The aim of this study is to evaluate the efficacy of internal jugular cross sectional area for predicting the occurrence of PSAH.

The aim of this study is to evaluate the efficacy of internal jugular cross sectional area for predicting the occurrence of PSAH. Spinal anaesthesia is frequently used in daily clinical practice. Postspinal anaesthesia hypotension (PSAH) is a common side effect with an incidence of 15.3 to 33% that may result in organ hypoperfusion and ischaemic events. Patients' susceptibility to intraoperative hypotension can be influenced by the sensory block level, age, preoperative volume status , physical status, pre-operative medications and fasting.

PSAH due to spinal blockade is principally a consequence of diminished systemic vascular resistance after blockade of preganglionic sympathetic fibres. Many attempts have been tried to prevent PSAH, such as intravenous volume preload or prophylactic vasopressors. However, fluid infusion has been proved to lower the incidence of PSAH and significantly decrease vasopressor requirements. At the same time, empirical volume loading carries the potential of volume overload, particularly in patients with cardiac disease. Consequently, the search for predictors of PSAH is becoming mandatory to avoid blind volume loading and reserve it only for patients who are expected to develop PSAH. .

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Inclusion Criteria:

• patients more than 40 years of age.
• American Society of Anesthesiologists' (ASA) physical status 1 or 2.
• scheduled for elective surgery under spinal anaesthesia in the supine position.

Exclusion Criteria:

• BMI more than 35 kg m2.
• taking angiotensin converting enzyme inhibitors.
• pregnant women.
• emergency cases.
• absolute or relative contraindications to spinal anaesthesia.
• Also, patients with a baseline arterial systolic blood pressure less than 90 mmHg or mean arterial blood pressure (MBP) less than 70 mmHg will be excluded.

patients more than 40 years of age with American Society of Anesthesiologists' (ASA) physical status 1 or 2 who will be scheduled for elective orthopedic surgery under spinal anaesthesia in the supine position