanesthetic care unit. There is no single anesthetic regimen shown to be superior in obese patients (Table 2). Obesity predisposes to cardiovascular morbidity. Hemodynamic variables could be affected from morbidly obese patients due to many factors (5). In our study, we determined slight changes in mean arterial pressure and heart rate that have no significant statistical result. Table 2: Intramucosal pH and Hemodynamic Values (Mean ± sd)Although there had been many studies evaluating different aspects of physiology during surgery and anesthesia in the obese patients (6–9), our study is the only one that utilized gastric tonometry. There is no clinical evidence or data that report that bariatric surgery operations or gastric band has an effect on stomach or splanchnic circulation. In long-term studies, the gastric band is well tolerated by these patients. Chronic erosion is a common complication due to the gastric band’s local effect, not from stomach nor splanchnic circulation disorder (10). pHi measurements can be used to assess perfusion, and we observed slight decreases in pHi in our patients. There may be many factors responsible for the decrease of splanchnic perfusion from cardiac depression caused by anesthesia to increased intra-abdominal pressure due to pneumoperitoneum. Our study was not designed to evaluate these factors. In conclusion, we found no statistical changes on pHi on the laparoscopic bariatric surgery for excessively obese patients. Ziya Salihoglu, MD Sener Demiroluk, MD Yalim Dikmen, MD Mustafa Taskin, MD

Cardiovascular and renal responses to a high-fat diet in Osborne-Mendel rats.

This study examined the cardiovascular, renal, and hormonal responses of dietary-induced obesity in Osborne-Mendel (OM) rats. Male OM rats were fed either a low (LF; n = 10)- or high-fat (HF; n = 11) diet for 17 wk. During week 15 of the study, arterial pressure was measured directly, 24 h/day, from chronically indwelling catheters. Body and kidney weights were 46 +/- 5 and 33 +/- 5% greater, respectively, in rats fed HF vs. LF diet. Left and right ventricular weights were also greater in rats fed HF diet (21 +/- 7 and 36 +/- 6%, respectively). Direct measurement of arterial pressure revealed only a slight increase in mean arterial pressure (88 +/- 1 in rats fed HF diet vs. 85 +/- 1 mmHg in rats fed LF diet), whereas there was no difference in resting heart rate between the two groups. Consumption of HF diet was also associated with a 3.5-fold increase in plasma insulin, a 16 +/- 4% higher blood glucose, and a 40 +/- 6% reduction in plasma renin activity compared with LF-fed rats. Thus feeding OM rats HF diet led to obesity, cardiac and renal hypertrophy, and hyperinsulinemia but only a slight increase in mean arterial pressure.

Antihypertensive actions of angiotensin-(1-7) in spontaneously hypertensive rats

Observations that angiotensin-(1-7) [ANG-(1-7)] may oppose the vasoconstrictor actions of angiotensin II (ANG II) prompted an investigation of the effects of the heptapeptide on the maintenance of elevated blood pressure in spontaneously hypertensive rats (SHR). ANG-(1-7) (24 micrograms.kg-1.h-1) was infused into the jugular vein of 13-wk-old SHR (n = 64), Wistar-Kyoto (WKY, n = 50), and Sprague-Dawley (SD, n = 18) rats for 2 wk, with the use of osmotic minipumps. Blood pressure, fluid and electrolyte balance, plasma vasopressin, and urinary excretion of prostaglandin E2 and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) were measured at days 2, 7, and 12 of the infusion. In SHR, ANG-(1-7) caused a sustained and significant reduction in plasma vasopressin concentration that was associated with an increase in urinary prostaglandin E2 and 6-keto-PGF1 alpha excretion at day 2 after the commencement of the infusion. These changes were accompanied by diuresis and natriuresis during the first 3 days of infusion in SHR but not in WKY or SD rats. Direct measurements of arterial pressure confirmed the lowering effect of ANG-(1-7) on systolic pressure of SHR on day 2 of treatment with a restoration of the pressure by days 7 and 12. These findings, along with our previous demonstration that ANG-(1-7) is an active depressor peptide in the intact animal, suggest that ANG-(1-7) may play a significant role as a vasodepressor system opposing the hemodynamic actions of ANG II in this genetic form of experimental hypertension.

Transfer of the critically ill obstetric patient: Experience of a specialist team and guidelines for the non-specialist

Transfer of the critically ill obstetric patient between hospitals is increasingly common. The specialist transfer team based at the Western Infirmary Intensive Therapy Unit, Glasgow has transported 60 such patients in the years 1985-1994. Monitoring was by direct arterial pressure measurement in 56 patients and central venous pressure measurement in 45. Forty-one patients were mechanically ventilated in transit. There were no deaths in transit but 3 patients died later in intensive care. The majority of patients had pregnancy induced hypertension or had suffered a post partum haemorrhage. A clinical impression that these two groups had different treatment requirements and outcomes was not substantiated. We conclude that the transfer of even the sickest obstetric patient is feasible and safe and suggest guidelines to non-specialists for the management of these patients before and during interhospital transfer.