authors gratefully acknowledge funding support from the Molly Towell Perinatal Research Foundation, Canadian Institutes of Health Research (CIHR), and Fonds de Recherche du Qu&#233;bec &#8211; Sant&#233; (FRQS) (to MGF) and CIHR-Quebec Training Network in Perinatal Research (QTNPR) (to LDD).
The authors wish to thank Esther Simard, Marco Bosa, Carl Bernard and Carmen Movila for technical assistance.

Animal care followed the guidelines of the Canadian Council on Animal Care and the approval by the Universit&#233; de Montr&#233;al Council on Animal Care (protocol #10-Rech-1560). Detailed information on materials and methods used is provided in the Table 1.
1. Anesthesia
<ol>
	<li>Insert a single-lumen catheter into a jugular vein.</li>
	<li>Sedate the ewe using acepromazine (Atravet 10 mg/mL) 2 mg intravenously approximately 30 min&#160;prior to the induction of anesthesia in order to red...

The anesthetic and surgical procedures are presented that are required for establishing an animal model for studying fetal physiology and pathophysiology: the chronically instrumented non-anesthetized fetal sheep.
Four critical steps within the protocol should be emphasized. First, passing the catheters and electrodes through the maternal flank: it is important that this is done at once to avoid any internal organ injuries. Second, securing the uterotomy operating site prior to exteriorizing t...

