Increase in heart rate (HR) is a normal sympathetic response to body trauma and a common consequence of major surgical procedures,A high resting HR is associated with increased myocardial work that may be detrimental to patients with a marginal myocardial oxygen supply,the aim of this study is To compare between the effects of Acu TENS and low level laser therapy on autonomic and hemodynamic instability after open heart surgery.

Autonomic function reached lowest values 3-6 days after coronary artery by pass graft (CABG) and could take up to 60 days to return to pre-surgery values (pedro et al., 2005).

Alterations in pulse may provide a first indication that a patient is developing hemodynamic instability. While many factors may influence the pulse rate, including fever, exercise, medications, and thyroid hormone status, a high pulse rate is often a sign of high levels of endogenous catecholamines, blood loss or dehydration (Jonathan ,2009.) Hemodynamically unstable patients don't have enough pressure in the circulatory system to keep blood flowing reliably to all the various parts of the body where it needs to be at the same time.

Vagus nerve stimulation (VNS) can increase HRV and reduce sympathetic nerve outflow, which is desirable in conditions characterized by enhanced sympathetic nerve activity .

Application of Acu-TENS over acu-point PC6 facilitated a faster return of resting HR to preoperative levels, maintained BP during the acute postoperative period and enhanced a quicker return of rate pressure product (RPP), in patients after acute cardiac surgery .

Faster return of the raised resting HR to preoperative levels in Acu-TENS application was possibly due to induced vagal stimulation and/or inhibition of sympathetic neural activity through the acu-points PC6 .

Low level laser therapy (LLLT) is a non-invasive and safe method, to recover parasympathetic/sympathetic nervous system balance .

this study show the differences between the effect of Acu TENS and low level laser therapy on autonomic and hemodynamic instability after open heart surgery

Inclusion Criteria:

• 1- 60 patients from both sexes . 2- undergo cardiac surgery through a median sternotomy. 3- age will be ranged from 45-65 years old. 4-Body mass index from 25 to 29.9 kg/m25-

Exclusion Criteria:

• 1- Previous thoracic surgery. 2- Emergency or urgent cardiac surgery. 3- hypoxemia with partial pressure of oxygen in arterial blood <60 mmHg. 4- Renal insufficiency with serum creatinine ≤1.8 mg/dl after surgery. 5- Other medical conditions such as uncontrolled diabetes, and hypertension . 6- Patients who are unable to follow verbal instructions.