A variety of animal models exist for the study of both normal and compromised pregnancies, including laboratory rodents, non-human primates and domestic ruminants.1,2,3,4,5 The chronically instrumented pregnant sheep has been used extensively for 50 years as a model of human fetal development and responses to pathophysiologic stimuli such as lipopolysaccharide (LPS).6-10 The lesions following LPS exposure mimic exactly what is seen in preterm infants with periventricular leukomalacia, which is due to a similar maturational profile of both species.11, 12
Other pregnancy complications have also been studied in great detail such as the discovery that antenatal glucocorticoids promote lung development 13-15 and understanding the impact of intrauterine growth restriction (IUGR) on the fetus 16,17.
The extensive use of the fetal sheep model is due to the unique amenability of the non-anesthetized fetal sheep to the surgical placement and maintenance of catheters and electrodes, allowing repetitive blood sampling, recording of bioelectrical activity, application of electric stimulation and in vivo brain imaging.18 Telemetry is also possible, although less frequently used yet due to the higher sophistication to set up as well as the initial and maintenance cost.19
Moreover, the fetal sheep model is very versatile as many variations of instrumentation are possible depending on the measures of interest. For example, it is possible to record over days to weeks multivariate signals in real time such as fetal breathing movements, electrical brain activity, cardiovascular responses, electrocardiogram, regional blood flow to a range of organs using flow probes or microspheres, etc. Thanks to this versatility, a wide range of studies have been conducted including the development of the cardiovascular system20,21, hypothalamo-pituitary-adrenal (HPA) axis22, brain development23 and sleep states development in particular24, effects of hypoxia/asphyxia25, therapeutic hypothermia 26, inflammation6-11, combination of both27, glucocorticoids28,29, anti-depressants30, broncho-pulmonary dysplasia (BPD) 31,32, fetal programming33,34,35,36,37,38,39 or development of novel fetal monitoring modalities prior and during labor to name but a few areas of investigation. 40,41,42,43
The overall goal of the method presented is to show this versatile model&#8217;s basic implementation. It allows establishing a wide variety of acute and chronic experimental protocols studying fetal physiology and pathophysiology on the integrative, organ, cellular and molecular levels.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>ACE Light source</td>
			<td>Schott-Fostec</td>
			<td>A20500</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting scissors</td>
			<td>Fine Science Tools</td>
			<td>14060 - 11</td>
			<td></td>
		</tr>
		<tr>
			<td>Angled dissecting scissors</td>
			<td>Fine Science Tools</td>
			<td>15006 - 09</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel handle</td>
			<td>Fine Science Tools</td>
			<td>10003 - 12</td>
			<td>alternating dissecting tool</td>
		</tr>
		<tr>
			<td>Curved scalpel blades #12</td>
			<td>Fine Science Tools</td>
			<td>10012 - 00</td>
			<td>alternating dissecting tool</td>
		</tr>
		<tr>
			<td>Bone scissors</td>
			<td>Fine Science Tools</td>
			<td>16044 - 10</td>
			<td></td>
		</tr>
		<tr>
			<td>S &#38; T suture tying forceps</td>
			<td>Fine Science Tools</td>
			<td>00272 - 13</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont SS forceps - angled</td>
			<td>Fine Science Tools</td>
			<td>11203 - 25&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Braided silk suture size 6-0</td>
			<td>Teleflex Medical</td>
			<td>07 - 30&#160; - 10</td>
			<td></td>
		</tr>
		<tr>
			<td>Medical Tape</td>
			<td>transpore</td>
			<td>3M</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine hydrochloride 100 mg/ml</td>
			<td>Hospira</td>
			<td>NDC 0409 - 2051 - 05</td>
			<td>Final Does is 80 mg/kg</td>
		</tr>
		<tr>
			<td>Tranqui Ved Injection (xylazine 100 mg/ml)</td>
			<td>Vecdo</td>
			<td>NDC 50989 - 234 - 11</td>
			<td>Final Does is 10 mg/kg</td>
		</tr>
		<tr>
			<td>Reactive orange 14</td>
			<td>Sigma - Aldrich</td>
			<td>R - 8254</td>
			<td></td>
		</tr>
		<tr>
			<td>Ringers Solution Components</td>
			<td></td>
			<td></td>
			<td>Solution is gas equilibrated with 95% O2 and 5% Co2, final pH 7.4</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma - Aldrich</td>
			<td>S7653</td>
			<td>Final Concentration: 118 mM</td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Fisher Scientific</td>
			<td>P217 - 3</td>
			<td>Final Concentration: 4.7 mM</td>
		</tr>
		<tr>
			<td>Calcium chloride dihydrate</td>
			<td>Fisher Scientific</td>
			<td>C79 - 500</td>
			<td>Final Concentration: 2.5 mM</td>
		</tr>
		<tr>
			<td>Potassium phosphate monobasic</td>
			<td>Fisher Scientific</td>
			<td>P -285</td>
			<td>Final Concentration: 1.2 mM</td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>J.T. Baker</td>
			<td>Jan-00</td>
			<td>Final Concentration: 0.57 mM</td>
		</tr>
		<tr>
			<td>4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES)</td>
			<td>Fisher Scientific</td>
			<td>BP 310 - 500</td>
			<td>Final Concentration: 5.95 g/L</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma - Aldrich</td>
			<td>G8270</td>
			<td>Final Concentration: 5.5 mM</td>
		</tr>
		<tr>
			<td>LifeWindow</td>
			<td>Digicare Biomedical Technology</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CED bioamplifier and ADC units</td>
			<td>Cambridge Electronic Design Limited, 
			Unit 4, Science Park, 
			Milton Road, 
			Cambridge CB4 0FE 
			ENGLAND.</td>
			<td>Bioamp: 1902; ADC: micro1401; Data acquisition software: Spike 2, V7.13</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurolog analog signal bioamplifier</td>
			<td>Digitimer Ltd 
			37 Hydeway 
			Welwyn Garden City 
			Hertfordshire, AL7 3BE, England</td>
			<td>NL108A</td>
			<td></td>
		</tr>
		<tr>
			<td>ABL800Flex</td>
			<td>Radiometer Canada; 200 Aberdeen Dr, London, ON N5V 4N2</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf 5804R</td>
			<td>Eppendorf Canada; 2810 Argentia Road, #2 
			Mississauga, Ontario, L5N 8L2</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Arrow Jugular Catheterization Set</td>
			<td>Arrow International, Inc., 2400 Bernville Road, Reading, PA 19605 USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Atravet</td>
			<td></td>
			<td></td>
			<td>10 mg/mL</td>
		</tr>
		<tr>
			<td>Diazepam</td>
			<td></td>
			<td></td>
			<td>5mg/mL</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>Ketalar</td>
			<td></td>
			<td>100 mg/mL</td>
		</tr>
		<tr>
			<td>Propofol</td>
			<td></td>
			<td></td>
			<td>10 mg/mL</td>
		</tr>
		<tr>
			<td>SurgiVeT</td>
			<td>Endotracheal Tubes; Smiths Medical ASD, Inc. St. Paul, MN 55112, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cook Airway Exchange Catheter with RAPI-FIT Adapters</td>
			<td>Cook Critical Care 750, Bloomington IN 47402-0489 USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dispomed Ventilator</td>
			<td>Dispomed Ltd., 745 Nazaire-Laurin, Joliette, Quebec J6E 0L6</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BD Insyte-W</td>
			<td>Becton Dickinson, Infusion Therapy Systems Inc., 9450 S State St, Sandy Utah 84070 USA</td>
			<td></td>
			<td>22 to 20 G; 1 in [0.9 x 25 mm] to 1.16 in [1.1 x 30 mm]</td>
		</tr>
		<tr>
			<td>Edwards Lifesciences Ref: PX272 Pressure monitoring kit with TruWave Disposable Pressure</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LifeWindow LW6000</td>
			<td>Digicare Biomedical Technology 107 Commerce Road, Boynton Beach, FL 33426-9365 USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gaymar</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Babcock</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Polyvinyl catheters</td>
			<td>SCI (Scientific Commodities Inc.)</td>
			<td></td>
			<td>2 meters</td>
		</tr>
		<tr>
			<td>2-0 Vicryl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Castroviejo scissors</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>electrocardiogram (ECG)</td>
			<td>LIFYY, Metrofunk Kabel-Union, Berlin, Germany</td>
			<td></td>
			<td>four copper electrodes in single sheath, 2 meters</td>
		</tr>
		<tr>
			<td>2-O Vicryl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>3-0 Vicryl</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PDS II USP</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Trimethoprim sulfadoxine</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ampicillin</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stopcock</td>
			<td>Argon Medical, Cat&#160;041220001A</td>
			<td></td>
			<td>Double 4-way Stopcock with male luer lock</td>
		</tr>
		<tr>
			<td>Needles</td>
			<td>Tyco Healthcare 8881202389</td>
			<td></td>
			<td>Monoject aluminum hub blunt needles, 22Gx, 0.7mmx 38.1mm: for fetal arterial and venous catheters</td>
		</tr>
		<tr>
			<td>Needles</td>
			<td>Tyco Healthcare 8881202322</td>
			<td></td>
			<td>Monoject aluminum hub blunt needles, 16Gx, 1.6mmx38.1mm: for amniotic catheters</td>
		</tr>
	</tbody>
</table>

instrumentation of near-term fetal sheep for multivariate chronic non-anesthetized recordings

The chronically instrumented pregnant sheep has been used as a model of human fetal development and responses to pathophysiologic stimuli such as endotoxins, bacteria, umbilical cord occlusions, hypoxia and various pharmacological treatments. The life-saving clinical practices of glucocorticoid treatment in fetuses at risk of premature birth and the therapeutic hypothermia have been developed in this model. This is due to the unique amenability of the non-anesthetized fetal sheep to the surgical placement and maintenance of catheters and electrodes, allowing repetitive blood sampling, substance injection, recording of bioelectrical activity, application of electric stimulation and in vivo organ imaging. Here we describe the surgical instrumentation procedure required to achieve a stable chronically instrumented non-anesthetized fetal sheep model including characterization of the post-operative recovery from blood gas, metabolic and inflammation standpoints.

38 pregnant time-dated ewes were instrumented at 128&#177;2 days of gestation (dGA, ~0.88 gestation, term 145 dGA) with arterial, venous and amniotic catheters and electrocardiogram (ECG) electrodes with sterile technique under general anesthesia (both ewe and fetus). In case of twin pregnancy the larger fetus was chosen based on palpating and estimating the intertemporal diameter; alternatively, the fetus to be instrumented may be selected randomly to avoid any potential bias or both fetuses may be instrumented. The tot...

Watch this Scientific Journal Video about Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings at JoVE.com

Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings

The chronically instrumented non-anesthetized fetal sheep model is used to study human fetal development in health and disease, because it permits surgical placement and maintenance of catheters and electrodes, repetitive blood sampling, substance injection, recording of bioelectrical activity, and in vivo imaging. We describe the procedures required to establish this model.

The chronically instrumented pregnant sheep has been used as a model of human fetal development and responses to pathophysiologic stimuli such as ...

instrumentation-near-term-fetal-sheep-for-multivariate-chronic-non

Research

JoVE Journal

Developmental Biology

9.3K visualizações.  CHUV, Université de Montréal, St-Hyacinthe, QC.  O modelo de fetos de ovelhas não-anestesiado cronicamente instrumentados é usado para estudar o desenvolvimento fetal humano na saúde e na doença, pois permite a colocação cirúrgica e manutenção de cateteres e eletrodos, coleta de sangue repetitivo, injeção de substância, a gravação da atividade bioelétrica, e in vivo de imagens. Nós descrevemos os procedimentos necessários para estabelecer este modelo. 